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/Utilities/Compression/Checksums/Crc32.cs

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C# | 298 lines | 176 code | 31 blank | 91 comment | 7 complexity | 761ea8406bed06a46eff72c34bc6b6e1 MD5 | raw file
Possible License(s): Apache-2.0
  1. using System;
  2. using System.IO;
  3. namespace Delta.Utilities.Compression.Checksums
  4. {
  5. /// <summary>
  6. /// Crc32 - Computes CRC32 data checksum of a data stream. Generate
  7. /// a table for a byte-wise 32-bit CRC calculation on the polynomial:
  8. /// 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.
  9. ///
  10. /// Polynomials over GF(2) are represented in binary, one bit per
  11. /// coefficient, with the lowest powers in the most significant bit.
  12. /// Then adding polynomials is just exclusive-or, and multiplying a
  13. /// polynomial by x is a right shift by one. If we call the above polynomial
  14. /// p, and represent a byte as the polynomial q, also with the lowest power
  15. /// in the most significant bit (so the byte 0xb1 is the polynomial
  16. /// x^7+x^3+x+1), then the CRC is (q*x^32) mod p, where a mod b means the
  17. /// remainder after dividing a by b.
  18. ///
  19. /// This calculation is done using the shift-register method of multiplying
  20. /// and taking the remainder. The register is initialized to zero, and for
  21. /// each incoming bit, x^32 is added mod p to the register if the bit is a
  22. /// one (where x^32 mod p is p+x^32 = x^26+...+1), and the register is
  23. /// multiplied mod p by x (which is shifting right by one and adding
  24. /// x^32 mod p if the bit shifted out is a one). We start with the highest
  25. /// power (least significant bit) of q and repeat for all eight bits of q.
  26. ///
  27. /// The table is simply the CRC of all possible eight bit values. This is all
  28. /// the information needed to generate CRC'str on data a byte at a time for
  29. /// all combinations of CRC register values and incoming bytes.
  30. /// </summary>
  31. public sealed class Crc32
  32. {
  33. #region Constants
  34. /// <summary>
  35. /// Crc seed
  36. /// </summary>
  37. private const uint CrcSeed = 0xFFFFFFFF;
  38. /// <summary>
  39. /// Crc table
  40. /// </summary>
  41. /// <returns>Uint []</returns>
  42. private static readonly uint[] CrcTable = new uint[]
  43. {
  44. 0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
  45. 0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
  46. 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
  47. 0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
  48. 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856,
  49. 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
  50. 0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
  51. 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
  52. 0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
  53. 0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
  54. 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
  55. 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
  56. 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
  57. 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
  58. 0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
  59. 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
  60. 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
  61. 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
  62. 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
  63. 0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
  64. 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
  65. 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
  66. 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
  67. 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
  68. 0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
  69. 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
  70. 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
  71. 0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
  72. 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
  73. 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
  74. 0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
  75. 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
  76. 0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
  77. 0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
  78. 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
  79. 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
  80. 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
  81. 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
  82. 0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
  83. 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
  84. 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
  85. 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
  86. 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
  87. 0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
  88. 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
  89. 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
  90. 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
  91. 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
  92. 0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
  93. 0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
  94. 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
  95. 0x2D02EF8D
  96. };
  97. #endregion
  98. #region ComputeCrcValue (Static)
  99. /// <summary>
  100. /// Compute crc value
  101. /// </summary>
  102. /// <param name="buffer">Buffer</param>
  103. /// <returns>Long</returns>
  104. public static long ComputeCrcValue(byte[] buffer)
  105. {
  106. Crc32 crc = new Crc32();
  107. crc.Update(buffer);
  108. return crc.Value;
  109. }
  110. // ComputeCrcValue(buffer)
  111. /// <summary>
  112. /// Compute crc value
  113. /// </summary>
  114. /// <param name="stream">Stream</param>
  115. /// <returns>Long</returns>
  116. public static long ComputeCrcValue(Stream stream)
  117. {
  118. // Make sure the stream is good to go.
  119. if (stream.CanRead == false ||
  120. stream.CanSeek == false)
  121. {
  122. throw new NotSupportedException(
  123. "Can't calculated checksum of a stream that does not support " +
  124. "reading or seeking!");
  125. }
  126. // Remember old stream position
  127. long oldPosition = stream.Position;
  128. // Get all data
  129. byte[] buffer = new byte[stream.Length];
  130. stream.Seek(0, SeekOrigin.Begin);
  131. stream.Read(buffer, 0, (int)stream.Length);
  132. // Restore old position
  133. stream.Position = oldPosition;
  134. // Compute and return checksum
  135. return ComputeCrcValue(buffer);
  136. }
  137. #endregion
  138. #region Value (Public)
  139. /// <summary>
  140. /// Returns the CRC32 data checksum computed so far.
  141. /// </summary>
  142. public long Value
  143. {
  144. get
  145. {
  146. return crc;
  147. } // get
  148. set
  149. {
  150. crc = (uint)value;
  151. } // set
  152. }
  153. #endregion
  154. #region Private
  155. #region crc (Private)
  156. /// <summary>
  157. /// The crc data checksum so far.
  158. /// </summary>
  159. private uint crc;
  160. #endregion
  161. #endregion
  162. #region Reset (Public)
  163. /// <summary>
  164. /// Resets the CRC32 data checksum as if no update was ever called.
  165. /// </summary>
  166. public void Reset()
  167. {
  168. crc = 0;
  169. }
  170. #endregion
  171. #region Update (Public)
  172. /// <summary>
  173. /// Updates the checksum with the int value.
  174. /// </summary>
  175. /// <param name="value">Byte is taken as the lower 8 bits of value</param>
  176. public void Update(int value)
  177. {
  178. crc ^= CrcSeed;
  179. crc = CrcTable[(crc ^ value) & 0xFF] ^ (crc >> 8);
  180. crc ^= CrcSeed;
  181. }
  182. // Update(value)
  183. /// <summary>
  184. /// Updates the checksum with the bytes taken from the array.
  185. /// </summary>
  186. /// <param name="buffer">
  187. /// buffer an array of bytes
  188. /// </param>
  189. public void Update(byte[] buffer)
  190. {
  191. Update(buffer, 0, buffer.Length);
  192. }
  193. // Update(buffer)
  194. /// <summary>
  195. /// Adds the byte array to the data checksum.
  196. /// </summary>
  197. /// <param name="buffer">Buffer which contains the data</param>
  198. /// <param name="offset">Offset in the buffer where the data starts</param>
  199. /// <param name="count">Length of the data</param>
  200. public void Update(byte[] buffer, int offset, int count)
  201. {
  202. if (buffer == null)
  203. {
  204. throw new ArgumentNullException("buffer");
  205. } // if (buf)
  206. if (offset < 0 ||
  207. count < 0 ||
  208. offset + count > buffer.Length)
  209. {
  210. throw new ArgumentOutOfRangeException();
  211. } // if (off)
  212. crc ^= CrcSeed;
  213. while (--count >= 0)
  214. {
  215. crc = CrcTable[(crc ^ buffer[offset++]) & 0xFF] ^ (crc >> 8);
  216. } // while (--len)
  217. crc ^= CrcSeed;
  218. }
  219. #endregion
  220. #region Methods (Private)
  221. #region ComputeCrc32
  222. /// <summary>
  223. /// Compute crc 32
  224. /// </summary>
  225. /// <param name="oldCrc">Old crc</param>
  226. /// <param name="value">Value</param>
  227. /// <returns>Uint</returns>
  228. internal static uint ComputeCrc32(uint oldCrc, byte value)
  229. {
  230. return (CrcTable[(oldCrc ^ value) & 0xFF] ^ (oldCrc >> 8));
  231. }
  232. #endregion
  233. #endregion
  234. /// <summary>
  235. /// Crc 32 tests
  236. /// </summary>
  237. private class Crc32Tests
  238. {
  239. #region Helpers
  240. #region TestCrc32
  241. /// <summary>
  242. /// Test crc 32
  243. /// </summary>
  244. public void TestCrc32()
  245. {
  246. Crc32 testCrc = new Crc32();
  247. // Test assigning and clearing
  248. testCrc.Value = 100;
  249. Assert.Equal(100, testCrc.Value);
  250. testCrc.Reset();
  251. Assert.Equal(0, testCrc.Value);
  252. // Throw in a byte array
  253. byte[] someData = new byte[]
  254. {
  255. 59, 49, 193, 98, 4, 199, 254, 9, 42
  256. };
  257. testCrc.Update(someData);
  258. Assert.Equal(2271575830, testCrc.Value);
  259. // Also test static methods
  260. Assert.Equal(1131014251L, ComputeCrc32(65953, 201));
  261. Assert.Equal(2271575830L, ComputeCrcValue(someData));
  262. }
  263. #endregion
  264. #endregion
  265. }
  266. }
  267. }