Class DeflateStream

A class for compressing and decompressing streams using the Deflate algorithm.

Inheritance

System.Object

System.MarshalByRefObject

System.IO.Stream

DeflateStream

Implements

System.IAsyncDisposable

System.IDisposable

Inherited Members

System.IO.Stream.Null

System.IO.Stream.BeginRead(System.Byte[], System.Int32, System.Int32, System.AsyncCallback, System.Object)

System.IO.Stream.BeginWrite(System.Byte[], System.Int32, System.Int32, System.AsyncCallback, System.Object)

System.IO.Stream.Close()

System.IO.Stream.CopyTo(System.IO.Stream)

System.IO.Stream.CopyTo(System.IO.Stream, System.Int32)

System.IO.Stream.CopyToAsync(System.IO.Stream)

System.IO.Stream.CopyToAsync(System.IO.Stream, System.Int32)

System.IO.Stream.CopyToAsync(System.IO.Stream, System.Int32, System.Threading.CancellationToken)

System.IO.Stream.CopyToAsync(System.IO.Stream, System.Threading.CancellationToken)

System.IO.Stream.CreateWaitHandle()

System.IO.Stream.Dispose()

System.IO.Stream.DisposeAsync()

System.IO.Stream.EndRead(System.IAsyncResult)

System.IO.Stream.EndWrite(System.IAsyncResult)

System.IO.Stream.FlushAsync()

System.IO.Stream.FlushAsync(System.Threading.CancellationToken)

System.IO.Stream.ObjectInvariant()

System.IO.Stream.Read(System.Span<System.Byte>)

System.IO.Stream.ReadAsync(System.Byte[], System.Int32, System.Int32)

System.IO.Stream.ReadAsync(System.Byte[], System.Int32, System.Int32, System.Threading.CancellationToken)

System.IO.Stream.ReadAsync(System.Memory<System.Byte>, System.Threading.CancellationToken)

System.IO.Stream.ReadByte()

System.IO.Stream.Synchronized(System.IO.Stream)

System.IO.Stream.Write(System.ReadOnlySpan<System.Byte>)

System.IO.Stream.WriteAsync(System.Byte[], System.Int32, System.Int32)

System.IO.Stream.WriteAsync(System.Byte[], System.Int32, System.Int32, System.Threading.CancellationToken)

System.IO.Stream.WriteAsync(System.ReadOnlyMemory<System.Byte>, System.Threading.CancellationToken)

System.IO.Stream.WriteByte(System.Byte)

System.IO.Stream.CanTimeout

System.IO.Stream.ReadTimeout

System.IO.Stream.WriteTimeout

System.MarshalByRefObject.GetLifetimeService()

System.MarshalByRefObject.InitializeLifetimeService()

System.MarshalByRefObject.MemberwiseClone(System.Boolean)

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

System.Object.ToString()

Namespace: OfficeOpenXml.Packaging.Ionic.Zlib

Assembly: EPPlus.dll

Syntax

public class DeflateStream : Stream, IAsyncDisposable, IDisposable

Remarks

The DeflateStream is a Decorator on a System.IO.Stream. It adds DEFLATE compression or decompression to any stream.

Using this stream, applications can compress or decompress data via stream Read and Write operations. Either compresssion or decompression can occur through either reading or writing. The compression format used is DEFLATE, which is documented in IETF RFC 1951, "DEFLATE Compressed Data Format Specification version 1.3.".

This class is similar to ZlibStream, except that ZlibStream adds the RFC 1950 - ZLIB framing bytes to a compressed stream when compressing, or expects the RFC1950 framing bytes when decompressing. The DeflateStream does not.

Constructors

DeflateStream(Stream, CompressionMode)

Create a DeflateStream using the specified CompressionMode.

Declaration

public DeflateStream(Stream stream, CompressionMode mode)

Parameters

Type	Name	Description
System.IO.Stream	stream	The stream which will be read or written.
CompressionMode	mode	Indicates whether the DeflateStream will compress or decompress.

Remarks

When mode is CompressionMode.Compress, the DeflateStream will use the default compression level. The "captive" stream will be closed when the DeflateStream is closed.

Examples

This example uses a DeflateStream to compress data from a file, and writes the compressed data to another file.

using (System.IO.Stream input = System.IO.File.OpenRead(fileToCompress))
{
    using (var raw = System.IO.File.Create(fileToCompress + ".deflated"))
    {
        using (Stream compressor = new DeflateStream(raw, CompressionMode.Compress))
        {
            byte[] buffer = new byte[WORKING_BUFFER_SIZE];
            int n;
            while ((n= input.Read(buffer, 0, buffer.Length)) != 0)
            {
                compressor.Write(buffer, 0, n);
            }
        }
    }
}

Using input As Stream = File.OpenRead(fileToCompress)
    Using raw As FileStream = File.Create(fileToCompress & ".deflated")
        Using compressor As Stream = New DeflateStream(raw, CompressionMode.Compress)
            Dim buffer As Byte() = New Byte(4096) {}
            Dim n As Integer = -1
            Do While (n <> 0)
                If (n > 0) Then
                    compressor.Write(buffer, 0, n)
                End If
                n = input.Read(buffer, 0, buffer.Length)
            Loop
        End Using
    End Using
End Using

DeflateStream(Stream, CompressionMode, CompressionLevel)

Create a DeflateStream using the specified CompressionMode and the specified CompressionLevel.

Declaration

public DeflateStream(Stream stream, CompressionMode mode, CompressionLevel level)

Parameters

Type	Name	Description
System.IO.Stream	stream	The stream to be read or written while deflating or inflating.
CompressionMode	mode	Indicates whether the `DeflateStream` will compress or decompress.
CompressionLevel	level	A tuning knob to trade speed for effectiveness.

Remarks

When mode is CompressionMode.Decompress, the level parameter is ignored. The "captive" stream will be closed when the DeflateStream is closed.

Examples

This example uses a DeflateStream to compress data from a file, and writes the compressed data to another file.

using (System.IO.Stream input = System.IO.File.OpenRead(fileToCompress))
{
    using (var raw = System.IO.File.Create(fileToCompress + ".deflated"))
    {
        using (Stream compressor = new DeflateStream(raw,
                                                     CompressionMode.Compress,
                                                     CompressionLevel.BestCompression))
        {
            byte[] buffer = new byte[WORKING_BUFFER_SIZE];
            int n= -1;
            while (n != 0)
            {
                if (n > 0)
                    compressor.Write(buffer, 0, n);
                n= input.Read(buffer, 0, buffer.Length);
            }
        }
    }
}

Using input As Stream = File.OpenRead(fileToCompress)
    Using raw As FileStream = File.Create(fileToCompress & ".deflated")
        Using compressor As Stream = New DeflateStream(raw, CompressionMode.Compress, CompressionLevel.BestCompression)
            Dim buffer As Byte() = New Byte(4096) {}
            Dim n As Integer = -1
            Do While (n <> 0)
                If (n > 0) Then
                    compressor.Write(buffer, 0, n)
                End If
                n = input.Read(buffer, 0, buffer.Length)
            Loop
        End Using
    End Using
End Using

DeflateStream(Stream, CompressionMode, CompressionLevel, Boolean)

Create a DeflateStream using the specified CompressionMode and the specified CompressionLevel, and explicitly specify whether the stream should be left open after Deflation or Inflation.

Declaration

public DeflateStream(Stream stream, CompressionMode mode, CompressionLevel level, bool leaveOpen)

Parameters

Type	Name	Description
System.IO.Stream	stream	The stream which will be read or written.
CompressionMode	mode	Indicates whether the DeflateStream will compress or decompress.
CompressionLevel	level	A tuning knob to trade speed for effectiveness.
System.Boolean	leaveOpen	true if the application would like the stream to remain open after inflation/deflation.

Remarks

When mode is CompressionMode.Decompress, the level parameter is ignored.

This constructor allows the application to request that the captive stream remain open after the deflation or inflation occurs. By default, after Close() is called on the stream, the captive stream is also closed. In some cases this is not desired, for example if the stream is a System.IO.MemoryStream that will be re-read after compression. Specify true for the leaveOpen parameter to leave the stream open.

Examples

This example shows how to use a DeflateStream to compress data from a file, and store the compressed data into another file.

using (var output = System.IO.File.Create(fileToCompress + ".deflated"))
{
    using (System.IO.Stream input = System.IO.File.OpenRead(fileToCompress))
    {
        using (Stream compressor = new DeflateStream(output, CompressionMode.Compress, CompressionLevel.BestCompression, true))
        {
            byte[] buffer = new byte[WORKING_BUFFER_SIZE];
            int n= -1;
            while (n != 0)
            {
                if (n > 0)
                    compressor.Write(buffer, 0, n);
                n= input.Read(buffer, 0, buffer.Length);
            }
        }
    }
    // can write additional data to the output stream here
}

Using output As FileStream = File.Create(fileToCompress & ".deflated")
    Using input As Stream = File.OpenRead(fileToCompress)
        Using compressor As Stream = New DeflateStream(output, CompressionMode.Compress, CompressionLevel.BestCompression, True)
            Dim buffer As Byte() = New Byte(4096) {}
            Dim n As Integer = -1
            Do While (n <> 0)
                If (n > 0) Then
                    compressor.Write(buffer, 0, n)
                End If
                n = input.Read(buffer, 0, buffer.Length)
            Loop
        End Using
    End Using
    ' can write additional data to the output stream here.
End Using

DeflateStream(Stream, CompressionMode, Boolean)

Create a DeflateStream using the specified CompressionMode, and explicitly specify whether the stream should be left open after Deflation or Inflation.

Declaration

public DeflateStream(Stream stream, CompressionMode mode, bool leaveOpen)

Parameters

Type	Name	Description
System.IO.Stream	stream	The stream which will be read or written. This is called the "captive" stream in other places in this documentation.
CompressionMode	mode	Indicates whether the `DeflateStream` will compress or decompress.
System.Boolean	leaveOpen	true if the application would like the stream to remain open after inflation/deflation.

Remarks

This constructor allows the application to request that the captive stream remain open after the deflation or inflation occurs. By default, after Close() is called on the stream, the captive stream is also closed. In some cases this is not desired, for example if the stream is a memory stream that will be re-read after compression. Specify true for the leaveOpen parameter to leave the stream open.

The DeflateStream will use the default compression level.

See the other overloads of this constructor for example code.

Properties

BufferSize

The size of the working buffer for the compression codec.

Declaration

public int BufferSize { get; set; }

Property Value

Type	Description
System.Int32

Remarks

The working buffer is used for all stream operations. The default size is 1024 bytes. The minimum size is 128 bytes. You may get better performance with a larger buffer. Then again, you might not. You would have to test it.

Set this before the first call to Read() or Write() on the stream. If you try to set it afterwards, it will throw.

CanRead

Indicates whether the stream can be read.

Declaration

public override bool CanRead { get; }

Property Value

Type	Description
System.Boolean

Overrides

System.IO.Stream.CanRead

Remarks

The return value depends on whether the captive stream supports reading.

CanSeek

Indicates whether the stream supports Seek operations.

Declaration

public override bool CanSeek { get; }

Property Value

Type	Description
System.Boolean

Overrides

System.IO.Stream.CanSeek

Remarks

Always returns false.

CanWrite

Indicates whether the stream can be written.

Declaration

public override bool CanWrite { get; }

Property Value

Type	Description
System.Boolean

Overrides

System.IO.Stream.CanWrite

Remarks

The return value depends on whether the captive stream supports writing.

FlushMode

This property sets the flush behavior on the stream.

Declaration

public virtual FlushType FlushMode { get; set; }

Property Value

Type	Description
FlushType

Remarks

See the ZLIB documentation for the meaning of the flush behavior.

Length

Reading this property always throws a System.NotImplementedException.

Declaration

public override long Length { get; }

Property Value

Type	Description
System.Int64

Overrides

System.IO.Stream.Length

Position

The position of the stream pointer.

Declaration

public override long Position { get; set; }

Property Value

Type	Description
System.Int64

Overrides

System.IO.Stream.Position

Remarks

Setting this property always throws a System.NotImplementedException. Reading will return the total bytes written out, if used in writing, or the total bytes read in, if used in reading. The count may refer to compressed bytes or uncompressed bytes, depending on how you've used the stream.

Strategy

The ZLIB strategy to be used during compression.

Declaration

public CompressionStrategy Strategy { get; set; }

Property Value

Type	Description
CompressionStrategy

Remarks

By tweaking this parameter, you may be able to optimize the compression for data with particular characteristics.

TotalIn

Returns the total number of bytes input so far.

Declaration

public virtual long TotalIn { get; }

Property Value

Type	Description
System.Int64

TotalOut

Returns the total number of bytes output so far.

Declaration

public virtual long TotalOut { get; }

Property Value

Type	Description
System.Int64

Methods

CompressBuffer(Byte[])

Compress a byte array into a new byte array using DEFLATE.

Declaration

public static byte[] CompressBuffer(byte[] b)

Parameters

Type	Name	Description
System.Byte[]	b	A buffer to compress.

Returns

Type	Description
System.Byte[]	The data in compressed form

Remarks

Uncompress it with UncompressBuffer(Byte[]).

CompressString(String)

Compress a string into a byte array using DEFLATE (RFC 1951).

Declaration

public static byte[] CompressString(string s)

Parameters

Type	Name	Description
System.String	s	A string to compress. The string will first be encoded using UTF8, then compressed.

Returns

Type	Description
System.Byte[]	The string in compressed form

Remarks

Uncompress it with UncompressString(Byte[]).

Dispose(Boolean)

Dispose the stream.

Declaration

protected override void Dispose(bool disposing)

Parameters

Type	Name	Description
System.Boolean	disposing	true if the Dispose method was invoked by user code.

Overrides

System.IO.Stream.Dispose(System.Boolean)

Remarks

This may or may not result in a Close() call on the captive stream. See the constructors that have a leaveOpen parameter for more information.

Application code won't call this code directly. This method may be invoked in two distinct scenarios. If disposing == true, the method has been called directly or indirectly by a user's code, for example via the public Dispose() method. In this case, both managed and unmanaged resources can be referenced and disposed. If disposing == false, the method has been called by the runtime from inside the object finalizer and this method should not reference other objects; in that case only unmanaged resources must be referenced or disposed.

Flush()

Flush the stream.

Declaration

public override void Flush()

Overrides

System.IO.Stream.Flush()

Read(Byte[], Int32, Int32)

Read data from the stream.

Declaration

public override int Read(byte[] buffer, int offset, int count)

Parameters

Type	Name	Description
System.Byte[]	buffer	The buffer into which the read data should be placed.
System.Int32	offset	the offset within that data array to put the first byte read.
System.Int32	count	the number of bytes to read.

Returns

Type	Description
System.Int32	the number of bytes actually read

Overrides

System.IO.Stream.Read(System.Byte[], System.Int32, System.Int32)

Remarks

If you wish to use the DeflateStream to compress data while reading, you can create a DeflateStream with CompressionMode.Compress, providing an uncompressed data stream. Then call Read() on that DeflateStream, and the data read will be compressed as you read. If you wish to use the DeflateStream to decompress data while reading, you can create a DeflateStream with CompressionMode.Decompress, providing a readable compressed data stream. Then call Read() on that DeflateStream, and the data read will be decompressed as you read.

A DeflateStream can be used for Read() or Write(), but not both.

Seek(Int64, SeekOrigin)

Calling this method always throws a System.NotImplementedException.

Declaration

public override long Seek(long offset, SeekOrigin origin)

Parameters

Type	Name	Description
System.Int64	offset	this is irrelevant, since it will always throw!
System.IO.SeekOrigin	origin	this is irrelevant, since it will always throw!

Returns

Type	Description
System.Int64	irrelevant!

Overrides

System.IO.Stream.Seek(System.Int64, System.IO.SeekOrigin)

SetLength(Int64)

Calling this method always throws a System.NotImplementedException.

Declaration

public override void SetLength(long value)

Parameters

Type	Name	Description
System.Int64	value	this is irrelevant, since it will always throw!

Overrides

System.IO.Stream.SetLength(System.Int64)

UncompressBuffer(Byte[])

Uncompress a DEFLATE'd byte array into a byte array.

Declaration

public static byte[] UncompressBuffer(byte[] compressed)

Parameters

Type	Name	Description
System.Byte[]	compressed	A buffer containing data that has been compressed with DEFLATE.

Returns

Type	Description
System.Byte[]	The data in uncompressed form

UncompressString(Byte[])

Uncompress a DEFLATE'd byte array into a single string.

Declaration

public static string UncompressString(byte[] compressed)

Parameters

Type	Name	Description
System.Byte[]	compressed	A buffer containing DEFLATE-compressed data.

Returns

Type	Description
System.String	The uncompressed string

Write(Byte[], Int32, Int32)

Write data to the stream.

Declaration

public override void Write(byte[] buffer, int offset, int count)

Parameters

Type	Name	Description
System.Byte[]	buffer	The buffer holding data to write to the stream.
System.Int32	offset	the offset within that data array to find the first byte to write.
System.Int32	count	the number of bytes to write.

Overrides

System.IO.Stream.Write(System.Byte[], System.Int32, System.Int32)

Remarks

If you wish to use the DeflateStream to compress data while writing, you can create a DeflateStream with CompressionMode.Compress, and a writable output stream. Then call Write() on that DeflateStream, providing uncompressed data as input. The data sent to the output stream will be the compressed form of the data written. If you wish to use the DeflateStream to decompress data while writing, you can create a DeflateStream with CompressionMode.Decompress, and a writable output stream. Then call Write() on that stream, providing previously compressed data. The data sent to the output stream will be the decompressed form of the data written.

A DeflateStream can be used for Read() or Write(), but not both.

Implements

System.IAsyncDisposable

System.IDisposable

Class DeflateStream

Inheritance

Implements

Inherited Members

Namespace: OfficeOpenXml.Packaging.Ionic.Zlib

Assembly: EPPlus.dll

Syntax

Remarks

Constructors

DeflateStream(Stream, CompressionMode)

Declaration

Parameters

Remarks

Examples

DeflateStream(Stream, CompressionMode, CompressionLevel)

Declaration

Parameters

Remarks

Examples

DeflateStream(Stream, CompressionMode, CompressionLevel, Boolean)

Declaration

Parameters

Remarks

Examples

DeflateStream(Stream, CompressionMode, Boolean)

Declaration

Parameters

Remarks

Properties

BufferSize

Declaration

Property Value

Remarks

CanRead

Declaration

Property Value

Overrides

Remarks

CanSeek

Declaration

Property Value

Overrides

Remarks

CanWrite

Declaration

Property Value

Overrides

Remarks

FlushMode

Declaration

Property Value

Remarks

Length

Declaration

Property Value

Overrides

Position

Declaration

Property Value

Overrides

Remarks

Strategy

Declaration

Property Value

Remarks

TotalIn

Declaration

Property Value

TotalOut

Declaration

Property Value

Methods

CompressBuffer(Byte[])

Declaration

Parameters

Returns

Remarks

See Also

CompressString(String)

Declaration