bitmessage-js/lib/platform.browser.js

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/**
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* Browser implementation of platform-specific routines.
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*/
"use strict";
var hash = require("hash.js");
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var BN = require("bn.js");
var assert = require("./util").assert;
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exports.sha512 = function(buf) {
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return new Buffer(hash.sha512().update(buf).digest());
};
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exports.sha256 = function(buf) {
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return new Buffer(hash.sha256().update(buf).digest());
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};
exports.ripemd160 = function(buf) {
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return new Buffer(hash.ripemd160().update(buf).digest());
};
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exports.randomBytes = function(size) {
var arr = new Uint8Array(size);
window.crypto.getRandomValues(arr);
return new Buffer(arr);
};
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// See `platform.js` for comments.
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var B64 = new BN("18446744073709551616");
exports.getTarget = function(opts) {
var length = new BN(opts.payloadLength);
length.iaddn(8);
length.iaddn(opts.payloadLengthExtraBytes);
var denominator = new BN(opts.ttl);
denominator.imul(length);
denominator.idivn(65536);
denominator.iadd(length);
denominator.imul(new BN(opts.nonceTrialsPerByte));
var target = parseInt(B64.div(denominator).toString(16), 16);
assert(target <= 9007199254740991, "Unsafe target");
return target;
};
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var FAILBACK_POOL_SIZE = 8;
// NOTE(Kagami): We don't use promise shim in Browser implementation
// because it's supported natively in new browsers (see
// <http://caniuse.com/#feat=promises>) and we can use only new browsers
// because of the WebCryptoAPI (see
// <http://caniuse.com/#feat=cryptography>).
exports.doPOW = function(opts) {
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// Try to get CPU cores count otherwise fallback to default value.
// Currenty navigator's concurrency property available in Chrome and
// not available in Firefox; hope default value won't slow down POW
// speed much on systems with 1 or 2 cores. There are core estimator
// libraries exist (see <https://stackoverflow.com/q/3289465>) but
// they are buggy. Ulimately library user could adjust pool size
// manually.
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var poolSize = opts.poolSize || navigator.hardwareConcurrency;
poolSize = poolSize || FAILBACK_POOL_SIZE;
// Check all input params prematurely to not let promise executor or
// worker to fail because of it.
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assert(poolSize > 0, "Pool size is too low");
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assert(opts.workerUrl, "Bad worker URL");
assert(typeof opts.target === "number", "Bad target");
assert(Buffer.isBuffer(opts.initialHash), "Bad initial hash");
var cancel;
var promise = new Promise(function(resolve, reject) {
function terminateAll() {
while (workers.length) {
workers.shift().terminate();
}
}
function onmessage(e) {
terminateAll();
if (e.data >= 0) {
resolve(e.data);
} else {
// It's very unlikely that execution will ever reach this place.
// Currently the only reason why Worker may return value less
// than zero is a 32-bit nonce overflow (see worker
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// implementation). It's 4G double hashes.
reject(new Error("uint32_t nonce overflow"));
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}
}
function onerror(e) {
// XXX(Kagami): `onerror` events fires in Chrome even after all
// workers were terminated. It doesn't cause wrong behaviour but
// beware that this function may be executed several times.
terminateAll();
reject(e);
}
var workers = [];
var worker;
for (var i = 0; i < poolSize; i++) {
worker = new Worker(opts.workerUrl);
workers.push(worker);
// NOTE(Kagami): There is no race condition here. `onmessage` can
// only be called _after_ this for-loop finishes. See
// <https://stackoverflow.com/a/18192122> for details.
worker.onmessage = onmessage;
worker.onerror = onerror;
worker.postMessage({
num: i,
poolSize: poolSize,
target: opts.target,
initialHash: opts.initialHash,
});
}
cancel = function(e) {
terminateAll();
reject(e);
};
});
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// Allow to stop a POW via custom function added to the Promise
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// instance.
promise.cancel = cancel;
return promise;
};