bitmessage-js/lib/worker.browser.js

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2015-01-09 14:12:23 +01:00
/**
* Web Worker routines for Browser platform.
*/
"use strict";
// NOTE(Kagami): In order to use it you need to create separate
// browserify bundle for this file, place it somewhere in your HTTP
// server assets path (under the same origin with your application code)
// and then pass appropriate `workerUrl` value to the function that
// spawns workers.
// You may also try to pass object URL instead. See
// <http://mdn.io/worker.worker>, <https://stackoverflow.com/q/10343913>
// for details.
// XXX(Kagami): This is rather unpleasent that we use different SHA-2
// implementations for main library code and for worker code (we use
// `sha.js` here because it's faster). Though worker code lays in
// separate file so it shouldn't result in any download overhead.
var createHash = require("sha.js");
function sha512(buf) {
return createHash("sha512").update(buf).digest();
}
function pow(opts) {
var nonce = opts.num;
var poolSize = opts.poolSize;
var message = new Buffer(72);
message.fill(0);
Buffer(opts.initialHash).copy(message, 8);
var targetHi = Math.floor(opts.target / 4294967296);
var targetLo = opts.target % 4294967296;
var digest, trialHi, trialLo;
while (true) {
// uint32_t overflow. There is no much need to fix it since 4G
// double hashes would we computed too long anyway in a Browser.
if (nonce > 4294967295) {
return -1;
}
message.writeUInt32BE(nonce, 4, true);
digest = sha512(sha512(message));
trialHi = digest.readUInt32BE(0, true);
if (trialHi > targetHi) {
nonce += poolSize;
} else if (trialHi === targetHi) {
trialLo = digest.readUInt32BE(4, true);
if (trialLo > targetLo) {
nonce += poolSize;
} else {
return nonce;
}
} else {
return nonce;
}
}
}
onmessage = function(e) { // jshint ignore:line
var nonce = pow(e.data);
postMessage(nonce); // jshint ignore:line
};