/*
    This file is a part of libcds - Concurrent Data Structures library

    (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017

    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_DETAILS_GPI_H
#define CDSLIB_URCU_DETAILS_GPI_H

#include <mutex>
#include <cds/urcu/details/gp.h>
#include <cds/algo/backoff_strategy.h>

namespace cds { namespace urcu {

    /// User-space general-purpose RCU with immediate reclamation
    /**
        @headerfile cds/urcu/general_instant.h

        This is simplest general-purpose RCU implementation. When a thread calls \ref retire_ptr function
        the RCU \p synchronize function is called that waits until all reader/updater threads end up
        their read-side critical sections, i.e. until the RCU quiescent state will come.
        After that the retired object is freed immediately.
        Thus, the implementation blocks for any retired object

        There is a wrapper \ref cds_urcu_general_instant_gc "gc<general_instant>" for \p %general_instant class
        that provides unified RCU interface. You should use this wrapper class instead \p %general_instant

        Template arguments:
        - \p Lock - mutex type, default is \p std::mutex
        - \p Backoff - back-off schema, default is cds::backoff::Default
    */
    template <
        class Lock = std::mutex
       ,class Backoff = cds::backoff::Default
    >
    class general_instant: public details::gp_singleton< general_instant_tag >
    {
        //@cond
        typedef details::gp_singleton< general_instant_tag > base_class;
        //@endcond

    public:
        typedef general_instant_tag rcu_tag ;   ///< RCU tag
        typedef Lock    lock_type   ;           ///< Lock type
        typedef Backoff back_off    ;           ///< Back-off schema type

        typedef typename base_class::thread_gc  thread_gc ;   ///< Thread-side RCU part
        typedef typename thread_gc::scoped_lock scoped_lock ; ///< Access lock class

        //@cond
        static bool const c_bBuffered = false ; ///< No buffers
        //@endcond

    protected:
        //@cond
        typedef details::gp_singleton_instance< rcu_tag >    singleton_ptr;
        //@endcond

    protected:
        //@cond
        lock_type   m_Lock;
        //@endcond

    public:
        /// Returns singleton instance
        static general_instant * instance()
        {
            return static_cast<general_instant *>( base_class::instance());
        }

        /// Checks if the singleton is created and ready to use
        static bool isUsed()
        {
            return singleton_ptr::s_pRCU != nullptr;
        }

    protected:
        //@cond
        general_instant()
        {}

        ~general_instant()
        {}

        void flip_and_wait()
        {
            back_off bkoff;
            base_class::flip_and_wait( bkoff );
        }
        //@endcond

    public:
        /// Creates singleton object
        static void Construct()
        {
            if ( !singleton_ptr::s_pRCU )
                singleton_ptr::s_pRCU = new general_instant();
        }

        /// Destroys singleton object
        static void Destruct( bool bDetachAll = false )
        {
            if ( isUsed()) {
                if ( bDetachAll )
                    instance()->m_ThreadList.detach_all();
                delete instance();
                singleton_ptr::s_pRCU = nullptr;
            }
        }

    public:
        /// Retires \p p pointer
        /**
            The method calls \p synchronize() to wait for the end of grace period
            and calls \p p disposer.
        */
        virtual void retire_ptr( retired_ptr& p ) override
        {
            synchronize();
            if ( p.m_p )
                p.free();
        }

        /// Retires the pointer chain [\p itFirst, \p itLast)
        template <typename ForwardIterator>
        void batch_retire( ForwardIterator itFirst, ForwardIterator itLast )
        {
            if ( itFirst != itLast ) {
                synchronize();
                while ( itFirst != itLast ) {
                    retired_ptr p( *itFirst );
                    ++itFirst;
                    if ( p.m_p )
                        p.free();
                }
            }
        }

        /// Retires the pointer chain until \p Func returns \p nullptr retired pointer
        template <typename Func>
        void batch_retire( Func e )
        {
            retired_ptr p{ e() };
            if ( p.m_p ) {
                synchronize();
                while ( p.m_p ) {
                    retired_ptr pr( p );
                    p = e();
                    pr.free();
                }
            }
        }

        /// Waits to finish a grace period
        void synchronize()
        {
            assert( !thread_gc::is_locked());
            std::unique_lock<lock_type> sl( m_Lock );
            flip_and_wait();
            flip_and_wait();
        }

        //@cond
        // Added for uniformity
        size_t CDS_CONSTEXPR capacity() const
        {
            return 1;
        }
        //@endcond
    };

    /// User-space general-purpose RCU with immediate reclamation (stripped version)
    /**
        @headerfile cds/urcu/general_instant.h

        This short version of \p general_instant is intended for stripping debug info.
        If you use \p %general_instant with default template arguments you may use
        this stripped version. All functionality of both classes are identical.
    */
    class general_instant_stripped: public general_instant<>
    {};

}} // namespace cds::urcu

#endif // #ifndef CDSLIB_URCU_DETAILS_GPI_H
