musl - musl - an implementation of the standard library for Linux-based systems

musl - an implementation of the standard library for Linux-based systems

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author	Rich Felker <dalias@aerifal.cx>	2012年09月27日 17:19:09 -0400
committer	Rich Felker <dalias@aerifal.cx>	2012年09月27日 17:19:09 -0400
commit	68dbd05039f8b256f586ed9a589645fa3a1b7f5f (patch)
tree	b27c6d58c7be3e028276a4840e76187ccdfa9696 /src/string/strcspn.c
parent	3f9ff1514e49b06c20a61af9ae9e52bd53b48d9a (diff)
download	musl-68dbd05039f8b256f586ed9a589645fa3a1b7f5f.tar.gz

optimize strchrnul/strcspn not to scan string twice on no-match

when strchr fails, and important piece of information already computed, the string length, is thrown away. have strchrnul (with namespace protection) be the underlying function so this information can be kept, and let strchr be a wrapper for it. this also allows strcspn to be considerably faster in the case where the match set has a single element that's not matched.

Diffstat (limited to 'src/string/strcspn.c')

-rw-r--r--

src/string/strcspn.c

1 files changed, 3 insertions, 2 deletions

diff --git a/src/string/strcspn.c b/src/string/strcspn.c
index c843ff97..cfdba114 100644
--- a/src/string/strcspn.c
+++ b/src/string/strcspn.c

@@ -3,13 +3,14 @@

#define BITOP(a,b,op) \

((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))

+char *__strchrnul(const char *, int);

size_t strcspn(const char *s, const char *c)

{

const char *a = s;

size_t byteset[32/sizeof(size_t)];

- if (!c[0]) return strlen(s);

- if (!c[1]) return (s=strchr(s, *c)) ? s-a : strlen(a);

+ if (!c[0] || !c[1]) return __strchrnul(s, *c)-a;

memset(byteset, 0, sizeof byteset);

for (; *c && BITOP(byteset, *(unsigned char *)c, |=); c++);

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