(Tcl) Decompress Large Binary File in Blocks

Decompresses a large binary file in blocks. This example uses BeginDecompressBytes, MoreDecompressBytes, and EndDecompressBytes.

Chilkat Tcl Extension Downloads Chilkat Tcl Extension Downloads

load ./chilkat.dll

# This example requires 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 previously compressed file for decompressing.
# See Compress Large File in Blocks

set success [CkFileAccess_OpenForRead $facSrc "qa_data/bmp/compressedBmp.dat"]
if {$success != 1} then {
    puts [CkFileAccess_lastErrorText $facSrc]
    delete_CkFileAccess $facSrc
    delete_CkFileAccess $facDest
    exit
}

# If we compress in 32K chunks, find out how many blocks there will be.
set blockSize 32768
set numBlocks [CkFileAccess_GetNumBlocks $facSrc $blockSize]

# Open an output file for the decompressed data.
set success [CkFileAccess_OpenForWrite $facDest "qa_output/decompressed.bmp"]
if {$success != 1} then {
    puts [CkFileAccess_lastErrorText $facDest]
    delete_CkFileAccess $facSrc
    delete_CkFileAccess $facDest
    exit
}

set compress [new_CkCompression]

CkCompression_put_Algorithm $compress "deflate"

set decompressedBytes [new_CkByteData]

set compressedBytes [new_CkByteData]

set i 0
while {$i < $numBlocks} {
    set success [CkFileAccess_ReadBlock $facSrc $i $blockSize $compressedBytes]
    if {$i == 0} then {
        set success [CkCompression_BeginDecompressBytes $compress $compressedBytes $decompressedBytes]
    }     else {
        set success [CkCompression_MoreDecompressBytes $compress $compressedBytes $decompressedBytes]
    }

    CkFileAccess_FileWrite $facDest $decompressedBytes

    set i [expr $i + 1]
}

# At the very end, flush any remaining decompressed bytes, if any.
set success [CkCompression_EndDecompressBytes $compress $decompressedBytes]
CkFileAccess_FileWrite $facDest $decompressedBytes

CkFileAccess_FileClose $facSrc
CkFileAccess_FileClose $facDest

puts "Finished decompressing file."

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