Method enqueue

extern/libcds/cds/intrusive/segmented_queue.h:462–515

Inserts a new element at last segment of the queue

        /// Inserts a new element at last segment of the queue
        bool enqueue( value_type& val )
        {
            // LSB is used as a flag in marked pointer
            assert( (reinterpret_cast<uintptr_t>( &val ) & 1) == 0 );

            typename gc::Guard segmentGuard;
            segment * pTailSegment = m_SegmentList.tail( segmentGuard );
            if ( !pTailSegment ) {
                // no segments, create the new one
                pTailSegment = m_SegmentList.create_tail( pTailSegment, segmentGuard );
                assert( pTailSegment );
            }

            permutation_generator gen( quasi_factor());

            // First, increment item counter.
            // We sure that the item will be enqueued
            // but if we increment the counter after inserting we can get a negative counter value
            // if dequeuing occurs before incrementing (enqueue/dequeue race)
            ++m_ItemCounter;

            while ( true ) {
                CDS_DEBUG_ONLY( size_t nLoopCount = 0);
                do {
                    typename permutation_generator::integer_type i = gen;
                    CDS_DEBUG_ONLY( ++nLoopCount );
                    if ( pTailSegment->cells[i].data.load(memory_model::memory_order_relaxed).all()) {
                        // Cell is not empty, go next
                        m_Stat.onPushPopulated();
                    }
                    else {
                        // Empty cell found, try to enqueue here
                        regular_cell nullCell;
                        if ( pTailSegment->cells[i].data.compare_exchange_strong( nullCell, regular_cell( &val ),
                            memory_model::memory_order_release, atomics::memory_order_relaxed ))
                        {
                            // Ok to push item
                            m_Stat.onPush();
                            return true;
                        }
                        assert( nullCell.ptr());
                        m_Stat.onPushContended();
                    }
                } while ( gen.next());

                assert( nLoopCount == quasi_factor());

                // No available position, create a new segment
                pTailSegment = m_SegmentList.create_tail( pTailSegment, segmentGuard );

                // Get new permutation
                gen.reset();
            }
        }

        /// Removes an element from first segment of the queue and returns it
        /**