crc.go

// © 2014 the flac Authors under the MIT license. See AUTHORS for the list of authors.

package flac

import (
	"errors"
)

var crc8Table = [...]byte{0, 7, 14, 9, 28, 27, 18, 21, 56, 63, 54, 49, 36, 35, 42, 45, 112, 119, 126, 121, 108, 107, 98, 101, 72, 79, 70, 65, 84, 83, 90, 93, 224, 231, 238, 233, 252, 251, 242, 245, 216, 223, 214, 209, 196, 195, 202, 205, 144, 151, 158, 153, 140, 139, 130, 133, 168, 175, 166, 161, 180, 179, 186, 189, 199, 192, 201, 206, 219, 220, 213, 210, 255, 248, 241, 246, 227, 228, 237, 234, 183, 176, 185, 190, 171, 172, 165, 162, 143, 136, 129, 134, 147, 148, 157, 154, 39, 32, 41, 46, 59, 60, 53, 50, 31, 24, 17, 22, 3, 4, 13, 10, 87, 80, 89, 94, 75, 76, 69, 66, 111, 104, 97, 102, 115, 116, 125, 122, 137, 142, 135, 128, 149, 146, 155, 156, 177, 182, 191, 184, 173, 170, 163, 164, 249, 254, 247, 240, 229, 226, 235, 236, 193, 198, 207, 200, 221, 218, 211, 212, 105, 110, 103, 96, 117, 114, 123, 124, 81, 86, 95, 88, 77, 74, 67, 68, 25, 30, 23, 16, 5, 2, 11, 12, 33, 38, 47, 40, 61, 58, 51, 52, 78, 73, 64, 71, 82, 85, 92, 91, 118, 113, 120, 127, 106, 109, 100, 99, 62, 57, 48, 55, 34, 37, 44, 43, 6, 1, 8, 15, 26, 29, 20, 19, 174, 169, 160, 167, 178, 181, 188, 187, 150, 145, 152, 159, 138, 141, 132, 131, 222, 217, 208, 215, 194, 197, 204, 203, 230, 225, 232, 239, 250, 253, 244, 243}

func verifyCRC8(data []byte) error {
	crc := uint8(0)
	for _, d := range data {
		crc = crc8Table[crc^d]
	}
	if crc == 0 {
		return nil
	}
	return errors.New("Bad checksum")
}

var crc16Table = [...]uint16{0, 32773, 32783, 10, 32795, 30, 20, 32785, 32819, 54, 60, 32825, 40, 32813, 32807, 34, 32867, 102, 108, 32873, 120, 32893, 32887, 114, 80, 32853, 32863, 90, 32843, 78, 68, 32833, 32963, 198, 204, 32969, 216, 32989, 32983, 210, 240, 33013, 33023, 250, 33003, 238, 228, 32993, 160, 32933, 32943, 170, 32955, 190, 180, 32945, 32915, 150, 156, 32921, 136, 32909, 32903, 130, 33155, 390, 396, 33161, 408, 33181, 33175, 402, 432, 33205, 33215, 442, 33195, 430, 420, 33185, 480, 33253, 33263, 490, 33275, 510, 500, 33265, 33235, 470, 476, 33241, 456, 33229, 33223, 450, 320, 33093, 33103, 330, 33115, 350, 340, 33105, 33139, 374, 380, 33145, 360, 33133, 33127, 354, 33059, 294, 300, 33065, 312, 33085, 33079, 306, 272, 33045, 33055, 282, 33035, 270, 260, 33025, 33539, 774, 780, 33545, 792, 33565, 33559, 786, 816, 33589, 33599, 826, 33579, 814, 804, 33569, 864, 33637, 33647, 874, 33659, 894, 884, 33649, 33619, 854, 860, 33625, 840, 33613, 33607, 834, 960, 33733, 33743, 970, 33755, 990, 980, 33745, 33779, 1014, 1020, 33785, 1000, 33773, 33767, 994, 33699, 934, 940, 33705, 952, 33725, 33719, 946, 912, 33685, 33695, 922, 33675, 910, 900, 33665, 640, 33413, 33423, 650, 33435, 670, 660, 33425, 33459, 694, 700, 33465, 680, 33453, 33447, 674, 33507, 742, 748, 33513, 760, 33533, 33527, 754, 720, 33493, 33503, 730, 33483, 718, 708, 33473, 33347, 582, 588, 33353, 600, 33373, 33367, 594, 624, 33397, 33407, 634, 33387, 622, 612, 33377, 544, 33317, 33327, 554, 33339, 574, 564, 33329, 33299, 534, 540, 33305, 520, 33293, 33287, 514}

func verifyCRC16(data []byte) error {
	crc := uint16(0)
	for _, d := range data {
		crc = ((crc << 8) ^ crc16Table[(uint8(crc>>8)^d)]) & 0xFFFF
	}
	if crc == 0 {
		return nil
	}
	return errors.New("Bad checksum")
}