| /** |
| * 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; |
| |
| import java.io.BufferedInputStream; |
| import java.io.DataInputStream; |
| import java.io.DataOutputStream; |
| import java.io.File; |
| import java.io.FileInputStream; |
| import java.io.IOException; |
| |
| import org.apache.hadoop.io.IOUtils; |
| import org.apache.hadoop.util.DataChecksum; |
| |
| |
| /** |
| * BlockMetadataHeader manages metadata for data blocks on Datanodes. |
| * This is not related to the Block related functionality in Namenode. |
| * The biggest part of data block metadata is CRC for the block. |
| */ |
| class BlockMetadataHeader { |
| |
| static final short METADATA_VERSION = FSDataset.METADATA_VERSION; |
| |
| /** |
| * Header includes everything except the checksum(s) themselves. |
| * Version is two bytes. Following it is the DataChecksum |
| * that occupies 5 bytes. |
| */ |
| private short version; |
| private DataChecksum checksum = null; |
| |
| BlockMetadataHeader(short version, DataChecksum checksum) { |
| this.checksum = checksum; |
| this.version = version; |
| } |
| |
| short getVersion() { |
| return version; |
| } |
| |
| DataChecksum getChecksum() { |
| return checksum; |
| } |
| |
| |
| /** |
| * This reads all the fields till the beginning of checksum. |
| * @param in |
| * @return Metadata Header |
| * @throws IOException |
| */ |
| static BlockMetadataHeader readHeader(DataInputStream in) throws IOException { |
| return readHeader(in.readShort(), in); |
| } |
| |
| /** |
| * Reads header at the top of metadata file and returns the header. |
| * |
| * @param dataset |
| * @param block |
| * @return |
| * @throws IOException |
| */ |
| static BlockMetadataHeader readHeader(File file) throws IOException { |
| DataInputStream in = null; |
| try { |
| in = new DataInputStream(new BufferedInputStream( |
| new FileInputStream(file))); |
| return readHeader(in); |
| } finally { |
| IOUtils.closeStream(in); |
| } |
| } |
| |
| // Version is already read. |
| private static BlockMetadataHeader readHeader(short version, DataInputStream in) |
| throws IOException { |
| DataChecksum checksum = DataChecksum.newDataChecksum(in); |
| return new BlockMetadataHeader(version, checksum); |
| } |
| |
| /** |
| * This writes all the fields till the beginning of checksum. |
| * @param out DataOutputStream |
| * @param header |
| * @return |
| * @throws IOException |
| */ |
| private static void writeHeader(DataOutputStream out, |
| BlockMetadataHeader header) |
| throws IOException { |
| out.writeShort(header.getVersion()); |
| header.getChecksum().writeHeader(out); |
| } |
| |
| /** |
| * Writes all the fields till the beginning of checksum. |
| * @param out |
| * @param checksum |
| * @throws IOException |
| */ |
| static void writeHeader(DataOutputStream out, DataChecksum checksum) |
| throws IOException { |
| writeHeader(out, new BlockMetadataHeader(METADATA_VERSION, checksum)); |
| } |
| |
| /** |
| * Returns the size of the header |
| */ |
| static int getHeaderSize() { |
| return Short.SIZE/Byte.SIZE + DataChecksum.getChecksumHeaderSize(); |
| } |
| } |
| |