diff options
Diffstat (limited to 'src/string/strspn.c')
-rw-r--r-- | src/string/strspn.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/src/string/strspn.c b/src/string/strspn.c new file mode 100644 index 00000000..59b063e5 --- /dev/null +++ b/src/string/strspn.c @@ -0,0 +1,22 @@ +#include <string.h> + +#define BITOP(a,b,op) \ + ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a)))) + +size_t strspn(const char *_s, const char *_c) +{ + const unsigned char *s = _s; + const unsigned char *c = _c; + const unsigned char *a = s; + size_t byteset[32/sizeof(size_t)] = { 0 }; + + if (!c[0]) return 0; + if (!c[1]) { + for (; *s == *c; s++); + return s-a; + } + + for (; *c && BITOP(byteset, *c, |=); c++); + for (; *s && BITOP(byteset, *s, &); s++); + return s-a; +} |