VB.NET

Compress Large Binary File in Blocks

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Compresses a large binary file in blocks. VB.NET

Dim success As Boolean = False

' 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.
success = facSrc.OpenForRead("qa_data/bmp/big.bmp")
If (success = False) 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("c:/temp/qa_output/compressedBmp.dat")
If (success = False) 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

' Assuming numBlocks > 1
compress.FirstChunk = True
compress.LastChunk = False

Dim i As Integer = 0
While i < numBlocks
    fileBytes = facSrc.ReadBlock(i,blockSize)
    compressedBytes = compress.CompressBytes(fileBytes)

    facDest.FileWrite(compressedBytes)

    i = i + 1

    compress.FirstChunk = False
    If (i = (numBlocks - 1)) Then
        compress.LastChunk = True
    End If

End While

facSrc.FileClose()
facDest.FileClose()

Debug.WriteLine("Finished compressing file.")