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) 1992-2009 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 3,  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.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 package body System.Exn_LLI is
  33
  34    ---------------------------
  35    -- Exn_Long_Long_Integer --
  36    ---------------------------
  37
  38    function Exn_Long_Long_Integer
  39      (Left  : Long_Long_Integer;
  40       Right : Natural)
  41       return  Long_Long_Integer
  42    is
  43       pragma Suppress (Division_Check);
  44       pragma Suppress (Overflow_Check);
  45
  46       Result : Long_Long_Integer := 1;
  47       Factor : Long_Long_Integer := Left;
  48       Exp    : Natural := Right;
  49
  50    begin
  51       --  We use the standard logarithmic approach, Exp gets shifted right
  52       --  testing successive low order bits and Factor is the value of the
  53       --  base raised to the next power of 2.
  54
  55       --  Note: it is not worth special casing base values -1, 0, +1 since
  56       --  the expander does this when the base is a literal, and other cases
  57       --  will be extremely rare.
  58
  59       if Exp /= 0 then
  60          loop
  61             if Exp rem 2 /= 0 then
  62                Result := Result * Factor;
  63             end if;
  64
  65             Exp := Exp / 2;
  66             exit when Exp = 0;
  67             Factor := Factor * Factor;
  68          end loop;
  69       end if;
  70
  71       return Result;
  72    end Exn_Long_Long_Integer;
  73
  74 end System.Exn_LLI;