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00038 using System;
00039
00040 using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
00041
00042 namespace ICSharpCode.SharpZipLib.Zip.Compression
00043 {
00044
00048 public class InflaterHuffmanTree
00049 {
00050 static int MAX_BITLEN = 15;
00051 short[] tree;
00052
00056 public static InflaterHuffmanTree defLitLenTree;
00057
00061 public static InflaterHuffmanTree defDistTree;
00062
00063 static InflaterHuffmanTree()
00064 {
00065 try {
00066 byte[] codeLengths = new byte[288];
00067 int i = 0;
00068 while (i < 144) {
00069 codeLengths[i++] = 8;
00070 }
00071 while (i < 256) {
00072 codeLengths[i++] = 9;
00073 }
00074 while (i < 280) {
00075 codeLengths[i++] = 7;
00076 }
00077 while (i < 288) {
00078 codeLengths[i++] = 8;
00079 }
00080 defLitLenTree = new InflaterHuffmanTree(codeLengths);
00081
00082 codeLengths = new byte[32];
00083 i = 0;
00084 while (i < 32) {
00085 codeLengths[i++] = 5;
00086 }
00087 defDistTree = new InflaterHuffmanTree(codeLengths);
00088 } catch (Exception) {
00089 throw new SharpZipBaseException("InflaterHuffmanTree: static tree length illegal");
00090 }
00091 }
00092
00099 public InflaterHuffmanTree(byte[] codeLengths)
00100 {
00101 BuildTree(codeLengths);
00102 }
00103
00104 void BuildTree(byte[] codeLengths)
00105 {
00106 int[] blCount = new int[MAX_BITLEN + 1];
00107 int[] nextCode = new int[MAX_BITLEN + 1];
00108
00109 for (int i = 0; i < codeLengths.Length; i++) {
00110 int bits = codeLengths[i];
00111 if (bits > 0) {
00112 blCount[bits]++;
00113 }
00114 }
00115
00116 int code = 0;
00117 int treeSize = 512;
00118 for (int bits = 1; bits <= MAX_BITLEN; bits++) {
00119 nextCode[bits] = code;
00120 code += blCount[bits] << (16 - bits);
00121 if (bits >= 10) {
00122
00123 int start = nextCode[bits] & 0x1ff80;
00124 int end = code & 0x1ff80;
00125 treeSize += (end - start) >> (16 - bits);
00126 }
00127 }
00128
00129
00130
00131
00132
00133
00134
00135
00136
00137
00138 tree = new short[treeSize];
00139 int treePtr = 512;
00140 for (int bits = MAX_BITLEN; bits >= 10; bits--) {
00141 int end = code & 0x1ff80;
00142 code -= blCount[bits] << (16 - bits);
00143 int start = code & 0x1ff80;
00144 for (int i = start; i < end; i += 1 << 7) {
00145 tree[DeflaterHuffman.BitReverse(i)] = (short) ((-treePtr << 4) | bits);
00146 treePtr += 1 << (bits-9);
00147 }
00148 }
00149
00150 for (int i = 0; i < codeLengths.Length; i++) {
00151 int bits = codeLengths[i];
00152 if (bits == 0) {
00153 continue;
00154 }
00155 code = nextCode[bits];
00156 int revcode = DeflaterHuffman.BitReverse(code);
00157 if (bits <= 9) {
00158 do {
00159 tree[revcode] = (short) ((i << 4) | bits);
00160 revcode += 1 << bits;
00161 } while (revcode < 512);
00162 } else {
00163 int subTree = tree[revcode & 511];
00164 int treeLen = 1 << (subTree & 15);
00165 subTree = -(subTree >> 4);
00166 do {
00167 tree[subTree | (revcode >> 9)] = (short) ((i << 4) | bits);
00168 revcode += 1 << bits;
00169 } while (revcode < treeLen);
00170 }
00171 nextCode[bits] = code + (1 << (16 - bits));
00172 }
00173
00174 }
00175
00186 public int GetSymbol(StreamManipulator input)
00187 {
00188 int lookahead, symbol;
00189 if ((lookahead = input.PeekBits(9)) >= 0) {
00190 if ((symbol = tree[lookahead]) >= 0) {
00191 input.DropBits(symbol & 15);
00192 return symbol >> 4;
00193 }
00194 int subtree = -(symbol >> 4);
00195 int bitlen = symbol & 15;
00196 if ((lookahead = input.PeekBits(bitlen)) >= 0) {
00197 symbol = tree[subtree | (lookahead >> 9)];
00198 input.DropBits(symbol & 15);
00199 return symbol >> 4;
00200 } else {
00201 int bits = input.AvailableBits;
00202 lookahead = input.PeekBits(bits);
00203 symbol = tree[subtree | (lookahead >> 9)];
00204 if ((symbol & 15) <= bits) {
00205 input.DropBits(symbol & 15);
00206 return symbol >> 4;
00207 } else {
00208 return -1;
00209 }
00210 }
00211 } else {
00212 int bits = input.AvailableBits;
00213 lookahead = input.PeekBits(bits);
00214 symbol = tree[lookahead];
00215 if (symbol >= 0 && (symbol & 15) <= bits) {
00216 input.DropBits(symbol & 15);
00217 return symbol >> 4;
00218 } else {
00219 return -1;
00220 }
00221 }
00222 }
00223 }
00224 }
00225