(VBScript) Compressing and Decompressing Files Using Streaming (CompressFile / DecompressFile)

See more Compression Examples

This example demonstrates how to compress a file to a binary format and then restore it using the Chilkat.Compression class. The CompressFile method reads the source file, compresses it using the specified algorithm, and writes the result to a destination file. The DecompressFile method performs the reverse operation, restoring the original file from the compressed data.

Both operations are performed internally in streaming mode, allowing files of any size to be processed efficiently without loading the entire file into memory. The example also includes a simple verification step by comparing file sizes to confirm that the decompressed output matches the original input.

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Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

' This example assumes the Chilkat API has already been unlocked.
' See Global Unlock Sample for sample code.

set compress = CreateObject("Chilkat.Compression")

' Use the zlib algorithm (recommended for general use)
compress.Algorithm = "zlib"

' ------------------------------------------------------------------
' Compress a file
' ------------------------------------------------------------------

inputFile = "c:/temp/example.txt"
compressedFile = "c:/temp/example.txt.zlib"

success = compress.CompressFile(inputFile,compressedFile)
If (success = 0) Then
    outFile.WriteLine("Compression failed:")
    outFile.WriteLine(compress.LastErrorText)
    WScript.Quit
End If

outFile.WriteLine("File compressed successfully:")
outFile.WriteLine("  Input:      " & inputFile)
outFile.WriteLine("  Compressed: " & compressedFile)

' ------------------------------------------------------------------
' Decompress the file back to its original form
' ------------------------------------------------------------------

decompressedFile = "c:/temp/example_restored.txt"

success = compress.DecompressFile(compressedFile,decompressedFile)
If (success = 0) Then
    outFile.WriteLine("Decompression failed:")
    outFile.WriteLine(compress.LastErrorText)
    WScript.Quit
End If

outFile.WriteLine("File decompressed successfully:")
outFile.WriteLine("  Output: " & decompressedFile)

' ------------------------------------------------------------------
' Optional: Verify file sizes (basic sanity check)
' ------------------------------------------------------------------

set fac = CreateObject("Chilkat.FileAccess")

originalSize = fac.FileSize(inputFile)
restoredSize = fac.FileSize(decompressedFile)

outFile.WriteLine("Original file size:   " & originalSize)
outFile.WriteLine("Restored file size:   " & restoredSize)

If (originalSize = restoredSize) Then
    outFile.WriteLine("Sizes match (basic verification successful).")
Else
    outFile.WriteLine("Warning: File sizes differ.")
End If


outFile.Close