(Visual FoxPro) 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

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

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.FileAccess')
loFacSrc = CreateObject('Chilkat.FileAccess')
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.FileAccess')
loFacDest = CreateObject('Chilkat.FileAccess')

* Open a large binary file for reading.
lnSuccess = loFacSrc.OpenForRead("qa_data/bmp/big.bmp")
IF (lnSuccess <> 1) 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("qa_data/bmp/compressedBmp.dat")
IF (lnSuccess <> 1) THEN
    ? loFacDest.LastErrorText
    RELEASE loFacSrc
    RELEASE loFacDest
    CANCEL
ENDIF

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Compression')
loCompress = CreateObject('Chilkat.Compression')
loCompress.Algorithm = "deflate"

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."

RELEASE loFacSrc
RELEASE loFacDest
RELEASE loCompress