Hashing and strict value equality for JavaScript primitives

eq.js

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
const xxh_1 = require("./xxh");
// Hash randomization
const SEED_ARRAY = (1000000000 * Math.random()) | 0;
const SEED_BIG = (1000000000 * Math.random()) | 0;
const SEED_NUM = (1000000000 * Math.random()) | 0;
const SEED_STR = (1000000000 * Math.random()) | 0;
const SEED_KEY = (1000000000 * Math.random()) | 0;
const SEED_DATE = (1000000000 * Math.random()) | 0;
const SEED_BOOL = (1000000000 * Math.random()) | 0;
const SEED_NULL = (1000000000 * Math.random()) | 0;
const XXH_FALSE = xxh_1.xxh_final(xxh_1.xxh_update(xxh_1.xxh_init(SEED_BOOL), 0));
const XXH_TRUE = xxh_1.xxh_final(xxh_1.xxh_update(xxh_1.xxh_init(SEED_BOOL), 1));
const XXH_NULL = xxh_1.xxh_final(xxh_1.xxh_update(xxh_1.xxh_init(SEED_NULL), 0));
const XXH_PRIV_SYM_NO_DESC = xxh_1.xxh_final(xxh_1.xxh_update(xxh_1.xxh_init(SEED_KEY), 0));
// union
const u = new ArrayBuffer(8);
const i32 = new Int32Array(u);
const i64 = new BigInt64Array(u);
const f64 = new Float64Array(u);
/**
 * Compute the hash code of a JavaScript primitive value. Note that objects are not values. Arrays are permitted in the case they are used as tuples.
 *
 * Improper use will throw `TypeError`.
 *
 * @param v any JavaScript primitive `bigint`, `boolean`, `number`, `Date`, `Array`, `null`, `string` or `symbol`
 */
function hashCode(v) {
    switch (typeof v) {
        case "bigint": {
            i64[0] = v; // truncate
            let h = xxh_1.xxh_init(SEED_BIG);
            h = xxh_1.xxh_update(h, i32[0]);
            h = xxh_1.xxh_update(h, i32[1]);
            return xxh_1.xxh_final(h);
        }
        case "boolean":
            return v ? XXH_TRUE : XXH_FALSE;
        case "number": {
            f64[0] = v;
            let h = xxh_1.xxh_init(SEED_NUM);
            h = xxh_1.xxh_update(h, i32[0]);
            h = xxh_1.xxh_update(h, i32[1]);
            return xxh_1.xxh_final(h);
        }
        case "object": {
            if (v instanceof Date) {
                return xxh_1.xxh_final(xxh_1.xxh_update(xxh_1.xxh_init(SEED_DATE), +v));
            }
            if (Array.isArray(v)) {
                let h = xxh_1.xxh_init((SEED_ARRAY + (v.length << 2)) | 0);
                for (let i = 0; i < v.length; i++) {
                    h = xxh_1.xxh_update(h, hashCode(v[i]));
                }
                return xxh_1.xxh_final(h);
            }
            if (v === null) {
                return XXH_NULL;
            }
            // the main reason for this is testing hash collisions,
            // it's not recommended that you write your own `hashCode()` function
            if (_hashCodeFunction(v)) {
                return v.hashCode();
            }
            throw new TypeError(`[object ${v.constructor.name}] is not a supported primitive`);
        }
        case "string": {
            return xxh_1.xxh_str(v, SEED_STR);
        }
        case "symbol": {
            const description = v.description;
            if (description !== undefined) {
                return xxh_1.xxh_str(description, SEED_KEY);
            }
            return XXH_PRIV_SYM_NO_DESC;
        }
    }
    throw new TypeError(`value with type ${typeof v} is not a supported primitive`);
}
exports.hashCode = hashCode;
/** test whether object has custom  `hashCode()` function */
function _hashCodeFunction(obj) {
    return typeof obj.hashCode === "function";
}
function equals(a, b) {
    switch (typeof a) {
        case "object": {
            if (a instanceof Date) {
                if (b instanceof Date) {
                    return +a === +b;
                }
                return false;
            }
            if (Array.isArray(a)) {
                if (Array.isArray(b)) {
                    if (a.length === b.length) {
                        for (let i = 0; i < a.length; i++) {
                            if (!equals(a[i], b[i])) {
                                return false;
                            }
                        }
                        return true;
                    }
                }
                return false;
            }
            break;
        }
    }
    return a === b;
}
exports.equals = equals;
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