mirror of
https://github.com/jart/cosmopolitan.git
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59 lines
3.1 KiB
C
59 lines
3.1 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/str/str.h"
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static inline noasan uint64_t UncheckedAlignedRead64(const char *p) {
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return (uint64_t)(255 & p[7]) << 070 | (uint64_t)(255 & p[6]) << 060 |
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(uint64_t)(255 & p[5]) << 050 | (uint64_t)(255 & p[4]) << 040 |
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(uint64_t)(255 & p[3]) << 030 | (uint64_t)(255 & p[2]) << 020 |
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(uint64_t)(255 & p[1]) << 010 | (uint64_t)(255 & p[0]) << 000;
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}
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/**
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* Compares NUL-terminated strings.
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*
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* @param a is first non-null NUL-terminated string pointer
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* @param b is second non-null NUL-terminated string pointer
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* @return is <0, 0, or >0 based on uint8_t comparison
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* @asyncsignalsafe
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*/
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int strcmp(const char *a, const char *b) {
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size_t i = 0;
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uint64_t v, w, d;
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if (a == b) return 0;
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if (((uintptr_t)a & 7) == ((uintptr_t)b & 7)) {
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for (; (uintptr_t)(a + i) & 7; ++i) {
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if (a[i] != b[i] || !b[i]) {
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return (a[i] & 0xff) - (b[i] & 0xff);
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}
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}
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for (;; i += 8) {
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v = UncheckedAlignedRead64(a + i);
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w = UncheckedAlignedRead64(b + i);
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w = (v ^ w) | (~v & (v - 0x0101010101010101) & 0x8080808080808080);
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if (w) {
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i += (unsigned)__builtin_ctzll(w) >> 3;
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return (a[i] & 0xff) - (b[i] & 0xff);
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}
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}
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} else {
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while (a[i] == b[i] && b[i]) ++i;
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return (a[i] & 0xff) - (b[i] & 0xff);
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}
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}
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