(VB.NET) Compress Large Binary File in Blocks

Compresses a large binary file in blocks. This example uses BeginCompressBytes, MoreCompressBytes, and EndCompressBytes.

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim facSrc As New Chilkat.FileAccess
Dim facDest As New Chilkat.FileAccess

' Open a large binary file for reading.
Dim success As Boolean = facSrc.OpenForRead("qa_data/bmp/big.bmp")
If (success <> True) Then
    Debug.WriteLine(facSrc.LastErrorText)
    Exit Sub
End If


' If we compress in 64K chunks, find out how many blocks there will be.
Dim blockSize As Integer = 65536
Dim numBlocks As Integer = facSrc.GetNumBlocks(blockSize)

' Open an output file for the compressed data.
success = facDest.OpenForWrite("qa_data/bmp/compressedBmp.dat")
If (success <> True) Then
    Debug.WriteLine(facDest.LastErrorText)
    Exit Sub
End If



Dim compress As New Chilkat.Compression
compress.Algorithm = "deflate"

Dim fileBytes() As Byte
Dim compressedBytes() As Byte

Dim i As Integer = 0
While i < numBlocks
    fileBytes = facSrc.ReadBlock(i,blockSize)
    If (i = 0) Then
        compressedBytes = compress.BeginCompressBytes(fileBytes)
    Else
        compressedBytes = compress.MoreCompressBytes(fileBytes)
    End If


    facDest.FileWrite(compressedBytes)

    i = i + 1
End While

' At the very end, flush any remaining compressed bytes, if any.
compressedBytes = compress.EndCompressBytes()
facDest.FileWrite(compressedBytes)

facSrc.FileClose()
facDest.FileClose()

Debug.WriteLine("Finished compressing file.")