firebird/extern/libcds/cds/container/msqueue.h

// Copyright (c) 2006-2018 Maxim Khizhinsky
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef CDSLIB_CONTAINER_MSQUEUE_H
#define CDSLIB_CONTAINER_MSQUEUE_H

#include <memory>
#include <cds/intrusive/msqueue.h>
#include <cds/container/details/base.h>

namespace cds { namespace container {

    /// MSQueue related definitions
    /** @ingroup cds_nonintrusive_helper
    */
    namespace msqueue {
        /// Internal statistics
        template <typename Counter = cds::intrusive::msqueue::stat<>::counter_type >
        using stat = cds::intrusive::msqueue::stat< Counter >;

        /// Dummy internal statistics
        typedef cds::intrusive::msqueue::empty_stat empty_stat;

        /// MSQueue default type traits
        struct traits
        {
            /// Node allocator
            typedef CDS_DEFAULT_ALLOCATOR       allocator;

            /// Back-off strategy
            typedef cds::backoff::empty         back_off;

            /// Item counting feature; by default, disabled. Use \p cds::atomicity::item_counter to enable item counting
            typedef atomicity::empty_item_counter   item_counter;

            /// Internal statistics (by default, disabled)
            /**
                Possible option value are: \p msqueue::stat, \p msqueue::empty_stat (the default),
                user-provided class that supports \p %msqueue::stat interface.
            */
            typedef msqueue::empty_stat         stat;

            /// C++ memory ordering model
            /**
                Can be \p opt::v::relaxed_ordering (relaxed memory model, the default)
                or \p opt::v::sequential_consistent (sequentially consisnent memory model).
            */
            typedef opt::v::relaxed_ordering    memory_model;

            /// Padding for internal critical atomic data. Default is \p opt::cache_line_padding
            enum { padding = opt::cache_line_padding };
        };

        /// Metafunction converting option list to \p msqueue::traits
        /**
            Supported \p Options are:
            - \p opt::allocator - allocator (like \p std::allocator) used for allocating queue nodes. Default is \ref CDS_DEFAULT_ALLOCATOR
            - \p opt::back_off - back-off strategy used, default is \p cds::backoff::empty.
            - \p opt::item_counter - the type of item counting feature. Default is \p cds::atomicity::empty_item_counter (item counting disabled)
                To enable item counting use \p cds::atomicity::item_counter
            - \p opt::stat - the type to gather internal statistics.
                Possible statistics types are: \p msqueue::stat, \p msqueue::empty_stat, user-provided class that supports \p %msqueue::stat interface.
                Default is \p %msqueue::empty_stat.
            - \p opt::padding - padding for internal critical atomic data. Default is \p opt::cache_line_padding
            - \p opt::memory_model - C++ memory ordering model. Can be \p opt::v::relaxed_ordering (relaxed memory model, the default)
                or \p opt::v::sequential_consistent (sequentially consisnent memory model).

            Example: declare \p %MSQueue with item counting and internal statistics
            \code
            typedef cds::container::MSQueue< cds::gc::HP, Foo,
                typename cds::container::msqueue::make_traits<
                    cds::opt::item_counter< cds::atomicity::item_counter >,
                    cds::opt::stat< cds::container::msqueue::stat<> >
                >::type
            > myQueue;
            \endcode
        */
        template <typename... Options>
        struct make_traits {
#   ifdef CDS_DOXYGEN_INVOKED
            typedef implementation_defined type;   ///< Metafunction result
#   else
            typedef typename cds::opt::make_options<
                typename cds::opt::find_type_traits< traits, Options... >::type
                , Options...
            >::type type;
#   endif
        };
    } // namespace msqueue

    //@cond
    namespace details {
        template <typename GC, typename T, typename Traits>
        struct make_msqueue
        {
            typedef GC gc;
            typedef T value_type;
            typedef Traits traits;

            struct node_type : public intrusive::msqueue::node< gc >
            {
                value_type  m_value;

                node_type( value_type const& val )
                    : m_value( val )
                {}

                template <typename... Args>
                node_type( Args&&... args )
                    : m_value( std::forward<Args>( args )... )
                {}
            };

            typedef typename std::allocator_traits< 
                typename traits::allocator
            >::template rebind_alloc<node_type> allocator_type;
            typedef cds::details::Allocator< node_type, allocator_type >           cxx_allocator;

            struct node_deallocator
            {
                void operator ()( node_type * pNode )
                {
                    cxx_allocator().Delete( pNode );
                }
            };

            struct intrusive_traits : public traits
            {
                typedef cds::intrusive::msqueue::base_hook< cds::opt::gc<gc> > hook;
                typedef node_deallocator disposer;
                static constexpr const cds::intrusive::opt::link_check_type link_checker = cds::intrusive::msqueue::traits::link_checker;
            };

            typedef intrusive::MSQueue< gc, node_type, intrusive_traits > type;
        };
    }
    //@endcond

    /// Michael & Scott lock-free queue
    /** @ingroup cds_nonintrusive_queue
        It is non-intrusive version of Michael & Scott's queue algorithm based on intrusive implementation
        \p cds::intrusive::MSQueue.

        Template arguments:
        - \p GC - garbage collector type: \p gc::HP, \p gc::DHP
        - \p T is a type stored in the queue.
        - \p Traits - queue traits, default is \p msqueue::traits. You can use \p msqueue::make_traits
            metafunction to make your traits or just derive your traits from \p %msqueue::traits:
            \code
            struct myTraits: public cds::container::msqueue::traits {
                typedef cds::intrusive::msqueue::stat<> stat;
                typedef cds::atomicity::item_counter    item_counter;
            };
            typedef cds::container::MSQueue< cds::gc::HP, Foo, myTraits > myQueue;

            // Equivalent make_traits example:
            typedef cds::container::MSQueue< cds::gc::HP, Foo,
                typename cds::container::msqueue::make_traits<
                    cds::opt::stat< cds::container::msqueue::stat<> >,
                    cds::opt::item_counter< cds::atomicity::item_counter >
                >::type
            > myQueue;
            \endcode
    */
    template <typename GC, typename T, typename Traits = cds::container::msqueue::traits>
    class MSQueue:
#ifdef CDS_DOXYGEN_INVOKED
        private intrusive::MSQueue< GC, cds::intrusive::msqueue::node< T >, Traits >
#else
        private details::make_msqueue< GC, T, Traits >::type
#endif
    {
        //@cond
        typedef details::make_msqueue< GC, T, Traits > maker;
        typedef typename maker::type base_class;
        //@endcond

    public:
        /// Rebind template arguments
        template <typename GC2, typename T2, typename Traits2>
        struct rebind {
            typedef MSQueue< GC2, T2, Traits2> other   ;   ///< Rebinding result
        };

    public:
        typedef T value_type;   ///< Value type stored in the queue
        typedef Traits traits;  ///< Queue traits

        typedef typename base_class::gc             gc;             ///< Garbage collector used
        typedef typename base_class::back_off       back_off;       ///< Back-off strategy used
        typedef typename maker::allocator_type      allocator_type; ///< Allocator type used for allocate/deallocate the nodes
        typedef typename base_class::item_counter   item_counter;   ///< Item counting policy used
        typedef typename base_class::stat           stat;           ///< Internal statistics policy used
        typedef typename base_class::memory_model   memory_model;   ///< Memory ordering. See cds::opt::memory_model option

        static constexpr const size_t c_nHazardPtrCount = base_class::c_nHazardPtrCount; ///< Count of hazard pointer required for the algorithm

    protected:
        //@cond
        typedef typename maker::node_type  node_type;   ///< queue node type (derived from \p intrusive::msqueue::node)

        typedef typename maker::cxx_allocator     cxx_allocator;
        typedef typename maker::node_deallocator  node_deallocator;   // deallocate node
        typedef typename base_class::node_traits  node_traits;
        //@endcond

    protected:
        ///@cond
        static node_type * alloc_node()
        {
            return cxx_allocator().New();
        }
        static node_type * alloc_node( value_type const& val )
        {
            return cxx_allocator().New( val );
        }
        template <typename... Args>
        static node_type * alloc_node_move( Args&&... args )
        {
            return cxx_allocator().MoveNew( std::forward<Args>( args )... );
        }
        static void free_node( node_type * p )
        {
            node_deallocator()( p );
        }

        struct node_disposer {
            void operator()( node_type * pNode )
            {
                free_node( pNode );
            }
        };
        typedef std::unique_ptr< node_type, node_disposer >     scoped_node_ptr;
        //@endcond

    public:
        /// Initializes empty queue
        MSQueue()
        {}

        /// Destructor clears the queue
        ~MSQueue()
        {}

        /// Enqueues \p val value into the queue.
        /**
            The function makes queue node in dynamic memory calling copy constructor for \p val
            and then it calls \p intrusive::MSQueue::enqueue.
            Returns \p true if success, \p false otherwise.
        */
        bool enqueue( value_type const& val )
        {
            scoped_node_ptr p( alloc_node(val));
            if ( base_class::enqueue( *p )) {
                p.release();
                return true;
            }
            return false;
        }

        /// Enqueues \p val in the queue, move semantics
        bool enqueue( value_type&& val )
        {
            scoped_node_ptr p( alloc_node_move( std::move( val )));
            if ( base_class::enqueue( *p )) {
                p.release();
                return true;
            }
            return false;
        }

        /// Enqueues data to the queue using a functor
        /**
            \p Func is a functor called to create node.
            The functor \p f takes one argument - a reference to a new node of type \ref value_type :
            \code
            cds::container::MSQueue< cds::gc::HP, Foo > myQueue;
            Bar bar;
            myQueue.enqueue_with( [&bar]( Foo& dest ) { dest = bar; } );
            \endcode
        */
        template <typename Func>
        bool enqueue_with( Func f )
        {
            scoped_node_ptr p( alloc_node());
            f( p->m_value );
            if ( base_class::enqueue( *p )) {
                p.release();
                return true;
            }
            return false;
        }

        /// Enqueues data of type \ref value_type constructed from <tt>std::forward<Args>(args)...</tt>
        template <typename... Args>
        bool emplace( Args&&... args )
        {
            scoped_node_ptr p( alloc_node_move( std::forward<Args>( args )... ));
            if ( base_class::enqueue( *p )) {
                p.release();
                return true;
            }
            return false;
        }

        /// Synonym for \p enqueue() function
        bool push( value_type const& val )
        {
            return enqueue( val );
        }

        /// Synonym for \p enqueue() function
        bool push( value_type&& val )
        {
            return enqueue( std::move( val ));
        }

        /// Synonym for \p enqueue_with() function
        template <typename Func>
        bool push_with( Func f )
        {
            return enqueue_with( f );
        }

        /// Dequeues a value from the queue
        /**
            If queue is not empty, the function returns \p true, \p dest contains copy of
            dequeued value. The assignment operator for type \ref value_type is invoked.
            If queue is empty, the function returns \p false, \p dest is unchanged.
        */
        bool dequeue( value_type& dest )
        {
            return dequeue_with( [&dest]( value_type& src ) {
                // TSan finds a race between this read of \p src and node_type constructor
                // I think, it is wrong
                CDS_TSAN_ANNOTATE_IGNORE_READS_BEGIN;
                dest = std::move( src );
                CDS_TSAN_ANNOTATE_IGNORE_READS_END;
            });
        }

        /// Dequeues a value using a functor
        /**
            \p Func is a functor called to copy dequeued value.
            The functor takes one argument - a reference to removed node:
            \code
            cds:container::MSQueue< cds::gc::HP, Foo > myQueue;
            Bar bar;
            myQueue.dequeue_with( [&bar]( Foo& src ) { bar = std::move( src );});
            \endcode
            The functor is called only if the queue is not empty.
        */
        template <typename Func>
        bool dequeue_with( Func f )
        {
            typename base_class::dequeue_result res;
            if ( base_class::do_dequeue( res )) {
                f( node_traits::to_value_ptr( *res.pNext )->m_value );
                base_class::dispose_result( res );
                return true;
            }
            return false;
        }

        /// Synonym for \p dequeue() function
        bool pop( value_type& dest )
        {
            return dequeue( dest );
        }

        /// Synonym for \p dequeue_with() function
        template <typename Func>
        bool pop_with( Func f )
        {
            return dequeue_with( f );
        }

        /// Clear the queue
        /**
            The function repeatedly calls \ref dequeue until it returns \p nullptr.
        */
        void clear()
        {
            base_class::clear();
        }

        /// Checks if the queue is empty
        bool empty() const
        {
            return base_class::empty();
        }

        /// Returns queue's item count (see \ref intrusive::MSQueue::size for explanation)
        /** \copydetails cds::intrusive::MSQueue::size()
        */
        size_t size() const
        {
            return base_class::size();
        }

        /// Returns reference to internal statistics
        const stat& statistics() const
        {
            return base_class::statistics();
        }
    };

}}  // namespace cds::container

#endif  // #ifndef CDSLIB_CONTAINER_MSQUEUE_H