Added RleOutputStream for RLE compression.

src/com/webcodepro/shrinkit/io/RleOutputStream.java

@@ -0,0 +1,82 @@
+package com.webcodepro.shrinkit.io;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * The RleOutputStream handles the NuFX RLE data stream.
+ * This data stream is byte oriented.  If a repeat occurs,
+ * the data stream will contain the marker byte, byte to 
+ * repeat, and the number of repeats (zero based; ie, $00=1,
+ * $01=2, ... $ff=256).  The default marker is $DB.
+ * 
+ * @author robgreene@users.sourceforge.net
+ */
+public class RleOutputStream extends OutputStream {
+	private OutputStream os;
+	private int escapeChar;
+	private int repeatedByte;
+	private int numBytes = -1;
+	
+	/**
+	 * Create an RLE output stream with the default marker byte.
+	 */
+	public RleOutputStream(OutputStream bs) {
+		this(bs, 0xdb);
+	}
+	/**
+	 * Create an RLE output stream with the specified marker byte.
+	 */
+	public RleOutputStream(OutputStream os, int escapeChar) {
+		this.os = os;
+		this.escapeChar = escapeChar;
+	}
+	
+	/**
+	 * Write the next byte to the output stream.
+	 */
+	public void write(int b) throws IOException {
+		if (numBytes == -1) {
+			repeatedByte = b;
+			numBytes++;
+		} else if (repeatedByte == b) {
+			numBytes++;
+			if (numBytes > 255) {
+				flush();
+			}
+		} else {
+			flush();
+			repeatedByte = b;
+			numBytes++;
+		}
+	}
+	
+	/**
+	 * Flush out any remaining data.
+	 * If we only have 1 byte and it is <em>not</em> the repeated
+	 * byte, we can just dump that byte.  Otherwise, we need to
+	 * write out the escape character, the repeated byte, and
+	 * the number of bytes. 
+	 */
+	public void flush() throws IOException {
+		if (numBytes != -1) {
+			if (numBytes == 0 && escapeChar != repeatedByte) {
+				os.write(repeatedByte);
+			} else {
+				os.write(escapeChar);
+				os.write(repeatedByte);
+				os.write(numBytes);
+			}
+			numBytes = -1;
+		}
+	}
+	
+	/**
+	 * Close out the data stream.  Makes sure the repeate buffer
+	 * is flushed.
+	 */
+	public void close() throws IOException {
+		flush();
+		os.close();
+	}
+}

test_src/com/webcodepro/shrinkit/io/RleTest.java

@@ -1,5 +1,6 @@
 package com.webcodepro.shrinkit.io;
 
+import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
@@ -11,23 +12,59 @@ import java.io.OutputStream;
  * @author robgreene@users.sourceforge.net
  */
 public class RleTest extends TestCaseHelper {
+	/**
+	 * Test the RleInputStream to verify decoding.
+	 */
 	public void testInputStream() throws IOException {
-		InputStream is = new RleInputStream(new LittleEndianByteInputStream(getPatternFileRle()));
+		InputStream is = new RleInputStream(new ByteArrayInputStream(getPatternFileRle()));
 		ByteArrayOutputStream os = new ByteArrayOutputStream();
 		copy(is,os);
 		byte[] expected = getPatternFileUncompressed();
 		byte[] actual = os.toByteArray();
 		assertEquals(expected, actual);
 	}
+	/**
+	 * Test the RleOutputStream to verify compression.
+	 */
+	public void testOutputStream() throws IOException {
+		ByteArrayOutputStream baos = new ByteArrayOutputStream();
+		RleOutputStream os = new RleOutputStream(baos);
+		ByteArrayInputStream is = new ByteArrayInputStream(getPatternFileUncompressed());
+		copy(is,os);
+		byte[] expected = getPatternFileRle();
+		byte[] actual = baos.toByteArray();
+		assertEquals(expected, actual);
+	}
+	/**
+	 * Test the RleOutputStream with the escape character to ensure it <em>always</em> is encoded.
+	 * Note that a file with lots of 0xdb codes will grow.
+	 */
+	public void testOutputStreamEscapeCharacter() throws IOException {
+		ByteArrayOutputStream baos = new ByteArrayOutputStream();
+		RleOutputStream os = new RleOutputStream(baos);
+		ByteArrayInputStream is = new ByteArrayInputStream(new byte[] { (byte)0xdb, (byte)0xdb, 0x00, (byte)0xdb });
+		copy(is,os);
+		byte[] expected = new byte[] { (byte)0xdb, (byte)0xdb, 0x01, 0x00, (byte)0xdb, (byte)0xdb, 0x00 };
+		byte[] actual = baos.toByteArray();
+		assertEquals(expected, actual);
+	}
 	
+	/**
+	 * Copy the input stream to the output stream.
+	 */
 	private void copy(InputStream is, OutputStream os) throws IOException {
 		int b = is.read();
 		while (b != -1) {
 			os.write(b);
 			b = is.read();
 		}
+		is.close();
+		os.close();
 	}
-	
+
+	/**
+	 * This the RLE compressed pattern file that happens to not compress via LZW.
+	 */
 	private byte[] getPatternFileRle() {
 		return new byte[] {
 			(byte)0xdb, 0x01, (byte)0xfd, 
@@ -49,6 +86,9 @@ public class RleTest extends TestCaseHelper {
 			(byte)0xdb, 0x11, (byte)0x97
 		};
 	}
+	/**
+	 * This is the uncompressed pattern file that happens to not compress via LZW.
+	 */
 	private byte[] getPatternFileUncompressed() {
 		byte[] data = new byte[4096];
 		int value = 0x01;