mirror of
https://github.com/jart/cosmopolitan.git
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81 lines
4.1 KiB
C
81 lines
4.1 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 2021 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/intrin/bits.h"
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#include "libc/zip.h"
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typedef char v16qi __attribute__((__vector_size__(16)));
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typedef short v8hi __attribute__((__vector_size__(16)));
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typedef long long v2di __attribute__((__vector_size__(16), __aligned__(1)));
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/**
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* Locates End Of Central Directory record in ZIP file.
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*
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* The ZIP spec says this header can be anywhere in the last 64kb. We
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* search it backwards for the ZIP-64 "PK♠•" magic number. If that's not
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* found, then we search again for the original "PK♣♠" magnum. The
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* caller needs to check the first four bytes of the returned value to
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* determine whether to use ZIP_CDIR_xxx() or ZIP_CDIR64_xxx() macros.
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*
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* @param p points to file memory
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* @param n is byte size of file
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* @return pointer to EOCD64 or EOCD, or NULL if not found
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*/
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void *GetZipCdir(const uint8_t *p, size_t n) {
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v2di x;
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size_t i, j;
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uint32_t magic;
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i = n - 4;
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do {
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#ifdef __x86_64__
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v8hi pk = {READ16LE("PK"), READ16LE("PK"), READ16LE("PK"), READ16LE("PK"),
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READ16LE("PK"), READ16LE("PK"), READ16LE("PK"), READ16LE("PK")};
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asm("" : "+x"(pk));
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if (i >= 14) {
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x = *(const v2di *)(p + i - 14);
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if (!(__builtin_ia32_pmovmskb128(
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(v16qi)__builtin_ia32_pcmpeqw128((v8hi)x, pk)) |
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__builtin_ia32_pmovmskb128((v16qi)__builtin_ia32_pcmpeqw128(
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(v8hi)__builtin_ia32_psrldqi128(x, 8), pk)))) {
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i -= 13;
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continue;
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}
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}
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#endif
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while (magic = READ32LE(p + i), magic != kZipCdir64LocatorMagic &&
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magic != kZipCdirHdrMagic &&
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i + 0x10000 + 0x1000 >= n && i > 0) {
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--i;
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}
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if (magic == kZipCdir64LocatorMagic && i + kZipCdir64LocatorSize <= n &&
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IsZipCdir64(p, n, ZIP_LOCATE64_OFFSET(p + i))) {
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return p + ZIP_LOCATE64_OFFSET(p + i);
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} else if (magic == kZipCdirHdrMagic && IsZipCdir32(p, n, i)) {
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j = i;
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do {
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if (READ32LE(p + j) == kZipCdir64LocatorMagic &&
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j + kZipCdir64LocatorSize <= n &&
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IsZipCdir64(p, n, ZIP_LOCATE64_OFFSET(p + j))) {
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return p + ZIP_LOCATE64_OFFSET(p + j);
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}
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} while (j-- && i - j < 128);
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return p + i;
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}
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} while (i > 0 && i-- + 0x10000 + 0x1000 >= n);
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return 0;
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}
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