--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwt/internal/image/PngHuffmanTable.d	Sat Aug 09 17:00:02 2008 +0200
@@ -0,0 +1,125 @@
+/*******************************************************************************
+ * 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;
+
+public class PngHuffmanTable {
+    CodeLengthInfo[] codeLengthInfo;
+    int[] codeValues;
+    
+    static final int MAX_CODE_LENGTH = 15;
+    static final int BAD_CODE = 0xFFFFFFF;
+    static final int incs[] = {1391376, 463792, 198768, 86961, 33936, 13776, 4592, 1968, 861, 336, 112, 48, 21, 7, 3, 1};
+
+PngHuffmanTable (int[] lengths) {
+    super();
+    initialize(lengths);
+    generateTable(lengths);
+}
+
+private void initialize(int[] lengths) {
+    codeValues = new int[lengths.length];
+    for (int i = 0; i < codeValues.length; i++) {
+        codeValues[i] = i;
+    }
+    
+    // minCodesByLength[n] : The smallest Huffman code of length n + 1.
+    // maxCodesByLength[n] : The largest Huffman code of length n + 1.
+    // indexesByLength[n] : Index into the values array. First value with a code of length n + 1.
+    codeLengthInfo = new CodeLengthInfo[MAX_CODE_LENGTH];
+    for (int i = 0; i < MAX_CODE_LENGTH; i++) {
+        codeLengthInfo[i] = new CodeLengthInfo();
+        codeLengthInfo[i].length = i;
+        codeLengthInfo[i].baseIndex = 0;
+        codeLengthInfo[i].min = BAD_CODE;
+        codeLengthInfo[i].max = -1;
+    }
+}
+    
+private void generateTable(int[] lengths) {
+    // Sort the values using shellsort. Primary key is code size. Secondary key is value.
+    int codeValuesTemp;
+    for (int k = 0; k < 16; k++) {
+        for (int h = incs[k], i = h; i < lengths.length; i++) {
+            int v = lengths[i];
+            codeValuesTemp = codeValues[i];
+            int j = i;
+            while (j >= h && (lengths[j - h] > v || (lengths[j - h] is v && codeValues[j - h] > codeValuesTemp))) {
+                lengths[j] = lengths[j - h];
+                codeValues[j] = codeValues[j - h];
+                j -= h;
+            }
+            lengths[j] = v;
+            codeValues[j] = codeValuesTemp;
+        }
+    }
+
+    // These values in these arrays correspond to the elements of the
+    // "values" array. The Huffman code for codeValues[N] is codes[N]
+    // and the length of the code is lengths[N].
+    int[] codes = new int[lengths.length];
+    int lastLength = 0;
+    int code = 0;
+    for (int i = 0; i < lengths.length; i++) {
+        while (lastLength !is lengths[i]) {
+            lastLength++;
+            code <<= 1;
+        }
+        if (lastLength !is 0) {
+            codes[i] = code;
+            code++;
+        }
+    }
+    
+    int last = 0;
+    for (int i = 0; i < lengths.length; i++) {
+        if (last !is lengths[i]) {
+            last = lengths[i];
+            codeLengthInfo[last - 1].baseIndex = i;
+            codeLengthInfo[last - 1].min = codes[i];
+        }
+        if (last !is 0) codeLengthInfo[last - 1].max = codes[i];
+    }
+}
+
+int getNextValue(PngDecodingDataStream stream) throws IOException {
+    int code = stream.getNextIdatBit();
+    int codelength = 0;
+
+    // Here we are taking advantage of the fact that 1 bits are used as
+    // a prefix to the longer codeValues.
+    while (codelength < MAX_CODE_LENGTH && code > codeLengthInfo[codelength].max) {
+        code = ((code << 1) | stream.getNextIdatBit());
+        codelength++;
+    }
+    if (codelength >= MAX_CODE_LENGTH) stream.error();
+
+    // Now we have a Huffman code of length (codelength + 1) that
+    // is somewhere in the range
+    // minCodesByLength[codelength]..maxCodesByLength[codelength].
+    // This code is the (offset + 1)'th code of (codelength + 1);
+    int offset = code - codeLengthInfo[codelength].min;
+
+    // indexesByLength[codelength] is the first code of length (codelength + 1)
+    // so now we can look up the value for the Huffman code in the table.
+    int index = codeLengthInfo[codelength].baseIndex + offset;
+    return codeValues[index];
+}   
+    
+static class CodeLengthInfo {
+    int length;
+    int max;
+    int min;
+    int baseIndex;
+}
+
+}