--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwt/internal/image/PngDecodingDataStream.d	Sat Aug 09 17:00:02 2008 +0200
@@ -0,0 +1,135 @@
+/*******************************************************************************
+ * Copyright (c) 2000, 2006 IBM Corporation and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ *******************************************************************************/
+module dwt.internal.image;
+
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import dwt.DWT;
+
+public class PngDecodingDataStream : InputStream {
+    InputStream stream;
+    byte currentByte;
+    int nextBitIndex;
+    
+    PngLzBlockReader lzBlockReader;
+    int adlerValue;
+    
+    static final int PRIME = 65521;
+    static final int MAX_BIT = 7;       
+    
+PngDecodingDataStream(InputStream stream) throws IOException {
+    super();
+    this.stream = stream;
+    nextBitIndex = MAX_BIT + 1;
+    adlerValue = 1;
+    lzBlockReader = new PngLzBlockReader(this);
+    readCompressedDataHeader();
+    lzBlockReader.readNextBlockHeader();
+}
+
+/**
+ * This method should be called when the image decoder thinks
+ * that all of the compressed image data has been read. This
+ * method will ensure that the next data value is an end of 
+ * block marker. If there are more blocks after this one,
+ * the method will read them and ensure that they are empty.
+ */
+void assertImageDataAtEnd() throws IOException {
+    lzBlockReader.assertCompressedDataAtEnd();
+}
+
+public void close() throws IOException {
+    assertImageDataAtEnd();
+    checkAdler();
+}
+
+int getNextIdatBits(int length) throws IOException {
+    int value = 0;
+    for (int i = 0; i < length; i++) {
+        value |= (getNextIdatBit() << i);
+    }
+    return value;
+}
+
+int getNextIdatBit() throws IOException {
+    if (nextBitIndex > MAX_BIT) {
+        currentByte = getNextIdatByte();
+        nextBitIndex = 0;
+    }
+    return (currentByte & (1 << nextBitIndex)) >> nextBitIndex++;
+}
+
+byte getNextIdatByte() throws IOException { 
+    byte nextByte = (byte)stream.read();
+    nextBitIndex = MAX_BIT + 1;
+    return nextByte;
+}
+
+void updateAdler(byte value) {
+    int low = adlerValue & 0xFFFF;
+    int high = (adlerValue >> 16) & 0xFFFF;
+    int valueInt = value & 0xFF;
+    low = (low + valueInt) % PRIME;
+    high = (low + high) % PRIME;
+    adlerValue = (high << 16) | low;
+}
+
+public int read() throws IOException {
+    byte nextDecodedByte = lzBlockReader.getNextByte();
+    updateAdler(nextDecodedByte);
+    return nextDecodedByte & 0xFF;
+}
+
+public int read(byte[] buffer, int off, int len) throws IOException {
+    for (int i = 0; i < len; i++) {
+        int b = read();
+        if (b is -1) return i;
+        buffer[off + i] = (byte)b;
+    }
+    return len;
+}
+
+void error() {
+    DWT.error(DWT.ERROR_INVALID_IMAGE);
+}
+
+private void readCompressedDataHeader() throws IOException {
+    byte headerByte1 = getNextIdatByte();
+    byte headerByte2 = getNextIdatByte();
+    
+    int number = ((headerByte1 & 0xFF) << 8) | (headerByte2 & 0xFF);
+    if (number % 31 !is 0) error();
+    
+    int compressionMethod = headerByte1 & 0x0F;
+    if (compressionMethod !is 8) error();
+    
+    int windowSizeHint = (headerByte1 & 0xF0) >> 4;
+    if (windowSizeHint > 7) error();
+    int windowSize = (1 << (windowSizeHint + 8));
+    lzBlockReader.setWindowSize(windowSize);
+    
+    int dictionary = (headerByte2 & (1 << 5));
+    if (dictionary !is 0) error();
+    
+//  int compressionLevel = (headerByte2 & 0xC0) >> 6;
+}
+
+void checkAdler() throws IOException {
+    int storedAdler = ((getNextIdatByte() & 0xFF) << 24)
+        | ((getNextIdatByte() & 0xFF) << 16)
+        | ((getNextIdatByte() & 0xFF) << 8)
+        | (getNextIdatByte() & 0xFF);
+    if (storedAdler !is adlerValue) error();
+}
+
+}