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// https://dev.to/ratmd/simple-proof-of-work-in-javascript-3kgm
export function process(data, difficulty = 5, threads = (navigator.hardwareConcurrency || 1)) {
return new Promise((resolve, reject) => {
let webWorkerURL = URL.createObjectURL(new Blob([
'(', processTask(), ')()'
], { type: 'application/javascript' }));
const workers = [];
for (let i = 0; i < threads; i++) {
let worker = new Worker(webWorkerURL);
worker.onmessage = (event) => {
workers.forEach(worker => worker.terminate());
worker.terminate();
resolve(event.data);
};
worker.onerror = (event) => {
worker.terminate();
reject();
};
worker.postMessage({
data,
difficulty,
nonce: i,
threads,
});
workers.push(worker);
}
URL.revokeObjectURL(webWorkerURL);
});
}
function processTask() {
return function () {
const sha256 = (text) => {
const encoded = new TextEncoder().encode(text);
return crypto.subtle.digest("SHA-256", encoded.buffer);
};
function uint8ArrayToHexString(arr) {
return Array.from(arr)
.map((c) => c.toString(16).padStart(2, "0"))
.join("");
}
addEventListener('message', async (event) => {
let data = event.data.data;
let difficulty = event.data.difficulty;
let hash;
let nonce = event.data.nonce;
let threads = event.data.threads;
while (true) {
const currentHash = await sha256(data + nonce);
const thisHash = new Uint8Array(currentHash);
let valid = true;
for (let j = 0; j < difficulty; j++) {
const byteIndex = Math.floor(j / 2); // which byte we are looking at
const nibbleIndex = j % 2; // which nibble in the byte we are looking at (0 is high, 1 is low)
let nibble = (thisHash[byteIndex] >> (nibbleIndex === 0 ? 4 : 0)) & 0x0F; // Get the nibble
if (nibble !== 0) {
valid = false;
break;
}
}
if (valid) {
hash = uint8ArrayToHexString(thisHash);
console.log(hash);
break;
}
nonce += threads;
}
postMessage({
hash,
data,
difficulty,
nonce,
});
});
}.toString();
}
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