Colin Cross | 28fa5bc | 2012-05-20 13:28:05 -0700 | [diff] [blame] | 1 | /*- |
| 2 | * COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or |
| 3 | * code or tables extracted from it, as desired without restriction. |
| 4 | */ |
| 5 | |
| 6 | /* |
| 7 | * First, the polynomial itself and its table of feedback terms. The |
| 8 | * polynomial is |
| 9 | * X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 |
| 10 | * |
| 11 | * Note that we take it "backwards" and put the highest-order term in |
| 12 | * the lowest-order bit. The X^32 term is "implied"; the LSB is the |
| 13 | * X^31 term, etc. The X^0 term (usually shown as "+1") results in |
| 14 | * the MSB being 1 |
| 15 | * |
| 16 | * Note that the usual hardware shift register implementation, which |
| 17 | * is what we're using (we're merely optimizing it by doing eight-bit |
| 18 | * chunks at a time) shifts bits into the lowest-order term. In our |
| 19 | * implementation, that means shifting towards the right. Why do we |
| 20 | * do it this way? Because the calculated CRC must be transmitted in |
| 21 | * order from highest-order term to lowest-order term. UARTs transmit |
| 22 | * characters in order from LSB to MSB. By storing the CRC this way |
| 23 | * we hand it to the UART in the order low-byte to high-byte; the UART |
| 24 | * sends each low-bit to hight-bit; and the result is transmission bit |
| 25 | * by bit from highest- to lowest-order term without requiring any bit |
| 26 | * shuffling on our part. Reception works similarly |
| 27 | * |
| 28 | * The feedback terms table consists of 256, 32-bit entries. Notes |
| 29 | * |
| 30 | * The table can be generated at runtime if desired; code to do so |
| 31 | * is shown later. It might not be obvious, but the feedback |
| 32 | * terms simply represent the results of eight shift/xor opera |
| 33 | * tions for all combinations of data and CRC register values |
| 34 | * |
| 35 | * The values must be right-shifted by eight bits by the "updcrc |
| 36 | * logic; the shift must be unsigned (bring in zeroes). On some |
| 37 | * hardware you could probably optimize the shift in assembler by |
| 38 | * using byte-swap instructions |
| 39 | * polynomial $edb88320 |
| 40 | * |
| 41 | * |
| 42 | * CRC32 code derived from work by Gary S. Brown. |
| 43 | */ |
| 44 | |
| 45 | /* Code taken from FreeBSD 8 */ |
| 46 | #include <stdint.h> |
Jerry Zhang | 5a75507 | 2018-06-12 16:18:53 -0700 | [diff] [blame] | 47 | #include <stdio.h> |
Colin Cross | 28fa5bc | 2012-05-20 13:28:05 -0700 | [diff] [blame] | 48 | |
| 49 | static uint32_t crc32_tab[] = { |
Jerry Zhang | 7b444f0 | 2018-06-12 16:42:09 -0700 | [diff] [blame] | 50 | 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3, |
| 51 | 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, |
| 52 | 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, |
| 53 | 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, |
| 54 | 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, |
| 55 | 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, |
| 56 | 0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f, |
| 57 | 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, |
| 58 | 0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433, |
| 59 | 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01, |
| 60 | 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, |
| 61 | 0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, |
| 62 | 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, |
| 63 | 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, |
| 64 | 0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, |
| 65 | 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, |
| 66 | 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, |
| 67 | 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, |
| 68 | 0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, |
| 69 | 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, |
| 70 | 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, |
| 71 | 0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79, |
| 72 | 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, |
| 73 | 0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, |
| 74 | 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, |
| 75 | 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, |
| 76 | 0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, |
| 77 | 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, |
| 78 | 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, |
| 79 | 0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, |
| 80 | 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf, |
| 81 | 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d}; |
Colin Cross | 28fa5bc | 2012-05-20 13:28:05 -0700 | [diff] [blame] | 82 | |
| 83 | /* |
| 84 | * A function that calculates the CRC-32 based on the table above is |
| 85 | * given below for documentation purposes. An equivalent implementation |
| 86 | * of this function that's actually used in the kernel can be found |
| 87 | * in sys/libkern.h, where it can be inlined. |
| 88 | */ |
| 89 | |
Jerry Zhang | 7b444f0 | 2018-06-12 16:42:09 -0700 | [diff] [blame] | 90 | uint32_t sparse_crc32(uint32_t crc_in, const void* buf, size_t size) { |
| 91 | const uint8_t* p = reinterpret_cast<const uint8_t*>(buf); |
| 92 | uint32_t crc; |
Colin Cross | 28fa5bc | 2012-05-20 13:28:05 -0700 | [diff] [blame] | 93 | |
Jerry Zhang | 7b444f0 | 2018-06-12 16:42:09 -0700 | [diff] [blame] | 94 | crc = crc_in ^ ~0U; |
| 95 | while (size--) crc = crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8); |
| 96 | return crc ^ ~0U; |
Colin Cross | 28fa5bc | 2012-05-20 13:28:05 -0700 | [diff] [blame] | 97 | } |