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lib/lz4: import upstream LZ4 sources verbatim

RFC PATCH Superseded Michal Wilczynski 5 participants 34 messages Sep 25 – Oct 4 1 message not in the archive

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#1 lore raw

cover lib/lz4: stop forking upstream LZ4, vendor it instead

The in-kernel LZ4 is a fork. The decompressor was last synced with upstream v1.8.3 in 2018 and the compressor with v1.7.3 in 2017, both by hand. Upstream has made 488 commits against lib/ since, and the gap is maintained one cherry-pick at a time.

That has left real bugs in place for example the forked LZ4_decompress_fast() has no bounds checks, so corrupted input runs off the output buffer in both directions.

This series vendors the upstream sources unmodified and adapts them at build time, so a re-sync becomes a directory copy:

upstream/lz4.c, upstream/lz4.h verbatim upstream sources
upstream/lz4hc.c, upstream/lz4hc.h

  lz4_deps.h                        the build environment
  lz4_kernel_api.h                  hands the LZ4 names back
  freestanding/                     ISO C headers -nostdinc drops
  lz4_compress.c                    the kernel's entry points

lz4_decompress.c
lz4hc_compress.c

Patch 1 imports the sources. Patch 2 backports the one upstream fix the kernel's warning flags require. Patch 3 adds the build environment. Patch 4 puts the freestanding headers on the pre-boot decompressor path. Patches 5-7 convert the compressor, HC compressor and decompressor in turn. Patch 8 folds away the last duplicated prototype list. Patch 9 gives lib/lz4 a MAINTAINERS entry, which it has never had.

The exported API changes in three ways.

The three stream types become incomplete. <linux/lz4.h> spelled out their layout for the fork's benefit, upstream headers define the same types and lib/decompress_unlz4.c ends up with both in one translation unit. Callers allocate LZ4_MEM_COMPRESS, LZ4HC_MEM_COMPRESS or LZ4_MEM_DECOMPRESS bytes instead of sizeof() every caller but zram already did. Each conversion patch makes its own type incomplete so no step leaves the tree broken.

Sixteen macros go with them: the hash geometry (LZ4_HASHLOG, LZ4_HASHTABLESIZE, LZ4_HASH_SIZE_U32, LZ4HC_DICTIONARY_LOGSIZE, LZ4HC_MAXD, LZ4HC_MAXD_MASK, LZ4HC_HASH_LOG, LZ4HC_HASHTABLESIZE, LZ4HC_HASH_MASK) and the sizes derived from it (LZ4_MEMORY_USAGE, LZ4_STREAMSIZE{,_U64}, LZ4_STREAMHCSIZE{,_SIZET}, LZ4_STREAMDECODESIZE{,_U64}). They existed to lay out structures the fork defined here none has an in tree user outside lib/lz4. LZ4_compressBound() goes too a static inline whose only caller was lib/decompress_unlz4.c, now using the LZ4_COMPRESSBOUND() macro.

LZ4_MEM_DECOMPRESS and LZ4HC_CLAMP_CLEVEL are new.

There are some behaviour changes. All of them come from upstream rather than from this series and I have kept them rather than patching them
out: a local fix on top of vendored sources is exactly the divergence this series exists to remove.

- LZ4HC levels 10 and up are clamped to 9. Upstream routes them to its optimal parser, whose ~64K opt[] does not fit a kernel stack. The fork had no optimal parser at all - level only scaled search depth - so its levels 10-16 beat its own level 9 by 0.01%. Clamping rather than rejecting keeps existing f2fs and zram settings working.

- LZ4_decompress_fast() stops running off the output buffer. Upstream routes it through LZ4_decompress_unsafe_generic(), which bounds-checks.

- LZ4_decompress_safe_partial() with a zero-length target returns 0 rather than -1, matching upstream since 725cb0aafdf7. No in-tree caller passes zero.

- The compressors require wrkmem aligned to 8 bytes. Upstream checks this and LZ4_initStream() returns NULL, which the stateless entry points cannot report, so a misaligned buffer faults rather than failing cleanly. Every in-tree caller uses kmalloc() or vmalloc() and is already aligned; <linux/lz4.h> now documents the requirement. Turning upstream's LZ4_ALIGN_TEST off would trade a loud failure for a silent one.

The layout follows lib/zstd, which keeps upstream's sources in a subdirectory and the kernel glue on top. zstd has an upstream import tool and an upstream zstd_deps.h; LZ4 has neither, so the kernel glue here lives outside the vendored files.

The import is the v1.10.0 release tag. It does not build under -Wmissing-prototypes without upstream commit 5ef1f16929b5, which patch 2 backports; that is the only deviation from the tag. The decoder fixes in PR #1753 landed after v1.10.0 and do not backport cleanly; they will come with the next release.

checkpatch reports some 3500 errors against patch 1: upstream's coding style, and no SPDX tags, in files kept verbatim.

Measured in the kernel: three kernels differing only in lib/lz4, booted one core under KVM, each reading 1.3GB of kernel source from an LZ4 erofs image with the page cache dropped before every pass. Median of 21 passes. The middle column is upstream v1.10.0 with LZ4_FAST_DEC_LOOP=0, to separate the version bump from the decode loop upstream added in v1.9.0.

erofs read, MB/s
erofs cluster today v1.10.0 + fast loop net

             4K     2363      2404          2630   +11%
            64K     2788      2904          3168   +14%

The same three decoders at the library level, each block decompressed on its own the way zram treats a page. x86_64, the fork's and upstream's sources built with the kernel's code generation flags (so no SSE), all decoding the same compressed input, median of 21 interleaved runs. The first corpus is upstream's tests/datagen with a fixed seed, so it is byte-identical anywhere; the second is a tar of kernel sources:

decompression, MB/s

  corpus           block  ratio    today   v1.10.0  + fast loop   net
  datagen -s0 -P60   4K  1.09x     4588      4702         5086   +11%
                    16K  1.34x     3950      4016         4779   +21%
                    64K  1.90x     4761      4866         5588   +17%
                   256K  1.92x     6596      6714         7258   +10%
  kernel source tar  4K  2.29x     3694      3830         4190   +13%
                    16K  2.57x     3653      3842         4091   +12%
                    64K  2.80x     3655      3818         4039   +11%
                   256K  2.95x     4072      4231         4542   +12%

The cost is size: lib/lz4 grows from 45K to 89K of text on x86_64, lz4hc most (12K to 39K). That is upstream code the fork never had, and the optimal parser the level clamp leaves unreachable is only 6K of it.

---
Michal Wilczynski (9):
lib/lz4: import upstream LZ4 sources verbatim
lib/lz4: backport upstream's -Wmissing-prototypes fix lib/lz4: add the build environment for the vendored sources
arch: boot: put the LZ4 freestanding headers on the decompressor path lib/lz4: switch the compressor to the vendored sources lib/lz4: switch the HC compressor to the vendored sources lib/lz4: switch the decompressor to the vendored sources lib/lz4: fold lz4_kernel_api.h into <linux/lz4.h>
MAINTAINERS: add an entry for the LZ4 compression library

 MAINTAINERS                          |    6 +
 arch/arm/boot/compressed/Makefile    |    3 +
 arch/mips/boot/compressed/Makefile   |    4 +
 arch/parisc/boot/compressed/Makefile |    3 +
 arch/s390/boot/Makefile              |    3 +
 arch/x86/boot/compressed/Makefile    |    3 +
 drivers/block/zram/backend_lz4.c     |    8 +-
 drivers/block/zram/backend_lz4hc.c   |    4 +-
 include/linux/lz4.h                  |  151 +-
 lib/decompress_unlz4.c               |    4 +-
 lib/lz4/Makefile                     |   15 +-
 lib/lz4/freestanding/limits.h        |   14 +
 lib/lz4/freestanding/stddef.h        |   15 +
 lib/lz4/freestanding/stdint.h        |   14 +
 lib/lz4/freestanding/string.h        |   14 +
 lib/lz4/lz4_compress.c               |  941 +----------
 lib/lz4/lz4_decompress.c             |  718 +--------
 lib/lz4/lz4_deps.h                   |   96 ++
 lib/lz4/lz4_kernel_api.h             |   35 +
 lib/lz4/lz4defs.h                    |  247 ---
 lib/lz4/lz4hc_compress.c             |  785 +---------
 lib/lz4/upstream/lz4.c               | 2829 ++++++++++++++++++++++++++++++++++
 lib/lz4/upstream/lz4.h               |  884 +++++++++++
 lib/lz4/upstream/lz4hc.c             | 2192 ++++++++++++++++++++++++++
 lib/lz4/upstream/lz4hc.h             |  414 +++++
 25 files changed, 6748 insertions(+), 2654 deletions(-)

---
base-commit: 93f51579e7df248780214094418f205253383cc5
change-id: 20260904-lz4-vendor-upstream-4bc2202d0ffc

Best regards,

Signature · 1 line
Michal Wilczynski <[email protected]>
#2 lore raw

RFC PATCH 1/9 lib/lz4: import upstream LZ4 sources verbatim

Add the four upstream files under lib/lz4/upstream/ without modification. Nothing builds them yet; a later patch adds the build environment.

Copied without modification from the v1.10.0 release tag of
https://github.com/lz4/lz4, tagged 2024-07-21.

---
 lib/lz4/upstream/lz4.c   | 2829 ++++++++++++++++++++++++++++++++++++++++++++++
 lib/lz4/upstream/lz4.h   |  884 +++++++++++++++
 lib/lz4/upstream/lz4hc.c | 2192 +++++++++++++++++++++++++++++++++++
 lib/lz4/upstream/lz4hc.h |  414 +++++++
 4 files changed, 6319 insertions(+)
lib/lz4/upstream/lz4.c new file +2829 -0
new file mode 100644
index 0000000000000000000000000000000000000000..a2f7abee19fb9a5c768f2a6c266acf5b571f0855
@@ -0,0 +1,2829 @@
+/*
+   LZ4 - Fast LZ compression algorithm
+   Copyright (C) 2011-2023, Yann Collet.
+
+   BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions are
+   met:
+
+       * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+       * Redistributions in binary form must reproduce the above
+   copyright notice, this list of conditions and the following disclaimer
+   in the documentation and/or other materials provided with the
+   distribution.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+   You can contact the author at :
+    - LZ4 homepage : http://www.lz4.org
+    - LZ4 source repository : https://github.com/lz4/lz4
+*/
+
+/*-************************************
+*  Tuning parameters
+**************************************/
+/*
+ * LZ4_HEAPMODE :
+ * Select how stateless compression functions like `LZ4_compress_default()`
+ * allocate memory for their hash table,
+ * in memory stack (0:default, fastest), or in memory heap (1:requires malloc()).
+ */
+#ifndef LZ4_HEAPMODE
+#  define LZ4_HEAPMODE 0
+#endif
+
+/*
+ * LZ4_ACCELERATION_DEFAULT :
+ * Select "acceleration" for LZ4_compress_fast() when parameter value <= 0
+ */
+#define LZ4_ACCELERATION_DEFAULT 1
+/*
+ * LZ4_ACCELERATION_MAX :
+ * Any "acceleration" value higher than this threshold
+ * get treated as LZ4_ACCELERATION_MAX instead (fix #876)
+ */
+#define LZ4_ACCELERATION_MAX 65537
+
+
+/*-************************************
+*  CPU Feature Detection
+**************************************/
+/* LZ4_FORCE_MEMORY_ACCESS
+ * By default, access to unaligned memory is controlled by `memcpy()`, which is safe and portable.
+ * Unfortunately, on some target/compiler combinations, the generated assembly is sub-optimal.
+ * The below switch allow to select different access method for improved performance.
+ * Method 0 (default) : use `memcpy()`. Safe and portable.
+ * Method 1 : `__packed` statement. It depends on compiler extension (ie, not portable).
+ *            This method is safe if your compiler supports it, and *generally* as fast or faster than `memcpy`.
+ * Method 2 : direct access. This method is portable but violate C standard.
+ *            It can generate buggy code on targets which assembly generation depends on alignment.
+ *            But in some circumstances, it's the only known way to get the most performance (ie GCC + ARMv6)
+ * See https://fastcompression.blogspot.fr/2015/08/accessing-unaligned-memory.html for details.
+ * Prefer these methods in priority order (0 > 1 > 2)
+ */
+#ifndef LZ4_FORCE_MEMORY_ACCESS   /* can be defined externally */
+#  if defined(__GNUC__) && \
+  ( defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || defined(__ARM_ARCH_6K__) \
+  || defined(__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__) || defined(__ARM_ARCH_6T2__) )
+#    define LZ4_FORCE_MEMORY_ACCESS 2
+#  elif (defined(__INTEL_COMPILER) && !defined(_WIN32)) || defined(__GNUC__) || defined(_MSC_VER)
+#    define LZ4_FORCE_MEMORY_ACCESS 1
+#  endif
+#endif
+
+/*
+ * LZ4_FORCE_SW_BITCOUNT
+ * Define this parameter if your target system or compiler does not support hardware bit count
+ */
+#if defined(_MSC_VER) && defined(_WIN32_WCE)   /* Visual Studio for WinCE doesn't support Hardware bit count */
+#  undef  LZ4_FORCE_SW_BITCOUNT  /* avoid double def */
+#  define LZ4_FORCE_SW_BITCOUNT
+#endif
+
+
+
+/*-************************************
+*  Dependency
+**************************************/
+/*
+ * LZ4_SRC_INCLUDED:
+ * Amalgamation flag, whether lz4.c is included
+ */
+#ifndef LZ4_SRC_INCLUDED
+#  define LZ4_SRC_INCLUDED 1
+#endif
+
+#ifndef LZ4_DISABLE_DEPRECATE_WARNINGS
+#  define LZ4_DISABLE_DEPRECATE_WARNINGS /* due to LZ4_decompress_safe_withPrefix64k */
+#endif
+
+#ifndef LZ4_STATIC_LINKING_ONLY
+#  define LZ4_STATIC_LINKING_ONLY
+#endif
+#include "lz4.h"
+/* see also "memory routines" below */
+
+
+/*-************************************
+*  Compiler Options
+**************************************/
+#if defined(_MSC_VER) && (_MSC_VER >= 1400)  /* Visual Studio 2005+ */
+#  include <intrin.h>               /* only present in VS2005+ */
+#  pragma warning(disable : 4127)   /* disable: C4127: conditional expression is constant */
+#  pragma warning(disable : 6237)   /* disable: C6237: conditional expression is always 0 */
+#  pragma warning(disable : 6239)   /* disable: C6239: (<non-zero constant> && <expression>) always evaluates to the result of <expression> */
+#  pragma warning(disable : 6240)   /* disable: C6240: (<expression> && <non-zero constant>) always evaluates to the result of <expression> */
+#  pragma warning(disable : 6326)   /* disable: C6326: Potential comparison of a constant with another constant */
+#endif  /* _MSC_VER */
+
+#ifndef LZ4_FORCE_INLINE
+#  if defined (_MSC_VER) && !defined (__clang__)    /* MSVC */
+#    define LZ4_FORCE_INLINE static __forceinline
+#  else
+#    if defined (__cplusplus) || defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L   /* C99 */
+#      if defined (__GNUC__) || defined (__clang__)
+#        define LZ4_FORCE_INLINE static inline __attribute__((always_inline))
+#      else
+#        define LZ4_FORCE_INLINE static inline
+#      endif
+#    else
+#      define LZ4_FORCE_INLINE static
+#    endif /* __STDC_VERSION__ */
+#  endif  /* _MSC_VER */
+#endif /* LZ4_FORCE_INLINE */
+
+/* LZ4_FORCE_O2 and LZ4_FORCE_INLINE
+ * gcc on ppc64le generates an unrolled SIMDized loop for LZ4_wildCopy8,
+ * together with a simple 8-byte copy loop as a fall-back path.
+ * However, this optimization hurts the decompression speed by >30%,
+ * because the execution does not go to the optimized loop
+ * for typical compressible data, and all of the preamble checks
+ * before going to the fall-back path become useless overhead.
+ * This optimization happens only with the -O3 flag, and -O2 generates
+ * a simple 8-byte copy loop.
+ * With gcc on ppc64le, all of the LZ4_decompress_* and LZ4_wildCopy8
+ * functions are annotated with __attribute__((optimize("O2"))),
+ * and also LZ4_wildCopy8 is forcibly inlined, so that the O2 attribute
+ * of LZ4_wildCopy8 does not affect the compression speed.
+ */
+#if defined(__PPC64__) && defined(__LITTLE_ENDIAN__) && defined(__GNUC__) && !defined(__clang__)
+#  define LZ4_FORCE_O2  __attribute__((optimize("O2")))
+#  undef LZ4_FORCE_INLINE
+#  define LZ4_FORCE_INLINE  static __inline __attribute__((optimize("O2"),always_inline))
+#else
+#  define LZ4_FORCE_O2
+#endif
+
+#if (defined(__GNUC__) && (__GNUC__ >= 3)) || (defined(__INTEL_COMPILER) && (__INTEL_COMPILER >= 800)) || defined(__clang__)
+#  define expect(expr,value)    (__builtin_expect ((expr),(value)) )
+#else
+#  define expect(expr,value)    (expr)
+#endif
+
+#ifndef likely
+#define likely(expr)     expect((expr) != 0, 1)
+#endif
+#ifndef unlikely
+#define unlikely(expr)   expect((expr) != 0, 0)
+#endif
+
+/* Should the alignment test prove unreliable, for some reason,
+ * it can be disabled by setting LZ4_ALIGN_TEST to 0 */
+#ifndef LZ4_ALIGN_TEST  /* can be externally provided */
+# define LZ4_ALIGN_TEST 1
+#endif
+
+
+/*-************************************
+*  Memory routines
+**************************************/
+
+/*! LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION :
+ *  Disable relatively high-level LZ4/HC functions that use dynamic memory
+ *  allocation functions (malloc(), calloc(), free()).
+ *
+ *  Note that this is a compile-time switch. And since it disables
+ *  public/stable LZ4 v1 API functions, we don't recommend using this
+ *  symbol to generate a library for distribution.
+ *
+ *  The following public functions are removed when this symbol is defined.
+ *  - lz4   : LZ4_createStream, LZ4_freeStream,
+ *            LZ4_createStreamDecode, LZ4_freeStreamDecode, LZ4_create (deprecated)
+ *  - lz4hc : LZ4_createStreamHC, LZ4_freeStreamHC,
+ *            LZ4_createHC (deprecated), LZ4_freeHC  (deprecated)
+ *  - lz4frame, lz4file : All LZ4F_* functions
+ */
+#if defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION)
+#  define ALLOC(s)          lz4_error_memory_allocation_is_disabled
+#  define ALLOC_AND_ZERO(s) lz4_error_memory_allocation_is_disabled
+#  define FREEMEM(p)        lz4_error_memory_allocation_is_disabled
+#elif defined(LZ4_USER_MEMORY_FUNCTIONS)
+/* memory management functions can be customized by user project.
+ * Below functions must exist somewhere in the Project
+ * and be available at link time */
+void* LZ4_malloc(size_t s);
+void* LZ4_calloc(size_t n, size_t s);
+void  LZ4_free(void* p);
+# define ALLOC(s)          LZ4_malloc(s)
+# define ALLOC_AND_ZERO(s) LZ4_calloc(1,s)
+# define FREEMEM(p)        LZ4_free(p)
+#else
+# include <stdlib.h>   /* malloc, calloc, free */
+# define ALLOC(s)          malloc(s)
+# define ALLOC_AND_ZERO(s) calloc(1,s)
+# define FREEMEM(p)        free(p)
+#endif
+
+#if ! LZ4_FREESTANDING
+#  include <string.h>   /* memset, memcpy */
+#endif
+#if !defined(LZ4_memset)
+#  define LZ4_memset(p,v,s) memset((p),(v),(s))
+#endif
+#define MEM_INIT(p,v,s)   LZ4_memset((p),(v),(s))
+
+
+/*-************************************
+*  Common Constants
+**************************************/
+#define MINMATCH 4
+
+#define WILDCOPYLENGTH 8
+#define LASTLITERALS   5   /* see ../doc/lz4_Block_format.md#parsing-restrictions */
+#define MFLIMIT       12   /* see ../doc/lz4_Block_format.md#parsing-restrictions */
+#define MATCH_SAFEGUARD_DISTANCE  ((2*WILDCOPYLENGTH) - MINMATCH)   /* ensure it's possible to write 2 x wildcopyLength without overflowing output buffer */
+#define FASTLOOP_SAFE_DISTANCE 64
+static const int LZ4_minLength = (MFLIMIT+1);
+
+#define KB *(1 <<10)
+#define MB *(1 <<20)
+#define GB *(1U<<30)
+
+#define LZ4_DISTANCE_ABSOLUTE_MAX 65535
+#if (LZ4_DISTANCE_MAX > LZ4_DISTANCE_ABSOLUTE_MAX)   /* max supported by LZ4 format */
+#  error "LZ4_DISTANCE_MAX is too big : must be <= 65535"
+#endif
+
+#define ML_BITS  4
+#define ML_MASK  ((1U<<ML_BITS)-1)
+#define RUN_BITS (8-ML_BITS)
+#define RUN_MASK ((1U<<RUN_BITS)-1)
+
+
+/*-************************************
+*  Error detection
+**************************************/
+#if defined(LZ4_DEBUG) && (LZ4_DEBUG>=1)
+#  include <assert.h>
+#else
+#  ifndef assert
+#    define assert(condition) ((void)0)
+#  endif
+#endif
+
+#define LZ4_STATIC_ASSERT(c)   { enum { LZ4_static_assert = 1/(int)(!!(c)) }; }   /* use after variable declarations */
+
+#if defined(LZ4_DEBUG) && (LZ4_DEBUG>=2)
+#  include <stdio.h>
+   static int g_debuglog_enable = 1;
+#  define DEBUGLOG(l, ...) {                          \
+        if ((g_debuglog_enable) && (l<=LZ4_DEBUG)) {  \
+            fprintf(stderr, __FILE__  " %i: ", __LINE__); \
+            fprintf(stderr, __VA_ARGS__);             \
+            fprintf(stderr, " \n");                   \
+    }   }
+#else
+#  define DEBUGLOG(l, ...) {}    /* disabled */
+#endif
+
+static int LZ4_isAligned(const void* ptr, size_t alignment)
+{
+    return ((size_t)ptr & (alignment -1)) == 0;
+}
+
+
+/*-************************************
+*  Types
+**************************************/
+#include <limits.h>
+#if defined(__cplusplus) || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */)
+# include <stdint.h>
+  typedef  uint8_t BYTE;
+  typedef uint16_t U16;
+  typedef uint32_t U32;
+  typedef  int32_t S32;
+  typedef uint64_t U64;
+  typedef uintptr_t uptrval;
+#else
+# if UINT_MAX != 4294967295UL
+#   error "LZ4 code (when not C++ or C99) assumes that sizeof(int) == 4"
+# endif
+  typedef unsigned char       BYTE;
+  typedef unsigned short      U16;
+  typedef unsigned int        U32;
+  typedef   signed int        S32;
+  typedef unsigned long long  U64;
+  typedef size_t              uptrval;   /* generally true, except OpenVMS-64 */
+#endif
+
+#if defined(__x86_64__)
+  typedef U64    reg_t;   /* 64-bits in x32 mode */
+#else
+  typedef size_t reg_t;   /* 32-bits in x32 mode */
+#endif
+
+typedef enum {
+    notLimited = 0,
+    limitedOutput = 1,
+    fillOutput = 2
+} limitedOutput_directive;
+
+
+/*-************************************
+*  Reading and writing into memory
+**************************************/
+
+/**
+ * LZ4 relies on memcpy with a constant size being inlined. In freestanding
+ * environments, the compiler can't assume the implementation of memcpy() is
+ * standard compliant, so it can't apply its specialized memcpy() inlining
+ * logic. When possible, use __builtin_memcpy() to tell the compiler to analyze
+ * memcpy() as if it were standard compliant, so it can inline it in freestanding
+ * environments. This is needed when decompressing the Linux Kernel, for example.
+ */
+#if !defined(LZ4_memcpy)
+#  if defined(__GNUC__) && (__GNUC__ >= 4)
+#    define LZ4_memcpy(dst, src, size) __builtin_memcpy(dst, src, size)
+#  else
+#    define LZ4_memcpy(dst, src, size) memcpy(dst, src, size)
+#  endif
+#endif
+
+#if !defined(LZ4_memmove)
+#  if defined(__GNUC__) && (__GNUC__ >= 4)
+#    define LZ4_memmove __builtin_memmove
+#  else
+#    define LZ4_memmove memmove
+#  endif
+#endif
+
+static unsigned LZ4_isLittleEndian(void)
+{
+    const union { U32 u; BYTE c[4]; } one = { 1 };   /* don't use static : performance detrimental */
+    return one.c[0];
+}
+
+#if defined(__GNUC__) || defined(__INTEL_COMPILER)
+#define LZ4_PACK( __Declaration__ ) __Declaration__ __attribute__((__packed__))
+#elif defined(_MSC_VER)
+#define LZ4_PACK( __Declaration__ ) __pragma( pack(push, 1) ) __Declaration__ __pragma( pack(pop))
+#endif
+
+#if defined(LZ4_FORCE_MEMORY_ACCESS) && (LZ4_FORCE_MEMORY_ACCESS==2)
+/* lie to the compiler about data alignment; use with caution */
+
+static U16 LZ4_read16(const void* memPtr) { return *(const U16*) memPtr; }
+static U32 LZ4_read32(const void* memPtr) { return *(const U32*) memPtr; }
+static reg_t LZ4_read_ARCH(const void* memPtr) { return *(const reg_t*) memPtr; }
+
+static void LZ4_write16(void* memPtr, U16 value) { *(U16*)memPtr = value; }
+static void LZ4_write32(void* memPtr, U32 value) { *(U32*)memPtr = value; }
+
+#elif defined(LZ4_FORCE_MEMORY_ACCESS) && (LZ4_FORCE_MEMORY_ACCESS==1)
+
+/* __pack instructions are safer, but compiler specific, hence potentially problematic for some compilers */
+/* currently only defined for gcc and icc */
+LZ4_PACK(typedef struct { U16 u16; }) LZ4_unalign16;
+LZ4_PACK(typedef struct { U32 u32; }) LZ4_unalign32;
+LZ4_PACK(typedef struct { reg_t uArch; }) LZ4_unalignST;
+
+static U16 LZ4_read16(const void* ptr) { return ((const LZ4_unalign16*)ptr)->u16; }
+static U32 LZ4_read32(const void* ptr) { return ((const LZ4_unalign32*)ptr)->u32; }
+static reg_t LZ4_read_ARCH(const void* ptr) { return ((const LZ4_unalignST*)ptr)->uArch; }
+
+static void LZ4_write16(void* memPtr, U16 value) { ((LZ4_unalign16*)memPtr)->u16 = value; }
+static void LZ4_write32(void* memPtr, U32 value) { ((LZ4_unalign32*)memPtr)->u32 = value; }
+
+#else  /* safe and portable access using memcpy() */
+
+static U16 LZ4_read16(const void* memPtr)
+{
+    U16 val; LZ4_memcpy(&val, memPtr, sizeof(val)); return val;
+}
+
+static U32 LZ4_read32(const void* memPtr)
+{
+    U32 val; LZ4_memcpy(&val, memPtr, sizeof(val)); return val;
+}
+
+static reg_t LZ4_read_ARCH(const void* memPtr)
+{
+    reg_t val; LZ4_memcpy(&val, memPtr, sizeof(val)); return val;
+}
+
+static void LZ4_write16(void* memPtr, U16 value)
+{
+    LZ4_memcpy(memPtr, &value, sizeof(value));
+}
+
+static void LZ4_write32(void* memPtr, U32 value)
+{
+    LZ4_memcpy(memPtr, &value, sizeof(value));
+}
+
+#endif /* LZ4_FORCE_MEMORY_ACCESS */
+
+
+static U16 LZ4_readLE16(const void* memPtr)
+{
+    if (LZ4_isLittleEndian()) {
+        return LZ4_read16(memPtr);
+    } else {
+        const BYTE* p = (const BYTE*)memPtr;
+        return (U16)((U16)p[0] | (p[1]<<8));
+    }
+}
+
+#ifdef LZ4_STATIC_LINKING_ONLY_ENDIANNESS_INDEPENDENT_OUTPUT
+static U32 LZ4_readLE32(const void* memPtr)
+{
+    if (LZ4_isLittleEndian()) {
+        return LZ4_read32(memPtr);
+    } else {
+        const BYTE* p = (const BYTE*)memPtr;
+        return (U32)p[0] | (p[1]<<8) | (p[2]<<16) | (p[3]<<24);
+    }
+}
+#endif
+
+static void LZ4_writeLE16(void* memPtr, U16 value)
+{
+    if (LZ4_isLittleEndian()) {
+        LZ4_write16(memPtr, value);
+    } else {
+        BYTE* p = (BYTE*)memPtr;
+        p[0] = (BYTE) value;
+        p[1] = (BYTE)(value>>8);
+    }
+}
+
+/* customized variant of memcpy, which can overwrite up to 8 bytes beyond dstEnd */
+LZ4_FORCE_INLINE
+void LZ4_wildCopy8(void* dstPtr, const void* srcPtr, void* dstEnd)
+{
+    BYTE* d = (BYTE*)dstPtr;
+    const BYTE* s = (const BYTE*)srcPtr;
+    BYTE* const e = (BYTE*)dstEnd;
+
+    do { LZ4_memcpy(d,s,8); d+=8; s+=8; } while (d<e);
+}
+
+static const unsigned inc32table[8] = {0, 1, 2,  1,  0,  4, 4, 4};
+static const int      dec64table[8] = {0, 0, 0, -1, -4,  1, 2, 3};
+
+
+#ifndef LZ4_FAST_DEC_LOOP
+#  if defined __i386__ || defined _M_IX86 || defined __x86_64__ || defined _M_X64
+#    define LZ4_FAST_DEC_LOOP 1
+#  elif defined(__aarch64__) && defined(__APPLE__)
+#    define LZ4_FAST_DEC_LOOP 1
+#  elif defined(__aarch64__) && !defined(__clang__)
+     /* On non-Apple aarch64, we disable this optimization for clang because
+      * on certain mobile chipsets, performance is reduced with clang. For
+      * more information refer to https://github.com/lz4/lz4/pull/707 */
+#    define LZ4_FAST_DEC_LOOP 1
+#  else
+#    define LZ4_FAST_DEC_LOOP 0
+#  endif
+#endif
+
+#if LZ4_FAST_DEC_LOOP
+
+LZ4_FORCE_INLINE void
+LZ4_memcpy_using_offset_base(BYTE* dstPtr, const BYTE* srcPtr, BYTE* dstEnd, const size_t offset)
+{
+    assert(srcPtr + offset == dstPtr);
+    if (offset < 8) {
+        LZ4_write32(dstPtr, 0);   /* silence an msan warning when offset==0 */
+        dstPtr[0] = srcPtr[0];
+        dstPtr[1] = srcPtr[1];
+        dstPtr[2] = srcPtr[2];
+        dstPtr[3] = srcPtr[3];
+        srcPtr += inc32table[offset];
+        LZ4_memcpy(dstPtr+4, srcPtr, 4);
+        srcPtr -= dec64table[offset];
+        dstPtr += 8;
+    } else {
+        LZ4_memcpy(dstPtr, srcPtr, 8);
+        dstPtr += 8;
+        srcPtr += 8;
+    }
+
+    LZ4_wildCopy8(dstPtr, srcPtr, dstEnd);
+}
+
+/* customized variant of memcpy, which can overwrite up to 32 bytes beyond dstEnd
+ * this version copies two times 16 bytes (instead of one time 32 bytes)
+ * because it must be compatible with offsets >= 16. */
+LZ4_FORCE_INLINE void
+LZ4_wildCopy32(void* dstPtr, const void* srcPtr, void* dstEnd)
+{
+    BYTE* d = (BYTE*)dstPtr;
+    const BYTE* s = (const BYTE*)srcPtr;
+    BYTE* const e = (BYTE*)dstEnd;
+
+    do { LZ4_memcpy(d,s,16); LZ4_memcpy(d+16,s+16,16); d+=32; s+=32; } while (d<e);
+}
+
+/* LZ4_memcpy_using_offset()  presumes :
+ * - dstEnd >= dstPtr + MINMATCH
+ * - there is at least 12 bytes available to write after dstEnd */
+LZ4_FORCE_INLINE void
+LZ4_memcpy_using_offset(BYTE* dstPtr, const BYTE* srcPtr, BYTE* dstEnd, const size_t offset)
+{
+    BYTE v[8];
+
+    assert(dstEnd >= dstPtr + MINMATCH);
+
+    switch(offset) {
+    case 1:
+        MEM_INIT(v, *srcPtr, 8);
+        break;
+    case 2:
+        LZ4_memcpy(v, srcPtr, 2);
+        LZ4_memcpy(&v[2], srcPtr, 2);
+#if defined(_MSC_VER) && (_MSC_VER <= 1937) /* MSVC 2022 ver 17.7 or earlier */
+#  pragma warning(push)
+#  pragma warning(disable : 6385) /* warning C6385: Reading invalid data from 'v'. */
+#endif
+        LZ4_memcpy(&v[4], v, 4);
+#if defined(_MSC_VER) && (_MSC_VER <= 1937) /* MSVC 2022 ver 17.7 or earlier */
+#  pragma warning(pop)
+#endif
+        break;
+    case 4:
+        LZ4_memcpy(v, srcPtr, 4);
+        LZ4_memcpy(&v[4], srcPtr, 4);
+        break;
+    default:
+        LZ4_memcpy_using_offset_base(dstPtr, srcPtr, dstEnd, offset);
+        return;
+    }
+
+    LZ4_memcpy(dstPtr, v, 8);
+    dstPtr += 8;
+    while (dstPtr < dstEnd) {
+        LZ4_memcpy(dstPtr, v, 8);
+        dstPtr += 8;
+    }
+}
+#endif
+
+
+/*-************************************
+*  Common functions
+**************************************/
+static unsigned LZ4_NbCommonBytes (reg_t val)
+{
+    assert(val != 0);
+    if (LZ4_isLittleEndian()) {
+        if (sizeof(val) == 8) {
+#       if defined(_MSC_VER) && (_MSC_VER >= 1800) && (defined(_M_AMD64) && !defined(_M_ARM64EC)) && !defined(LZ4_FORCE_SW_BITCOUNT)
+/*-*************************************************************************************************
+* ARM64EC is a Microsoft-designed ARM64 ABI compatible with AMD64 applications on ARM64 Windows 11.
+* The ARM64EC ABI does not support AVX/AVX2/AVX512 instructions, nor their relevant intrinsics
+* including _tzcnt_u64. Therefore, we need to neuter the _tzcnt_u64 code path for ARM64EC.
+****************************************************************************************************/
+#         if defined(__clang__) && (__clang_major__ < 10)
+            /* Avoid undefined clang-cl intrinsics issue.
+             * See https://github.com/lz4/lz4/pull/1017 for details. */
+            return (unsigned)__builtin_ia32_tzcnt_u64(val) >> 3;
+#         else
+            /* x64 CPUS without BMI support interpret `TZCNT` as `REP BSF` */
+            return (unsigned)_tzcnt_u64(val) >> 3;
+#         endif
+#       elif defined(_MSC_VER) && defined(_WIN64) && !defined(LZ4_FORCE_SW_BITCOUNT)
+            unsigned long r = 0;
+            _BitScanForward64(&r, (U64)val);
+            return (unsigned)r >> 3;
+#       elif (defined(__clang__) || (defined(__GNUC__) && ((__GNUC__ > 3) || \
+                            ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))) && \
+                                        !defined(LZ4_FORCE_SW_BITCOUNT)
+            return (unsigned)__builtin_ctzll((U64)val) >> 3;
+#       else
+            const U64 m = 0x0101010101010101ULL;
+            val ^= val - 1;
+            return (unsigned)(((U64)((val & (m - 1)) * m)) >> 56);
+#       endif
+        } else /* 32 bits */ {
+#       if defined(_MSC_VER) && (_MSC_VER >= 1400) && !defined(LZ4_FORCE_SW_BITCOUNT)
+            unsigned long r;
+            _BitScanForward(&r, (U32)val);
+            return (unsigned)r >> 3;
+#       elif (defined(__clang__) || (defined(__GNUC__) && ((__GNUC__ > 3) || \
+                            ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))) && \
+                        !defined(__TINYC__) && !defined(LZ4_FORCE_SW_BITCOUNT)
+            return (unsigned)__builtin_ctz((U32)val) >> 3;
+#       else
+            const U32 m = 0x01010101;
+            return (unsigned)((((val - 1) ^ val) & (m - 1)) * m) >> 24;
+#       endif
+        }
+    } else   /* Big Endian CPU */ {
+        if (sizeof(val)==8) {
+#       if (defined(__clang__) || (defined(__GNUC__) && ((__GNUC__ > 3) || \
+                            ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))) && \
+                        !defined(__TINYC__) && !defined(LZ4_FORCE_SW_BITCOUNT)
+            return (unsigned)__builtin_clzll((U64)val) >> 3;
+#       else
+#if 1
+            /* this method is probably faster,
+             * but adds a 128 bytes lookup table */
+            static const unsigned char ctz7_tab[128] = {
+                7, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
+                4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
+                5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
+                4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
+                6, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
+                4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
+                5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
+                4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
+            };
+            U64 const mask = 0x0101010101010101ULL;
+            U64 const t = (((val >> 8) - mask) | val) & mask;
+            return ctz7_tab[(t * 0x0080402010080402ULL) >> 57];
+#else
+            /* this method doesn't consume memory space like the previous one,
+             * but it contains several branches,
+             * that may end up slowing execution */
+            static const U32 by32 = sizeof(val)*4;  /* 32 on 64 bits (goal), 16 on 32 bits.
+            Just to avoid some static analyzer complaining about shift by 32 on 32-bits target.
+            Note that this code path is never triggered in 32-bits mode. */
+            unsigned r;
+            if (!(val>>by32)) { r=4; } else { r=0; val>>=by32; }
+            if (!(val>>16)) { r+=2; val>>=8; } else { val>>=24; }
+            r += (!val);
+            return r;
+#endif
+#       endif
+        } else /* 32 bits */ {
+#       if (defined(__clang__) || (defined(__GNUC__) && ((__GNUC__ > 3) || \
+                            ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))) && \
+                                        !defined(LZ4_FORCE_SW_BITCOUNT)
+            return (unsigned)__builtin_clz((U32)val) >> 3;
+#       else
+            val >>= 8;
+            val = ((((val + 0x00FFFF00) | 0x00FFFFFF) + val) |
+              (val + 0x00FF0000)) >> 24;
+            return (unsigned)val ^ 3;
+#       endif
+        }
+    }
+}
+
+
+#define STEPSIZE sizeof(reg_t)
+LZ4_FORCE_INLINE
+unsigned LZ4_count(const BYTE* pIn, const BYTE* pMatch, const BYTE* pInLimit)
+{
+    const BYTE* const pStart = pIn;
+
+    if (likely(pIn < pInLimit-(STEPSIZE-1))) {
+        reg_t const diff = LZ4_read_ARCH(pMatch) ^ LZ4_read_ARCH(pIn);
+        if (!diff) {
+            pIn+=STEPSIZE; pMatch+=STEPSIZE;
+        } else {
+            return LZ4_NbCommonBytes(diff);
+    }   }
+
+    while (likely(pIn < pInLimit-(STEPSIZE-1))) {
+        reg_t const diff = LZ4_read_ARCH(pMatch) ^ LZ4_read_ARCH(pIn);
+        if (!diff) { pIn+=STEPSIZE; pMatch+=STEPSIZE; continue; }
+        pIn += LZ4_NbCommonBytes(diff);
+        return (unsigned)(pIn - pStart);
+    }
+
+    if ((STEPSIZE==8) && (pIn<(pInLimit-3)) && (LZ4_read32(pMatch) == LZ4_read32(pIn))) { pIn+=4; pMatch+=4; }
+    if ((pIn<(pInLimit-1)) && (LZ4_read16(pMatch) == LZ4_read16(pIn))) { pIn+=2; pMatch+=2; }
+    if ((pIn<pInLimit) && (*pMatch == *pIn)) pIn++;
+    return (unsigned)(pIn - pStart);
+}
+
+
+#ifndef LZ4_COMMONDEFS_ONLY
+/*-************************************
+*  Local Constants
+**************************************/
+static const int LZ4_64Klimit = ((64 KB) + (MFLIMIT-1));
+static const U32 LZ4_skipTrigger = 6;  /* Increase this value ==> compression run slower on incompressible data */
+
+
+/*-************************************
+*  Local Structures and types
+**************************************/
+typedef enum { clearedTable = 0, byPtr, byU32, byU16 } tableType_t;
+
+/**
+ * This enum distinguishes several different modes of accessing previous
+ * content in the stream.
+ *
+ * - noDict        : There is no preceding content.
+ * - withPrefix64k : Table entries up to ctx->dictSize before the current blob
+ *                   blob being compressed are valid and refer to the preceding
+ *                   content (of length ctx->dictSize), which is available
+ *                   contiguously preceding in memory the content currently
+ *                   being compressed.
+ * - usingExtDict  : Like withPrefix64k, but the preceding content is somewhere
+ *                   else in memory, starting at ctx->dictionary with length
+ *                   ctx->dictSize.
+ * - usingDictCtx  : Everything concerning the preceding content is
+ *                   in a separate context, pointed to by ctx->dictCtx.
+ *                   ctx->dictionary, ctx->dictSize, and table entries
+ *                   in the current context that refer to positions
+ *                   preceding the beginning of the current compression are
+ *                   ignored. Instead, ctx->dictCtx->dictionary and ctx->dictCtx
+ *                   ->dictSize describe the location and size of the preceding
+ *                   content, and matches are found by looking in the ctx
+ *                   ->dictCtx->hashTable.
+ */
+typedef enum { noDict = 0, withPrefix64k, usingExtDict, usingDictCtx } dict_directive;
+typedef enum { noDictIssue = 0, dictSmall } dictIssue_directive;
+
+
+/*-************************************
+*  Local Utils
+**************************************/
+int LZ4_versionNumber (void) { return LZ4_VERSION_NUMBER; }
+const char* LZ4_versionString(void) { return LZ4_VERSION_STRING; }
+int LZ4_compressBound(int isize)  { return LZ4_COMPRESSBOUND(isize); }
+int LZ4_sizeofState(void) { return sizeof(LZ4_stream_t); }
+
+
+/*-****************************************
+*  Internal Definitions, used only in Tests
+*******************************************/
+#if defined (__cplusplus)
+extern "C" {
+#endif
+
+int LZ4_compress_forceExtDict (LZ4_stream_t* LZ4_dict, const char* source, char* dest, int srcSize);
+
+int LZ4_decompress_safe_forceExtDict(const char* source, char* dest,
+                                     int compressedSize, int maxOutputSize,
+                                     const void* dictStart, size_t dictSize);
+int LZ4_decompress_safe_partial_forceExtDict(const char* source, char* dest,
+                                     int compressedSize, int targetOutputSize, int dstCapacity,
+                                     const void* dictStart, size_t dictSize);
+#if defined (__cplusplus)
+}
+#endif
+
+/*-******************************
+*  Compression functions
+********************************/
+LZ4_FORCE_INLINE U32 LZ4_hash4(U32 sequence, tableType_t const tableType)
+{
+    if (tableType == byU16)
+        return ((sequence * 2654435761U) >> ((MINMATCH*8)-(LZ4_HASHLOG+1)));
+    else
+        return ((sequence * 2654435761U) >> ((MINMATCH*8)-LZ4_HASHLOG));
+}
+
+LZ4_FORCE_INLINE U32 LZ4_hash5(U64 sequence, tableType_t const tableType)
+{
+    const U32 hashLog = (tableType == byU16) ? LZ4_HASHLOG+1 : LZ4_HASHLOG;
+    if (LZ4_isLittleEndian()) {
+        const U64 prime5bytes = 889523592379ULL;
+        return (U32)(((sequence << 24) * prime5bytes) >> (64 - hashLog));
+    } else {
+        const U64 prime8bytes = 11400714785074694791ULL;
+        return (U32)(((sequence >> 24) * prime8bytes) >> (64 - hashLog));
+    }
+}
+
+LZ4_FORCE_INLINE U32 LZ4_hashPosition(const void* const p, tableType_t const tableType)
+{
+    if ((sizeof(reg_t)==8) && (tableType != byU16)) return LZ4_hash5(LZ4_read_ARCH(p), tableType);
+
+#ifdef LZ4_STATIC_LINKING_ONLY_ENDIANNESS_INDEPENDENT_OUTPUT
+    return LZ4_hash4(LZ4_readLE32(p), tableType);
+#else
+    return LZ4_hash4(LZ4_read32(p), tableType);
+#endif
+}
+
+LZ4_FORCE_INLINE void LZ4_clearHash(U32 h, void* tableBase, tableType_t const tableType)
+{
+    switch (tableType)
+    {
+    default: /* fallthrough */
+    case clearedTable: { /* illegal! */ assert(0); return; }
+    case byPtr: { const BYTE** hashTable = (const BYTE**)tableBase; hashTable[h] = NULL; return; }
+    case byU32: { U32* hashTable = (U32*) tableBase; hashTable[h] = 0; return; }
+    case byU16: { U16* hashTable = (U16*) tableBase; hashTable[h] = 0; return; }
+    }
+}
+
+LZ4_FORCE_INLINE void LZ4_putIndexOnHash(U32 idx, U32 h, void* tableBase, tableType_t const tableType)
+{
+    switch (tableType)
+    {
+    default: /* fallthrough */
+    case clearedTable: /* fallthrough */
+    case byPtr: { /* illegal! */ assert(0); return; }
+    case byU32: { U32* hashTable = (U32*) tableBase; hashTable[h] = idx; return; }
+    case byU16: { U16* hashTable = (U16*) tableBase; assert(idx < 65536); hashTable[h] = (U16)idx; return; }
+    }
+}
+
+/* LZ4_putPosition*() : only used in byPtr mode */
+LZ4_FORCE_INLINE void LZ4_putPositionOnHash(const BYTE* p, U32 h,
+                                  void* tableBase, tableType_t const tableType)
+{
+    const BYTE** const hashTable = (const BYTE**)tableBase;
+    assert(tableType == byPtr); (void)tableType;
+    hashTable[h] = p;
+}
+
+LZ4_FORCE_INLINE void LZ4_putPosition(const BYTE* p, void* tableBase, tableType_t tableType)
+{
+    U32 const h = LZ4_hashPosition(p, tableType);
+    LZ4_putPositionOnHash(p, h, tableBase, tableType);
+}
+
+/* LZ4_getIndexOnHash() :
+ * Index of match position registered in hash table.
+ * hash position must be calculated by using base+index, or dictBase+index.
+ * Assumption 1 : only valid if tableType == byU32 or byU16.
+ * Assumption 2 : h is presumed valid (within limits of hash table)
+ */
+LZ4_FORCE_INLINE U32 LZ4_getIndexOnHash(U32 h, const void* tableBase, tableType_t tableType)
+{
+    LZ4_STATIC_ASSERT(LZ4_MEMORY_USAGE > 2);
+    if (tableType == byU32) {
+        const U32* const hashTable = (const U32*) tableBase;
+        assert(h < (1U << (LZ4_MEMORY_USAGE-2)));
+        return hashTable[h];
+    }
+    if (tableType == byU16) {
+        const U16* const hashTable = (const U16*) tableBase;
+        assert(h < (1U << (LZ4_MEMORY_USAGE-1)));
+        return hashTable[h];
+    }
+    assert(0); return 0;  /* forbidden case */
+}
+
+static const BYTE* LZ4_getPositionOnHash(U32 h, const void* tableBase, tableType_t tableType)
+{
+    assert(tableType == byPtr); (void)tableType;
+    { const BYTE* const* hashTable = (const BYTE* const*) tableBase; return hashTable[h]; }
+}
+
+LZ4_FORCE_INLINE const BYTE*
+LZ4_getPosition(const BYTE* p,
+                const void* tableBase, tableType_t tableType)
+{
+    U32 const h = LZ4_hashPosition(p, tableType);
+    return LZ4_getPositionOnHash(h, tableBase, tableType);
+}
+
+LZ4_FORCE_INLINE void
+LZ4_prepareTable(LZ4_stream_t_internal* const cctx,
+           const int inputSize,
+           const tableType_t tableType) {
+    /* If the table hasn't been used, it's guaranteed to be zeroed out, and is
+     * therefore safe to use no matter what mode we're in. Otherwise, we figure
+     * out if it's safe to leave as is or whether it needs to be reset.
+     */
+    if ((tableType_t)cctx->tableType != clearedTable) {
+        assert(inputSize >= 0);
+        if ((tableType_t)cctx->tableType != tableType
+          || ((tableType == byU16) && cctx->currentOffset + (unsigned)inputSize >= 0xFFFFU)
+          || ((tableType == byU32) && cctx->currentOffset > 1 GB)
+          || tableType == byPtr
+          || inputSize >= 4 KB)
+        {
+            DEBUGLOG(4, "LZ4_prepareTable: Resetting table in %p", cctx);
+            MEM_INIT(cctx->hashTable, 0, LZ4_HASHTABLESIZE);
+            cctx->currentOffset = 0;
+            cctx->tableType = (U32)clearedTable;
+        } else {
+            DEBUGLOG(4, "LZ4_prepareTable: Re-use hash table (no reset)");
+        }
+    }
+
+    /* Adding a gap, so all previous entries are > LZ4_DISTANCE_MAX back,
+     * is faster than compressing without a gap.
+     * However, compressing with currentOffset == 0 is faster still,
+     * so we preserve that case.
+     */
+    if (cctx->currentOffset != 0 && tableType == byU32) {
+        DEBUGLOG(5, "LZ4_prepareTable: adding 64KB to currentOffset");
+        cctx->currentOffset += 64 KB;
+    }
+
+    /* Finally, clear history */
+    cctx->dictCtx = NULL;
+    cctx->dictionary = NULL;
+    cctx->dictSize = 0;
+}
+
+/** LZ4_compress_generic_validated() :
+ *  inlined, to ensure branches are decided at compilation time.
+ *  The following conditions are presumed already validated:
+ *  - source != NULL
+ *  - inputSize > 0
+ */
+LZ4_FORCE_INLINE int LZ4_compress_generic_validated(
+                 LZ4_stream_t_internal* const cctx,
+                 const char* const source,
+                 char* const dest,
+                 const int inputSize,
+                 int*  inputConsumed, /* only written when outputDirective == fillOutput */
+                 const int maxOutputSize,
+                 const limitedOutput_directive outputDirective,
+                 const tableType_t tableType,
+                 const dict_directive dictDirective,
+                 const dictIssue_directive dictIssue,
+                 const int acceleration)
+{
+    int result;
+    const BYTE* ip = (const BYTE*)source;
+
+    U32 const startIndex = cctx->currentOffset;
+    const BYTE* base = (const BYTE*)source - startIndex;
+    const BYTE* lowLimit;
+
+    const LZ4_stream_t_internal* dictCtx = (const LZ4_stream_t_internal*) cctx->dictCtx;
+    const BYTE* const dictionary =
+        dictDirective == usingDictCtx ? dictCtx->dictionary : cctx->dictionary;
+    const U32 dictSize =
+        dictDirective == usingDictCtx ? dictCtx->dictSize : cctx->dictSize;
+    const U32 dictDelta =
+        (dictDirective == usingDictCtx) ? startIndex - dictCtx->currentOffset : 0;   /* make indexes in dictCtx comparable with indexes in current context */
+
+    int const maybe_extMem = (dictDirective == usingExtDict) || (dictDirective == usingDictCtx);
+    U32 const prefixIdxLimit = startIndex - dictSize;   /* used when dictDirective == dictSmall */
+    const BYTE* const dictEnd = dictionary ? dictionary + dictSize : dictionary;
+    const BYTE* anchor = (const BYTE*) source;
+    const BYTE* const iend = ip + inputSize;
+    const BYTE* const mflimitPlusOne = iend - MFLIMIT + 1;
+    const BYTE* const matchlimit = iend - LASTLITERALS;
+
+    /* the dictCtx currentOffset is indexed on the start of the dictionary,
+     * while a dictionary in the current context precedes the currentOffset */
+    const BYTE* dictBase = (dictionary == NULL) ? NULL :
+                           (dictDirective == usingDictCtx) ?
+                            dictionary + dictSize - dictCtx->currentOffset :
+                            dictionary + dictSize - startIndex;
+
+    BYTE* op = (BYTE*) dest;
+    BYTE* const olimit = op + maxOutputSize;
+
+    U32 offset = 0;
+    U32 forwardH;
+
+    DEBUGLOG(5, "LZ4_compress_generic_validated: srcSize=%i, tableType=%u", inputSize, tableType);
+    assert(ip != NULL);
+    if (tableType == byU16) assert(inputSize<LZ4_64Klimit);  /* Size too large (not within 64K limit) */
+    if (tableType == byPtr) assert(dictDirective==noDict);   /* only supported use case with byPtr */
+    /* If init conditions are not met, we don't have to mark stream
+     * as having dirty context, since no action was taken yet */
+    if (outputDirective == fillOutput && maxOutputSize < 1) { return 0; } /* Impossible to store anything */
+    assert(acceleration >= 1);
+
+    lowLimit = (const BYTE*)source - (dictDirective == withPrefix64k ? dictSize : 0);
+
+    /* Update context state */
+    if (dictDirective == usingDictCtx) {
+        /* Subsequent linked blocks can't use the dictionary. */
+        /* Instead, they use the block we just compressed. */
+        cctx->dictCtx = NULL;
+        cctx->dictSize = (U32)inputSize;
+    } else {
+        cctx->dictSize += (U32)inputSize;
+    }
+    cctx->currentOffset += (U32)inputSize;
+    cctx->tableType = (U32)tableType;
+
+    if (inputSize<LZ4_minLength) goto _last_literals;        /* Input too small, no compression (all literals) */
+
+    /* First Byte */
+    {   U32 const h = LZ4_hashPosition(ip, tableType);
+        if (tableType == byPtr) {
+            LZ4_putPositionOnHash(ip, h, cctx->hashTable, byPtr);
+        } else {
+            LZ4_putIndexOnHash(startIndex, h, cctx->hashTable, tableType);
+    }   }
+    ip++; forwardH = LZ4_hashPosition(ip, tableType);
+
+    /* Main Loop */
+    for ( ; ; ) {
+        const BYTE* match;
+        BYTE* token;
+        const BYTE* filledIp;
+
+        /* Find a match */
+        if (tableType == byPtr) {
+            const BYTE* forwardIp = ip;
+            int step = 1;
+            int searchMatchNb = acceleration << LZ4_skipTrigger;
+            do {
+                U32 const h = forwardH;
+                ip = forwardIp;
+                forwardIp += step;
+                step = (searchMatchNb++ >> LZ4_skipTrigger);
+
+                if (unlikely(forwardIp > mflimitPlusOne)) goto _last_literals;
+                assert(ip < mflimitPlusOne);
+
+                match = LZ4_getPositionOnHash(h, cctx->hashTable, tableType);
+                forwardH = LZ4_hashPosition(forwardIp, tableType);
+                LZ4_putPositionOnHash(ip, h, cctx->hashTable, tableType);
+
+            } while ( (match+LZ4_DISTANCE_MAX < ip)
+                   || (LZ4_read32(match) != LZ4_read32(ip)) );
+
+        } else {   /* byU32, byU16 */
+
+            const BYTE* forwardIp = ip;
+            int step = 1;
+            int searchMatchNb = acceleration << LZ4_skipTrigger;
+            do {
+                U32 const h = forwardH;
+                U32 const current = (U32)(forwardIp - base);
+                U32 matchIndex = LZ4_getIndexOnHash(h, cctx->hashTable, tableType);
+                assert(matchIndex <= current);
+                assert(forwardIp - base < (ptrdiff_t)(2 GB - 1));
+                ip = forwardIp;
+                forwardIp += step;
+                step = (searchMatchNb++ >> LZ4_skipTrigger);
+
+                if (unlikely(forwardIp > mflimitPlusOne)) goto _last_literals;
+                assert(ip < mflimitPlusOne);
+
+                if (dictDirective == usingDictCtx) {
+                    if (matchIndex < startIndex) {
+                        /* there was no match, try the dictionary */
+                        assert(tableType == byU32);
+                        matchIndex = LZ4_getIndexOnHash(h, dictCtx->hashTable, byU32);
+                        match = dictBase + matchIndex;
+                        matchIndex += dictDelta;   /* make dictCtx index comparable with current context */
+                        lowLimit = dictionary;
+                    } else {
+                        match = base + matchIndex;
+                        lowLimit = (const BYTE*)source;
+                    }
+                } else if (dictDirective == usingExtDict) {
+                    if (matchIndex < startIndex) {
+                        DEBUGLOG(7, "extDict candidate: matchIndex=%5u  <  startIndex=%5u", matchIndex, startIndex);
+                        assert(startIndex - matchIndex >= MINMATCH);
+                        assert(dictBase);
+                        match = dictBase + matchIndex;
+                        lowLimit = dictionary;
+                    } else {
+                        match = base + matchIndex;
+                        lowLimit = (const BYTE*)source;
+                    }
+                } else {   /* single continuous memory segment */
+                    match = base + matchIndex;
+                }
+                forwardH = LZ4_hashPosition(forwardIp, tableType);
+                LZ4_putIndexOnHash(current, h, cctx->hashTable, tableType);
+
+                DEBUGLOG(7, "candidate at pos=%u  (offset=%u \n", matchIndex, current - matchIndex);
+                if ((dictIssue == dictSmall) && (matchIndex < prefixIdxLimit)) { continue; }    /* match outside of valid area */
+                assert(matchIndex < current);
+                if ( ((tableType != byU16) || (LZ4_DISTANCE_MAX < LZ4_DISTANCE_ABSOLUTE_MAX))
+                  && (matchIndex+LZ4_DISTANCE_MAX < current)) {
+                    continue;
+                } /* too far */
+                assert((current - matchIndex) <= LZ4_DISTANCE_MAX);  /* match now expected within distance */
+
+                if (LZ4_read32(match) == LZ4_read32(ip)) {
+                    if (maybe_extMem) offset = current - matchIndex;
+                    break;   /* match found */
+                }
+
+            } while(1);
+        }
+
+        /* Catch up */
+        filledIp = ip;
+        assert(ip > anchor); /* this is always true as ip has been advanced before entering the main loop */
+        if ((match > lowLimit) && unlikely(ip[-1] == match[-1])) {
+            do { ip--; match--; } while (((ip > anchor) & (match > lowLimit)) && (unlikely(ip[-1] == match[-1])));
+        }
+
+        /* Encode Literals */
+        {   unsigned const litLength = (unsigned)(ip - anchor);
+            token = op++;
+            if ((outputDirective == limitedOutput) &&  /* Check output buffer overflow */
+                (unlikely(op + litLength + (2 + 1 + LASTLITERALS) + (litLength/255) > olimit)) ) {
+                return 0;   /* cannot compress within `dst` budget. Stored indexes in hash table are nonetheless fine */
+            }
+            if ((outputDirective == fillOutput) &&
+                (unlikely(op + (litLength+240)/255 /* litlen */ + litLength /* literals */ + 2 /* offset */ + 1 /* token */ + MFLIMIT - MINMATCH /* min last literals so last match is <= end - MFLIMIT */ > olimit))) {
+                op--;
+                goto _last_literals;
+            }
+            if (litLength >= RUN_MASK) {
+                unsigned len = litLength - RUN_MASK;
+                *token = (RUN_MASK<<ML_BITS);
+                for(; len >= 255 ; len-=255) *op++ = 255;
+                *op++ = (BYTE)len;
+            }
+            else *token = (BYTE)(litLength<<ML_BITS);
+
+            /* Copy Literals */
+            LZ4_wildCopy8(op, anchor, op+litLength);
+            op+=litLength;
+            DEBUGLOG(6, "seq.start:%i, literals=%u, match.start:%i",
+                        (int)(anchor-(const BYTE*)source), litLength, (int)(ip-(const BYTE*)source));
+        }
+
+_next_match:
+        /* at this stage, the following variables must be correctly set :
+         * - ip : at start of LZ operation
+         * - match : at start of previous pattern occurrence; can be within current prefix, or within extDict
+         * - offset : if maybe_ext_memSegment==1 (constant)
+         * - lowLimit : must be == dictionary to mean "match is within extDict"; must be == source otherwise
+         * - token and *token : position to write 4-bits for match length; higher 4-bits for literal length supposed already written
+         */
+
+        if ((outputDirective == fillOutput) &&
+            (op + 2 /* offset */ + 1 /* token */ + MFLIMIT - MINMATCH /* min last literals so last match is <= end - MFLIMIT */ > olimit)) {
+            /* the match was too close to the end, rewind and go to last literals */
+            op = token;
+            goto _last_literals;
+        }
+
+        /* Encode Offset */
+        if (maybe_extMem) {   /* static test */
+            DEBUGLOG(6, "             with offset=%u  (ext if > %i)", offset, (int)(ip - (const BYTE*)source));
+            assert(offset <= LZ4_DISTANCE_MAX && offset > 0);
+            LZ4_writeLE16(op, (U16)offset); op+=2;
+        } else  {
+            DEBUGLOG(6, "             with offset=%u  (same segment)", (U32)(ip - match));
+            assert(ip-match <= LZ4_DISTANCE_MAX);
+            LZ4_writeLE16(op, (U16)(ip - match)); op+=2;
+        }
+
+        /* Encode MatchLength */
+        {   unsigned matchCode;
+
+            if ( (dictDirective==usingExtDict || dictDirective==usingDictCtx)
+              && (lowLimit==dictionary) /* match within extDict */ ) {
+                const BYTE* limit = ip + (dictEnd-match);
+                assert(dictEnd > match);
+                if (limit > matchlimit) limit = matchlimit;
+                matchCode = LZ4_count(ip+MINMATCH, match+MINMATCH, limit);
+                ip += (size_t)matchCode + MINMATCH;
+                if (ip==limit) {
+                    unsigned const more = LZ4_count(limit, (const BYTE*)source, matchlimit);
+                    matchCode += more;
+                    ip += more;
+                }
+                DEBUGLOG(6, "             with matchLength=%u starting in extDict", matchCode+MINMATCH);
+            } else {
+                matchCode = LZ4_count(ip+MINMATCH, match+MINMATCH, matchlimit);
+                ip += (size_t)matchCode + MINMATCH;
+                DEBUGLOG(6, "             with matchLength=%u", matchCode+MINMATCH);
+            }
+
+            if ((outputDirective) &&    /* Check output buffer overflow */
+                (unlikely(op + (1 + LASTLITERALS) + (matchCode+240)/255 > olimit)) ) {
+                if (outputDirective == fillOutput) {
+                    /* Match description too long : reduce it */
+                    U32 newMatchCode = 15 /* in token */ - 1 /* to avoid needing a zero byte */ + ((U32)(olimit - op) - 1 - LASTLITERALS) * 255;
+                    ip -= matchCode - newMatchCode;
+                    assert(newMatchCode < matchCode);
+                    matchCode = newMatchCode;
+                    if (unlikely(ip <= filledIp)) {
+                        /* We have already filled up to filledIp so if ip ends up less than filledIp
+                         * we have positions in the hash table beyond the current position. This is
+                         * a problem if we reuse the hash table. So we have to remove these positions
+                         * from the hash table.
+                         */
+                        const BYTE* ptr;
+                        DEBUGLOG(5, "Clearing %u positions", (U32)(filledIp - ip));
+                        for (ptr = ip; ptr <= filledIp; ++ptr) {
+                            U32 const h = LZ4_hashPosition(ptr, tableType);
+                            LZ4_clearHash(h, cctx->hashTable, tableType);
+                        }
+                    }
+                } else {
+                    assert(outputDirective == limitedOutput);
+                    return 0;   /* cannot compress within `dst` budget. Stored indexes in hash table are nonetheless fine */
+                }
+            }
+            if (matchCode >= ML_MASK) {
+                *token += ML_MASK;
+                matchCode -= ML_MASK;
+                LZ4_write32(op, 0xFFFFFFFF);
+                while (matchCode >= 4*255) {
+                    op+=4;
+                    LZ4_write32(op, 0xFFFFFFFF);
+                    matchCode -= 4*255;
+                }
+                op += matchCode / 255;
+                *op++ = (BYTE)(matchCode % 255);
+            } else
+                *token += (BYTE)(matchCode);
+        }
+        /* Ensure we have enough space for the last literals. */
+        assert(!(outputDirective == fillOutput && op + 1 + LASTLITERALS > olimit));
+
+        anchor = ip;
+
+        /* Test end of chunk */
+        if (ip >= mflimitPlusOne) break;
+
+        /* Fill table */
+        {   U32 const h = LZ4_hashPosition(ip-2, tableType);
+            if (tableType == byPtr) {
+                LZ4_putPositionOnHash(ip-2, h, cctx->hashTable, byPtr);
+            } else {
+                U32 const idx = (U32)((ip-2) - base);
+                LZ4_putIndexOnHash(idx, h, cctx->hashTable, tableType);
+        }   }
+
+        /* Test next position */
+        if (tableType == byPtr) {
+
+            match = LZ4_getPosition(ip, cctx->hashTable, tableType);
+            LZ4_putPosition(ip, cctx->hashTable, tableType);
+            if ( (match+LZ4_DISTANCE_MAX >= ip)
+              && (LZ4_read32(match) == LZ4_read32(ip)) )
+            { token=op++; *token=0; goto _next_match; }
+
+        } else {   /* byU32, byU16 */
+
+            U32 const h = LZ4_hashPosition(ip, tableType);
+            U32 const current = (U32)(ip-base);
+            U32 matchIndex = LZ4_getIndexOnHash(h, cctx->hashTable, tableType);
+            assert(matchIndex < current);
+            if (dictDirective == usingDictCtx) {
+                if (matchIndex < startIndex) {
+                    /* there was no match, try the dictionary */
+                    assert(tableType == byU32);
+                    matchIndex = LZ4_getIndexOnHash(h, dictCtx->hashTable, byU32);
+                    match = dictBase + matchIndex;
+                    lowLimit = dictionary;   /* required for match length counter */
+                    matchIndex += dictDelta;
+                } else {
+                    match = base + matchIndex;
+                    lowLimit = (const BYTE*)source;  /* required for match length counter */
+                }
+            } else if (dictDirective==usingExtDict) {
+                if (matchIndex < startIndex) {
+                    assert(dictBase);
+                    match = dictBase + matchIndex;
+                    lowLimit = dictionary;   /* required for match length counter */
+                } else {
+                    match = base + matchIndex;
+                    lowLimit = (const BYTE*)source;   /* required for match length counter */
+                }
+            } else {   /* single memory segment */
+                match = base + matchIndex;
+            }
+            LZ4_putIndexOnHash(current, h, cctx->hashTable, tableType);
+            assert(matchIndex < current);
+            if ( ((dictIssue==dictSmall) ? (matchIndex >= prefixIdxLimit) : 1)
+              && (((tableType==byU16) && (LZ4_DISTANCE_MAX == LZ4_DISTANCE_ABSOLUTE_MAX)) ? 1 : (matchIndex+LZ4_DISTANCE_MAX >= current))
+              && (LZ4_read32(match) == LZ4_read32(ip)) ) {
+                token=op++;
+                *token=0;
+                if (maybe_extMem) offset = current - matchIndex;
+                DEBUGLOG(6, "seq.start:%i, literals=%u, match.start:%i",
+                            (int)(anchor-(const BYTE*)source), 0, (int)(ip-(const BYTE*)source));
+                goto _next_match;
+            }
+        }
+
+        /* Prepare next loop */
+        forwardH = LZ4_hashPosition(++ip, tableType);
+
+    }
+
+_last_literals:
+    /* Encode Last Literals */
+    {   size_t lastRun = (size_t)(iend - anchor);
+        if ( (outputDirective) &&  /* Check output buffer overflow */
+            (op + lastRun + 1 + ((lastRun+255-RUN_MASK)/255) > olimit)) {
+            if (outputDirective == fillOutput) {
+                /* adapt lastRun to fill 'dst' */
+                assert(olimit >= op);
+                lastRun  = (size_t)(olimit-op) - 1/*token*/;
+                lastRun -= (lastRun + 256 - RUN_MASK) / 256;  /*additional length tokens*/
+            } else {
+                assert(outputDirective == limitedOutput);
+                return 0;   /* cannot compress within `dst` budget. Stored indexes in hash table are nonetheless fine */
+            }
+        }
+        DEBUGLOG(6, "Final literal run : %i literals", (int)lastRun);
+        if (lastRun >= RUN_MASK) {
+            size_t accumulator = lastRun - RUN_MASK;
+            *op++ = RUN_MASK << ML_BITS;
+            for(; accumulator >= 255 ; accumulator-=255) *op++ = 255;
+            *op++ = (BYTE) accumulator;
+        } else {
+            *op++ = (BYTE)(lastRun<<ML_BITS);
+        }
+        LZ4_memcpy(op, anchor, lastRun);
+        ip = anchor + lastRun;
+        op += lastRun;
+    }
+
+    if (outputDirective == fillOutput) {
+        *inputConsumed = (int) (((const char*)ip)-source);
+    }
+    result = (int)(((char*)op) - dest);
+    assert(result > 0);
+    DEBUGLOG(5, "LZ4_compress_generic: compressed %i bytes into %i bytes", inputSize, result);
+    return result;
+}
+
+/** LZ4_compress_generic() :
+ *  inlined, to ensure branches are decided at compilation time;
+ *  takes care of src == (NULL, 0)
+ *  and forward the rest to LZ4_compress_generic_validated */
+LZ4_FORCE_INLINE int LZ4_compress_generic(
+                 LZ4_stream_t_internal* const cctx,
+                 const char* const src,
+                 char* const dst,
+                 const int srcSize,
+                 int *inputConsumed, /* only written when outputDirective == fillOutput */
+                 const int dstCapacity,
+                 const limitedOutput_directive outputDirective,
+                 const tableType_t tableType,
+                 const dict_directive dictDirective,
+                 const dictIssue_directive dictIssue,
+                 const int acceleration)
+{
+    DEBUGLOG(5, "LZ4_compress_generic: srcSize=%i, dstCapacity=%i",
+                srcSize, dstCapacity);
+
+    if ((U32)srcSize > (U32)LZ4_MAX_INPUT_SIZE) { return 0; }  /* Unsupported srcSize, too large (or negative) */
+    if (srcSize == 0) {   /* src == NULL supported if srcSize == 0 */
+        if (outputDirective != notLimited && dstCapacity <= 0) return 0;  /* no output, can't write anything */
+        DEBUGLOG(5, "Generating an empty block");
+        assert(outputDirective == notLimited || dstCapacity >= 1);
+        assert(dst != NULL);
+        dst[0] = 0;
+        if (outputDirective == fillOutput) {
+            assert (inputConsumed != NULL);
+            *inputConsumed = 0;
+        }
+        return 1;
+    }
+    assert(src != NULL);
+
+    return LZ4_compress_generic_validated(cctx, src, dst, srcSize,
+                inputConsumed, /* only written into if outputDirective == fillOutput */
+                dstCapacity, outputDirective,
+                tableType, dictDirective, dictIssue, acceleration);
+}
+
+
+int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int inputSize, int maxOutputSize, int acceleration)
+{
+    LZ4_stream_t_internal* const ctx = & LZ4_initStream(state, sizeof(LZ4_stream_t)) -> internal_donotuse;
+    assert(ctx != NULL);
+    if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
+    if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
+    if (maxOutputSize >= LZ4_compressBound(inputSize)) {
+        if (inputSize < LZ4_64Klimit) {
+            return LZ4_compress_generic(ctx, source, dest, inputSize, NULL, 0, notLimited, byU16, noDict, noDictIssue, acceleration);
+        } else {
+            const tableType_t tableType = ((sizeof(void*)==4) && ((uptrval)source > LZ4_DISTANCE_MAX)) ? byPtr : byU32;
+            return LZ4_compress_generic(ctx, source, dest, inputSize, NULL, 0, notLimited, tableType, noDict, noDictIssue, acceleration);
+        }
+    } else {
+        if (inputSize < LZ4_64Klimit) {
+            return LZ4_compress_generic(ctx, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, byU16, noDict, noDictIssue, acceleration);
+        } else {
+            const tableType_t tableType = ((sizeof(void*)==4) && ((uptrval)source > LZ4_DISTANCE_MAX)) ? byPtr : byU32;
+            return LZ4_compress_generic(ctx, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, noDict, noDictIssue, acceleration);
+        }
+    }
+}
+
+/**
+ * LZ4_compress_fast_extState_fastReset() :
+ * A variant of LZ4_compress_fast_extState().
+ *
+ * Using this variant avoids an expensive initialization step. It is only safe
+ * to call if the state buffer is known to be correctly initialized already
+ * (see comment in lz4.h on LZ4_resetStream_fast() for a definition of
+ * "correctly initialized").
+ */
+int LZ4_compress_fast_extState_fastReset(void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration)
+{
+    LZ4_stream_t_internal* const ctx = &((LZ4_stream_t*)state)->internal_donotuse;
+    if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
+    if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
+    assert(ctx != NULL);
+
+    if (dstCapacity >= LZ4_compressBound(srcSize)) {
+        if (srcSize < LZ4_64Klimit) {
+            const tableType_t tableType = byU16;
+            LZ4_prepareTable(ctx, srcSize, tableType);
+            if (ctx->currentOffset) {
+                return LZ4_compress_generic(ctx, src, dst, srcSize, NULL, 0, notLimited, tableType, noDict, dictSmall, acceleration);
+            } else {
+                return LZ4_compress_generic(ctx, src, dst, srcSize, NULL, 0, notLimited, tableType, noDict, noDictIssue, acceleration);
+            }
+        } else {
+            const tableType_t tableType = ((sizeof(void*)==4) && ((uptrval)src > LZ4_DISTANCE_MAX)) ? byPtr : byU32;
+            LZ4_prepareTable(ctx, srcSize, tableType);
+            return LZ4_compress_generic(ctx, src, dst, srcSize, NULL, 0, notLimited, tableType, noDict, noDictIssue, acceleration);
+        }
+    } else {
+        if (srcSize < LZ4_64Klimit) {
+            const tableType_t tableType = byU16;
+            LZ4_prepareTable(ctx, srcSize, tableType);
+            if (ctx->currentOffset) {
+                return LZ4_compress_generic(ctx, src, dst, srcSize, NULL, dstCapacity, limitedOutput, tableType, noDict, dictSmall, acceleration);
+            } else {
+                return LZ4_compress_generic(ctx, src, dst, srcSize, NULL, dstCapacity, limitedOutput, tableType, noDict, noDictIssue, acceleration);
+            }
+        } else {
+            const tableType_t tableType = ((sizeof(void*)==4) && ((uptrval)src > LZ4_DISTANCE_MAX)) ? byPtr : byU32;
+            LZ4_prepareTable(ctx, srcSize, tableType);
+            return LZ4_compress_generic(ctx, src, dst, srcSize, NULL, dstCapacity, limitedOutput, tableType, noDict, noDictIssue, acceleration);
+        }
+    }
+}
+
+
+int LZ4_compress_fast(const char* src, char* dest, int srcSize, int dstCapacity, int acceleration)
+{
+    int result;
+#if (LZ4_HEAPMODE)
+    LZ4_stream_t* const ctxPtr = (LZ4_stream_t*)ALLOC(sizeof(LZ4_stream_t));   /* malloc-calloc always properly aligned */
+    if (ctxPtr == NULL) return 0;
+#else
+    LZ4_stream_t ctx;
+    LZ4_stream_t* const ctxPtr = &ctx;
+#endif
+    result = LZ4_compress_fast_extState(ctxPtr, src, dest, srcSize, dstCapacity, acceleration);
+
+#if (LZ4_HEAPMODE)
+    FREEMEM(ctxPtr);
+#endif
+    return result;
+}
+
+
+int LZ4_compress_default(const char* src, char* dst, int srcSize, int dstCapacity)
+{
+    return LZ4_compress_fast(src, dst, srcSize, dstCapacity, 1);
+}
+
+
+/* Note!: This function leaves the stream in an unclean/broken state!
+ * It is not safe to subsequently use the same state with a _fastReset() or
+ * _continue() call without resetting it. */
+static int LZ4_compress_destSize_extState_internal(LZ4_stream_t* state, const char* src, char* dst, int* srcSizePtr, int targetDstSize, int acceleration)
+{
+    void* const s = LZ4_initStream(state, sizeof (*state));
+    assert(s != NULL); (void)s;
+
+    if (targetDstSize >= LZ4_compressBound(*srcSizePtr)) {  /* compression success is guaranteed */
+        return LZ4_compress_fast_extState(state, src, dst, *srcSizePtr, targetDstSize, acceleration);
+    } else {
+        if (*srcSizePtr < LZ4_64Klimit) {
+            return LZ4_compress_generic(&state->internal_donotuse, src, dst, *srcSizePtr, srcSizePtr, targetDstSize, fillOutput, byU16, noDict, noDictIssue, acceleration);
+        } else {
+            tableType_t const addrMode = ((sizeof(void*)==4) && ((uptrval)src > LZ4_DISTANCE_MAX)) ? byPtr : byU32;
+            return LZ4_compress_generic(&state->internal_donotuse, src, dst, *srcSizePtr, srcSizePtr, targetDstSize, fillOutput, addrMode, noDict, noDictIssue, acceleration);
+    }   }
+}
+
+int LZ4_compress_destSize_extState(void* state, const char* src, char* dst, int* srcSizePtr, int targetDstSize, int acceleration)
+{
+    int const r = LZ4_compress_destSize_extState_internal((LZ4_stream_t*)state, src, dst, srcSizePtr, targetDstSize, acceleration);
+    /* clean the state on exit */
+    LZ4_initStream(state, sizeof (LZ4_stream_t));
+    return r;
+}
+
+
+int LZ4_compress_destSize(const char* src, char* dst, int* srcSizePtr, int targetDstSize)
+{
+#if (LZ4_HEAPMODE)
+    LZ4_stream_t* const ctx = (LZ4_stream_t*)ALLOC(sizeof(LZ4_stream_t));   /* malloc-calloc always properly aligned */
+    if (ctx == NULL) return 0;
+#else
+    LZ4_stream_t ctxBody;
+    LZ4_stream_t* const ctx = &ctxBody;
+#endif
+
+    int result = LZ4_compress_destSize_extState_internal(ctx, src, dst, srcSizePtr, targetDstSize, 1);
+
+#if (LZ4_HEAPMODE)
+    FREEMEM(ctx);
+#endif
+    return result;
+}
+
+
+
+/*-******************************
+*  Streaming functions
+********************************/
+
+#if !defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION)
+LZ4_stream_t* LZ4_createStream(void)
+{
+    LZ4_stream_t* const lz4s = (LZ4_stream_t*)ALLOC(sizeof(LZ4_stream_t));
+    LZ4_STATIC_ASSERT(sizeof(LZ4_stream_t) >= sizeof(LZ4_stream_t_internal));
+    DEBUGLOG(4, "LZ4_createStream %p", lz4s);
+    if (lz4s == NULL) return NULL;
+    LZ4_initStream(lz4s, sizeof(*lz4s));
+    return lz4s;
+}
+#endif
+
+static size_t LZ4_stream_t_alignment(void)
+{
+#if LZ4_ALIGN_TEST
+    typedef struct { char c; LZ4_stream_t t; } t_a;
+    return sizeof(t_a) - sizeof(LZ4_stream_t);
+#else
+    return 1;  /* effectively disabled */
+#endif
+}
+
+LZ4_stream_t* LZ4_initStream (void* buffer, size_t size)
+{
+    DEBUGLOG(5, "LZ4_initStream");
+    if (buffer == NULL) { return NULL; }
+    if (size < sizeof(LZ4_stream_t)) { return NULL; }
+    if (!LZ4_isAligned(buffer, LZ4_stream_t_alignment())) return NULL;
+    MEM_INIT(buffer, 0, sizeof(LZ4_stream_t_internal));
+    return (LZ4_stream_t*)buffer;
+}
+
+/* resetStream is now deprecated,
+ * prefer initStream() which is more general */
+void LZ4_resetStream (LZ4_stream_t* LZ4_stream)
+{
+    DEBUGLOG(5, "LZ4_resetStream (ctx:%p)", LZ4_stream);
+    MEM_INIT(LZ4_stream, 0, sizeof(LZ4_stream_t_internal));
+}
+
+void LZ4_resetStream_fast(LZ4_stream_t* ctx) {
+    LZ4_prepareTable(&(ctx->internal_donotuse), 0, byU32);
+}
+
+#if !defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION)
+int LZ4_freeStream (LZ4_stream_t* LZ4_stream)
+{
+    if (!LZ4_stream) return 0;   /* support free on NULL */
+    DEBUGLOG(5, "LZ4_freeStream %p", LZ4_stream);
+    FREEMEM(LZ4_stream);
+    return (0);
+}
+#endif
+
+
+typedef enum { _ld_fast, _ld_slow } LoadDict_mode_e;
+#define HASH_UNIT sizeof(reg_t)
+int LZ4_loadDict_internal(LZ4_stream_t* LZ4_dict,
+                    const char* dictionary, int dictSize,
+                    LoadDict_mode_e _ld)
+{
+    LZ4_stream_t_internal* const dict = &LZ4_dict->internal_donotuse;
+    const tableType_t tableType = byU32;
+    const BYTE* p = (const BYTE*)dictionary;
+    const BYTE* const dictEnd = p + dictSize;
+    U32 idx32;
+
+    DEBUGLOG(4, "LZ4_loadDict (%i bytes from %p into %p)", dictSize, dictionary, LZ4_dict);
+
+    /* It's necessary to reset the context,
+     * and not just continue it with prepareTable()
+     * to avoid any risk of generating overflowing matchIndex
+     * when compressing using this dictionary */
+    LZ4_resetStream(LZ4_dict);
+
+    /* We always increment the offset by 64 KB, since, if the dict is longer,
+     * we truncate it to the last 64k, and if it's shorter, we still want to
+     * advance by a whole window length so we can provide the guarantee that
+     * there are only valid offsets in the window, which allows an optimization
+     * in LZ4_compress_fast_continue() where it uses noDictIssue even when the
+     * dictionary isn't a full 64k. */
+    dict->currentOffset += 64 KB;
+
+    if (dictSize < (int)HASH_UNIT) {
+        return 0;
+    }
+
+    if ((dictEnd - p) > 64 KB) p = dictEnd - 64 KB;
+    dict->dictionary = p;
+    dict->dictSize = (U32)(dictEnd - p);
+    dict->tableType = (U32)tableType;
+    idx32 = dict->currentOffset - dict->dictSize;
+
+    while (p <= dictEnd-HASH_UNIT) {
+        U32 const h = LZ4_hashPosition(p, tableType);
+        /* Note: overwriting => favors positions end of dictionary */
+        LZ4_putIndexOnHash(idx32, h, dict->hashTable, tableType);
+        p+=3; idx32+=3;
+    }
+
+    if (_ld == _ld_slow) {
+        /* Fill hash table with additional references, to improve compression capability */
+        p = dict->dictionary;
+        idx32 = dict->currentOffset - dict->dictSize;
+        while (p <= dictEnd-HASH_UNIT) {
+            U32 const h = LZ4_hashPosition(p, tableType);
+            U32 const limit = dict->currentOffset - 64 KB;
+            if (LZ4_getIndexOnHash(h, dict->hashTable, tableType) <= limit) {
+                /* Note: not overwriting => favors positions beginning of dictionary */
+                LZ4_putIndexOnHash(idx32, h, dict->hashTable, tableType);
+            }
+            p++; idx32++;
+        }
+    }
+
+    return (int)dict->dictSize;
+}
+
+int LZ4_loadDict(LZ4_stream_t* LZ4_dict, const char* dictionary, int dictSize)
+{
+    return LZ4_loadDict_internal(LZ4_dict, dictionary, dictSize, _ld_fast);
+}
+
+int LZ4_loadDictSlow(LZ4_stream_t* LZ4_dict, const char* dictionary, int dictSize)
+{
+    return LZ4_loadDict_internal(LZ4_dict, dictionary, dictSize, _ld_slow);
+}
+
+void LZ4_attach_dictionary(LZ4_stream_t* workingStream, const LZ4_stream_t* dictionaryStream)
+{
+    const LZ4_stream_t_internal* dictCtx = (dictionaryStream == NULL) ? NULL :
+        &(dictionaryStream->internal_donotuse);
+
+    DEBUGLOG(4, "LZ4_attach_dictionary (%p, %p, size %u)",
+             workingStream, dictionaryStream,
+             dictCtx != NULL ? dictCtx->dictSize : 0);
+
+    if (dictCtx != NULL) {
+        /* If the current offset is zero, we will never look in the
+         * external dictionary context, since there is no value a table
+         * entry can take that indicate a miss. In that case, we need
+         * to bump the offset to something non-zero.
+         */
+        if (workingStream->internal_donotuse.currentOffset == 0) {
+            workingStream->internal_donotuse.currentOffset = 64 KB;
+        }
+
+        /* Don't actually attach an empty dictionary.
+         */
+        if (dictCtx->dictSize == 0) {
+            dictCtx = NULL;
+        }
+    }
+    workingStream->internal_donotuse.dictCtx = dictCtx;
+}
+
+
+static void LZ4_renormDictT(LZ4_stream_t_internal* LZ4_dict, int nextSize)
+{
+    assert(nextSize >= 0);
+    if (LZ4_dict->currentOffset + (unsigned)nextSize > 0x80000000) {   /* potential ptrdiff_t overflow (32-bits mode) */
+        /* rescale hash table */
+        U32 const delta = LZ4_dict->currentOffset - 64 KB;
+        const BYTE* dictEnd = LZ4_dict->dictionary + LZ4_dict->dictSize;
+        int i;
+        DEBUGLOG(4, "LZ4_renormDictT");
+        for (i=0; i<LZ4_HASH_SIZE_U32; i++) {
+            if (LZ4_dict->hashTable[i] < delta) LZ4_dict->hashTable[i]=0;
+            else LZ4_dict->hashTable[i] -= delta;
+        }
+        LZ4_dict->currentOffset = 64 KB;
+        if (LZ4_dict->dictSize > 64 KB) LZ4_dict->dictSize = 64 KB;
+        LZ4_dict->dictionary = dictEnd - LZ4_dict->dictSize;
+    }
+}
+
+
+int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream,
+                                const char* source, char* dest,
+                                int inputSize, int maxOutputSize,
+                                int acceleration)
+{
+    const tableType_t tableType = byU32;
+    LZ4_stream_t_internal* const streamPtr = &LZ4_stream->internal_donotuse;
+    const char* dictEnd = streamPtr->dictSize ? (const char*)streamPtr->dictionary + streamPtr->dictSize : NULL;
+
+    DEBUGLOG(5, "LZ4_compress_fast_continue (inputSize=%i, dictSize=%u)", inputSize, streamPtr->dictSize);
+
+    LZ4_renormDictT(streamPtr, inputSize);   /* fix index overflow */
+    if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
+    if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
+
+    /* invalidate tiny dictionaries */
+    if ( (streamPtr->dictSize < 4)     /* tiny dictionary : not enough for a hash */
+      && (dictEnd != source)           /* prefix mode */
+      && (inputSize > 0)               /* tolerance : don't lose history, in case next invocation would use prefix mode */
+      && (streamPtr->dictCtx == NULL)  /* usingDictCtx */
+      ) {
+        DEBUGLOG(5, "LZ4_compress_fast_continue: dictSize(%u) at addr:%p is too small", streamPtr->dictSize, streamPtr->dictionary);
+        /* remove dictionary existence from history, to employ faster prefix mode */
+        streamPtr->dictSize = 0;
+        streamPtr->dictionary = (const BYTE*)source;
+        dictEnd = source;
+    }
+
+    /* Check overlapping input/dictionary space */
+    {   const char* const sourceEnd = source + inputSize;
+        if ((sourceEnd > (const char*)streamPtr->dictionary) && (sourceEnd < dictEnd)) {
+            streamPtr->dictSize = (U32)(dictEnd - sourceEnd);
+            if (streamPtr->dictSize > 64 KB) streamPtr->dictSize = 64 KB;
+            if (streamPtr->dictSize < 4) streamPtr->dictSize = 0;
+            streamPtr->dictionary = (const BYTE*)dictEnd - streamPtr->dictSize;
+        }
+    }
+
+    /* prefix mode : source data follows dictionary */
+    if (dictEnd == source) {
+        if ((streamPtr->dictSize < 64 KB) && (streamPtr->dictSize < streamPtr->currentOffset))
+            return LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, withPrefix64k, dictSmall, acceleration);
+        else
+            return LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, withPrefix64k, noDictIssue, acceleration);
+    }
+
+    /* external dictionary mode */
+    {   int result;
+        if (streamPtr->dictCtx) {
+            /* We depend here on the fact that dictCtx'es (produced by
+             * LZ4_loadDict) guarantee that their tables contain no references
+             * to offsets between dictCtx->currentOffset - 64 KB and
+             * dictCtx->currentOffset - dictCtx->dictSize. This makes it safe
+             * to use noDictIssue even when the dict isn't a full 64 KB.
+             */
+            if (inputSize > 4 KB) {
+                /* For compressing large blobs, it is faster to pay the setup
+                 * cost to copy the dictionary's tables into the active context,
+                 * so that the compression loop is only looking into one table.
+                 */
+                LZ4_memcpy(streamPtr, streamPtr->dictCtx, sizeof(*streamPtr));
+                result = LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, usingExtDict, noDictIssue, acceleration);
+            } else {
+                result = LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, usingDictCtx, noDictIssue, acceleration);
+            }
+        } else {  /* small data <= 4 KB */
+            if ((streamPtr->dictSize < 64 KB) && (streamPtr->dictSize < streamPtr->currentOffset)) {
+                result = LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, usingExtDict, dictSmall, acceleration);
+            } else {
+                result = LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, usingExtDict, noDictIssue, acceleration);
+            }
+        }
+        streamPtr->dictionary = (const BYTE*)source;
+        streamPtr->dictSize = (U32)inputSize;
+        return result;
+    }
+}
+
+
+/* Hidden debug function, to force-test external dictionary mode */
+int LZ4_compress_forceExtDict (LZ4_stream_t* LZ4_dict, const char* source, char* dest, int srcSize)
+{
+    LZ4_stream_t_internal* const streamPtr = &LZ4_dict->internal_donotuse;
+    int result;
+
+    LZ4_renormDictT(streamPtr, srcSize);
+
+    if ((streamPtr->dictSize < 64 KB) && (streamPtr->dictSize < streamPtr->currentOffset)) {
+        result = LZ4_compress_generic(streamPtr, source, dest, srcSize, NULL, 0, notLimited, byU32, usingExtDict, dictSmall, 1);
+    } else {
+        result = LZ4_compress_generic(streamPtr, source, dest, srcSize, NULL, 0, notLimited, byU32, usingExtDict, noDictIssue, 1);
+    }
+
+    streamPtr->dictionary = (const BYTE*)source;
+    streamPtr->dictSize = (U32)srcSize;
+
+    return result;
+}
+
+
+/*! LZ4_saveDict() :
+ *  If previously compressed data block is not guaranteed to remain available at its memory location,
+ *  save it into a safer place (char* safeBuffer).
+ *  Note : no need to call LZ4_loadDict() afterwards, dictionary is immediately usable,
+ *         one can therefore call LZ4_compress_fast_continue() right after.
+ * @return : saved dictionary size in bytes (necessarily <= dictSize), or 0 if error.
+ */
+int LZ4_saveDict (LZ4_stream_t* LZ4_dict, char* safeBuffer, int dictSize)
+{
+    LZ4_stream_t_internal* const dict = &LZ4_dict->internal_donotuse;
+
+    DEBUGLOG(5, "LZ4_saveDict : dictSize=%i, safeBuffer=%p", dictSize, safeBuffer);
+
+    if ((U32)dictSize > 64 KB) { dictSize = 64 KB; } /* useless to define a dictionary > 64 KB */
+    if ((U32)dictSize > dict->dictSize) { dictSize = (int)dict->dictSize; }
+
+    if (safeBuffer == NULL) assert(dictSize == 0);
+    if (dictSize > 0) {
+        const BYTE* const previousDictEnd = dict->dictionary + dict->dictSize;
+        assert(dict->dictionary);
+        LZ4_memmove(safeBuffer, previousDictEnd - dictSize, (size_t)dictSize);
+    }
+
+    dict->dictionary = (const BYTE*)safeBuffer;
+    dict->dictSize = (U32)dictSize;
+
+    return dictSize;
+}
+
+
+
+/*-*******************************
+ *  Decompression functions
+ ********************************/
+
+typedef enum { decode_full_block = 0, partial_decode = 1 } earlyEnd_directive;
+
+#undef MIN
+#define MIN(a,b)    ( (a) < (b) ? (a) : (b) )
+
+
+/* variant for decompress_unsafe()
+ * does not know end of input
+ * presumes input is well formed
+ * note : will consume at least one byte */
+static size_t read_long_length_no_check(const BYTE** pp)
+{
+    size_t b, l = 0;
+    do { b = **pp; (*pp)++; l += b; } while (b==255);
+    DEBUGLOG(6, "read_long_length_no_check: +length=%zu using %zu input bytes", l, l/255 + 1)
+    return l;
+}
+
+/* core decoder variant for LZ4_decompress_fast*()
+ * for legacy support only : these entry points are deprecated.
+ * - Presumes input is correctly formed (no defense vs malformed inputs)
+ * - Does not know input size (presume input buffer is "large enough")
+ * - Decompress a full block (only)
+ * @return : nb of bytes read from input.
+ * Note : this variant is not optimized for speed, just for maintenance.
+ *        the goal is to remove support of decompress_fast*() variants by v2.0
+**/
+LZ4_FORCE_INLINE int
+LZ4_decompress_unsafe_generic(
+                 const BYTE* const istart,
+                 BYTE* const ostart,
+                 int decompressedSize,
+
+                 size_t prefixSize,
+                 const BYTE* const dictStart,  /* only if dict==usingExtDict */
+                 const size_t dictSize         /* note: =0 if dictStart==NULL */
+                 )
+{
+    const BYTE* ip = istart;
+    BYTE* op = (BYTE*)ostart;
+    BYTE* const oend = ostart + decompressedSize;
+    const BYTE* const prefixStart = ostart - prefixSize;
+
+    DEBUGLOG(5, "LZ4_decompress_unsafe_generic");
+    if (dictStart == NULL) assert(dictSize == 0);
+
+    while (1) {
+        /* start new sequence */
+        unsigned token = *ip++;
+
+        /* literals */
+        {   size_t ll = token >> ML_BITS;
+            if (ll==15) {
+                /* long literal length */
+                ll += read_long_length_no_check(&ip);
+            }
+            if ((size_t)(oend-op) < ll) return -1; /* output buffer overflow */
+            LZ4_memmove(op, ip, ll); /* support in-place decompression */
+            op += ll;
+            ip += ll;
+            if ((size_t)(oend-op) < MFLIMIT) {
+                if (op==oend) break;  /* end of block */
+                DEBUGLOG(5, "invalid: literals end at distance %zi from end of block", oend-op);
+                /* incorrect end of block :
+                 * last match must start at least MFLIMIT==12 bytes before end of output block */
+                return -1;
+        }   }
+
+        /* match */
+        {   size_t ml = token & 15;
+            size_t const offset = LZ4_readLE16(ip);
+            ip+=2;
+
+            if (ml==15) {
+                /* long literal length */
+                ml += read_long_length_no_check(&ip);
+            }
+            ml += MINMATCH;
+
+            if ((size_t)(oend-op) < ml) return -1; /* output buffer overflow */
+
+            {   const BYTE* match = op - offset;
+
+                /* out of range */
+                if (offset > (size_t)(op - prefixStart) + dictSize) {
+                    DEBUGLOG(6, "offset out of range");
+                    return -1;
+                }
+
+                /* check special case : extDict */
+                if (offset > (size_t)(op - prefixStart)) {
+                    /* extDict scenario */
+                    const BYTE* const dictEnd = dictStart + dictSize;
+                    const BYTE* extMatch = dictEnd - (offset - (size_t)(op-prefixStart));
+                    size_t const extml = (size_t)(dictEnd - extMatch);
+                    if (extml > ml) {
+                        /* match entirely within extDict */
+                        LZ4_memmove(op, extMatch, ml);
+                        op += ml;
+                        ml = 0;
+                    } else {
+                        /* match split between extDict & prefix */
+                        LZ4_memmove(op, extMatch, extml);
+                        op += extml;
+                        ml -= extml;
+                    }
+                    match = prefixStart;
+                }
+
+                /* match copy - slow variant, supporting overlap copy */
+                {   size_t u;
+                    for (u=0; u<ml; u++) {
+                        op[u] = match[u];
+            }   }   }
+            op += ml;
+            if ((size_t)(oend-op) < LASTLITERALS) {
+                DEBUGLOG(5, "invalid: match ends at distance %zi from end of block", oend-op);
+                /* incorrect end of block :
+                 * last match must stop at least LASTLITERALS==5 bytes before end of output block */
+                return -1;
+            }
+        } /* match */
+    } /* main loop */
+    return (int)(ip - istart);
+}
+
+
+/* Read the variable-length literal or match length.
+ *
+ * @ip : input pointer
+ * @ilimit : position after which if length is not decoded, the input is necessarily corrupted.
+ * @initial_check - check ip >= ipmax before start of loop.  Returns initial_error if so.
+ * @error (output) - error code.  Must be set to 0 before call.
+**/
+typedef size_t Rvl_t;
+static const Rvl_t rvl_error = (Rvl_t)(-1);
+LZ4_FORCE_INLINE Rvl_t
+read_variable_length(const BYTE** ip, const BYTE* ilimit,
+                     int initial_check)
+{
+    Rvl_t s, length = 0;
+    assert(ip != NULL);
+    assert(*ip !=  NULL);
+    assert(ilimit != NULL);
+    if (initial_check && unlikely((*ip) >= ilimit)) {    /* read limit reached */
+        return rvl_error;
+    }
+    s = **ip;
+    (*ip)++;
+    length += s;
+    if (unlikely((*ip) > ilimit)) {    /* read limit reached */
+        return rvl_error;
+    }
+    /* accumulator overflow detection (32-bit mode only) */
+    if ((sizeof(length) < 8) && unlikely(length > ((Rvl_t)(-1)/2)) ) {
+        return rvl_error;
+    }
+    if (likely(s != 255)) return length;
+    do {
+        s = **ip;
+        (*ip)++;
+        length += s;
+        if (unlikely((*ip) > ilimit)) {    /* read limit reached */
+            return rvl_error;
+        }
+        /* accumulator overflow detection (32-bit mode only) */
+        if ((sizeof(length) < 8) && unlikely(length > ((Rvl_t)(-1)/2)) ) {
+            return rvl_error;
+        }
+    } while (s == 255);
+
+    return length;
+}
+
+/*! LZ4_decompress_generic() :
+ *  This generic decompression function covers all use cases.
+ *  It shall be instantiated several times, using different sets of directives.
+ *  Note that it is important for performance that this function really get inlined,
+ *  in order to remove useless branches during compilation optimization.
+ */
+LZ4_FORCE_INLINE int
+LZ4_decompress_generic(
+                 const char* const src,
+                 char* const dst,
+                 int srcSize,
+                 int outputSize,         /* If endOnInput==endOnInputSize, this value is `dstCapacity` */
+
+                 earlyEnd_directive partialDecoding,  /* full, partial */
+                 dict_directive dict,                 /* noDict, withPrefix64k, usingExtDict */
+                 const BYTE* const lowPrefix,  /* always <= dst, == dst when no prefix */
+                 const BYTE* const dictStart,  /* only if dict==usingExtDict */
+                 const size_t dictSize         /* note : = 0 if noDict */
+                 )
+{
+    if ((src == NULL) || (outputSize < 0)) { return -1; }
+
+    {   const BYTE* ip = (const BYTE*) src;
+        const BYTE* const iend = ip + srcSize;
+
+        BYTE* op = (BYTE*) dst;
+        BYTE* const oend = op + outputSize;
+        BYTE* cpy;
+
+        const BYTE* const dictEnd = (dictStart == NULL) ? NULL : dictStart + dictSize;
+
+        const int checkOffset = (dictSize < (int)(64 KB));
+
+
+        /* Set up the "end" pointers for the shortcut. */
+        const BYTE* const shortiend = iend - 14 /*maxLL*/ - 2 /*offset*/;
+        const BYTE* const shortoend = oend - 14 /*maxLL*/ - 18 /*maxML*/;
+
+        const BYTE* match;
+        size_t offset;
+        unsigned token;
+        size_t length;
+
+
+        DEBUGLOG(5, "LZ4_decompress_generic (srcSize:%i, dstSize:%i)", srcSize, outputSize);
+
+        /* Special cases */
+        assert(lowPrefix <= op);
+        if (unlikely(outputSize==0)) {
+            /* Empty output buffer */
+            if (partialDecoding) return 0;
+            return ((srcSize==1) && (*ip==0)) ? 0 : -1;
+        }
+        if (unlikely(srcSize==0)) { return -1; }
+
+    /* LZ4_FAST_DEC_LOOP:
+     * designed for modern OoO performance cpus,
+     * where copying reliably 32-bytes is preferable to an unpredictable branch.
+     * note : fast loop may show a regression for some client arm chips. */
+#if LZ4_FAST_DEC_LOOP
+        if ((oend - op) < FASTLOOP_SAFE_DISTANCE) {
+            DEBUGLOG(6, "move to safe decode loop");
+            goto safe_decode;
+        }
+
+        /* Fast loop : decode sequences as long as output < oend-FASTLOOP_SAFE_DISTANCE */
+        DEBUGLOG(6, "using fast decode loop");
+        while (1) {
+            /* Main fastloop assertion: We can always wildcopy FASTLOOP_SAFE_DISTANCE */
+            assert(oend - op >= FASTLOOP_SAFE_DISTANCE);
+            assert(ip < iend);
+            token = *ip++;
+            length = token >> ML_BITS;  /* literal length */
+            DEBUGLOG(7, "blockPos%6u: litLength token = %u", (unsigned)(op-(BYTE*)dst), (unsigned)length);
+
+            /* decode literal length */
+            if (length == RUN_MASK) {
+                size_t const addl = read_variable_length(&ip, iend-RUN_MASK, 1);
+                if (addl == rvl_error) {
+                    DEBUGLOG(6, "error reading long literal length");
+                    goto _output_error;
+                }
+                length += addl;
+                if (unlikely((uptrval)(op)+length<(uptrval)(op))) { goto _output_error; } /* overflow detection */
+                if (unlikely((uptrval)(ip)+length<(uptrval)(ip))) { goto _output_error; } /* overflow detection */
+
+                /* copy literals */
+                LZ4_STATIC_ASSERT(MFLIMIT >= WILDCOPYLENGTH);
+                if ((op+length>oend-32) || (ip+length>iend-32)) { goto safe_literal_copy; }
+                LZ4_wildCopy32(op, ip, op+length);
+                ip += length; op += length;
+            } else if (ip <= iend-(16 + 1/*max lit + offset + nextToken*/)) {
+                /* We don't need to check oend, since we check it once for each loop below */
+                DEBUGLOG(7, "copy %u bytes in a 16-bytes stripe", (unsigned)length);
+                /* Literals can only be <= 14, but hope compilers optimize better when copy by a register size */
+                LZ4_memcpy(op, ip, 16);
+                ip += length; op += length;
+            } else {
+                goto safe_literal_copy;
+            }
+
+            /* get offset */
+            offset = LZ4_readLE16(ip); ip+=2;
+            DEBUGLOG(6, "blockPos%6u: offset = %u", (unsigned)(op-(BYTE*)dst), (unsigned)offset);
+            match = op - offset;
+            assert(match <= op);  /* overflow check */
+
+            /* get matchlength */
+            length = token & ML_MASK;
+            DEBUGLOG(7, "  match length token = %u (len==%u)", (unsigned)length, (unsigned)length+MINMATCH);
+
+            if (length == ML_MASK) {
+                size_t const addl = read_variable_length(&ip, iend - LASTLITERALS + 1, 0);
+                if (addl == rvl_error) {
+                    DEBUGLOG(5, "error reading long match length");
+                    goto _output_error;
+                }
+                length += addl;
+                length += MINMATCH;
+                DEBUGLOG(7, "  long match length == %u", (unsigned)length);
+                if (unlikely((uptrval)(op)+length<(uptrval)op)) { goto _output_error; } /* overflow detection */
+                if (op + length >= oend - FASTLOOP_SAFE_DISTANCE) {
+                    goto safe_match_copy;
+                }
+            } else {
+                length += MINMATCH;
+                if (op + length >= oend - FASTLOOP_SAFE_DISTANCE) {
+                    DEBUGLOG(7, "moving to safe_match_copy (ml==%u)", (unsigned)length);
+                    goto safe_match_copy;
+                }
+
+                /* Fastpath check: skip LZ4_wildCopy32 when true */
+                if ((dict == withPrefix64k) || (match >= lowPrefix)) {
+                    if (offset >= 8) {
+                        assert(match >= lowPrefix);
+                        assert(match <= op);
+                        assert(op + 18 <= oend);
+
+                        LZ4_memcpy(op, match, 8);
+                        LZ4_memcpy(op+8, match+8, 8);
+                        LZ4_memcpy(op+16, match+16, 2);
+                        op += length;
+                        continue;
+            }   }   }
+
+            if ( checkOffset && (unlikely(match + dictSize < lowPrefix)) ) {
+                DEBUGLOG(5, "Error : pos=%zi, offset=%zi => outside buffers", op-lowPrefix, op-match);
+                goto _output_error;
+            }
+            /* match starting within external dictionary */
+            if ((dict==usingExtDict) && (match < lowPrefix)) {
+                assert(dictEnd != NULL);
+                if (unlikely(op+length > oend-LASTLITERALS)) {
+                    if (partialDecoding) {
+                        DEBUGLOG(7, "partialDecoding: dictionary match, close to dstEnd");
+                        length = MIN(length, (size_t)(oend-op));
+                    } else {
+                        DEBUGLOG(6, "end-of-block condition violated")
+                        goto _output_error;
+                }   }
+
+                if (length <= (size_t)(lowPrefix-match)) {
+                    /* match fits entirely within external dictionary : just copy */
+                    LZ4_memmove(op, dictEnd - (lowPrefix-match), length);
+                    op += length;
+                } else {
+                    /* match stretches into both external dictionary and current block */
+                    size_t const copySize = (size_t)(lowPrefix - match);
+                    size_t const restSize = length - copySize;
+                    LZ4_memcpy(op, dictEnd - copySize, copySize);
+                    op += copySize;
+                    if (restSize > (size_t)(op - lowPrefix)) {  /* overlap copy */
+                        BYTE* const endOfMatch = op + restSize;
+                        const BYTE* copyFrom = lowPrefix;
+                        while (op < endOfMatch) { *op++ = *copyFrom++; }
+                    } else {
+                        LZ4_memcpy(op, lowPrefix, restSize);
+                        op += restSize;
+                }   }
+                continue;
+            }
+
+            /* copy match within block */
+            cpy = op + length;
+
+            assert((op <= oend) && (oend-op >= 32));
+            if (unlikely(offset<16)) {
+                LZ4_memcpy_using_offset(op, match, cpy, offset);
+            } else {
+                LZ4_wildCopy32(op, match, cpy);
+            }
+
+            op = cpy;   /* wildcopy correction */
+        }
+    safe_decode:
+#endif
+
+        /* Main Loop : decode remaining sequences where output < FASTLOOP_SAFE_DISTANCE */
+        DEBUGLOG(6, "using safe decode loop");
+        while (1) {
+            assert(ip < iend);
+            token = *ip++;
+            length = token >> ML_BITS;  /* literal length */
+            DEBUGLOG(7, "blockPos%6u: litLength token = %u", (unsigned)(op-(BYTE*)dst), (unsigned)length);
+
+            /* A two-stage shortcut for the most common case:
+             * 1) If the literal length is 0..14, and there is enough space,
+             * enter the shortcut and copy 16 bytes on behalf of the literals
+             * (in the fast mode, only 8 bytes can be safely copied this way).
+             * 2) Further if the match length is 4..18, copy 18 bytes in a similar
+             * manner; but we ensure that there's enough space in the output for
+             * those 18 bytes earlier, upon entering the shortcut (in other words,
+             * there is a combined check for both stages).
+             */
+            if ( (length != RUN_MASK)
+                /* strictly "less than" on input, to re-enter the loop with at least one byte */
+              && likely((ip < shortiend) & (op <= shortoend)) ) {
+                /* Copy the literals */
+                LZ4_memcpy(op, ip, 16);
+                op += length; ip += length;
+
+                /* The second stage: prepare for match copying, decode full info.
+                 * If it doesn't work out, the info won't be wasted. */
+                length = token & ML_MASK; /* match length */
+                DEBUGLOG(7, "blockPos%6u: matchLength token = %u (len=%u)", (unsigned)(op-(BYTE*)dst), (unsigned)length, (unsigned)length + 4);
+                offset = LZ4_readLE16(ip); ip += 2;
+                match = op - offset;
+                assert(match <= op); /* check overflow */
+
+                /* Do not deal with overlapping matches. */
+                if ( (length != ML_MASK)
+                  && (offset >= 8)
+                  && (dict==withPrefix64k || match >= lowPrefix) ) {
+                    /* Copy the match. */
+                    LZ4_memcpy(op + 0, match + 0, 8);
+                    LZ4_memcpy(op + 8, match + 8, 8);
+                    LZ4_memcpy(op +16, match +16, 2);
+                    op += length + MINMATCH;
+                    /* Both stages worked, load the next token. */
+                    continue;
+                }
+
+                /* The second stage didn't work out, but the info is ready.
+                 * Propel it right to the point of match copying. */
+                goto _copy_match;
+            }
+
+            /* decode literal length */
+            if (length == RUN_MASK) {
+                size_t const addl = read_variable_length(&ip, iend-RUN_MASK, 1);
+                if (addl == rvl_error) { goto _output_error; }
+                length += addl;
+                if (unlikely((uptrval)(op)+length<(uptrval)(op))) { goto _output_error; } /* overflow detection */
+                if (unlikely((uptrval)(ip)+length<(uptrval)(ip))) { goto _output_error; } /* overflow detection */
+            }
+
+#if LZ4_FAST_DEC_LOOP
+        safe_literal_copy:
+#endif
+            /* copy literals */
+            cpy = op+length;
+
+            LZ4_STATIC_ASSERT(MFLIMIT >= WILDCOPYLENGTH);
+            if ((cpy>oend-MFLIMIT) || (ip+length>iend-(2+1+LASTLITERALS))) {
+                /* We've either hit the input parsing restriction or the output parsing restriction.
+                 * In the normal scenario, decoding a full block, it must be the last sequence,
+                 * otherwise it's an error (invalid input or dimensions).
+                 * In partialDecoding scenario, it's necessary to ensure there is no buffer overflow.
+                 */
+                if (partialDecoding) {
+                    /* Since we are partial decoding we may be in this block because of the output parsing
+                     * restriction, which is not valid since the output buffer is allowed to be undersized.
+                     */
+                    DEBUGLOG(7, "partialDecoding: copying literals, close to input or output end")
+                    DEBUGLOG(7, "partialDecoding: literal length = %u", (unsigned)length);
+                    DEBUGLOG(7, "partialDecoding: remaining space in dstBuffer : %i", (int)(oend - op));
+                    DEBUGLOG(7, "partialDecoding: remaining space in srcBuffer : %i", (int)(iend - ip));
+                    /* Finishing in the middle of a literals segment,
+                     * due to lack of input.
+                     */
+                    if (ip+length > iend) {
+                        length = (size_t)(iend-ip);
+                        cpy = op + length;
+                    }
+                    /* Finishing in the middle of a literals segment,
+                     * due to lack of output space.
+                     */
+                    if (cpy > oend) {
+                        cpy = oend;
+                        assert(op<=oend);
+                        length = (size_t)(oend-op);
+                    }
+                } else {
+                     /* We must be on the last sequence (or invalid) because of the parsing limitations
+                      * so check that we exactly consume the input and don't overrun the output buffer.
+                      */
+                    if ((ip+length != iend) || (cpy > oend)) {
+                        DEBUGLOG(5, "should have been last run of literals")
+                        DEBUGLOG(5, "ip(%p) + length(%i) = %p != iend (%p)", ip, (int)length, ip+length, iend);
+                        DEBUGLOG(5, "or cpy(%p) > (oend-MFLIMIT)(%p)", cpy, oend-MFLIMIT);
+                        DEBUGLOG(5, "after writing %u bytes / %i bytes available", (unsigned)(op-(BYTE*)dst), outputSize);
+                        goto _output_error;
+                    }
+                }
+                LZ4_memmove(op, ip, length);  /* supports overlapping memory regions, for in-place decompression scenarios */
+                ip += length;
+                op += length;
+                /* Necessarily EOF when !partialDecoding.
+                 * When partialDecoding, it is EOF if we've either
+                 * filled the output buffer or
+                 * can't proceed with reading an offset for following match.
+                 */
+                if (!partialDecoding || (cpy == oend) || (ip >= (iend-2))) {
+                    break;
+                }
+            } else {
+                LZ4_wildCopy8(op, ip, cpy);   /* can overwrite up to 8 bytes beyond cpy */
+                ip += length; op = cpy;
+            }
+
+            /* get offset */
+            offset = LZ4_readLE16(ip); ip+=2;
+            match = op - offset;
+
+            /* get matchlength */
+            length = token & ML_MASK;
+            DEBUGLOG(7, "blockPos%6u: matchLength token = %u", (unsigned)(op-(BYTE*)dst), (unsigned)length);
+
+    _copy_match:
+            if (length == ML_MASK) {
+                size_t const addl = read_variable_length(&ip, iend - LASTLITERALS + 1, 0);
+                if (addl == rvl_error) { goto _output_error; }
+                length += addl;
+                if (unlikely((uptrval)(op)+length<(uptrval)op)) goto _output_error;   /* overflow detection */
+            }
+            length += MINMATCH;
+
+#if LZ4_FAST_DEC_LOOP
+        safe_match_copy:
+#endif
+            if ((checkOffset) && (unlikely(match + dictSize < lowPrefix))) goto _output_error;   /* Error : offset outside buffers */
+            /* match starting within external dictionary */
+            if ((dict==usingExtDict) && (match < lowPrefix)) {
+                assert(dictEnd != NULL);
+                if (unlikely(op+length > oend-LASTLITERALS)) {
+                    if (partialDecoding) length = MIN(length, (size_t)(oend-op));
+                    else goto _output_error;   /* doesn't respect parsing restriction */
+                }
+
+                if (length <= (size_t)(lowPrefix-match)) {
+                    /* match fits entirely within external dictionary : just copy */
+                    LZ4_memmove(op, dictEnd - (lowPrefix-match), length);
+                    op += length;
+                } else {
+                    /* match stretches into both external dictionary and current block */
+                    size_t const copySize = (size_t)(lowPrefix - match);
+                    size_t const restSize = length - copySize;
+                    LZ4_memcpy(op, dictEnd - copySize, copySize);
+                    op += copySize;
+                    if (restSize > (size_t)(op - lowPrefix)) {  /* overlap copy */
+                        BYTE* const endOfMatch = op + restSize;
+                        const BYTE* copyFrom = lowPrefix;
+                        while (op < endOfMatch) *op++ = *copyFrom++;
+                    } else {
+                        LZ4_memcpy(op, lowPrefix, restSize);
+                        op += restSize;
+                }   }
+                continue;
+            }
+            assert(match >= lowPrefix);
+
+            /* copy match within block */
+            cpy = op + length;
+
+            /* partialDecoding : may end anywhere within the block */
+            assert(op<=oend);
+            if (partialDecoding && (cpy > oend-MATCH_SAFEGUARD_DISTANCE)) {
+                size_t const mlen = MIN(length, (size_t)(oend-op));
+                const BYTE* const matchEnd = match + mlen;
+                BYTE* const copyEnd = op + mlen;
+                if (matchEnd > op) {   /* overlap copy */
+                    while (op < copyEnd) { *op++ = *match++; }
+                } else {
+                    LZ4_memcpy(op, match, mlen);
+                }
+                op = copyEnd;
+                if (op == oend) { break; }
+                continue;
+            }
+
+            if (unlikely(offset<8)) {
+                LZ4_write32(op, 0);   /* silence msan warning when offset==0 */
+                op[0] = match[0];
+                op[1] = match[1];
+                op[2] = match[2];
+                op[3] = match[3];
+                match += inc32table[offset];
+                LZ4_memcpy(op+4, match, 4);
+                match -= dec64table[offset];
+            } else {
+                LZ4_memcpy(op, match, 8);
+                match += 8;
+            }
+            op += 8;
+
+            if (unlikely(cpy > oend-MATCH_SAFEGUARD_DISTANCE)) {
+                BYTE* const oCopyLimit = oend - (WILDCOPYLENGTH-1);
+                if (cpy > oend-LASTLITERALS) { goto _output_error; } /* Error : last LASTLITERALS bytes must be literals (uncompressed) */
+                if (op < oCopyLimit) {
+                    LZ4_wildCopy8(op, match, oCopyLimit);
+                    match += oCopyLimit - op;
+                    op = oCopyLimit;
+                }
+                while (op < cpy) { *op++ = *match++; }
+            } else {
+                LZ4_memcpy(op, match, 8);
+                if (length > 16) { LZ4_wildCopy8(op+8, match+8, cpy); }
+            }
+            op = cpy;   /* wildcopy correction */
+        }
+
+        /* end of decoding */
+        DEBUGLOG(5, "decoded %i bytes", (int) (((char*)op)-dst));
+        return (int) (((char*)op)-dst);     /* Nb of output bytes decoded */
+
+        /* Overflow error detected */
+    _output_error:
+        return (int) (-(((const char*)ip)-src))-1;
+    }
+}
+
+
+/*===== Instantiate the API decoding functions. =====*/
+
+LZ4_FORCE_O2
+int LZ4_decompress_safe(const char* source, char* dest, int compressedSize, int maxDecompressedSize)
+{
+    return LZ4_decompress_generic(source, dest, compressedSize, maxDecompressedSize,
+                                  decode_full_block, noDict,
+                                  (BYTE*)dest, NULL, 0);
+}
+
+LZ4_FORCE_O2
+int LZ4_decompress_safe_partial(const char* src, char* dst, int compressedSize, int targetOutputSize, int dstCapacity)
+{
+    dstCapacity = MIN(targetOutputSize, dstCapacity);
+    return LZ4_decompress_generic(src, dst, compressedSize, dstCapacity,
+                                  partial_decode,
+                                  noDict, (BYTE*)dst, NULL, 0);
+}
+
+LZ4_FORCE_O2
+int LZ4_decompress_fast(const char* source, char* dest, int originalSize)
+{
+    DEBUGLOG(5, "LZ4_decompress_fast");
+    return LZ4_decompress_unsafe_generic(
+                (const BYTE*)source, (BYTE*)dest, originalSize,
+                0, NULL, 0);
+}
+
+/*===== Instantiate a few more decoding cases, used more than once. =====*/
+
+LZ4_FORCE_O2 /* Exported, an obsolete API function. */
+int LZ4_decompress_safe_withPrefix64k(const char* source, char* dest, int compressedSize, int maxOutputSize)
+{
+    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
+                                  decode_full_block, withPrefix64k,
+                                  (BYTE*)dest - 64 KB, NULL, 0);
+}
+
+LZ4_FORCE_O2
+static int LZ4_decompress_safe_partial_withPrefix64k(const char* source, char* dest, int compressedSize, int targetOutputSize, int dstCapacity)
+{
+    dstCapacity = MIN(targetOutputSize, dstCapacity);
+    return LZ4_decompress_generic(source, dest, compressedSize, dstCapacity,
+                                  partial_decode, withPrefix64k,
+                                  (BYTE*)dest - 64 KB, NULL, 0);
+}
+
+/* Another obsolete API function, paired with the previous one. */
+int LZ4_decompress_fast_withPrefix64k(const char* source, char* dest, int originalSize)
+{
+    return LZ4_decompress_unsafe_generic(
+                (const BYTE*)source, (BYTE*)dest, originalSize,
+                64 KB, NULL, 0);
+}
+
+LZ4_FORCE_O2
+static int LZ4_decompress_safe_withSmallPrefix(const char* source, char* dest, int compressedSize, int maxOutputSize,
+                                               size_t prefixSize)
+{
+    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
+                                  decode_full_block, noDict,
+                                  (BYTE*)dest-prefixSize, NULL, 0);
+}
+
+LZ4_FORCE_O2
+static int LZ4_decompress_safe_partial_withSmallPrefix(const char* source, char* dest, int compressedSize, int targetOutputSize, int dstCapacity,
+                                               size_t prefixSize)
+{
+    dstCapacity = MIN(targetOutputSize, dstCapacity);
+    return LZ4_decompress_generic(source, dest, compressedSize, dstCapacity,
+                                  partial_decode, noDict,
+                                  (BYTE*)dest-prefixSize, NULL, 0);
+}
+
+LZ4_FORCE_O2
+int LZ4_decompress_safe_forceExtDict(const char* source, char* dest,
+                                     int compressedSize, int maxOutputSize,
+                                     const void* dictStart, size_t dictSize)
+{
+    DEBUGLOG(5, "LZ4_decompress_safe_forceExtDict");
+    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
+                                  decode_full_block, usingExtDict,
+                                  (BYTE*)dest, (const BYTE*)dictStart, dictSize);
+}
+
+LZ4_FORCE_O2
+int LZ4_decompress_safe_partial_forceExtDict(const char* source, char* dest,
+                                     int compressedSize, int targetOutputSize, int dstCapacity,
+                                     const void* dictStart, size_t dictSize)
+{
+    dstCapacity = MIN(targetOutputSize, dstCapacity);
+    return LZ4_decompress_generic(source, dest, compressedSize, dstCapacity,
+                                  partial_decode, usingExtDict,
+                                  (BYTE*)dest, (const BYTE*)dictStart, dictSize);
+}
+
+LZ4_FORCE_O2
+static int LZ4_decompress_fast_extDict(const char* source, char* dest, int originalSize,
+                                       const void* dictStart, size_t dictSize)
+{
+    return LZ4_decompress_unsafe_generic(
+                (const BYTE*)source, (BYTE*)dest, originalSize,
+                0, (const BYTE*)dictStart, dictSize);
+}
+
+/* The "double dictionary" mode, for use with e.g. ring buffers: the first part
+ * of the dictionary is passed as prefix, and the second via dictStart + dictSize.
+ * These routines are used only once, in LZ4_decompress_*_continue().
+ */
+LZ4_FORCE_INLINE
+int LZ4_decompress_safe_doubleDict(const char* source, char* dest, int compressedSize, int maxOutputSize,
+                                   size_t prefixSize, const void* dictStart, size_t dictSize)
+{
+    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
+                                  decode_full_block, usingExtDict,
+                                  (BYTE*)dest-prefixSize, (const BYTE*)dictStart, dictSize);
+}
+
+/*===== streaming decompression functions =====*/
+
+#if !defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION)
+LZ4_streamDecode_t* LZ4_createStreamDecode(void)
+{
+    LZ4_STATIC_ASSERT(sizeof(LZ4_streamDecode_t) >= sizeof(LZ4_streamDecode_t_internal));
+    return (LZ4_streamDecode_t*) ALLOC_AND_ZERO(sizeof(LZ4_streamDecode_t));
+}
+
+int LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_stream)
+{
+    if (LZ4_stream == NULL) { return 0; }  /* support free on NULL */
+    FREEMEM(LZ4_stream);
+    return 0;
+}
+#endif
+
+/*! LZ4_setStreamDecode() :
+ *  Use this function to instruct where to find the dictionary.
+ *  This function is not necessary if previous data is still available where it was decoded.
+ *  Loading a size of 0 is allowed (same effect as no dictionary).
+ * @return : 1 if OK, 0 if error
+ */
+int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dictionary, int dictSize)
+{
+    LZ4_streamDecode_t_internal* lz4sd = &LZ4_streamDecode->internal_donotuse;
+    lz4sd->prefixSize = (size_t)dictSize;
+    if (dictSize) {
+        assert(dictionary != NULL);
+        lz4sd->prefixEnd = (const BYTE*) dictionary + dictSize;
+    } else {
+        lz4sd->prefixEnd = (const BYTE*) dictionary;
+    }
+    lz4sd->externalDict = NULL;
+    lz4sd->extDictSize  = 0;
+    return 1;
+}
+
+/*! LZ4_decoderRingBufferSize() :
+ *  when setting a ring buffer for streaming decompression (optional scenario),
+ *  provides the minimum size of this ring buffer
+ *  to be compatible with any source respecting maxBlockSize condition.
+ *  Note : in a ring buffer scenario,
+ *  blocks are presumed decompressed next to each other.
+ *  When not enough space remains for next block (remainingSize < maxBlockSize),
+ *  decoding resumes from beginning of ring buffer.
+ * @return : minimum ring buffer size,
+ *           or 0 if there is an error (invalid maxBlockSize).
+ */
+int LZ4_decoderRingBufferSize(int maxBlockSize)
+{
+    if (maxBlockSize < 0) return 0;
+    if (maxBlockSize > LZ4_MAX_INPUT_SIZE) return 0;
+    if (maxBlockSize < 16) maxBlockSize = 16;
+    return LZ4_DECODER_RING_BUFFER_SIZE(maxBlockSize);
+}
+
+/*
+*_continue() :
+    These decoding functions allow decompression of multiple blocks in "streaming" mode.
+    Previously decoded blocks must still be available at the memory position where they were decoded.
+    If it's not possible, save the relevant part of decoded data into a safe buffer,
+    and indicate where it stands using LZ4_setStreamDecode()
+*/
+LZ4_FORCE_O2
+int LZ4_decompress_safe_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* source, char* dest, int compressedSize, int maxOutputSize)
+{
+    LZ4_streamDecode_t_internal* lz4sd = &LZ4_streamDecode->internal_donotuse;
+    int result;
+
+    if (lz4sd->prefixSize == 0) {
+        /* The first call, no dictionary yet. */
+        assert(lz4sd->extDictSize == 0);
+        result = LZ4_decompress_safe(source, dest, compressedSize, maxOutputSize);
+        if (result <= 0) return result;
+        lz4sd->prefixSize = (size_t)result;
+        lz4sd->prefixEnd = (BYTE*)dest + result;
+    } else if (lz4sd->prefixEnd == (BYTE*)dest) {
+        /* They're rolling the current segment. */
+        if (lz4sd->prefixSize >= 64 KB - 1)
+            result = LZ4_decompress_safe_withPrefix64k(source, dest, compressedSize, maxOutputSize);
+        else if (lz4sd->extDictSize == 0)
+            result = LZ4_decompress_safe_withSmallPrefix(source, dest, compressedSize, maxOutputSize,
+                                                         lz4sd->prefixSize);
+        else
+            result = LZ4_decompress_safe_doubleDict(source, dest, compressedSize, maxOutputSize,
+                                                    lz4sd->prefixSize, lz4sd->externalDict, lz4sd->extDictSize);
+        if (result <= 0) return result;
+        lz4sd->prefixSize += (size_t)result;
+        lz4sd->prefixEnd  += result;
+    } else {
+        /* The buffer wraps around, or they're switching to another buffer. */
+        lz4sd->extDictSize = lz4sd->prefixSize;
+        lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
+        result = LZ4_decompress_safe_forceExtDict(source, dest, compressedSize, maxOutputSize,
+                                                  lz4sd->externalDict, lz4sd->extDictSize);
+        if (result <= 0) return result;
+        lz4sd->prefixSize = (size_t)result;
+        lz4sd->prefixEnd  = (BYTE*)dest + result;
+    }
+
+    return result;
+}
+
+LZ4_FORCE_O2 int
+LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode,
+                        const char* source, char* dest, int originalSize)
+{
+    LZ4_streamDecode_t_internal* const lz4sd =
+        (assert(LZ4_streamDecode!=NULL), &LZ4_streamDecode->internal_donotuse);
+    int result;
+
+    DEBUGLOG(5, "LZ4_decompress_fast_continue (toDecodeSize=%i)", originalSize);
+    assert(originalSize >= 0);
+
+    if (lz4sd->prefixSize == 0) {
+        DEBUGLOG(5, "first invocation : no prefix nor extDict");
+        assert(lz4sd->extDictSize == 0);
+        result = LZ4_decompress_fast(source, dest, originalSize);
+        if (result <= 0) return result;
+        lz4sd->prefixSize = (size_t)originalSize;
+        lz4sd->prefixEnd = (BYTE*)dest + originalSize;
+    } else if (lz4sd->prefixEnd == (BYTE*)dest) {
+        DEBUGLOG(5, "continue using existing prefix");
+        result = LZ4_decompress_unsafe_generic(
+                        (const BYTE*)source, (BYTE*)dest, originalSize,
+                        lz4sd->prefixSize,
+                        lz4sd->externalDict, lz4sd->extDictSize);
+        if (result <= 0) return result;
+        lz4sd->prefixSize += (size_t)originalSize;
+        lz4sd->prefixEnd  += originalSize;
+    } else {
+        DEBUGLOG(5, "prefix becomes extDict");
+        lz4sd->extDictSize = lz4sd->prefixSize;
+        lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
+        result = LZ4_decompress_fast_extDict(source, dest, originalSize,
+                                             lz4sd->externalDict, lz4sd->extDictSize);
+        if (result <= 0) return result;
+        lz4sd->prefixSize = (size_t)originalSize;
+        lz4sd->prefixEnd  = (BYTE*)dest + originalSize;
+    }
+
+    return result;
+}
+
+
+/*
+Advanced decoding functions :
+*_usingDict() :
+    These decoding functions work the same as "_continue" ones,
+    the dictionary must be explicitly provided within parameters
+*/
+
+int LZ4_decompress_safe_usingDict(const char* source, char* dest, int compressedSize, int maxOutputSize, const char* dictStart, int dictSize)
+{
+    if (dictSize==0)
+        return LZ4_decompress_safe(source, dest, compressedSize, maxOutputSize);
+    if (dictStart+dictSize == dest) {
+        if (dictSize >= 64 KB - 1) {
+            return LZ4_decompress_safe_withPrefix64k(source, dest, compressedSize, maxOutputSize);
+        }
+        assert(dictSize >= 0);
+        return LZ4_decompress_safe_withSmallPrefix(source, dest, compressedSize, maxOutputSize, (size_t)dictSize);
+    }
+    assert(dictSize >= 0);
+    return LZ4_decompress_safe_forceExtDict(source, dest, compressedSize, maxOutputSize, dictStart, (size_t)dictSize);
+}
+
+int LZ4_decompress_safe_partial_usingDict(const char* source, char* dest, int compressedSize, int targetOutputSize, int dstCapacity, const char* dictStart, int dictSize)
+{
+    if (dictSize==0)
+        return LZ4_decompress_safe_partial(source, dest, compressedSize, targetOutputSize, dstCapacity);
+    if (dictStart+dictSize == dest) {
+        if (dictSize >= 64 KB - 1) {
+            return LZ4_decompress_safe_partial_withPrefix64k(source, dest, compressedSize, targetOutputSize, dstCapacity);
+        }
+        assert(dictSize >= 0);
+        return LZ4_decompress_safe_partial_withSmallPrefix(source, dest, compressedSize, targetOutputSize, dstCapacity, (size_t)dictSize);
+    }
+    assert(dictSize >= 0);
+    return LZ4_decompress_safe_partial_forceExtDict(source, dest, compressedSize, targetOutputSize, dstCapacity, dictStart, (size_t)dictSize);
+}
+
+int LZ4_decompress_fast_usingDict(const char* source, char* dest, int originalSize, const char* dictStart, int dictSize)
+{
+    if (dictSize==0 || dictStart+dictSize == dest)
+        return LZ4_decompress_unsafe_generic(
+                        (const BYTE*)source, (BYTE*)dest, originalSize,
+                        (size_t)dictSize, NULL, 0);
+    assert(dictSize >= 0);
+    return LZ4_decompress_fast_extDict(source, dest, originalSize, dictStart, (size_t)dictSize);
+}
+
+
+/*=*************************************************
+*  Obsolete Functions
+***************************************************/
+/* obsolete compression functions */
+int LZ4_compress_limitedOutput(const char* source, char* dest, int inputSize, int maxOutputSize)
+{
+    return LZ4_compress_default(source, dest, inputSize, maxOutputSize);
+}
+int LZ4_compress(const char* src, char* dest, int srcSize)
+{
+    return LZ4_compress_default(src, dest, srcSize, LZ4_compressBound(srcSize));
+}
+int LZ4_compress_limitedOutput_withState (void* state, const char* src, char* dst, int srcSize, int dstSize)
+{
+    return LZ4_compress_fast_extState(state, src, dst, srcSize, dstSize, 1);
+}
+int LZ4_compress_withState (void* state, const char* src, char* dst, int srcSize)
+{
+    return LZ4_compress_fast_extState(state, src, dst, srcSize, LZ4_compressBound(srcSize), 1);
+}
+int LZ4_compress_limitedOutput_continue (LZ4_stream_t* LZ4_stream, const char* src, char* dst, int srcSize, int dstCapacity)
+{
+    return LZ4_compress_fast_continue(LZ4_stream, src, dst, srcSize, dstCapacity, 1);
+}
+int LZ4_compress_continue (LZ4_stream_t* LZ4_stream, const char* source, char* dest, int inputSize)
+{
+    return LZ4_compress_fast_continue(LZ4_stream, source, dest, inputSize, LZ4_compressBound(inputSize), 1);
+}
+
+/*
+These decompression functions are deprecated and should no longer be used.
+They are only provided here for compatibility with older user programs.
+- LZ4_uncompress is totally equivalent to LZ4_decompress_fast
+- LZ4_uncompress_unknownOutputSize is totally equivalent to LZ4_decompress_safe
+*/
+int LZ4_uncompress (const char* source, char* dest, int outputSize)
+{
+    return LZ4_decompress_fast(source, dest, outputSize);
+}
+int LZ4_uncompress_unknownOutputSize (const char* source, char* dest, int isize, int maxOutputSize)
+{
+    return LZ4_decompress_safe(source, dest, isize, maxOutputSize);
+}
+
+/* Obsolete Streaming functions */
+
+int LZ4_sizeofStreamState(void) { return sizeof(LZ4_stream_t); }
+
+int LZ4_resetStreamState(void* state, char* inputBuffer)
+{
+    (void)inputBuffer;
+    LZ4_resetStream((LZ4_stream_t*)state);
+    return 0;
+}
+
+#if !defined(LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION)
+void* LZ4_create (char* inputBuffer)
+{
+    (void)inputBuffer;
+    return LZ4_createStream();
+}
+#endif
+
+char* LZ4_slideInputBuffer (void* state)
+{
+    /* avoid const char * -> char * conversion warning */
+    return (char *)(uptrval)((LZ4_stream_t*)state)->internal_donotuse.dictionary;
+}
+
+#endif   /* LZ4_COMMONDEFS_ONLY */
lib/lz4/upstream/lz4.h new file +884 -0

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lib/lz4/upstream/lz4hc.c new file +2192 -0

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lib/lz4/upstream/lz4hc.h new file +414 -0

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2.34.1

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#3 lore raw
Sashiko has reviewed this patch and found no issues. It looks great!
Quoted 7 lines

Add the four upstream files under lib/lz4/upstream/ without modification. Nothing builds them yet; a later patch adds the build environment.

Copied without modification from the v1.10.0 release tag of
https://github.com/lz4/lz4, tagged 2024-07-21.

Sashiko has reviewed this patch and found no issues. It looks great!

Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1
#4 lore raw
In reply to Michal Wilczynski

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

Quoted 4 lines
lib/lz4/upstream/lz4.c new file +4 -0
+#ifndef LZ4_FAST_DEC_LOOP
+#  if defined __i386__ || defined _M_IX86 || defined __x86_64__ || defined _M_X64
+#    define LZ4_FAST_DEC_LOOP 1
+#  elif defined(__aarch64__) && defined(__APPLE__)

lib/lz4/upstream/lz4.c line 491

Quoted 10 lines
lib/lz4/upstream/lz4.c new file +10 -0
+#    define LZ4_FAST_DEC_LOOP 1
+#  elif defined(__aarch64__) && !defined(__clang__)
+     /* On non-Apple aarch64, we disable this optimization for clang because
+      * on certain mobile chipsets, performance is reduced with clang. For
+      * more information refer to https://github.com/lz4/lz4/pull/707 */
+#    define LZ4_FAST_DEC_LOOP 1
+#  else
+#    define LZ4_FAST_DEC_LOOP 0
+#  endif
+#endif

I just checked https://github.com/lz4/lz4/pull/707 and it seems that LZ4_FAST_DEC_LOOP is enabled on aarch64 now, but we still disable it. Am I missing something?

#5 lore raw
Quoted 12 lines · Sergey Senozhatsky

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

Quoted 10 lines
lib/lz4/upstream/lz4.c new file +10 -0
+#ifndef LZ4_FAST_DEC_LOOP
+#  if defined __i386__ || defined _M_IX86 || defined __x86_64__ || defined _M_X64
+#    define LZ4_FAST_DEC_LOOP 1
+#  elif defined(__aarch64__) && defined(__APPLE__)
+#    define LZ4_FAST_DEC_LOOP 1
+#  elif defined(__aarch64__) && !defined(__clang__)
+     /* On non-Apple aarch64, we disable this optimization for clang because
+      * on certain mobile chipsets, performance is reduced with clang. For
+      * more information refer to https://protect2.fireeye.com/v1/url?k=e59d343e-8402d40e-e59cbf71-000babe403ab-24cad800d51083a3&q=1&e=1265adcb-d286-42f9-9d57-b9b998ba2ed0&u=https%3A%2F%2Fgithub.com%2Flz4%2Flz4%2Fpull%2F707 */
+#    define LZ4_FAST_DEC_LOOP 1
Quoted 9 lines

lib/lz4/upstream/lz4.c line 491

Quoted 4 lines
lib/lz4/upstream/lz4.c new file +4 -0
+#  else
+#    define LZ4_FAST_DEC_LOOP 0
+#  endif
+#endif

I just checked https://protect2.fireeye.com/v1/url?k=f36de8be-92f2088e-f36c63f1-000babe403ab-1972efa3caab0762&q=1&e=1265adcb-d286-42f9-9d57-b9b998ba2ed0&u=https%3A%2F%2Fgithub.com%2Flz4%2Flz4%2Fpull%2F707 and it seems that LZ4_FAST_DEC_LOOP is enabled on aarch64 now, but we still disable it.
Am I missing something?

You're right for clang builds. v1.10.0 enables the fast loop on aarch64 only with GCC clang has been excluded since PR you mentioned. Upstream has since changed that neither of those commits is released yet:

0aa33884faf5 ("[LZ4] Limit disabling LZ4_FAST_DEC_LOOP to aarch64+clang+android")

ed86bc1ed802 ("AArch64: Enable LZ4_FAST_DEC_LOOP for Android")

The first is already enough for the kernel.

For v2 I'll backport both commits into the vendored lz4.c the same way patch 2 backports 5ef1f16929b5. They apply cleanly in order and give exactly upstream's current condition, and they go away at the next resync.

Best regards,

Signature · 1 line
Michal Wilczynski <[email protected]>
#6 lore raw
In reply to Michal Wilczynski

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

lib/lz4/upstream/lz4.c line 1385

Quoted 4 lines
lib/lz4/upstream/lz4.c new file +4 -0
+int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int inputSize, int maxOutputSize, int acceleration)
+{
+    LZ4_stream_t_internal* const ctx = & LZ4_initStream(state, sizeof(LZ4_stream_t)) -> internal_donotuse;
+    assert(ctx != NULL);

Probably in some other places as well:

LZ4_initStream() can return NULL, but the code immediately derefs the pointer. The assert() check seems to be misplaced, unless I'm missing something.

I suppose those need to be decoupled. First LZ4_initStream() call and NULL check, then stream->internal_donotuse.

#7 lore raw
Quoted 9 lines · Sergey Senozhatsky

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

lib/lz4/upstream/lz4.c line 1385

Quoted 4 lines
lib/lz4/upstream/lz4.c new file +4 -0
+int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int inputSize, int maxOutputSize, int acceleration)
+{
+    LZ4_stream_t_internal* const ctx = & LZ4_initStream(state, sizeof(LZ4_stream_t)) -> internal_donotuse;
+    assert(ctx != NULL);

Probably in some other places as well:

Quoted 6 lines

LZ4_initStream() can return NULL, but the code immediately derefs the pointer. The assert() check seems to be misplaced, unless I'm missing something.

I suppose those need to be decoupled. First LZ4_initStream() call and NULL check, then stream->internal_donotuse.

Good catch, this assert() is a noop in the kernel (as any build without LZ4_DEBUG), so a NULL, undersized or misaligned wrkmem oopses in LZ4_compress_fast(), and LZ4_compress_destSize() and LZ4_resetStreamHC() carry on with an uninitialised state.

No in-tree caller hits it (all use kmalloc/vmalloc), and I listed the alignment requirement as a behaviour change in the cover letter. Still, the vendored files need to stay verbatim.

So in v2 our own entry points can check alignment with a WARN_ON_ONCE() and bail out early. It might be something that we can fix upstream as well.

Quoted 1 line

Best regards,

Signature · 1 line
Michal Wilczynski <[email protected]>
#8 lore raw
Quoted 14 lines · On Sun, 4 Oct 2026 01:50:39 +0200 Michal Wilczynski <[email protected]>…
Quoted 13 lines · Sergey Senozhatsky

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

lib/lz4/upstream/lz4.c line 1385

Quoted 4 lines
lib/lz4/upstream/lz4.c new file +4 -0
+int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int inputSize, int maxOutputSize, int acceleration)
+{
+    LZ4_stream_t_internal* const ctx = & LZ4_initStream(state, sizeof(LZ4_stream_t)) -> internal_donotuse;
+    assert(ctx != NULL);  

Probably in some other places as well:

LZ4_initStream() can return NULL, but the code immediately derefs the pointer. The assert() check seems to be misplaced, unless I'm missing something.

Quoted 7 lines
Quoted 2 lines

I suppose those need to be decoupled. First LZ4_initStream() call and NULL check, then stream->internal_donotuse.

Good catch, this assert() is a noop in the kernel (as any build without LZ4_DEBUG), so a NULL, undersized or misaligned wrkmem oopses in LZ4_compress_fast(), and LZ4_compress_destSize() and LZ4_resetStreamHC() carry on with an uninitialised state.

The assert() is also just a waste of code. Debugging the NULL pointer dereference is just as easy.

David

Quoted 13 lines

No in-tree caller hits it (all use kmalloc/vmalloc), and I listed the alignment requirement as a behaviour change in the cover letter. Still, the vendored files need to stay verbatim.

So in v2 our own entry points can check alignment with a WARN_ON_ONCE() and bail out early. It might be something that we can fix upstream as well.

Quoted 1 line

Best regards,

#9 lore raw
In reply to Michal Wilczynski

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

Quoted 3 lines
lib/lz4/upstream/lz4.c new file +3 -0
+void LZ4_resetStream_fast(LZ4_stream_t* ctx) {
+    LZ4_prepareTable(&(ctx->internal_donotuse), 0, byU32);
+}

[..]

Quoted 17 lines
lib/lz4/upstream/lz4.c new file +17 -0
+void LZ4_attach_dictionary(LZ4_stream_t* workingStream, const LZ4_stream_t* dictionaryStream)
+{
+    const LZ4_stream_t_internal* dictCtx = (dictionaryStream == NULL) ? NULL :
+        &(dictionaryStream->internal_donotuse);
+
+    DEBUGLOG(4, "LZ4_attach_dictionary (%p, %p, size %u)",
+             workingStream, dictionaryStream,
+             dictCtx != NULL ? dictCtx->dictSize : 0);
+
+    if (dictCtx != NULL) {
+        /* If the current offset is zero, we will never look in the
+         * external dictionary context, since there is no value a table
+         * entry can take that indicate a miss. In that case, we need
+         * to bump the offset to something non-zero.
+         */
+        if (workingStream->internal_donotuse.currentOffset == 0) {
+            workingStream->internal_donotuse.currentOffset = 64 KB;

lib/lz4/upstream/lz4.c line 1684

Quoted 10 lines
lib/lz4/upstream/lz4.c new file +10 -0
+        }
+
+        /* Don't actually attach an empty dictionary.
+         */
+        if (dictCtx->dictSize == 0) {
+            dictCtx = NULL;
+        }
+    }
+    workingStream->internal_donotuse.dictCtx = dictCtx;
+}

Just a side note,
there is a bunch of new helpful API added in this release. Currently, we do some memcpy hacks to avoid re-init of lz4 C/D-dict in zram, but once this series lands I'll be happy to send some trivial EXPORT_SYMBOL patches so that zram (and other lz4 users) can use standard lz4 dict API instead of hacks.

#10 lore raw
Quoted 35 lines · Sergey Senozhatsky

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

Quoted 3 lines
lib/lz4/upstream/lz4.c new file +3 -0
+void LZ4_resetStream_fast(LZ4_stream_t* ctx) {
+    LZ4_prepareTable(&(ctx->internal_donotuse), 0, byU32);
+}

[..]

Quoted 26 lines
lib/lz4/upstream/lz4.c new file +26 -0
+void LZ4_attach_dictionary(LZ4_stream_t* workingStream, const LZ4_stream_t* dictionaryStream)
+{
+    const LZ4_stream_t_internal* dictCtx = (dictionaryStream == NULL) ? NULL :
+        &(dictionaryStream->internal_donotuse);
+
+    DEBUGLOG(4, "LZ4_attach_dictionary (%p, %p, size %u)",
+             workingStream, dictionaryStream,
+             dictCtx != NULL ? dictCtx->dictSize : 0);
+
+    if (dictCtx != NULL) {
+        /* If the current offset is zero, we will never look in the
+         * external dictionary context, since there is no value a table
+         * entry can take that indicate a miss. In that case, we need
+         * to bump the offset to something non-zero.
+         */
+        if (workingStream->internal_donotuse.currentOffset == 0) {
+            workingStream->internal_donotuse.currentOffset = 64 KB;
+        }
+
+        /* Don't actually attach an empty dictionary.
+         */
+        if (dictCtx->dictSize == 0) {
+            dictCtx = NULL;
+        }
+    }
+    workingStream->internal_donotuse.dictCtx = dictCtx;
Quoted 9 lines
Quoted 1 line

+}

Just a side note,
there is a bunch of new helpful API added in this release. Currently, we do some memcpy hacks to avoid re-init of lz4 C/D-dict in zram, but once this series lands I'll be happy to send some trivial EXPORT_SYMBOL patches so that zram (and other lz4 users) can use standard lz4 dict API instead of hacks.

Sounds great, thank you !

Best regards,

Signature · 1 line
Michal Wilczynski <[email protected]>
#11 lore raw

RFC PATCH 2/9 lib/lz4: backport upstream's -Wmissing-prototypes fix

In reply to Michal Wilczynski

v1.10.0 defines LZ4_loadDict_internal() in lz4.c and LZ4HC_searchExtDict() in lz4hc.c with external linkage and no prototype, which the kernel's -Wmissing-prototypes rejects. The first also prevents linking, since lz4_compress.c and lz4_decompress.c both include lz4.c and would each define it.

Neither can be forward declared static in lz4_deps.h like the other bare helpers, because their signatures use types declared inside the .c files.

Take the two hunks of upstream commit 5ef1f16929b5
("fix -Wmissing-prototypes warnings") that apply to the files we vendor. This is the only deviation from the tag, and goes away at the next re-sync.

---
 lib/lz4/upstream/lz4.c   | 2 +-
 lib/lz4/upstream/lz4hc.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
lib/lz4/upstream/lz4.c +1 -1
index a2f7abee19fb9a5c768f2a6c266acf5b571f0855..0d474be0236a698d297ab9a430f5082485eb3709 100644
@@ -1584,7 +1584,7 @@ int LZ4_freeStream (LZ4_stream_t* LZ4_stream)
 
 typedef enum { _ld_fast, _ld_slow } LoadDict_mode_e;
 #define HASH_UNIT sizeof(reg_t)
-int LZ4_loadDict_internal(LZ4_stream_t* LZ4_dict,
+static int LZ4_loadDict_internal(LZ4_stream_t* LZ4_dict,
                     const char* dictionary, int dictSize,
                     LoadDict_mode_e _ld)
 {
lib/lz4/upstream/lz4hc.c +1 -1
index 4d8c36a6978fcae09e4c4a936572b4b271513466..32b29f382268d961d65383b24c7225494d9044ad 100644
@@ -360,7 +360,7 @@ typedef struct {
     int back;  /* negative value */
 } LZ4HC_match_t;
 
-LZ4HC_match_t LZ4HC_searchExtDict(const BYTE* ip, U32 ipIndex,
+static LZ4HC_match_t LZ4HC_searchExtDict(const BYTE* ip, U32 ipIndex,
         const BYTE* const iLowLimit, const BYTE* const iHighLimit,
         const LZ4HC_CCtx_internal* dictCtx, U32 gDictEndIndex,
         int currentBestML, int nbAttempts)
Signature · 1 line
2.34.1
#12 lore raw

Re: [PATCH RFC 2/9] lib/lz4: backport upstream's -Wmissing-prototypes fix

Sashiko has reviewed this patch and found no issues. It looks great!
Quoted 9 lines

v1.10.0 defines LZ4_loadDict_internal() in lz4.c and LZ4HC_searchExtDict() in lz4hc.c with external linkage and no prototype, which the kernel's -Wmissing-prototypes rejects. The first also prevents linking, since lz4_compress.c and lz4_decompress.c both include lz4.c and would each define it.

Neither can be forward declared static in lz4_deps.h like the other bare helpers, because their signatures use types declared inside the .c files.

Quoted 6 lines

Take the two hunks of upstream commit 5ef1f16929b5
("fix -Wmissing-prototypes warnings") that apply to the files we vendor. This is the only deviation from the tag, and goes away at the next re-sync.

Sashiko has reviewed this patch and found no issues. It looks great!

Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2
#13 lore raw

RFC PATCH 3/9 lib/lz4: add the build environment for the vendored sources

In reply to Michal Wilczynski

lz4_deps.h makes the unmodified upstream sources compile in the kernel:
it supplies the ISO C spellings they expect, gives every upstream entry point internal linkage so an object carries only the codec it forwards, keeps every workspace off the stack, and renames the entry points the kernel re-exports with a trailing wrkmem argument.

freestanding/ forwards the four ISO C headers upstream includes (stddef.h, stdint.h, limits.h, string.h) to their <linux/> equivalents.

The vendored functions an object does not forward are unreferenced, so LZ4LIB_VISIBILITY carries __maybe_unused rather than disabling -Wunused-function for a directory. This also covers the pre-boot decompressors, which compile lz4_decompress.c textually and never see lib/lz4's ccflags.

For the same reason this header includes <linux/build_bug.h>: the entry points static_assert upstream's structure sizes, and only some architectures' pre-boot environments have static_assert in scope.

lz4_kernel_api.h undoes the renaming for the entry point files and declares what lib/lz4 exports. It starts out carrying its own copy of those prototypes, because it cannot include <linux/lz4.h> while that header still defines the three stream types upstream's headers also define. A later patch folds it away once they are incomplete.

Nothing includes either header yet.

---
 lib/lz4/freestanding/limits.h | 14 +++++++
 lib/lz4/freestanding/stddef.h | 15 +++++++
 lib/lz4/freestanding/stdint.h | 14 +++++++
 lib/lz4/freestanding/string.h | 14 +++++++
 lib/lz4/lz4_deps.h            | 96 ++++++++++++++++++++++++++++++++++++++++++
 lib/lz4/lz4_kernel_api.h      | 98 +++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 251 insertions(+)
lib/lz4/freestanding/limits.h new file +14 -0
new file mode 100644
index 0000000000000000000000000000000000000000..0d1cafbc77eb5d2f564b51feaa911748446abf60
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2026 Samsung Electronics Co., Ltd.
+ * Author: Michal Wilczynski <[email protected]>
+ *
+ * Freestanding <limits.h> for the vendored upstream LZ4 sources; lz4.c needs
+ * UINT_MAX and lz4hc.c needs INT_MAX.
+ */
+#ifndef __LZ4_FREESTANDING_LIMITS_H__
+#define __LZ4_FREESTANDING_LIMITS_H__
+
+#include <linux/limits.h>
+
+#endif
lib/lz4/freestanding/stddef.h new file +15 -0
new file mode 100644
index 0000000000000000000000000000000000000000..aaafd2413849210fa4ec4fa03ba0e9453a9fe026
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2026 Samsung Electronics Co., Ltd.
+ * Author: Michal Wilczynski <[email protected]>
+ *
+ * Freestanding <stddef.h> for the vendored upstream LZ4 sources; -nostdinc
+ * drops the compiler's copy, and lz4.h needs size_t and NULL.
+ */
+#ifndef __LZ4_FREESTANDING_STDDEF_H__
+#define __LZ4_FREESTANDING_STDDEF_H__
+
+#include <linux/stddef.h>	/* NULL, offsetof */
+#include <linux/types.h>	/* size_t, ptrdiff_t */
+
+#endif
lib/lz4/freestanding/stdint.h new file +14 -0
new file mode 100644
index 0000000000000000000000000000000000000000..923db05b19f23fb4051d16e5df2bf134cd5ac11e
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2026 Samsung Electronics Co., Ltd.
+ * Author: Michal Wilczynski <[email protected]>
+ *
+ * Freestanding <stdint.h> for the vendored upstream LZ4 sources; forwards to
+ * <linux/types.h>.
+ */
+#ifndef __LZ4_FREESTANDING_STDINT_H__
+#define __LZ4_FREESTANDING_STDINT_H__
+
+#include <linux/types.h>
+
+#endif
lib/lz4/freestanding/string.h new file +14 -0
new file mode 100644
index 0000000000000000000000000000000000000000..8f3ea3b63013608a780a52fe9c33bf5df557584e
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2026 Samsung Electronics Co., Ltd.
+ * Author: Michal Wilczynski <[email protected]>
+ *
+ * Freestanding <string.h> for the vendored upstream LZ4 sources; lz4.c
+ * includes it for memcpy()/memset(), which must resolve under -nostdinc.
+ */
+#ifndef __LZ4_FREESTANDING_STRING_H__
+#define __LZ4_FREESTANDING_STRING_H__
+
+#include <linux/string.h>
+
+#endif
lib/lz4/lz4_deps.h new file +96 -0

96 lines not on this page · raw message

lib/lz4/lz4_kernel_api.h new file +98 -0

98 lines not on this page · raw message

Signature · 1 line
2.34.1
#14 lore raw

Re: [PATCH RFC 3/9] lib/lz4: add the build environment for the vendored sources

Sashiko has reviewed this patch and found no issues. It looks great!
Quoted 25 lines

lz4_deps.h makes the unmodified upstream sources compile in the kernel:
it supplies the ISO C spellings they expect, gives every upstream entry point internal linkage so an object carries only the codec it forwards, keeps every workspace off the stack, and renames the entry points the kernel re-exports with a trailing wrkmem argument.

freestanding/ forwards the four ISO C headers upstream includes (stddef.h, stdint.h, limits.h, string.h) to their <linux/> equivalents.

The vendored functions an object does not forward are unreferenced, so LZ4LIB_VISIBILITY carries __maybe_unused rather than disabling -Wunused-function for a directory. This also covers the pre-boot decompressors, which compile lz4_decompress.c textually and never see lib/lz4's ccflags.

For the same reason this header includes <linux/build_bug.h>: the entry points static_assert upstream's structure sizes, and only some architectures' pre-boot environments have static_assert in scope.

lz4_kernel_api.h undoes the renaming for the entry point files and declares what lib/lz4 exports. It starts out carrying its own copy of those prototypes, because it cannot include <linux/lz4.h> while that header still defines the three stream types upstream's headers also define. A later patch folds it away once they are incomplete.

Quoted 3 lines

Nothing includes either header yet.

Sashiko has reviewed this patch and found no issues. It looks great!

Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=3
#15 lore raw

Re: [PATCH RFC 3/9] lib/lz4: add the build environment for the vendored sources

In reply to Michal Wilczynski

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

lib/lz4/lz4_deps.h line 48

Quoted 3 lines
lib/lz4/lz4_deps.h new file +3 -0
+
+/* LZ4_decompress_fast() and LZ4_resetStream() are still kernel API. */
+#define LZ4_DISABLE_DEPRECATE_WARNINGS 1

Is this upstream code? As far as I understand it, LZ4_decompress_fast*() deprecated upstream and are strongly discouraged. Do we want to suppress deprecation warnings?

#16 lore raw

Re: [PATCH RFC 3/9] lib/lz4: add the build environment for the vendored sources

Quoted 10 lines · Sergey Senozhatsky

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

lib/lz4/lz4_deps.h line 48

Quoted 3 lines
lib/lz4/lz4_deps.h new file +3 -0
+
+/* LZ4_decompress_fast() and LZ4_resetStream() are still kernel API. */
+#define LZ4_DISABLE_DEPRECATE_WARNINGS 1

Is this upstream code? As far as I understand it, LZ4_decompress_fast*() deprecated upstream and are strongly discouraged. Do we want to suppress deprecation warnings?

It's ours lz4_deps.h but upstream's lz4.c sets the same switch for itself lz4.c, since its own code calls deprecated functions. We include lz4.h before lz4.c, so we have to set it first.

I agree on the direction. The only in-tree _fast() user is the pre boot path of lib/decompress_unlz4.c, so as a follow-up I'd move it to LZ4_decompress_safe_partial() and drop the three _fast exports.

Best regards,

Signature · 1 line
Michal Wilczynski <[email protected]>
#17 lore raw

RFC PATCH 4/9 arch: boot: put the LZ4 freestanding headers on the decompressor path

In reply to Michal Wilczynski

lib/decompress_unlz4.c pulls lib/lz4/lz4_decompress.c into the pre-boot decompressor on these five arches. A later patch makes that file include the vendored LZ4 sources, which include ISO C headers that -nostdinc does not provide, so put lib/lz4/freestanding on the include path first.

---
 arch/arm/boot/compressed/Makefile    | 3 +++
 arch/mips/boot/compressed/Makefile   | 4 ++++
 arch/parisc/boot/compressed/Makefile | 3 +++
 arch/s390/boot/Makefile              | 3 +++
 arch/x86/boot/compressed/Makefile    | 3 +++
 5 files changed, 16 insertions(+)
arch/arm/boot/compressed/Makefile +3 -0
index e3f550d6285786c8405b16768255af87b4dc8222..c0418ef2618bbcbf18f905e619031c37661563ed 100644
@@ -92,6 +92,9 @@ targets       := vmlinux vmlinux.lds piggy_data piggy.o \
 		 head.o $(OBJS)
 
 KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
+# decompress_unlz4.c builds the vendored LZ4 sources, which include a few
+# ISO C headers -nostdinc drops.
+KBUILD_CFLAGS += -I$(srctree)/lib/lz4/freestanding
 
 ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \
 	     -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \
arch/mips/boot/compressed/Makefile +4 -0
index e0b8ec9a9516281933b6cc5b175e82f4013c2f54..b832b8a26f20073d817fb50bc4c8015de006b5e4 100644
@@ -30,6 +30,10 @@ endif
 KBUILD_CFLAGS := $(KBUILD_CFLAGS) -D__KERNEL__ -D__DISABLE_EXPORTS \
 	-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE) -D"VMLINUX_LOAD_ADDRESS_ULL=$(VMLINUX_LOAD_ADDRESS)ull"
 
+# decompress_unlz4.c builds the vendored LZ4 sources, which include a few
+# ISO C headers -nostdinc drops.
+KBUILD_CFLAGS += -I$(srctree)/lib/lz4/freestanding
+
 KBUILD_AFLAGS := $(KBUILD_AFLAGS) -D__ASSEMBLY__ \
 	-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE) \
 	-DKERNEL_ENTRY=$(VMLINUX_ENTRY_ADDRESS)
arch/parisc/boot/compressed/Makefile +3 -0
index 14eefb5ed5d1d781a4ee0cb2ef61ab86c905cc56..1d4a3e66e3503714c1f723dedb15598183ec8b0a 100644
@@ -12,6 +12,9 @@ targets += $(OBJECTS) sizes.h
 
 KBUILD_CFLAGS := -D__KERNEL__ -O2 -DBOOTLOADER
 KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
+# decompress_unlz4.c builds the vendored LZ4 sources, which include a few
+# ISO C headers -nostdinc drops.
+KBUILD_CFLAGS += -I$(srctree)/lib/lz4/freestanding
 KBUILD_CFLAGS += -fno-strict-aliasing
 KBUILD_CFLAGS += $(cflags-y) -fno-delete-null-pointer-checks -fno-builtin-printf
 KBUILD_CFLAGS += -fno-PIE -mno-space-regs -mdisable-fpregs -Os
arch/s390/boot/Makefile +3 -0
index 10b75e053a6f6bb9083548e8f82796f0aa9a9958..fd88523eb1102af1eb1f821e156b8faadb502879 100644
@@ -21,6 +21,9 @@ KBUILD_AFLAGS := $(filter-out $(CC_FLAGS_MARCH),$(KBUILD_AFLAGS_DECOMPRESSOR))
 KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_MARCH),$(KBUILD_CFLAGS_DECOMPRESSOR))
 KBUILD_AFLAGS += $(CC_FLAGS_MARCH_MINIMUM) -D__DISABLE_EXPORTS
 KBUILD_CFLAGS += $(CC_FLAGS_MARCH_MINIMUM) -D__DISABLE_EXPORTS
+# decompress_unlz4.c builds the vendored LZ4 sources, which include a few
+# ISO C headers -nostdinc drops.
+KBUILD_CFLAGS += -I$(srctree)/lib/lz4/freestanding
 KBUILD_CFLAGS += $(call cc-option, -Wno-default-const-init-unsafe)
 
 CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char
arch/x86/boot/compressed/Makefile +3 -0
index 06934f9691d6a9d6952532ae5f7d96f5858719dd..d200a0a4c28b9e7be1be45f603e625eb573d0220 100644
@@ -30,6 +30,9 @@ KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
 KBUILD_CFLAGS += -fno-jump-tables
 KBUILD_CFLAGS += -Wundef
 KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
+# decompress_unlz4.c builds the vendored LZ4 sources, which include a few
+# ISO C headers -nostdinc drops.
+KBUILD_CFLAGS += -I$(srctree)/lib/lz4/freestanding
 cflags-$(CONFIG_X86_32) := -march=i386
 cflags-$(CONFIG_X86_64) := -mcmodel=small -mno-red-zone
 KBUILD_CFLAGS += $(cflags-y)
Signature · 1 line
2.34.1
#18 lore raw

Re: [PATCH RFC 4/9] arch: boot: put the LZ4 freestanding headers on the decompressor path

Sashiko has reviewed this patch and found no issues. It looks great!
Quoted 6 lines

lib/decompress_unlz4.c pulls lib/lz4/lz4_decompress.c into the pre-boot decompressor on these five arches. A later patch makes that file include the vendored LZ4 sources, which include ISO C headers that -nostdinc does not provide, so put lib/lz4/freestanding on the include path first.

Sashiko has reviewed this patch and found no issues. It looks great!

Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=4
#19 lore raw

RFC PATCH 5/9 lib/lz4: switch the compressor to the vendored sources

In reply to Michal Wilczynski

Replace the forked compressor with thin entry points over the vendored lz4.c.

LZ4_compress_default(), LZ4_compress_fast() and LZ4_compress_destSize() keep the trailing wrkmem argument and forward to upstream's *_extState() entry points. The rest are plain forwarders.

Compressed output is not quite bit-for-bit identical: it differs on a small fraction of inputs by a byte or two, with no measurable change in ratio. Both implementations decode each other's output, so nothing already on disk changes meaning.

<linux/lz4.h> spelled out LZ4_stream_t's layout for the fork's benefit:
lz4defs.h included the public header and the fork read internal_donotuse back out. The vendored compressor brings upstream's own definition, so make the public type incomplete, repeating upstream's forward declaration. Both headers then name the same type, which lib/decompress_unlz4.c needs since it ends up including both.

LZ4_MEMORY_USAGE, LZ4_HASHLOG, LZ4_HASHTABLESIZE, LZ4_HASH_SIZE_U32, LZ4_STREAMSIZE_U64 and LZ4_STREAMSIZE only existed to lay that structure out, and go with it. LZ4_MEM_COMPRESS keeps its value, 16416, as a plain number.

Callers now allocate LZ4_MEM_COMPRESS bytes instead of sizeof(LZ4_stream_t). Every caller but zram already did; zram is adjusted here.

---
 drivers/block/zram/backend_lz4.c |   6 +-
 include/linux/lz4.h              |  47 +-
 lib/lz4/Makefile                 |  11 +-
 lib/lz4/lz4_compress.c           | 941 ++-------------------------------------
 4 files changed, 68 insertions(+), 937 deletions(-)
drivers/block/zram/backend_lz4.c +3 -3
index 1e4ad31d39a63f45b3bddd3d8a467d8d7d095beb..50265e3ce256490994cb6dae32a45da376e408e0 100644
@@ -42,7 +42,7 @@ static int lz4_setup_params(struct zcomp_params *params)
 	if (!params->dict || !params->dict_sz)
 		return 0;
 
-	dict_stream = kzalloc_obj(*dict_stream);
+	dict_stream = kzalloc(LZ4_MEM_COMPRESS, GFP_KERNEL);
 	if (!dict_stream)
 		return -ENOMEM;
 
@@ -88,7 +88,7 @@ static int lz4_create(struct zcomp_params *params, struct zcomp_ctx *ctx)
 		if (!zctx->dstrm)
 			goto error;
 
-		zctx->cstrm = kzalloc_obj(*zctx->cstrm);
+		zctx->cstrm = kzalloc(LZ4_MEM_COMPRESS, GFP_KERNEL);
 		if (!zctx->cstrm)
 			goto error;
 	}
@@ -112,7 +112,7 @@ static int lz4_compress(struct zcomp_params *params, struct zcomp_ctx *ctx,
 					zctx->mem);
 	} else {
 		/* Cstrm needs to be reset */
-		memcpy(zctx->cstrm, params->drv_data, sizeof(*zctx->cstrm));
+		memcpy(zctx->cstrm, params->drv_data, LZ4_MEM_COMPRESS);
 		ret = LZ4_compress_fast_continue(zctx->cstrm, req->src,
 						 req->dst, req->src_len,
 						 req->dst_len, params->level);
include/linux/lz4.h +13 -34

102 lines not on this page · raw message

lib/lz4/Makefile +8 -3
index 5b42242afaa20deb165d8a2f0b1c0c842dfcdc39..e9d83cff4ea4efe1097f54caba72e268cecb04af 100644
@@ -1,6 +1,11 @@
 # SPDX-License-Identifier: GPL-2.0-only
 ccflags-y += -O3
 
-obj-$(CONFIG_LZ4_COMPRESS) += lz4_compress.o
-obj-$(CONFIG_LZ4HC_COMPRESS) += lz4hc_compress.o
-obj-$(CONFIG_LZ4_DECOMPRESS) += lz4_decompress.o
+# upstream/ holds verbatim copies of the upstream LZ4 sources; do not edit
+# them.  The three entry point files include them.  freestanding/ supplies
+# the ISO C headers upstream includes that -nostdinc does not provide.
+ccflags-y += -I $(src)/freestanding
+
+obj-$(CONFIG_LZ4_COMPRESS)	+= lz4_compress.o
+obj-$(CONFIG_LZ4HC_COMPRESS)	+= lz4hc_compress.o
+obj-$(CONFIG_LZ4_DECOMPRESS)	+= lz4_decompress.o
lib/lz4/lz4_compress.c +44 -897

981 lines not on this page · raw message

Signature · 1 line
2.34.1
#20 lore raw

Re: [PATCH RFC 5/9] lib/lz4: switch the compressor to the vendored sources

Sashiko has reviewed this patch and found no issues. It looks great!
Quoted 24 lines

Replace the forked compressor with thin entry points over the vendored lz4.c.

LZ4_compress_default(), LZ4_compress_fast() and LZ4_compress_destSize() keep the trailing wrkmem argument and forward to upstream's *_extState() entry points. The rest are plain forwarders.

Compressed output is not quite bit-for-bit identical: it differs on a small fraction of inputs by a byte or two, with no measurable change in ratio. Both implementations decode each other's output, so nothing already on disk changes meaning.

<linux/lz4.h> spelled out LZ4_stream_t's layout for the fork's benefit:
lz4defs.h included the public header and the fork read internal_donotuse back out. The vendored compressor brings upstream's own definition, so make the public type incomplete, repeating upstream's forward declaration. Both headers then name the same type, which lib/decompress_unlz4.c needs since it ends up including both.

LZ4_MEMORY_USAGE, LZ4_HASHLOG, LZ4_HASHTABLESIZE, LZ4_HASH_SIZE_U32, LZ4_STREAMSIZE_U64 and LZ4_STREAMSIZE only existed to lay that structure out, and go with it. LZ4_MEM_COMPRESS keeps its value, 16416, as a plain number.

Quoted 5 lines

Callers now allocate LZ4_MEM_COMPRESS bytes instead of sizeof(LZ4_stream_t). Every caller but zram already did; zram is adjusted here.

Sashiko has reviewed this patch and found no issues. It looks great!

Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=5
#21 lore raw

RFC PATCH 6/9 lib/lz4: switch the HC compressor to the vendored sources

In reply to Michal Wilczynski

Replace the forked LZ4HC with thin entry points over the vendored lz4hc.c.

The HC entry points clamp the level below LZ4HC_CLEVEL_OPT_MIN, since upstream routes levels 10 and up to the optimal parser whose ~64K workspace does not fit a kernel stack. Levels are clamped rather than rejected so existing f2fs and zram settings keep working; they now compress as level 9.

f2fs and zram both take user levels up to LZ4HC_MAX_CLEVEL, so <linux/lz4.h> gains LZ4HC_CLAMP_CLEVEL and says what happens at or above it. A later patch ties that constant to upstream's LZ4HC_CLEVEL_OPT_MIN with a static_assert, once <linux/lz4.h> is in scope of these files.

Levels 1 and 2 change in the other direction. Upstream routes them through its new lz4mid strategy: at a 4K block that is 26% faster for 10% and 19% worse ratio, and at 64K it is 83% and 90% faster for 14% and 26% worse. In the fork level 1 was only 10% faster than level 3 while compressing 17% worse, so this is a better point on the curve rather than a loss, but it is a change. f2fs rejects levels below LZ4HC_MIN_CLEVEL, so only zram can select them; a caller that wants the old ratio should ask for level 3.

As with LZ4_stream_t, LZ4_streamHC_t becomes an incomplete type, and the macros that laid the forked structure out (LZ4HC_DICTIONARY_LOGSIZE, LZ4HC_MAXD, LZ4HC_MAXD_MASK, LZ4HC_HASH_LOG, LZ4HC_HASHTABLESIZE, LZ4HC_HASH_MASK, LZ4_STREAMHCSIZE, LZ4_STREAMHCSIZE_SIZET) go with it.

LZ4HC_MEM_COMPRESS grows from 262192 to upstream's LZ4_STREAMHC_MINSIZE, 262200: upstream's LZ4HC_CCtx_internal has fields the forked one does not, most visibly the dictionary context pointer. It has to grow in the same commit; an allocation eight bytes short of what the compressor initialises would overrun zram's compress path. The size is static_asserted against upstream's own LZ4_STREAMHC_MINSIZE, so a future re-sync that changes it fails the build rather than the allocation.

lz4hc.c pulls in lz4.c for its common definitions, which include two decoder tables used there only by the fast decode loop. On architectures where that loop is off, W=1 reports them as unused. Silence that one warning for this one object rather than edit the vendored file.

This retires one local patch:

commit b08918fb3f27 ("lz4: do not export static symbol")

---
 drivers/block/zram/backend_lz4hc.c |   2 +-
 include/linux/lz4.h                |  53 +--
 lib/lz4/Makefile                   |   4 +
 lib/lz4/lz4hc_compress.c           | 785 +++----------------------------------
 4 files changed, 76 insertions(+), 768 deletions(-)
drivers/block/zram/backend_lz4hc.c +1 -1
index d8aa01bb258fec760b597a88296dfaa4e0049693..894695753d99bf2fec7e191c4ec2fff489b5bddd 100644
@@ -69,7 +69,7 @@ static int lz4hc_create(struct zcomp_params *params, struct zcomp_ctx *ctx)
 		if (!zctx->dstrm)
 			goto error;
 
-		zctx->cstrm = kzalloc_obj(*zctx->cstrm);
+		zctx->cstrm = kzalloc(LZ4HC_MEM_COMPRESS, GFP_KERNEL);
 		if (!zctx->cstrm)
 			goto error;
 	}
include/linux/lz4.h +15 -38

88 lines not on this page · raw message

lib/lz4/Makefile +4 -0
index e9d83cff4ea4efe1097f54caba72e268cecb04af..9ac36ada805cc99d6db43d141394e51b4b1f7598 100644
@@ -9,3 +9,7 @@ ccflags-y += -I $(src)/freestanding
 obj-$(CONFIG_LZ4_COMPRESS)	+= lz4_compress.o
 obj-$(CONFIG_LZ4HC_COMPRESS)	+= lz4hc_compress.o
 obj-$(CONFIG_LZ4_DECOMPRESS)	+= lz4_decompress.o
+
+# lz4hc.c pulls in lz4.c's common definitions, which include two decoder
+# tables nothing here uses when LZ4_FAST_DEC_LOOP is off.
+CFLAGS_lz4hc_compress.o += $(call cc-disable-warning, unused-const-variable)
lib/lz4/lz4hc_compress.c +56 -729

822 lines not on this page · raw message

Signature · 1 line
2.34.1
#22 lore raw

Re: [PATCH RFC 6/9] lib/lz4: switch the HC compressor to the vendored sources

Sashiko has reviewed this patch and found no issues. It looks great!
Quoted 14 lines

Replace the forked LZ4HC with thin entry points over the vendored lz4hc.c.

The HC entry points clamp the level below LZ4HC_CLEVEL_OPT_MIN, since upstream routes levels 10 and up to the optimal parser whose ~64K workspace does not fit a kernel stack. Levels are clamped rather than rejected so existing f2fs and zram settings keep working; they now compress as level 9.

f2fs and zram both take user levels up to LZ4HC_MAX_CLEVEL, so <linux/lz4.h> gains LZ4HC_CLAMP_CLEVEL and says what happens at or above it. A later patch ties that constant to upstream's LZ4HC_CLEVEL_OPT_MIN with a static_assert, once <linux/lz4.h> is in scope of these files.

Quoted 7 lines

Levels 1 and 2 change in the other direction. Upstream routes them [ ... ]
This retires one local patch:

commit b08918fb3f27 ("lz4: do not export static symbol")

Sashiko has reviewed this patch and found no issues. It looks great!

Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=6
#23 lore raw

RFC PATCH 7/9 lib/lz4: switch the decompressor to the vendored sources

In reply to Michal Wilczynski

Replace the forked decompressor with thin entry points over the vendored lz4.c. The API is already signature-compatible, so every export is a plain forwarder. lz4defs.h has no users left and goes.

lib/decompress_unlz4.c still includes this file for the pre-boot decompressor; the exports stay behind #ifndef STATIC.

That include is why LZ4_streamDecode_t is incomplete: under PREBOOT the translation unit has both <linux/lz4.h> and upstream's lz4.h, so both must name the same type. Both repeat upstream's forward declaration, and the file builds without guards.

LZ4_streamDecode_t is the last of the three, so LZ4_STREAMDECODESIZE and LZ4_STREAMDECODESIZE_U64 go and LZ4_MEM_DECOMPRESS takes over, 32 bytes.

LZ4_COMPRESSBOUND is likewise defined by both headers; guard it. LZ4_compressBound() cannot be guarded, so drop the inline wrapper:
lib/decompress_unlz4.c was its only caller and uses the macro now.

This picks up upstream's decoder fixes since v1.8.3 and retires six local patches:

commit 8cb5d7482810 ("lib/lz4: make arrays static const, reduces object code size") commit b1a3e75e466d ("lz4: fix kernel decompression speed")
commit 89b158635ad7 ("lib/lz4: explicitly support in-place decompression") commit 7fde9d6e839d ("lz4_decompress: declare LZ4_decompress_safe_withPrefix64k static") commit eafc0a02391b ("lz4: fix LZ4_decompress_safe_partial read out of bound") commit 2d8867f3e083 ("lib: make LZ4_decompress_safe_forceExtDict() static")

The decompression speed fix has an upstream equivalent, carried since v1.9.3 as upstream commit fe2a1b3707d5
("Call LZ4_memcpy() instead of memcpy()").

---
 drivers/block/zram/backend_lz4.c   |   2 +-
 drivers/block/zram/backend_lz4hc.c |   2 +-
 include/linux/lz4.h                |  51 +--
 lib/decompress_unlz4.c             |   4 +-
 lib/lz4/lz4_decompress.c           | 718 +++----------------------------------
 lib/lz4/lz4defs.h                  | 247 -------------
 6 files changed, 74 insertions(+), 950 deletions(-)
drivers/block/zram/backend_lz4.c +1 -1
index 50265e3ce256490994cb6dae32a45da376e408e0..b9b8a5f678c155442fa3fd2c1984e45182e6fc38 100644
@@ -84,7 +84,7 @@ static int lz4_create(struct zcomp_params *params, struct zcomp_ctx *ctx)
 		if (!zctx->mem)
 			goto error;
 	} else {
-		zctx->dstrm = kzalloc_obj(*zctx->dstrm);
+		zctx->dstrm = kzalloc(LZ4_MEM_DECOMPRESS, GFP_KERNEL);
 		if (!zctx->dstrm)
 			goto error;
 
drivers/block/zram/backend_lz4hc.c +1 -1
index 894695753d99bf2fec7e191c4ec2fff489b5bddd..7fabd0e6d66095d411007bec5eaa8e5f553b626d 100644
@@ -65,7 +65,7 @@ static int lz4hc_create(struct zcomp_params *params, struct zcomp_ctx *ctx)
 		if (!zctx->mem)
 			goto error;
 	} else {
-		zctx->dstrm = kzalloc_obj(*zctx->dstrm);
+		zctx->dstrm = kzalloc(LZ4_MEM_DECOMPRESS, GFP_KERNEL);
 		if (!zctx->dstrm)
 			goto error;
 
include/linux/lz4.h +16 -35

110 lines not on this page · raw message

lib/decompress_unlz4.c +2 -2
index c0dbb3cea915eb91d8f4ac26c38c4785bbf19770..48ac767dbf68d69082dd00fa4970aaf50aa1db5c 100644
@@ -69,7 +69,7 @@ STATIC inline int INIT unlz4(u8 *input, long in_len,
 		error("NULL input pointer and missing fill function");
 		goto exit_1;
 	} else {
-		inp = large_malloc(LZ4_compressBound(uncomp_chunksize));
+		inp = large_malloc(LZ4_COMPRESSBOUND(uncomp_chunksize));
 		if (!inp) {
 			error("Could not allocate input buffer");
 			goto exit_1;
@@ -140,7 +140,7 @@ STATIC inline int INIT unlz4(u8 *input, long in_len,
 			inp += 4;
 			size -= 4;
 		} else {
-			if (chunksize > LZ4_compressBound(uncomp_chunksize)) {
+			if (chunksize > LZ4_COMPRESSBOUND(uncomp_chunksize)) {
 				error("chunk length is longer than allocated");
 				goto exit_2;
 			}
lib/lz4/lz4_decompress.c +54 -664

761 lines not on this page · raw message

lib/lz4/lz4defs.h deleted +0 -247

247 lines not on this page · raw message

Signature · 1 line
2.34.1
#24 lore raw

Re: [PATCH RFC 7/9] lib/lz4: switch the decompressor to the vendored sources

Sashiko has reviewed this patch and found no issues. It looks great!
Quoted 15 lines

Replace the forked decompressor with thin entry points over the vendored lz4.c. The API is already signature-compatible, so every export is a plain forwarder. lz4defs.h has no users left and goes.

lib/decompress_unlz4.c still includes this file for the pre-boot decompressor; the exports stay behind #ifndef STATIC.

That include is why LZ4_streamDecode_t is incomplete: under PREBOOT the translation unit has both <linux/lz4.h> and upstream's lz4.h, so both must name the same type. Both repeat upstream's forward declaration, and the file builds without guards.

LZ4_streamDecode_t is the last of the three, so LZ4_STREAMDECODESIZE and LZ4_STREAMDECODESIZE_U64 go and LZ4_MEM_DECOMPRESS takes over, 32 bytes.

Quoted 6 lines

[ ... ]
The decompression speed fix has an upstream equivalent, carried since v1.9.3 as upstream commit fe2a1b3707d5
("Call LZ4_memcpy() instead of memcpy()").

Sashiko has reviewed this patch and found no issues. It looks great!

Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=7
#25 lore raw

Re: [PATCH RFC 7/9] lib/lz4: switch the decompressor to the vendored sources

In reply to Michal Wilczynski

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

Quoted 1 line

-static FORCE_INLINE int LZ4_decompress_generic(

[..]

lib/lz4/lz4_decompress.c line 279

Quoted 7 lines
lib/lz4/lz4_decompress.c +0 -7
-			/* Necessarily EOF when !partialDecoding.
-			 * When partialDecoding, it is EOF if we've either
-			 * filled the output buffer or
-			 * can't proceed with reading an offset for following match.
-			 */
-			if (!partialDecoding || (cpy == oend) || (ip >= (iend - 2)))
-				break;

Worth noting, these lines are downstream commit eafc0a02391b (lz4: fix LZ4_decompress_safe_partial read out of bound).

Is this intended or are we "loosing" some of the downstream fixes?

#26 lore raw

Re: [PATCH RFC 7/9] lib/lz4: switch the decompressor to the vendored sources

Quoted 15 lines · Sergey Senozhatsky

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

Quoted 1 line

-static FORCE_INLINE int LZ4_decompress_generic(

[..]

lib/lz4/lz4_decompress.c line 279

Quoted 7 lines
lib/lz4/lz4_decompress.c +0 -7
-			/* Necessarily EOF when !partialDecoding.
-			 * When partialDecoding, it is EOF if we've either
-			 * filled the output buffer or
-			 * can't proceed with reading an offset for following match.
-			 */
-			if (!partialDecoding || (cpy == oend) || (ip >= (iend - 2)))
-				break;

Worth noting, these lines are downstream commit eafc0a02391b (lz4: fix LZ4_decompress_safe_partial read out of bound).

Quoted 2 lines

Is this intended or are we "loosing" some of the downstream fixes?

Yeah it's intended, eafc0a02391b was itself a backport of upstream c5d6f8a8be39 which is in v1.9.3 and later; its own commit message links it. The same check is at lib/lz4/upstream/lz4.c in this series.

And upstream's version also clamps a literal run that would read past the end of the input, which the backport didn't take.

Best regards,

Signature · 1 line
Michal Wilczynski <[email protected]>
#27 lore raw

RFC PATCH 8/9 lib/lz4: fold lz4_kernel_api.h into <linux/lz4.h>

In reply to Michal Wilczynski

lz4_kernel_api.h carried its own copy of the twenty public prototypes because it could not include <linux/lz4.h>, which defined the stream types that upstream's headers also define.

The types are incomplete now, so it can. Two prototype lists for one ABI is a drift hazard: the entry points were built against one and their callers against the other, so no compiler ever saw both, and MODVERSIONS would not catch a mismatch either, since it hashes the exporter's view only. Now there is one list.

It also puts the public constants in scope of the entry points, so the size assertions can name them, and the HC level clamp can use LZ4HC_CLAMP_CLEVEL, static_asserted equal to upstream's LZ4HC_CLEVEL_OPT_MIN.

---
 lib/lz4/lz4_compress.c   |  2 +-
 lib/lz4/lz4_decompress.c |  2 +-
 lib/lz4/lz4_kernel_api.h | 71 +++---------------------------------------------
 lib/lz4/lz4hc_compress.c |  8 ++++--
 4 files changed, 11 insertions(+), 72 deletions(-)
lib/lz4/lz4_compress.c +1 -1
index 19b877fc96d1dde6fd5ff832f79beca42d5b783b..40ebbc850f42f60ca2ddbcacd3b804cfde9e8d4e 100644
@@ -29,7 +29,7 @@
 
 /* Catch any divergence from upstream's layout at build time. */
 static_assert(sizeof(LZ4_stream_t) == LZ4_STREAM_MINSIZE);
-static_assert(LZ4_STREAM_MINSIZE == 16416); /* LZ4_MEM_COMPRESS */
+static_assert(LZ4_STREAM_MINSIZE == LZ4_MEM_COMPRESS);
 
 int LZ4_compress_fast(const char *source, char *dest, int inputSize,
 		      int maxOutputSize, int acceleration, void *wrkmem)
lib/lz4/lz4_decompress.c +1 -1
index 68c8a87476df58fff48b1ffbeee8f2d3bbf743df..49e6f76af975435c10c387c09bb639525a89b5f9 100644
@@ -31,7 +31,7 @@
 #endif
 
 static_assert(sizeof(LZ4_streamDecode_t) == LZ4_STREAMDECODE_MINSIZE);
-static_assert(LZ4_STREAMDECODE_MINSIZE == 32); /* LZ4_MEM_DECOMPRESS */
+static_assert(LZ4_STREAMDECODE_MINSIZE == LZ4_MEM_DECOMPRESS);
 
 int LZ4_decompress_safe(const char *source, char *dest, int compressedSize,
 			int maxDecompressedSize)
lib/lz4/lz4_kernel_api.h +4 -67

81 lines not on this page · raw message

lib/lz4/lz4hc_compress.c +5 -3
index 6070719bab54e90a8a163c08842a5531d7b2b4ac..ad49a3509aaac25850c045347d588b9354a8ce18 100644
@@ -38,7 +38,7 @@ static int LZ4_compressBound(int isize)
 
 /* Catch any divergence from upstream's layout at build time. */
 static_assert(sizeof(LZ4_streamHC_t) == LZ4_STREAMHC_MINSIZE);
-static_assert(LZ4_STREAMHC_MINSIZE == 262200); /* LZ4HC_MEM_COMPRESS */
+static_assert(LZ4_STREAMHC_MINSIZE == LZ4HC_MEM_COMPRESS);
 
 /* Levels >= LZ4HC_CLEVEL_OPT_MIN (10) reach the optimal parser, whose ~64K
  * opt[] does not fit a kernel stack, so clamp them to 9.  Clamp rather than
@@ -46,10 +46,12 @@ static_assert(LZ4_STREAMHC_MINSIZE == 262200); /* LZ4HC_MEM_COMPRESS */
  * untouched; 1 and 2 are upstream's lz4mid, faster and weaker than the
  * shallow hash chain the fork used for them.
  */
+static_assert(LZ4HC_CLAMP_CLEVEL == LZ4HC_CLEVEL_OPT_MIN);
+
 static int lz4hc_clamp_level(int compressionLevel)
 {
-	if (compressionLevel >= LZ4HC_CLEVEL_OPT_MIN)
-		return LZ4HC_CLEVEL_OPT_MIN - 1;
+	if (compressionLevel >= LZ4HC_CLAMP_CLEVEL)
+		return LZ4HC_CLAMP_CLEVEL - 1;
 
 	return compressionLevel;
 }
Signature · 1 line
2.34.1
#28 lore raw

Re: [PATCH RFC 8/9] lib/lz4: fold lz4_kernel_api.h into <linux/lz4.h>

Sashiko has reviewed this patch and found no issues. It looks great!
Quoted 10 lines

lz4_kernel_api.h carried its own copy of the twenty public prototypes because it could not include <linux/lz4.h>, which defined the stream types that upstream's headers also define.

The types are incomplete now, so it can. Two prototype lists for one ABI is a drift hazard: the entry points were built against one and their callers against the other, so no compiler ever saw both, and MODVERSIONS would not catch a mismatch either, since it hashes the exporter's view only. Now there is one list.

Quoted 6 lines

It also puts the public constants in scope of the entry points, so the size assertions can name them, and the HC level clamp can use LZ4HC_CLAMP_CLEVEL, static_asserted equal to upstream's LZ4HC_CLEVEL_OPT_MIN.

Sashiko has reviewed this patch and found no issues. It looks great!

Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=8
#29 lore raw

RFC PATCH 9/9 MAINTAINERS: add an entry for the LZ4 compression library

In reply to Michal Wilczynski

lib/lz4/ has never had one: get_maintainer.pl returns only the LKML fallback for every file in it, including include/linux/lz4.h, which eight subsystems build against.

This matters more now than it did. With the previous patches lib/lz4 is vendored upstream sources, and someone has to bump them to new upstream releases and decide what the kernel-side glue may do. I am willing to do that, so add myself as its maintainer.

---
 MAINTAINERS | 6 ++++++
 1 file changed, 6 insertions(+)
MAINTAINERS +6 -0
index cc3cae2e378b34aeb705cef654c720ca9f2ba223..989e1b5fab21432dd7042d1e60c4bbad85beb925 100644
@@ -15606,6 +15606,12 @@ S:	Supported
 F:	drivers/net/pcs/pcs-lynx.c
 F:	include/linux/pcs-lynx.h
 
+LZ4 COMPRESSION LIBRARY
+M:	Michal Wilczynski <[email protected]>
+S:	Maintained
+F:	include/linux/lz4.h
+F:	lib/lz4/
+
 M68K ARCHITECTURE
 M:	Geert Uytterhoeven <[email protected]>
 L:	[email protected]
Signature · 1 line
2.34.1
#30 lore raw

Re: [PATCH RFC 9/9] MAINTAINERS: add an entry for the LZ4 compression library

Quoted 19 lines · Michal Wilczynski

lib/lz4/ has never had one: get_maintainer.pl returns only the LKML fallback for every file in it, including include/linux/lz4.h, which eight subsystems build against.

This matters more now than it did. With the previous patches lib/lz4 is vendored upstream sources, and someone has to bump them to new upstream releases and decide what the kernel-side glue may do. I am willing to do that, so add myself as its maintainer.

---
 MAINTAINERS | 6 ++++++
 1 file changed, 6 insertions(+)
MAINTAINERS +0 -0
index cc3cae2e378b34aeb705cef654c720ca9f2ba223..989e1b5fab21432dd7042d1e60c4bbad85beb925 100644

MAINTAINERS S: Supported · line 15614

Quoted 9 lines
MAINTAINERS +6 -0
@@ -15606,6 +15606,12 @@ S:	Supported
 F:	drivers/net/pcs/pcs-lynx.c
 F:	include/linux/pcs-lynx.h
 
+LZ4 COMPRESSION LIBRARY
+M:	Michal Wilczynski <[email protected]>
+S:	Maintained
+F:	include/linux/lz4.h
+F:	lib/lz4/
+

Should this entry cover lib/decompress_unlz4.c and include/linux/decompress/unlz4.h as well?

- Eric

#31 lore raw

Re: [PATCH RFC 9/9] MAINTAINERS: add an entry for the LZ4 compression library

Quoted 23 lines · Eric Biggers
Quoted 22 lines · Michal Wilczynski

lib/lz4/ has never had one: get_maintainer.pl returns only the LKML fallback for every file in it, including include/linux/lz4.h, which eight subsystems build against.

This matters more now than it did. With the previous patches lib/lz4 is vendored upstream sources, and someone has to bump them to new upstream releases and decide what the kernel-side glue may do. I am willing to do that, so add myself as its maintainer.

---
 MAINTAINERS | 6 ++++++
 1 file changed, 6 insertions(+)
MAINTAINERS +0 -0
index cc3cae2e378b34aeb705cef654c720ca9f2ba223..989e1b5fab21432dd7042d1e60c4bbad85beb925 100644
@@ -15606,6 +15606,12 @@ S:	Supported
 F:	drivers/net/pcs/pcs-lynx.c
 F:	include/linux/pcs-lynx.h
 
Quoted 9 lines

MAINTAINERS S: Supported · line 15614

Quoted 6 lines
MAINTAINERS +6 -0
+LZ4 COMPRESSION LIBRARY
+M:	Michal Wilczynski <[email protected]>
+S:	Maintained
+F:	include/linux/lz4.h
+F:	lib/lz4/
+

Should this entry cover lib/decompress_unlz4.c and include/linux/decompress/unlz4.h as well?

Yes I'll add both in v2.
Thanks a lot for looking at the series as a whole.

Quoted 3 lines

- Eric

Best regards,

Signature · 1 line
Michal Wilczynski <[email protected]>
#32 lore raw

Re: [PATCH RFC 0/9] lib/lz4: stop forking upstream LZ4, vendor it instead

In reply to Michal Wilczynski
Quoted 11 lines · Michal Wilczynski

The in-kernel LZ4 is a fork. The decompressor was last synced with upstream v1.8.3 in 2018 and the compressor with v1.7.3 in 2017, both by hand. Upstream has made 488 commits against lib/ since, and the gap is maintained one cherry-pick at a time.

That has left real bugs in place for example the forked LZ4_decompress_fast() has no bounds checks, so corrupted input runs off the output buffer in both directions.

This series vendors the upstream sources unmodified and adapts them at build time, so a re-sync becomes a directory copy:

At a high level, this looks good to me, and it's similar to what was done with zstd. I don't see any obvious issues with the integration.

There are disadvantages to directly integrating external projects like this, vs. writing a small implementation from scratch for the kernel. But the existing LZ4 code in the kernel isn't that, but rather a fork from upstream anyway, and it's clearly not being maintained properly.

The upstream LZ4 codebase also already avoids many of the typical incompatibilities with Linux kernel code that are often seen in userspace projects (such as assuming FPU/SIMD/vector instructions can be used at any time, or that the stack size is infinite, or that the C standard library is available, or that it's reasonable to have hundreds of files or 100MB of test data, etc.).

And writing properly optimized compression/decompression code is quite difficult. So yes, syncing with the latest LZ4 upstream seems like the right choice for the kernel.

- Eric

#33 lore raw

Re: [PATCH RFC 0/9] lib/lz4: stop forking upstream LZ4, vendor it instead

In reply to Michal Wilczynski

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

Quoted 10 lines

Michal Wilczynski (9):
lib/lz4: import upstream LZ4 sources verbatim
lib/lz4: backport upstream's -Wmissing-prototypes fix lib/lz4: add the build environment for the vendored sources
arch: boot: put the LZ4 freestanding headers on the decompressor path lib/lz4: switch the compressor to the vendored sources lib/lz4: switch the HC compressor to the vendored sources lib/lz4: switch the decompressor to the vendored sources lib/lz4: fold lz4_kernel_api.h into <linux/lz4.h>
MAINTAINERS: add an entry for the LZ4 compression library

On my x86_64 build .text size change seems to be quite significant:

./scripts/bloat-o-meter lib/lz4/lz4_compress-old.ko lib/lz4/lz4_compress.ko
add/remove: 0/2 grow/shrink: 5/1 up/down: 8022/-1755 (6267)

Function                                     old     new   delta
LZ4_compress_fast_continue                  6028   10486   +4458
LZ4_compress_destSize                        158    3112   +2954
LZ4_compress_fast_extState                  4078    4597    +519
LZ4_saveDict                                  82     153     +71
__UNIQUE_ID_modinfo_466                       52      72     +20
__pfx_LZ4_compress_destSize_generic           16       -     -16
LZ4_loadDict                                 261     204     -57

LZ4_compress_destSize_generic 1682 - -1682
Total: Before=14756, After=21023, chg +42.47%

#34 lore raw

Re: [PATCH RFC 0/9] lib/lz4: stop forking upstream LZ4, vendor it instead

Quoted 12 lines · Sergey Senozhatsky

On my x86_64 build .text size change seems to be quite significant:

./scripts/bloat-o-meter lib/lz4/lz4_compress-old.ko lib/lz4/lz4_compress.ko
add/remove: 0/2 grow/shrink: 5/1 up/down: 8022/-1755 (6267)

Function                                     old     new   delta
LZ4_compress_fast_continue                  6028   10486   +4458
LZ4_compress_destSize                        158    3112   +2954
LZ4_compress_fast_extState                  4078    4597    +519
LZ4_saveDict                                  82     153     +71
__UNIQUE_ID_modinfo_466                       52      72     +20
__pfx_LZ4_compress_destSize_generic           16       -     -16
LZ4_loadDict                                 261     204     -57
Quoted 2 lines

LZ4_compress_destSize_generic 1682 - -1682
Total: Before=14756, After=21023, chg +42.47%

D'oh you actually point that out in the commit message, sorry for the noise.