gcc/ada/libgnat/s-ransee.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                   S Y S T E M . R A N D O M _ S E E D                    --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2011-2018, 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 --  Version used on all systems except Ravenscar where Calendar is unavailable
  33
  34 with Ada.Calendar; use Ada.Calendar;
  35 with Ada.Unchecked_Conversion;
  36
  37 package body System.Random_Seed is
  38
  39    Y2K : constant Time :=
  40            Time_Of (Year => 2000, Month => 1, Day => 1, Seconds => 0.0);
  41    --  First day of Year 2000, to get a duration
  42
  43    function To_U64 is
  44      new Ada.Unchecked_Conversion (Duration, Interfaces.Unsigned_64);
  45
  46    --------------
  47    -- Get_Seed --
  48    --------------
  49
  50    function Get_Seed return Interfaces.Unsigned_64 is
  51    begin
  52       return To_U64 (Clock - Y2K);
  53    end Get_Seed;
  54
  55 end System.Random_Seed;