35 lines
920 B
C
35 lines
920 B
C
#include <string.h>
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#include <stdint.h>
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#include <limits.h>
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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 *memccpy(void *restrict dest, const void *restrict src, int c, size_t n)
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{
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unsigned char *d = dest;
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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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typedef size_t __attribute__((__may_alias__)) word;
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word *wd;
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const word *ws;
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if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
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for (; ((uintptr_t)s & ALIGN) && n && (*d=*s)!=c; n--, s++, d++);
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if ((uintptr_t)s & ALIGN) goto tail;
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size_t k = ONES * c;
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wd=(void *)d; ws=(const void *)s;
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for (; n>=sizeof(size_t) && !HASZERO(*ws^k);
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n-=sizeof(size_t), ws++, wd++) *wd = *ws;
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d=(void *)wd; s=(const void *)ws;
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}
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#endif
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for (; n && (*d=*s)!=c; n--, s++, d++);
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tail:
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if (n) return d+1;
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return 0;
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}
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