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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,154 @@ | ||
| /* | ||
| https://en.wikipedia.org/wiki/Cyclic_redundancy_check | ||
| Algorithms ported from https://pycrc.org/ | ||
| */ | ||
|
|
||
| class CRC { | ||
| constructor(width, poly, xor_in, xor_out, reflect) { | ||
| this.width = width | ||
| this.poly = poly | ||
| this.xor_in = xor_in | ||
| this.xor_out = xor_out | ||
| this.reflect = reflect | ||
| this.msb_mask = 1 << (this.width - 1) | ||
| this.mask = ((this.msb_mask - 1) << 1) | 1 | ||
| this.crc_shift = this.width < 8 ? 8 - this.width : 0 | ||
| let table = this.gen_table() | ||
| this.table = table | ||
|
|
||
| // optimized for crc32c | ||
| if (width === 32 && reflect && xor_in === 0xffffffff && xor_out === 0xffffffff) { | ||
| this.calculate = function (buffer) { | ||
| buffer = preprocess(buffer) | ||
| let crc = -1 | ||
| for (let i = 0; i < buffer.length; i++) | ||
| crc = table[(crc ^ buffer[i]) & 0xff] ^ (crc >>> 8) | ||
| return (crc ^ -1) >>> 0 | ||
| } | ||
| } | ||
| } | ||
|
|
||
| calculate(buffer) { | ||
| buffer = preprocess(buffer) | ||
| let crc | ||
| if (this.reflect) { | ||
| crc = this.xor_in === 0xffffffff ? -1 : reflect(this.xor_in, this.width) | ||
| for (let i = 0; i < buffer.length; i++) { | ||
| let key = (crc ^ buffer[i]) & 0xff | ||
| crc = (this.table[key] ^ (crc >>> 8)) & this.mask | ||
| } | ||
| } else { | ||
| crc = this.xor_in << this.crc_shift | ||
| for (let i = 0; i < buffer.length; i++) { | ||
| let key = ((crc >> (this.width - 8 + this.crc_shift)) ^ buffer[i]) & 0xff | ||
| crc <<= 8 - this.crc_shift | ||
| crc ^= this.table[key] << this.crc_shift | ||
| crc &= this.mask << this.crc_shift | ||
| } | ||
| crc >>= this.crc_shift | ||
| } | ||
| crc ^= this.xor_out | ||
| return crc >>> 0 | ||
| } | ||
|
|
||
| calculate_no_table(buffer) { | ||
| buffer = preprocess(buffer) | ||
| let crc = this.xor_in | ||
| for (let i = 0; i < buffer.length; i++) { | ||
| let octet = buffer[i] | ||
| if (this.reflect) octet = reflect(octet, 8) | ||
| for (let i = 0; i < 8; i++) { | ||
| let topbit = crc & this.msb_mask | ||
| if (octet & (0x80 >> i)) topbit ^= this.msb_mask | ||
| crc <<= 1 | ||
| if (topbit) crc ^= this.poly | ||
| } | ||
| crc &= this.mask | ||
| } | ||
| if (this.reflect) crc = reflect(crc, this.width) | ||
| crc ^= this.xor_out | ||
| return crc >>> 0 | ||
| } | ||
|
|
||
| gen_table() { | ||
| let table_length = 256 | ||
| let table = [] | ||
| for (let i = 0; i < table_length; i++) { | ||
| let reg = i | ||
| if (this.reflect) reg = reflect(reg, 8) | ||
| reg = reg << (this.width - 8 + this.crc_shift) | ||
| for (let j = 0; j < 8; j++) { | ||
| if ((reg & (this.msb_mask << this.crc_shift)) !== 0) { | ||
| reg <<= 1 | ||
| reg ^= this.poly << this.crc_shift | ||
| } else { | ||
| reg <<= 1 | ||
| } | ||
| } | ||
| if (this.reflect) reg = reflect(reg >> this.crc_shift, this.width) << this.crc_shift | ||
| reg = (reg >> this.crc_shift) & this.mask | ||
| table[i] = reg >>> 0 | ||
| } | ||
| return table | ||
| } | ||
|
|
||
| print() { | ||
| let table = this.table | ||
| let digits = Math.ceil(this.width / 4) | ||
| let shift = (digits < 4) ? 4 : 3 | ||
| let rows = table.length >> shift | ||
| let columns = 1 << shift | ||
| let result = '' | ||
| for (let r = 0; r < rows; r++) { | ||
| let row = '' | ||
| for (let c = 0; c < columns; c++) { | ||
| let val = table[r << shift | c] | ||
| val = '000000000' + val.toString(16) | ||
| val = val.substr(val.length - digits) | ||
| row += '0x' + val + ', ' | ||
| } | ||
| result += ' ' + row + '\n' | ||
| } | ||
| result = '[\n' + result.slice(0, -3) + '\n]' | ||
| return result | ||
| } | ||
|
|
||
| } | ||
|
|
||
|
|
||
| function preprocess(data) { | ||
| if (Buffer.isBuffer(data)) return data | ||
| switch (typeof data) { | ||
| case 'number': | ||
| let buffer = Buffer.alloc(4) | ||
| buffer.writeUInt32BE(data) | ||
| return buffer | ||
| case 'string': | ||
| return Buffer.from(data) | ||
| default: | ||
| throw new Error() | ||
| } | ||
| } | ||
|
|
||
|
|
||
| function reflect(data, width) { | ||
| let res = 0 | ||
| for (let i = 0; i < width; i++) { | ||
| res = res << 1 | data & 1 | ||
| data >>= 1 | ||
| } | ||
| return res | ||
| } | ||
|
|
||
|
|
||
| module.exports = { | ||
| CRC, | ||
| crc6: new CRC(6, 0x2F), | ||
| crc8: new CRC(8, 0x07), | ||
| crc10: new CRC(10, 0x233), | ||
| crc32: new CRC(32, 0x04C11DB7, 0xFFFFFFFF, 0xFFFFFFFF, true), | ||
| crc32c: new CRC(32, 0x1EDC6F41, 0xFFFFFFFF, 0xFFFFFFFF, true) | ||
| } |
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