def checkPieceHash(pieceIndex)
      id = returnAndIncrRequestId
      return id if @state == :after_stop
      @requests.push [id, :hash_piece, pieceIndex]
      @requestsSemaphore.signal
      id
    end
def checkPieceHash(pieceIndex)
      id = returnAndIncrRequestId
      return id if @state == :after_stop
      @requests.push [id, :hash_piece, pieceIndex]
      @requestsSemaphore.signal
      id
    end
Validate that the hash of the downloaded piece matches the hash from the metainfo.
 The result is successful? if the hash matches, false otherwise. The data of the result is
 set to the piece index.