sapphire/src/common/Util/LockedWaitQueue.h

#ifndef _LOCKED_WAIT_H
#define _LOCKED_WAIT_H

#include <condition_variable>
#include <mutex>
#include <queue>
#include <atomic>
#include <type_traits>
#include <utility>

namespace Sapphire
{

  template< typename T >
  class LockedWaitQueue
  {
  private:
    std::mutex m_queueLock;
    std::queue< T > m_queue;
    std::condition_variable m_condition;
    std::atomic< bool > m_shutdown;

  public:

    LockedWaitQueue< T >() :
      m_shutdown( false )
    {
    }

    void push( const T& value )
    {
      std::lock_guard< std::mutex > lock( m_queueLock );
      m_queue.push( std::move( value ) );

      m_condition.notify_one();
    }

    bool empty()
    {
      std::lock_guard< std::mutex > lock( m_queueLock );

      return m_queue.empty();
    }

    bool pop( T& value )
    {
      std::lock_guard< std::mutex > lock( m_queueLock );

      if( m_queue.empty() || m_shutdown )
        return false;

      value = m_queue.front();

      m_queue.pop();

      return true;
    }

    void waitAndPop( T& value )
    {
      std::unique_lock< std::mutex > lock( m_queueLock );

      while( m_queue.empty() && !m_shutdown )
        m_condition.wait( lock );

      if( m_queue.empty() || m_shutdown )
        return;

      value = m_queue.front();

      m_queue.pop();
    }

    void cancel()
    {
      std::unique_lock< std::mutex > lock( m_queueLock );

      while( !m_queue.empty() )
      {
        T& value = m_queue.front();

        deleteQueuedObject( value );

        m_queue.pop();
      }

      m_shutdown = true;

      m_condition.notify_all();
    }

  private:
    template< typename E = T >
    typename std::enable_if< std::is_pointer< E >::value >::type deleteQueuedObject( E& obj )
    {
      delete obj;
    }

    template< typename E = T >
    typename std::enable_if< !std::is_pointer< E >::value >::type deleteQueuedObject( E const& )
    {
    }
  };
}

#endif