51 lines
1.4 KiB
JavaScript
51 lines
1.4 KiB
JavaScript
/**
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* SeededRandom.js
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* A deterministic pseudo-random number generator using Mulberry32.
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* Essential for reproducible procedural generation.
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*/
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export class SeededRandom {
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constructor(seed) {
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// Hash the string seed to a number if necessary
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if (typeof seed === "string") {
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this.state = this.hashString(seed);
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} else {
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this.state = seed || Math.floor(Math.random() * 2147483647);
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}
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}
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hashString(str) {
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let hash = 1779033703 ^ str.length;
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for (let i = 0; i < str.length; i++) {
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hash = Math.imul(hash ^ str.charCodeAt(i), 3432918353);
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hash = (hash << 13) | (hash >>> 19);
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}
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// Perform the final mixing immediately and return the result
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hash = Math.imul(hash ^ (hash >>> 16), 2246822507);
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hash = Math.imul(hash ^ (hash >>> 13), 3266489909);
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return hash >>> 0;
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}
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// Mulberry32 Algorithm
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next() {
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let t = (this.state += 0x6d2b79f5);
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t = Math.imul(t ^ (t >>> 15), t | 1);
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t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
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return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
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}
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// Returns float between [min, max)
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range(min, max) {
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return min + this.next() * (max - min);
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}
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// Returns integer between [min, max] (inclusive)
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rangeInt(min, max) {
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return Math.floor(this.range(min, max + 1));
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}
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// Returns true/false based on probability (0.0 - 1.0)
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chance(probability) {
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return this.next() < probability;
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}
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}
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