Function new_block_index

concurrentqueue.h:2378–2415

		
		
		bool new_block_index(size_t numberOfFilledSlotsToExpose)
		{
			auto prevBlockSizeMask = pr_blockIndexSize - 1;
			
			// Create the new block
			pr_blockIndexSize <<= 1;
			auto newRawPtr = static_cast<char*>((Traits::malloc)(sizeof(BlockIndexHeader) + std::alignment_of<BlockIndexEntry>::value - 1 + sizeof(BlockIndexEntry) * pr_blockIndexSize));
			if (newRawPtr == nullptr) {
				pr_blockIndexSize >>= 1;		// Reset to allow graceful retry
				return false;
			}
			
			auto newBlockIndexEntries = reinterpret_cast<BlockIndexEntry*>(details::align_for<BlockIndexEntry>(newRawPtr + sizeof(BlockIndexHeader)));
			
			// Copy in all the old indices, if any
			size_t j = 0;
			if (pr_blockIndexSlotsUsed != 0) {
				auto i = (pr_blockIndexFront - pr_blockIndexSlotsUsed) & prevBlockSizeMask;
				do {
					newBlockIndexEntries[j++] = pr_blockIndexEntries[i];
					i = (i + 1) & prevBlockSizeMask;
				} while (i != pr_blockIndexFront);
			}
			
			// Update everything
			auto header = new (newRawPtr) BlockIndexHeader;
			header->size = pr_blockIndexSize;
			header->front.store(numberOfFilledSlotsToExpose - 1, std::memory_order_relaxed);
			header->entries = newBlockIndexEntries;
			header->prev = pr_blockIndexRaw;		// we link the new block to the old one so we can free it later
			
			pr_blockIndexFront = j;
			pr_blockIndexEntries = newBlockIndexEntries;
			pr_blockIndexRaw = newRawPtr;
			blockIndex.store(header, std::memory_order_release);
			
			return true;
		}
		
	private:
		std::atomic<BlockIndexHeader*> blockIndex;