enable_shared_from_this.h

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// This file wraps enable_shared_from_this so that it is more flexible
#ifndef included_AMP_enable_shared_from_this
#define included_AMP_enable_shared_from_this
 
#include "AMP/utils/UtilityMacros.h"
 
#include <memory>
 
 
namespace AMP {
 
 
template<class T>
class enable_shared_from_this : public std::enable_shared_from_this<T>
{
public:
    std::shared_ptr<T> shared_from_this()
    {
        std::shared_ptr<T> ptr;
        if ( weak_ptr_.use_count() == 0 ) {
            T *tmp = dynamic_cast<T *>( this );
            AMP_ASSERT( tmp != NULL );
            try {
                std::enable_shared_from_this<T> *tmp2 = this;
                ptr                                   = tmp2->shared_from_this();
            } catch ( ... ) {
                ptr = std::shared_ptr<T>( tmp, []( void * ) {} );
            }
            weak_ptr_ = ptr;
        } else {
            ptr = std::shared_ptr<T>( weak_ptr_ );
        }
        return ptr;
    }
    std::shared_ptr<const T> shared_from_this() const
    {
        std::shared_ptr<const T> ptr;
        if ( weak_ptr_.use_count() == 0 ) {
            const T *tmp = dynamic_cast<const T *>( this );
            AMP_ASSERT( tmp != NULL );
            try {
                const std::enable_shared_from_this<T> *tmp2 = this;
                ptr                                         = tmp2->shared_from_this();
            } catch ( ... ) {
                // Note: Clang on MAC has issues with the const version of this line, hence the
                // const_cast
                ptr = std::shared_ptr<T>( const_cast<T *>( tmp ), []( void * ) {} );
            }
            weak_ptr_ = std::const_pointer_cast<T>( ptr );
        } else {
            ptr = std::shared_ptr<const T>( weak_ptr_ );
        }
        return ptr;
    }
    virtual ~enable_shared_from_this() = default;
 
protected:
    mutable std::weak_ptr<T> weak_ptr_;
};
 
 
} // namespace AMP
 
#endif