Adds reduce implementation and test.

Author: Sebmaster

lib/parallel.js

@@ -144,6 +144,50 @@
 		return this;
 	};
 
+	Parallel.prototype._spawnReduceWorker = function (data, cb, done) {
+		var that = this;
+		var wrk = new Worker(that.options.path);
+		wrk.postMessage(Parallel.getWorkerSource(cb));
+		wrk.postMessage(data);
+		wrk.onmessage = function (msg) {
+			wrk.terminate();
+			that.data[that.data.length] = msg.data;
+			done();
+		};
+	};
+
+	Parallel.prototype.reduce = function (cb) {
+		if (!this.data.length) {
+			throw new Error('Can\'t reduce non-array data');
+		}
+
+		var that = this;
+		function done(data) {
+			if (that.data.length === 1) {
+				that.data = that.data[0];
+				newOp.resolve(null, that.data);
+			} else {
+				that._spawnReduceWorker([that.data[0], that.data[1]], cb, done);
+				that.data.splice(0, 2);
+			}
+		}
+
+		var newOp = new Operation();
+		this.operation.then(function () {
+			if (that.data.length === 1) {
+				newOp.resolve(null, that.data[0]);
+			} else {
+				for (var i = 0; i < that.options.maxWorkers && i < Math.floor(that.data.length / 2); ++i) {
+					that._spawnReduceWorker([that.data[i * 2], that.data[i * 2 + 1]], cb, done);
+				}
+
+				that.data.splice(0, i * 2);
+			}
+		});
+		this.operation = newOp;
+		return this;
+	};
+
 	Parallel.prototype.then = function (cb, errCb) {
 		var that = this;
 		var newOp = new Operation();

test/api.spec.js

@@ -140,6 +140,30 @@
 		});
 	});
 
+	it('should execute .reduce() correctly', function () {
+		var Parallel = require('../lib/parallel.js');
+		var p = new Parallel([1, 2, 3]);
+		var done = false;
+		var result = null;
+
+		runs(function () {
+			p.reduce(function (data) {
+				return data[0] + data[1];
+			}).then(function (data) {
+				result = data;
+				done = true;
+			});
+		});
+
+		waitsFor(function () {
+			return done;
+		}, "it should finish", 500);
+
+		runs(function () {
+			expect(result).toEqual(6);
+		});
+	});
+
 	it('should process data returned from .then()', function () {
 		var Parallel = require('../lib/parallel.js');
 		var p = new Parallel([1, 2, 3]);