pkg-utils: describe the case conversion macros in more detail.
PATCH 1/1 pkg-utils: describe the case conversion macros in more detail.
After the refactoring of the case conversion macros in dd5e620ac, the macro became even harder to understand. Improve this explanation a little so future generations can make sense of what we're doing here.
Cc Thomas De Schampheleire <[email protected]>
---
Very old patch that I forgot to push
--- package/pkg-utils.mk | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-)
package/pkg-utils.mk +18 -8
@@ -5,14 +5,24 @@ # ################################################################################ -# UPPERCASE Macro -- transform its argument to uppercase and replace dots and -# hyphens to underscores - -# Heavily inspired by the up macro from gmsl (http://gmsl.sf.net) -# This is approx 5 times faster than forking a shell and tr, and -# as this macro is used a lot it matters -# This works by creating translation character pairs (E.G. a:A b:B) -# and then looping though all of them running $(subst from,to,text) +# Case conversion macros. This is inspired by the 'up' macro from gmsl +# (http://gmsl.sf.net). It is optimised very heavily because these macros +# are used a lot. It is about 5 times faster than forking a shell and tr. +# +# The caseconvert-helper creates a definition of the case conversion macro. +# After expansion by the outer $(eval ), the UPPERCASE macro is defined as: +# $(strip $(eval __tmp := $(1)) $(eval __tmp := $(subst a,A,$(__tmp))) ... ) +# In other words, every letter is substituted one by one. +# +# The caseconvert-helper allows us to create this definition out of the +# [FROM] and [TO] lists, so we don't need to write down every substition +# manually. The uses of $ and $$ quoting are chosen in order to do as +# much expansion as possible up-front. +# +# Note that it would be possible to conceive a slightly more optimal +# implementation that avoids the use of __tmp, but that would be even +# more unreadable and is not worth the effort. + [FROM] := a b c d e f g h i j k l m n o p q r s t u v w x y z - . [TO] := A B C D E F G H I J K L M N O P Q R S T U V W X Y Z _ _
Signature · 1 line
2.1.1
PATCH 1/1 pkg-utils: describe the case conversion macros in more detail.
Arnout, All,
On 2014-10-14 11:23 +0200, Arnout Vandecappelle (Essensium/Mind) spake thusly:
Quoted 6 lines
After the refactoring of the case conversion macros in
dd5e620ac, the macro became even harder to understand. Improve this explanation a little so future generations can make sense of what we're doing here.Cc Thomas De Schampheleire <[email protected]>
Reviewed-by "Yann E. MORIN" <[email protected]>
Regards,
Yann E. MORIN.
Quoted 52 lines
---
Very old patch that I forgot to push--- package/pkg-utils.mk | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-)package/pkg-utils.mk +18
-8@@ -5,14 +5,24 @@ # ################################################################################ -# UPPERCASE Macro -- transform its argument to uppercase and replace dots and -# hyphens to underscores - -# Heavily inspired by the up macro from gmsl (http://gmsl.sf.net) -# This is approx 5 times faster than forking a shell and tr, and -# as this macro is used a lot it matters -# This works by creating translation character pairs (E.G. a:A b:B) -# and then looping though all of them running $(subst from,to,text) +# Case conversion macros. This is inspired by the 'up' macro from gmsl +# (http://gmsl.sf.net). It is optimised very heavily because these macros +# are used a lot. It is about 5 times faster than forking a shell and tr. +# +# The caseconvert-helper creates a definition of the case conversion macro. +# After expansion by the outer $(eval ), the UPPERCASE macro is defined as: +# $(strip $(eval __tmp := $(1)) $(eval __tmp := $(subst a,A,$(__tmp))) ... ) +# In other words, every letter is substituted one by one. +# +# The caseconvert-helper allows us to create this definition out of the +# [FROM] and [TO] lists, so we don't need to write down every substition +# manually. The uses of $ and $$ quoting are chosen in order to do as +# much expansion as possible up-front. +# +# Note that it would be possible to conceive a slightly more optimal +# implementation that avoids the use of __tmp, but that would be even +# more unreadable and is not worth the effort. + [FROM] := a b c d e f g h i j k l m n o p q r s t u v w x y z - . [TO] := A B C D E F G H I J K L M N O P Q R S T U V W X Y Z _ _Signature · 6 lines
2.1.1 _______________________________________________ buildroot mailing list buildroot at busybox.net http://lists.busybox.net/mailman/listinfo/buildroot
Signature · 6 lines
.-----------------.--------------------.------------------.--------------------. | Yann E. MORIN | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: | | +33 662 376 056 | Software Designer | \ / CAMPAIGN | ___ | | +33 223 225 172 `------------.-------: X AGAINST | \e/ There is no | | http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL | v conspiracy. | '------------------------------^-------^------------------^--------------------'
Thomas Petazzoni
AppliedPATCH 1/1 pkg-utils: describe the case conversion macros in more detail.
In reply to Arnout Vandecappelle (Essensium/Mind)Dear Arnout Vandecappelle (Essensium/Mind),
Quoted 6 lines · Arnout Vandecappelle (Essensium/Mind)
After the refactoring of the case conversion macros in
dd5e620ac, the macro became even harder to understand. Improve this explanation a little so future generations can make sense of what we're doing here.Cc Thomas De Schampheleire <[email protected]>
Applied, thanks.
Thomas
Signature · 3 lines
Thomas Petazzoni, CTO, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com