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pkg/dev_compiler/tool/input_sdk/lib/core/stopwatch.dart

-// Copyright (c) 2011, 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.core;
-
-/**
- * A simple stopwatch interface to measure elapsed time.
- */
-class Stopwatch {
-  /**
-   * Frequency of the elapsed counter in Hz.
-   */
-  int get frequency => _frequency;
-
-  // The _start and _stop fields capture the time when [start] and [stop]
-  // are called respectively.
-  // If _start is null, then the [Stopwatch] has not been started yet.
-  // If _stop is null, then the [Stopwatch] has not been stopped yet,
-  // or is running.
-  int _start;
-  int _stop;
-
-  /**
-   * Creates a [Stopwatch] in stopped state with a zero elapsed count.
-   *
-   * The following example shows how to start a [Stopwatch]
-   * immediately after allocation.
-   *
-   *     Stopwatch stopwatch = new Stopwatch()..start();
-   */
-  Stopwatch() {
-    _initTicker();
-  }
-
-  /**
-   * Starts the [Stopwatch].
-   *
-   * The [elapsed] count is increasing monotonically. If the [Stopwatch] has
-   * been stopped, then calling start again restarts it without resetting the
-   * [elapsed] count.
-   *
-   * If the [Stopwatch] is currently running, then calling start does nothing.
-   */
-  void start() {
-    if (isRunning) return;
-    if (_start == null) {
-      // This stopwatch has never been started.
-      _start = _now();
-    } else {
-      // Restart this stopwatch. Prepend the elapsed time to the current
-      // start time.
-      _start = _now() - (_stop - _start);
-      _stop = null;
-    }
-  }
-
-  /**
-   * Stops the [Stopwatch].
-   *
-   * The [elapsedTicks] count stops increasing after this call. If the
-   * [Stopwatch] is currently not running, then calling this method has no
-   * effect.
-   */
-  void stop() {
-    if (!isRunning) return;
-    _stop = _now();
-  }
-
-  /**
-   * Resets the [elapsed] count to zero.
-   *
-   * This method does not stop or start the [Stopwatch].
-   */
-  void reset() {
-    if (_start == null) return;
-    // If [_start] is not null, then the stopwatch had already been started. It
-    // may running right now.
-    _start = _now();
-    if (_stop != null) {
-      // The watch is not running. So simply set the [_stop] to [_start] thus
-      // having an elapsed time of 0.
-      _stop = _start;
-    }
-  }
-
-  /**
-   * Returns the elapsed number of clock ticks since calling [start] while the
-   * [Stopwatch] is running.
-   *
-   * Returns the elapsed number of clock ticks between calling [start] and
-   * calling [stop].
-   *
-   * Returns 0 if the [Stopwatch] has never been started.
-   *
-   * The elapsed number of clock ticks increases by [frequency] every second.
-   */
-  int get elapsedTicks {
-    if (_start == null) {
-      return 0;
-    }
-    return (_stop == null) ? (_now() - _start) : (_stop - _start);
-  }
-
-  /**
-   * Returns the [elapsedTicks] counter converted to a [Duration].
-   */
-  Duration get elapsed {
-    return new Duration(microseconds: elapsedMicroseconds);
-  }
-
-  /**
-   * Returns the [elapsedTicks] counter converted to microseconds.
-   */
-  int get elapsedMicroseconds {
-    return (elapsedTicks * 1000000) ~/ frequency;
-  }
-
-  /**
-   * Returns the [elapsedTicks] counter converted to milliseconds.
-   */
-  int get elapsedMilliseconds {
-    return (elapsedTicks * 1000) ~/ frequency;
-  }
-
-
-  /**
-   * Returns wether the [StopWatch] is currently running.
-   */
-  bool get isRunning => _start != null && _stop == null;
-
-  /**
-   * Cached frequency of the system. Must be initialized in [_initTicker];
-   */
-  static int _frequency;
-
-  /**
-   * Initializes the time-measuring system. *Must* initialize the [_frequency]
-   * variable.
-   */
-  external static void _initTicker();
-  external static int _now();
-}