inline void MyCopy(AnsiString &Ret,char *cs,int n,int &LRet)
{
  int RetLength=Ret.Length();
  if (RetLength<LRet+n) Ret.SetLength(RetLength+ 2 *n);
  memcpy(Ret.c_str()+LRet,cs,n);
  LRet+=n;
}
AnsiString MyStringReplaceAll(AnsiString s,AnsiString f,AnsiString r)
{
  int sL=s.Length();
  int fL=f.Length();
  int rL=r.Length();

  AnsiString Ret;
  Ret.SetLength(sL);
  int LRet= 0 ;
  
  char *cs=s.c_str();
  char *csL=cs+sL;
  char *cf=f.c_str();
  char *cr=r.c_str();
  
  do
  {
    char *cs_found=StrPos(cs,cf);
    if (!cs_found)
    {
      MyCopy(Ret,cs,csL-cs,LRet);
      cs=csL;
    }
    else
    {
      MyCopy(Ret,cs,cs_found-cs,LRet);
      MyCopy(Ret,cr,rL,LRet);
      cs=cs_found+fL;
    }
  }while(cs<csL);

  Ret.SetLength(LRet);
  return Ret;
}

void __fastcall TForm1::Button2Click(TObject *Sender)
{
  AnsiString SrcString=Edit3->Text;
  AnsiString Find=Edit5->Text;
  AnsiString Replace=Edit6->Text;
  int N=Edit7->Text.ToInt();
  int StartTime1=GetTickCount();
  for(int i= 0 ;i<N;i++) MyStringReplaceAll(SrcString,Find,Replace);
  int EndTime1=GetTickCount();
  int StartTime2=GetTickCount();
  for(int i= 0 ;i<N;i++) StringReplace(SrcString,Find,Replace,TReplaceFlags()<<rfReplaceAll);
  int EndTime2=GetTickCount();
  ShowMessage(IntToStr(EndTime1-StartTime1)+"\r\n"+IntToStr(EndTime2-StartTime2));
}