mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 11:37:35 +00:00
47 lines
2.7 KiB
C
47 lines
2.7 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
|
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
|
|
╞══════════════════════════════════════════════════════════════════════════════╡
|
|
│ Copyright 2021 Justine Alexandra Roberts Tunney │
|
|
│ │
|
|
│ Permission to use, copy, modify, and/or distribute this software for │
|
|
│ any purpose with or without fee is hereby granted, provided that the │
|
|
│ above copyright notice and this permission notice appear in all copies. │
|
|
│ │
|
|
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
|
|
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
|
|
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
|
|
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
|
|
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
|
|
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
|
|
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
|
|
│ PERFORMANCE OF THIS SOFTWARE. │
|
|
╚─────────────────────────────────────────────────────────────────────────────*/
|
|
#include "libc/str/str.h"
|
|
|
|
/**
|
|
* Returns pointer to first instance of character.
|
|
*
|
|
* @param m is memory to search
|
|
* @param c is search byte which is masked with 255
|
|
* @param n is byte length of p
|
|
* @return is pointer to first instance of c or NULL if not found
|
|
* @asyncsignalsafe
|
|
*/
|
|
void *memchr(const void *m, int c, size_t n) {
|
|
uint64_t v, w;
|
|
const unsigned char *p, *pe;
|
|
c &= 255;
|
|
v = 0x0101010101010101 * c;
|
|
for (p = (const unsigned char *)m, pe = p + n; p + 8 <= pe; p += 8) {
|
|
w = (uint64_t)p[7] << 070 | (uint64_t)p[6] << 060 | (uint64_t)p[5] << 050 |
|
|
(uint64_t)p[4] << 040 | (uint64_t)p[3] << 030 | (uint64_t)p[2] << 020 |
|
|
(uint64_t)p[1] << 010 | (uint64_t)p[0] << 000;
|
|
if ((w = ~(w ^ v) & ((w ^ v) - 0x0101010101010101) & 0x8080808080808080)) {
|
|
return p + ((unsigned)__builtin_ctzll(w) >> 3);
|
|
}
|
|
}
|
|
for (; p < pe; ++p) {
|
|
if (*p == c) return p;
|
|
}
|
|
return NULL;
|
|
}
|