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

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Here is the source code for org.apache.hadoop.fs.FSDataOutputStream.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.fs;

import java.io.DataOutputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

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

/** Utility that wraps a {@link OutputStream} in a {@link DataOutputStream}.
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class FSDataOutputStream extends DataOutputStream implements Syncable, CanSetDropBehind, StreamCapabilities {
    private final OutputStream wrappedStream;

    private static class PositionCache extends FilterOutputStream {
        private final FileSystem.Statistics statistics;
        private long position;

        PositionCache(OutputStream out, FileSystem.Statistics stats, long pos) {
            super(out);
            statistics = stats;
            position = pos;
        }

        @Override
        public void write(int b) throws IOException {
            out.write(b);
            position++;
            if (statistics != null) {
                statistics.incrementBytesWritten(1);
            }
        }

        @Override
        public void write(byte b[], int off, int len) throws IOException {
            out.write(b, off, len);
            position += len; // update position
            if (statistics != null) {
                statistics.incrementBytesWritten(len);
            }
        }

        long getPos() {
            return position; // return cached position
        }

        @Override
        public void close() throws IOException {
            // ensure close works even if a null reference was passed in
            if (out != null) {
                out.close();
            }
        }
    }

    public FSDataOutputStream(OutputStream out, FileSystem.Statistics stats) {
        this(out, stats, 0);
    }

    public FSDataOutputStream(OutputStream out, FileSystem.Statistics stats, long startPosition) {
        super(new PositionCache(out, stats, startPosition));
        wrappedStream = out;
    }

    /**
     * Get the current position in the output stream.
     *
     * @return the current position in the output stream
     */
    public long getPos() {
        return ((PositionCache) out).getPos();
    }

    /**
     * Close the underlying output stream.
     */
    @Override
    public void close() throws IOException {
        out.close(); // This invokes PositionCache.close()
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("FSDataOutputStream{");
        sb.append("wrappedStream=").append(wrappedStream);
        sb.append('}');
        return sb.toString();
    }

    /**
     * Get a reference to the wrapped output stream.
     *
     * @return the underlying output stream
     */
    @InterfaceAudience.LimitedPrivate({ "HDFS" })
    public OutputStream getWrappedStream() {
        return wrappedStream;
    }

    @Override
    public boolean hasCapability(String capability) {
        if (wrappedStream instanceof StreamCapabilities) {
            return ((StreamCapabilities) wrappedStream).hasCapability(capability);
        }
        return false;
    }

    @Override // Syncable
    public void hflush() throws IOException {
        if (wrappedStream instanceof Syncable) {
            ((Syncable) wrappedStream).hflush();
        } else {
            wrappedStream.flush();
        }
    }

    @Override // Syncable
    public void hsync() throws IOException {
        if (wrappedStream instanceof Syncable) {
            ((Syncable) wrappedStream).hsync();
        } else {
            wrappedStream.flush();
        }
    }

    @Override
    public void setDropBehind(Boolean dropBehind) throws IOException {
        try {
            ((CanSetDropBehind) wrappedStream).setDropBehind(dropBehind);
        } catch (ClassCastException e) {
            throw new UnsupportedOperationException(
                    "the wrapped stream does " + "not support setting the drop-behind caching setting.");
        }
    }
}