68 lines
1.2 KiB
C
68 lines
1.2 KiB
C
/*
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* strspn, strcspn
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*/
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#include <string.h>
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#include <stddef.h>
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#include <inttypes.h>
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#include <limits.h>
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#ifndef LONG_BIT
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#define LONG_BIT (CHAR_BIT*sizeof(long))
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#endif
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static inline void
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set_bit(unsigned long *bitmap, unsigned int bit)
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{
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bitmap[bit/LONG_BIT] |= 1UL << (bit%LONG_BIT);
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}
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static inline int
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test_bit(unsigned long *bitmap, unsigned int bit)
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{
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return (int)(bitmap[bit/LONG_BIT] >> (bit%LONG_BIT)) & 1;
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}
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static size_t
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strxspn(const char *s, const char *map, int parity)
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{
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unsigned long matchmap[((1 << CHAR_BIT)+LONG_BIT-1)/LONG_BIT];
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size_t n = 0;
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/* Create bitmap */
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memset(matchmap, 0, sizeof matchmap);
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while ( *map )
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set_bit(matchmap, (unsigned char) *map++);
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/* Make sure the null character never matches */
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if ( parity )
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set_bit(matchmap, 0);
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/* Calculate span length */
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while ( test_bit(matchmap, (unsigned char) *s++)^parity )
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n++;
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return n;
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}
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size_t
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strspn(const char *s, const char *accept)
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{
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return strxspn(s, accept, 0);
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}
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size_t
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strcspn(const char *s, const char *reject)
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{
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return strxspn(s, reject, 1);
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}
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char *
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strpbrk(const char *s, const char *accept)
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{
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const char *ss = s+strxspn(s, accept, 1);
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return *ss ? (char *)ss : NULL;
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}
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