System.Zip.TZipFile.Extract

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Delphi 

procedure Extract(const FileName: string; const Path: string = ''; CreateSubdirs: Boolean = True); overload;
procedure Extract(Index: Integer; const Path: string = ''; CreateSubdirs: Boolean = True); overload;

C++ 

void __fastcall Extract(const System::UnicodeString FileName, const System::UnicodeString Path = System::UnicodeString(), bool CreateSubdirs = true)/* overload */;
void __fastcall Extract(int Index, const System::UnicodeString Path = System::UnicodeString(), bool CreateSubdirs = true)/* overload */;

Properties

Type Visibility Source Unit Parent
procedure
function
 public
System.Zip.pas
System.Zip.hpp
 System.Zip TZipFile

Description

Extracts a single file from the .zip archive.

  • FileName specifies the file to be extracted from the .zip file. All slashes in the .zip file names should be '/'.
  • Index represents the index of this file in the .zip archive.
  • Path represents the location, on the disk, where the file will be extracted.
  • CreateSubDirs indicates whether the output should create subdirectories specified in the .zip file. The default value for CreateSubDirs is True.

The second overload procedure is useful when a .zip file has duplicate file names.

To track the progress of the extraction, use OnProgress.

Extracting Password-protected Files

In order to extract password-protected (encrypted) files, you can use the OnCreateDecompressStream event or the CreateDecompressStreamCallBack callback. The following example demonstrates how to use OnCreateDecompressStream to extract an encrypted file:

  1. Assign the OnCreateDecompressStream event:

    Delphi: 

    ...
  myZipFile := TZipFile.Create;
  myZipFile.OnCreateDecompressStream := OnCreateDecompressStream;
  try
    myZipFile.ExtractAll('');
    myZipFile.Close;
  finally
    myZipFile.Free;
  end;
...

    C++: 

    ...
	std::unique_ptr<TZipFile> myZipFile(new TZipFile);
	myZipFile->OnCreateDecompressStream = OnCreateDecompressStream;
	myZipFile->ExtractAll("../../");
	myZipFile->Close();
...
  2. Perform decryption in your OnCreateDecompressStream function:

    Delphi:

    • Include the definition in the private section: 
        private
    { Private declarations }
    function OnCreateDecompressStream(const AInStream: TStream; const AZipFile: TZipFile;
      const AHeader: TZipHeader; AIsEncrypted: Boolean): TStream;
    • Implement the OnCreateDecompressStream function: 
      function TForm1.OnCreateDecompressStream(const AInStream: TStream; const AZipFile: TZipFile;
  const AHeader: TZipHeader; AIsEncrypted: Boolean): TStream;
begin
  try
    if AIsEncrypted then
    begin
      // Perform decrypt operation on AInStream. For example, you can use your own implementation of CryptZip or AES-256. 
      // Result := DecryptedStream;
    end
    else
       Result := AInStream;
  except
    on E:Exception do
    begin
      Result := AInStream;
    end;
  end;
end;

    3. C++:

    • Include the definition in you .h file: 
      private:	// User declarations
	TStream* __fastcall OnCreateDecompressStream (TStream* const InStream, TZipFile* const ZipFile, const TZipHeader &Item, bool IsEncrypted);
    • Implement the OnCreateDecompressStream function: 
      TStream* __fastcall TForm2::OnCreateDecompressStream(TStream* const InStream, TZipFile* const ZipFile, const TZipHeader &Item, bool IsEncrypted)
{
	try
	{
		if (IsEncrypted)
		{
			// Perform decrypt operation on AInStream. For example, you can use your own implementation of CryptZip or AES-256.
			// return DecryptedStream;
		}
		else
		{
			return InStream;
		}
	}
	catch (Exception &e)
	{
		return InStream;
	}
}

See Also

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