28 lines
697 B
C
28 lines
697 B
C
#include <string.h>
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#include <stdint.h>
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#include <limits.h>
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#define SS (sizeof(size_t))
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#define ALIGN (sizeof(size_t)-1)
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#define ONES ((size_t)-1/UCHAR_MAX)
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#define HIGHS (ONES * (UCHAR_MAX/2+1))
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#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
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void *memchr(const void *src, int c, size_t n)
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{
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const unsigned char *s = src;
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c = (unsigned char)c;
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#ifdef __GNUC__
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for (; ((uintptr_t)s & ALIGN) && n && *s != c; s++, n--);
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if (n && *s != c) {
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typedef size_t __attribute__((__may_alias__)) word;
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const word *w;
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size_t k = ONES * c;
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for (w = (const void *)s; n>=SS && !HASZERO(*w^k); w++, n-=SS);
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s = (const void *)w;
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}
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#endif
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for (; n && *s != c; s++, n--);
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return n ? (void *)s : 0;
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}
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