From c6ed05d2c34828fe8d3249e74c6afc4ba5c8eed0 Mon Sep 17 00:00:00 2001 From: Daniel Huigens Date: Sat, 8 Feb 2020 03:07:56 +0100 Subject: [PATCH] Optimize crc24 calculation --- src/encoding/armor.js | 84 ++++++++++++++++++++++++------------------- 1 file changed, 48 insertions(+), 36 deletions(-) diff --git a/src/encoding/armor.js b/src/encoding/armor.js index 2385e302..259a7274 100644 --- a/src/encoding/armor.js +++ b/src/encoding/armor.js @@ -126,53 +126,65 @@ function getCheckSum(data) { return base64.encode(crc); } +// https://create.stephan-brumme.com/crc32/#slicing-by-8-overview + const crc_table = [ - 0x00000000, 0x00864cfb, 0x018ad50d, 0x010c99f6, 0x0393e6e1, 0x0315aa1a, 0x021933ec, 0x029f7f17, 0x07a18139, - 0x0727cdc2, 0x062b5434, 0x06ad18cf, 0x043267d8, 0x04b42b23, 0x05b8b2d5, 0x053efe2e, 0x0fc54e89, 0x0f430272, - 0x0e4f9b84, 0x0ec9d77f, 0x0c56a868, 0x0cd0e493, 0x0ddc7d65, 0x0d5a319e, 0x0864cfb0, 0x08e2834b, 0x09ee1abd, - 0x09685646, 0x0bf72951, 0x0b7165aa, 0x0a7dfc5c, 0x0afbb0a7, 0x1f0cd1e9, 0x1f8a9d12, 0x1e8604e4, 0x1e00481f, - 0x1c9f3708, 0x1c197bf3, 0x1d15e205, 0x1d93aefe, 0x18ad50d0, 0x182b1c2b, 0x192785dd, 0x19a1c926, 0x1b3eb631, - 0x1bb8faca, 0x1ab4633c, 0x1a322fc7, 0x10c99f60, 0x104fd39b, 0x11434a6d, 0x11c50696, 0x135a7981, 0x13dc357a, - 0x12d0ac8c, 0x1256e077, 0x17681e59, 0x17ee52a2, 0x16e2cb54, 0x166487af, 0x14fbf8b8, 0x147db443, 0x15712db5, - 0x15f7614e, 0x3e19a3d2, 0x3e9fef29, 0x3f9376df, 0x3f153a24, 0x3d8a4533, 0x3d0c09c8, 0x3c00903e, 0x3c86dcc5, - 0x39b822eb, 0x393e6e10, 0x3832f7e6, 0x38b4bb1d, 0x3a2bc40a, 0x3aad88f1, 0x3ba11107, 0x3b275dfc, 0x31dced5b, - 0x315aa1a0, - 0x30563856, 0x30d074ad, 0x324f0bba, 0x32c94741, 0x33c5deb7, 0x3343924c, 0x367d6c62, 0x36fb2099, 0x37f7b96f, - 0x3771f594, 0x35ee8a83, 0x3568c678, 0x34645f8e, 0x34e21375, 0x2115723b, 0x21933ec0, 0x209fa736, 0x2019ebcd, - 0x228694da, 0x2200d821, 0x230c41d7, 0x238a0d2c, 0x26b4f302, 0x2632bff9, 0x273e260f, 0x27b86af4, 0x252715e3, - 0x25a15918, 0x24adc0ee, 0x242b8c15, 0x2ed03cb2, 0x2e567049, 0x2f5ae9bf, 0x2fdca544, 0x2d43da53, 0x2dc596a8, - 0x2cc90f5e, 0x2c4f43a5, 0x2971bd8b, 0x29f7f170, 0x28fb6886, 0x287d247d, 0x2ae25b6a, 0x2a641791, 0x2b688e67, - 0x2beec29c, 0x7c3347a4, 0x7cb50b5f, 0x7db992a9, 0x7d3fde52, 0x7fa0a145, 0x7f26edbe, 0x7e2a7448, 0x7eac38b3, - 0x7b92c69d, 0x7b148a66, 0x7a181390, 0x7a9e5f6b, 0x7801207c, 0x78876c87, 0x798bf571, 0x790db98a, 0x73f6092d, - 0x737045d6, 0x727cdc20, 0x72fa90db, 0x7065efcc, 0x70e3a337, 0x71ef3ac1, 0x7169763a, 0x74578814, 0x74d1c4ef, - 0x75dd5d19, 0x755b11e2, 0x77c46ef5, 0x7742220e, 0x764ebbf8, 0x76c8f703, 0x633f964d, 0x63b9dab6, 0x62b54340, - 0x62330fbb, - 0x60ac70ac, 0x602a3c57, 0x6126a5a1, 0x61a0e95a, 0x649e1774, 0x64185b8f, 0x6514c279, 0x65928e82, 0x670df195, - 0x678bbd6e, 0x66872498, 0x66016863, 0x6cfad8c4, 0x6c7c943f, 0x6d700dc9, 0x6df64132, 0x6f693e25, 0x6fef72de, - 0x6ee3eb28, 0x6e65a7d3, 0x6b5b59fd, 0x6bdd1506, 0x6ad18cf0, 0x6a57c00b, 0x68c8bf1c, 0x684ef3e7, 0x69426a11, - 0x69c426ea, 0x422ae476, 0x42aca88d, 0x43a0317b, 0x43267d80, 0x41b90297, 0x413f4e6c, 0x4033d79a, 0x40b59b61, - 0x458b654f, 0x450d29b4, 0x4401b042, 0x4487fcb9, 0x461883ae, 0x469ecf55, 0x479256a3, 0x47141a58, 0x4defaaff, - 0x4d69e604, 0x4c657ff2, 0x4ce33309, 0x4e7c4c1e, 0x4efa00e5, 0x4ff69913, 0x4f70d5e8, 0x4a4e2bc6, 0x4ac8673d, - 0x4bc4fecb, 0x4b42b230, 0x49ddcd27, 0x495b81dc, 0x4857182a, 0x48d154d1, 0x5d26359f, 0x5da07964, 0x5cace092, - 0x5c2aac69, 0x5eb5d37e, 0x5e339f85, 0x5f3f0673, 0x5fb94a88, 0x5a87b4a6, 0x5a01f85d, 0x5b0d61ab, 0x5b8b2d50, - 0x59145247, 0x59921ebc, 0x589e874a, 0x5818cbb1, 0x52e37b16, 0x526537ed, 0x5369ae1b, 0x53efe2e0, 0x51709df7, - 0x51f6d10c, - 0x50fa48fa, 0x507c0401, 0x5542fa2f, 0x55c4b6d4, 0x54c82f22, 0x544e63d9, 0x56d11cce, 0x56575035, 0x575bc9c3, - 0x57dd8538 + new Array(0xFF), + new Array(0xFF), + new Array(0xFF), + new Array(0xFF) ]; +for (let i = 0; i <= 0xFF; i++) { + let crc = i << 16; + for (let j = 0; j < 8; j++) { + crc = (crc << 1) ^ ((crc & 0x800000) !== 0 ? 0x864CFB : 0); + } + crc_table[0][i] = + ((crc & 0xFF0000) >> 16) | + (crc & 0x00FF00) | + ((crc & 0x0000FF) << 16); +} +for (let i = 0; i <= 0xFF; i++) { + crc_table[1][i] = (crc_table[0][i] >> 8) ^ crc_table[0][crc_table[0][i] & 0xFF]; +} +for (let i = 0; i <= 0xFF; i++) { + crc_table[2][i] = (crc_table[1][i] >> 8) ^ crc_table[0][crc_table[1][i] & 0xFF]; +} +for (let i = 0; i <= 0xFF; i++) { + crc_table[3][i] = (crc_table[2][i] >> 8) ^ crc_table[0][crc_table[2][i] & 0xFF]; +} + +// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView#Endianness +const isLittleEndian = (function() { + const buffer = new ArrayBuffer(2); + new DataView(buffer).setInt16(0, 0xFF, true /* littleEndian */); + // Int16Array uses the platform's endianness. + return new Int16Array(buffer)[0] === 0xFF; +}()); + /** * Internal function to calculate a CRC-24 checksum over a given string (data) * @param {String | ReadableStream} data Data to create a CRC-24 checksum for * @returns {Uint8Array | ReadableStream} The CRC-24 checksum */ function createcrc24(input) { - let crc = 0xB704CE; + let crc = 0xCE04B7; return stream.transform(input, value => { - for (let index = 0; index < value.length; index++) { - crc = (crc << 8) ^ crc_table[((crc >> 16) ^ value[index]) & 0xff]; + const len32 = isLittleEndian ? Math.floor(value.length / 4) : 0; + const arr32 = new Uint32Array(value.buffer, value.byteOffset, len32); + for (let i = 0; i < len32; i++) { + crc ^= arr32[i]; + crc = + crc_table[0][(crc >> 24) & 0xFF] ^ + crc_table[1][(crc >> 16) & 0xFF] ^ + crc_table[2][(crc >> 8) & 0xFF] ^ + crc_table[3][(crc >> 0) & 0xFF]; } - }, () => new Uint8Array([crc >> 16, crc >> 8, crc])); + for (let i = len32 * 4; i < value.length; i++) { + crc = (crc >> 8) ^ crc_table[0][(crc & 0xFF) ^ value[i]]; + } + }, () => new Uint8Array([crc, crc >> 8, crc >> 16])); } /**