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.Runtime.InteropServices;
10
11 namespace DotZLib
12 {
13 /// <summary>
14 /// Implements the common functionality needed for all <see cref="Codec"/>s
15 /// </summary>
16 public abstract class CodecBase : Codec, IDisposable
17 {
18
19 #region Data members
20
21 /// <summary>
22 /// Instance of the internal zlib buffer structure that is
23 /// passed to all functions in the zlib dll
24 /// </summary>
25 internal ZStream _ztream = new ZStream();
26
27 /// <summary>
28 /// True if the object instance has been disposed, false otherwise
29 /// </summary>
30 protected bool _isDisposed = false;
31
32 /// <summary>
33 /// The size of the internal buffers
34 /// </summary>
35 protected const int kBufferSize = 16384;
36
37 private byte[] _outBuffer = new byte[kBufferSize];
38 private byte[] _inBuffer = new byte[kBufferSize];
39
40 private GCHandle _hInput;
41 private GCHandle _hOutput;
42
43 private uint _checksum = 0;
44
45 #endregion
46
47 /// <summary>
48 /// Initializes a new instance of the <c>CodeBase</c> class.
49 /// </summary>
50 public CodecBase()
51 {
52 try
53 {
54 _hInput = GCHandle.Alloc(_inBuffer, GCHandleType.Pinned);
55 _hOutput = GCHandle.Alloc(_outBuffer, GCHandleType.Pinned);
56 }
57 catch (Exception)
58 {
59 CleanUp(false);
60 throw;
61 }
62 }
63
64
65 #region Codec Members
66
67 /// <summary>
68 /// Occurs when more processed data are available.
69 /// </summary>
70 public event DataAvailableHandler DataAvailable;
71
72 /// <summary>
73 /// Fires the <see cref="DataAvailable"/> event
74 /// </summary>
75 protected void OnDataAvailable()
76 {
77 if (_ztream.total_out > 0)
78 {
79 if (DataAvailable != null)
80 DataAvailable( _outBuffer, 0, (int)_ztream.total_out);
81 resetOutput();
82 }
83 }
84
85 /// <summary>
86 /// Adds more data to the codec to be processed.
87 /// </summary>
88 /// <param name="data">Byte array containing the data to be added to the codec</param>
89 /// <remarks>Adding data may, or may not, raise the <c>DataAvailable</c> event</remarks>
90 public void Add(byte[] data)
91 {
92 Add(data,0,data.Length);
93 }
94
95 /// <summary>
96 /// Adds more data to the codec to be processed.
97 /// </summary>
98 /// <param name="data">Byte array containing the data to be added to the codec</param>
99 /// <param name="offset">The index of the first byte to add from <c>data</c></param>
100 /// <param name="count">The number of bytes to add</param>
101 /// <remarks>Adding data may, or may not, raise the <c>DataAvailable</c> event</remarks>
102 /// <remarks>This must be implemented by a derived class</remarks>
103 public abstract void Add(byte[] data, int offset, int count);
104
105 /// <summary>
106 /// Finishes up any pending data that needs to be processed and handled.
107 /// </summary>
108 /// <remarks>This must be implemented by a derived class</remarks>
109 public abstract void Finish();
110
111 /// <summary>
112 /// Gets the checksum of the data that has been added so far
113 /// </summary>
114 public uint Checksum { get { return _checksum; } }
115
116 #endregion
117
118 #region Destructor & IDisposable stuff
119
120 /// <summary>
121 /// Destroys this instance
122 /// </summary>
123 ~CodecBase()
124 {
125 CleanUp(false);
126 }
127
128 /// <summary>
129 /// Releases any unmanaged resources and calls the <see cref="CleanUp()"/> method of the derived class
130 /// </summary>
131 public void Dispose()
132 {
133 CleanUp(true);
134 }
135
136 /// <summary>
137 /// Performs any codec specific cleanup
138 /// </summary>
139 /// <remarks>This must be implemented by a derived class</remarks>
140 protected abstract void CleanUp();
141
142 // performs the release of the handles and calls the dereived CleanUp()
143 private void CleanUp(bool isDisposing)
144 {
145 if (!_isDisposed)
146 {
147 CleanUp();
148 if (_hInput.IsAllocated)
149 _hInput.Free();
150 if (_hOutput.IsAllocated)
151 _hOutput.Free();
152
153 _isDisposed = true;
154 }
155 }
156
157
158 #endregion
159
160 #region Helper methods
161
162 /// <summary>
163 /// Copies a number of bytes to the internal codec buffer - ready for proccesing
164 /// </summary>
165 /// <param name="data">The byte array that contains the data to copy</param>
166 /// <param name="startIndex">The index of the first byte to copy</param>
167 /// <param name="count">The number of bytes to copy from <c>data</c></param>
168 protected void copyInput(byte[] data, int startIndex, int count)
169 {
170 Array.Copy(data, startIndex, _inBuffer,0, count);
171 _ztream.next_in = _hInput.AddrOfPinnedObject();
172 _ztream.total_in = 0;
173 _ztream.avail_in = (uint)count;
174
175 }
176
177 /// <summary>
178 /// Resets the internal output buffers to a known state - ready for processing
179 /// </summary>
180 protected void resetOutput()
181 {
182 _ztream.total_out = 0;
183 _ztream.avail_out = kBufferSize;
184 _ztream.next_out = _hOutput.AddrOfPinnedObject();
185 }
186
187 /// <summary>
188 /// Updates the running checksum property
189 /// </summary>
190 /// <param name="newSum">The new checksum value</param>
191 protected void setChecksum(uint newSum)
192 {
193 _checksum = newSum;
194 }
195 #endregion
196
197 }
198 }