gcc/ada/s-osprim-vms.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --                  S Y S T E M . O S _ P R I M I T I V E S                 --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1998-2009, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNARL 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 -- GNARL was developed by the GNARL team at Florida State University.       --
  28 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This package provides low level primitives used to implement clock and
  33 --  delays in non tasking applications on Alpha/VMS.
  34
  35 --  The choice of the real clock/delay implementation (depending on whether
  36 --  tasking is involved or not) is done via soft links (see s-soflin.ads)
  37
  38 --  NEVER add any dependency to tasking packages here
  39
  40 package System.OS_Primitives is
  41    pragma Preelaborate;
  42
  43    subtype OS_Time is Long_Integer;
  44    --  System time on VMS is used for performance reasons.
  45    --  Note that OS_Time is *not* the same as Ada.Calendar.Time, the
  46    --  difference being that relative OS_Time is negative, but relative
  47    --  Calendar.Time is positive.
  48    --  See Ada.Calendar.Delays for more information on VMS Time.
  49
  50    Max_Sensible_Delay : constant Duration :=
  51                           Duration'Min (183 * 24 * 60 * 60.0,
  52                                         Duration'Last);
  53    --  Max of half a year delay, needed to prevent exceptions for large delay
  54    --  values. It seems unlikely that any test will notice this restriction,
  55    --  except in the case of applications setting the clock at run time (see
  56    --  s-tastim.adb). Also note that a larger value might cause problems (e.g
  57    --  overflow, or more likely OS limitation in the primitives used). In the
  58    --  case where half a year is too long (which occurs in high integrity mode
  59    --  with 32-bit words, and possibly on some specific ports of GNAT),
  60    --  Duration'Last is used instead.
  61
  62    procedure Initialize;
  63    --  Initialize global settings related to this package. This procedure
  64    --  should be called before any other subprograms in this package. Note
  65    --  that this procedure can be called several times.
  66
  67    function OS_Clock return OS_Time;
  68    --  Returns "absolute" time, represented as an offset
  69    --  relative to "the Epoch", which is Nov 17, 1858 on VMS.
  70
  71    function Clock return Duration;
  72    pragma Inline (Clock);
  73    --  Returns "absolute" time, represented as an offset relative to "the
  74    --  Epoch", which is Jan 1, 1970 00:00:00 UTC on UNIX systems. This
  75    --  implementation is affected by system's clock changes.
  76
  77    function Monotonic_Clock return Duration;
  78    pragma Inline (Monotonic_Clock);
  79    --  Returns "absolute" time, represented as an offset relative to "the Unix
  80    --  Epoch", which is Jan 1, 1970 00:00:00 UTC. This clock implementation is
  81    --  immune to the system's clock changes.
  82
  83    Relative          : constant := 0;
  84    Absolute_Calendar : constant := 1;
  85    Absolute_RT       : constant := 2;
  86    --  Values for Mode call below. Note that the compiler (exp_ch9.adb) relies
  87    --  on these values. So any change here must be reflected in corresponding
  88    --  changes in the compiler.
  89
  90    procedure Timed_Delay (Time : Duration; Mode : Integer);
  91    --  Implements the semantics of the delay statement when no tasking is used
  92    --  in the application.
  93    --
  94    --    Mode is one of the three values above
  95    --
  96    --    Time is a relative or absolute duration value, depending on Mode.
  97    --
  98    --  Note that currently Ada.Real_Time always uses the tasking run time,
  99    --  so this procedure should never be called with Mode set to Absolute_RT.
 100    --  This may change in future or bare board implementations.
 101
 102    function To_Duration (T : OS_Time; Mode : Integer) return Duration;
 103    --  Convert VMS system time to Duration
 104    --  Mode is one of the three values above
 105
 106    function To_OS_Time (D : Duration; Mode : Integer) return OS_Time;
 107    --  Convert Duration to VMS system time
 108    --  Mode is one of the three values above
 109
 110 end System.OS_Primitives;