60 lines
2.8 KiB
C
60 lines
2.8 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/bits/safemacros.h"
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#include "libc/nexgen32e/crc32.h"
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#include "libc/nexgen32e/x86feature.h"
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static uint32_t kCrc32Tab[256];
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/**
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* Computes Phil Katz CRC-32 used by zip/zlib/gzip/etc.
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*
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* x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1
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* 0b100000100110000010001110110110111
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* bitreverse32(0x104c11db7)
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*
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* @param h is initial value
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*/
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uint32_t crc32_z(uint32_t h, const void *data, size_t size) {
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const unsigned char *p, *pe;
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static bool once;
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size_t skip;
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if (!once) {
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crc32init(kCrc32Tab, 0xedb88320);
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once = true;
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}
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if (data) {
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h ^= 0xffffffff;
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if (size >= 64 && X86_HAVE(PCLMUL)) {
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h = crc32$pclmul(h, data, size); /* 51x faster */
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skip = rounddown(size, 16);
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} else {
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skip = 0;
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}
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p = (const unsigned char *)data + skip;
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pe = (const unsigned char *)data + size;
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while (p < pe) {
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h = h >> 8 ^ kCrc32Tab[(h & 0xff) ^ *p++];
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}
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return h ^ 0xffffffff;
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} else {
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return 0;
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}
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}
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