From 3229d748876729718edc3d4c100575e7a73525a8 Mon Sep 17 00:00:00 2001
From: Yanis Benson <yanis.benson@gmail.com>
Date: Fri, 3 May 2019 09:48:26 +0300
Subject: [PATCH] Move hashing to worker thread (#7)

---
 .travis.yml  |  1 +
 index.js     | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 package.json | 10 ++++++--
 readme.md    |  2 +-
 test.js      | 14 +++++++++++
 thread.js    | 12 +++++++++
 6 files changed, 106 insertions(+), 4 deletions(-)
 create mode 100644 thread.js

diff --git a/.travis.yml b/.travis.yml
index f3fa8cd..f98fed0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,4 +1,5 @@
 language: node_js
 node_js:
+  - '12'
   - '10'
   - '8'
diff --git a/index.js b/index.js
index eeaeb50..cf7367d 100644
--- a/index.js
+++ b/index.js
@@ -1,7 +1,50 @@
 'use strict';
 const crypto = require('crypto');
 
-const create = algorithm => async (buffer, options) => {
+const requireOptional = (name, defaultValue) => {
+	try {
+		return require(name);
+	} catch (_) {
+		return defaultValue;
+	}
+};
+
+const {Worker} = requireOptional('worker_threads', {});
+
+let worker; // Lazy
+let taskIdCounter = 0;
+const tasks = new Map();
+
+const createWorker = () => {
+	worker = new Worker('./thread.js');
+	worker.on('message', message => {
+		const task = tasks.get(message.id);
+		tasks.delete(message.id);
+		if (tasks.size === 0) {
+			worker.unref();
+		}
+
+		task(message.value);
+	});
+
+	worker.on('error', error => {
+		// Any error here is effectively an equivalent of segfault and have no scope, so we just throw it on callback level
+		throw error;
+	});
+};
+
+const taskWorker = (value, transferList) => new Promise(resolve => {
+	const id = taskIdCounter++;
+	tasks.set(id, resolve);
+
+	if (worker === undefined) {
+		createWorker();
+	}
+
+	worker.postMessage({id, value}, transferList);
+});
+
+let create = algorithm => async (buffer, options) => {
 	options = {
 		outputFormat: 'hex',
 		...options
@@ -17,6 +60,32 @@ const create = algorithm => async (buffer, options) => {
 	return hash.digest().buffer;
 };
 
+if (Worker !== undefined) {
+	create = algorithm => async (source, options) => {
+		options = {
+			outputFormat: 'hex',
+			...options
+		};
+
+		let buffer;
+		if (typeof source === 'string') {
+			// Saving one copy operation by writing string to buffer right away and then transfering buffer
+			buffer = new ArrayBuffer(Buffer.byteLength(source, 'utf8'));
+			Buffer.from(buffer).write(source, 'utf8');
+		} else {
+			// Creating a copy of buffer at call time, will be transfered later
+			buffer = source.buffer.slice(0);
+		}
+
+		const result = await taskWorker({algorithm, buffer}, [buffer]);
+		if (options.outputFormat === 'hex') {
+			return Buffer.from(result).toString('hex');
+		}
+
+		return result;
+	};
+}
+
 exports.sha1 = create('sha1');
 exports.sha256 = create('sha256');
 exports.sha384 = create('sha384');
diff --git a/package.json b/package.json
index d3a9751..f08d750 100644
--- a/package.json
+++ b/package.json
@@ -18,7 +18,8 @@
 	"files": [
 		"index.js",
 		"index.d.ts",
-		"browser.js"
+		"browser.js",
+		"thread.js"
 	],
 	"keywords": [
 		"crypto",
@@ -41,5 +42,10 @@
 		"tsd": "^0.7.2",
 		"xo": "^0.24.0"
 	},
-	"browser": "browser.js"
+	"browser": "browser.js",
+	"xo": {
+		"rules": {
+			"import/no-unresolved": "off"
+		}
+	}
 }
diff --git a/readme.md b/readme.md
index 90afd68..34d6c2b 100644
--- a/readme.md
+++ b/readme.md
@@ -41,7 +41,7 @@ const {sha256} = require('crypto-hash');
 
 Returns a `Promise<string>` with a hex-encoded hash.
 
-*Note that even though it returns a promise, [in Node.js, the operation is synchronous 💩](https://github.com/nodejs/node/issues/678).*
+*In Node.js 12 or later, the operation is executed using [`worker_threads`](https://nodejs.org/api/worker_threads.html). A thread is lazily spawned on the first operation and lives until the end of the program execution. It's `unref`ed, so it won't keep the process alive.*
 
 [SHA-1 is insecure](https://stackoverflow.com/a/38045085/64949) and should not be used for anything sensitive.
 
diff --git a/test.js b/test.js
index 1079524..c2f3dac 100644
--- a/test.js
+++ b/test.js
@@ -34,3 +34,17 @@ test('buffer output', async t => {
 	const result = await sha1('🦄', {outputFormat: 'buffer'});
 	t.is(is(result), 'ArrayBuffer');
 });
+
+test('parallel execution', async t => {
+	const promises = [];
+	for (let i = 0; i < 10; i++) {
+		promises.push(sha512('🦄'));
+	}
+
+	const results = await Promise.all(promises);
+	t.is(results.length, promises.length);
+
+	for (const result of results) {
+		t.is(result, '7d9e515c59bd15d0692f9bc0c68f50f82b62a99bef4b8dc490cec165296210dff005529a4cb84a655eee6ddec82339e6bdbab21bdb287b71a543a56cfab53905');
+	}
+});
diff --git a/thread.js b/thread.js
new file mode 100644
index 0000000..eaac620
--- /dev/null
+++ b/thread.js
@@ -0,0 +1,12 @@
+'use strict';
+const crypto = require('crypto');
+const {parentPort} = require('worker_threads');
+
+parentPort.on('message', message => {
+	const {algorithm, buffer} = message.value;
+	const hash = crypto.createHash(algorithm);
+	hash.update(Buffer.from(buffer));
+	const arrayBuffer = hash.digest().buffer;
+	// Transfering buffer here for consistency, but considering buffer size it might be faster to just leave it for copying, needs perf test
+	parentPort.postMessage({id: message.id, value: arrayBuffer}, [arrayBuffer]);
+});