Method enqueue

source/util/concurrentqueue.h:2487–2541

		
		template<AllocationMode allocMode, typename U>
		inline bool enqueue(U&& element)
		{
			index_t currentTailIndex = this->tailIndex.load(std::memory_order_relaxed);
			index_t newTailIndex = 1 + currentTailIndex;
			if ((currentTailIndex & static_cast<index_t>(BLOCK_SIZE - 1)) == 0) {
				// We reached the end of a block, start a new one
				auto head = this->headIndex.load(std::memory_order_relaxed);
				assert(!details::circular_less_than<index_t>(currentTailIndex, head));
				if (!details::circular_less_than<index_t>(head, currentTailIndex + BLOCK_SIZE) || (MAX_SUBQUEUE_SIZE != details::const_numeric_max<size_t>::value && (MAX_SUBQUEUE_SIZE == 0 || MAX_SUBQUEUE_SIZE - BLOCK_SIZE < currentTailIndex - head))) {
					return false;
				}
#ifdef MCDBGQ_NOLOCKFREE_IMPLICITPRODBLOCKINDEX
				debug::DebugLock lock(mutex);
#endif
				// Find out where we'll be inserting this block in the block index
				BlockIndexEntry* idxEntry;
				if (!insert_block_index_entry<allocMode>(idxEntry, currentTailIndex)) {
					return false;
				}
				
				// Get ahold of a new block
				auto newBlock = this->parent->ConcurrentQueue::template requisition_block<allocMode>();
				if (newBlock == nullptr) {
					rewind_block_index_tail();
					idxEntry->value.store(nullptr, std::memory_order_relaxed);
					return false;
				}
#ifdef MCDBGQ_TRACKMEM
				newBlock->owner = this;
#endif
				newBlock->ConcurrentQueue::Block::template reset_empty<implicit_context>();

				MOODYCAMEL_CONSTEXPR_IF (!MOODYCAMEL_NOEXCEPT_CTOR(T, U, new (static_cast<T*>(nullptr)) T(std::forward<U>(element)))) {
					// May throw, try to insert now before we publish the fact that we have this new block
					MOODYCAMEL_TRY {
						new ((*newBlock)[currentTailIndex]) T(std::forward<U>(element));
					}
					MOODYCAMEL_CATCH (...) {
						rewind_block_index_tail();
						idxEntry->value.store(nullptr, std::memory_order_relaxed);
						this->parent->add_block_to_free_list(newBlock);
						MOODYCAMEL_RETHROW;
					}
				}
				
				// Insert the new block into the index
				idxEntry->value.store(newBlock, std::memory_order_relaxed);
				
				this->tailBlock = newBlock;
				
				MOODYCAMEL_CONSTEXPR_IF (!MOODYCAMEL_NOEXCEPT_CTOR(T, U, new (static_cast<T*>(nullptr)) T(std::forward<U>(element)))) {
					this->tailIndex.store(newTailIndex, std::memory_order_release);
					return true;
				}
			}
			
			// Enqueue
			new ((*this->tailBlock)[currentTailIndex]) T(std::forward<U>(element));