B4X

Add Custom Extra Data to a Gzip File

This example demonstrates how to use the SetExtraData method to include custom binary data in the Gzip header using a hex-encoded string.

The hex string represents the raw bytes to embed in the Gzip metadata. When a compression method is called, this data is included in the Gzip header.

The example also shows how to retrieve the metadata using GetGzipInfo to verify that the extra data was successfully embedded. The retrieved value is returned as a Base64-encoded string.

B4X

Dim success As Boolean = False

'  This example demonstrates how to include custom extra data
'  in the Gzip header when compressing.

'  The extra data is provided as a hex-encoded string.

Dim gzip As ChilkatGzip
gzip.Initialize("gzip")
Dim json As ChilkatJsonObject
json.Initialize

'  Set extra data using a hex string.
'  This example represents 4 bytes: 00 01 02 03
success = gzip.SetExtraData("00010203", "hex")
If success = False Then
    Log(gzip.LastErrorText)
    Return
End If


'  Compress a file so the extra data is embedded in the Gzip header:
Dim inputFile As String = "example.txt"
Dim outputFile As String = "example.txt.gz"

success = gzip.CompressFile(inputFile, outputFile)
If success = False Then
    Log(gzip.LastErrorText)
    Return
End If


Log("Gzip file created with extra data.")

'  (Optional) Retrieve the metadata to verify:
success = gzip.GetGzipInfo(outputFile, json)
If success = False Then
    Log(gzip.LastErrorText)
    Return
End If


Log("Metadata JSON:")
Log(json.Emit)