net.sourceforge.subsonic.io.RangeOutputStream.java Source code

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Here is the source code for net.sourceforge.subsonic.io.RangeOutputStream.java

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/*
 This file is part of Subsonic.
    
 Subsonic is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
    
 Subsonic is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
    
 You should have received a copy of the GNU General Public License
 along with Subsonic.  If not, see <http://www.gnu.org/licenses/>.
    
 Copyright 2009 (C) Sindre Mehus
 */
package net.sourceforge.subsonic.io;

import org.apache.commons.lang.math.Range;

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

/**
 * Special output stream for grabbing only part of a passed stream.
 *
 * @author Sindre Mehus (based on code found on http://www.koders.com/
 */
public class RangeOutputStream extends FilterOutputStream {

    /**
     * The starting index.
     */
    private long start;

    /**
     * The ending index.
     */
    private long end;

    /**
     * The current position.
     */
    protected long pos;

    /**
     * Wraps the given output stream in a RangeOutputStream, using the values
     * in the given range, unless the range is <code>null</code> in which case
     * the original OutputStream is returned.
     *
     * @param out   The output stream to wrap in a RangeOutputStream.
     * @param range The range, may be <code>null</code>.
     * @return The possibly wrapped output stream.
     */
    public static OutputStream wrap(OutputStream out, Range range) {
        if (range == null) {
            return out;
        }
        return new RangeOutputStream(out, range.getMinimumLong(), range.getMaximumLong());
    }

    /**
     * Creates the stream with the passed start and end.
     *
     * @param out   The stream to write to.
     * @param start The starting position.
     * @param end   The ending position.
     */
    public RangeOutputStream(OutputStream out, long start, long end) {
        super(out);
        this.start = start;
        this.end = end;
        pos = 0;
    }

    /**
     * Writes the byte IF it is within the range, otherwise it only
     * increments the position.
     *
     * @param b The byte to write.
     * @throws IOException Thrown if there was a problem writing to the stream.
     */
    @Override
    public void write(int b) throws IOException {
        if ((pos >= start) && (pos <= end)) {
            super.write(b);
        }
        pos++;
    }

    /**
     * Writes the bytes IF it is within the range, otherwise it only
     * increments the position.
     *
     * @param b   The bytes to write.
     * @param off The offset to start at.
     * @param len The length to write.
     * @throws IOException Thrown if there was a problem writing to the stream.
     */
    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        boolean allowWrite = false;
        long newPos = pos + off, newOff = off, newLen = len;

        // Check to see if we are in the range
        if (newPos <= end) {
            if (newPos >= start) {
                // We are so check to make sure we don't leave it
                if (newPos + newLen > end) {
                    newLen = end - newPos;
                }

                // Enable writing
                allowWrite = true;
            }

            // We aren't yet in the range, but if see if the proposed write
            // would place us there
            else if (newPos + newLen >= start) {
                // It would so, update the offset
                newOff += start - newPos;

                // New offset means, a new position, so update that too
                newPos = newOff + pos;
                newLen = len + (pos - newPos);

                // Make sure we don't go past the range
                if (newPos + newLen > end) {
                    newLen = end - newPos;
                }

                // Enable writting
                allowWrite = true;
            }
        }

        // If we have enabled writing, do the write!
        if (allowWrite) {
            out.write(b, (int) newOff, (int) newLen);
        }

        // Move the cursor along
        pos += off + len;
    }
}