86 lines
4.7 KiB
Ada
86 lines
4.7 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- S Y S T E M . O S _ P R I M I T I V E S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1998-2015, Free Software Foundation, Inc. --
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-- --
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-- GNARL is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNARL was developed by the GNARL team at Florida State University. --
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-- Extensive contributions were provided by Ada Core Technologies, Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package provides low level primitives used to implement clock and
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-- delays in non tasking applications.
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-- The choice of the real clock/delay implementation (depending on whether
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-- tasking is involved or not) is done via soft links (see s-soflin.ads)
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-- NEVER add any dependency to tasking packages here
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package System.OS_Primitives is
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pragma Preelaborate;
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Max_Sensible_Delay : constant Duration :=
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Duration'Min (183 * 24 * 60 * 60.0,
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Duration'Last);
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-- Max of half a year delay, needed to prevent exceptions for large delay
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-- values. It seems unlikely that any test will notice this restriction,
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-- except in the case of applications setting the clock at run time (see
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-- s-tastim.adb). Also note that a larger value might cause problems (e.g
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-- overflow, or more likely OS limitation in the primitives used). In the
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-- case where half a year is too long (which occurs in high integrity mode
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-- with 32-bit words, and possibly on some specific ports of GNAT),
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-- Duration'Last is used instead.
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procedure Initialize;
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-- Initialize global settings related to this package. This procedure
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-- should be called before any other subprograms in this package. Note
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-- that this procedure can be called several times.
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function Clock return Duration;
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pragma Inline (Clock);
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-- Returns "absolute" time, represented as an offset relative to "the
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-- Epoch", which is Jan 1, 1970 00:00:00 UTC on UNIX systems. This
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-- implementation is affected by system's clock changes.
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Relative : constant := 0;
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Absolute_Calendar : constant := 1;
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Absolute_RT : constant := 2;
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-- Values for Mode call below. Note that the compiler (exp_ch9.adb) relies
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-- on these values. So any change here must be reflected in corresponding
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-- changes in the compiler.
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procedure Timed_Delay (Time : Duration; Mode : Integer);
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-- Implements the semantics of the delay statement when no tasking is used
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-- in the application.
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--
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-- Mode is one of the three values above
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--
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-- Time is a relative or absolute duration value, depending on Mode.
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--
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-- Note that currently Ada.Real_Time always uses the tasking run time,
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-- so this procedure should never be called with Mode set to Absolute_RT.
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-- This may change in future or bare board implementations.
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end System.OS_Primitives;
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