PowerShell

Transition from Compression.BeginCompressBytes to FirstChunk/LastChunk

Provides instructions for replacing deprecated BeginCompressBytes method calls with using FirstChunk and LastChunk properties. PowerShell

Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

$success = $false

$facSrc = New-Object Chilkat.FileAccess
$facDest = New-Object Chilkat.FileAccess

# Open a large binary file for reading.
$success = $facSrc.OpenForRead("qa_data/bmp/big.bmp")
if ($success -eq $false) {
    $($facSrc.LastErrorText)
    exit
}

# If we compress in 64K chunks, find out how many blocks there will be.
$blockSize = 65536
$numBlocks = $facSrc.GetNumBlocks($blockSize)

# Open an output file for the compressed data.
$success = $facDest.OpenForWrite("c:/temp/qa_output/compressedBmp.dat")
if ($success -eq $false) {
    $($facDest.LastErrorText)
    exit
}

$compress = New-Object Chilkat.Compression
$compress.Algorithm = "deflate"

# ----------------------------------------------------------------------------------
# This is the deprecated way of compressing in chunks using Begin/More/End methods..
# ----------------------------------------------------------------------------------
$i = 0
while ($i -lt $numBlocks) {
    $fileBytes = $facSrc.ReadBlock($i,$blockSize)
    if ($i -eq 0) {
        $compressedBytes = $compress.BeginCompressBytes($fileBytes)
    }
    else {
        $compressedBytes = $compress.MoreCompressBytes($fileBytes)
    }

    $facDest.FileWrite($compressedBytes)

    $i = $i + 1
}

# At the very end, flush any remaining compressed bytes, if any.
$compressedBytes = $compress.EndCompressBytes()
$facDest.FileWrite($compressedBytes)

$facSrc.FileClose()
$facDest.FileClose()

$("Finished compressing file.")

# ----------------------------------------------------------------------------------
# This is new way of compressing in chunks using FirstChunk and LastChunk properties
# ----------------------------------------------------------------------------------

$success = $facSrc.OpenForRead("qa_data/bmp/big.bmp")
if ($success -eq $false) {
    $($facSrc.LastErrorText)
    exit
}

$success = $facDest.OpenForWrite("c:/temp/qa_output/compressedBmp2.dat")
if ($success -eq $false) {
    $($facDest.LastErrorText)
    exit
}

# Assuming numBlocks > 1
$compress.FirstChunk = $true
$compress.LastChunk = $false

$i = 0
while ($i -lt $numBlocks) {
    $fileBytes = $facSrc.ReadBlock($i,$blockSize)
    $compressedBytes = $compress.CompressBytes($fileBytes)

    $facDest.FileWrite($compressedBytes)

    $i = $i + 1

    $compress.FirstChunk = $false
    if ($i -eq ($numBlocks - 1)) {
        $compress.LastChunk = $true
    }

}

$facSrc.FileClose()
$facDest.FileClose()

$("Finished compressing file 2.")