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 40package 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 110end System.OS_Primitives; 111