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How can i use PChars correctly to improve this optimization?
function StripString(mask: string; var modifiedstring: string): string;
var
  index,len: integer;
  s: string;
begin
    Index := pos(Mask, ModifiedString);
    len := Length(ModifiedString);
    if index <> 0 then
    begin
        if Index <> 1 then
        begin
            s := LeftStr(ModifiedString, index - 1);
            ModifiedString := RightStr(ModifiedString, len-index);
        end else begin
            if Length(ModifiedString)>1 then
              ModifiedString := Copy(ModifiedString,2,len)
            else
              ModifiedString := '';
            s := '';
        end;
    end else begin
        s := ModifiedString;
        ModifiedString := '';
    end;
    result := s
end;

//faster method - uses PChars
function StripStringEx(mask: char; var modifiedstring: string): string;
var
  pSt,pCur,pEnd : Pchar;
begin
    pEnd := @modifiedString[Length(modifiedString)];
    pSt := @modifiedString[1];
    pCur := pSt;
    while pCur <= pEnd do
    begin
         if pCur^ = mask then break;
         inc(pCur);
    end;
    SetString(Result,pSt,pCur-pSt);
    SetString(ModifiedString,pCur+1,pEnd-pCur);
end;

function StripString(const Mask: string; var ModifiedString: string): string;
var
  Index: Integer;
begin
  Index := Pos(Mask, ModifiedString);
  if Index <> 0 then
  begin
    Result := LeftStr(ModifiedString, Index - 1);
    Delete(ModifiedString, Index);
  end
  else
  begin
    Result := ModifiedString;
    ModifiedString := '';
  end;
end;