com32/lib/strspn.c

   1 /*
   2  * strspn, strcspn
   3  */
   4
   5 #include <string.h>
   6 #include <stddef.h>
   7 #include <inttypes.h>
   8 #include <limits.h>
   9
  10 #ifndef LONG_BIT
  11 #define LONG_BIT (CHAR_BIT*sizeof(long))
  12 #endif
  13
  14 static void set_bit(unsigned long *bitmap, unsigned int bit)
  15 {
  16     bitmap[bit / LONG_BIT] |= 1UL << (bit % LONG_BIT);
  17 }
  18
  19 static int test_bit(unsigned long *bitmap, unsigned int bit)
  20 {
  21     return (int)(bitmap[bit / LONG_BIT] >> (bit % LONG_BIT)) & 1;
  22 }
  23
  24 static size_t strxspn(const char *s, const char *map, int parity)
  25 {
  26     unsigned long matchmap[((1 << CHAR_BIT) + LONG_BIT - 1) / LONG_BIT];
  27     size_t n = 0;
  28
  29     /* Create bitmap */
  30     memset(matchmap, 0, sizeof matchmap);
  31     while (*map)
  32         set_bit(matchmap, (unsigned char)*map++);
  33
  34     /* Make sure the null character never matches */
  35     if (parity)
  36         set_bit(matchmap, 0);
  37
  38     /* Calculate span length */
  39     while (test_bit(matchmap, (unsigned char)*s++) ^ parity)
  40         n++;
  41
  42     return n;
  43 }
  44
  45 size_t strspn(const char *s, const char *accept)
  46 {
  47     return strxspn(s, accept, 0);
  48 }
  49
  50 size_t strcspn(const char *s, const char *reject)
  51 {
  52     return strxspn(s, reject, 1);
  53 }
  54
  55 char *strpbrk(const char *s, const char *accept)
  56 {
  57     const char *ss = s + strxspn(s, accept, 1);
  58
  59     return *ss ? (char *)ss : NULL;
  60 }