org.apache.hadoop.hdfs.server.namenode.FSImageUtil.java Source code

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Here is the source code for org.apache.hadoop.hdfs.server.namenode.FSImageUtil.java

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/**
 * 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.namenode;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.util.Arrays;

import org.apache.commons.io.Charsets;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.protocol.LayoutVersion.Feature;
import org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf.Loader;
import org.apache.hadoop.hdfs.server.namenode.FsImageProto.FileSummary;
import org.apache.hadoop.io.compress.CompressionCodec;

@InterfaceAudience.Private
public final class FSImageUtil {
    public static final byte[] MAGIC_HEADER = "HDFSIMG1".getBytes(Charsets.UTF_8);
    public static final int FILE_VERSION = 1;

    public static boolean checkFileFormat(RandomAccessFile file) throws IOException {
        if (file.length() < Loader.MINIMUM_FILE_LENGTH)
            return false;

        byte[] magic = new byte[MAGIC_HEADER.length];
        file.readFully(magic);
        if (!Arrays.equals(MAGIC_HEADER, magic))
            return false;

        return true;
    }

    public static FileSummary loadSummary(RandomAccessFile file) throws IOException {
        final int FILE_LENGTH_FIELD_SIZE = 4;
        long fileLength = file.length();
        file.seek(fileLength - FILE_LENGTH_FIELD_SIZE);
        int summaryLength = file.readInt();

        if (summaryLength <= 0) {
            throw new IOException("Negative length of the file");
        }
        file.seek(fileLength - FILE_LENGTH_FIELD_SIZE - summaryLength);

        byte[] summaryBytes = new byte[summaryLength];
        file.readFully(summaryBytes);

        FileSummary summary = FileSummary.parseDelimitedFrom(new ByteArrayInputStream(summaryBytes));
        if (summary.getOndiskVersion() != FILE_VERSION) {
            throw new IOException("Unsupported file version " + summary.getOndiskVersion());
        }

        if (!NameNodeLayoutVersion.supports(Feature.PROTOBUF_FORMAT, summary.getLayoutVersion())) {
            throw new IOException("Unsupported layout version " + summary.getLayoutVersion());
        }
        return summary;
    }

    public static InputStream wrapInputStreamForCompression(Configuration conf, String codec, InputStream in)
            throws IOException {
        if (codec.isEmpty())
            return in;

        FSImageCompression compression = FSImageCompression.createCompression(conf, codec);
        CompressionCodec imageCodec = compression.getImageCodec();
        return imageCodec.createInputStream(in);
    }

}