当前文件路径：x3blogAccessBuild80707/SharpZipLib/Checksums/CRC32.cs

		            
  1// CRC32.cs - Computes CRC32 data checksum of a data stream
  2// Copyright (C) 2001 Mike Krueger
  3//
  4// This file was translated from java, it was part of the GNU Classpath
  5// Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
  6//
  7// This program is free software; you can redistribute it and/or
  8// modify it under the terms of the GNU General Public License
  9// as published by the Free Software Foundation; either version 2
 10// of the License, or (at your option) any later version.
 11//
 12// This program is distributed in the hope that it will be useful,
 13// but WITHOUT ANY WARRANTY; without even the implied warranty of
 14// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15// GNU General Public License for more details.
 16//
 17// You should have received a copy of the GNU General Public License
 18// along with this program; if not, write to the Free Software
 19// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 20//
 21// Linking this library statically or dynamically with other modules is
 22// making a combined work based on this library.  Thus, the terms and
 23// conditions of the GNU General Public License cover the whole
 24// combination.
 25// 
 26// As a special exception, the copyright holders of this library give you
 27// permission to link this library with independent modules to produce an
 28// executable, regardless of the license terms of these independent
 29// modules, and to copy and distribute the resulting executable under
 30// terms of your choice, provided that you also meet, for each linked
 31// independent module, the terms and conditions of the license of that
 32// module.  An independent module is a module which is not derived from
 33// or based on this library.  If you modify this library, you may extend
 34// this exception to your version of the library, but you are not
 35// obligated to do so.  If you do not wish to do so, delete this
 36// exception statement from your version.
 37
 38using System;
 39
 40namespace ICSharpCode.SharpZipLib.Checksums 
 41...{
 42    
 43    /**//// <summary>
 44    /// Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
 45    /// 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.
 46    ///
 47    /// Polynomials over GF(2) are represented in binary, one bit per coefficient,
 48    /// with the lowest powers in the most significant bit.  Then adding polynomials
 49    /// is just exclusive-or, and multiplying a polynomial by x is a right shift by
 50    /// one.  If we call the above polynomial p, and represent a byte as the
 51    /// polynomial q, also with the lowest power in the most significant bit (so the
 52    /// byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
 53    /// where a mod b means the remainder after dividing a by b.
 54    ///
 55    /// This calculation is done using the shift-register method of multiplying and
 56    /// taking the remainder.  The register is initialized to zero, and for each
 57    /// incoming bit, x^32 is added mod p to the register if the bit is a one (where
 58    /// x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
 59    /// x (which is shifting right by one and adding x^32 mod p if the bit shifted
 60    /// out is a one).  We start with the highest power (least significant bit) of
 61    /// q and repeat for all eight bits of q.
 62    ///
 63    /// The table is simply the CRC of all possible eight bit values.  This is all
 64    /// the information needed to generate CRC's on data a byte at a time for all
 65    /// combinations of CRC register values and incoming bytes.
 66    /// </summary>
 67    public sealed class Crc32 : IChecksum
 68    ...{
 69        readonly static uint CrcSeed = 0xFFFFFFFF;
 70        
 71        readonly static uint[] CrcTable = new uint[] ...{
 72            0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
 73            0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
 74            0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
 75            0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
 76            0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856,
 77            0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
 78            0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
 79            0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
 80            0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
 81            0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
 82            0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
 83            0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
 84            0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
 85            0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
 86            0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
 87            0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
 88            0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
 89            0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
 90            0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
 91            0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
 92            0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
 93            0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
 94            0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
 95            0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
 96            0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
 97            0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
 98            0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
 99            0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
100            0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
101            0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
102            0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
103            0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
104            0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
105            0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
106            0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
107            0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
108            0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
109            0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
110            0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
111            0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
112            0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
113            0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
114            0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
115            0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
116            0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
117            0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
118            0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
119            0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
120            0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
121            0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
122            0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
123            0x2D02EF8D
124        };
125        
126        internal static uint ComputeCrc32(uint oldCrc, byte bval)
127        ...{
128            return (uint)(Crc32.CrcTable[(oldCrc ^ bval) & 0xFF] ^ (oldCrc >> 8));
129        }
130        
131        /**//// <summary>
132        /// The crc data checksum so far.
133        /// </summary>
134        uint crc = 0;
135        
136        /**//// <summary>
137        /// Returns the CRC32 data checksum computed so far.
138        /// </summary>
139        public long Value ...{
140            get ...{
141                return (long)crc;
142            }
143            set ...{
144                crc = (uint)value;
145            }
146        }
147        
148        /**//// <summary>
149        /// Resets the CRC32 data checksum as if no update was ever called.
150        /// </summary>
151        public void Reset() 
152        ...{ 
153            crc = 0; 
154        }
155        
156        /**//// <summary>
157        /// Updates the checksum with the int bval.
158        /// </summary>
159        /// <param name = "bval">
160        /// the byte is taken as the lower 8 bits of bval
161        /// </param>
162        public void Update(int bval)
163        ...{
164            crc ^= CrcSeed;
165            crc  = CrcTable[(crc ^ bval) & 0xFF] ^ (crc >> 8);
166            crc ^= CrcSeed;
167        }
168        
169        /**//// <summary>
170        /// Updates the checksum with the bytes taken from the array.
171        /// </summary>
172        /// <param name="buffer">
173        /// buffer an array of bytes
174        /// </param>
175        public void Update(byte[] buffer)
176        ...{
177            Update(buffer, 0, buffer.Length);
178        }
179        
180        /**//// <summary>
181        /// Adds the byte array to the data checksum.
182        /// </summary>
183        /// <param name = "buf">
184        /// the buffer which contains the data
185        /// </param>
186        /// <param name = "off">
187        /// the offset in the buffer where the data starts
188        /// </param>
189        /// <param name = "len">
190        /// the length of the data
191        /// </param>
192        public void Update(byte[] buf, int off, int len)
193        ...{
194            if (buf == null) ...{
195                throw new ArgumentNullException("buf");
196            }
197            
198            if (off < 0 || len < 0 || off + len > buf.Length) ...{
199                throw new ArgumentOutOfRangeException();
200            }
201            
202            crc ^= CrcSeed;
203            
204            while (--len >= 0) ...{
205                crc = CrcTable[(crc ^ buf[off++]) & 0xFF] ^ (crc >> 8);
206            }
207            
208            crc ^= CrcSeed;
209        }
210    }
211}
212