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+------------------------------------------------------------------------------
+-- --
+-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
+-- --
+-- S Y S T E M . O S _ P R I M I T I V E S --
+-- --
+-- S p e c --
+-- --
+-- Copyright (C) 1998-2007, Free Software Foundation, Inc. --
+-- --
+-- GNARL is free software; you can redistribute it and/or modify it under --
+-- terms of the GNU General Public License as published by the Free Soft- --
+-- ware Foundation; either version 2, or (at your option) any later ver- --
+-- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
+-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
+-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
+-- for more details. You should have received a copy of the GNU General --
+-- Public License distributed with GNARL; see file COPYING. If not, write --
+-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
+-- Boston, MA 02110-1301, USA. --
+-- --
+-- As a special exception, if other files instantiate generics from this --
+-- unit, or you link this unit with other files to produce an executable, --
+-- this unit does not by itself cause the resulting executable to be --
+-- covered by the GNU General Public License. This exception does not --
+-- however invalidate any other reasons why the executable file might be --
+-- covered by the GNU Public License. --
+-- --
+-- GNARL was developed by the GNARL team at Florida State University. --
+-- Extensive contributions were provided by Ada Core Technologies, Inc. --
+-- --
+------------------------------------------------------------------------------
+
+-- This package provides low level primitives used to implement clock and
+-- delays in non tasking applications.
+
+-- The choice of the real clock/delay implementation (depending on whether
+-- tasking is involved or not) is done via soft links (see s-soflin.ads)
+
+-- NEVER add any dependency to tasking packages here
+
+package System.OS_Primitives is
+ pragma Preelaborate;
+
+ Max_Sensible_Delay : constant Duration :=
+ Duration'Min (183 * 24 * 60 * 60.0,
+ Duration'Last);
+ -- Max of half a year delay, needed to prevent exceptions for large delay
+ -- values. It seems unlikely that any test will notice this restriction,
+ -- except in the case of applications setting the clock at run time (see
+ -- s-tastim.adb). Also note that a larger value might cause problems (e.g
+ -- overflow, or more likely OS limitation in the primitives used). In the
+ -- case where half a year is too long (which occurs in high integrity mode
+ -- with 32-bit words, and possibly on some specific ports of GNAT),
+ -- Duration'Last is used instead.
+
+ procedure Initialize;
+ -- Initialize global settings related to this package. This procedure
+ -- should be called before any other subprograms in this package. Note
+ -- that this procedure can be called several times.
+
+ function Clock return Duration;
+ pragma Inline (Clock);
+ -- Returns "absolute" time, represented as an offset relative to "the
+ -- Epoch", which is Jan 1, 1970 00:00:00 UTC on UNIX systems. This
+ -- implementation is affected by system's clock changes.
+
+ function Monotonic_Clock return Duration;
+ pragma Inline (Monotonic_Clock);
+ -- Returns "absolute" time, represented as an offset relative to "the Unix
+ -- Epoch", which is Jan 1, 1970 00:00:00 UTC. This clock implementation is
+ -- immune to the system's clock changes.
+
+ Relative : constant := 0;
+ Absolute_Calendar : constant := 1;
+ Absolute_RT : constant := 2;
+ -- Values for Mode call below. Note that the compiler (exp_ch9.adb) relies
+ -- on these values. So any change here must be reflected in corresponding
+ -- changes in the compiler.
+
+ procedure Timed_Delay (Time : Duration; Mode : Integer);
+ -- Implements the semantics of the delay statement when no tasking is used
+ -- in the application.
+ --
+ -- Mode is one of the three values above
+ --
+ -- Time is a relative or absolute duration value, depending on Mode.
+ --
+ -- Note that currently Ada.Real_Time always uses the tasking run time,
+ -- so this procedure should never be called with Mode set to Absolute_RT.
+ -- This may change in future or bare board implementations.
+
+end System.OS_Primitives;