cosmopolitan/libc/intrin/strnlen.c
Justine Tunney 7e0a09feec
Mint APE Loader v1.5
This change ports APE Loader to Linux AARCH64, so that Raspberry Pi
users can run programs like redbean, without the executable needing
to modify itself. Progress has also slipped into this change on the
issue of making progress better conforming to user expectations and
industry standards regarding which symbols we're allowed to declare
2023-07-26 13:54:49 -07:00

61 lines
2.8 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/assert.h"
#include "libc/dce.h"
#include "libc/intrin/asan.internal.h"
#include "libc/intrin/bits.h"
#include "libc/str/str.h"
#ifndef __aarch64__
static dontasan size_t strnlen_x64(const char *s, size_t n, size_t i) {
uint64_t w;
for (; i + 8 < n; i += 8) {
w = *(uint64_t *)(s + i);
if ((w = ~w & (w - 0x0101010101010101) & 0x8080808080808080)) {
i += (unsigned)__builtin_ctzll(w) >> 3;
break;
}
}
return i;
}
/**
* Returns length of NUL-terminated string w/ limit.
*
* @param s is string
* @param n is max length
* @return byte length
* @asyncsignalsafe
*/
dontasan size_t strnlen(const char *s, size_t n) {
size_t i;
if (IsAsan() && n) __asan_verify(s, 1);
for (i = 0; (uintptr_t)(s + i) & 7; ++i) {
if (i == n || !s[i]) return i;
}
i = strnlen_x64(s, n, i);
for (;; ++i) {
if (i == n || !s[i]) break;
}
unassert(i == n || (i < n && !s[i]));
if (IsAsan()) __asan_verify(s, i);
return i;
}
#endif /* __aarch64__ */