Pascal (Lazarus/Delphi)

Compress and Encrypt a Large File (Low and Constant Memory Footprint)

See more Compression Examples

Demonstrates how to compress and encrypt a large file such that the memory footprint remains low and constant.

Note: This example requires Chilkat v9.5.0.99 or greater.

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Crypt2,
  Chilkat.JsonObject,
  Chilkat.Compression;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  compress: TCompression;
  json: TJsonObject;
  inPath: string;
  outPath: string;
  inPath2: string;
  outPath2: string;
  crypt: TCrypt2;
  decryptedPath: string;
  outPath3: string;

begin
  success := False;

  //  This example assumes the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  compress := TCompression.Create;
  compress.Algorithm := 'deflate';

  //  Set encryption params.
  //  The possible values are the same as for the corresponding properties in the Chilkat Crypt2 class/object.
  //  The encoded IV and Key must be specified as hex.
  json := TJsonObject.Create;
  json.UpdateString('cryptAlgorithm','aes');
  json.UpdateString('cipherMode','cbc');
  json.UpdateInt('keyLength',128);
  json.UpdateInt('paddingScheme',0);
  json.UpdateString('encodedIV','000102030405060708090A0B0C0D0E0F');
  json.UpdateString('encodedKey','000102030405060708090A0B0C0D0E0F');

  //  Do file-to-file compression+encryption in a single call.
  inPath := 'qa_data/largeFile.dat';
  outPath := 'c:/temp/qa_output/compressed_encrypted.dat';
  success := compress.CompressEncryptFile(json,inPath,outPath);
  if (success = False) then
    begin
      WriteLn(compress.LastErrorText);
      Exit;
    end;

  //  We can do file-to-file decrypt/decompress like this:
  inPath2 := outPath;
  outPath2 := 'c:/temp/qa_output/restored.dat';
  success := compress.DecryptDecompressFile(json,inPath2,outPath2);
  if (success = False) then
    begin
      WriteLn(compress.LastErrorText);
      Exit;
    end;

  //  Note: The above decrypt + decompress is the equivalent of doing the same in these two steps:
  crypt := TCrypt2.Create;
  crypt.CryptAlgorithm := 'aes';
  crypt.CipherMode := 'cbc';
  crypt.KeyLength := 128;
  crypt.PaddingScheme := 0;
  crypt.SetEncodedIV('000102030405060708090A0B0C0D0E0F','hex');
  crypt.SetEncodedKey('000102030405060708090A0B0C0D0E0F','hex');

  decryptedPath := 'c:/temp/qa_output/decrypted.dat';
  success := crypt.CkDecryptFile(inPath2,decryptedPath);
  if (success = False) then
    begin
      WriteLn(crypt.LastErrorText);
      Exit;
    end;

  outPath3 := 'c:/temp/qa_output/restored_in_two_steps.dat';
  success := compress.DecompressFile(decryptedPath,outPath3);
  if (success = False) then
    begin
      WriteLn(compress.LastErrorText);
      Exit;
    end;

  WriteLn('Success.');


  compress.Free;
  json.Free;
  crypt.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.