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30 lines
821 B
30 lines
821 B
2 years ago
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var isStr = require('./isStr');
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var strToBytes = require('./strToBytes');
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var TABLE = [];
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for (var n = 0; n < 256; n++) {
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var c = n;
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for (var k = 0; k < 8; k++) {
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if (c & 1) {
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c = 0xedb88320 ^ (c >>> 1);
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} else {
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c = c >>> 1;
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}
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}
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TABLE[n] = c >>> 0;
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}
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if (typeof Int32Array !== 'undefined') TABLE = new Int32Array(TABLE);
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exports = function(input, previous) {
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return exports.signed(input, previous) >>> 0;
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};
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exports.signed = function(input, previous) {
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if (isStr(input)) input = strToBytes(input);
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var crc = previous === 0 ? 0 : ~~previous ^ -1;
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for (var i = 0, len = input.length; i < len; i++) {
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var byte = input[i];
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crc = TABLE[(crc ^ byte) & 0xff] ^ (crc >>> 8);
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}
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return crc ^ -1;
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};
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module.exports = exports;
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