(Lianja) Compress Large Binary File in Blocks

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

Chilkat Lianja Extension Download Chilkat Lianja Extension

// 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 <> .T.) 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("qa_data/bmp/compressedBmp.dat")
if (llSuccess <> .T.) then
    ? loFacDest.LastErrorText
    release loFacSrc
    release loFacDest
    return
endif

loCompress = createobject("CkCompression")
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