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 inline void
  15 set_bit(unsigned long *bitmap, unsigned int bit)
  16 {
  17   bitmap[bit/LONG_BIT] |= 1UL << (bit%LONG_BIT);
  18 }
  19
  20 static inline int
  21 test_bit(unsigned long *bitmap, unsigned int bit)
  22 {
  23   return (int)(bitmap[bit/LONG_BIT] >> (bit%LONG_BIT)) & 1;
  24 }
  25
  26 static size_t
  27 strxspn(const char *s, const char *map, int parity)
  28 {
  29   unsigned long matchmap[((1 << CHAR_BIT)+LONG_BIT-1)/LONG_BIT];
  30   size_t n = 0;
  31
  32   /* Create bitmap */
  33   memset(matchmap, 0, sizeof matchmap);
  34   while ( *map )
  35     set_bit(matchmap, (unsigned char) *map++);
  36
  37   /* Make sure the null character never matches */
  38   if ( parity )
  39     set_bit(matchmap, 0);
  40
  41   /* Calculate span length */
  42   while ( test_bit(matchmap, (unsigned char) *s++)^parity )
  43     n++;
  44
  45   return n;
  46 }
  47
  48 size_t
  49 strspn(const char *s, const char *accept)
  50 {
  51   return strxspn(s, accept, 0);
  52 }
  53
  54 size_t
  55 strcspn(const char *s, const char *reject)
  56 {
  57   return strxspn(s, reject, 1);
  58 }
  59
  60 char *
  61 strpbrk(const char *s, const char *accept)
  62 {
  63   const char *ss = s+strxspn(s, accept, 1);
  64
  65   return *ss ? (char *)ss : NULL;
  66 }