ref: 4dd43534558d8e24534d263a3bc1ca748052af9a
dir: /lib/c/strspn.c/
#include <string.h> #undef strspn size_t strspn(const char *s1, const char *s2) { char buf[__NUMCHARS]; 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; }