Lianja Requires Chilkat v11.0.0+

Compress Large Binary File in Blocks

See more Compression Examples

Compresses a large binary file in blocks. Lianja

llSuccess = .F.

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

loFacSrc = createobject("CkFileAccess")
loFacDest = createobject("CkFileAccess")

//  Open a large binary file for reading.
llSuccess = loFacSrc.OpenForRead("qa_data/bmp/big.bmp")
if (llSuccess = .F.) then
    ? loFacSrc.LastErrorText
    release loFacSrc
    release loFacDest
    return
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.
llSuccess = loFacDest.OpenForWrite("c:/temp/qa_output/compressedBmp.dat")
if (llSuccess = .F.) then
    ? loFacDest.LastErrorText
    release loFacSrc
    release loFacDest
    return
endif

loCompress = createobject("CkCompression")
loCompress.Algorithm = "deflate"

//  Assuming numBlocks > 1
loCompress.FirstChunk = .T.
loCompress.LastChunk = .F.

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

    loFacDest.FileWrite(loCompressedBytes)

    i = i + 1

    loCompress.FirstChunk = .F.
    if (i = (lnNumBlocks - 1)) then
        loCompress.LastChunk = .T.
    endif

enddo

loFacSrc.FileClose()
loFacDest.FileClose()

? "Finished compressing file."


release loFacSrc
release loFacDest
release loCompress