Function insert_block_index_entry

include/dmlc/concurrentqueue.h:2896–2925

    template<AllocationMode allocMode>
    inline bool insert_block_index_entry(BlockIndexEntry *&idxEntry, index_t blockStartIndex) {
      auto localBlockIndex = blockIndex.load(
        std::memory_order_relaxed);    // We're the only writer thread, relaxed is OK
      if (localBlockIndex == nullptr) {
        return false;  // this can happen if new_block_index failed in the constructor
      }
      auto newTail = (localBlockIndex->tail.load(std::memory_order_relaxed) + 1) &
                     (localBlockIndex->capacity - 1);
      idxEntry = localBlockIndex->index[newTail];
      if (idxEntry->key.load(std::memory_order_relaxed) == INVALID_BLOCK_BASE ||
          idxEntry->value.load(std::memory_order_relaxed) == nullptr) {

        idxEntry->key.store(blockStartIndex, std::memory_order_relaxed);
        localBlockIndex->tail.store(newTail, std::memory_order_release);
        return true;
      }

      // No room in the old block index, try to allocate another one!
      if (allocMode == CannotAlloc || !new_block_index()) {
        return false;
      }
      localBlockIndex = blockIndex.load(std::memory_order_relaxed);
      newTail = (localBlockIndex->tail.load(std::memory_order_relaxed) + 1) &
                (localBlockIndex->capacity - 1);
      idxEntry = localBlockIndex->index[newTail];
      assert(idxEntry->key.load(std::memory_order_relaxed) == INVALID_BLOCK_BASE);
      idxEntry->key.store(blockStartIndex, std::memory_order_relaxed);
      localBlockIndex->tail.store(newTail, std::memory_order_release);
      return true;
    }

    inline void rewind_block_index_tail() {
      auto localBlockIndex = blockIndex.load(std::memory_order_relaxed);