48 lines
1.0 KiB
C
48 lines
1.0 KiB
C
enum { CRC_TABLE_SIZE = 0x100 };
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uint32_t
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crc_reflect(uint32_t input)
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{
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uint32_t reflected = 0;
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for (int 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
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crc_fill_table(uint32_t *table, int big, uint32_t polynomial)
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{
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uint32_t lsb = (big) ? 1 << 31 : 1; /* least significant bit */
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uint32_t poly = (big) ? polynomial : crc_reflect(polynomial);
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for (int c = 0; c < CRC_TABLE_SIZE; c++, table++) {
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*table = (big) ? c << 24 : c;
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for (int 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
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crc_be_cycle(uint32_t *table, uint32_t *remainder, char c)
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{
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uint32_t byte = table[(((*remainder) >> 24) ^ c) & 0xff];
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*remainder = (((*remainder) << 8) ^ byte) & 0xFFFFFFFF;
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}
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void
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crc_le_cycle(uint32_t *table, uint32_t *remainder, char c)
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{
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uint32_t byte = table[((*remainder) ^ c) & 0xFF];
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*remainder = ((*remainder) >> 8) ^ byte;
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}
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