text: #include <string.h>
  #undef strcspn
  
  size_t
  strcspn(const char *s1, const char *s2)
  {
  	const unsigned char *s = s1;
  	const unsigned char *accept = s2;
  	unsigned ch;
  	size_t n;
  	char buf[__NUMCHARS];
  
  	memset(buf, 0, sizeof(buf));
  	while (ch = *accept++)
  		buf[ch] = 1;
  
  	for (n = 0; (ch = *s++) && !buf[ch]; ++n)
  		;
  
  	return n;
  }
  