Method enqueue

include/dmlc/concurrentqueue.h:2461–2517

    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;
        }
#if 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;
        }
#if MCDBGQ_TRACKMEM
        newBlock->owner = this;
#endif
        newBlock->template reset_empty<implicit_context>();

        if (!MOODYCAMEL_NOEXCEPT_CTOR(T, U, new(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;

        if (!MOODYCAMEL_NOEXCEPT_CTOR(T, U, new(nullptr) T(std::forward<U>(element)))) {
          this->tailIndex.store(newTailIndex, std::memory_order_release);
          return true;
        }
      }