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/* ************************************************************************** */
/* */
/* ::: :::::::: */
/* ft_memchr.c :+: :+: :+: */
/* +:+ +:+ +:+ */
/* By: cacharle <marvin@42.fr> +#+ +:+ +#+ */
/* +#+#+#+#+#+ +#+ */
/* Created: 2019/10/07 09:55:31 by cacharle #+# #+# */
/* Updated: 2020/02/13 04:28:00 by cacharle ### ########.fr */
/* */
/* ************************************************************************** */
#include "libft.h"
/*
** Determining if a long word contain byte n
**
** xor all bytes with n, then check for zero byte like in ft_strlen.
*/
#define HIMAGIC 0x8080808080808080L
#define LOMAGIC 0x0101010101010101L
void *ft_memchr(const void *s, int c, size_t n)
{
uint64_t buf;
uint64_t lw;
c = (uint8_t)c;
while (((uint64_t)s & 0b111) != 0)
{
n--;
if (*(uint8_t*)s == (uint8_t)c)
return ((uint8_t*)s);
s++;
}
buf = (uint64_t)c | (uint64_t)c << 8 | (uint64_t)c << 16
| (uint64_t)c << 24 | (uint64_t)c << 32 | (uint64_t)c << 40
| (uint64_t)c << 48 | (uint64_t)c << 56;
while (n >= 8)
{
lw = *(uint64_t*)s ^ buf;
if ((lw - LOMAGIC) & ~lw & HIMAGIC)
break;
n -= 8;
s += 8;
}
while (n > 0)
{
if (*(uint8_t*)s == (uint8_t)c)
return ((uint8_t*)s);
n--;
s++;
}
return (NULL);
}
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