File: StreamManipulator.cs

package info (click to toggle)
mono 4.6.2.7+dfsg-1
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 778,148 kB
  • ctags: 914,052
  • sloc: cs: 5,779,509; xml: 2,773,713; ansic: 432,645; sh: 14,749; makefile: 12,361; perl: 2,488; python: 1,434; cpp: 849; asm: 531; sql: 95; sed: 16; php: 1
file content (270 lines) | stat: -rw-r--r-- 8,238 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
// StreamManipulator.cs
//
// Copyright (C) 2001 Mike Krueger
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
// 
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module.  An independent module is a module which is not derived from
// or based on this library.  If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so.  If you do not wish to do so, delete this
// exception statement from your version.

using System;

namespace ICSharpCode.SharpZipLib.Zip.Compression.Streams 
{
	
	/// <summary>
	/// This class allows us to retrieve a specified number of bits from
	/// the input buffer, as well as copy big byte blocks.
	///
	/// It uses an int buffer to store up to 31 bits for direct
	/// manipulation.  This guarantees that we can get at least 16 bits,
	/// but we only need at most 15, so this is all safe.
	///
	/// There are some optimizations in this class, for example, you must
	/// never peek more than 8 bits more than needed, and you must first
	/// peek bits before you may drop them.  This is not a general purpose
	/// class but optimized for the behaviour of the Inflater.
	///
	/// authors of the original java version : John Leuner, Jochen Hoenicke
	/// </summary>
	public class StreamManipulator
	{
		private byte[] window;
		private int window_start = 0;
		private int window_end = 0;
		
		private uint buffer = 0;
		private int bits_in_buffer = 0;
		
		/// <summary>
		/// Get the next n bits but don't increase input pointer.  n must be
		/// less or equal 16 and if this call succeeds, you must drop
		/// at least n - 8 bits in the next call.
		/// </summary>
		/// <returns>
		/// the value of the bits, or -1 if not enough bits available.  */
		/// </returns>
		public int PeekBits(int n)
		{
			if (bits_in_buffer < n) {
				if (window_start == window_end) {
					return -1; // ok
				}
				buffer |= (uint)((window[window_start++] & 0xff |
				                 (window[window_start++] & 0xff) << 8) << bits_in_buffer);
				bits_in_buffer += 16;
			}
			return (int)(buffer & ((1 << n) - 1));
		}
		
		/// <summary>
		/// Drops the next n bits from the input.  You should have called PeekBits
		/// with a bigger or equal n before, to make sure that enough bits are in
		/// the bit buffer.
		/// </summary>
		public void DropBits(int n)
		{
			buffer >>= n;
			bits_in_buffer -= n;
		}
		
		/// <summary>
		/// Gets the next n bits and increases input pointer.  This is equivalent
		/// to PeekBits followed by dropBits, except for correct error handling.
		/// </summary>
		/// <returns>
		/// the value of the bits, or -1 if not enough bits available.
		/// </returns>
		public int GetBits(int n)
		{
			int bits = PeekBits(n);
			if (bits >= 0) {
				DropBits(n);
			}
			return bits;
		}
		
		/// <summary>
		/// Gets the number of bits available in the bit buffer.  This must be
		/// only called when a previous PeekBits() returned -1.
		/// </summary>
		/// <returns>
		/// the number of bits available.
		/// </returns>
		public int AvailableBits {
			get {
				return bits_in_buffer;
			}
		}
		
		/// <summary>
		/// Gets the number of bytes available.
		/// </summary>
		/// <returns>
		/// The number of bytes available.
		/// </returns>
		public int AvailableBytes {
			get {
				return window_end - window_start + (bits_in_buffer >> 3);
			}
		}
		
		/// <summary>
		/// Skips to the next byte boundary.
		/// </summary>
		public void SkipToByteBoundary()
		{
			buffer >>= (bits_in_buffer & 7);
			bits_in_buffer &= ~7;
		}

		/// <summary>
		/// Returns true when SetInput can be called
		/// </summary>
		public bool IsNeedingInput {
			get {
				return window_start == window_end;
			}
		}
		
		/// <summary>
		/// Copies length bytes from input buffer to output buffer starting
		/// at output[offset].  You have to make sure, that the buffer is
		/// byte aligned.  If not enough bytes are available, copies fewer
		/// bytes.
		/// </summary>
		/// <param name="output">
		/// The buffer to copy bytes to.
		/// </param>
		/// <param name="offset">
		/// The offset in the buffer at which copying starts
		/// </param>
		/// <param name="length">
		/// The length to copy, 0 is allowed.
		/// </param>
		/// <returns>
		/// The number of bytes copied, 0 if no bytes were available.
		/// </returns>
		/// <exception cref="ArgumentOutOfRangeException">
		/// Length is less than zero
		/// </exception>
		/// <exception cref="InvalidOperationException">
		/// Bit buffer isnt byte aligned
		/// </exception>
		public int CopyBytes(byte[] output, int offset, int length)
		{
			if (length < 0) {
				throw new ArgumentOutOfRangeException("length");
			}
			if ((bits_in_buffer & 7) != 0) {
				/* bits_in_buffer may only be 0 or a multiple of 8 */
				throw new InvalidOperationException("Bit buffer is not byte aligned!");
			}
			
			int count = 0;
			while (bits_in_buffer > 0 && length > 0) {
				output[offset++] = (byte) buffer;
				buffer >>= 8;
				bits_in_buffer -= 8;
				length--;
				count++;
			}
			
			if (length == 0) {
				return count;
			}
			
			int avail = window_end - window_start;
			if (length > avail) {
				length = avail;
			}
			System.Array.Copy(window, window_start, output, offset, length);
			window_start += length;
			
			if (((window_start - window_end) & 1) != 0) {
				/* We always want an even number of bytes in input, see peekBits */
				buffer = (uint)(window[window_start++] & 0xff);
				bits_in_buffer = 8;
			}
			return count + length;
		}
		
		/// <summary>
		/// Constructs a default StreamManipulator with all buffers empty
		/// </summary>
		public StreamManipulator()
		{
		}

		
		/// <summary>
		/// resets state and empties internal buffers
		/// </summary>
		public void Reset()
		{
			buffer = (uint)(window_start = window_end = bits_in_buffer = 0);
		}

		/// <summary>
		/// Add more input for consumption.
		/// Only call when IsNeedingInput returns true
		/// </summary>
		/// <param name="buf">data to be input</param>
		/// <param name="off">offset of first byte of input</param>
		/// <param name="len">length of input</param>
		public void SetInput(byte[] buf, int off, int len)
		{
			if (window_start < window_end) {
				throw new InvalidOperationException("Old input was not completely processed");
			}
			
			int end = off + len;
			
			/* We want to throw an ArrayIndexOutOfBoundsException early.  The
			* check is very tricky: it also handles integer wrap around.
			*/
			if (0 > off || off > end || end > buf.Length) {
				throw new ArgumentOutOfRangeException();
			}
			
			if ((len & 1) != 0) {
				/* We always want an even number of bytes in input, see peekBits */
				buffer |= (uint)((buf[off++] & 0xff) << bits_in_buffer);
				bits_in_buffer += 8;
			}
			
			window = buf;
			window_start = off;
			window_end = end;
		}
	}
}