Detailed Description

Encoder and Decoder for ZLIB and DEFLATE (IETF RFC1950 and RFC1951).

This class compresses and decompresses data according to the Deflate algorithm and optionally, the ZLIB format, as documented in RFC 1950 - ZLIB

and RFC 1951 - DEFLATE

.

Public Member Functions
	ZlibCodec ()
	Create a ZlibCodec. More...

	ZlibCodec (CompressionMode mode)
	Create a ZlibCodec that either compresses or decompresses. More...

int	InitializeInflate ()
	Initialize the inflation state. More...

int	InitializeInflate (bool expectRfc1950Header)
	Initialize the inflation state with an explicit flag to govern the handling of RFC1950 header bytes. More...

int	InitializeInflate (int windowBits)
	Initialize the ZlibCodec for inflation, with the specified number of window bits. More...

int	InitializeInflate (int windowBits, bool expectRfc1950Header)
	Initialize the inflation state with an explicit flag to govern the handling of RFC1950 header bytes. More...

int	EndInflate ()
	Ends an inflation session. More...

int	SyncInflate ()
	I don't know what this does! More...

int	InitializeDeflate ()
	Initialize the ZlibCodec for deflation operation. More...

int	InitializeDeflate (CompressionLevel level)
	Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel. More...

int	InitializeDeflate (CompressionLevel level, bool wantRfc1950Header)
	Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel, and the explicit flag governing whether to emit an RFC1950 header byte pair. More...

int	InitializeDeflate (CompressionLevel level, int bits)
	Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel, and the specified number of window bits. More...

int	InitializeDeflate (CompressionLevel level, int bits, bool wantRfc1950Header)
	Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel, the specified number of window bits, and the explicit flag governing whether to emit an RFC1950 header byte pair. More...

int	EndDeflate ()
	End a deflation session. More...

void	ResetDeflate ()
	Reset a codec for another deflation session. More...

int	SetDictionary (byte[] dictionary)
	Set the dictionary to be used for either Inflation or Deflation. More...

Public Attributes
byte[]	InputBuffer
	The buffer from which data is taken. More...

int	NextIn
	An index into the InputBuffer array, indicating where to start reading. More...

int	AvailableBytesIn
	The number of bytes available in the InputBuffer, starting at NextIn. More...

long	TotalBytesIn
	Total number of bytes read so far, through all calls to Inflate()/Deflate(). More...

byte[]	OutputBuffer
	Buffer to store output data. More...

int	NextOut
	An index into the OutputBuffer array, indicating where to start writing. More...

int	AvailableBytesOut
	The number of bytes available in the OutputBuffer, starting at NextOut. More...

long	TotalBytesOut
	Total number of bytes written to the output so far, through all calls to Inflate()/Deflate(). More...

System.String	Message
	used for diagnostics, when something goes wrong! More...

CompressionLevel	CompressLevel = CompressionLevel.Default
	The compression level to use in this codec. Useful only in compression mode. More...

int	WindowBits = ZlibConstants.WindowBitsDefault
	The number of Window Bits to use. More...

Package Functions
int	Inflate (FlushType flush)
	Inflate the data in the InputBuffer, placing the result in the OutputBuffer. More...

int	Deflate (FlushType flush)
	Deflate one batch of data. More...

int	SetDeflateParams (CompressionLevel level, CompressionStrategy strategy)
	Set the CompressionStrategy and CompressionLevel for a deflation session. More...

void	flush_pending ()

int	read_buf (byte[] buf, int start, int size)

Package Attributes
DeflateManager	dstate

InflateManager	istate

uint	_Adler32

CompressionStrategy	Strategy = CompressionStrategy.Default
	The compression strategy to use. More...

Properties
int	Adler32 `[get]`
	The Adler32 checksum on the data transferred through the codec so far. You probably don't need to look at this. More...

Private Member Functions
int	_InternalInitializeDeflate (bool wantRfc1950Header)

Constructor & Destructor Documentation

Zlib.ZlibCodec.ZlibCodec ( )

inline

Create a ZlibCodec.

If you use this default constructor, you will later have to explicitly call InitializeInflate() or InitializeDeflate() before using the ZlibCodec to compress or decompress.

Zlib.ZlibCodec.ZlibCodec ( CompressionMode mode)

inline

Create a ZlibCodec that either compresses or decompresses.

Parameters

mode	Indicates whether the codec should compress (deflate) or decompress (inflate).

Member Function Documentation

int Zlib.ZlibCodec._InternalInitializeDeflate ( bool wantRfc1950Header)

inlineprivate

int Zlib.ZlibCodec.Deflate ( FlushType flush)

inlinepackage

Deflate one batch of data.

You must have set InputBuffer and OutputBuffer before calling this method.

private void DeflateBuffer(CompressionLevel level)
{
    int bufferSize = 1024;
    byte[] buffer = new byte[bufferSize];
    ZlibCodec compressor = new ZlibCodec();
    Console.WriteLine("\n============================================");
    Console.WriteLine("Size of Buffer to Deflate: {0} bytes.", UncompressedBytes.Length);
    MemoryStream ms = new MemoryStream();
    int rc = compressor.InitializeDeflate(level);
    compressor.InputBuffer = UncompressedBytes;
    compressor.NextIn = 0;
    compressor.AvailableBytesIn = UncompressedBytes.Length;
    compressor.OutputBuffer = buffer;
    // pass 1: deflate 
    do
    {
        compressor.NextOut = 0;
        compressor.AvailableBytesOut = buffer.Length;
        rc = compressor.Deflate(FlushType.None);
        if (rc != ZlibConstants.Z_OK &amp;&amp; rc != ZlibConstants.Z_STREAM_END)
            throw new Exception("deflating: " + compressor.Message);
        ms.Write(compressor.OutputBuffer, 0, buffer.Length - compressor.AvailableBytesOut);
    }
    while (compressor.AvailableBytesIn &gt; 0 || compressor.AvailableBytesOut == 0);
    // pass 2: finish and flush
    do
    {
        compressor.NextOut = 0;
        compressor.AvailableBytesOut = buffer.Length;
        rc = compressor.Deflate(FlushType.Finish);
        if (rc != ZlibConstants.Z_STREAM_END &amp;&amp; rc != ZlibConstants.Z_OK)
            throw new Exception("deflating: " + compressor.Message);
        if (buffer.Length - compressor.AvailableBytesOut &gt; 0)
            ms.Write(buffer, 0, buffer.Length - compressor.AvailableBytesOut);
    }
    while (compressor.AvailableBytesIn &gt; 0 || compressor.AvailableBytesOut == 0);
    compressor.EndDeflate();
    ms.Seek(0, SeekOrigin.Begin);
    CompressedBytes = new byte[compressor.TotalBytesOut];
    ms.Read(CompressedBytes, 0, CompressedBytes.Length);
}

Parameters

flush whether to flush all data as you deflate. Generally you will want to use Z_NO_FLUSH here, in a series of calls to Deflate(), and then call EndDeflate() to flush everything.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.EndDeflate ( )

inline

End a deflation session.

Call this after making a series of one or more calls to Deflate(). All buffers are flushed.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.EndInflate ( )

inline

Ends an inflation session.

Call this after successively calling Inflate(). This will cause all buffers to be flushed. After calling this you cannot call Inflate() without a intervening call to one of the InitializeInflate() overloads.

Returns: Z_OK if everything goes well.

void Zlib.ZlibCodec.flush_pending ( )

inlinepackage

int Zlib.ZlibCodec.Inflate ( FlushType flush)

inlinepackage

Inflate the data in the InputBuffer, placing the result in the OutputBuffer.

You must have set InputBuffer and OutputBuffer, NextIn and NextOut, and AvailableBytesIn and AvailableBytesOut before calling this method.

private void InflateBuffer()
{
    int bufferSize = 1024;
    byte[] buffer = new byte[bufferSize];
    ZlibCodec decompressor = new ZlibCodec();
    Console.WriteLine("\n============================================");
    Console.WriteLine("Size of Buffer to Inflate: {0} bytes.", CompressedBytes.Length);
    MemoryStream ms = new MemoryStream(DecompressedBytes);
    int rc = decompressor.InitializeInflate();
    decompressor.InputBuffer = CompressedBytes;
    decompressor.NextIn = 0;
    decompressor.AvailableBytesIn = CompressedBytes.Length;
    decompressor.OutputBuffer = buffer;
    // pass 1: inflate 
    do
    {
        decompressor.NextOut = 0;
        decompressor.AvailableBytesOut = buffer.Length;
        rc = decompressor.Inflate(FlushType.None);
        if (rc != ZlibConstants.Z_OK &amp;&amp; rc != ZlibConstants.Z_STREAM_END)
            throw new Exception("inflating: " + decompressor.Message);
        ms.Write(decompressor.OutputBuffer, 0, buffer.Length - decompressor.AvailableBytesOut);
    }
    while (decompressor.AvailableBytesIn &gt; 0 || decompressor.AvailableBytesOut == 0);
    // pass 2: finish and flush
    do
    {
        decompressor.NextOut = 0;
        decompressor.AvailableBytesOut = buffer.Length;
        rc = decompressor.Inflate(FlushType.Finish);
        if (rc != ZlibConstants.Z_STREAM_END &amp;&amp; rc != ZlibConstants.Z_OK)
            throw new Exception("inflating: " + decompressor.Message);
        if (buffer.Length - decompressor.AvailableBytesOut &gt; 0)
            ms.Write(buffer, 0, buffer.Length - decompressor.AvailableBytesOut);
    }
    while (decompressor.AvailableBytesIn &gt; 0 || decompressor.AvailableBytesOut == 0);
    decompressor.EndInflate();
}

Parameters

flush The flush to use when inflating.

Returns: Z_OK if everything goes well.

int Zlib.ZlibCodec.InitializeDeflate ( )

inline

Initialize the ZlibCodec for deflation operation.

The codec will use the MAX window bits and the default level of compression.

int bufferSize = 40000;
byte[] CompressedBytes = new byte[bufferSize];
byte[] DecompressedBytes = new byte[bufferSize];
ZlibCodec compressor = new ZlibCodec();
compressor.InitializeDeflate(CompressionLevel.Default);
compressor.InputBuffer = System.Text.ASCIIEncoding.ASCII.GetBytes(TextToCompress);
compressor.NextIn = 0;
compressor.AvailableBytesIn = compressor.InputBuffer.Length;
compressor.OutputBuffer = CompressedBytes;
compressor.NextOut = 0;
compressor.AvailableBytesOut = CompressedBytes.Length;
while (compressor.TotalBytesIn != TextToCompress.Length &amp;&amp; compressor.TotalBytesOut &lt; bufferSize)
{
  compressor.Deflate(FlushType.None);
}
while (true)
{
  int rc= compressor.Deflate(FlushType.Finish);
  if (rc == ZlibConstants.Z_STREAM_END) break;
}
compressor.EndDeflate();

Returns: Z_OK if all goes well. You generally don't need to check the return code.

int Zlib.ZlibCodec.InitializeDeflate ( CompressionLevel level)

inline

Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel.

The codec will use the maximum window bits (15) and the specified CompressionLevel. It will emit a ZLIB stream as it compresses.

Parameters

level The compression level for the codec.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.InitializeDeflate	(	CompressionLevel	level,
		bool	wantRfc1950Header
	)

inline

Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel, and the explicit flag governing whether to emit an RFC1950 header byte pair.

The codec will use the maximum window bits (15) and the specified CompressionLevel. If you want to generate a zlib stream, you should specify true for wantRfc1950Header. In this case, the library will emit a ZLIB header, as defined in RFC 1950

, in the compressed stream.

Parameters

level	The compression level for the codec.
wantRfc1950Header	whether to emit an initial RFC1950 byte pair in the compressed stream.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.InitializeDeflate	(	CompressionLevel	level,
		int	bits
	)

inline

Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel, and the specified number of window bits.

The codec will use the specified number of window bits and the specified CompressionLevel.

Parameters

level	The compression level for the codec.
bits	the number of window bits to use. If you don't know what this means, don't use this method.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.InitializeDeflate	(	CompressionLevel	level,
		int	bits,
		bool	wantRfc1950Header
	)

inline

Initialize the ZlibCodec for deflation operation, using the specified CompressionLevel, the specified number of window bits, and the explicit flag governing whether to emit an RFC1950 header byte pair.

Parameters

level	The compression level for the codec.
wantRfc1950Header	whether to emit an initial RFC1950 byte pair in the compressed stream.
bits	the number of window bits to use. If you don't know what this means, don't use this method.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.InitializeInflate ( )

inline

Initialize the inflation state.

It is not necessary to call this before using the ZlibCodec to inflate data; It is implicitly called when you call the constructor.

Returns: Z_OK if everything goes well.

int Zlib.ZlibCodec.InitializeInflate ( bool expectRfc1950Header)

inline

Initialize the inflation state with an explicit flag to govern the handling of RFC1950 header bytes.

By default, the ZLIB header defined in RFC 1950

is expected. If you want to read a zlib stream you should specify true for expectRfc1950Header. If you have a deflate stream, you will want to specify false. It is only necessary to invoke this initializer explicitly if you want to specify false.

Parameters

expectRfc1950Header whether to expect an RFC1950 header byte pair when reading the stream of data to be inflated.

Returns: Z_OK if everything goes well.

int Zlib.ZlibCodec.InitializeInflate ( int windowBits)

inline

Initialize the ZlibCodec for inflation, with the specified number of window bits.

Parameters

windowBits The number of window bits to use. If you need to ask what that is, then you shouldn't be calling this initializer.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.InitializeInflate	(	int	windowBits,
		bool	expectRfc1950Header
	)

inline

Initialize the inflation state with an explicit flag to govern the handling of RFC1950 header bytes.

If you want to read a zlib stream you should specify true for expectRfc1950Header. In this case, the library will expect to find a ZLIB header, as defined in RFC 1950

, in the compressed stream. If you will be reading a DEFLATE or GZIP stream, which does not have such a header, you will want to specify false.

Parameters

expectRfc1950Header	whether to expect an RFC1950 header byte pair when reading the stream of data to be inflated.
windowBits	The number of window bits to use. If you need to ask what that is, then you shouldn't be calling this initializer.

Returns: Z_OK if everything goes well.

int Zlib.ZlibCodec.read_buf	(	byte[]	buf,
		int	start,
		int	size
	)

inlinepackage

void Zlib.ZlibCodec.ResetDeflate ( )

inline

Reset a codec for another deflation session.

Call this to reset the deflation state. For example if a thread is deflating non-consecutive blocks, you can call Reset() after the Deflate(Sync) of the first block and before the next Deflate(None) of the second block.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.SetDeflateParams	(	CompressionLevel	level,
		CompressionStrategy	strategy
	)

inlinepackage

Set the CompressionStrategy and CompressionLevel for a deflation session.

Parameters

level	the level of compression to use.
strategy	the strategy to use for compression.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.SetDictionary ( byte[] dictionary)

inline

Set the dictionary to be used for either Inflation or Deflation.

Parameters

dictionary The dictionary bytes to use.

Returns: Z_OK if all goes well.

int Zlib.ZlibCodec.SyncInflate ( )

inline

I don't know what this does!

Returns: Z_OK if everything goes well.

Member Data Documentation

uint Zlib.ZlibCodec._Adler32

package

int Zlib.ZlibCodec.AvailableBytesIn

The number of bytes available in the InputBuffer, starting at NextIn.

Generally you should set this to InputBuffer.Length before the first Inflate() or Deflate() call. The class will update this number as calls to Inflate/Deflate are made.

int Zlib.ZlibCodec.AvailableBytesOut

The number of bytes available in the OutputBuffer, starting at NextOut.

Generally you should set this to OutputBuffer.Length before the first Inflate() or Deflate() call. The class will update this number as calls to Inflate/Deflate are made.

CompressionLevel Zlib.ZlibCodec.CompressLevel = CompressionLevel.Default

The compression level to use in this codec. Useful only in compression mode.

DeflateManager Zlib.ZlibCodec.dstate

package

byte [] Zlib.ZlibCodec.InputBuffer

The buffer from which data is taken.

InflateManager Zlib.ZlibCodec.istate

package

System.String Zlib.ZlibCodec.Message

used for diagnostics, when something goes wrong!

int Zlib.ZlibCodec.NextIn

An index into the InputBuffer array, indicating where to start reading.

int Zlib.ZlibCodec.NextOut

An index into the OutputBuffer array, indicating where to start writing.

byte [] Zlib.ZlibCodec.OutputBuffer

Buffer to store output data.

CompressionStrategy Zlib.ZlibCodec.Strategy = CompressionStrategy.Default

package

The compression strategy to use.

This is only effective in compression. The theory offered by ZLIB is that different strategies could potentially produce significant differences in compression behavior for different data sets. Unfortunately I don't have any good recommendations for how to set it differently. When I tested changing the strategy I got minimally different compression performance. It's best to leave this property alone if you don't have a good feel for it. Or, you may want to produce a test harness that runs through the different strategy options and evaluates them on different file types. If you do that, let me know your results.

long Zlib.ZlibCodec.TotalBytesIn

Total number of bytes read so far, through all calls to Inflate()/Deflate().

long Zlib.ZlibCodec.TotalBytesOut

Total number of bytes written to the output so far, through all calls to Inflate()/Deflate().

int Zlib.ZlibCodec.WindowBits = ZlibConstants.WindowBitsDefault

The number of Window Bits to use.

This gauges the size of the sliding window, and hence the compression effectiveness as well as memory consumption. It's best to just leave this setting alone if you don't know what it is. The maximum value is 15 bits, which implies a 32k window.

Property Documentation

int Zlib.ZlibCodec.Adler32

get

The Adler32 checksum on the data transferred through the codec so far. You probably don't need to look at this.

Detailed Description

Public Member Functions

Public Attributes

Package Functions

Package Attributes

Properties

Private Member Functions

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation

Property Documentation