(Delphi DLL) 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.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
compress: HCkCompression;
inputFile: PWideChar;
compressedFile: PWideChar;
decompressedFile: PWideChar;
fac: HCkFileAccess;
originalSize: Integer;
restoredSize: Integer;

begin
success := False;

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

compress := CkCompression_Create();

// Use the zlib algorithm (recommended for general use)
CkCompression_putAlgorithm(compress,'zlib');

// ------------------------------------------------------------------
// Compress a file
// ------------------------------------------------------------------

inputFile := 'c:/temp/example.txt';
compressedFile := 'c:/temp/example.txt.zlib';

success := CkCompression_CompressFile(compress,inputFile,compressedFile);
if (success = False) then
  begin
    Memo1.Lines.Add('Compression failed:');
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

Memo1.Lines.Add('File compressed successfully:');
Memo1.Lines.Add('  Input:      ' + inputFile);
Memo1.Lines.Add('  Compressed: ' + compressedFile);

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

decompressedFile := 'c:/temp/example_restored.txt';

success := CkCompression_DecompressFile(compress,compressedFile,decompressedFile);
if (success = False) then
  begin
    Memo1.Lines.Add('Decompression failed:');
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

Memo1.Lines.Add('File decompressed successfully:');
Memo1.Lines.Add('  Output: ' + decompressedFile);

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

fac := CkFileAccess_Create();

originalSize := CkFileAccess_FileSize(fac,inputFile);
restoredSize := CkFileAccess_FileSize(fac,decompressedFile);

Memo1.Lines.Add('Original file size:   ' + IntToStr(originalSize));
Memo1.Lines.Add('Restored file size:   ' + IntToStr(restoredSize));

if (originalSize = restoredSize) then
  begin
    Memo1.Lines.Add('Sizes match (basic verification successful).');
  end
else
  begin
    Memo1.Lines.Add('Warning: File sizes differ.');
  end;

CkCompression_Dispose(compress);
CkFileAccess_Dispose(fac);

end;