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------------------------------------------------------------------------------
-- --
-- GNAT 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 --
-- --
-- Copyright (C) 1998-2005 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, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, 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 is the NT version of this package
with Ada.Exceptions;
with Interfaces.C;
package body System.OS_Primitives is
---------------------------
-- Win32 API Definitions --
---------------------------
-- These definitions are copied from System.OS_Interface because we do not
-- want to depend on gnarl here.
type DWORD is new Interfaces.C.unsigned_long;
type LARGE_INTEGER is delta 1.0 range -2.0**63 .. 2.0**63 - 1.0;
type BOOL is new Boolean;
for BOOL'Size use Interfaces.C.unsigned_long'Size;
procedure GetSystemTimeAsFileTime (lpFileTime : access Long_Long_Integer);
pragma Import (Stdcall, GetSystemTimeAsFileTime, "GetSystemTimeAsFileTime");
function QueryPerformanceCounter
(lpPerformanceCount : access LARGE_INTEGER) return BOOL;
pragma Import
(Stdcall, QueryPerformanceCounter, "QueryPerformanceCounter");
function QueryPerformanceFrequency
(lpFrequency : access LARGE_INTEGER) return BOOL;
pragma Import
(Stdcall, QueryPerformanceFrequency, "QueryPerformanceFrequency");
procedure Sleep (dwMilliseconds : DWORD);
pragma Import (Stdcall, Sleep, External_Name => "Sleep");
----------------------------------------
-- Data for the high resolution clock --
----------------------------------------
-- Declare some pointers to access multi-word data above. This is needed
-- to workaround a limitation in the GNU/Linker auto-import feature used
-- to build the GNAT runtime DLLs. In fact the Clock and Monotonic_Clock
-- routines are inlined and they are using some multi-word variables.
-- GNU/Linker will fail to auto-import those variables when building
-- libgnarl.dll. The indirection level introduced here has no measurable
-- penalties.
--
-- Note that access variables below must not be declared as constant
-- otherwise the compiler optimization will remove this indirect access.
type DA is access all Duration;
-- Use to have indirect access to multi-word variables
type LIA is access all LARGE_INTEGER;
-- Use to have indirect access to multi-word variables
type LLIA is access all Long_Long_Integer;
-- Use to have indirect access to multi-word variables
Tick_Frequency : aliased LARGE_INTEGER;
TFA : constant LIA := Tick_Frequency'Access;
-- 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;
BTA : constant LIA := Base_Ticks'Access;
-- Holds the Tick count for the base time.
Base_Monotonic_Ticks : aliased LARGE_INTEGER;
BMTA : constant LIA := Base_Monotonic_Ticks'Access;
-- Holds the Tick count for the base monotonic time
Base_Clock : aliased Duration;
BCA : constant DA := Base_Clock'Access;
-- Holds the current clock for the standard clock's base time
Base_Monotonic_Clock : aliased Duration;
BMCA : constant DA := Base_Monotonic_Clock'Access;
-- Holds the current clock for monotonic clock's base time
Base_Time : aliased Long_Long_Integer;
BTiA : constant LLIA := Base_Time'Access;
-- Holds the base time used to check for system time change, used with
-- the standard clock.
procedure Get_Base_Time;
-- Retrieve the base time and base ticks. These values 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. Note that this routine does not change the base
-- monotonic values used by the monotonic clock.
-----------
-- Clock --
-----------
-- 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
-- times per seconds. The call to QueryPerformanceCounter takes 6
-- microsecs to complete.
function Clock return Duration is
Max_Shift : constant Duration := 2.0;
Hundreds_Nano_In_Sec : constant Long_Long_Float := 1.0E7;
Current_Ticks : aliased LARGE_INTEGER;
Elap_Secs_Tick : Duration;
Elap_Secs_Sys : Duration;
Now : aliased Long_Long_Integer;
begin
if not QueryPerformanceCounter (Current_Ticks'Access) then
return 0.0;
end if;
GetSystemTimeAsFileTime (Now'Access);
Elap_Secs_Sys :=
Duration (Long_Long_Float (abs (Now - BTiA.all)) /
Hundreds_Nano_In_Sec);
Elap_Secs_Tick :=
Duration (Long_Long_Float (Current_Ticks - BTA.all) /
Long_Long_Float (TFA.all));
-- 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 NTP synchronisation. And we want to adjust the
-- time for this system (non-monotonic) clock.
if abs (Elap_Secs_Sys - Elap_Secs_Tick) > Max_Shift then
Get_Base_Time;
Elap_Secs_Tick :=
Duration (Long_Long_Float (Current_Ticks - BTA.all) /
Long_Long_Float (TFA.all));
end if;
return BCA.all + Elap_Secs_Tick;
end Clock;
-------------------
-- Get_Base_Time --
-------------------
procedure Get_Base_Time is
-- The resolution for GetSystemTime is 1 millisecond.
-- 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;
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
GetSystemTimeAsFileTime (Base_Time'Access);
if not QueryPerformanceCounter (Base_Ticks'Access) then
pragma Assert
(Standard.False,
"Could not query high performance counter in Clock");
null;
end if;
GetSystemTimeAsFileTime (Test_Now'Access);
exit when Test_Now - Base_Time = Max_Elapsed;
end loop;
Base_Clock := Duration
(Long_Long_Float ((Base_Time - epoch_1970) * system_time_ns) /
Long_Long_Float (Sec_Unit));
end Get_Base_Time;
---------------------
-- Monotonic_Clock --
---------------------
function Monotonic_Clock return Duration is
Current_Ticks : aliased LARGE_INTEGER;
Elap_Secs_Tick : Duration;
begin
if not QueryPerformanceCounter (Current_Ticks'Access) then
return 0.0;
end if;
Elap_Secs_Tick :=
Duration (Long_Long_Float (Current_Ticks - BMTA.all) /
Long_Long_Float (TFA.all));
return BMCA.all + Elap_Secs_Tick;
end Monotonic_Clock;
-----------------
-- Timed_Delay --
-----------------
procedure Timed_Delay (Time : Duration; Mode : Integer) is
Rel_Time : Duration;
Abs_Time : Duration;
Check_Time : Duration := Monotonic_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 := Monotonic_Clock;
exit when Abs_Time <= Check_Time;
Rel_Time := Abs_Time - Check_Time;
end loop;
end if;
end Timed_Delay;
-- Package elaboration, get starting time as base
begin
if not QueryPerformanceFrequency (Tick_Frequency'Access) then
Ada.Exceptions.Raise_Exception
(Program_Error'Identity,
"cannot get high performance counter frequency");
end if;
Get_Base_Time;
-- Keep base clock and ticks for the monotonic clock. These values should
-- never be changed to ensure proper behavior of the monotonic clock.
Base_Monotonic_Clock := Base_Clock;
Base_Monotonic_Ticks := Base_Ticks;
end System.OS_Primitives;
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