87 lines
2.3 KiB
C
87 lines
2.3 KiB
C
/* Copyright 2022 the unarr project authors (see AUTHORS file).
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License: LGPLv3 */
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#include "unarr-imp.h"
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#if !defined HAVE_ZLIB || !defined USE_ZLIB_CRC
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/*
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crc32 calculation based on Intel slice-by-8 algorithm with lookup-table generation code
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adapted from https://gnunet.org/svn/gnunet/src/util/crypto_crc.c (public domain) */
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static inline uint32_t uint32le(const uint8_t *data) { return data[0] | data[1] << 8 | data[2] << 16 | (uint32_t)data[3] << 24; }
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static bool crc_table_ready = false;
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static uint32_t crc_table[8][256];
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uint32_t ar_crc32(uint32_t crc32, const uint8_t * data, size_t data_len)
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{
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if (!crc_table_ready) {
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static const uint32_t crc_poly = 0xEDB88320;
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uint32_t h = 1;
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crc_table[0][0] = 0;
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for (unsigned int i = 128; i; i >>= 1) {
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h = (h >> 1) ^ ((h & 1) ? crc_poly : 0);
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for (unsigned int j = 0; j < 256; j += 2 * i) {
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crc_table[0][i+j] = crc_table[0][j] ^ h;
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}
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}
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for (unsigned int i = 0; i < 256; i++) {
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for (unsigned int j = 1; j < 8; j++) {
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crc_table[j][i] = (crc_table[j-1][i] >> 8) ^ crc_table[0][crc_table[j-1][i] & 0xFF];
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}
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}
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crc_table_ready = true;
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}
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crc32 ^= 0xFFFFFFFF;
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while (data_len >= 8) {
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uint32_t tmp = crc32 ^ uint32le(data);
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crc32 = crc_table[7][ tmp & 0xFF ] ^
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crc_table[6][(tmp >> 8) & 0xFF ] ^
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crc_table[5][(tmp >> 16) & 0xFF ] ^
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crc_table[4][ tmp >> 24 ];
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tmp = uint32le(data + 4);
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crc32 ^= crc_table[3][tmp & 0xFF] ^
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crc_table[2][(tmp >> 8) & 0xFF] ^
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crc_table[1][(tmp >> 16) & 0xFF] ^
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crc_table[0][ tmp >> 24 ];
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data += 8;
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data_len -= 8;
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}
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while (data_len-- > 0) {
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crc32 = (crc32 >> 8) ^ crc_table[0][(crc32 ^ *data++) & 0xFF];
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}
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return crc32 ^ 0xFFFFFFFF;
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}
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#else
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#include <zlib.h>
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uint32_t ar_crc32(uint32_t crc, const unsigned char *data, size_t data_len)
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{
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#if SIZE_MAX > UINT32_MAX
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while (data_len > UINT32_MAX) {
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crc = crc32(crc, data, UINT32_MAX);
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data += UINT32_MAX;
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data_len -= UINT32_MAX;
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}
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#endif
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return crc32(crc, data, (uint32_t)data_len);
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}
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#endif
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