org.apache.hadoop.fs.BufferedFSInputStream.java Source code

Introduction

Here is the source code for org.apache.hadoop.fs.BufferedFSInputStream.java

Source

/**
 * 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.fs;

import java.io.BufferedInputStream;
import java.io.EOFException;
import java.io.FileDescriptor;
import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

/**
 * A class that optimizes reading from FSInputStream by buffering
 */

@InterfaceAudience.Private
@InterfaceStability.Unstable
public class BufferedFSInputStream extends BufferedInputStream
        implements Seekable, PositionedReadable, HasFileDescriptor {
    /**
     * Creates a <code>BufferedFSInputStream</code>
     * with the specified buffer size,
     * and saves its  argument, the input stream
     * <code>in</code>, for later use.  An internal
     * buffer array of length  <code>size</code>
     * is created and stored in <code>buf</code>.
     *
     * @param   in     the underlying input stream.
     * @param   size   the buffer size.
     * @exception IllegalArgumentException if size <= 0.
     */
    public BufferedFSInputStream(FSInputStream in, int size) {
        super(in, size);
    }

    @Override
    public long getPos() throws IOException {
        if (in == null) {
            throw new IOException(FSExceptionMessages.STREAM_IS_CLOSED);
        }
        return ((FSInputStream) in).getPos() - (count - pos);
    }

    @Override
    public long skip(long n) throws IOException {
        if (n <= 0) {
            return 0;
        }

        seek(getPos() + n);
        return n;
    }

    @Override
    public void seek(long pos) throws IOException {
        if (in == null) {
            throw new IOException(FSExceptionMessages.STREAM_IS_CLOSED);
        }
        if (pos < 0) {
            throw new EOFException(FSExceptionMessages.NEGATIVE_SEEK);
        }
        if (this.pos != this.count) {
            // optimize: check if the pos is in the buffer
            // This optimization only works if pos != count -- if they are
            // equal, it's possible that the previous reads were just
            // longer than the total buffer size, and hence skipped the buffer.
            long end = ((FSInputStream) in).getPos();
            long start = end - count;
            if (pos >= start && pos < end) {
                this.pos = (int) (pos - start);
                return;
            }
        }

        // invalidate buffer
        this.pos = 0;
        this.count = 0;

        ((FSInputStream) in).seek(pos);
    }

    @Override
    public boolean seekToNewSource(long targetPos) throws IOException {
        pos = 0;
        count = 0;
        return ((FSInputStream) in).seekToNewSource(targetPos);
    }

    @Override
    public int read(long position, byte[] buffer, int offset, int length) throws IOException {
        return ((FSInputStream) in).read(position, buffer, offset, length);
    }

    @Override
    public void readFully(long position, byte[] buffer, int offset, int length) throws IOException {
        ((FSInputStream) in).readFully(position, buffer, offset, length);
    }

    @Override
    public void readFully(long position, byte[] buffer) throws IOException {
        ((FSInputStream) in).readFully(position, buffer);
    }

    @Override
    public FileDescriptor getFileDescriptor() throws IOException {
        if (in instanceof HasFileDescriptor) {
            return ((HasFileDescriptor) in).getFileDescriptor();
        } else {
            return null;
        }
    }
}