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author | mm <mm@FreeBSD.org> | 2010-05-10 06:59:50 +0000 |
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committer | mm <mm@FreeBSD.org> | 2010-05-10 06:59:50 +0000 |
commit | 5c358d45429b654efa9c8177ecd370a7965ec1a7 (patch) | |
tree | d2d916954c6a66a3168ee356b5f24da01c2017d6 /contrib/xz/src/liblzma/check/crc32_fast.c | |
parent | 3e09decd1986826f54af1a47be97bb87c1220783 (diff) | |
parent | 1008b7c6744a190c5b15aaf8cab1054671e4c7c3 (diff) | |
download | FreeBSD-src-5c358d45429b654efa9c8177ecd370a7965ec1a7.zip FreeBSD-src-5c358d45429b654efa9c8177ecd370a7965ec1a7.tar.gz |
Import of liblzma, xz, xzdec, lzmainfo from vendor branch
Add support for xz and lzma to lesspipe.sh (xzless, lzless)
Bump __FreeBSD_version
Approved by: delphij (mentor)
MFC after: 2 weeks
Diffstat (limited to 'contrib/xz/src/liblzma/check/crc32_fast.c')
-rw-r--r-- | contrib/xz/src/liblzma/check/crc32_fast.c | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/contrib/xz/src/liblzma/check/crc32_fast.c b/contrib/xz/src/liblzma/check/crc32_fast.c new file mode 100644 index 0000000..94da855 --- /dev/null +++ b/contrib/xz/src/liblzma/check/crc32_fast.c @@ -0,0 +1,82 @@ +/////////////////////////////////////////////////////////////////////////////// +// +/// \file crc32.c +/// \brief CRC32 calculation +/// +/// Calculate the CRC32 using the slice-by-eight algorithm. +/// It is explained in this document: +/// http://www.intel.com/technology/comms/perfnet/download/CRC_generators.pdf +/// The code in this file is not the same as in Intel's paper, but +/// the basic principle is identical. +// +// Author: Lasse Collin +// +// This file has been put into the public domain. +// You can do whatever you want with this file. +// +/////////////////////////////////////////////////////////////////////////////// + +#include "check.h" +#include "crc_macros.h" + + +// If you make any changes, do some bench marking! Seemingly unrelated +// changes can very easily ruin the performance (and very probably is +// very compiler dependent). +extern LZMA_API(uint32_t) +lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc) +{ + crc = ~crc; + +#ifdef WORDS_BIGENDIAN + crc = bswap32(crc); +#endif + + if (size > 8) { + // Fix the alignment, if needed. The if statement above + // ensures that this won't read past the end of buf[]. + while ((uintptr_t)(buf) & 7) { + crc = lzma_crc32_table[0][*buf++ ^ A(crc)] ^ S8(crc); + --size; + } + + // Calculate the position where to stop. + const uint8_t *const limit = buf + (size & ~(size_t)(7)); + + // Calculate how many bytes must be calculated separately + // before returning the result. + size &= (size_t)(7); + + // Calculate the CRC32 using the slice-by-eight algorithm. + while (buf < limit) { + crc ^= *(const uint32_t *)(buf); + buf += 4; + + crc = lzma_crc32_table[7][A(crc)] + ^ lzma_crc32_table[6][B(crc)] + ^ lzma_crc32_table[5][C(crc)] + ^ lzma_crc32_table[4][D(crc)]; + + const uint32_t tmp = *(const uint32_t *)(buf); + buf += 4; + + // At least with some compilers, it is critical for + // performance, that the crc variable is XORed + // between the two table-lookup pairs. + crc = lzma_crc32_table[3][A(tmp)] + ^ lzma_crc32_table[2][B(tmp)] + ^ crc + ^ lzma_crc32_table[1][C(tmp)] + ^ lzma_crc32_table[0][D(tmp)]; + } + } + + while (size-- != 0) + crc = lzma_crc32_table[0][*buf++ ^ A(crc)] ^ S8(crc); + +#ifdef WORDS_BIGENDIAN + crc = bswap32(crc); +#endif + + return ~crc; +} |