Extend and add a little more generalization to the mem_pool API

In my new merge algorithm, I made use of the mem_pool API in a few places...but I also needed to add a few more functions and also needed to make the API a bit more general.

Changes since v2:

* Remove 'x' from mem_pool_xstr[n]?dup() names and remove check for NULL since mem_pool_alloc() already handles that (via xmalloc), as suggested by René
* Rewrite mem_pool_strndup() to not rely on strnlen(), since that may be too new from some systems (comes from POSIX 2008 ). Also pointed out by René

Elijah Newren (3):
mem-pool: add convenience functions for strdup and strndup
mem-pool: use more standard initialization and finalization
mem-pool: use consistent pool variable name

 fast-import.c | 12 ++-------
 mem-pool.c    | 69 ++++++++++++++++++++++++++++++---------------------
 mem-pool.h    | 14 ++++++++---
 read-cache.c  | 21 ++++++++++------
 split-index.c |  6 +++--
 5 files changed, 70 insertions(+), 52 deletions(-)

base-commit: 7814e8a05a59c0cf5fb186661d1551c75d1299b5
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-830%2Fnewren%2Fmem_pool_api-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-830/newren/mem_pool_api-v3
Pull-Request: https://github.com/git/git/pull/830

Range-diff vs v2:

1: 6d679c5b46 ! 1: e7f6bf8a8c mem-pool: add convenience functions for xstrdup and xstrndup

     @@ Metadata
      Author: Elijah Newren <[email protected]>
      
       ## Commit message ##
     -    mem-pool: add convenience functions for xstrdup and xstrndup
     +    mem-pool: add convenience functions for strdup and strndup
      
     -    fast-import had a special mem_pool_xstrdup() convenience function that I
     +    fast-import had a special mem_pool_strdup() convenience function that I
          want to be able to use from the new merge algorithm I am writing.  Move
     -    it from fast-import to mem-pool, and also add a mem_pool_xstrndup()
     +    it from fast-import to mem-pool, and also add a mem_pool_strndup()
          while at it that I also want to use.
      
          Signed-off-by: Elijah Newren <[email protected]>
     @@ fast-import.c: static struct branch *new_branch(const char *name)
       
       	b = mem_pool_calloc(&fi_mem_pool, 1, sizeof(struct branch));
      -	b->name = pool_strdup(name);
     -+	b->name = mem_pool_xstrdup(&fi_mem_pool, name);
     ++	b->name = mem_pool_strdup(&fi_mem_pool, name);
       	b->table_next_branch = branch_table[hc];
       	b->branch_tree.versions[0].mode = S_IFDIR;
       	b->branch_tree.versions[1].mode = S_IFDIR;
     @@ fast-import.c: static void parse_new_tag(const char *arg)
       	t = mem_pool_alloc(&fi_mem_pool, sizeof(struct tag));
       	memset(t, 0, sizeof(struct tag));
      -	t->name = pool_strdup(arg);
     -+	t->name = mem_pool_xstrdup(&fi_mem_pool, arg);
     ++	t->name = mem_pool_strdup(&fi_mem_pool, arg);
       	if (last_tag)
       		last_tag->next_tag = t;
       	else
     @@ mem-pool.c: void *mem_pool_calloc(struct mem_pool *mem_pool, size_t count, size_
       	return r;
       }
       
     -+char *mem_pool_xstrdup(struct mem_pool *pool, const char *str)
     ++char *mem_pool_strdup(struct mem_pool *pool, const char *str)
      +{
      +	size_t len = strlen(str) + 1;
      +	char *ret = mem_pool_alloc(pool, len);
      +
     -+	if (!ret)
     -+		die(_("mem_pool_xstrdup: out of memory"));
     -+
      +	return memcpy(ret, str, len);
      +}
      +
     -+char *mem_pool_xstrndup(struct mem_pool *pool, const char *str, size_t len)
     ++char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len)
      +{
     -+	size_t minlen = strnlen(str, len);
     -+	char *ret = mem_pool_alloc(pool, minlen+1);
     -+
     -+	if (!ret)
     -+		die(_("mem_pool_xstrndup: out of memory"));
     ++	char *p = memchr(str, '\0', len);
     ++	size_t actual_len = (p ? p - str : len);
     ++	char *ret = mem_pool_alloc(pool, actual_len+1);
      +
     -+	ret[minlen] = '\0';
     -+	return memcpy(ret, str, minlen);
     ++	ret[actual_len] = '\0';
     ++	return memcpy(ret, str, actual_len);
      +}
      +
       int mem_pool_contains(struct mem_pool *mem_pool, void *mem)
     @@ mem-pool.h: void *mem_pool_alloc(struct mem_pool *pool, size_t len);
      +/*
      + * Allocate memory from the memory pool and copy str into it.
      + */
     -+char *mem_pool_xstrdup(struct mem_pool *pool, const char *str);
     -+char *mem_pool_xstrndup(struct mem_pool *pool, const char *str, size_t len);
     ++char *mem_pool_strdup(struct mem_pool *pool, const char *str);
     ++char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len);
      +
       /*
        * Move the memory associated with the 'src' pool to the 'dst' pool. The 'src'
 2:  e04ba96b22 = 2:  65f334f5cf mem-pool: use more standard initialization and finalization
 3:  616402c64e ! 3:  09976779c3 mem-pool: use consistent pool variable name

@@ mem-pool.c: void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len)
memset(r, 0, len);
return r;
}
-@@ mem-pool.c: char *mem_pool_xstrndup(struct mem_pool *pool, const char *str, size_t len)
- return memcpy(ret, str, minlen);
+@@ mem-pool.c: char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len)
+ return memcpy(ret, str, actual_len);
}

-int mem_pool_contains(struct mem_pool *mem_pool, void *mem)

gitgitgadget