#### /Utilities/Compression/Checksums/Crc32.cs

#
C# | 298 lines | 176 code | 31 blank | 91 comment | 7 complexity | 761ea8406bed06a46eff72c34bc6b6e1 MD5 | raw file
```  1using System;
2using System.IO;
3
4namespace Delta.Utilities.Compression.Checksums
5{
6	/// <summary>
7	/// Crc32 - Computes CRC32 data checksum of a data stream. Generate
8	/// a table for a byte-wise 32-bit CRC calculation on the polynomial:
9	/// x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.
10	///
11	/// Polynomials over GF(2) are represented in binary, one bit per
12	/// coefficient, with the lowest powers in the most significant bit.
13	/// Then adding polynomials is just exclusive-or, and multiplying a
14	/// polynomial by x is a right shift by one. If we call the above polynomial
15	/// p, and represent a byte as the polynomial q, also with the lowest power
16	/// in the most significant bit (so the byte 0xb1 is the polynomial
17	/// x^7+x^3+x+1), then the CRC is (q*x^32) mod p, where a mod b means the
18	/// remainder after dividing a by b.
19	///
20	/// This calculation is done using the shift-register method of multiplying
21	/// and taking the remainder.  The register is initialized to zero, and for
22	/// each incoming bit, x^32 is added mod p to the register if the bit is a
23	/// one (where x^32 mod p is p+x^32 = x^26+...+1), and the register is
24	/// multiplied mod p by x (which is shifting right by one and adding
25	/// x^32 mod p if the bit shifted out is a one).  We start with the highest
26	/// power (least significant bit) of q and repeat for all eight bits of q.
27	///
28	/// The table is simply the CRC of all possible eight bit values. This is all
29	/// the information needed to generate CRC'str on data a byte at a time for
30	/// all combinations of CRC register values and incoming bytes.
31	/// </summary>
32	public sealed class Crc32
33	{
34		#region Constants
35		/// <summary>
36		/// Crc seed
37		/// </summary>
38		private const uint CrcSeed = 0xFFFFFFFF;
39
40		/// <summary>
41		/// Crc table
42		/// </summary>
43		/// <returns>Uint []</returns>
44		private static readonly uint[] CrcTable = new uint[]
45		{
46			0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
47			0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
48			0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
49			0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
51			0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
52			0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
53			0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
54			0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
55			0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
56			0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
57			0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
58			0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
59			0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
60			0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
61			0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
62			0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
63			0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
64			0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
65			0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
66			0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
67			0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
68			0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
69			0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
70			0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
71			0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
72			0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
73			0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
74			0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
75			0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
76			0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
77			0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
78			0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
79			0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
80			0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
81			0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
82			0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
83			0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
84			0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
85			0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
86			0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
87			0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
88			0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
89			0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
90			0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
91			0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
92			0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
93			0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
94			0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
95			0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
96			0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
97			0x2D02EF8D
98		};
99		#endregion
100
101		#region ComputeCrcValue (Static)
102		/// <summary>
103		/// Compute crc value
104		/// </summary>
105		/// <param name="buffer">Buffer</param>
106		/// <returns>Long</returns>
107		public static long ComputeCrcValue(byte[] buffer)
108		{
109			Crc32 crc = new Crc32();
110			crc.Update(buffer);
111			return crc.Value;
112		}
113
114		// ComputeCrcValue(buffer)
115
116		/// <summary>
117		/// Compute crc value
118		/// </summary>
119		/// <param name="stream">Stream</param>
120		/// <returns>Long</returns>
121		public static long ComputeCrcValue(Stream stream)
122		{
123			// Make sure the stream is good to go.
124			if (stream.CanRead == false ||
125			    stream.CanSeek == false)
126			{
127				throw new NotSupportedException(
128					"Can't calculated checksum of a stream that does not support " +
130			}
131
132			// Remember old stream position
133			long oldPosition = stream.Position;
134
135			// Get all data
136			byte[] buffer = new byte[stream.Length];
137			stream.Seek(0, SeekOrigin.Begin);
139
140			// Restore old position
141			stream.Position = oldPosition;
142
143			// Compute and return checksum
144			return ComputeCrcValue(buffer);
145		}
146		#endregion
147
148		#region Value (Public)
149		/// <summary>
150		/// Returns the CRC32 data checksum computed so far.
151		/// </summary>
152		public long Value
153		{
154			get
155			{
156				return crc;
157			} // get
158			set
159			{
160				crc = (uint)value;
161			} // set
162		}
163		#endregion
164
165		#region Private
166
167		#region crc (Private)
168		/// <summary>
169		/// The crc data checksum so far.
170		/// </summary>
171		private uint crc;
172		#endregion
173
174		#endregion
175
176		#region Reset (Public)
177		/// <summary>
178		/// Resets the CRC32 data checksum as if no update was ever called.
179		/// </summary>
180		public void Reset()
181		{
182			crc = 0;
183		}
184		#endregion
185
186		#region Update (Public)
187		/// <summary>
188		/// Updates the checksum with the int value.
189		/// </summary>
190		/// <param name="value">Byte is taken as the lower 8 bits of value</param>
191		public void Update(int value)
192		{
193			crc ^= CrcSeed;
194			crc = CrcTable[(crc ^ value) & 0xFF] ^ (crc >> 8);
195			crc ^= CrcSeed;
196		}
197
198		// Update(value)
199
200		/// <summary>
201		/// Updates the checksum with the bytes taken from the array.
202		/// </summary>
203		/// <param name="buffer">
204		/// buffer an array of bytes
205		/// </param>
206		public void Update(byte[] buffer)
207		{
208			Update(buffer, 0, buffer.Length);
209		}
210
211		// Update(buffer)
212
213		/// <summary>
214		/// Adds the byte array to the data checksum.
215		/// </summary>
216		/// <param name="buffer">Buffer which contains the data</param>
217		/// <param name="offset">Offset in the buffer where the data starts</param>
218		/// <param name="count">Length of the data</param>
219		public void Update(byte[] buffer, int offset, int count)
220		{
221			if (buffer == null)
222			{
223				throw new ArgumentNullException("buffer");
224			} // if (buf)
225			if (offset < 0 ||
226			    count < 0 ||
227			    offset + count > buffer.Length)
228			{
229				throw new ArgumentOutOfRangeException();
230			} // if (off)
231
232			crc ^= CrcSeed;
233
234			while (--count >= 0)
235			{
236				crc = CrcTable[(crc ^ buffer[offset++]) & 0xFF] ^ (crc >> 8);
237			} // while (--len)
238
239			crc ^= CrcSeed;
240		}
241		#endregion
242
243		#region Methods (Private)
244
245		#region ComputeCrc32
246		/// <summary>
247		/// Compute crc 32
248		/// </summary>
249		/// <param name="oldCrc">Old crc</param>
250		/// <param name="value">Value</param>
251		/// <returns>Uint</returns>
252		internal static uint ComputeCrc32(uint oldCrc, byte value)
253		{
254			return (CrcTable[(oldCrc ^ value) & 0xFF] ^ (oldCrc >> 8));
255		}
256		#endregion
257
258		#endregion
259
260		/// <summary>
261		/// Crc 32 tests
262		/// </summary>
263		private class Crc32Tests
264		{
265			#region Helpers
266
267			#region TestCrc32
268			/// <summary>
269			/// Test crc 32
270			/// </summary>
271			public void TestCrc32()
272			{
273				Crc32 testCrc = new Crc32();
274
275				// Test assigning and clearing
276				testCrc.Value = 100;
277				Assert.Equal(100, testCrc.Value);
278				testCrc.Reset();
279				Assert.Equal(0, testCrc.Value);
280
281				// Throw in a byte array
282				byte[] someData = new byte[]
283				{
284					59, 49, 193, 98, 4, 199, 254, 9, 42
285				};
286				testCrc.Update(someData);
287				Assert.Equal(2271575830, testCrc.Value);
288
289				// Also test static methods
290				Assert.Equal(1131014251L, ComputeCrc32(65953, 201));
291				Assert.Equal(2271575830L, ComputeCrcValue(someData));
292			}
293			#endregion
294
295			#endregion
296		}
297	}
298}
```