Delphi DLL

Compress a File to Gzip with Custom Metadata

See more Gzip Examples

This example demonstrates how to use the CompressFile method to create a Gzip (.gz) file while customizing the metadata embedded in the Gzip header.

Before compression, several properties are set:

• Comment: Adds a descriptive comment to the Gzip file.
• Filename: Specifies the filename to embed in the Gzip data, which may be used by extraction tools as the default output name.
• CompressionLevel: Controls the tradeoff between compression ratio and speed (set to maximum in this example).
• LastModStr: Sets the last-modified timestamp using an RFC 822 formatted date string.

After setting these properties, the input file is compressed and written to a .gz file. This approach allows you to embed meaningful metadata along with the compressed data.

Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Gzip;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
gzip: HCkGzip;
inputFile: PWideChar;
outputFile: PWideChar;

begin
success := False;

// This example demonstrates how to compress a file to Gzip format
// while setting custom metadata such as comment, filename,
// compression level, and last-modified date.

gzip := CkGzip_Create();

// Set custom Gzip properties:
CkGzip_putComment(gzip,'Example Gzip file created with Chilkat');
CkGzip_putFilename(gzip,'custom_name.txt');
CkGzip_putCompressionLevel(gzip,9);
CkGzip_putLastModStr(gzip,'Wed, 1 Apr 2025 12:45:26 -0500');

// The file to be compressed:
inputFile := 'example.txt';
outputFile := 'example.txt.gz';

// Compress the file:
success := CkGzip_CompressFile(gzip,inputFile,outputFile);
if (success = False) then
  begin
    Memo1.Lines.Add(CkGzip__lastErrorText(gzip));
    Exit;
  end;

Memo1.Lines.Add('Compression successful.');
Memo1.Lines.Add('Gzip file created: ' + outputFile);

CkGzip_Dispose(gzip);

end;