cosmopolitan/libc/str/strcpy.c

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/*-*- 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 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/intrin/pcmpeqb.h"
#include "libc/intrin/pmovmskb.h"
#include "libc/limits.h"
#include "libc/nexgen32e/bsf.h"
#include "libc/str/str.h"
/**
* Copies bytes from 𝑠 to 𝑑 until a NUL is encountered.
*
* @param 𝑑 is destination memory
* @param 𝑠 is a NUL-terminated string
* @note 𝑑 and 𝑠 can't overlap
* @return original dest
* @see memccpy()
* @asyncsignalsafe
*/
char *strcpy(char *d, const char *s) {
size_t i;
uint8_t v1[16], v2[16], vz[16];
i = 0;
while (((uintptr_t)(s + i) & 15)) {
if (!(d[i] = s[i])) {
return d;
}
++i;
}
for (;;) {
memset(vz, 0, 16);
memcpy(v1, s + i, 16);
pcmpeqb(v2, v1, vz);
if (!pmovmskb(v2)) {
memcpy(d + i, v1, 16);
i += 16;
} else {
break;
}
}
for (;;) {
if (!(d[i] = s[i])) {
return d;
}
++i;
}
}