DeflateStream

[Flpit]

Hi,

Can anybody tell me how to use the System.IO.Compr ession

Deflatestream Class.

I have a byte[] which is a compressed set of bytes that form a block.

I want to inflate the byte[] and return the new inflated byte[].

public static byte[] Deflate(byte[] c_block)
{
MemoryStream ms = new MemoryStream(c_ block);
DeflateStream zlib = new DeflateStream (ms,Compression Mode.Decompress );
zlib.Read(d_blo ck,0,??);
// Close the stream.
zlib.Close();
ms.Close();
return d_block;
}

Is this the right approach ?? If so, how can I tell the size of the inflated array d_block for the zlib.Read method. Can somebody provide some guidance.

Thanks

Phill

[AricC]

From MSDN

Imports System
Imports System.IO
Imports System.IO.Compression
 
 
 
Public Class DeflateTest
    Shared msg As String
   Public Shared Function ReadAllBytesFromStream(stream As Stream, buffer() As Byte) As Integer
      ' Use this method is used to read all bytes from a stream.
      Dim offset As Integer = 0
      Dim totalCount As Integer = 0
      While True
         Dim bytesRead As Integer = stream.Read(buffer, offset, 100)
         If bytesRead = 0 Then
            Exit While
         End If
         offset += bytesRead
         totalCount += bytesRead
      End While
      Return totalCount
   End Function 'ReadAllBytesFromStream
 
 
   Public Shared Function CompareData(buf1() As Byte, len1 As Integer, buf2() As Byte, len2 As Integer) As Boolean
      ' Use this method to compare data from two different buffers.
        If len1 <> len2 Then
            msg = "Number of bytes in two buffer are different" & len1 & ":" & len2
            MsgBox(msg)
            Return False
        End If
 
      Dim i As Integer
      For i = 0 To len1 - 1
         If buf1(i) <> buf2(i) Then
                msg = "byte " & i & " is different " & buf1(i) & "|" & buf2(i)
                MsgBox(msg)
                Return False
         End If
        Next i
        msg = "All bytes compare."
        MsgBox(msg)
        Return True
   End Function 'CompareData
 
 
   Public Shared Sub DeflateCompressDecompress(filename As String)
        msg = "Test compression and decompression on file " & filename
        MsgBox(msg)
 
        Dim infile As FileStream
      Try
         ' Open the file as a FileStream object.
         infile = New FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read)
            Dim buffer(infile.Length - 1) As Byte
         ' Read the file to ensure it is readable.
            Dim count As Integer = infile.Read(buffer, 0, buffer.Length)
         If count <> buffer.Length Then
                infile.Close()
                msg = "Test Failed: Unable to read data from file"
                MsgBox(msg)
                Return
         End If
         infile.Close()
         Dim ms As New MemoryStream()
         ' Use the newly created memory stream for the compressed data.
         Dim compressedzipStream As New DeflateStream(ms, CompressionMode.Compress, True)
         compressedzipStream.Write(buffer, 0, buffer.Length)
         ' Close the stream.
            compressedzipStream.Close()
 
            msg = "Original size: " & buffer.Length & ", Compressed size: " & ms.Length
            MsgBox(msg)
 
         ' Reset the memory stream position to begin decompression.
         ms.Position = 0
         Dim zipStream As New DeflateStream(ms, CompressionMode.Decompress)
         Dim decompressedBuffer(buffer.Length + 100) As Byte
         ' Use the ReadAllBytesFromStream to read the stream.
         Dim totalCount As Integer = DeflateTest.ReadAllBytesFromStream(zipStream, decompressedBuffer)
            msg = "Decompressed " & totalCount & " bytes"
            MsgBox(msg)
 
         If Not DeflateTest.CompareData(buffer, buffer.Length, decompressedBuffer, totalCount) Then
                msg = "Error. The two buffers did not compare."
                MsgBox(msg)
 
         End If
         zipStream.Close()
        Catch e As Exception
            msg = "Error: The file being read contains invalid data."
            MsgBox(msg)
        End Try
 
   End Sub 'DeflateCompressDecompress
 
    Public Shared Sub Main(ByVal args() As String)
        Dim usageText As String = "Usage: DeflateTest <inputfilename>"
        'If no file name is specified, write usage text.
        If args.Length = 0 Then
            Console.WriteLine(usageText)
        Else
            If File.Exists(args(0)) Then
                DeflateCompressDecompress(args(0))
            End If
        End If
    End Sub 'Main
End Class 'DeflateTest
 

[Flpit]

Yep, tried that, but it relies on having the original file, compressing it, then uncompressing it, so it has a reference to the uncompressed file size.

Can you explain how to implement this in stimple terms ??