(Visual Basic 6.0) Compress Large Binary File in Blocks

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

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

Dim facSrc As New CkFileAccess
Dim facDest As New CkFileAccess

' Open a large binary file for reading.
Dim success As Long
success = facSrc.OpenForRead("qa_data/bmp/big.bmp")
If (success <> 1) Then
    Debug.Print facSrc.LastErrorText
    Exit Sub
End If

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

' Open an output file for the compressed data.
success = facDest.OpenForWrite("qa_data/bmp/compressedBmp.dat")
If (success <> 1) Then
    Debug.Print facDest.LastErrorText
    Exit Sub
End If

Dim compress As New ChilkatCompression
compress.Algorithm = "deflate"

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

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

    success = facDest.FileWrite(compressedBytes)

    i = i + 1
Loop

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

facSrc.FileClose 
facDest.FileClose 

Debug.Print "Finished compressing file."