antlr4ts/misc/MurmurHash.js

ANTLR 4 runtime for JavaScript written in Typescript

"use strict";
/*!
 * Copyright 2016 The ANTLR Project. All rights reserved.
 * Licensed under the BSD-3-Clause license. See LICENSE file in the project root for license information.
 */
Object.defineProperty(exports, "__esModule", { value: true });
exports.MurmurHash = void 0;
/**
 *
 * @author Sam Harwell
 */
var MurmurHash;
(function (MurmurHash) {
    const DEFAULT_SEED = 0;
    /**
     * Initialize the hash using the specified `seed`.
     *
     * @param seed the seed (optional)
     * @returns the intermediate hash value
     */
    function initialize(seed = DEFAULT_SEED) {
        return seed;
    }
    MurmurHash.initialize = initialize;
    /**
     * Update the intermediate hash value for the next input `value`.
     *
     * @param hash the intermediate hash value
     * @param value the value to add to the current hash
     * @returns the updated intermediate hash value
     */
    function update(hash, value) {
        const c1 = 0xCC9E2D51;
        const c2 = 0x1B873593;
        const r1 = 15;
        const r2 = 13;
        const m = 5;
        const n = 0xE6546B64;
        if (value == null) {
            value = 0;
        }
        else if (typeof value === "string") {
            value = hashString(value);
        }
        else if (typeof value === "object") {
            value = value.hashCode();
        }
        let k = value;
        k = Math.imul(k, c1);
        k = (k << r1) | (k >>> (32 - r1));
        k = Math.imul(k, c2);
        hash = hash ^ k;
        hash = (hash << r2) | (hash >>> (32 - r2));
        hash = Math.imul(hash, m) + n;
        return hash & 0xFFFFFFFF;
    }
    MurmurHash.update = update;
    /**
     * Apply the final computation steps to the intermediate value `hash`
     * to form the final result of the MurmurHash 3 hash function.
     *
     * @param hash the intermediate hash value
     * @param numberOfWords the number of integer values added to the hash
     * @returns the final hash result
     */
    function finish(hash, numberOfWords) {
        hash = hash ^ (numberOfWords * 4);
        hash = hash ^ (hash >>> 16);
        hash = Math.imul(hash, 0x85EBCA6B);
        hash = hash ^ (hash >>> 13);
        hash = Math.imul(hash, 0xC2B2AE35);
        hash = hash ^ (hash >>> 16);
        return hash;
    }
    MurmurHash.finish = finish;
    /**
     * Utility function to compute the hash code of an array using the
     * MurmurHash algorithm.
     *
     * @param <T> the array element type
     * @param data the array data
     * @param seed the seed for the MurmurHash algorithm
     * @returns the hash code of the data
     */
    function hashCode(data, seed = DEFAULT_SEED) {
        let hash = initialize(seed);
        let length = 0;
        for (let value of data) {
            hash = update(hash, value);
            length++;
        }
        hash = finish(hash, length);
        return hash;
    }
    MurmurHash.hashCode = hashCode;
    /**
     * Function to hash a string. Based on the implementation found here:
     * http://stackoverflow.com/a/7616484
     */
    function hashString(str) {
        let len = str.length;
        if (len === 0) {
            return 0;
        }
        let hash = 0;
        for (let i = 0; i < len; i++) {
            let c = str.charCodeAt(i);
            hash = (((hash << 5) >>> 0) - hash) + c;
            hash |= 0;
        }
        return hash;
    }
})(MurmurHash = exports.MurmurHash || (exports.MurmurHash = {}));
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