46 lines
1 KiB
JavaScript
46 lines
1 KiB
JavaScript
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/*
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MIT License http://www.opensource.org/licenses/mit-license.php
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Author Tobias Koppers @sokra
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*/
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"use strict";
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const SAFE_LIMIT = 0x80000000;
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const SAFE_PART = SAFE_LIMIT - 1;
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const COUNT = 4;
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const arr = [0, 0, 0, 0, 0];
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const primes = [3, 7, 17, 19];
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module.exports = (str, range) => {
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arr.fill(0);
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for (let i = 0; i < str.length; i++) {
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const c = str.charCodeAt(i);
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for (let j = 0; j < COUNT; j++) {
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const p = (j + COUNT - 1) % COUNT;
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arr[j] = (arr[j] + c * primes[j] + arr[p]) & SAFE_PART;
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}
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for (let j = 0; j < COUNT; j++) {
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const q = arr[j] % COUNT;
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arr[j] = arr[j] ^ (arr[q] >> 1);
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}
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}
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if (range <= SAFE_PART) {
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let sum = 0;
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for (let j = 0; j < COUNT; j++) {
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sum = (sum + arr[j]) % range;
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}
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return sum;
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} else {
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let sum1 = 0;
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let sum2 = 0;
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const rangeExt = Math.floor(range / SAFE_LIMIT);
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for (let j = 0; j < COUNT; j += 2) {
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sum1 = (sum1 + arr[j]) & SAFE_PART;
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}
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for (let j = 1; j < COUNT; j += 2) {
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sum2 = (sum2 + arr[j]) % rangeExt;
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}
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return (sum2 * SAFE_LIMIT + sum1) % range;
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}
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};
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