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annotate org.eclipse.swt.gtk.linux.x86/src/org/eclipse/swt/internal/image/PngHuffmanTable.d @ 125:c43718956f21 default tip
Updated the snippets status.
| author | Jacob Carlborg <doob@me.com> |
|---|---|
| date | Thu, 11 Aug 2011 19:55:14 +0200 |
| parents | 536e43f63c81 |
| children |
| rev | line source |
|---|---|
| 25 | 1 /******************************************************************************* |
| 2 * Copyright (c) 2000, 2008 IBM Corporation and others. | |
| 3 * All rights reserved. This program and the accompanying materials | |
| 4 * are made available under the terms of the Eclipse Public License v1.0 | |
| 5 * which accompanies this distribution, and is available at | |
| 6 * http://www.eclipse.org/legal/epl-v10.html | |
| 7 * | |
| 8 * Contributors: | |
| 9 * IBM Corporation - initial API and implementation | |
| 10 * Port to the D programming language: | |
| 11 * Frank Benoit <benoit@tionex.de> | |
| 12 *******************************************************************************/ | |
| 13 module org.eclipse.swt.internal.image.PngHuffmanTable; | |
| 14 | |
| 15 import org.eclipse.swt.internal.image.PngDecodingDataStream; | |
| 16 | |
| 17 public class PngHuffmanTable { | |
| 18 CodeLengthInfo[] codeLengthInfo; | |
| 19 int[] codeValues; | |
| 20 | |
| 21 static const int MAX_CODE_LENGTH = 15; | |
| 22 static const int BAD_CODE = 0xFFFFFFF; | |
| 23 static const int incs[] = [1391376, 463792, 198768, 86961, 33936, 13776, 4592, 1968, 861, 336, 112, 48, 21, 7, 3, 1]; | |
| 24 | |
| 25 this (int[] lengths) { | |
| 26 initialize(lengths); | |
| 27 generateTable(lengths); | |
| 28 } | |
| 29 | |
|
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536e43f63c81
Comprehensive update for Win32/Linux32 dmd-2.053/dmd-1.068+Tango-r5661
Denis Shelomovskij <verylonglogin.reg@gmail.com>
parents:
25
diff
changeset
|
30 private void initialize(in int[] lengths) { |
| 25 | 31 codeValues = new int[lengths.length]; |
| 32 for (int i = 0; i < codeValues.length; i++) { | |
| 33 codeValues[i] = i; | |
| 34 } | |
| 35 | |
| 36 // minCodesByLength[n] : The smallest Huffman code of length n + 1. | |
| 37 // maxCodesByLength[n] : The largest Huffman code of length n + 1. | |
| 38 // indexesByLength[n] : Index into the values array. First value with a code of length n + 1. | |
| 39 codeLengthInfo = new CodeLengthInfo[MAX_CODE_LENGTH]; | |
| 40 for (int i = 0; i < MAX_CODE_LENGTH; i++) { | |
| 41 codeLengthInfo[i] = new CodeLengthInfo(); | |
| 42 codeLengthInfo[i].length = i; | |
| 43 codeLengthInfo[i].baseIndex = 0; | |
| 44 codeLengthInfo[i].min = BAD_CODE; | |
| 45 codeLengthInfo[i].max = -1; | |
| 46 } | |
| 47 } | |
| 48 | |
| 49 private void generateTable(int[] lengths) { | |
| 50 // Sort the values using shellsort. Primary key is code size. Secondary key is value. | |
| 51 int codeValuesTemp; | |
| 52 for (int k = 0; k < 16; k++) { | |
| 53 for (int h = incs[k], i = h; i < lengths.length; i++) { | |
| 54 int v = lengths[i]; | |
| 55 codeValuesTemp = codeValues[i]; | |
| 56 int j = i; | |
| 57 while (j >= h && (lengths[j - h] > v || (lengths[j - h] is v && codeValues[j - h] > codeValuesTemp))) { | |
| 58 lengths[j] = lengths[j - h]; | |
| 59 codeValues[j] = codeValues[j - h]; | |
| 60 j -= h; | |
| 61 } | |
| 62 lengths[j] = v; | |
| 63 codeValues[j] = codeValuesTemp; | |
| 64 } | |
| 65 } | |
| 66 | |
| 67 // These values in these arrays correspond to the elements of the | |
| 68 // "values" array. The Huffman code for codeValues[N] is codes[N] | |
| 69 // and the length of the code is lengths[N]. | |
| 70 int[] codes = new int[lengths.length]; | |
| 71 int lastLength = 0; | |
| 72 int code = 0; | |
| 73 for (int i = 0; i < lengths.length; i++) { | |
| 74 while (lastLength !is lengths[i]) { | |
| 75 lastLength++; | |
| 76 code <<= 1; | |
| 77 } | |
| 78 if (lastLength !is 0) { | |
| 79 codes[i] = code; | |
| 80 code++; | |
| 81 } | |
| 82 } | |
| 83 | |
| 84 int last = 0; | |
| 85 for (int i = 0; i < lengths.length; i++) { | |
| 86 if (last !is lengths[i]) { | |
| 87 last = lengths[i]; | |
| 88 codeLengthInfo[last - 1].baseIndex = i; | |
| 89 codeLengthInfo[last - 1].min = codes[i]; | |
| 90 } | |
| 91 if (last !is 0) codeLengthInfo[last - 1].max = codes[i]; | |
| 92 } | |
| 93 } | |
| 94 | |
| 95 int getNextValue(PngDecodingDataStream stream) { | |
| 96 int code = stream.getNextIdatBit(); | |
| 97 int codelength = 0; | |
| 98 | |
| 99 // Here we are taking advantage of the fact that 1 bits are used as | |
| 100 // a prefix to the longer codeValues. | |
| 101 while (codelength < MAX_CODE_LENGTH && code > codeLengthInfo[codelength].max) { | |
| 102 code = ((code << 1) | stream.getNextIdatBit()); | |
| 103 codelength++; | |
| 104 } | |
| 105 if (codelength >= MAX_CODE_LENGTH) stream.error(); | |
| 106 | |
| 107 // Now we have a Huffman code of length (codelength + 1) that | |
| 108 // is somewhere in the range | |
| 109 // minCodesByLength[codelength]..maxCodesByLength[codelength]. | |
| 110 // This code is the (offset + 1)'th code of (codelength + 1); | |
| 111 int offset = code - codeLengthInfo[codelength].min; | |
| 112 | |
| 113 // indexesByLength[codelength] is the first code of length (codelength + 1) | |
| 114 // so now we can look up the value for the Huffman code in the table. | |
| 115 int index = codeLengthInfo[codelength].baseIndex + offset; | |
| 116 return codeValues[index]; | |
| 117 } | |
| 118 | |
| 119 static class CodeLengthInfo { | |
| 120 int length; | |
| 121 int max; | |
| 122 int min; | |
| 123 int baseIndex; | |
| 124 } | |
| 125 | |
| 126 } |