48 lines
990 B
C
48 lines
990 B
C
#include "crc32.h"
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/* CRC-32/IEEE 802.3 查表实现（表在首次使用时生成，避免占用 Flash） */
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static uint32_t crc32_table[256];
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static uint8_t crc32_table_ready = 0;
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static void crc32_build_table(void)
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{
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for (uint32_t i = 0; i < 256; i++)
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{
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uint32_t c = i;
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for (uint32_t k = 0; k < 8; k++)
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{
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c = (c & 1U) ? (0xEDB88320UL ^ (c >> 1)) : (c >> 1);
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}
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crc32_table[i] = c;
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}
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crc32_table_ready = 1;
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}
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uint32_t crc32_init(void)
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{
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return 0xFFFFFFFFUL;
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}
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uint32_t crc32_update(uint32_t crc, const uint8_t *data, uint32_t len)
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{
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if (!crc32_table_ready)
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{
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crc32_build_table();
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}
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while (len--)
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{
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crc = crc32_table[(crc ^ *data++) & 0xFFU] ^ (crc >> 8);
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}
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return crc;
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}
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uint32_t crc32_final(uint32_t crc)
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{
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return crc ^ 0xFFFFFFFFUL;
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}
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uint32_t crc32_compute(const uint8_t *data, uint32_t len)
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{
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return crc32_final(crc32_update(crc32_init(), data, len));
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}
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