org.openpdf.renderer.decode.RunLengthDecode Maven / Gradle / Ivy
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/*
* Copyright 2009 Sun Microsystems, Inc., 4150 Network Circle,
* Santa Clara, California 95054, U.S.A. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package org.openpdf.renderer.decode;
import java.io.ByteArrayOutputStream;
import java.nio.ByteBuffer;
import org.openpdf.renderer.PDFObject;
import org.openpdf.renderer.PDFParseException;
/**
* decode an array of Run Length encoded bytes into a byte array
*
* @author Mike Wessler
*/
public class RunLengthDecode {
/** the end of data in the RunLength encoding. */
private static final int RUN_LENGTH_EOD = 128;
private ByteBuffer buf;
/**
* initialize the decoder with an array of bytes in RunLength format
*/
private RunLengthDecode(ByteBuffer buf) {
this.buf = buf;
}
/**
* decode the array
*
* @return the decoded bytes
*/
private ByteBuffer decode() {
// start at the beginning of the buffer
this.buf.rewind();
// allocate the output buffer
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int dupAmount;
byte[] buffer = new byte[128];
while ((dupAmount = this.buf.get()&0xFF) != RUN_LENGTH_EOD) {
if (dupAmount >= 0 && dupAmount <= 127) {
int amountToCopy = dupAmount + 1;
this.buf.get(buffer, 0, amountToCopy);
baos.write(buffer, 0, amountToCopy);
} else {
byte dupByte = this.buf.get();
for (int i = 0; i < 257 - dupAmount; i++) {
baos.write(dupByte);
}
}
}
return ByteBuffer.wrap(baos.toByteArray());
}
/**
* decode an array of bytes in RunLength format.
*
* RunLength format consists of a sequence of a byte-oriented format based
* on run length. There are a series of "runs", where a run is a length byte
* followed by 1 to 128 bytes of data. If the length is 0-127, the following
* length+1 (1 to 128) bytes are to be copied. If the length is 129 through
* 255, the following single byte is copied 257-length (2 to 128) times. A
* length value of 128 means and End of Data (EOD).
*
* @param buf
* the RUnLEngth encoded bytes in a byte buffer
*
* @param params
* parameters to the decoder (ignored)
* @return the decoded bytes
*/
public static ByteBuffer decode(ByteBuffer buf, PDFObject params) throws PDFParseException {
RunLengthDecode me = new RunLengthDecode(buf);
return me.decode();
}
}