73 lines
1.6 KiB
C
73 lines
1.6 KiB
C
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///////////////////////////////////////////////////////////////////////////////
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//
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/// \file crc64.c
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/// \brief CRC64 calculation
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///
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/// Calculate the CRC64 using the slice-by-four algorithm. This is the same
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/// idea that is used in crc32_fast.c, but for CRC64 we use only four tables
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/// instead of eight to avoid increasing CPU cache usage.
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//
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// Author: Lasse Collin
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "check.h"
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#include "crc_macros.h"
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#ifdef WORDS_BIGENDIAN
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# define A1(x) ((x) >> 56)
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#else
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# define A1 A
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#endif
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// See the comments in crc32_fast.c. They aren't duplicated here.
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extern LZMA_API(uint64_t)
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lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
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{
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crc = ~crc;
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#ifdef WORDS_BIGENDIAN
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crc = bswap64(crc);
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#endif
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if (size > 4) {
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while ((uintptr_t)(buf) & 3) {
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crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);
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--size;
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}
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const uint8_t *const limit = buf + (size & ~(size_t)(3));
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size &= (size_t)(3);
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while (buf < limit) {
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#ifdef WORDS_BIGENDIAN
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const uint32_t tmp = (crc >> 32)
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^ *(const uint32_t *)(buf);
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#else
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const uint32_t tmp = crc ^ *(const uint32_t *)(buf);
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#endif
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buf += 4;
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crc = lzma_crc64_table[3][A(tmp)]
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^ lzma_crc64_table[2][B(tmp)]
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^ S32(crc)
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^ lzma_crc64_table[1][C(tmp)]
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^ lzma_crc64_table[0][D(tmp)];
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}
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}
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while (size-- != 0)
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crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);
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#ifdef WORDS_BIGENDIAN
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crc = bswap64(crc);
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#endif
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return ~crc;
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}
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