BufferLockFree.hpp

/***************************************************************************
  tag: Peter Soetens  Thu Jan 13 10:24:51 CET 2005  BufferLockFree.hpp

                        BufferLockFree.hpp -  description
                           -------------------
    begin                : Thu January 13 2005
    copyright            : (C) 2005 Peter Soetens
    email                : peter.soetens@mech.kuleuven.ac.be

 ***************************************************************************
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#ifndef ORO_BUFFER_LOCK_FREE_HPP
#define ORO_BUFFER_LOCK_FREE_HPP

#include "os/oro_atomic.h"
#include "os/CAS.hpp"
#include "BufferPolicy.hpp"
#include "BufferInterface.hpp"
#include "AtomicQueue.hpp"
#include "MemoryPool.hpp"
#include <vector>

#ifdef ORO_PRAGMA_INTERFACE
#pragma interface
#endif

namespace RTT
{

    using OS::CAS;

    template< class T, class ReadPolicy = NonBlockingPolicy, class WritePolicy = NonBlockingPolicy >
    class BufferLockFree
        : public BufferInterface<T>
    {
    public:
        typedef typename ReadInterface<T>::reference_t reference_t;
        typedef typename WriteInterface<T>::param_t param_t;
        typedef typename BufferInterface<T>::size_type size_type;
        typedef T value_t;
    private:
        typedef T Item;
        AtomicQueue<Item*,ReadPolicy,WritePolicy> bufs;
        // is mutable because of reference counting.
        mutable FixedSizeMemoryPool<Item> mpool;
    public:
        BufferLockFree( unsigned int bufsize, const T& initial_value = T() )
            : bufs( bufsize ), mpool(bufsize, initial_value)
        {
        }

        size_type capacity() const
        {
            return bufs.capacity();
        }

        size_type size() const
        {
            return bufs.size();
        }

        bool empty() const
        {
            return bufs.isEmpty();
        }

        bool full() const
        {
            return bufs.isFull();
        }

        void clear()
        {
            Item* item;
            while ( bufs.dequeue(item) )
                mpool.deallocate( item );
        }

        bool write( param_t d ) {
            return this->Push( d );
        }

        bool Push( param_t item)
        {
            Item* mitem = mpool.allocate();
            if ( mitem == 0 ) // queue full.
                return false;
            // copy over.
            *mitem = item;
            if (bufs.enqueue( mitem ) == false ) { // can this ever happen ?
                //mpool.deallocate( mitem );
                //return false;
                assert(false && "Race detected in Push()");
            }
            return true;
        }

        size_type write( const std::vector<T>& d) {
            return this->Push( d );
        }

        size_type Push(const std::vector<T>& items)
        {
            int towrite  = items.size();
            typename std::vector<T>::const_iterator it;
            for(  it = items.begin(); it != items.end(); ++it)
                if ( this->Push( *it ) == false )
                    break;
            return towrite - (items.end() - it);
        }


        bool read(T& res) {
            return this->Pop( res );
        }

        value_t front() const {
            Item* orig;
            orig = bufs.lockfront(mpool);
            // if orig == 0, then queue is empty
            if (orig == 0)
                return value_t();

            // ok, copy, unlock and return front.
            value_t ret = *orig;
            mpool.unlock( orig );
            return ret;
        }

        bool Pop( reference_t item )
        {
            Item* ipop;
            if (bufs.dequeue( ipop ) == false )
                return false;
            item = *ipop;
            if (mpool.deallocate( ipop ) == false )
                assert(false);
            return true;
        }

        size_type read(std::vector<T>& res)
        {
            return this->Pop( res );
        }

        size_type Pop(std::vector<T>& items )
        {
            Item* ipop;
            items.clear();
            while( bufs.dequeue(ipop) ) {
                items.push_back( *ipop );
                if (mpool.deallocate(ipop) == false)
                    assert(false);
            }
            return items.size();
        }

    };
}

#endif