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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
part of dart.async;
/**
* A count-down timer that can be configured to fire once or repeatedly.
*
* The timer counts down from the specified duration to 0.
* When the timer reaches 0, the timer invokes the specified callback function.
* Use a periodic timer to repeatedly count down the same interval.
*
* A negative duration is treated the same as a duration of 0.
* If the duration is statically known to be 0, consider using [run].
*
* Frequently the duration is either a constant or computed as in the
* following example (taking advantage of the multiplication operator of
* the [Duration] class):
*
* const TIMEOUT = const Duration(seconds: 3);
* const ms = const Duration(milliseconds: 1);
*
* startTimeout([int milliseconds]) {
* var duration = milliseconds == null ? TIMEOUT : ms * milliseconds;
* return new Timer(duration, handleTimeout);
* }
* ...
* void handleTimeout() { // callback function
* ...
* }
*
* Note: If Dart code using Timer is compiled to JavaScript, the finest
* granularity available in the browser is 4 milliseconds.
*
* See [Stopwatch] for measuring elapsed time.
*/
abstract class Timer {
/**
* Creates a new timer.
*
* The [callback] function is invoked after the given [duration].
*
*/
factory Timer(Duration duration, void callback()) {
if (Zone.current == Zone.ROOT) {
// No need to bind the callback. We know that the root's timer will
// be invoked in the root zone.
return Zone.current.createTimer(duration, callback);
}
return Zone.current.createTimer(
duration, Zone.current.bindCallback(callback, runGuarded: true));
}
/**
* Creates a new repeating timer.
*
* The [callback] is invoked repeatedly with [duration] intervals until
* canceled with the [cancel] function.
*
* The exact timing depends on the underlying timer implementation.
* No more than `n` callbacks will be made in `duration * n` time,
* but the time between two consecutive callbacks
* can be shorter and longer than `duration`.
*
* In particular, an implementation may schedule the next callback, e.g.,
* a `duration` after either when the previous callback ended,
* when the previous callback started, or when the previous callback was
* scheduled for - even if the actual callback was delayed.
*/
factory Timer.periodic(Duration duration, void callback(Timer timer)) {
if (Zone.current == Zone.ROOT) {
// No need to bind the callback. We know that the root's timer will
// be invoked in the root zone.
return Zone.current.createPeriodicTimer(duration, callback);
}
// TODO(floitsch): the return type should be 'void', and the type
// should be inferred.
var boundCallback = Zone.current
.bindUnaryCallback<dynamic, Timer>(callback, runGuarded: true);
return Zone.current.createPeriodicTimer(duration, boundCallback);
}
/**
* Runs the given [callback] asynchronously as soon as possible.
*
* This function is equivalent to `new Timer(Duration.ZERO, callback)`.
*/
static void run(void callback()) {
new Timer(Duration.ZERO, callback);
}
/**
* Cancels the timer.
*/
void cancel();
/**
* Returns whether the timer is still active.
*
* A non-periodic timer is active if the callback has not been executed,
* and the timer has not been canceled.
*
* A periodic timer is active if it has not been canceled.
*/
bool get isActive;
static Timer _createTimer(Duration duration, void callback()) {
// TODO(iposva): Remove _TimerFactory and use VMLibraryHooks exclusively.
if (_TimerFactory._factory == null) {
_TimerFactory._factory = VMLibraryHooks.timerFactory as _TimerFactoryClosure;
}
if (_TimerFactory._factory == null) {
throw new UnsupportedError("Timer interface not supported.");
}
int milliseconds = duration.inMilliseconds;
if (milliseconds < 0) milliseconds = 0;
return _TimerFactory._factory(milliseconds, (_) {
callback();
}, false);
}
static Timer _createPeriodicTimer(
Duration duration, void callback(Timer timer)) {
// TODO(iposva): Remove _TimerFactory and use VMLibraryHooks exclusively.
if (_TimerFactory._factory == null) {
_TimerFactory._factory = VMLibraryHooks.timerFactory as _TimerFactoryClosure;
}
if (_TimerFactory._factory == null) {
throw new UnsupportedError("Timer interface not supported.");
}
int milliseconds = duration.inMilliseconds;
if (milliseconds < 0) milliseconds = 0;
return _TimerFactory._factory(milliseconds, callback, true);
}
}