| | 1 | | using System; |
| | 2 | |
|
| | 3 | | namespace ICSharpCode.SharpZipLib.Checksum |
| | 4 | | { |
| | 5 | | /// <summary> |
| | 6 | | /// CRC-32 with reversed data and unreversed output |
| | 7 | | /// </summary> |
| | 8 | | /// <remarks> |
| | 9 | | /// Generate a table for a byte-wise 32-bit CRC calculation on the polynomial: |
| | 10 | | /// 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+x^0. |
| | 11 | | /// |
| | 12 | | /// Polynomials over GF(2) are represented in binary, one bit per coefficient, |
| | 13 | | /// with the lowest powers in the most significant bit. Then adding polynomials |
| | 14 | | /// is just exclusive-or, and multiplying a polynomial by x is a right shift by |
| | 15 | | /// one. If we call the above polynomial p, and represent a byte as the |
| | 16 | | /// polynomial q, also with the lowest power in the most significant bit (so the |
| | 17 | | /// byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p, |
| | 18 | | /// where a mod b means the remainder after dividing a by b. |
| | 19 | | /// |
| | 20 | | /// This calculation is done using the shift-register method of multiplying and |
| | 21 | | /// taking the remainder. The register is initialized to zero, and for each |
| | 22 | | /// incoming bit, x^32 is added mod p to the register if the bit is a one (where |
| | 23 | | /// x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by |
| | 24 | | /// x (which is shifting right by one and adding x^32 mod p if the bit shifted |
| | 25 | | /// out is a one). We start with the highest power (least significant bit) of |
| | 26 | | /// 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's on data a byte at a time for all |
| | 30 | | /// combinations of CRC register values and incoming bytes. |
| | 31 | | /// </remarks> |
| | 32 | | public sealed class Crc32 : IChecksum |
| | 33 | | { |
| | 34 | | #region Instance Fields |
| 1 | 35 | | readonly static uint crcInit = 0xFFFFFFFF; |
| 1 | 36 | | readonly static uint crcXor = 0xFFFFFFFF; |
| | 37 | |
|
| 1 | 38 | | readonly static uint[] crcTable = { |
| 1 | 39 | | 0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, |
| 1 | 40 | | 0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4, |
| 1 | 41 | | 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, |
| 1 | 42 | | 0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE, |
| 1 | 43 | | 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856, |
| 1 | 44 | | 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9, |
| 1 | 45 | | 0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4, |
| 1 | 46 | | 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B, |
| 1 | 47 | | 0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, |
| 1 | 48 | | 0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A, |
| 1 | 49 | | 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599, |
| 1 | 50 | | 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924, |
| 1 | 51 | | 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190, |
| 1 | 52 | | 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, |
| 1 | 53 | | 0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E, |
| 1 | 54 | | 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01, |
| 1 | 55 | | 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED, |
| 1 | 56 | | 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950, |
| 1 | 57 | | 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, |
| 1 | 58 | | 0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, |
| 1 | 59 | | 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A, |
| 1 | 60 | | 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5, |
| 1 | 61 | | 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010, |
| 1 | 62 | | 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F, |
| 1 | 63 | | 0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, |
| 1 | 64 | | 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6, |
| 1 | 65 | | 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615, |
| 1 | 66 | | 0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8, |
| 1 | 67 | | 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344, |
| 1 | 68 | | 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB, |
| 1 | 69 | | 0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A, |
| 1 | 70 | | 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5, |
| 1 | 71 | | 0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, |
| 1 | 72 | | 0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C, |
| 1 | 73 | | 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF, |
| 1 | 74 | | 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236, |
| 1 | 75 | | 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE, |
| 1 | 76 | | 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, |
| 1 | 77 | | 0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C, |
| 1 | 78 | | 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713, |
| 1 | 79 | | 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B, |
| 1 | 80 | | 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242, |
| 1 | 81 | | 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, |
| 1 | 82 | | 0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, |
| 1 | 83 | | 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278, |
| 1 | 84 | | 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7, |
| 1 | 85 | | 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, |
| 1 | 86 | | 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9, |
| 1 | 87 | | 0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, |
| 1 | 88 | | 0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8, |
| 1 | 89 | | 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, |
| 1 | 90 | | 0x2D02EF8D |
| 1 | 91 | | }; |
| | 92 | |
|
| | 93 | | /// <summary> |
| | 94 | | /// The CRC data checksum so far. |
| | 95 | | /// </summary> |
| | 96 | | uint checkValue; |
| | 97 | | #endregion |
| | 98 | |
|
| | 99 | | internal static uint ComputeCrc32(uint oldCrc, byte bval) |
| | 100 | | { |
| 4516642 | 101 | | return (uint)(Crc32.crcTable[(oldCrc ^ bval) & 0xFF] ^ (oldCrc >> 8)); |
| | 102 | | } |
| | 103 | |
|
| | 104 | | /// <summary> |
| | 105 | | /// Initialise a default instance of <see cref="Crc32"></see> |
| | 106 | | /// </summary> |
| 66290 | 107 | | public Crc32() |
| | 108 | | { |
| 66290 | 109 | | Reset(); |
| 66290 | 110 | | } |
| | 111 | |
|
| | 112 | | /// <summary> |
| | 113 | | /// Resets the CRC data checksum as if no update was ever called. |
| | 114 | | /// </summary> |
| | 115 | | public void Reset() |
| | 116 | | { |
| 66451 | 117 | | checkValue = crcInit; |
| 66451 | 118 | | } |
| | 119 | |
|
| | 120 | | /// <summary> |
| | 121 | | /// Returns the CRC data checksum computed so far. |
| | 122 | | /// </summary> |
| | 123 | | /// <remarks>Reversed Out = false</remarks> |
| | 124 | | public long Value { |
| | 125 | | get { |
| 66251 | 126 | | return (long)(checkValue ^ crcXor); |
| | 127 | | } |
| | 128 | | } |
| | 129 | |
|
| | 130 | | /// <summary> |
| | 131 | | /// Updates the checksum with the int bval. |
| | 132 | | /// </summary> |
| | 133 | | /// <param name = "bval"> |
| | 134 | | /// the byte is taken as the lower 8 bits of bval |
| | 135 | | /// </param> |
| | 136 | | /// <remarks>Reversed Data = true</remarks> |
| | 137 | | public void Update(int bval) |
| | 138 | | { |
| 4528259 | 139 | | checkValue = unchecked(crcTable[(checkValue ^ bval) & 0xFF] ^ (checkValue >> 8)); |
| 4528259 | 140 | | } |
| | 141 | |
|
| | 142 | | /// <summary> |
| | 143 | | /// Updates the CRC data checksum with the bytes taken from |
| | 144 | | /// a block of data. |
| | 145 | | /// </summary> |
| | 146 | | /// <param name="buffer">Contains the data to update the CRC with.</param> |
| | 147 | | public void Update(byte[] buffer) |
| | 148 | | { |
| 2 | 149 | | if (buffer == null) { |
| 1 | 150 | | throw new ArgumentNullException(nameof(buffer)); |
| | 151 | | } |
| | 152 | |
|
| 1 | 153 | | Update(buffer, 0, buffer.Length); |
| 1 | 154 | | } |
| | 155 | |
|
| | 156 | | /// <summary> |
| | 157 | | /// Update CRC data checksum based on a portion of a block of data |
| | 158 | | /// </summary> |
| | 159 | | /// <param name = "buffer">Contains the data to update the CRC with.</param> |
| | 160 | | /// <param name = "offset">The offset into the buffer where the data starts</param> |
| | 161 | | /// <param name = "count">The number of data bytes to update the CRC with.</param> |
| | 162 | | public void Update(byte[] buffer, int offset, int count) |
| | 163 | | { |
| 5155 | 164 | | if (buffer == null) { |
| 1 | 165 | | throw new ArgumentNullException(nameof(buffer)); |
| | 166 | | } |
| | 167 | |
|
| 5154 | 168 | | if (offset < 0) { |
| 1 | 169 | | throw new ArgumentOutOfRangeException(nameof(offset), "cannot be less than zero"); |
| | 170 | | } |
| | 171 | |
|
| 5153 | 172 | | if (offset >= buffer.Length) { |
| 2 | 173 | | throw new ArgumentOutOfRangeException(nameof(offset), "not a valid index into buffer"); |
| | 174 | | } |
| | 175 | |
|
| 5151 | 176 | | if (count < 0) { |
| 1 | 177 | | throw new ArgumentOutOfRangeException(nameof(count), "cannot be less than zero"); |
| | 178 | | } |
| | 179 | |
|
| 5150 | 180 | | if (offset + count > buffer.Length) { |
| 1 | 181 | | throw new ArgumentOutOfRangeException(nameof(count), "exceeds buffer size"); |
| | 182 | | } |
| | 183 | |
|
| 9066816 | 184 | | for (int i = 0; i < count; ++i) { |
| 4528259 | 185 | | Update(buffer[offset++]); |
| | 186 | | } |
| 5149 | 187 | | } |
| | 188 | | } |
| | 189 | | } |