semaphore.hpp

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#pragma once
 
#include <condition_variable>
#include <mutex>
 
namespace cras
{
 
class ReverseSemaphore
{
public:
  explicit ReverseSemaphore(bool waitZeroAtDestroy = true);
 
  ~ReverseSemaphore();
 
  bool acquire();
 
  void release();
 
  bool waitZero();
 
  void disable();
 
  void enable();
 
  bool isEnabled() const;
 
  size_t getCount() const;
 
private:
  bool waitZeroAtDestroy;
 
  bool isDestroying {false};
 
  volatile size_t count {0};
 
  volatile bool disabled {false};
 
  mutable ::std::mutex mutex;
 
  ::std::condition_variable cv;
};
 
template <typename T>
class SemaphoreGuard
{
public:
  explicit SemaphoreGuard(T& semaphore) : semaphore(semaphore)
  {
    this->acquireSucceeded = this->semaphore.acquire();
  }
 
  ~SemaphoreGuard()
  {
    if (this->acquireSucceeded)
      this->semaphore.release();
  }
 
  bool acquired() const
  {
    return this->acquireSucceeded;
  }
 
private:
  T& semaphore;
 
  bool acquireSucceeded {false};
};
}