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/* promise.vala
*
* Copyright (C) 2013 Maciej Piechotka
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Author:
* Maciej Piechotka <uzytkownik2@gmail.com>
*/
using GLib;
/**
* Promise allows to set a value with associated {@link Future}. Please note that
* value can be stored only once.
*
* Typically the producer will create promise and return {@link future} while
* keeping the promise to itself. Then when value is ready it can call {@link set_value}.
*
* @see Future
* @see task
* @since 0.11.0
*/
public class Gee.Promise<G> {
public Promise () {
_future = new Future<G> ();
}
~Promise () {
_future.abandon ();
}
/**
* {@link Future} value of this promise
*/
public Gee.Future<G> future {
get {
return _future;
}
}
/**
* Sets the value of the future.
*
* @param value Value of future
*/
public void set_value (owned G value) {
_future.set_value ((owned)value);
}
/**
* Sets the exception.
*
* @param exception Exception thrown
*/
public void set_exception (owned GLib.Error exception) {
_future.set_exception ((owned)exception);
}
private class Future<G> : Object, Gee.Future<G> {
public Future () {
_when_done = new Gee.Future.SourceFuncArrayElement<G>[0];
}
public bool ready {
get {
_mutex.lock ();
bool result = _state != State.INIT;
_mutex.unlock ();
return result;
}
}
public GLib.Error? exception {
get {
return _exception;
}
}
public unowned G wait () throws FutureError {
_mutex.lock ();
State state = _state;
while (_state == State.INIT) {
_set.wait (_mutex);
state = _state;
}
_mutex.unlock ();
switch (state) {
case State.ABANDON:
throw new FutureError.ABANDON_PROMISE ("Promise has been abandon");
case State.EXCEPTION:
throw new FutureError.EXCEPTION ("Exception has been thrown");
case State.READY:
return _value;
default:
assert_not_reached ();
}
}
public bool wait_until (int64 end_time, out unowned G? value = null) throws FutureError {
_mutex.lock ();
State state = _state;
bool res = true;
while (_state == State.INIT) {
res = _set.wait_until (_mutex, end_time);
if (!res) {
break;
}
state = _state;
}
_mutex.unlock ();
if (!res) {
value = null;
return false;
}
switch (state) {
case State.ABANDON:
throw new FutureError.ABANDON_PROMISE ("Promise has been abandon");
case State.EXCEPTION:
throw new FutureError.EXCEPTION ("Exception has been thrown");
case State.READY:
value = _value;
return true;
default:
assert_not_reached ();
}
}
public async unowned G wait_async () throws Gee.FutureError {
_mutex.lock ();
State state = _state;
if (state == State.INIT) {
_when_done += SourceFuncArrayElement(wait_async.callback);
yield Gee.Utils.Async.yield_and_unlock (_mutex);
state = _state;
} else {
_mutex.unlock ();
}
assert (state != State.INIT);
switch (state) {
case State.ABANDON:
throw new FutureError.ABANDON_PROMISE ("Promise has been abandon");
case State.EXCEPTION:
throw new FutureError.EXCEPTION ("Exception has been thrown");
case State.READY:
return _value;
default:
assert_not_reached ();
}
}
internal void set_value (owned G value) {
_mutex.lock ();
assert (_state == State.INIT);
_state = State.READY;
_value = (owned)value;
_set.broadcast ();
_mutex.unlock ();
Gee.Future.SourceFuncArrayElement<G>[] when_done = (owned)_when_done;
for (int i = 0; i < when_done.length; i++) {
when_done[i].func ();
}
}
internal void set_exception (owned GLib.Error? exception) {
_mutex.lock ();
assert (_state == State.INIT);
_state = State.EXCEPTION;
_exception = (owned)exception;
_set.broadcast ();
_mutex.unlock ();
Gee.Future.SourceFuncArrayElement<G>[] when_done = (owned)_when_done;
for (int i = 0; i < when_done.length; i++) {
when_done[i].func ();
}
}
internal void abandon () {
_mutex.lock ();
if (_state != State.INIT) {
_mutex.unlock ();
return;
}
assert (_state == State.INIT);
_state = State.ABANDON;
_set.broadcast ();
_mutex.unlock ();
Gee.Future.SourceFuncArrayElement<G>[] when_done = (owned)_when_done;
for (int i = 0; i < when_done.length; i++) {
when_done[i].func ();
}
}
private Mutex _mutex = Mutex ();
private Cond _set = Cond ();
private State _state;
private G? _value;
private GLib.Error? _exception;
private Gee.Future.SourceFuncArrayElement<G>[]? _when_done;
private enum State {
INIT,
ABANDON,
EXCEPTION,
READY
}
}
private Future<G> _future;
}
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