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add implementation of memccpy function

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This commit is contained in:
Rich Felker
2011-02-24 12:35:42 -05:00
parent 9f19b3ec8d
commit b8ff2aaabb
1 changed files with 32 additions and 0 deletions
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32
src/string/memccpy.c Normal file
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#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <limits.h>
#define ALIGN (sizeof(size_t)-1)
#define ONES ((size_t)-1/UCHAR_MAX)
#define HIGHS (ONES * (UCHAR_MAX/2+1))
#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
void *memccpy(void *dest, const void *src, int c, size_t n)
{
unsigned char *d = dest;
const unsigned char *s = src;
size_t *wd, k;
const size_t *ws;
c = (unsigned char)c;
if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
for (; ((uintptr_t)s & ALIGN) && n && (*d=*s)!=c; n--, s++, d++);
if ((uintptr_t)s & ALIGN) goto tail;
k = ONES * c;
wd=(void *)d; ws=(const void *)s;
for (; n>=sizeof(size_t) && !HASZERO(*ws^k);
n-=sizeof(size_t), ws++, *wd++) *wd = *ws;
d=(void *)wd; s=(const void *)ws;
}
for (; n && (*d=*s)!=c; n--, s++, d++);
tail:
if (*s==c) return d+1;
return 0;
}