226 lines
8.2 KiB
Ada
226 lines
8.2 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- S Y S T E M . O S _ P R I M I T I V E S --
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-- --
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-- B o d y --
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-- --
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-- Copyright (C) 1998-2001 Free Software Foundation, Inc. --
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-- --
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-- GNARL is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 2, or (at your option) any later ver- --
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-- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNARL; see file COPYING. If not, write --
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-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
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-- MA 02111-1307, USA. --
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-- --
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-- As a special exception, if other files instantiate generics from this --
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-- unit, or you link this unit with other files to produce an executable, --
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-- this unit does not by itself cause the resulting executable to be --
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-- covered by the GNU General Public License. This exception does not --
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-- however invalidate any other reasons why the executable file might be --
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-- covered by the GNU Public License. --
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-- --
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-- GNARL was developed by the GNARL team at Florida State University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This is the NT version of this package
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with Ada.Exceptions;
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with System.OS_Interface;
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package body System.OS_Primitives is
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use System.OS_Interface;
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---------------------------------------
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-- Data for the high resolution clock --
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---------------------------------------
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Tick_Frequency : aliased LARGE_INTEGER;
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-- Holds frequency of high-performance counter used by Clock
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-- Windows NT uses a 1_193_182 Hz counter on PCs.
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Base_Ticks : aliased LARGE_INTEGER;
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-- Holds the Tick count for the base time.
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Base_Clock : Duration;
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-- Holds the current clock for the standard clock's base time
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Base_Monotonic_Clock : Duration;
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-- Holds the current clock for monotonic clock's base time
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Base_Time : aliased Long_Long_Integer;
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-- Holds the base time used to check for system time change, used with
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-- the standard clock.
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procedure Get_Base_Time;
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-- Retrieve the base time. This base time will be used by clock to
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-- compute the current time by adding to it a fraction of the
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-- performance counter. This is for the implementation of a
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-- high-resolution clock.
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-----------
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-- Clock --
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-----------
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-- This implementation of clock provides high resolution timer values
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-- using QueryPerformanceCounter. This call return a 64 bits values (based
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-- on the 8253 16 bits counter). This counter is updated every 1/1_193_182
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-- times per seconds. The call to QueryPerformanceCounter takes 6
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-- microsecs to complete.
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function Clock return Duration is
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Max_Shift : constant Duration := 2.0;
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Hundreds_Nano_In_Sec : constant := 1E7;
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Current_Ticks : aliased LARGE_INTEGER;
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Elap_Secs_Tick : Duration;
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Elap_Secs_Sys : Duration;
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Now : aliased Long_Long_Integer;
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begin
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if not QueryPerformanceCounter (Current_Ticks'Access) then
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return 0.0;
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end if;
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GetSystemTimeAsFileTime (Now'Access);
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Elap_Secs_Sys :=
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Duration (abs (Now - Base_Time) / Hundreds_Nano_In_Sec);
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Elap_Secs_Tick :=
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Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
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Long_Long_Float (Tick_Frequency));
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-- If we have a shift of more than Max_Shift seconds we resynchonize the
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-- Clock. This is probably due to a manual Clock adjustment, an DST
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-- adjustment or an NNTP synchronisation. And we want to adjust the
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-- time for this system (non-monotonic) clock.
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if abs (Elap_Secs_Sys - Elap_Secs_Tick) > Max_Shift then
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Get_Base_Time;
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Elap_Secs_Tick :=
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Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
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Long_Long_Float (Tick_Frequency));
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end if;
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return Base_Clock + Elap_Secs_Tick;
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end Clock;
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-------------------
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-- Get_Base_Time --
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-------------------
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procedure Get_Base_Time is
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use System.OS_Interface;
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-- The resolution for GetSystemTime is 1 millisecond.
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-- The time to get both base times should take less than 1 millisecond.
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-- Therefore, the elapsed time reported by GetSystemTime between both
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-- actions should be null.
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Max_Elapsed : constant := 0;
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Test_Now : aliased Long_Long_Integer;
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epoch_1970 : constant := 16#19D_B1DE_D53E_8000#; -- win32 UTC epoch
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system_time_ns : constant := 100; -- 100 ns per tick
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Sec_Unit : constant := 10#1#E9;
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begin
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-- Here we must be sure that both of these calls are done in a short
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-- amount of time. Both are base time and should in theory be taken
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-- at the very same time.
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loop
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GetSystemTimeAsFileTime (Base_Time'Access);
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if not QueryPerformanceCounter (Base_Ticks'Access) then
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pragma Assert
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(Standard.False,
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"Could not query high performance counter in Clock");
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null;
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end if;
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GetSystemTimeAsFileTime (Test_Now'Access);
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exit when Test_Now - Base_Time = Max_Elapsed;
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end loop;
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Base_Clock := Duration
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(Long_Long_Float ((Base_Time - epoch_1970) * system_time_ns) /
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Long_Long_Float (Sec_Unit));
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end Get_Base_Time;
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---------------------
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-- Monotonic_Clock --
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---------------------
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function Monotonic_Clock return Duration is
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Current_Ticks : aliased LARGE_INTEGER;
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Elap_Secs_Tick : Duration;
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begin
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if not QueryPerformanceCounter (Current_Ticks'Access) then
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return 0.0;
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end if;
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Elap_Secs_Tick :=
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Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
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Long_Long_Float (Tick_Frequency));
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return Base_Monotonic_Clock + Elap_Secs_Tick;
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end Monotonic_Clock;
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-----------------
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-- Timed_Delay --
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-----------------
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procedure Timed_Delay (Time : Duration; Mode : Integer) is
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Rel_Time : Duration;
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Abs_Time : Duration;
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Check_Time : Duration := Monotonic_Clock;
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begin
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if Mode = Relative then
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Rel_Time := Time;
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Abs_Time := Time + Check_Time;
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else
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Rel_Time := Time - Check_Time;
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Abs_Time := Time;
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end if;
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if Rel_Time > 0.0 then
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loop
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Sleep (DWORD (Rel_Time * 1000.0));
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Check_Time := Monotonic_Clock;
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exit when Abs_Time <= Check_Time;
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Rel_Time := Abs_Time - Check_Time;
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end loop;
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end if;
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end Timed_Delay;
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-- Package elaboration, get starting time as base
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begin
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if not QueryPerformanceFrequency (Tick_Frequency'Access) then
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Ada.Exceptions.Raise_Exception
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(Program_Error'Identity,
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"cannot get high performance counter frequency");
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end if;
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Get_Base_Time;
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Base_Monotonic_Clock := Base_Clock;
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end System.OS_Primitives;
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