ref: 5310badb8f39560835f0db678d6784217c92766f
dir: /lib/c/strcspn.c/
#include <string.h> #undef strcspn size_t strcspn(const char *s1, const char *s2) { char buf[256]; unsigned char ch; size_t n; memset(buf, 0, sizeof(buf)); while (ch = *s2++) buf[ch] = 1; for (n = 0; (ch = *s1++) && !buf[ch]; ++n) ; return n; }