text: /*
      This file is a part of libcds - Concurrent Data Structures library
  
      (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
  
      Source code repo: http://github.com/khizmax/libcds/
      Download: http://sourceforge.net/projects/libcds/files/
      
      Redistribution and use in source and binary forms, with or without
      modification, are permitted provided that the following conditions are met:
  
      * Redistributions of source code must retain the above copyright notice, this
        list of conditions and the following disclaimer.
  
      * Redistributions in binary form must reproduce the above copyright notice,
        this list of conditions and the following disclaimer in the documentation
        and/or other materials provided with the distribution.
  
      THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
      AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
      IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
      DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
      FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
      DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
      SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
      CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
      OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.     
  */
  
  #ifndef CDSLIB_URCU_EXEMPT_PTR_H
  #define CDSLIB_URCU_EXEMPT_PTR_H
  
  #include <type_traits>
  #include <cds/details/defs.h>
  
  namespace cds { namespace urcu {
  
      //@cond
      namespace details {
          template <typename Node, typename Value>
          struct conventional_exempt_member_cast
          {
              Value * operator()( Node * p ) const
              {
                  return &p->m_Value;
              }
          };
  
          template <typename Node, typename Value>
          struct conventional_exempt_pair_cast
          {
              Value * operator()( Node * p ) const
              {
                  return &p->m_Data;
              }
          };
      } // namespace details
      //@endcond
  
      /// Exempt pointer for RCU
      /**
          This special pointer class is intended for returning extracted node from RCU-based container.
          The destructor (and \p release() member function) invokes <tt>RCU::retire_ptr< Disposer >()</tt> function to dispose the node.
          For non-intrusive containers from \p cds::container namespace \p Disposer is usually an invocation
          of node deallocator. For intrusive containers the disposer can be empty or it can trigger an event "node can be reused safely".
          In any case, the exempt pointer concept keeps RCU semantics.
          The destructor or \p release() should be called outside the RCU lock of current thread.
  
          You don't need use this helper class directly. Any RCU-based container typedefs a simplified version of this template.
  
          Template arguments:
          - \p RCU - one of \ref cds_urcu_gc "RCU type"
          - \p NodeType - container's node type
          - \p ValueType - value type stored in container's node. For intrusive containers it is the same as \p NodeType
          - \p Disposer - a disposer functor
          - \p Cast - a functor for casting from \p NodeType to \p ValueType. For intrusive containers
              the casting is usually disabled, i.e. \p Cast is \p void.
      */
      template <
          class RCU,
          typename NodeType,
          typename ValueType,
          typename Disposer,
  #ifdef CDS_DOXYGEN_INVOKED
          typename Cast
  #else
          typename Cast=details::conventional_exempt_member_cast<NodeType, ValueType>
  #endif
      >
      class exempt_ptr
      {
          //@cond
          struct trivial_cast {
              ValueType * operator()( NodeType * p ) const
              {
                  return p;
              }
          };
          //@endcond
      public:
          typedef RCU         rcu         ;   ///< RCU type - one of <tt>cds::urcu::gc< ... ></tt>
          typedef NodeType    node_type   ;   ///< Node type
          typedef ValueType   value_type  ;   ///< Value type
          typedef Disposer    disposer    ;   ///< Disposer calling when release
          /// Functor converting \p node_type to \p value_type
          typedef typename std::conditional< std::is_same< Cast, void >::value, trivial_cast, Cast>::type node_to_value_cast;
  
      private:
          //@cond
          node_type *     m_pNode;
          //@endcond
  
      public:
          /// Constructs empty pointer
          exempt_ptr() CDS_NOEXCEPT
              : m_pNode( nullptr )
          {}
  
          //@cond
          /// Creates exempt pointer for \p pNode. Only for internal use.
          explicit exempt_ptr( node_type * pNode ) CDS_NOEXCEPT
              : m_pNode( pNode )
          {}
          explicit exempt_ptr( std::nullptr_t ) CDS_NOEXCEPT
              : m_pNode( nullptr )
          {}
          //@endcond
  
          /// Move ctor
          exempt_ptr( exempt_ptr&& p ) CDS_NOEXCEPT
              : m_pNode( p.m_pNode )
          {
              p.m_pNode = nullptr;
          }
  
          /// The exempt pointer is not copy-constructible
          exempt_ptr( exempt_ptr const& ) = delete;
  
          /// Releases the pointer, see \p release()
          ~exempt_ptr()
          {
              release();
          }
  
          /// Checks if the pointer is \p nullptr
          bool empty() const CDS_NOEXCEPT
          {
              return m_pNode == nullptr;
          }
  
          /// \p bool operator returns <tt>!empty()</tt>
          explicit operator bool() const CDS_NOEXCEPT
          {
              return !empty();
          }
  
          /// Dereference operator
          value_type * operator->() const CDS_NOEXCEPT
          {
              return !empty() ? node_to_value_cast()(m_pNode) : nullptr;
          }
  
          /// Returns a reference to the value
          value_type& operator *() CDS_NOEXCEPT
          {
              assert( !empty());
              return *node_to_value_cast()( m_pNode );
          }
  
          /// Move assignment. Can be called only outside of RCU critical section
          exempt_ptr& operator =( exempt_ptr&& p ) CDS_NOEXCEPT
          {
              release();
              m_pNode = p.m_pNode;
              p.m_pNode = nullptr;
              return *this;
          }
  
          /// The exempt pointer is not copy-assignable
          exempt_ptr& operator=(exempt_ptr const&) = delete;
  
          /// Disposes the pointer. Should be called only outside of RCU critical section
          void release()
          {
              if ( !empty() ) {
                  assert( !rcu::is_locked() );
                  rcu::template retire_ptr<disposer>( m_pNode );
                  m_pNode = nullptr;
              }
          }
      };
  }} // namespace cds::urcu
  
  #endif //#ifndef CDSLIB_URCU_EXEMPT_PTR_H
  