C# Class Ionic.Crc.CRC32

ファイルを表示 Open project: haf/DotNetZip.Semverd Class Usage Examples

Public Methods

Method	Description
CRC32 ( ) : System	Create an instance of the CRC32 class using the default settings: no bit reversal, and a polynomial of 0xEDB88320.
CRC32 ( bool reverseBits ) : System	Create an instance of the CRC32 class, specifying whether to reverse data bits or not. In the CRC-32 used by BZip2, the bits are reversed. Therefore if you want a CRC32 with compatibility with BZip2, you should pass true here. In the CRC-32 used by GZIP and PKZIP, the bits are not reversed; Therefore if you want a CRC32 with compatibility with those, you should pass false.
CRC32 ( int polynomial, bool reverseBits ) : System	Create an instance of the CRC32 class, specifying the polynomial and whether to reverse data bits or not. In the CRC-32 used by BZip2, the bits are reversed. Therefore if you want a CRC32 with compatibility with BZip2, you should pass true here for the `reverseBits` parameter. In the CRC-32 used by GZIP and PKZIP, the bits are not reversed; Therefore if you want a CRC32 with compatibility with those, you should pass false for the `reverseBits` parameter.
Combine ( int crc, int length ) : void	Combines the given CRC32 value with the current running total. This is useful when using a divide-and-conquer approach to calculating a CRC. Multiple threads can each calculate a CRC32 on a segment of the data, and then combine the individual CRC32 values at the end.
ComputeCrc32 ( Int32 W, byte B ) : Int32	Get the CRC32 for the given (word,byte) combo. This is a computation defined by PKzip for PKZIP 2.0 (weak) encryption.
GetCrc32 ( System input ) : Int32	Returns the CRC32 for the specified stream.
GetCrc32AndCopy ( System input, System output ) : Int32	Returns the CRC32 for the specified stream, and writes the input into the output stream.
Reset ( ) : void	Reset the CRC-32 class - clear the CRC "remainder register." Use this when employing a single instance of this class to compute multiple, distinct CRCs on multiple, distinct data blocks.
SlurpBlock ( byte block, int offset, int count ) : void	Update the value for the running CRC32 using the given block of bytes. This is useful when using the CRC32() class in a Stream.
UpdateCRC ( byte b ) : void	Process one byte in the CRC.
UpdateCRC ( byte b, int n ) : void	Process a run of N identical bytes into the CRC. This method serves as an optimization for updating the CRC when a run of identical bytes is found. Rather than passing in a buffer of length n, containing all identical bytes b, this method accepts the byte value and the length of the (virtual) buffer - the length of the run.

Private Methods

Method	Description
GenerateLookupTable ( ) : void
ReverseBits ( byte data ) : byte
ReverseBits ( uint data ) : uint
_InternalComputeCrc32 ( UInt32 W, byte B ) : Int32
gf2_matrix_square ( uint square, uint mat ) : void
gf2_matrix_times ( uint matrix, uint vec ) : uint

Method Details

CRC32() public method

Create an instance of the CRC32 class using the default settings: no bit reversal, and a polynomial of 0xEDB88320.

public CRC32 ( ) : System
return	System

CRC32() public method

Create an instance of the CRC32 class, specifying whether to reverse data bits or not.

In the CRC-32 used by BZip2, the bits are reversed. Therefore if you want a CRC32 with compatibility with BZip2, you should pass true here. In the CRC-32 used by GZIP and PKZIP, the bits are not reversed; Therefore if you want a CRC32 with compatibility with those, you should pass false.

public CRC32 ( bool reverseBits ) : System
reverseBits	bool	/// specify true if the instance should reverse data bits. ///
return	System

CRC32() public method

Create an instance of the CRC32 class, specifying the polynomial and whether to reverse data bits or not.

In the CRC-32 used by BZip2, the bits are reversed. Therefore if you want a CRC32 with compatibility with BZip2, you should pass true here for the reverseBits parameter. In the CRC-32 used by GZIP and PKZIP, the bits are not reversed; Therefore if you want a CRC32 with compatibility with those, you should pass false for the reverseBits parameter.

public CRC32 ( int polynomial, bool reverseBits ) : System
polynomial	int	/// The polynomial to use for the CRC, expressed in the reversed (LSB) /// format: the highest ordered bit in the polynomial value is the /// coefficient of the 0th power; the second-highest order bit is the /// coefficient of the 1 power, and so on. Expressed this way, the /// polynomial for the CRC-32C used in IEEE 802.3, is 0xEDB88320. ///
reverseBits	bool	/// specify true if the instance should reverse data bits. ///
return	System

Combine() public method

Combines the given CRC32 value with the current running total.

This is useful when using a divide-and-conquer approach to calculating a CRC. Multiple threads can each calculate a CRC32 on a segment of the data, and then combine the individual CRC32 values at the end.

public Combine ( int crc, int length ) : void
crc	int	the crc value to be combined with this one
length	int	the length of data the CRC value was calculated on
return	void

ComputeCrc32() public method

Get the CRC32 for the given (word,byte) combo. This is a computation defined by PKzip for PKZIP 2.0 (weak) encryption.

public ComputeCrc32 ( Int32 W, byte B ) : Int32
W	System.Int32	The word to start with.
B	byte	The byte to combine it with.
return	System.Int32

GetCrc32() public method

Returns the CRC32 for the specified stream.

public GetCrc32 ( System input ) : Int32
input	System	The stream over which to calculate the CRC32
return	System.Int32

GetCrc32AndCopy() public method

Returns the CRC32 for the specified stream, and writes the input into the output stream.

public GetCrc32AndCopy ( System input, System output ) : Int32
input	System	The stream over which to calculate the CRC32
output	System	The stream into which to deflate the input
return	System.Int32

Reset() public method

Reset the CRC-32 class - clear the CRC "remainder register."

Use this when employing a single instance of this class to compute multiple, distinct CRCs on multiple, distinct data blocks.

public Reset ( ) : void
return	void

SlurpBlock() public method

Update the value for the running CRC32 using the given block of bytes. This is useful when using the CRC32() class in a Stream.

public SlurpBlock ( byte block, int offset, int count ) : void
block	byte	block of bytes to slurp
offset	int	starting point in the block
count	int	how many bytes within the block to slurp
return	void

UpdateCRC() public method

Process one byte in the CRC.

public UpdateCRC ( byte b ) : void
b	byte	the byte to include into the CRC .
return	void

UpdateCRC() public method

Process a run of N identical bytes into the CRC.

This method serves as an optimization for updating the CRC when a run of identical bytes is found. Rather than passing in a buffer of length n, containing all identical bytes b, this method accepts the byte value and the length of the (virtual) buffer - the length of the run.

public UpdateCRC ( byte b, int n ) : void
b	byte	the byte to include into the CRC.
n	int	the number of times that byte should be repeated.
return	void