(Delphi ActiveX) 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.

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
compress: TChilkatCompression;
success: Integer;
json: TChilkatJsonObject;
inPath: WideString;
outPath: WideString;
inPath2: WideString;
outPath2: WideString;
crypt: TChilkatCrypt2;
decryptedPath: WideString;
outPath3: WideString;

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

compress := TChilkatCompression.Create(Self);
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 := TChilkatJsonObject.Create(Self);
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.ControlInterface,inPath,outPath);
if (success = 0) then
  begin
    Memo1.Lines.Add(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.ControlInterface,inPath2,outPath2);
if (success = 0) then
  begin
    Memo1.Lines.Add(compress.LastErrorText);
    Exit;
  end;

// Note: The above decrypt + decompress is the equivalent of doing the same in these two steps:
crypt := TChilkatCrypt2.Create(Self);
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 = 0) then
  begin
    Memo1.Lines.Add(crypt.LastErrorText);
    Exit;
  end;

outPath3 := 'c:/temp/qa_output/restored_in_two_steps.dat';
success := compress.DecompressFile(decryptedPath,outPath3);
if (success = 0) then
  begin
    Memo1.Lines.Add(compress.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Success.');
end;