Add a new TickTimer class to NetEq

webrtc/modules/audio_coding/neteq/tick_timer.h

+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_CODING_NETEQ_TICK_TIMER_H_
+#define WEBRTC_MODULES_AUDIO_CODING_NETEQ_TICK_TIMER_H_
+
+#include <memory>
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+// Implements a time counter. The counter is advanced with the Increment()
+// methods, and is queried with the ticks() accessor. It is assumed that one
+// "tick" och the counter corresponds to 10 ms.
+// A TickTimer object can provide two types of associated time-measuring
+// objects: Stopwatch and Countdown.
+class TickTimer {
+ public:
+  // Stopwatch measures time elapsed since it was started, by querying the
+  // associated TickTimer for the current time. The intended use is to request a
+  // new Stopwatch object from a TickTimer object with the GetNewStopwatch()
+  // method. Note: since the Stopwatch object contains a reference to the
+  // TickTimer it is associated with, it cannot outlive the TickTimer.
+  class Stopwatch {
+   public:
+    explicit Stopwatch(const TickTimer& ticktimer);
+
+    uint64_t ElapsedTicks() const { return ticktimer_.ticks() - starttick_; }
+
+    uint64_t ElapsedMs() const {
+      const uint64_t elapsed_ticks = ticktimer_.ticks() - starttick_;
+      return elapsed_ticks < UINT64_MAX / 10 ? elapsed_ticks * 10 : UINT64_MAX;

[tlegrand-webrtc, 2016/04/21 10:37:44]

The class TickTimer might be usable for other time intervals. Maybe we should
take the number of ms as an input then creating the class instead? If not, I
think 10 ms needs to be somewhere in the name of the class.

[hlundin-webrtc, 2016/04/21 13:50:58]

Acknowledged. I think I'm going to say YAGNI on the variable tick interval, and
just let 10ms be part of the name. Another option is to not have the ElapsedMs()
method, and instead let the caller (NetEq) call ElapsedTicks() and do the
conversion itself. I'll work something out.

[hlundin-webrtc, 2016/04/22 07:46:03]

Updated.

+    }
+
+   private:
+    const TickTimer& ticktimer_;
+    const uint64_t starttick_;
+  };
+
+  // Countdown counts down from a given start value with each tick of the
+  // associated TickTimer, until zero is reached. The Finished() method will
+  // return true if zero has been reached, false otherwise. The intended use is
+  // to request a new Countdown object from a TickTimer object with the
+  // GetNewCountdown() method. Note: since the Countdown object contains a
+  // reference to the TickTimer it is associated with, it cannot outlive the
+  // TickTimer.
+  class Countdown {
+   public:
+    Countdown(const TickTimer& ticktimer, uint64_t ticks_to_count);
+
+    ~Countdown();
+
+    bool Finished() const {
+      return stopwatch_->ElapsedTicks() >= ticks_to_count_;
+    }
+
+   private:
+    const std::unique_ptr<Stopwatch> stopwatch_;
+    const uint64_t ticks_to_count_;
+  };
+
+  TickTimer() {}
+
+  void Increment() { ++ticks_; }
+
+  // Mainly intended for testing.
+  void Increment(uint64_t x) { ticks_ += x; }
+
+  uint64_t ticks() const { return ticks_; }
+
+  // Returns a new Stopwatch object, based on the current TickTimer. Note that
+  // the new Stopwatch object contains a reference to the current TickTimer,
+  // and must therefore not outlive the TickTimer.
+  std::unique_ptr<Stopwatch> GetNewStopwatch() const {
+    return std::unique_ptr<Stopwatch>(new Stopwatch(*this));
+  }
+
+  // Returns a new Countdown object, based on the current TickTimer. Note that
+  // the new Countdown object contains a reference to the current TickTimer,
+  // and must therefore not outlive the TickTimer.
+  std::unique_ptr<Countdown> GetNewCountdown(uint64_t ticks_to_count) const {
+    return std::unique_ptr<Countdown>(new Countdown(*this, ticks_to_count));
+  }
+
+ private:
+  uint64_t ticks_ = 0;
+  RTC_DISALLOW_COPY_AND_ASSIGN(TickTimer);
+};
+
+}  // namespace webrtc
+#endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_TICK_TIMER_H_