(Tcl) Compress Large Binary File in Blocks

Compresses a large binary file in blocks.

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

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load ./chilkat.dll

set success 0

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

set facSrc [new_CkFileAccess]

set facDest [new_CkFileAccess]

# Open a large binary file for reading.
set success [CkFileAccess_OpenForRead $facSrc "qa_data/bmp/big.bmp"]
if {$success == 0} then {
    puts [CkFileAccess_lastErrorText $facSrc]
    delete_CkFileAccess $facSrc
    delete_CkFileAccess $facDest
    exit
}

# If we compress in 64K chunks, find out how many blocks there will be.
set blockSize 65536
set numBlocks [CkFileAccess_GetNumBlocks $facSrc $blockSize]

# Open an output file for the compressed data.
set success [CkFileAccess_OpenForWrite $facDest "c:/temp/qa_output/compressedBmp.dat"]
if {$success == 0} then {
    puts [CkFileAccess_lastErrorText $facDest]
    delete_CkFileAccess $facSrc
    delete_CkFileAccess $facDest
    exit
}

set compress [new_CkCompression]

CkCompression_put_Algorithm $compress "deflate"

set fileBytes [new_CkByteData]

set compressedBytes [new_CkByteData]

# Assuming numBlocks > 1
CkCompression_put_FirstChunk $compress 1
CkCompression_put_LastChunk $compress 0

set i 0
while {$i < $numBlocks} {
    set success [CkFileAccess_ReadBlock $facSrc $i $blockSize $fileBytes]
    set success [CkCompression_CompressBytes $compress $fileBytes $compressedBytes]

    CkFileAccess_FileWrite $facDest $compressedBytes

    set i [expr $i + 1]

    CkCompression_put_FirstChunk $compress 0
    if {$i == [expr $numBlocks - 1]} then {
        CkCompression_put_LastChunk $compress 1
    }

}

CkFileAccess_FileClose $facSrc
CkFileAccess_FileClose $facDest

puts "Finished compressing file."

delete_CkFileAccess $facSrc
delete_CkFileAccess $facDest
delete_CkCompression $compress
delete_CkByteData $fileBytes
delete_CkByteData $compressedBytes