code: protected final ByteBuf composeIntoComposite(ByteBufAllocator alloc, ByteBuf cumulation, ByteBuf next) {
          // Create a composite buffer to accumulate this pair and potentially all the buffers
          // in the queue. Using +2 as we have already dequeued current and next.
          CompositeByteBuf composite = alloc.compositeBuffer(size() + 2);
          try {
              composite.addComponent(true, cumulation);
              composite.addComponent(true, next);
          } catch (Throwable cause) {
              composite.release();
              safeRelease(next);
              throwException(cause);
          }
          return composite;
      }
docs: Compose {@code cumulation} and {@code next} into a new {@link CompositeByteBuf}.