path: root/src/string/strcspn.c
diff options
authorRich Felker <>2012-09-27 17:19:09 -0400
committerRich Felker <>2012-09-27 17:19:09 -0400
commit68dbd05039f8b256f586ed9a589645fa3a1b7f5f (patch)
treeb27c6d58c7be3e028276a4840e76187ccdfa9696 /src/string/strcspn.c
parent3f9ff1514e49b06c20a61af9ae9e52bd53b48d9a (diff)
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')
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++);