gcc/ada/libgnat/a-caldel.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --                   A D A . C A L E N D A R . D E L A Y S                  --
   6 --                                                                          --
   7 --                                  B o d y                                 --
   8 --                                                                          --
   9 --             Copyright (C) 1991-2017, Florida State University            --
  10 --                     Copyright (C) 1995-2018, AdaCore                     --
  11 --                                                                          --
  12 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  15 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  18 --                                                                          --
  19 -- As a special exception under Section 7 of GPL version 3, you are granted --
  20 -- additional permissions described in the GCC Runtime Library Exception,   --
  21 -- version 3.1, as published by the Free Software Foundation.               --
  22 --                                                                          --
  23 -- You should have received a copy of the GNU General Public License and    --
  24 -- a copy of the GCC Runtime Library Exception along with this program;     --
  25 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  26 -- <http://www.gnu.org/licenses/>.                                          --
  27 --                                                                          --
  28 -- GNARL was developed by the GNARL team at Florida State University.       --
  29 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  30 --                                                                          --
  31 ------------------------------------------------------------------------------
  32
  33 with System.OS_Primitives;
  34 with System.Soft_Links;
  35
  36 package body Ada.Calendar.Delays is
  37
  38    package OSP renames System.OS_Primitives;
  39    package SSL renames System.Soft_Links;
  40
  41    use type SSL.Timed_Delay_Call;
  42
  43    --  Earlier, System.Time_Operations was used to implement the following
  44    --  operations. The idea was to avoid sucking in the tasking packages. This
  45    --  did not work. Logically, we can't have it both ways. There is no way to
  46    --  implement time delays that will have correct task semantics without
  47    --  reference to the tasking run-time system. To achieve this goal, we now
  48    --  use soft links.
  49
  50    -----------------------
  51    -- Local Subprograms --
  52    -----------------------
  53
  54    procedure Timed_Delay_NT (Time : Duration; Mode : Integer);
  55    --  Timed delay procedure used when no tasking is active
  56
  57    ---------------
  58    -- Delay_For --
  59    ---------------
  60
  61    procedure Delay_For (D : Duration) is
  62    begin
  63       SSL.Timed_Delay.all (Duration'Min (D, OSP.Max_Sensible_Delay),
  64                            OSP.Relative);
  65    end Delay_For;
  66
  67    -----------------
  68    -- Delay_Until --
  69    -----------------
  70
  71    procedure Delay_Until (T : Time) is
  72       D : constant Duration := To_Duration (T);
  73
  74    begin
  75       SSL.Timed_Delay.all (D, OSP.Absolute_Calendar);
  76    end Delay_Until;
  77
  78    --------------------
  79    -- Timed_Delay_NT --
  80    --------------------
  81
  82    procedure Timed_Delay_NT (Time : Duration; Mode : Integer) is
  83    begin
  84       OSP.Timed_Delay (Time, Mode);
  85    end Timed_Delay_NT;
  86
  87    -----------------
  88    -- To_Duration --
  89    -----------------
  90
  91    function To_Duration (T : Time) return Duration is
  92    begin
  93       --  Since time has multiple representations on different platforms, a
  94       --  target independent operation in Ada.Calendar is used to perform
  95       --  this conversion.
  96
  97       return Delay_Operations.To_Duration (T);
  98    end To_Duration;
  99
 100 begin
 101    --  Set up the Timed_Delay soft link to the non tasking version if it has
 102    --  not been already set. If tasking is present, Timed_Delay has already set
 103    --  this soft link, or this will be overridden during the elaboration of
 104    --  System.Tasking.Initialization
 105
 106    if SSL.Timed_Delay = null then
 107       SSL.Timed_Delay := Timed_Delay_NT'Access;
 108    end if;
 109
 110 end Ada.Calendar.Delays;