util_semaphore.h

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/*
 * Copyright 2011-2020 Blender Foundation
 *
 * 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 __UTIL_SEMAPHORE_H__
#define __UTIL_SEMAPHORE_H__
 
#include "util/util_thread.h"
 
CCL_NAMESPACE_BEGIN
 
/* Counting Semaphore
 *
 * To restrict concurrent access to a resource to a specified number
 * of threads. Similar to std::counting_semaphore from C++20. */
 
class thread_counting_semaphore {
 public:
  explicit thread_counting_semaphore(const int count) : count(count)
  {
  }
 
  thread_counting_semaphore(const thread_counting_semaphore &) = delete;
 
  void acquire()
  {
    thread_scoped_lock lock(mutex);
    while (count == 0) {
      condition.wait(lock);
    }
    count--;
  }
 
  void release()
  {
    thread_scoped_lock lock(mutex);
    count++;
    condition.notify_one();
  }
 
 protected:
  thread_mutex mutex;
  thread_condition_variable condition;
  int count;
};
 
CCL_NAMESPACE_END
 
#endif /* __UTIL_SEMAPHORE_H__ */