src/kudu/util/semaphore.h

// Copyright 2013 Cloudera, Inc.
//
// 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 KUDU_UTIL_SEMAPHORE_H
#define KUDU_UTIL_SEMAPHORE_H

#include <semaphore.h>

#include "kudu/gutil/macros.h"
#include "kudu/gutil/port.h"
#include "kudu/util/monotime.h"

namespace kudu {

// Wrapper for POSIX semaphores.
class Semaphore {
 public:
  // Initialize the semaphore with the specified capacity.
  explicit Semaphore(int capacity);
  ~Semaphore();

  // Acquire the semaphore.
  void Acquire();

  // Acquire the semaphore within the given timeout. Returns true if successful.
  bool TimedAcquire(const MonoDelta& timeout);

  // Try to acquire the semaphore immediately. Returns false if unsuccessful.
  bool TryAcquire();

  // Release the semaphore.
  void Release();

  // Get the current value of the semaphore.
  int GetValue();

  // Boost-compatible wrappers.
  void lock() { Acquire(); }
  void unlock() { Release(); }
  bool try_lock() { return TryAcquire(); }

 private:
  // Log a fatal error message. Separated out to keep the main functions
  // as small as possible in terms of code size.
  void Fatal(const char* action) ATTRIBUTE_NORETURN;

  sem_t sem_;
  DISALLOW_COPY_AND_ASSIGN(Semaphore);
};

} // namespace kudu
#endif /* KUDU_UTIL_SEMAPHORE_H */