mirror of
https://github.com/jart/cosmopolitan.git
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c843243322
- Support deterministic stacks on OpenBSD - Support OpenBSD system call origin verification - Fix overrun by one in chibicc string token allocator - Get all chibicc tests passing under Address Sanitizer
90 lines
3.8 KiB
C
90 lines
3.8 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(unsigned char *p) {
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return (uint64_t)p[7] << 070 | (uint64_t)p[6] << 060 | (uint64_t)p[5] << 050 |
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(uint64_t)p[4] << 040 | (uint64_t)p[3] << 030 | (uint64_t)p[2] << 020 |
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(uint64_t)p[1] << 010 | (uint64_t)p[0] << 000;
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}
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/**
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* Copies at most N bytes from SRC to DST until 𝑐 is encountered.
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*
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* This is little-known C Standard Library approach, dating back to the
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* Fourth Edition of System Five, for copying a C strings to fixed-width
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* buffers, with added generality.
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*
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* For example, strictly:
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*
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* char buf[16];
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* CHECK_NOTNULL(memccpy(buf, s, '\0', sizeof(buf)));
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*
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* Or unstrictly:
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*
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* if (!memccpy(buf, s, '\0', sizeof(buf))) strcpy(buf, "?");
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*
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* Are usually more sensible than the following:
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*
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* char cstrbuf[16];
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* snprintf(cstrbuf, sizeof(cstrbuf), "%s", CSTR);
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*
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* @param c is search character and is masked with 255
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* @return DST + idx(c) + 1, or NULL if 𝑐 ∉ 𝑠₀․․ₙ₋₁
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* @note DST and SRC can't overlap
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* @asyncsignalsafe
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*/
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void *memccpy(void *dst, const void *src, int c, size_t n) {
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size_t i;
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uint64_t v, w;
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unsigned char *d;
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unsigned char *pd;
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const unsigned char *s;
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i = 0;
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d = dst;
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s = src;
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c &= 255;
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v = 0x0101010101010101 * c;
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for (; (uintptr_t)(s + i) & 7; ++i) {
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if (i == n) return NULL;
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if ((d[i] = s[i]) == c) return d + i + 1;
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}
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for (; i + 8 <= n; i += 8) {
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w = UncheckedAlignedRead64(s + i);
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if (~(w ^ v) & ((w ^ v) - 0x0101010101010101) & 0x8080808080808080) {
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break;
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} else {
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pd = d + i;
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pd[0] = (w >> 000) & 255;
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pd[1] = (w >> 010) & 255;
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pd[2] = (w >> 020) & 255;
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pd[3] = (w >> 030) & 255;
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pd[4] = (w >> 040) & 255;
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pd[5] = (w >> 050) & 255;
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pd[6] = (w >> 060) & 255;
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pd[7] = (w >> 070) & 255;
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}
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}
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for (; i < n; ++i) {
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if ((d[i] = s[i]) == c) {
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return d + i + 1;
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}
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}
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return NULL;
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}
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