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/checks.h"
+#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_;
+      const int ms_per_tick = ticktimer_.ms_per_tick();
+      return elapsed_ticks < UINT64_MAX / ms_per_tick
+                 ? elapsed_ticks * ms_per_tick
+                 : UINT64_MAX;
+    }
+
+   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() : TickTimer(10) {}
+  explicit TickTimer(int ms_per_tick) : ms_per_tick_(ms_per_tick) {
+    RTC_DCHECK_GT(ms_per_tick_, 0);
+  }
+
+  void Increment() { ++ticks_; }
+
+  // Mainly intended for testing.
+  void Increment(uint64_t x) { ticks_ += x; }
+
+  uint64_t ticks() const { return ticks_; }
+
+  int ms_per_tick() const { return ms_per_tick_; }
+
+  // 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;
+  const int ms_per_tick_;
+  RTC_DISALLOW_COPY_AND_ASSIGN(TickTimer);
+};
+
+}  // namespace webrtc
+#endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_TICK_TIMER_H_