------------------------------------------------------------------------------ -- -- -- GNU ADA 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) 1998-2003 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, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, 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 on Alpha/VMS -- The choice of the real clock/delay implementation (depending on whether -- tasking is involved or not) is done via soft links (see s-tasoli.ads) -- NEVER add any dependency to tasking packages here package System.OS_Primitives is subtype OS_Time is Long_Integer; -- System time on VMS is used for performance reasons. -- Note that OS_Time is *not* the same as Ada.Calendar.Time, the -- difference being that relative OS_Time is negative, but relative -- Calendar.Time is positive. -- See Ada.Calendar.Delays for more information on VMS Time. 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 -- 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. function OS_Clock return OS_Time; -- Returns "absolute" time, represented as an offset -- relative to "the Epoch", which is Nov 17, 1858 on VMS. function Clock return Duration; pragma Inline (Clock); -- Returns "absolute" time, represented as an offset -- relative to "the Epoch", which is Jan 1, 1970 on unixes. -- 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 Epoch", which is Jan 1, 1970. -- 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. function To_Duration (T : OS_Time; Mode : Integer) return Duration; -- Convert VMS system time to Duration -- Mode is one of the three values above function To_OS_Time (D : Duration; Mode : Integer) return OS_Time; -- Convert Duration to VMS system time -- Mode is one of the three values above end System.OS_Primitives;