gcc/ada/s-exnlli.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . E X N _ L L I                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2005 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,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, 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
  34 package body System.Exn_LLI is
  35
  36    ---------------------------
  37    -- Exn_Long_Long_Integer --
  38    ---------------------------
  39
  40    function Exn_Long_Long_Integer
  41      (Left  : Long_Long_Integer;
  42       Right : Natural)
  43       return  Long_Long_Integer
  44    is
  45       pragma Suppress (Division_Check);
  46       pragma Suppress (Overflow_Check);
  47
  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                Result := Result * Factor;
  65             end if;
  66
  67             Exp := Exp / 2;
  68             exit when Exp = 0;
  69             Factor := Factor * Factor;
  70          end loop;
  71       end if;
  72
  73       return Result;
  74    end Exn_Long_Long_Integer;
  75
  76 end System.Exn_LLI;