1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUNTIME COMPONENTS                          --
4--                                                                          --
5--                        S Y S T E M . X P _ B M L                         --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--        Copyright (C) 1992,1993,1994 Free Software Foundation, Inc.       --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
17-- for  more details.  You should have  received  a copy of the GNU General --
18-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
19-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
20-- MA 02111-1307, USA.                                                      --
21--                                                                          --
22-- As a special exception,  if other files  instantiate  generics from this --
23-- unit, or you link  this unit with other files  to produce an executable, --
24-- this  unit  does not  by itself cause  the resulting  executable  to  be --
25-- covered  by the  GNU  General  Public  License.  This exception does not --
26-- however invalidate  any other reasons why  the executable file  might be --
27-- covered by the  GNU Public License.                                      --
28--                                                                          --
29-- GNAT was originally developed  by the GNAT team at  New York University. --
30-- Extensive contributions were provided by Ada Core Technologies Inc.      --
31--                                                                          --
32------------------------------------------------------------------------------
33
34with System.Unsigned_Types; use System.Unsigned_Types;
35
36package body System.Exp_LLU is
37
38   ----------------------------
39   -- Exp_Long_Long_Unsigned --
40   ----------------------------
41
42   function Exp_Long_Long_Unsigned
43     (Left  : Long_Long_Unsigned;
44      Right : Natural)
45      return  Long_Long_Unsigned
46   is
47      Result : Long_Long_Unsigned := 1;
48      Factor : Long_Long_Unsigned := Left;
49      Exp    : Natural := Right;
50
51   begin
52      --  We use the standard logarithmic approach, Exp gets shifted right
53      --  testing successive low order bits and Factor is the value of the
54      --  base raised to the next power of 2.
55
56      --  Note: it is not worth special casing the cases of base values -1,0,+1
57      --  since the expander does this when the base is a literal, and other
58      --  cases will be extremely rare.
59
60      if Exp /= 0 then
61         loop
62            if Exp rem 2 /= 0 then
63               Result := Result * Factor;
64            end if;
65
66            Exp := Exp / 2;
67            exit when Exp = 0;
68            Factor := Factor * Factor;
69         end loop;
70      end if;
71
72      return Result;
73
74   end Exp_Long_Long_Unsigned;
75
76end System.Exp_LLU;
77