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//-----------------------------------------------------------------------------
//------------- *** WARNING ***
//------------- This file is part of a legally monitored development project.
//------------- Do not check in changes to this project. Do not raid bugs on this
//------------- code in the main PS database. Do not contact the owner of this
//------------- code directly. Contact the legal team at ‘ZSLegal’ for assistance.
//------------- *** WARNING ***
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//
// <copyright file="CRC32.cs" company="Microsoft">
// Copyright (C) Microsoft Corporation. All rights reserved.
// </copyright>
//
// Description:
// This is a CRC32 calculator, originally built for ZIP IO for OPC scenarios.
// This particular piece of code generic, and doest have ane ZIP or OPC specific
// features
//
// History:
// 11/19/2004: IgorBel: Initial creation.
//
//-----------------------------------------------------------------------------
using System;
using System.IO;
using System.Diagnostics;
namespace MS.Internal.IO.Zip
{
internal class Crc32Calculator
{
/// <summary>
/// We need to initialize table once per all intstances of this class
/// Instead of using static constructor, we are using lock to do this so that
/// we don't get into a threading issue
/// </summary>
internal Crc32Calculator()
{
lock (_globalSync)
{
if (_Crc32Table == null)
{
PrepareTable();
}
}
}
// Calculate CRC from the current position to the end of the stream
// CRC is calculated accumulatively on to the current residue
internal UInt32 CalculateStreamCrc(Stream stream)
{
byte[] buffer = new byte[0x1000];
Debug.Assert(stream != null);
for(;;)
{
int bytesRead = stream.Read(buffer,0,buffer.Length);
if (bytesRead > 0)
{
Accumulate(buffer, 0, bytesRead);
}
else
{
break;
}
}
return Crc;
}
internal void Accumulate(byte[] buffer, int offset, int count)
{
Debug.Assert((offset >=0) && (count >=0) && (offset+count <= buffer.Length));
for(int i =offset; i<count+offset; i++)
{
_residue = ((_residue >> 8) & 0x00FFFFFF)
^
_Crc32Table[((_residue ^ buffer[i]) & 0x000000FF)];
}
}
internal UInt32 Crc
{
get
{
return ~_residue;
}
}
// set the residue to the intial value so that we can recalculate CRC
internal void ClearCrc()
{
_residue = _InitialResidueValue;
}
static private void PrepareTable()
{
_Crc32Table = new UInt32[256];
for(uint tablePosition=0; tablePosition < _Crc32Table.Length; tablePosition++)
{
for(byte bitPosition=0; bitPosition < 32; bitPosition++)
{
bool bitValue = false;
foreach(byte maskingBit in _maskingBitTable[bitPosition])
{
bitValue ^= GetBit(maskingBit, tablePosition);
}
SetBit(bitPosition, ref (_Crc32Table[tablePosition]), bitValue);
}
}
}
private static bool GetBit(byte bitOrdinal, UInt32 data)
{
Debug.Assert(bitOrdinal < 32);
return ((data >> bitOrdinal) & 0x1) == 1;
}
// only valid in this context (the bit in to is always 0)
private static void SetBit(byte bitOrdinal, ref UInt32 data, bool value)
{
Debug.Assert(bitOrdinal < 32);
if (value)
{
data |= ((UInt32)0x1 << bitOrdinal);
}
}
private const UInt32 _InitialResidueValue = 0xFFFFFFFF;
private UInt32 _residue = _InitialResidueValue;
private static Object _globalSync = new Object();
// static CRC table , which is calculated in the stqatic constructor
private static UInt32[] _Crc32Table;
// static bit mask table that is used to calculate _Crc32Table
private static byte[][] _maskingBitTable =
{new byte[] {2},
new byte[] {0,3},
new byte[] {0,1,4},
new byte[] {1,2,5},
new byte[] {0,2,3,6},
new byte[] {1,3,4,7},
new byte[] {4,5},
new byte[] {0,5,6},
new byte[] {1,6,7},
new byte[] {7},
new byte[] {2},
new byte[] {3},
new byte[] {0,4},
new byte[] {0,1,5},
new byte[] {1,2,6},
new byte[] {2,3,7},
new byte[] {0,2,3,4},
new byte[] {0,1,3,4,5},
new byte[] {0,1,2,4,5,6},
new byte[] {1,2,3,5,6,7},
new byte[] {3,4,6,7},
new byte[] {2,4,5,7},
new byte[] {2,3,5,6},
new byte[] {3,4,6,7},
new byte[] {0,2,4,5,7},
new byte[] {0,1,2,3,5,6},
new byte[] {0,1,2,3,4,6,7},
new byte[] {1,3,4,5,7},
new byte[] {0,4,5,6},
new byte[] {0,1,5,6,7},
new byte[] {0,1,6,7},
new byte[] {1,7}};
// _Crc32Table should contain the following :
// --CRC32 Table--
// 0000000000 - 0000000000 0x77073096 0xee0e612c 0x990951ba
// 0x00000004 - 0x076dc419 0x706af48f 0xe963a535 0x9e6495a3
// 0x00000008 - 0x0edb8832 0x79dcb8a4 0xe0d5e91e 0x97d2d988
// 0x0000000c - 0x09b64c2b 0x7eb17cbd 0xe7b82d07 0x90bf1d91
// 0x00000010 - 0x1db71064 0x6ab020f2 0xf3b97148 0x84be41de
// 0x00000014 - 0x1adad47d 0x6ddde4eb 0xf4d4b551 0x83d385c7
// 0x00000018 - 0x136c9856 0x646ba8c0 0xfd62f97a 0x8a65c9ec
// 0x0000001c - 0x14015c4f 0x63066cd9 0xfa0f3d63 0x8d080df5
// 0x00000020 - 0x3b6e20c8 0x4c69105e 0xd56041e4 0xa2677172
// 0x00000024 - 0x3c03e4d1 0x4b04d447 0xd20d85fd 0xa50ab56b
// 0x00000028 - 0x35b5a8fa 0x42b2986c 0xdbbbc9d6 0xacbcf940
// 0x0000002c - 0x32d86ce3 0x45df5c75 0xdcd60dcf 0xabd13d59
// 0x00000030 - 0x26d930ac 0x51de003a 0xc8d75180 0xbfd06116
// 0x00000034 - 0x21b4f4b5 0x56b3c423 0xcfba9599 0xb8bda50f
// 0x00000038 - 0x2802b89e 0x5f058808 0xc60cd9b2 0xb10be924
// 0x0000003c - 0x2f6f7c87 0x58684c11 0xc1611dab 0xb6662d3d
// 0x00000040 - 0x76dc4190 0x01db7106 0x98d220bc 0xefd5102a
// 0x00000044 - 0x71b18589 0x06b6b51f 0x9fbfe4a5 0xe8b8d433
// 0x00000048 - 0x7807c9a2 0x0f00f934 0x9609a88e 0xe10e9818
// 0x0000004c - 0x7f6a0dbb 0x086d3d2d 0x91646c97 0xe6635c01
// 0x00000050 - 0x6b6b51f4 0x1c6c6162 0x856530d8 0xf262004e
// 0x00000054 - 0x6c0695ed 0x1b01a57b 0x8208f4c1 0xf50fc457
// 0x00000058 - 0x65b0d9c6 0x12b7e950 0x8bbeb8ea 0xfcb9887c
// 0x0000005c - 0x62dd1ddf 0x15da2d49 0x8cd37cf3 0xfbd44c65
// 0x00000060 - 0x4db26158 0x3ab551ce 0xa3bc0074 0xd4bb30e2
// 0x00000064 - 0x4adfa541 0x3dd895d7 0xa4d1c46d 0xd3d6f4fb
// 0x00000068 - 0x4369e96a 0x346ed9fc 0xad678846 0xda60b8d0
// 0x0000006c - 0x44042d73 0x33031de5 0xaa0a4c5f 0xdd0d7cc9
// 0x00000070 - 0x5005713c 0x270241aa 0xbe0b1010 0xc90c2086
// 0x00000074 - 0x5768b525 0x206f85b3 0xb966d409 0xce61e49f
// 0x00000078 - 0x5edef90e 0x29d9c998 0xb0d09822 0xc7d7a8b4
// 0x0000007c - 0x59b33d17 0x2eb40d81 0xb7bd5c3b 0xc0ba6cad
// 0x00000080 - 0xedb88320 0x9abfb3b6 0x03b6e20c 0x74b1d29a
// 0x00000084 - 0xead54739 0x9dd277af 0x04db2615 0x73dc1683
// 0x00000088 - 0xe3630b12 0x94643b84 0x0d6d6a3e 0x7a6a5aa8
// 0x0000008c - 0xe40ecf0b 0x9309ff9d 0x0a00ae27 0x7d079eb1
// 0x00000090 - 0xf00f9344 0x8708a3d2 0x1e01f268 0x6906c2fe
// 0x00000094 - 0xf762575d 0x806567cb 0x196c3671 0x6e6b06e7
// 0x00000098 - 0xfed41b76 0x89d32be0 0x10da7a5a 0x67dd4acc
// 0x0000009c - 0xf9b9df6f 0x8ebeeff9 0x17b7be43 0x60b08ed5
// 0x000000a0 - 0xd6d6a3e8 0xa1d1937e 0x38d8c2c4 0x4fdff252
// 0x000000a4 - 0xd1bb67f1 0xa6bc5767 0x3fb506dd 0x48b2364b
// 0x000000a8 - 0xd80d2bda 0xaf0a1b4c 0x36034af6 0x41047a60
// 0x000000ac - 0xdf60efc3 0xa867df55 0x316e8eef 0x4669be79
// 0x000000b0 - 0xcb61b38c 0xbc66831a 0x256fd2a0 0x5268e236
// 0x000000b4 - 0xcc0c7795 0xbb0b4703 0x220216b9 0x5505262f
// 0x000000b8 - 0xc5ba3bbe 0xb2bd0b28 0x2bb45a92 0x5cb36a04
// 0x000000bc - 0xc2d7ffa7 0xb5d0cf31 0x2cd99e8b 0x5bdeae1d
// 0x000000c0 - 0x9b64c2b0 0xec63f226 0x756aa39c 0x026d930a
// 0x000000c4 - 0x9c0906a9 0xeb0e363f 0x72076785 0x05005713
// 0x000000c8 - 0x95bf4a82 0xe2b87a14 0x7bb12bae 0x0cb61b38
// 0x000000cc - 0x92d28e9b 0xe5d5be0d 0x7cdcefb7 0x0bdbdf21
// 0x000000d0 - 0x86d3d2d4 0xf1d4e242 0x68ddb3f8 0x1fda836e
// 0x000000d4 - 0x81be16cd 0xf6b9265b 0x6fb077e1 0x18b74777
// 0x000000d8 - 0x88085ae6 0xff0f6a70 0x66063bca 0x11010b5c
// 0x000000dc - 0x8f659eff 0xf862ae69 0x616bffd3 0x166ccf45
// 0x000000e0 - 0xa00ae278 0xd70dd2ee 0x4e048354 0x3903b3c2
// 0x000000e4 - 0xa7672661 0xd06016f7 0x4969474d 0x3e6e77db
// 0x000000e8 - 0xaed16a4a 0xd9d65adc 0x40df0b66 0x37d83bf0
// 0x000000ec - 0xa9bcae53 0xdebb9ec5 0x47b2cf7f 0x30b5ffe9
// 0x000000f0 - 0xbdbdf21c 0xcabac28a 0x53b39330 0x24b4a3a6
// 0x000000f4 - 0xbad03605 0xcdd70693 0x54de5729 0x23d967bf
// 0x000000f8 - 0xb3667a2e 0xc4614ab8 0x5d681b02 0x2a6f2b94
// 0x000000fc - 0xb40bbe37 0xc30c8ea1 0x5a05df1b 0x2d02ef8d
}
}
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