VB.NET

Transition from Compression.BeginCompressBytes to FirstChunk/LastChunk

Provides instructions for replacing deprecated BeginCompressBytes method calls with using FirstChunk and LastChunk properties. VB.NET

Dim success As Boolean = False

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

' ----------------------------------------------------------------------------------
' This is the deprecated way of compressing in chunks using Begin/More/End methods..
' ----------------------------------------------------------------------------------
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.")

' ----------------------------------------------------------------------------------
' This is new way of compressing in chunks using FirstChunk and LastChunk properties
' ----------------------------------------------------------------------------------

success = facSrc.OpenForRead("qa_data/bmp/big.bmp")
If (success = False) Then
    Debug.WriteLine(facSrc.LastErrorText)
    Exit Sub
End If


success = facDest.OpenForWrite("c:/temp/qa_output/compressedBmp2.dat")
If (success = False) Then
    Debug.WriteLine(facDest.LastErrorText)
    Exit Sub
End If


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

i = 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 2.")