(Visual FoxPro) Transition from Compression.BeginCompressBytes to FirstChunk/LastChunk

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

Note: This example requires Chilkat v11.0.0 or greater.

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

LOCAL lnSuccess
LOCAL loFacSrc
LOCAL loFacDest
LOCAL lnBlockSize
LOCAL lnNumBlocks
LOCAL loCompress
LOCAL loFileBytes
LOCAL loCompressedBytes
LOCAL i

lnSuccess = 0

loFacSrc = CreateObject('Chilkat.FileAccess')
loFacDest = CreateObject('Chilkat.FileAccess')

* Open a large binary file for reading.
lnSuccess = loFacSrc.OpenForRead("qa_data/bmp/big.bmp")
IF (lnSuccess = 0) THEN
    ? loFacSrc.LastErrorText
    RELEASE loFacSrc
    RELEASE loFacDest
    CANCEL
ENDIF

* If we compress in 64K chunks, find out how many blocks there will be.
lnBlockSize = 65536
lnNumBlocks = loFacSrc.GetNumBlocks(lnBlockSize)

* Open an output file for the compressed data.
lnSuccess = loFacDest.OpenForWrite("c:/temp/qa_output/compressedBmp.dat")
IF (lnSuccess = 0) THEN
    ? loFacDest.LastErrorText
    RELEASE loFacSrc
    RELEASE loFacDest
    CANCEL
ENDIF

loCompress = CreateObject('Chilkat.Compression')
loCompress.Algorithm = "deflate"

* ----------------------------------------------------------------------------------
* This is the deprecated way of compressing in chunks using Begin/More/End methods..
* ----------------------------------------------------------------------------------
i = 0
DO WHILE i < lnNumBlocks
    loFileBytes = loFacSrc.ReadBlock(i,lnBlockSize)
    IF (i = 0) THEN
        loCompressedBytes = loCompress.BeginCompressBytes(loFileBytes)
    ELSE
        loCompressedBytes = loCompress.MoreCompressBytes(loFileBytes)
    ENDIF

    loFacDest.FileWrite(loCompressedBytes)

    i = i + 1
ENDDO

* At the very end, flush any remaining compressed bytes, if any.
loCompressedBytes = loCompress.EndCompressBytes()
loFacDest.FileWrite(loCompressedBytes)

loFacSrc.FileClose()
loFacDest.FileClose()

? "Finished compressing file."

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

lnSuccess = loFacSrc.OpenForRead("qa_data/bmp/big.bmp")
IF (lnSuccess = 0) THEN
    ? loFacSrc.LastErrorText
    RELEASE loFacSrc
    RELEASE loFacDest
    RELEASE loCompress
    CANCEL
ENDIF

lnSuccess = loFacDest.OpenForWrite("c:/temp/qa_output/compressedBmp2.dat")
IF (lnSuccess = 0) THEN
    ? loFacDest.LastErrorText
    RELEASE loFacSrc
    RELEASE loFacDest
    RELEASE loCompress
    CANCEL
ENDIF

* Assuming numBlocks > 1
loCompress.FirstChunk = 1
loCompress.LastChunk = 0

i = 0
DO WHILE i < lnNumBlocks
    loFileBytes = loFacSrc.ReadBlock(i,lnBlockSize)
    loCompressedBytes = loCompress.CompressBytes(loFileBytes)

    loFacDest.FileWrite(loCompressedBytes)

    i = i + 1

    loCompress.FirstChunk = 0
    IF (i = (lnNumBlocks - 1)) THEN
        loCompress.LastChunk = 1
    ENDIF

ENDDO

loFacSrc.FileClose()
loFacDest.FileClose()

? "Finished compressing file 2."

RELEASE loFacSrc
RELEASE loFacDest
RELEASE loCompress