Delphi DLL

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.

Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Crypt2, JsonObject, Compression;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
compress: HCkCompression;
json: HCkJsonObject;
inPath: PWideChar;
outPath: PWideChar;
inPath2: PWideChar;
outPath2: PWideChar;
crypt: HCkCrypt2;
decryptedPath: PWideChar;
outPath3: PWideChar;

begin
success := False;

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

compress := CkCompression_Create();
CkCompression_putAlgorithm(compress,'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 := CkJsonObject_Create();
CkJsonObject_UpdateString(json,'cryptAlgorithm','aes');
CkJsonObject_UpdateString(json,'cipherMode','cbc');
CkJsonObject_UpdateInt(json,'keyLength',128);
CkJsonObject_UpdateInt(json,'paddingScheme',0);
CkJsonObject_UpdateString(json,'encodedIV','000102030405060708090A0B0C0D0E0F');
CkJsonObject_UpdateString(json,'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 := CkCompression_CompressEncryptFile(compress,json,inPath,outPath);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

// We can do file-to-file decrypt/decompress like this:
inPath2 := outPath;
outPath2 := 'c:/temp/qa_output/restored.dat';
success := CkCompression_DecryptDecompressFile(compress,json,inPath2,outPath2);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCompression__lastErrorText(compress));
    Exit;
  end;

// Note: The above decrypt + decompress is the equivalent of doing the same in these two steps:
crypt := CkCrypt2_Create();
CkCrypt2_putCryptAlgorithm(crypt,'aes');
CkCrypt2_putCipherMode(crypt,'cbc');
CkCrypt2_putKeyLength(crypt,128);
CkCrypt2_putPaddingScheme(crypt,0);
CkCrypt2_SetEncodedIV(crypt,'000102030405060708090A0B0C0D0E0F','hex');
CkCrypt2_SetEncodedKey(crypt,'000102030405060708090A0B0C0D0E0F','hex');

decryptedPath := 'c:/temp/qa_output/decrypted.dat';
success := CkCrypt2_CkDecryptFile(crypt,inPath2,decryptedPath);
if (success = False) then
  begin
    Memo1.Lines.Add(CkCrypt2__lastErrorText(crypt));
    Exit;
  end;

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

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

CkCompression_Dispose(compress);
CkJsonObject_Dispose(json);
CkCrypt2_Dispose(crypt);

end;