node-csfd-api/anubis/proof-of-work.js

ČSFD API in JavaScript. Amazing NPM library for scrapping csfd.cz :)

import { sha256, toHex } from "./sha256.js";
//#region src/anubis/proof-of-work.ts
const DEFAULT_TIME_BUDGET_MS = 1e4;
const YIELD_INTERVAL = 4096;
const scheduleImmediate = globalThis.setImmediate;
const yieldToEventLoop = scheduleImmediate ? () => new Promise((resolve) => scheduleImmediate(() => resolve())) : () => new Promise((resolve) => setTimeout(() => resolve(), 0));
/**
* Find a nonce whose `sha256(data + nonce)` digest starts with `difficulty`
* zero nibbles, mirroring Anubis' own worker: whole zero bytes first, then the
* high nibble of the next byte when difficulty is odd.
*
* Resolves `null` if no nonce is found within the time budget.
*/
const solveProofOfWork = async (data, difficulty, timeBudgetMs = DEFAULT_TIME_BUDGET_MS) => {
	const requiredZeroBytes = Math.floor(difficulty / 2);
	const isDifficultyOdd = difficulty % 2 !== 0;
	const deadline = Date.now() + timeBudgetMs;
	for (let nonce = 0;; nonce++) {
		if (nonce > 0 && nonce % YIELD_INTERVAL === 0) {
			if (Date.now() > deadline) return null;
			await yieldToEventLoop();
		}
		const digest = sha256(data + nonce);
		let valid = true;
		for (let i = 0; i < requiredZeroBytes; i++) if (digest[i] !== 0) {
			valid = false;
			break;
		}
		if (valid && isDifficultyOdd && digest[requiredZeroBytes] >> 4 !== 0) valid = false;
		if (valid) return {
			hash: toHex(digest),
			nonce
		};
	}
};
//#endregion
export { DEFAULT_TIME_BUDGET_MS, solveProofOfWork };

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