(Visual FoxPro) 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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LOCAL lnSuccess
LOCAL loCompress
LOCAL lcInputFile
LOCAL lcCompressedFile
LOCAL lcDecompressedFile
LOCAL loFac
LOCAL lnOriginalSize
LOCAL lnRestoredSize

lnSuccess = 0

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

loCompress = CreateObject('Chilkat.Compression')

* Use the zlib algorithm (recommended for general use)
loCompress.Algorithm = "zlib"

* ------------------------------------------------------------------
* Compress a file
* ------------------------------------------------------------------

lcInputFile = "c:/temp/example.txt"
lcCompressedFile = "c:/temp/example.txt.zlib"

lnSuccess = loCompress.CompressFile(lcInputFile,lcCompressedFile)
IF (lnSuccess = 0) THEN
    ? "Compression failed:"
    ? loCompress.LastErrorText
    RELEASE loCompress
    CANCEL
ENDIF

? "File compressed successfully:"
? "  Input:      " + lcInputFile
? "  Compressed: " + lcCompressedFile

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

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

lnSuccess = loCompress.DecompressFile(lcCompressedFile,lcDecompressedFile)
IF (lnSuccess = 0) THEN
    ? "Decompression failed:"
    ? loCompress.LastErrorText
    RELEASE loCompress
    CANCEL
ENDIF

? "File decompressed successfully:"
? "  Output: " + lcDecompressedFile

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

loFac = CreateObject('Chilkat.FileAccess')

lnOriginalSize = loFac.FileSize(lcInputFile)
lnRestoredSize = loFac.FileSize(lcDecompressedFile)

? "Original file size:   " + STR(lnOriginalSize)
? "Restored file size:   " + STR(lnRestoredSize)

IF (lnOriginalSize = lnRestoredSize) THEN
    ? "Sizes match (basic verification successful)."
ELSE
    ? "Warning: File sizes differ."
ENDIF

RELEASE loCompress
RELEASE loFac