83 lines
1.9 KiB
Java
83 lines
1.9 KiB
Java
package com.webcodepro.shrinkit.io;
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import java.io.IOException;
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import java.io.OutputStream;
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/**
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* The RleOutputStream handles the NuFX RLE data stream.
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* This data stream is byte oriented. If a repeat occurs,
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* the data stream will contain the marker byte, byte to
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* repeat, and the number of repeats (zero based; ie, $00=1,
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* $01=2, ... $ff=256). The default marker is $DB.
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*
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* @author robgreene@users.sourceforge.net
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*/
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public class RleOutputStream extends OutputStream {
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private OutputStream os;
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private int escapeChar;
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private int repeatedByte;
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private int numBytes = -1;
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/**
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* Create an RLE output stream with the default marker byte.
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*/
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public RleOutputStream(OutputStream bs) {
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this(bs, 0xdb);
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}
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/**
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* Create an RLE output stream with the specified marker byte.
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*/
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public RleOutputStream(OutputStream os, int escapeChar) {
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this.os = os;
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this.escapeChar = escapeChar;
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}
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/**
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* Write the next byte to the output stream.
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*/
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public void write(int b) throws IOException {
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if (numBytes == -1) {
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repeatedByte = b;
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numBytes++;
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} else if (repeatedByte == b) {
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numBytes++;
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if (numBytes > 255) {
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flush();
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}
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} else {
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flush();
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repeatedByte = b;
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numBytes++;
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}
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}
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/**
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* Flush out any remaining data.
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* If we only have 1 byte and it is <em>not</em> the repeated
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* byte, we can just dump that byte. Otherwise, we need to
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* write out the escape character, the repeated byte, and
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* the number of bytes.
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*/
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public void flush() throws IOException {
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if (numBytes != -1) {
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if (numBytes == 0 && escapeChar != repeatedByte) {
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os.write(repeatedByte);
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} else {
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os.write(escapeChar);
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os.write(repeatedByte);
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os.write(numBytes);
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}
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numBytes = -1;
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}
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}
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/**
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* Close out the data stream. Makes sure the repeate buffer
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* is flushed.
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*/
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public void close() throws IOException {
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flush();
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os.close();
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}
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}
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