1 //
2 // © Copyright Henrik Ravn 2004
3 //
4 // Use, modification and distribution are subject to the Boost Software License, Version 1.0.
5 // (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 //
7
8 using System;
9 using System.IO;
10 using System.Runtime.InteropServices;
11
12 namespace DotZLib
13 {
14 /// <summary>
15 /// Implements a compressed <see cref="Stream"/>, in GZip (.gz) format.
16 /// </summary>
17 public class GZipStream : Stream, IDisposable
18 {
19 #region Dll Imports
20 [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl, CharSet=CharSet.Ansi)]
21 private static extern IntPtr gzopen(string name, string mode);
22
23 [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
24 private static extern int gzclose(IntPtr gzFile);
25
26 [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
27 private static extern int gzwrite(IntPtr gzFile, int data, int length);
28
29 [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
30 private static extern int gzread(IntPtr gzFile, int data, int length);
31
32 [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
33 private static extern int gzgetc(IntPtr gzFile);
34
35 [DllImport("ZLIB1.dll", CallingConvention=CallingConvention.Cdecl)]
36 private static extern int gzputc(IntPtr gzFile, int c);
37
38 #endregion
39
40 #region Private data
41 private IntPtr _gzFile;
42 private bool _isDisposed = false;
43 private bool _isWriting;
44 #endregion
45
46 #region Constructors
47 /// <summary>
48 /// Creates a new file as a writeable GZipStream
49 /// </summary>
50 /// <param name="fileName">The name of the compressed file to create</param>
51 /// <param name="level">The compression level to use when adding data</param>
52 /// <exception cref="ZLibException">If an error occurred in the internal zlib function</exception>
53 public GZipStream(string fileName, CompressLevel level)
54 {
55 _isWriting = true;
56 _gzFile = gzopen(fileName, String.Format("wb{0}", (int)level));
57 if (_gzFile == IntPtr.Zero)
58 throw new ZLibException(-1, "Could not open " + fileName);
59 }
60
61 /// <summary>
62 /// Opens an existing file as a readable GZipStream
63 /// </summary>
64 /// <param name="fileName">The name of the file to open</param>
65 /// <exception cref="ZLibException">If an error occurred in the internal zlib function</exception>
66 public GZipStream(string fileName)
67 {
68 _isWriting = false;
69 _gzFile = gzopen(fileName, "rb");
70 if (_gzFile == IntPtr.Zero)
71 throw new ZLibException(-1, "Could not open " + fileName);
72
73 }
74 #endregion
75
76 #region Access properties
77 /// <summary>
78 /// Returns true of this stream can be read from, false otherwise
79 /// </summary>
80 public override bool CanRead
81 {
82 get
83 {
84 return !_isWriting;
85 }
86 }
87
88
89 /// <summary>
90 /// Returns false.
91 /// </summary>
92 public override bool CanSeek
93 {
94 get
95 {
96 return false;
97 }
98 }
99
100 /// <summary>
101 /// Returns true if this tsream is writeable, false otherwise
102 /// </summary>
103 public override bool CanWrite
104 {
105 get
106 {
107 return _isWriting;
108 }
109 }
110 #endregion
111
112 #region Destructor & IDispose stuff
113
114 /// <summary>
115 /// Destroys this instance
116 /// </summary>
117 ~GZipStream()
118 {
119 cleanUp(false);
120 }
121
122 /// <summary>
123 /// Closes the external file handle
124 /// </summary>
125 public void Dispose()
126 {
127 cleanUp(true);
128 }
129
130 // Does the actual closing of the file handle.
131 private void cleanUp(bool isDisposing)
132 {
133 if (!_isDisposed)
134 {
135 gzclose(_gzFile);
136 _isDisposed = true;
137 }
138 }
139 #endregion
140
141 #region Basic reading and writing
142 /// <summary>
143 /// Attempts to read a number of bytes from the stream.
144 /// </summary>
145 /// <param name="buffer">The destination data buffer</param>
146 /// <param name="offset">The index of the first destination byte in <c>buffer</c></param>
147 /// <param name="count">The number of bytes requested</param>
148 /// <returns>The number of bytes read</returns>
149 /// <exception cref="ArgumentNullException">If <c>buffer</c> is null</exception>
150 /// <exception cref="ArgumentOutOfRangeException">If <c>count</c> or <c>offset</c> are negative</exception>
151 /// <exception cref="ArgumentException">If <c>offset</c> + <c>count</c> is > buffer.Length</exception>
152 /// <exception cref="NotSupportedException">If this stream is not readable.</exception>
153 /// <exception cref="ObjectDisposedException">If this stream has been disposed.</exception>
154 public override int Read(byte[] buffer, int offset, int count)
155 {
156 if (!CanRead) throw new NotSupportedException();
157 if (buffer == null) throw new ArgumentNullException();
158 if (offset < 0 || count < 0) throw new ArgumentOutOfRangeException();
159 if ((offset+count) > buffer.Length) throw new ArgumentException();
160 if (_isDisposed) throw new ObjectDisposedException("GZipStream");
161
162 GCHandle h = GCHandle.Alloc(buffer, GCHandleType.Pinned);
163 int result;
164 try
165 {
166 result = gzread(_gzFile, h.AddrOfPinnedObject().ToInt32() + offset, count);
167 if (result < 0)
168 throw new IOException();
169 }
170 finally
171 {
172 h.Free();
173 }
174 return result;
175 }
176
177 /// <summary>
178 /// Attempts to read a single byte from the stream.
179 /// </summary>
180 /// <returns>The byte that was read, or -1 in case of error or End-Of-File</returns>
181 public override int ReadByte()
182 {
183 if (!CanRead) throw new NotSupportedException();
184 if (_isDisposed) throw new ObjectDisposedException("GZipStream");
185 return gzgetc(_gzFile);
186 }
187
188 /// <summary>
189 /// Writes a number of bytes to the stream
190 /// </summary>
191 /// <param name="buffer"></param>
192 /// <param name="offset"></param>
193 /// <param name="count"></param>
194 /// <exception cref="ArgumentNullException">If <c>buffer</c> is null</exception>
195 /// <exception cref="ArgumentOutOfRangeException">If <c>count</c> or <c>offset</c> are negative</exception>
196 /// <exception cref="ArgumentException">If <c>offset</c> + <c>count</c> is > buffer.Length</exception>
197 /// <exception cref="NotSupportedException">If this stream is not writeable.</exception>
198 /// <exception cref="ObjectDisposedException">If this stream has been disposed.</exception>
199 public override void Write(byte[] buffer, int offset, int count)
200 {
201 if (!CanWrite) throw new NotSupportedException();
202 if (buffer == null) throw new ArgumentNullException();
203 if (offset < 0 || count < 0) throw new ArgumentOutOfRangeException();
204 if ((offset+count) > buffer.Length) throw new ArgumentException();
205 if (_isDisposed) throw new ObjectDisposedException("GZipStream");
206
207 GCHandle h = GCHandle.Alloc(buffer, GCHandleType.Pinned);
208 try
209 {
210 int result = gzwrite(_gzFile, h.AddrOfPinnedObject().ToInt32() + offset, count);
211 if (result < 0)
212 throw new IOException();
213 }
214 finally
215 {
216 h.Free();
217 }
218 }
219
220 /// <summary>
221 /// Writes a single byte to the stream
222 /// </summary>
223 /// <param name="value">The byte to add to the stream.</param>
224 /// <exception cref="NotSupportedException">If this stream is not writeable.</exception>
225 /// <exception cref="ObjectDisposedException">If this stream has been disposed.</exception>
226 public override void WriteByte(byte value)
227 {
228 if (!CanWrite) throw new NotSupportedException();
229 if (_isDisposed) throw new ObjectDisposedException("GZipStream");
230
231 int result = gzputc(_gzFile, (int)value);
232 if (result < 0)
233 throw new IOException();
234 }
235 #endregion
236
237 #region Position & length stuff
238 /// <summary>
239 /// Not supported.
240 /// </summary>
241 /// <param name="value"></param>
242 /// <exception cref="NotSupportedException">Always thrown</exception>
243 public override void SetLength(long value)
244 {
245 throw new NotSupportedException();
246 }
247
248 /// <summary>
249 /// Not suppported.
250 /// </summary>
251 /// <param name="offset"></param>
252 /// <param name="origin"></param>
253 /// <returns></returns>
254 /// <exception cref="NotSupportedException">Always thrown</exception>
255 public override long Seek(long offset, SeekOrigin origin)
256 {
257 throw new NotSupportedException();
258 }
259
260 /// <summary>
261 /// Flushes the <c>GZipStream</c>.
262 /// </summary>
263 /// <remarks>In this implementation, this method does nothing. This is because excessive
264 /// flushing may degrade the achievable compression rates.</remarks>
265 public override void Flush()
266 {
267 // left empty on purpose
268 }
269
270 /// <summary>
271 /// Gets/sets the current position in the <c>GZipStream</c>. Not suppported.
272 /// </summary>
273 /// <remarks>In this implementation this property is not supported</remarks>
274 /// <exception cref="NotSupportedException">Always thrown</exception>
275 public override long Position
276 {
277 get
278 {
279 throw new NotSupportedException();
280 }
281 set
282 {
283 throw new NotSupportedException();
284 }
285 }
286
287 /// <summary>
288 /// Gets the size of the stream. Not suppported.
289 /// </summary>
290 /// <remarks>In this implementation this property is not supported</remarks>
291 /// <exception cref="NotSupportedException">Always thrown</exception>
292 public override long Length
293 {
294 get
295 {
296 throw new NotSupportedException();
297 }
298 }
299 #endregion
300 }
301 }