File : s-osprim.adb
------------------------------------------------------------------------------
-- --
-- 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 --
-- --
-- B o d y --
-- --
-- $Revision: 1.6 $ --
-- --
-- Copyright (C) 1998-1999 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. It is --
-- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
-- State University (http://www.gnat.com). --
-- --
------------------------------------------------------------------------------
-- This is the NT version of this package
with System.OS_Interface;
with System.Error_Reporting;
-- used for Shutdown
package body System.OS_Primitives is
use System.OS_Interface;
use System.Error_Reporting;
---------------------------------------
-- Data for the high resoltion clock --
---------------------------------------
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;
-- Holds the Tick count for the base time.
Base_Clock : Duration;
-- Holds the current clock for the base time.
procedure Get_Base_Time;
-- Retreive the base time. This base time will be used by clock to
-- compute the current time by adding to it a fraction of the
-- performance counter. This is for the implementation of a
-- high-resolution clock.
-----------
-- Clock --
-----------
-- this is a high resolution clock implemented 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
-- times per seconds. The call to QueryPerformanceCounter takes 6
-- microsecs to complete.
function Clock return Duration is
Current_Ticks : aliased LARGE_INTEGER;
begin
if not QueryPerformanceCounter (Current_Ticks'Access) then
return 0.0;
end if;
return Base_Clock +
Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
Long_Long_Float (Tick_Frequency));
end Clock;
-------------------
-- Get_Base_Time --
-------------------
procedure Get_Base_Time is
use System.OS_Interface;
-- the resolution for GetSystemTime is 1 millisec.
-- the time to get both bases times should take less that 1 millisec.
-- so the elapsed time reported by GetSystemTime between both
-- actions should be null.
Max_Elapsed : constant := 0;
Systime : aliased SYSTEMTIME;
Test_Systime : aliased SYSTEMTIME;
Now : aliased Long_Long_Integer;
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
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
-- at the very same time.
loop
GetSystemTime (Systime'Access);
if not QueryPerformanceCounter (Base_Ticks'Access) then
pragma Assert
(Shutdown
("Could not query high performance counter in Clock"));
null;
end if;
GetSystemTime (Test_Systime'Access);
-- compute the time between both call to GetSystemTime and try again
-- if the time between both are above Max_Elapsed.
if not SystemTimeToFileTime (Systime'Access, Now'Access) then
pragma Assert
(Shutdown
("Call to SystemTimeToFileTime failed"));
null;
end if;
if SystemTimeToFileTime (Test_Systime'Access, Test_Now'Access) then
pragma Assert
(Shutdown
("Call to SystemTimeToFileTime failed"));
null;
end if;
exit when (Test_Now - Now) = Max_Elapsed;
end loop;
Base_Clock := Duration
(Long_Long_Float ((Now - epoch_1970) * system_time_ns) /
Long_Long_Float (Sec_Unit));
end Get_Base_Time;
-----------------
-- Timed_Delay --
-----------------
procedure Timed_Delay
(Time : Duration;
Mode : Integer)
is
Rel_Time : Duration;
Abs_Time : Duration;
Check_Time : Duration := Clock;
begin
if Mode = Relative then
Rel_Time := Time;
Abs_Time := Time + Check_Time;
else
Rel_Time := Time - Check_Time;
Abs_Time := Time;
end if;
if Rel_Time > 0.0 then
loop
Sleep (DWORD (Rel_Time * 1000.0));
Check_Time := Clock;
exit when Abs_Time <= Check_Time;
Rel_Time := Abs_Time - Check_Time;
end loop;
end if;
end Timed_Delay;
begin
if not QueryPerformanceFrequency (Tick_Frequency'Access) then
pragma Assert
(Shutdown ("cannot get high performance counter frequency"));
null;
end if;
Get_Base_Time;
end System.OS_Primitives;