ref: 3f7e54a705c0f7a6e6807285e00167f2af5e3d88
dir: /lib/c/strcspn.c/
#include <string.h> #undef strcspn size_t strcspn(const char *s1, const char *s2) { char buf[128]; 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; }