boost/spirit/home/support/iterators/detail/ref_counted_policy.hpp

//  Copyright (c) 2001, Daniel C. Nuffer
//  Copyright (c) 2001-2008, Hartmut Kaiser
// 
//  Distributed under the Boost Software License, Version 1.0. (See accompanying
//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#if !defined(BOOST_SPIRIT_ITERATOR_REF_COUNTED_POLICY_MAR_16_2007_1108AM)
#define BOOST_SPIRIT_ITERATOR_REF_COUNTED_POLICY_MAR_16_2007_1108AM

#include <boost/spirit/home/support/iterators/multi_pass_fwd.hpp>
#include <boost/spirit/home/support/iterators/detail/multi_pass.hpp>
#include <cstdlib>

namespace boost { namespace spirit { namespace multi_pass_policies
{
    ///////////////////////////////////////////////////////////////////////////
    //  class ref_counted
    //  Implementation of an OwnershipPolicy used by multi_pass.
    //
    //  Implementation modified from RefCounted class from the Loki library by
    //  Andrei Alexandrescu.
    ///////////////////////////////////////////////////////////////////////////
    struct ref_counted
    {
        ///////////////////////////////////////////////////////////////////////
        struct unique // : detail::default_ownership_policy
        {
            void swap(unique&) {}

            // clone is called when a copy of the iterator is made, so 
            // increment the ref-count.
            template <typename MultiPass>
            static void clone(MultiPass& mp)
            {
                if (0 != mp.shared)
                    ++mp.shared->count;
            }

            // called when a copy is deleted. Decrement the ref-count. Return
            // value of true indicates that the last copy has been released.
            template <typename MultiPass>
            static bool release(MultiPass& mp)
            {
                return 0 != mp.shared && 0 == --mp.shared->count;
            }

            // returns true if there is only one iterator in existence.
            // std_deque StoragePolicy will free it's buffered data if this
            // returns true.
            template <typename MultiPass>
            static bool is_unique(MultiPass const& mp) 
            {
                return 0 == mp.shared || 1 == mp.shared->count;
            }

            template <typename MultiPass>
            static void destroy(MultiPass&) 
            {}
        };

        ////////////////////////////////////////////////////////////////////////
        struct shared
        {
            shared() : count(1) {}
            std::size_t count;
        };

    };

}}}

#endif