(Tcl) Decompress Large Text File in Blocks

Decompresses a large text file in blocks, and compares the restored (decompressed) file with the original to make sure it's correct.

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load ./chilkat.dll

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

# First, let's compress a text file.
# We'll then decompress in blocks, and compare the decompressed with the original file.

# Compress a text file:
set compress [new_CkCompression]

CkCompression_put_Algorithm $compress "deflate"

set success [CkCompression_CompressFile $compress "qa_data/hamlet.xml" "qa_data/hamlet_compressed.dat"]
if {$success != 1} then {
    puts [CkCompression_lastErrorText $compress]
    delete_CkCompression $compress
    exit
}

set fac [new_CkFileAccess]

# Examine the uncompressed and compressed sizes:
set originalPath "qa_data/hamlet.xml"
# Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
# the size of the file as a string, then convert to an integer value.
puts "uncompressed size: [CkFileAccess_FileSize $fac $originalPath]"
puts "compressed size: [CkFileAccess_FileSize $fac qa_data/hamlet_compressed.dat]"

# Decompress in blocks..
set facSrc [new_CkFileAccess]

set facDest [new_CkFileAccess]

CkFileAccess_OpenForRead $facSrc "qa_data/hamlet_compressed.dat"

# 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 restoredPath "qa_output/hamlet_restored.xml"
set success [CkFileAccess_OpenForWrite $facDest $restoredPath]
if {$success != 1} then {
    puts [CkFileAccess_lastErrorText $facDest]
    delete_CkCompression $compress
    delete_CkFileAccess $fac
    delete_CkFileAccess $facSrc
    delete_CkFileAccess $facDest
    exit
}

set compressedBytes [new_CkByteData]

set i 0
while {$i < $numBlocks} {
    set success [CkFileAccess_ReadBlock $facSrc $i $blockSize $compressedBytes]
    if {$i == 0} then {
        set decompressedStr [CkCompression_beginDecompressString $compress $compressedBytes]
    }     else {
        set decompressedStr [CkCompression_moreDecompressString $compress $compressedBytes]
    }

    CkFileAccess_AppendText $facDest $decompressedStr "utf-8"

    set i [expr $i + 1]
}

# At the very end, flush any remaining content, if any.
set decompressedStr [CkCompression_endDecompressString $compress]
CkFileAccess_AppendText $facDest $decompressedStr "utf-8"

CkFileAccess_FileClose $facSrc
CkFileAccess_FileClose $facDest

# Examine the size of the restored file.
puts "restored size: [CkFileAccess_FileSize $fac $restoredPath]"

# Compare the contents of the original with the restored.
set bEqualContents [CkFileAccess_FileContentsEqual $fac $restoredPath $originalPath]
puts "Contents Equal: $bEqualContents"

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