gkozlenko/node-video-lib

'use strict';

const CRC_TABLE = [0, 0xb71dc104, 0x6e3b8209, 0xd926430d, 0xdc760413, 0x6b6bc517, 0xb24d861a, 0x550471e, 0xb8ed0826, 0xff0c922,
    0xd6d68a2f, 0x61cb4b2b, 0x649b0c35, 0xd386cd31, 0xaa08e3c, 0xbdbd4f38, 0x70db114c, 0xc7c6d048, 0x1ee09345, 0xa9fd5241,
    0xacad155f, 0x1bb0d45b, 0xc2969756, 0x758b5652, 0xc836196a, 0x7f2bd86e, 0xa60d9b63, 0x11105a67, 0x14401d79, 0xa35ddc7d,
    0x7a7b9f70, 0xcd665e74, 0xe0b62398, 0x57abe29c, 0x8e8da191, 0x39906095, 0x3cc0278b, 0x8bdde68f, 0x52fba582, 0xe5e66486,
    0x585b2bbe, 0xef46eaba, 0x3660a9b7, 0x817d68b3, 0x842d2fad, 0x3330eea9, 0xea16ada4, 0x5d0b6ca0, 0x906d32d4, 0x2770f3d0,
    0xfe56b0dd, 0x494b71d9, 0x4c1b36c7, 0xfb06f7c3, 0x2220b4ce, 0x953d75ca, 0x28803af2, 0x9f9dfbf6, 0x46bbb8fb, 0xf1a679ff,
    0xf4f63ee1, 0x43ebffe5, 0x9acdbce8, 0x2dd07dec, 0x77708634, 0xc06d4730, 0x194b043d, 0xae56c539, 0xab068227, 0x1c1b4323,
    0xc53d002e, 0x7220c12a, 0xcf9d8e12, 0x78804f16, 0xa1a60c1b, 0x16bbcd1f, 0x13eb8a01, 0xa4f64b05, 0x7dd00808, 0xcacdc90c,
    0x7ab9778, 0xb0b6567c, 0x69901571, 0xde8dd475, 0xdbdd936b, 0x6cc0526f, 0xb5e61162, 0x2fbd066, 0xbf469f5e, 0x85b5e5a,
    0xd17d1d57, 0x6660dc53, 0x63309b4d, 0xd42d5a49, 0xd0b1944, 0xba16d840, 0x97c6a5ac, 0x20db64a8, 0xf9fd27a5, 0x4ee0e6a1,
    0x4bb0a1bf, 0xfcad60bb, 0x258b23b6, 0x9296e2b2, 0x2f2bad8a, 0x98366c8e, 0x41102f83, 0xf60dee87, 0xf35da999, 0x4440689d,
    0x9d662b90, 0x2a7bea94, 0xe71db4e0, 0x500075e4, 0x892636e9, 0x3e3bf7ed, 0x3b6bb0f3, 0x8c7671f7, 0x555032fa, 0xe24df3fe,
    0x5ff0bcc6, 0xe8ed7dc2, 0x31cb3ecf, 0x86d6ffcb, 0x8386b8d5, 0x349b79d1, 0xedbd3adc, 0x5aa0fbd8, 0xeee00c69, 0x59fdcd6d,
    0x80db8e60, 0x37c64f64, 0x3296087a, 0x858bc97e, 0x5cad8a73, 0xebb04b77, 0x560d044f, 0xe110c54b, 0x38368646, 0x8f2b4742,
    0x8a7b005c, 0x3d66c158, 0xe4408255, 0x535d4351, 0x9e3b1d25, 0x2926dc21, 0xf0009f2c, 0x471d5e28, 0x424d1936, 0xf550d832,
    0x2c769b3f, 0x9b6b5a3b, 0x26d61503, 0x91cbd407, 0x48ed970a, 0xfff0560e, 0xfaa01110, 0x4dbdd014, 0x949b9319, 0x2386521d,
    0xe562ff1, 0xb94beef5, 0x606dadf8, 0xd7706cfc, 0xd2202be2, 0x653deae6, 0xbc1ba9eb, 0xb0668ef, 0xb6bb27d7, 0x1a6e6d3,
    0xd880a5de, 0x6f9d64da, 0x6acd23c4, 0xddd0e2c0, 0x4f6a1cd, 0xb3eb60c9, 0x7e8d3ebd, 0xc990ffb9, 0x10b6bcb4, 0xa7ab7db0,
    0xa2fb3aae, 0x15e6fbaa, 0xccc0b8a7, 0x7bdd79a3, 0xc660369b, 0x717df79f, 0xa85bb492, 0x1f467596, 0x1a163288, 0xad0bf38c,
    0x742db081, 0xc3307185, 0x99908a5d, 0x2e8d4b59, 0xf7ab0854, 0x40b6c950, 0x45e68e4e, 0xf2fb4f4a, 0x2bdd0c47, 0x9cc0cd43,
    0x217d827b, 0x9660437f, 0x4f460072, 0xf85bc176, 0xfd0b8668, 0x4a16476c, 0x93300461, 0x242dc565, 0xe94b9b11, 0x5e565a15,
    0x87701918, 0x306dd81c, 0x353d9f02, 0x82205e06, 0x5b061d0b, 0xec1bdc0f, 0x51a69337, 0xe6bb5233, 0x3f9d113e, 0x8880d03a,
    0x8dd09724, 0x3acd5620, 0xe3eb152d, 0x54f6d429, 0x7926a9c5, 0xce3b68c1, 0x171d2bcc, 0xa000eac8, 0xa550add6, 0x124d6cd2,
    0xcb6b2fdf, 0x7c76eedb, 0xc1cba1e3, 0x76d660e7, 0xaff023ea, 0x18ede2ee, 0x1dbda5f0, 0xaaa064f4, 0x738627f9, 0xc49be6fd,
    0x9fdb889, 0xbee0798d, 0x67c63a80, 0xd0dbfb84, 0xd58bbc9a, 0x62967d9e, 0xbbb03e93, 0xcadff97, 0xb110b0af, 0x60d71ab,
    0xdf2b32a6, 0x6836f3a2, 0x6d66b4bc, 0xda7b75b8, 0x35d36b5, 0xb440f7b1, 1];

function reverseBytes(value) {
    return ((value >>> 24)) | ((value >> 8) & 0xFF00) | ((value << 8) & 0xFF0000) | ((value << 24));
}

function getChecksum(buf, start, end) {
    start = start || 0;
    end = end || buf.length;
    let checksumVal = -1, res;
    for (let i = start; i < end; i++) {
        res = (checksumVal ^ buf[i]) & 0xff;
        checksumVal = CRC_TABLE[res] ^ checksumVal >> 8 & 0xffffff;
    }
    return reverseBytes(checksumVal);
}

module.exports = {
    checksum: getChecksum,
};