/* Copyright 2015 The TensorFlow Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#ifndef TENSORFLOW_STREAM_EXECUTOR_TIMER_H_
#define TENSORFLOW_STREAM_EXECUTOR_TIMER_H_

#include <memory>

#include "tensorflow/stream_executor/platform/port.h"

namespace stream_executor {

namespace internal {
class TimerInterface;
}  // namespace internal

class StreamExecutor;

// An interval timer, suitable for use in timing the operations which occur in
// streams.
//
// Thread-hostile: CUDA associates a CUDA-context with a particular thread in
// the system. Any operation that a user attempts to perform by using a Timer
// on a thread not-associated with the CUDA-context has unknown behavior at the
// current time; see b/13176597
class Timer {
 public:
  // Instantiate a timer tied to parent as a platform executor.
  explicit Timer(StreamExecutor *parent);

  // Deallocates any timer resources that the parent StreamExecutor has bestowed
  // upon this object.
  ~Timer();

  // Returns the elapsed number of microseconds for a completed timer.
  // Completed means has been through a start/stop lifecycle.
  uint64_t Microseconds() const;

  // Returns the elapsed number of nanoseconds for a completed timer.
  // Completed means has been through a start/stop lifecycle.
  uint64_t Nanoseconds() const;

  // Returns the (opaque) backing platform ITimer instance. Ownership is
  // not transferred to the caller.
  internal::TimerInterface *implementation() { return implementation_.get(); }

 private:
  // The StreamExecutor that manages the platform-specific internals for this
  // timer.
  StreamExecutor *parent_;

  // Platform-dependent implementation of the timer internals for the underlying
  // platform. This class just delegates to this opaque instance.
  std::unique_ptr<internal::TimerInterface> implementation_;

  SE_DISALLOW_COPY_AND_ASSIGN(Timer);
};

}  // namespace stream_executor

#endif  // TENSORFLOW_STREAM_EXECUTOR_TIMER_H_
