ResettableFileInputStream.java Source code

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Here is the source code for ResettableFileInputStream.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.                                           *
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import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * @author  Federico Barbieri <fede@apache.org>
 */
public class ResettableFileInputStream extends InputStream {
    protected static final int DEFAULT_BUFFER_SIZE = 1024;

    protected final String m_filename;
    protected int m_bufferSize;
    protected InputStream m_inputStream;
    protected long m_position;
    protected long m_mark;
    protected boolean m_isMarkSet;

    public ResettableFileInputStream(final File file) throws IOException {
        this(file.getCanonicalPath());
    }

    public ResettableFileInputStream(final String filename) throws IOException {
        this(filename, DEFAULT_BUFFER_SIZE);
    }

    public ResettableFileInputStream(final String filename, final int bufferSize) throws IOException {
        m_bufferSize = bufferSize;
        m_filename = filename;
        m_position = 0;

        m_inputStream = newStream();
    }

    public void mark(final int readLimit) {
        m_isMarkSet = true;
        m_mark = m_position;
        m_inputStream.mark(readLimit);
    }

    public boolean markSupported() {
        return true;
    }

    public void reset() throws IOException {
        if (!m_isMarkSet) {
            throw new IOException("Unmarked Stream");
        }
        try {
            m_inputStream.reset();
        } catch (final IOException ioe) {
            try {
                m_inputStream.close();
                m_inputStream = newStream();
                m_inputStream.skip(m_mark);
                m_position = m_mark;
            } catch (final Exception e) {
                throw new IOException("Cannot reset current Stream: " + e.getMessage());
            }
        }
    }

    protected InputStream newStream() throws IOException {
        return new BufferedInputStream(new FileInputStream(m_filename), m_bufferSize);
    }

    public int available() throws IOException {
        return m_inputStream.available();
    }

    public void close() throws IOException {
        m_inputStream.close();
    }

    public int read() throws IOException {
        m_position++;
        return m_inputStream.read();
    }

    public int read(final byte[] bytes, final int offset, final int length) throws IOException {
        final int count = m_inputStream.read(bytes, offset, length);
        m_position += count;
        return count;
    }

    public long skip(final long count) throws IOException {
        m_position += count;
        return m_inputStream.skip(count);
    }
}