70 lines
1.3 KiB
C
70 lines
1.3 KiB
C
enum { CRC_TABLE_SIZE = 0x100 };
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static inline 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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static inline void
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crc_be_fill_table(uint32_t *table, uint32_t polynomial)
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{
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const uint32_t lsb = 1 << 31;
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uint32_t poly = polynomial;
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for (int c = 0; c < CRC_TABLE_SIZE; c++, table++) {
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uint32_t v = c << 24;
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for (int i = 0; i < 8; i++) {
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if (v & lsb) {
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v <<= 1;
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v ^= poly;
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} else {
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v <<= 1;
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}
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}
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*table = v;
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}
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}
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static inline void
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crc_le_fill_table(uint32_t *table, uint32_t polynomial)
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{
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const uint32_t lsb = 1;
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uint32_t poly = crc_reflect(polynomial);
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for (int c = 0; c < CRC_TABLE_SIZE; c++, table++) {
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uint32_t v = c;
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for (int i = 0; i < 8; i++) {
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if (v & lsb) {
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v >>= 1;
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v ^= poly;
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} else {
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v >>= 1;
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}
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}
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*table = v;
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}
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}
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static inline void
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crc_be_cycle(uint32_t *table, uint32_t *remainder, uint8_t c)
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{
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const uint8_t i = ((*remainder) >> 24) ^ c;
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const uint32_t next = table[i];
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*remainder = ((*remainder) << 8) ^ next;
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}
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static inline void
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crc_le_cycle(uint32_t *table, uint32_t *remainder, uint8_t c)
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{
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const uint8_t i = (*remainder) ^ c;
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const uint32_t next = table[i];
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*remainder = ((*remainder) >> 8) ^ next;
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}
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