git.joshuawise.com / netwatch.git / blame
| Commit | Line | Data |
|---|---|---|
| 74032dae JW |
1 | #include <stdint.h> |
| 2 | ||
| 3 | /* code from http://www.faqs.org/faqs/compression-faq/part1/section-26.html, | |
| 4 | * presumed public domain */ | |
| 5 | ||
| db9fad13 | 6 | static uint32_t crc32_table[256]; |
| 74032dae | 7 | |
| f2da68c5 | 8 | uint32_t crc32(uint8_t *buf, int len, uint32_t crc0) |
| 74032dae JW |
9 | { |
| 10 | uint8_t *p; | |
| 11 | uint32_t crc; | |
| 12 | ||
| f2da68c5 | 13 | crc = crc0; |
| 74032dae JW |
14 | for (p = buf; len > 0; ++p, --len) |
| 15 | crc = (crc << 8) ^ crc32_table[(crc >> 24) ^ *p]; | |
| f2da68c5 | 16 | return crc; |
| 74032dae JW |
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 | } |