com.dianping.cat.hadoop.hdfs.MessageBlockReader.java Source code

Introduction

Here is the source code for com.dianping.cat.hadoop.hdfs.MessageBlockReader.java

Source

/*
 * Copyright (c) 2011-2018, Meituan Dianping. All Rights Reserved.
 *
 * 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 com.dianping.cat.hadoop.hdfs;

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.util.zip.GZIPInputStream;

import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.xerial.snappy.SnappyInputStream;

import com.dianping.cat.Cat;

public class MessageBlockReader {
    private FSDataInputStream m_indexFile;

    private FSDataInputStream m_dataFile;

    public MessageBlockReader(FileSystem fs, Path basePath, String dataFile) throws IOException {
        m_indexFile = fs.open(new Path(basePath, dataFile + ".idx"));
        m_dataFile = fs.open(new Path(basePath, dataFile));
    }

    public MessageBlockReader(FileSystem fs, String dataFile) throws IOException {
        m_indexFile = fs.open(new Path(dataFile + ".idx"));
        m_dataFile = fs.open(new Path(dataFile));
    }

    public void close() throws IOException {
        synchronized (m_indexFile) {
            m_indexFile.close();
            m_dataFile.close();
        }
    }

    private DataInputStream createDataInputStream(byte[] buf) {
        DataInputStream in = null;

        try {
            in = new DataInputStream(new SnappyInputStream(new ByteArrayInputStream(buf)));
        } catch (IOException e) {
            try {
                in = new DataInputStream(new GZIPInputStream(new ByteArrayInputStream(buf)));
            } catch (IOException ioe) {
                Cat.logError(ioe);
            }
        }
        return in;
    }

    public byte[] readMessage(int index) throws IOException {
        int blockAddress;
        int blockOffset;
        byte[] buf;

        synchronized (m_indexFile) {
            m_indexFile.seek(index * 6L);
            blockAddress = m_indexFile.readInt();
            blockOffset = m_indexFile.readShort() & 0xFFFF;
        }

        synchronized (m_dataFile) {
            m_dataFile.seek(blockAddress);
            buf = new byte[m_dataFile.readInt()];
            m_dataFile.readFully(buf);
        }

        DataInputStream in = createDataInputStream(buf);

        if (in != null) {
            try {
                in.skip(blockOffset);

                int len = in.readInt();
                byte[] data = new byte[len];

                in.readFully(data);
                return data;
            } finally {
                try {
                    in.close();
                } catch (Exception e) {
                    // ignore it
                }
            }
        } else {
            return null;
        }
    }

}