Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl; import java.io.ByteArrayOutputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileDescriptor; import java.io.FileInputStream; import java.io.FilenameFilter; import java.io.IOException; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.URI; import java.util.Arrays; import com.google.common.base.Preconditions; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hdfs.protocol.Block; import org.apache.hadoop.hdfs.protocol.HdfsConstants; import org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader; import org.apache.hadoop.hdfs.server.datanode.DatanodeUtil; import org.apache.hadoop.hdfs.server.datanode.FinalizedReplica; import org.apache.hadoop.hdfs.server.datanode.ReplicaInfo; import org.apache.hadoop.io.IOUtils; import org.apache.hadoop.util.DataChecksum; /** Utility methods. */ @InterfaceAudience.Private public class FsDatasetUtil { static boolean isUnlinkTmpFile(File f) { return f.getName().endsWith(DatanodeUtil.UNLINK_BLOCK_SUFFIX); } public static byte[] createNullChecksumByteArray() { DataChecksum csum = DataChecksum.newDataChecksum(DataChecksum.Type.NULL, 512); ByteArrayOutputStream out = new ByteArrayOutputStream(); DataOutputStream dataOut = new DataOutputStream(out); try { BlockMetadataHeader.writeHeader(dataOut, csum); dataOut.close(); } catch (IOException e) { FsVolumeImpl.LOG.error("Exception in creating null checksum stream: " + e); return null; } return out.toByteArray(); } static File getOrigFile(File unlinkTmpFile) { final String name = unlinkTmpFile.getName(); if (!name.endsWith(DatanodeUtil.UNLINK_BLOCK_SUFFIX)) { throw new IllegalArgumentException( "unlinkTmpFile=" + unlinkTmpFile + " does not end with " + DatanodeUtil.UNLINK_BLOCK_SUFFIX); } final int n = name.length() - DatanodeUtil.UNLINK_BLOCK_SUFFIX.length(); return new File(unlinkTmpFile.getParentFile(), name.substring(0, n)); } static File getMetaFile(File f, long gs) { return new File(f.getParent(), DatanodeUtil.getMetaName(f.getName(), gs)); } /** Find the corresponding meta data file from a given block file */ public static File findMetaFile(final File blockFile) throws IOException { final String prefix = blockFile.getName() + "_"; final File parent = blockFile.getParentFile(); final File[] matches = parent.listFiles(new FilenameFilter() { @Override public boolean accept(File dir, String name) { return dir.equals(parent) && name.startsWith(prefix) && name.endsWith(Block.METADATA_EXTENSION); } }); if (matches == null || matches.length == 0) { throw new IOException("Meta file not found, blockFile=" + blockFile); } if (matches.length > 1) { throw new IOException("Found more than one meta files: " + Arrays.asList(matches)); } return matches[0]; } public static FileDescriptor openAndSeek(File file, long offset) throws IOException { RandomAccessFile raf = null; try { raf = new RandomAccessFile(file, "r"); if (offset > 0) { raf.seek(offset); } return raf.getFD(); } catch (IOException ioe) { IOUtils.cleanup(null, raf); throw ioe; } } /** * Find the meta-file for the specified block file and then return the * generation stamp from the name of the meta-file. Generally meta file will * be the next file in sorted array of file's. * * @param listdir * sorted list of file based on name. * @param blockFile * block file for which generation stamp is needed. * @param index * index of block file in array. * @return generation stamp for block file. */ static long getGenerationStampFromFile(File[] listdir, File blockFile, int index) { String blockName = blockFile.getName(); if ((index + 1) < listdir.length) { // Check if next index file is meta file String metaFile = listdir[index + 1].getName(); if (metaFile.startsWith(blockName)) { return Block.getGenerationStamp(metaFile); } } FsDatasetImpl.LOG.warn("Block " + blockFile + " does not have a metafile!"); return HdfsConstants.GRANDFATHER_GENERATION_STAMP; } /** Find the corresponding meta data file from a given block file */ static long parseGenerationStamp(File blockFile, File metaFile) throws IOException { final String metaname = metaFile.getName(); final String gs = metaname.substring(blockFile.getName().length() + 1, metaname.length() - Block.METADATA_EXTENSION.length()); try { return Long.parseLong(gs); } catch (NumberFormatException nfe) { throw new IOException( "Failed to parse generation stamp: blockFile=" + blockFile + ", metaFile=" + metaFile, nfe); } } /** * Compute the checksum for a block file that does not already have * its checksum computed, and save it to dstMeta file. */ public static void computeChecksum(File srcMeta, File dstMeta, File blockFile, int smallBufferSize, Configuration conf) throws IOException { Preconditions.checkNotNull(srcMeta); Preconditions.checkNotNull(dstMeta); Preconditions.checkNotNull(blockFile); // Create a dummy ReplicaInfo object pointing to the blockFile. ReplicaInfo wrapper = new FinalizedReplica(0, 0, 0, null, null) { @Override public URI getMetadataURI() { return srcMeta.toURI(); } @Override public InputStream getDataInputStream(long seekOffset) throws IOException { return new FileInputStream(blockFile); } }; FsDatasetImpl.computeChecksum(wrapper, dstMeta, smallBufferSize, conf); } }