Function dequeue_bulk

deps/concurrentqueue/concurrentqueue.h:2233–2323

		
		template<typename It>
		size_t dequeue_bulk(It& itemFirst, size_t max)
		{
			auto tail = this->tailIndex.load(std::memory_order_relaxed);
			auto overcommit = this->dequeueOvercommit.load(std::memory_order_relaxed);
			auto desiredCount = static_cast<size_t>(tail - (this->dequeueOptimisticCount.load(std::memory_order_relaxed) - overcommit));
			if (details::circular_less_than<size_t>(0, desiredCount)) {
				desiredCount = desiredCount < max ? desiredCount : max;
				std::atomic_thread_fence(std::memory_order_acquire);
				
				auto myDequeueCount = this->dequeueOptimisticCount.fetch_add(desiredCount, std::memory_order_relaxed);
				
				tail = this->tailIndex.load(std::memory_order_acquire);
				auto actualCount = static_cast<size_t>(tail - (myDequeueCount - overcommit));
				if (details::circular_less_than<size_t>(0, actualCount)) {
					actualCount = desiredCount < actualCount ? desiredCount : actualCount;
					if (actualCount < desiredCount) {
						this->dequeueOvercommit.fetch_add(desiredCount - actualCount, std::memory_order_release);
					}
					
					// Get the first index. Note that since there's guaranteed to be at least actualCount elements, this
					// will never exceed tail.
					auto firstIndex = this->headIndex.fetch_add(actualCount, std::memory_order_acq_rel);
					
					// Determine which block the first element is in
					auto localBlockIndex = blockIndex.load(std::memory_order_acquire);
					auto localBlockIndexHead = localBlockIndex->front.load(std::memory_order_acquire);
					
					auto headBase = localBlockIndex->entries[localBlockIndexHead].base;
					auto firstBlockBaseIndex = firstIndex & ~static_cast<index_t>(BLOCK_SIZE - 1);
					auto offset = static_cast<size_t>(static_cast<typename std::make_signed<index_t>::type>(firstBlockBaseIndex - headBase) / BLOCK_SIZE);
					auto indexIndex = (localBlockIndexHead + offset) & (localBlockIndex->size - 1);
					
					// Iterate the blocks and dequeue
					auto index = firstIndex;
					do {
						auto firstIndexInBlock = index;
						index_t endIndex = (index & ~static_cast<index_t>(BLOCK_SIZE - 1)) + static_cast<index_t>(BLOCK_SIZE);
						endIndex = details::circular_less_than<index_t>(firstIndex + static_cast<index_t>(actualCount), endIndex) ? firstIndex + static_cast<index_t>(actualCount) : endIndex;
						auto block = localBlockIndex->entries[indexIndex].block;
						if (MOODYCAMEL_NOEXCEPT_ASSIGN(T, T&&, details::deref_noexcept(itemFirst) = std::move((*(*block)[index])))) {
							while (index != endIndex) {
								auto& el = *((*block)[index]);
								*itemFirst++ = std::move(el);
								el.~T();
								++index;
							}
						}
						else {
							MOODYCAMEL_TRY {
								while (index != endIndex) {
									auto& el = *((*block)[index]);
									*itemFirst = std::move(el);
									++itemFirst;
									el.~T();
									++index;
								}
							}
							MOODYCAMEL_CATCH (...) {