54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
/* Copyright (C) 2012 Connor Olding
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*
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* This program is licensed under the terms of the MIT License, and
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* is distributed without any warranty. You should have received a
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* copy of the license along with this program; see the file LICENSE.
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*/
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typedef unsigned long ulong;
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#include "crc32.h"
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ulong crc_reflect(ulong input)
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{
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ulong reflected = 0;
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int i;
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for (i = 0; i < 4 * 8; i++) {
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reflected <<= 1;
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reflected |= input & 1;
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input >>= 1;
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}
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return reflected;
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}
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void crc_fill_table(ulong *table, int big, ulong polynomial)
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{
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ulong lsb = (big) ? 1 << 31 : 1; /* least significant bit */
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ulong poly = (big) ? polynomial : crc_reflect(polynomial);
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int c, i;
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for (c = 0; c < CRC_TABLE_SIZE; c++, table++) {
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*table = (big) ? c << 24 : c;
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for (i = 0; i < 8; i++) {
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if (*table & lsb) {
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*table = (big) ? *table << 1 : *table >> 1;
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*table ^= poly;
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} else {
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*table = (big) ? *table << 1 : *table >> 1;
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}
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*table &= 0xFFFFFFFF;
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}
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}
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}
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void crc_be_cycle(ulong *table, ulong *remainder, char c)
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{
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ulong byte = table[((*remainder) >> 24) ^ c];
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*remainder = (((*remainder) << 8) ^ byte) & 0xFFFFFFFF;
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}
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void crc_le_cycle(ulong *table, ulong *remainder, char c)
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{
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ulong byte = table[((*remainder) ^ c) & 0xFF];
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*remainder = ((*remainder) >> 8) ^ byte;
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}
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