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) 1998-2015, 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. 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 40package System.OS_Primitives is 41 pragma Preelaborate; 42 43 Max_Sensible_Delay : constant Duration := 44 Duration'Min (183 * 24 * 60 * 60.0, 45 Duration'Last); 46 -- Max of half a year delay, needed to prevent exceptions for large delay 47 -- values. It seems unlikely that any test will notice this restriction, 48 -- except in the case of applications setting the clock at run time (see 49 -- s-tastim.adb). Also note that a larger value might cause problems (e.g 50 -- overflow, or more likely OS limitation in the primitives used). In the 51 -- case where half a year is too long (which occurs in high integrity mode 52 -- with 32-bit words, and possibly on some specific ports of GNAT), 53 -- Duration'Last is used instead. 54 55 procedure Initialize; 56 -- Initialize global settings related to this package. This procedure 57 -- should be called before any other subprograms in this package. Note 58 -- that this procedure can be called several times. 59 60 function Clock return Duration; 61 pragma Inline (Clock); 62 -- Returns "absolute" time, represented as an offset relative to "the 63 -- Epoch", which is Jan 1, 1970 00:00:00 UTC on UNIX systems. This 64 -- implementation is affected by system's clock changes. 65 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) relies 70 -- on these values. So any change here must be reflected in corresponding 71 -- changes in the compiler. 72 73 procedure Timed_Delay (Time : Duration; Mode : Integer); 74 -- Implements the semantics of the delay statement when no tasking is used 75 -- in the application. 76 -- 77 -- Mode is one of the three values above 78 -- 79 -- Time is a relative or absolute duration value, depending on Mode. 80 -- 81 -- Note that currently Ada.Real_Time always uses the tasking run time, 82 -- so this procedure should never be called with Mode set to Absolute_RT. 83 -- This may change in future or bare board implementations. 84 85end System.OS_Primitives; 86