Question

Has anyone written an ‘UnFormat’ routine for Delphi?

What I’m imagining is the inverse of SysUtils.Format and looks something like this

UnFormat(‘a number %n and another %n’,[float1, float2]);

So you could unpack a string into a series of variables using format strings.

I’ve looked at the ‘Format’ routine in SysUtils, but I’ve never used assembly so it is meaningless to me.

Answer 1

This is called scanf in C, I’ve made a Delphi look-a-like for this :

function ScanFormat(const Input, Format: string; Args: array of Pointer): Integer; var   InputOffset: Integer;   FormatOffset: Integer;   InputChar: Char;   FormatChar: Char;    function _GetInputChar: Char;   begin     if InputOffset <= Length(Input) then     begin       Result := Input[InputOffset];       Inc(InputOffset);     end     else       Result := #0;   end;    function _PeekFormatChar: Char;   begin     if FormatOffset <= Length(Format) then       Result := Format[FormatOffset]     else       Result := #0;   end;    function _GetFormatChar: Char;   begin     Result := _PeekFormatChar;     if Result <> #0 then       Inc(FormatOffset);   end;    function _ScanInputString(const Arg: Pointer = nil): string;   var     EndChar: Char;   begin     Result := '';     EndChar := _PeekFormatChar;     InputChar := _GetInputChar;     while (InputChar > ' ')       and (InputChar <> EndChar) do     begin       Result := Result + InputChar;       InputChar := _GetInputChar;     end;      if InputChar <> #0 then       Dec(InputOffset);      if Assigned(Arg) then       PString(Arg)^ := Result;   end;    function _ScanInputInteger(const Arg: Pointer): Boolean;   var     Value: string;   begin     Value := _ScanInputString;     Result := TryStrToInt(Value, {out} PInteger(Arg)^);   end;    procedure _Raise;   begin     raise EConvertError.CreateFmt('Unknown ScanFormat character : '%s'!', [FormatChar]);   end;  begin   Result := 0;   InputOffset := 1;   FormatOffset := 1;   FormatChar := _GetFormatChar;   while FormatChar <> #0 do   begin     if FormatChar <> '%' then     begin       InputChar := _GetInputChar;       if (InputChar = #0)       or (FormatChar <> InputChar) then         Exit;     end     else     begin       FormatChar := _GetFormatChar;       case FormatChar of         '%':           if _GetInputChar <> '%' then             Exit;         's':           begin             _ScanInputString(Args[Result]);             Inc(Result);           end;         'd', 'u':           begin             if not _ScanInputInteger(Args[Result]) then               Exit;              Inc(Result);           end;       else         _Raise;       end;     end;      FormatChar := _GetFormatChar;   end; end;