Anders Hesselbom

Decompressing text

2010-06-12

This post shows how to compress a String to reduce the amount memory it consumes, and this post shows how to use the CompressText function. To be able to read the content of the string, it must be decompressed (or inflated) again. The DecompressText function is one way to do this.

Private Function DecompressText(ByVal B() As Byte) As String
   Dim Result As New System.Text.StringBuilder()
   Using MemStream As New System.IO.MemoryStream(B)
      Using GZStream As New System.IO.Compression.GZipStream(MemStream, _
         IO.Compression.CompressionMode.Decompress)
      Do
         'Note that this makes 1024 bytes in VB.
         Dim Buffer(1023) As Byte
         Dim BytesRead As Integer = GZStream.Read(Buffer, 0, 1024)
         If BytesRead > 0 Then
            Result.Append( _
               System.Text.Encoding.UTF8.GetString(Buffer, 0, BytesRead))
         End If
         If BytesRead < 1024 Then
            Exit Do
         End If
      Loop
      GZStream.Close()
      Return Result.ToString()
      End Using
   End Using
End Function

Now, imagine that B is a byte array returned from the CompressText function. B holds the bytes of a compressed text string. B is passed to the DecompressText function and the function returns the inflated string again. Example:

'Create some text.
Dim S As String = "This is some text that I want to compress. Preferably it's " & _
"a long string loaded from a text file or some XML document."

'Assign the compressed version to the variable B.
Dim B() As Byte = CompressText(S.ToString())

'Decompress it, and display the result.
Dim Decompressed As String = DecompressText(B)
Console.WriteLine(Decompressed)

Have you seen a more elegant way to handle strings in memory than what the .NET Framework offers?

Categories: Visual Basic 9

Tags: Streams

One response to “Decompressing text”

1. visual basic « Эхо блогосферы says:

   2010-06-12 at 14:02

   […] Anders Hesselbom пишет: Decompress) Do ‘Note that this makes 1024 bytes in VB. Dim Buffer(1023) As Byte Dim BytesRead As Integer = GZStream.Read(Buffer, 0, 1024) If BytesRead > 0 Then Result.Append( _ System.Text.Encoding.UTF8.GetString(Buffer, 0, BytesRead)) … […]