B4X

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.

B4X

Dim success As Boolean = False

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

Dim compress As ChilkatCompression
compress.Initialize("compress")

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

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

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

success = compress.CompressFile(inputFile, compressedFile)
If success = False Then
    Log("Compression failed:")
    Log(compress.LastErrorText)
    Return
End If


Log("File compressed successfully:")
Log("  Input:      " & inputFile)
Log("  Compressed: " & compressedFile)

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

Dim decompressedFile As String = "c:/temp/example_restored.txt"

success = compress.DecompressFile(compressedFile, decompressedFile)
If success = False Then
    Log("Decompression failed:")
    Log(compress.LastErrorText)
    Return
End If


Log("File decompressed successfully:")
Log("  Output: " & decompressedFile)

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

Dim fac As ChilkatFileAccess
fac.Initialize

Dim originalSize As Int = fac.FileSize(inputFile)
Dim restoredSize As Int = fac.FileSize(decompressedFile)

Log("Original file size:   " & originalSize)
Log("Restored file size:   " & restoredSize)

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