File : s-osprim.adb
------------------------------------------------------------------------------
-- --
-- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
5 -- S Y S T E M . O S _ P R I M I T I V E S --
-- --
-- B o d y --
-- --
-- $Revision: 1.13 $ --
10 -- --
-- Copyright (C) 1998-2001 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- --
15 -- 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 --
20 -- 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 --
25 -- 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. --
30 -- --
-- GNARL was developed by the GNARL team at Florida State University. It is --
-- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
-- State University (http://www.gnat.com). --
-- --
35 ------------------------------------------------------------------------------
-- This is the NT version of this package
with Ada.Exceptions;
40 with System.OS_Interface;
package body System.OS_Primitives is
use System.OS_Interface;
45
---------------------------------------
-- Data for the high resolution clock --
---------------------------------------
50 Tick_Frequency : aliased LARGE_INTEGER;
-- Holds frequency of high-performance counter used by Clock
-- Windows NT uses a 1_193_182 Hz counter on PCs.
Base_Ticks : aliased LARGE_INTEGER;
55 -- Holds the Tick count for the base time.
Base_Clock : Duration;
-- Holds the current clock for the standard clock's base time
60 Base_Monotonic_Clock : Duration;
-- Holds the current clock for monotonic clock's base time
Base_Time : aliased Long_Long_Integer;
-- Holds the base time used to check for system time change, used with
65 -- the standard clock.
procedure Get_Base_Time;
-- Retrieve the base time. This base time will be used by clock to
-- compute the current time by adding to it a fraction of the
70 -- performance counter. This is for the implementation of a
-- high-resolution clock.
-----------
-- Clock --
75 -----------
-- This implementation of clock provides high resolution timer values
-- using QueryPerformanceCounter. This call return a 64 bits values (based
-- on the 8253 16 bits counter). This counter is updated every 1/1_193_182
80 -- times per seconds. The call to QueryPerformanceCounter takes 6
-- microsecs to complete.
function Clock return Duration is
Max_Shift : constant Duration := 2.0;
85 Hundreds_Nano_In_Sec : constant := 1E7;
Current_Ticks : aliased LARGE_INTEGER;
Elap_Secs_Tick : Duration;
Elap_Secs_Sys : Duration;
Now : aliased Long_Long_Integer;
90
begin
if not QueryPerformanceCounter (Current_Ticks'Access) then
return 0.0;
end if;
95
GetSystemTimeAsFileTime (Now'Access);
Elap_Secs_Sys :=
Duration (abs (Now - Base_Time) / Hundreds_Nano_In_Sec);
100
Elap_Secs_Tick :=
Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
Long_Long_Float (Tick_Frequency));
105 -- If we have a shift of more than Max_Shift seconds we resynchonize the
-- Clock. This is probably due to a manual Clock adjustment, an DST
-- adjustment or an NNTP synchronisation. And we want to adjust the
-- time for this system (non-monotonic) clock.
110 if abs (Elap_Secs_Sys - Elap_Secs_Tick) > Max_Shift then
Get_Base_Time;
Elap_Secs_Tick :=
Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
115 Long_Long_Float (Tick_Frequency));
end if;
return Base_Clock + Elap_Secs_Tick;
end Clock;
120
-------------------
-- Get_Base_Time --
-------------------
125 procedure Get_Base_Time is
use System.OS_Interface;
-- The resolution for GetSystemTime is 1 millisecond.
130 -- The time to get both base times should take less than 1 millisecond.
-- Therefore, the elapsed time reported by GetSystemTime between both
-- actions should be null.
Max_Elapsed : constant := 0;
135
Test_Now : aliased Long_Long_Integer;
epoch_1970 : constant := 16#19D_B1DE_D53E_8000#; -- win32 UTC epoch
system_time_ns : constant := 100; -- 100 ns per tick
140 Sec_Unit : constant := 10#1#E9;
begin
-- Here we must be sure that both of these calls are done in a short
-- amount of time. Both are base time and should in theory be taken
145 -- at the very same time.
loop
GetSystemTimeAsFileTime (Base_Time'Access);
150 if not QueryPerformanceCounter (Base_Ticks'Access) then
pragma Assert
(Standard.False,
"Could not query high performance counter in Clock");
null;
155 end if;
GetSystemTimeAsFileTime (Test_Now'Access);
exit when Test_Now - Base_Time = Max_Elapsed;
160 end loop;
Base_Clock := Duration
(Long_Long_Float ((Base_Time - epoch_1970) * system_time_ns) /
Long_Long_Float (Sec_Unit));
165 end Get_Base_Time;
---------------------
-- Monotonic_Clock --
---------------------
170
function Monotonic_Clock return Duration is
Current_Ticks : aliased LARGE_INTEGER;
Elap_Secs_Tick : Duration;
begin
175 if not QueryPerformanceCounter (Current_Ticks'Access) then
return 0.0;
end if;
Elap_Secs_Tick :=
180 Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
Long_Long_Float (Tick_Frequency));
return Base_Monotonic_Clock + Elap_Secs_Tick;
end Monotonic_Clock;
185
-----------------
-- Timed_Delay --
-----------------
190 procedure Timed_Delay (Time : Duration; Mode : Integer) is
Rel_Time : Duration;
Abs_Time : Duration;
Check_Time : Duration := Monotonic_Clock;
195 begin
if Mode = Relative then
Rel_Time := Time;
Abs_Time := Time + Check_Time;
else
200 Rel_Time := Time - Check_Time;
Abs_Time := Time;
end if;
if Rel_Time > 0.0 then
205 loop
Sleep (DWORD (Rel_Time * 1000.0));
Check_Time := Monotonic_Clock;
exit when Abs_Time <= Check_Time;
210
Rel_Time := Abs_Time - Check_Time;
end loop;
end if;
end Timed_Delay;
215
-- Package elaboration, get starting time as base
begin
if not QueryPerformanceFrequency (Tick_Frequency'Access) then
220 Ada.Exceptions.Raise_Exception
(Program_Error'Identity,
"cannot get high performance counter frequency");
end if;
225 Get_Base_Time;
Base_Monotonic_Clock := Base_Clock;
end System.OS_Primitives;