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42 lines
790 B
JavaScript
42 lines
790 B
JavaScript
7 years ago
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'use strict';
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// Note: we can't get significant speed boost here.
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// So write code to minimize size - no pregenerated tables
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// and array tools dependencies.
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// Use ordinary array, since untyped makes no boost here
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function makeTable() {
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var c, table = [];
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for (var n = 0; n < 256; n++) {
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c = n;
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for (var k = 0; k < 8; k++) {
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c = ((c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1));
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}
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table[n] = c;
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}
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return table;
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}
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// Create table on load. Just 255 signed longs. Not a problem.
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var crcTable = makeTable();
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function crc32(crc, buf, len, pos) {
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var t = crcTable,
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end = pos + len;
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crc ^= -1;
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for (var i = pos; i < end; i++) {
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crc = (crc >>> 8) ^ t[(crc ^ buf[i]) & 0xFF];
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}
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return (crc ^ (-1)); // >>> 0;
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}
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module.exports = crc32;
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