1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUNTIME COMPONENTS -- 4-- -- 5-- S Y S T E M . E X P L L I -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 1992-2003 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 34package body System.Exp_LLI is 35 36 --------------------------- 37 -- Exp_Long_Long_Integer -- 38 --------------------------- 39 40 -- Note that negative exponents get a constraint error because the 41 -- subtype of the Right argument (the exponent) is Natural. 42 43 function Exp_Long_Long_Integer 44 (Left : Long_Long_Integer; 45 Right : Natural) 46 return Long_Long_Integer 47 is 48 Result : Long_Long_Integer := 1; 49 Factor : Long_Long_Integer := Left; 50 Exp : Natural := Right; 51 52 begin 53 -- We use the standard logarithmic approach, Exp gets shifted right 54 -- testing successive low order bits and Factor is the value of the 55 -- base raised to the next power of 2. 56 57 -- Note: it is not worth special casing base values -1, 0, +1 since 58 -- the expander does this when the base is a literal, and other cases 59 -- will be extremely rare. 60 61 if Exp /= 0 then 62 loop 63 if Exp rem 2 /= 0 then 64 declare 65 pragma Unsuppress (All_Checks); 66 begin 67 Result := Result * Factor; 68 end; 69 end if; 70 71 Exp := Exp / 2; 72 exit when Exp = 0; 73 74 declare 75 pragma Unsuppress (All_Checks); 76 begin 77 Factor := Factor * Factor; 78 end; 79 end loop; 80 end if; 81 82 return Result; 83 end Exp_Long_Long_Integer; 84 85end System.Exp_LLI; 86