| | 1 | #include <stdint.h> |
| | 2 | |
| | 3 | /* code from http://www.faqs.org/faqs/compression-faq/part1/section-26.html, |
| | 4 | * presumed public domain */ |
| | 5 | |
| | 6 | uint32_t crc32_table[256]; |
| | 7 | |
| | 8 | uint32_t crc32(uint8_t *buf, int len, uint32_t crc0) |
| | 9 | { |
| | 10 | uint8_t *p; |
| | 11 | uint32_t crc; |
| | 12 | |
| | 13 | crc = crc0; |
| | 14 | for (p = buf; len > 0; ++p, --len) |
| | 15 | crc = (crc << 8) ^ crc32_table[(crc >> 24) ^ *p]; |
| | 16 | return crc; |
| | 17 | } |
| | 18 | |
| | 19 | /* |
| | 20 | * Build auxiliary table for parallel byte-at-a-time CRC-32. |
| | 21 | */ |
| | 22 | #define CRC32_POLY 0x04c11db7 /* AUTODIN II, Ethernet, & FDDI */ |
| | 23 | |
| | 24 | void crc32_init() |
| | 25 | { |
| | 26 | int i, j; |
| | 27 | uint32_t c; |
| | 28 | |
| | 29 | for (i = 0; i < 256; ++i) { |
| | 30 | for (c = i << 24, j = 8; j > 0; --j) |
| | 31 | c = c & 0x80000000 ? (c << 1) ^ CRC32_POLY : (c << 1); |
| | 32 | crc32_table[i] = c; |
| | 33 | } |
| | 34 | } |
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