当前文件路径：x3blogAccessBuild80707/SharpZipLib/BZip2/BZip2InputStream.cs 
1
// BZip2InputStream.cs
2//
3// Copyright (C) 2001 Mike Krueger
4//
5// This program is free software; you can redistribute it and/or
6// modify it under the terms of the GNU General Public License
7// as published by the Free Software Foundation; either version 2
8// of the License, or (at your option) any later version.
9//
10// This program is distributed in the hope that it will be useful,
11// but WITHOUT ANY WARRANTY; without even the implied warranty of
12// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13// GNU General Public License for more details.
14//
15// You should have received a copy of the GNU General Public License
16// along with this program; if not, write to the Free Software
17// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18//
19// Linking this library statically or dynamically with other modules is
20// making a combined work based on this library. Thus, the terms and
21// conditions of the GNU General Public License cover the whole
22// combination.
23//
24// As a special exception, the copyright holders of this library give you
25// permission to link this library with independent modules to produce an
26// executable, regardless of the license terms of these independent
27// modules, and to copy and distribute the resulting executable under
28// terms of your choice, provided that you also meet, for each linked
29// independent module, the terms and conditions of the license of that
30// module. An independent module is a module which is not derived from
31// or based on this library. If you modify this library, you may extend
32// this exception to your version of the library, but you are not
33// obligated to do so. If you do not wish to do so, delete this
34// exception statement from your version.
35
36using System;
37using System.IO;
38
39using ICSharpCode.SharpZipLib.Checksums;
40
41namespace ICSharpCode.SharpZipLib.BZip2
42
...{
43
44
/**//// <summary>
45 /// An input stream that decompresses files in the BZip2 format
46
/// </summary>
47 public class BZip2InputStream : Stream
48 ...{
49 /**//// <summary>
50 /// Gets a value indicating if the stream supports reading
51 /// </summary>
52 public override bool CanRead ...{
53 get ...{
54 return baseStream.CanRead;
55 }
56 }
57
58 /**//// <summary>
59 /// Gets a value indicating whether the current stream supports seeking.
60 /// </summary>
61 public override bool CanSeek ...{
62 get ...{
63 return baseStream.CanSeek;
64 }
65 }
66
67 /**//// <summary>
68 /// Gets a value indicating whether the current stream supports writing.
69 /// This property always returns false
70 /// </summary>
71 public override bool CanWrite ...{
72 get ...{
73 return false;
74 }
75 }
76
77 /**//// <summary>
78 /// Gets the length in bytes of the stream.
79 /// </summary>
80 public override long Length ...{
81 get ...{
82 return baseStream.Length;
83 }
84 }
85
86 /**//// <summary>
87 /// Gets or sets the streams position.
88 /// Setting the position is not supported and will throw a NotSupportException
89 /// </summary>
90 /// <exception cref="NotSupportedException">Any attempt to set the position</exception>
91 public override long Position ...{
92 get ...{
93 return baseStream.Position;
94 }
95 set ...{
96 throw new NotSupportedException("BZip2InputStream position cannot be set");
97 }
98 }
99
100 /**//// <summary>
101 /// Flushes the stream.
102 /// </summary>
103 public override void Flush()
104 ...{
105 if (baseStream != null) ...{
106 baseStream.Flush();
107 }
108 }
109
110 /**//// <summary>
111 /// Set the streams position. This operation is not supported and will throw a NotSupportedException
112 /// </summary>
113 /// <exception cref="NotSupportedException">Any access</exception>
114 public override long Seek(long offset, SeekOrigin origin)
115 ...{
116 throw new NotSupportedException("BZip2InputStream Seek not supported");
117 }
118
119 /**//// <summary>
120 /// Sets the length of this stream to the given value.
121 /// This operation is not supported and will throw a NotSupportedExceptionortedException
122 /// </summary>
123 /// <exception cref="NotSupportedException">Any access</exception>
124 public override void SetLength(long val)
125 ...{
126 throw new NotSupportedException("BZip2InputStream SetLength not supported");
127 }
128
129 /**//// <summary>
130 /// Writes a block of bytes to this stream using data from a buffer.
131 /// This operation is not supported and will throw a NotSupportedException
132 /// </summary>
133 /// <exception cref="NotSupportedException">Any access</exception>
134 public override void Write(byte[] array, int offset, int count)
135 ...{
136 throw new NotSupportedException("BZip2InputStream Write not supported");
137 }
138
139 /**//// <summary>
140 /// Writes a byte to the current position in the file stream.
141 /// This operation is not supported and will throw a NotSupportedException
142 /// </summary>
143 /// <exception cref="NotSupportedException">Any access</exception>
144 public override void WriteByte(byte val)
145 ...{
146 throw new NotSupportedException("BZip2InputStream WriteByte not supported");
147 }
148
149 /**//// <summary>
150 /// Read a sequence of bytes and advances the read position by one byte.
151 /// </summary>
152 /// <param name="b">Array of bytes to store values in</param>
153 /// <param name="offset">Offset in array to begin storing data</param>
154 /// <param name="count">The maximum number of bytes to read</param>
155 /// <returns>The total number of bytes read into the buffer. This might be less
156 /// than the number of bytes requested if that number of bytes are not
157 /// currently available or zero if the end of the stream is reached.
158 /// </returns>
159 public override int Read(byte[] b, int offset, int count)
160 ...{
161 for (int i = 0; i < count; ++i) ...{
162 int rb = ReadByte();
163 if (rb == -1) ...{
164 return i;
165 }
166 b[offset + i] = (byte)rb;
167 }
168 return count;
169 }
170
171 /**//// <summary>
172 /// Closes the stream, releasing any associated resources.
173 /// </summary>
174 public override void Close()
175 ...{
176 if (baseStream != null) ...{
177 baseStream.Close();
178 }
179 }
180
181 void MakeMaps()
182 ...{
183 nInUse = 0;
184 for (int i = 0; i < 256; ++i) ...{
185 if (inUse[i]) ...{
186 seqToUnseq[nInUse] = (byte)i;
187 unseqToSeq[i] = (byte)nInUse;
188 nInUse++;
189 }
190 }
191 }
192
193 /**//*--
194 index of the last char in the block, so
195 the block size == last + 1.
196 --*/
197 int last;
198
199 /**//*--
200 index in zptr[] of original string after sorting.
201 --*/
202 int origPtr;
203
204 /**//*--
205 always: in the range 0 .. 9.
206 The current block size is 100000 * this number.
207 --*/
208 int blockSize100k;
209
210 bool blockRandomised;
211
212 int bsBuff;
213 int bsLive;
214 IChecksum mCrc = new StrangeCRC();
215
216 bool[] inUse = new bool[256];
217 int nInUse;
218
219 byte[] seqToUnseq = new byte[256];
220 byte[] unseqToSeq = new byte[256];
221
222 byte[] selector = new byte[BZip2Constants.MAX_SELECTORS];
223 byte[] selectorMtf = new byte[BZip2Constants.MAX_SELECTORS];
224
225 int[] tt;
226 byte[] ll8;
227
228 /**//*--
229 freq table collected to save a pass over the data
230 during decompression.
231 --*/
232 int[] unzftab = new int[256];
233
234 int[][] limit = new int[BZip2Constants.N_GROUPS][];
235 int[][] baseArray = new int[BZip2Constants.N_GROUPS][];
236 int[][] perm = new int[BZip2Constants.N_GROUPS][];
237 int[] minLens = new int[BZip2Constants.N_GROUPS];
238
239 Stream baseStream;
240 bool streamEnd = false;
241
242 int currentChar = -1;
243
244 const int START_BLOCK_STATE = 1;
245 const int RAND_PART_A_STATE = 2;
246 const int RAND_PART_B_STATE = 3;
247 const int RAND_PART_C_STATE = 4;
248 const int NO_RAND_PART_A_STATE = 5;
249 const int NO_RAND_PART_B_STATE = 6;
250 const int NO_RAND_PART_C_STATE = 7;
251
252 int currentState = START_BLOCK_STATE;
253
254 int storedBlockCRC, storedCombinedCRC;
255 int computedBlockCRC;
256 uint computedCombinedCRC;
257
258 int count, chPrev, ch2;
259 int tPos;
260 int rNToGo = 0;
261 int rTPos = 0;
262 int i2, j2;
263 byte z;
264
265 /**//// <summary>
266 /// Construct instance for reading from stream
267 /// </summary>
268 /// <param name="stream">Data source</param>
269 public BZip2InputStream(Stream stream)
270 ...{
271 // init arrays
272 for (int i = 0; i < BZip2Constants.N_GROUPS; ++i) ...{
273 limit[i] = new int[BZip2Constants.MAX_ALPHA_SIZE];
274 baseArray[i] = new int[BZip2Constants.MAX_ALPHA_SIZE];
275 perm[i] = new int[BZip2Constants.MAX_ALPHA_SIZE];
276 }
277
278 ll8 = null;
279 tt = null;
280 BsSetStream(stream);
281 Initialize();
282 InitBlock();
283 SetupBlock();
284 }
285
286
