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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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60 lines
1.2 KiB
C
60 lines
1.2 KiB
C
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/*
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* CRC32 using the polynomial from IEEE-802.3
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*
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* Authors: Lasse Collin <lasse.collin@tukaani.org>
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* Igor Pavlov <http://7-zip.org/>
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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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* This is not the fastest implementation, but it is pretty compact.
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* The fastest versions of xz_crc32() on modern CPUs without hardware
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* accelerated CRC instruction are 3-5 times as fast as this version,
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* but they are bigger and use more memory for the lookup table.
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*/
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#include "xz_private.h"
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/*
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* STATIC_RW_DATA is used in the pre-boot environment on some architectures.
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* See <linux/decompress/mm.h> for details.
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*/
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#ifndef STATIC_RW_DATA
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# define STATIC_RW_DATA static
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#endif
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STATIC_RW_DATA uint32_t xz_crc32_table[256];
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XZ_EXTERN void xz_crc32_init(void)
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{
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const uint32_t poly = 0xEDB88320;
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uint32_t i;
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uint32_t j;
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uint32_t r;
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for (i = 0; i < 256; ++i) {
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r = i;
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for (j = 0; j < 8; ++j)
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r = (r >> 1) ^ (poly & ~((r & 1) - 1));
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xz_crc32_table[i] = r;
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}
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return;
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}
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XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
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{
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crc = ~crc;
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while (size != 0) {
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crc = xz_crc32_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
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--size;
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}
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return ~crc;
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}
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