| Himani Chawla | 4ff5fab | 2021-11-09 19:19:29 +0530 | [diff] [blame] | 1 | package crc32a |
| 2 | |
| 3 | import ( |
| 4 | "encoding/binary" |
| 5 | "encoding/hex" |
| 6 | ) |
| 7 | |
| 8 | // Checksum calculates CRC32A (ITU I.363.5 algorithm, popularized by BZIP2) checksum. |
| 9 | // This function will produce the same results as following PHP code: |
| 10 | // hexdec(hash('crc32', $data)) |
| 11 | func Checksum(data []byte) uint32 { |
| 12 | b := digest(data) |
| 13 | |
| 14 | return binary.BigEndian.Uint32(b) |
| 15 | } |
| 16 | |
| 17 | // ChecksumHex is a convenience function that outputs CRC32A (ITU I.363.5 algorithm, popularized by BZIP2) checksum as a hex string. |
| 18 | // This function will produce the same results as following PHP code: |
| 19 | // hash('crc32', $data) |
| 20 | func ChecksumHex(data []byte) string { |
| 21 | b := digest(data) |
| 22 | |
| 23 | return hex.EncodeToString(b) |
| 24 | } |
| 25 | |
| 26 | // digest performs checksum calculation for each byte of provided data and returns digest in form of byte array. |
| 27 | func digest(data []byte) []byte { |
| 28 | var crc uint32 |
| 29 | var digest = make([]byte, 4) |
| 30 | |
| 31 | crc = ^crc |
| 32 | for i := 0; i < len(data); i++ { |
| 33 | crc = (crc << 8) ^ table[(crc >> 24) ^ (uint32(data[i]) & 0xff)] |
| 34 | } |
| 35 | crc = ^crc |
| 36 | |
| 37 | digest[3] = byte((crc >> 24) & 0xff) |
| 38 | digest[2] = byte((crc >> 16) & 0xff) |
| 39 | digest[1] = byte((crc >> 8) & 0xff) |
| 40 | digest[0] = byte(crc & 0xff) |
| 41 | |
| 42 | return digest |
| 43 | } |
| 44 | |
| 45 | // table is the pre-generated 0x04C11DB7 polynominal used for CRC32A. |
| 46 | var table = [256]uint32{ |
| 47 | 0x0, |
| 48 | 0x04c11db7, 0x09823b6e, 0x0d4326d9, 0x130476dc, 0x17c56b6b, |
| 49 | 0x1a864db2, 0x1e475005, 0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, |
| 50 | 0x2b4bcb61, 0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd, |
| 51 | 0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9, 0x5f15adac, |
| 52 | 0x5bd4b01b, 0x569796c2, 0x52568b75, 0x6a1936c8, 0x6ed82b7f, |
| 53 | 0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3, 0x709f7b7a, |
| 54 | 0x745e66cd, 0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039, |
| 55 | 0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 0xbe2b5b58, |
| 56 | 0xbaea46ef, 0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033, |
| 57 | 0xa4ad16ea, 0xa06c0b5d, 0xd4326d90, 0xd0f37027, 0xddb056fe, |
| 58 | 0xd9714b49, 0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95, |
| 59 | 0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1, 0xe13ef6f4, |
| 60 | 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 0x34867077, 0x30476dc0, |
| 61 | 0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5, |
| 62 | 0x2ac12072, 0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16, |
| 63 | 0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca, 0x7897ab07, |
| 64 | 0x7c56b6b0, 0x71159069, 0x75d48dde, 0x6b93dddb, 0x6f52c06c, |
| 65 | 0x6211e6b5, 0x66d0fb02, 0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, |
| 66 | 0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba, |
| 67 | 0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b, |
| 68 | 0xbb60adfc, 0xb6238b25, 0xb2e29692, 0x8aad2b2f, 0x8e6c3698, |
| 69 | 0x832f1041, 0x87ee0df6, 0x99a95df3, 0x9d684044, 0x902b669d, |
| 70 | 0x94ea7b2a, 0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e, |
| 71 | 0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2, 0xc6bcf05f, |
| 72 | 0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34, |
| 73 | 0xdc3abded, 0xd8fba05a, 0x690ce0ee, 0x6dcdfd59, 0x608edb80, |
| 74 | 0x644fc637, 0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb, |
| 75 | 0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f, 0x5c007b8a, |
| 76 | 0x58c1663d, 0x558240e4, 0x51435d53, 0x251d3b9e, 0x21dc2629, |
| 77 | 0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5, 0x3f9b762c, |
| 78 | 0x3b5a6b9b, 0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff, |
| 79 | 0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 0xf12f560e, |
| 80 | 0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65, |
| 81 | 0xeba91bbc, 0xef68060b, 0xd727bbb6, 0xd3e6a601, 0xdea580d8, |
| 82 | 0xda649d6f, 0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3, |
| 83 | 0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7, 0xae3afba2, |
| 84 | 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 0x9b3660c6, 0x9ff77d71, |
| 85 | 0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74, |
| 86 | 0x857130c3, 0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640, |
| 87 | 0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c, 0x7b827d21, |
| 88 | 0x7f436096, 0x7200464f, 0x76c15bf8, 0x68860bfd, 0x6c47164a, |
| 89 | 0x61043093, 0x65c52d24, 0x119b4be9, 0x155a565e, 0x18197087, |
| 90 | 0x1cd86d30, 0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec, |
| 91 | 0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d, |
| 92 | 0x2056cd3a, 0x2d15ebe3, 0x29d4f654, 0xc5a92679, 0xc1683bce, |
| 93 | 0xcc2b1d17, 0xc8ea00a0, 0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, |
| 94 | 0xdbee767c, 0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18, |
| 95 | 0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4, 0x89b8fd09, |
| 96 | 0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662, |
| 97 | 0x933eb0bb, 0x97ffad0c, 0xafb010b1, 0xab710d06, 0xa6322bdf, |
| 98 | 0xa2f33668, 0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4, |
| 99 | } |