1 ------------------------------------------------------------------------------
3 -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . O S _ P R I M I T I V E S --
11 -- Copyright (C) 1998-2001 Free Software Foundation, Inc. --
13 -- GNARL is free software; you can redistribute it and/or modify it under --
14 -- terms of the GNU General Public License as published by the Free Soft- --
15 -- ware Foundation; either version 2, or (at your option) any later ver- --
16 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
17 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
18 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
19 -- for more details. You should have received a copy of the GNU General --
20 -- Public License distributed with GNARL; see file COPYING. If not, write --
21 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
22 -- MA 02111-1307, USA. --
24 -- As a special exception, if other files instantiate generics from this --
25 -- unit, or you link this unit with other files to produce an executable, --
26 -- this unit does not by itself cause the resulting executable to be --
27 -- covered by the GNU General Public License. This exception does not --
28 -- however invalidate any other reasons why the executable file might be --
29 -- covered by the GNU Public License. --
31 -- GNARL was developed by the GNARL team at Florida State University. --
32 -- Extensive contributions were provided by Ada Core Technologies Inc. --
34 ------------------------------------------------------------------------------
36 -- This package provides low level primitives used to implement clock and
37 -- delays in non tasking applications.
39 -- The choice of the real clock/delay implementation (depending on whether
40 -- tasking is involved or not) is done via soft links (see s-tasoli.ads)
42 -- NEVER add any dependency to tasking packages here
44 package System
.OS_Primitives
is
46 Max_Sensible_Delay
: constant Duration := 183 * 24 * 60 * 60.0;
47 -- Max of half a year delay, needed to prevent exceptions for large
48 -- delay values. It seems unlikely that any test will notice this
49 -- restriction, except in the case of applications setting the clock at
50 -- at run time (see s-tastim.adb). Also note that a larger value might
51 -- cause problems (e.g overflow, or more likely OS limitation in the
54 function Clock
return Duration;
55 pragma Inline
(Clock
);
56 -- Returns "absolute" time, represented as an offset
57 -- relative to "the Epoch", which is Jan 1, 1970 on unixes.
58 -- This implementation is affected by system's clock changes.
60 function Monotonic_Clock
return Duration;
61 pragma Inline
(Monotonic_Clock
);
62 -- Returns "absolute" time, represented as an offset
63 -- relative to "the Epoch", which is Jan 1, 1970.
64 -- This clock implementation is immune to the system's clock changes.
66 Relative
: constant := 0;
67 Absolute_Calendar
: constant := 1;
68 Absolute_RT
: constant := 2;
69 -- Values for Mode call below. Note that the compiler (exp_ch9.adb)
70 -- relies on these values. So any change here must be reflected in
71 -- corresponding changes in the compiler.
73 procedure Timed_Delay
(Time
: Duration; Mode
: Integer);
74 -- Implements the semantics of the delay statement when no tasking is
75 -- used in the application.
77 -- Mode is one of the three values above
79 -- Time is a relative or absolute duration value, depending on Mode.
81 -- Note that currently Ada.Real_Time always uses the tasking run time, so
82 -- this procedure should never be called with Mode set to Absolute_RT.
83 -- This may change in future or bare board implementations.
85 end System
.OS_Primitives
;