How to add .arc decompression to Inno Setup?

This answer has been superseded by Inno Setup – How to add cancel button to decompressing page? that uses unarc.dll instead of driving the console Arc.exe.

I’m keeping this answer, as its concept can be useful for other archive types.

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See the example below. It:

• takes an ARC file, embeds it to the installer
• during installation, the ARC file is extracted to a temporary folder
• the files from the ARC file is extracted to the target folder

#define ArcArchive "test.arc"

[Files]
Source: {#ArcArchive}; DestDir: "{tmp}"; Flags: nocompression deleteafterinstall
Source: Arc.exe; Flags: dontcopy

[Code]

function BufferToAnsi(const Buffer: string): AnsiString;
var
  W: Word;
  I: Integer;
begin
  SetLength(Result, Length(Buffer) * 2);
  for I := 1 to Length(Buffer) do
  begin
    W := Ord(Buffer[I]);
    Result[(I * 2)] := Chr(W shr 8); // high byte
    Result[(I * 2) - 1] := Chr(Byte(W)); // low byte
  end;
end;

function SetTimer(
  Wnd: LongWord; IDEvent, Elapse: LongWord; TimerFunc: LongWord): LongWord;
  external '[email protected] stdcall';
function KillTimer(hWnd: LongWord; uIDEvent: LongWord): BOOL;
  external '[email protected] stdcall';

var
  ProgressPage: TOutputProgressWizardPage;
  ProgressFileName: string;

procedure UpdateProgressProc(
  H: LongWord; Msg: LongWord; Event: LongWord; Time: LongWord);
var
  S: AnsiString;
  L: Integer;
  P: Integer;
  Max: Integer;
  Progress: string;
  Buffer: string;
  Stream: TFileStream;
  Percent: Integer;
  Found: Boolean;
begin
  Found := False;
  if not FileExists(ProgressFileName) then
  begin
    Log(Format('Progress file %s does not exist', [ProgressFileName]));
  end
    else
  begin
    try
      // Need shared read as the output file is locked for writting,
      // so we cannot use LoadStringFromFile
      Stream :=
        TFileStream.Create(ProgressFileName, fmOpenRead or fmShareDenyNone);
      try
        L := Stream.Size;
        Max := 100*2014;
        if L > Max then
        begin
          Stream.Position := L - Max;
          L := Max;
        end;
        SetLength(Buffer, (L div 2) + (L mod 2));
        Stream.ReadBuffer(Buffer, L);
        S := BufferToAnsi(Buffer);
      finally
        Stream.Free;
      end;

      if S = '' then
      begin
        Log(Format('Progress file %s is empty', [ProgressFileName]));
      end;
    except
      Log(Format('Failed to read progress from file %s - %s', [
                 ProgressFileName, GetExceptionMessage]));
    end;
  end;

  if S <> '' then
  begin
    P := Pos('Extracted', S);
    if P > 0 then
    begin
      Log('Extraction done');
      Percent := 100;
      Found := True;
    end
      else
    begin
      P := Pos('%', S);
      if P > 0 then
      begin
        repeat
          Progress := Copy(S, 1, P - 1);
          Delete(S, 1, P);
          P := Pos('%', S);
        until (P = 0);
        
        P := Length(Progress);
        while (P > 0) and
              (((Progress[P] >= '0') and (Progress[P] <= '9')) or
               (Progress[P] = '.')) do
        begin
          Dec(P);
        end;

        Progress := Copy(Progress, P + 1, Length(Progress) - P);

        P := Pos('.', Progress);
        if P > 0 then
        begin
          Progress := Copy(Progress, 1, P - 1);
        end;

        Percent := StrToInt(Progress);
        Log(Format('Percent: %d', [Percent]));
        Found := True;
      end;
    end;
  end;

  if not Found then
  begin
    Log('No new data found');
    // no new progress data, at least pump the message queue
    ProgressPage.SetProgress(ProgressPage.ProgressBar.Position, 100);
  end
    else
  begin
    ProgressPage.SetProgress(Percent, 100);
    ProgressPage.SetText(Format('Extracted: %d%%', [Percent]), '');
  end;
end;

procedure ExtractArc;
var
  ArcExtracterPath: string;
  ArcArchivePath: string;
  TempPath: string;
  CommandLine: string;
  Timer: LongWord;
  ResultCode: Integer;
  S: AnsiString;
  Message: string;
begin
  ExtractTemporaryFile('Arc.exe');

  ProgressPage :=
    CreateOutputProgressPage('Decompression', 'Decompressing archive...');
  ProgressPage.SetProgress(0, 100);
  ProgressPage.Show;
  try
    Timer := SetTimer(0, 0, 250, CreateCallback(@UpdateProgressProc));

    TempPath := ExpandConstant('{tmp}');
    ArcExtracterPath := TempPath + '\Arc.exe';
    ArcArchivePath := TempPath + '\{#ArcArchive}';
    ProgressFileName := ExpandConstant('{tmp}\progress.txt');
    Log(Format('Expecting progress in %s', [ProgressFileName]));
    CommandLine :=
      Format('"%s" x -y -o+ -dp"%s" "%s" > "%s"', [
        ArcExtracterPath, ExpandConstant('{app}'), ArcArchivePath,
        ProgressFileName]);
    Log(Format('Executing: %s', [CommandLine]));
    CommandLine := Format('/C "%s"', [CommandLine]);
    if not Exec(ExpandConstant('{cmd}'), CommandLine, '', SW_HIDE,
                ewWaitUntilTerminated, ResultCode) then
    begin
      RaiseException('Cannot start extracter');
    end
      else
    if ResultCode <> 0 then
    begin
      LoadStringFromFile(ProgressFileName, S);
      Message :=
        Format('Arc extraction failed failed with code %d', [ResultCode]);
      Log(Message);
      Log('Output: ' + S);
      RaiseException(Message);
    end
      else
    begin
      Log('Arc extraction done');
    end;
  finally
    // Clean up
    Log('Arc extraction cleanup');
    KillTimer(0, Timer);
    ProgressPage.Hide;
    DeleteFile(ProgressFileName);
  end;
  Log('Arc extraction end');
end;

procedure CurStepChanged(CurStep: TSetupStep);
begin
  if CurStep = ssPostInstall then
  begin
    ExtractArc;
  end;
end;

The code needs arc.exe (I’ve taken it from PeaZip portable package).

For CreateCallback function, you need Inno Setup 6. If you are stuck with Inno Setup 5, you can use WrapCallback function from InnoTools InnoCallback library (and you need Unicode version of Inno Setup 5).

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Alternatively, to avoid double extraction, you can distribute the arc file along the installer.

Just use {src} to resolve its path:

ArcArchivePath := ExpandConstant('{src}\{#ArcArchive}');

And remove the {#ArcArchive} entry from the [Files] section.

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It would be more robust to implement the extraction using unarc.dll, like seen in the FreeArc+InnoSetup package ISFreeArcExtract v.4.0.rar.