co.cask.tigon.io.SeekableInputStream.java Source code

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Here is the source code for co.cask.tigon.io.SeekableInputStream.java

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/*
 * Copyright  2014 Cask Data, Inc.
 *
 * Licensed 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 co.cask.tigon.io;

import org.apache.hadoop.fs.Seekable;

import java.io.FileInputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Abstract base class for {@link java.io.InputStream} that implements the
 * {@link org.apache.hadoop.fs.Seekable} interface.
 */
public abstract class SeekableInputStream extends FilterInputStream implements Seekable {

    /**
     * Creates a {@link SeekableInputStream} from the given {@link java.io.InputStream}. Exception will be
     * thrown if failed to do so.
     *
     * @throws java.io.IOException If the given input stream is not seekable.
     */
    public static SeekableInputStream create(InputStream input) throws IOException {
        if (input instanceof SeekableInputStream) {
            return (SeekableInputStream) input;
        }
        if (input instanceof FileInputStream) {
            return create((FileInputStream) input);
        }
        if (input instanceof Seekable) {
            final Seekable seekable = (Seekable) input;
            return new SeekableInputStream(input) {
                @Override
                public void seek(long pos) throws IOException {
                    seekable.seek(pos);
                }

                @Override
                public long getPos() throws IOException {
                    return seekable.getPos();
                }

                @Override
                public boolean seekToNewSource(long targetPos) throws IOException {
                    return seekable.seekToNewSource(targetPos);
                }
            };
        }

        throw new IOException("Failed to create SeekableInputStream from " + input.getClass());
    }

    /**
     * Creates a {@link SeekableInputStream} from the given {@link java.io.FileInputStream}.
     */
    private static SeekableInputStream create(final FileInputStream input) {
        return new SeekableInputStream(input) {
            @Override
            public void seek(long pos) throws IOException {
                input.getChannel().position(pos);
            }

            @Override
            public long getPos() throws IOException {
                return input.getChannel().position();
            }

            @Override
            public boolean seekToNewSource(long targetPos) throws IOException {
                return false;
            }
        };
    }

    protected SeekableInputStream(InputStream in) {
        super(in);
    }
}