futures.js

function Future() {}

Future.mixin({
	didComplete: function(value) {
		if (value === undefined) {
			throw new TypeError('May not return undefined from future');
		}
		this._value = value;
		var fibers = this._fibers;
		if (fibers) {
			delete this._fibers;
			for (var ii = 0; ii < fibers.length; ++ii) {
				fibers[ii].run(value);
			}
		}
	},

	didThrow: function(exception) {
		if (!exception) {
			throw new Error('Must throw non-empty exception!');
		}
		this._exception = exception;
		var fibers = this._fibers;
		if (fibers) {
			delete this._fibers;
			for (var ii = 0; ii < fibers.length; ++ii) {
				fibers[ii].throwInto(exception);
			}
		}
	},

	resolve: function() {
		if (this._exception) {
			throw this._exception;
		} else if (this._value !== undefined) {
			return this._value;
		} else {
			this._fibers = this._fibers || [];
			if (!Fiber.current) {
				throw new Error('Can\'t resolve a future with no fiber!');
			}
			this._fibers.push(Fiber.current);
			return yield();
		}
	},
});

function FiberFuture(fn) {
	var that = this;
	Fiber(function() {
		try {
			that.didComplete(fn());
		} catch(e) {
			that.didThrow(e);
		}
	}).run();
}
FiberFuture.inherit(Future);