Extract Variable	unbufMirrorOut : OutputStream in method public writeBlock(block ExtendedBlock, blockToken Token<BlockTokenIdentifier>, clientname String, targets DatanodeInfo[], srcDataNode DatanodeInfo, stage BlockConstructionStage, pipelineSize int, minBytesRcvd long, maxBytesRcvd long, latestGenerationStamp long, requestedChecksum DataChecksum) : void from class org.apache.hadoop.hdfs.server.datanode.DataXceiver