org.apache.hadoop.io.compress.CompressionInputStream.java Source code

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Here is the source code for org.apache.hadoop.io.compress.CompressionInputStream.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.io.compress;

import java.io.IOException;
import java.io.InputStream;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.PositionedReadable;
import org.apache.hadoop.fs.Seekable;

/**
 * A compression input stream.
 *
 * <p>Implementations are assumed to be buffered.  This permits clients to
 * reposition the underlying input stream then call {@link #resetState()},
 * without having to also synchronize client buffers.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public abstract class CompressionInputStream extends InputStream implements Seekable {
    /**
     * The input stream to be compressed. 
     */
    protected final InputStream in;
    protected long maxAvailableData = 0L;

    private Decompressor trackedDecompressor;

    /**
     * Create a compression input stream that reads
     * the decompressed bytes from the given stream.
     * 
     * @param in The input stream to be compressed.
     * @throws IOException
     */
    protected CompressionInputStream(InputStream in) throws IOException {
        if (!(in instanceof Seekable) || !(in instanceof PositionedReadable)) {
            this.maxAvailableData = in.available();
        }
        this.in = in;
    }

    @Override
    public void close() throws IOException {
        try {
            in.close();
        } finally {
            if (trackedDecompressor != null) {
                CodecPool.returnDecompressor(trackedDecompressor);
                trackedDecompressor = null;
            }
        }
    }

    /**
     * Read bytes from the stream.
     * Made abstract to prevent leakage to underlying stream.
     */
    @Override
    public abstract int read(byte[] b, int off, int len) throws IOException;

    /**
     * Reset the decompressor to its initial state and discard any buffered data,
     * as the underlying stream may have been repositioned.
     */
    public abstract void resetState() throws IOException;

    /**
     * This method returns the current position in the stream.
     *
     * @return Current position in stream as a long
     */
    @Override
    public long getPos() throws IOException {
        if (!(in instanceof Seekable) || !(in instanceof PositionedReadable)) {
            //This way of getting the current position will not work for file
            //size which can be fit in an int and hence can not be returned by
            //available method.
            return (this.maxAvailableData - this.in.available());
        } else {
            return ((Seekable) this.in).getPos();
        }

    }

    /**
     * This method is current not supported.
     *
     * @throws UnsupportedOperationException
     */

    @Override
    public void seek(long pos) throws UnsupportedOperationException {
        throw new UnsupportedOperationException();
    }

    /**
     * This method is current not supported.
     *
     * @throws UnsupportedOperationException
     */
    @Override
    public boolean seekToNewSource(long targetPos) throws UnsupportedOperationException {
        throw new UnsupportedOperationException();
    }

    void setTrackedDecompressor(Decompressor decompressor) {
        trackedDecompressor = decompressor;
    }
}