(PowerShell) Streaming Compression

Compress and decompress using a stream.

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

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

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

$streamC = New-Object Chilkat.Stream

# This example sets the source and sink of the stream to files.
# A stream can have use other streams as a source or sink,
# or the application can itself be the source/sink by directly
# reading or writing a stream.  (See below for an example of this..)
$streamC.SourceFile = "qa_data/hamlet.xml"
$streamC.SinkFile = "qa_output/hamlet_compressed.dat"

# Compress from source to sink.
$success = $compress.CompressStream($streamC)
if ($success -ne $true) {
    $($compress.LastErrorText)
    exit
}

$("File-to-file deflate compression successful.")
# 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.
$("Original size = " + $fac.FileSize($streamC.SourceFile))
$("Compressed size = " + $fac.FileSize($streamC.SinkFile))

# Now do file-to-file decompression
$streamD = New-Object Chilkat.Stream
$streamD.SourceFile = "qa_output/hamlet_compressed.dat"
$streamD.SinkFile = "qa_output/hamlet_restored.xml"

# Decompress from source to sink.
$success = $compress.DecompressStream($streamD)
if ($success -ne $true) {
    $($compress.LastErrorText)
    exit
}

$("File-to-file deflate decompression successful.")

# Let's double-check to see that the files are equal in size and content:

$bFilesEqual = $fac.FileContentsEqual($streamC.SourceFile,$streamD.SinkFile)
if ($bFilesEqual -ne $true) {
    $("The output file is not equal to the input file!")
}
else {
    $("The file was successfully compressed and decompressed.")
}

# ---------------------------------------------------------------------
# Now let's decompress again, but this time w/ the application reading
# the decompressed data directly from a stream.
$streamA = New-Object Chilkat.Stream

$streamA.SourceFile = "qa_output/hamlet_compressed.dat"

# Start decompressing in a background thread.
$task = $compress.DecompressStreamAsync($streamA)
$success = $task.Run()

# Read decompressed data from streamA:

while (($streamA.EndOfStream -ne $true)) {
    if ($streamA.DataAvailable -eq $true) {
        $decompressedText = $streamA.ReadString()
        $($decompressedText)
    }

}

# Let's make sure the background task finished and that the decompress was successful.
# It should already be the case that the task is finished.
while (($task.Finished -ne $true)) {
    $task.SleepMs(20)
}

# The decompressor may have finished, but it is possible that data
# remains to be flushed.  
if ($streamA.DataAvailable -eq $true) {
    $decompressedText = $streamA.ReadString()
    $($decompressedText)
}

# Did streamA succeed in reading the entire file?
if ($task.TaskSuccess -ne $true) {
    $("async decompress failed:")
    $($task.ResultErrorText)
    $success = $false
}

$("The async decompress was successful.")