Class ZlibCodec

Namespace

Ionic.Zlib

Assembly

SunamoDotNetZip.dll

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

[Guid("ebc25cf6-9120-4283-b972-0e5520d0000D")]
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.AutoDispatch)]
public sealed class ZlibCodec

Inheritance

object

ZlibCodec

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Extension Methods

FuncExtensions.AsFuncFast<T>(T)

FuncExtensions.AsFunc<T>(T)

ObjectExtensions.GetStackTrace(object)

ReClasser.FixMeUp(object)

Remarks

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.

Constructors

ZlibCodec()

Create a ZlibCodec.

public ZlibCodec()

Remarks

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

ZlibCodec(CompressionMode)

Create a ZlibCodec that either compresses or decompresses.

public ZlibCodec(CompressionMode mode)

Parameters

mode CompressionMode

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

Fields

AvailableBytesIn

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

public int AvailableBytesIn

Field Value

int

Remarks

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.

AvailableBytesOut

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

public int AvailableBytesOut

Field Value

int

Remarks

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.

CompressLevel

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

public CompressionLevel CompressLevel

Field Value

CompressionLevel

InputBuffer

The buffer from which data is taken.

public byte[] InputBuffer

Field Value

byte[]

Message

used for diagnostics, when something goes wrong!

public string Message

Field Value

string

NextIn

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

public int NextIn

Field Value

int

NextOut

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

public int NextOut

Field Value

int

OutputBuffer

Buffer to store output data.

public byte[] OutputBuffer

Field Value

byte[]

Strategy

The compression strategy to use.

public CompressionStrategy Strategy

Field Value

CompressionStrategy

Remarks

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.

TotalBytesIn

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

public long TotalBytesIn

Field Value

long

TotalBytesOut

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

public long TotalBytesOut

Field Value

long

WindowBits

The number of Window Bits to use.

public int WindowBits

Field Value

int

Remarks

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.

Properties

Adler32

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

public int Adler32 { get; }

Property Value

int

Methods

Deflate(FlushType)

Deflate one batch of data.

public int Deflate(FlushType flush)

Parameters

flush FlushType

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

int

Z_OK if all goes well.

Examples

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 && rc != ZlibConstants.Z_STREAM_END)
            throw new Exception("deflating: " + compressor.Message);

        ms.Write(compressor.OutputBuffer, 0, buffer.Length - compressor.AvailableBytesOut);
    }
    while (compressor.AvailableBytesIn > 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 && rc != ZlibConstants.Z_OK)
            throw new Exception("deflating: " + compressor.Message);

        if (buffer.Length - compressor.AvailableBytesOut > 0)
            ms.Write(buffer, 0, buffer.Length - compressor.AvailableBytesOut);
    }
    while (compressor.AvailableBytesIn > 0 || compressor.AvailableBytesOut == 0);

    compressor.EndDeflate();

    ms.Seek(0, SeekOrigin.Begin);
    CompressedBytes = new byte[compressor.TotalBytesOut];
    ms.Read(CompressedBytes, 0, CompressedBytes.Length);
}

Remarks

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

EndDeflate()

End a deflation session.

public int EndDeflate()

Returns

int

Z_OK if all goes well.

Remarks

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

EndInflate()

Ends an inflation session.

public int EndInflate()

Returns

int

Z_OK if everything goes well.

Remarks

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.

Inflate()

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

public int Inflate()

Returns

int

Z_OK if everything goes well.

Examples

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 && rc != ZlibConstants.Z_STREAM_END)
            throw new Exception("inflating: " + decompressor.Message);

        ms.Write(decompressor.OutputBuffer, 0, buffer.Length - decompressor.AvailableBytesOut);
    }
    while (decompressor.AvailableBytesIn > 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 && rc != ZlibConstants.Z_OK)
            throw new Exception("inflating: " + decompressor.Message);

        if (buffer.Length - decompressor.AvailableBytesOut > 0)
            ms.Write(buffer, 0, buffer.Length - decompressor.AvailableBytesOut);
    }
    while (decompressor.AvailableBytesIn > 0 || decompressor.AvailableBytesOut == 0);

    decompressor.EndInflate();
}

Remarks

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

InitializeDeflate()

Initialize the ZlibCodec for deflation operation.

public int InitializeDeflate()

Returns

int

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

Examples

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 && compressor.TotalBytesOut < bufferSize)
{
  compressor.Deflate(FlushType.None);
}

while (true)
{
  int rc= compressor.Deflate(FlushType.Finish);
  if (rc == ZlibConstants.Z_STREAM_END) break;
}

compressor.EndDeflate();

Remarks

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

InitializeDeflate(CompressionLevel)

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

public int InitializeDeflate(CompressionLevel level)

Parameters

level CompressionLevel

The compression level for the codec.

Returns

int

Z_OK if all goes well.

Remarks

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

InitializeDeflate(CompressionLevel, bool)

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

public int InitializeDeflate(CompressionLevel level, bool wantRfc1950Header)

Parameters

level CompressionLevel

The compression level for the codec.

wantRfc1950Header bool

whether to emit an initial RFC1950 byte pair in the compressed stream.

Returns

int

Z_OK if all goes well.

Remarks

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.

InitializeDeflate(CompressionLevel, int)

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

public int InitializeDeflate(CompressionLevel level, int bits)

Parameters

level CompressionLevel

The compression level for the codec.

bits int

the number of window bits to use. If you don't know what this means, don't use this method.

Returns

int

Z_OK if all goes well.

Remarks

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

InitializeDeflate(CompressionLevel, int, bool)

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.

public int InitializeDeflate(CompressionLevel level, int bits, bool wantRfc1950Header)

Parameters

level CompressionLevel

The compression level for the codec.

bits int

the number of window bits to use. If you don't know what this means, don't use this method.

wantRfc1950Header bool

whether to emit an initial RFC1950 byte pair in the compressed stream.

Returns

int

Z_OK if all goes well.

InitializeInflate()

Initialize the inflation state.

public int InitializeInflate()

Returns

int

Z_OK if everything goes well.

Remarks

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

InitializeInflate(bool)

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

public int InitializeInflate(bool expectRfc1950Header)

Parameters

expectRfc1950Header bool

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

Returns

int

Z_OK if everything goes well.

Remarks

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.

InitializeInflate(int)

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

public int InitializeInflate(int windowBits)

Parameters

windowBits int

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

Returns

int

Z_OK if all goes well.

InitializeInflate(int, bool)

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

public int InitializeInflate(int windowBits, bool expectRfc1950Header)

Parameters

windowBits int

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

expectRfc1950Header bool

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

Returns

int

Z_OK if everything goes well.

Remarks

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.

ResetDeflate()

Reset a codec for another deflation session.

public void ResetDeflate()

Remarks

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.

SetDeflateParams(CompressionLevel, CompressionStrategy)

Set the CompressionStrategy and CompressionLevel for a deflation session.

public int SetDeflateParams(CompressionLevel level, CompressionStrategy strategy)

Parameters

level CompressionLevel

the level of compression to use.

strategy CompressionStrategy

the strategy to use for compression.

Returns

int

Z_OK if all goes well.

SetDictionary(byte[])

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

public int SetDictionary(byte[] dictionary)

Parameters

dictionary byte[]

The dictionary bytes to use.

Returns

int

Z_OK if all goes well.

SetDictionaryUnconditionally(byte[])

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

public int SetDictionaryUnconditionally(byte[] dictionary)

Parameters

dictionary byte[]

The dictionary bytes to use.

Returns

int

Z_OK if all goes well.

Remarks

Decoding a MSZip file requires the dictionary state to be set unconditionally at the end of each block to the previous decoded data

SyncInflate()

I don't know what this does!

public int SyncInflate()

Returns

int

Z_OK if everything goes well.