------------------------------------------------------------------------------ -- -- -- 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) 1998-2013, 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 3, or (at your option) any later ver- -- -- sion. GNAT 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. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- 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 System.Task_Lock; with System.Win32.Ext; package body System.OS_Primitives is use System.Task_Lock; use System.Win32; use System.Win32.Ext; ---------------------------------------- -- Data for the high resolution 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_Monotonic_Ticks : LARGE_INTEGER; -- Holds the Tick count for the base monotonic time Base_Monotonic_Clock : Duration; -- Holds the current clock for monotonic clock's base time type Clock_Data is record Base_Ticks : LARGE_INTEGER; -- Holds the Tick count for the base time Base_Time : Long_Long_Integer; -- Holds the base time used to check for system time change, used with -- the standard clock. Base_Clock : Duration; -- Holds the current clock for the standard clock's base time end record; type Clock_Data_Access is access all Clock_Data; -- Two base clock buffers. This is used to be able to update a buffer while -- the other buffer is read. The point is that we do not want to use a lock -- inside the Clock routine for performance reasons. We still use a lock -- in the Get_Base_Time which is called very rarely. Current is a pointer, -- the pragma Atomic is there to ensure that the value can be set or read -- atomically. That's it, when Get_Base_Time has updated a buffer the -- switch to the new value is done by changing Current pointer. First, Second : aliased Clock_Data; Current : Clock_Data_Access := First'Access; pragma Atomic (Current); -- The following signature is to detect change on the base clock data -- above. The signature is a modular type, it will wrap around without -- raising an exception. We would need to have exactly 2**32 updates of -- the base data for the changes to get undetected. type Signature_Type is mod 2**32; Signature : Signature_Type := 0; pragma Atomic (Signature); procedure Get_Base_Time (Data : out Clock_Data); -- 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; Data : Clock_Data; Current_Ticks : aliased LARGE_INTEGER; Elap_Secs_Tick : Duration; Elap_Secs_Sys : Duration; Now : aliased Long_Long_Integer; Sig1, Sig2 : Signature_Type; begin -- Try ten times to get a coherent set of base data. For this we just -- check that the signature hasn't changed during the copy of the -- current data. -- -- This loop will always be done once if there is no interleaved call -- to Get_Base_Time. for K in 1 .. 10 loop Sig1 := Signature; Data := Current.all; Sig2 := Signature; exit when Sig1 = Sig2; end loop; if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then return 0.0; end if; GetSystemTimeAsFileTime (Now'Access); Elap_Secs_Sys := Duration (Long_Long_Float (abs (Now - Data.Base_Time)) / Hundreds_Nano_In_Sec); Elap_Secs_Tick := Duration (Long_Long_Float (Current_Ticks - Data.Base_Ticks) / Long_Long_Float (Tick_Frequency)); -- If we have a shift of more than Max_Shift seconds we resynchronize -- the Clock. This is probably due to a manual Clock adjustment, a 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 (Data); Elap_Secs_Tick := Duration (Long_Long_Float (Current_Ticks - Data.Base_Ticks) / Long_Long_Float (Tick_Frequency)); end if; return Data.Base_Clock + Elap_Secs_Tick; end Clock; ------------------- -- Get_Base_Time -- ------------------- procedure Get_Base_Time (Data : out Clock_Data) 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. 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; Max_Elapsed : constant LARGE_INTEGER := LARGE_INTEGER (Tick_Frequency / 100_000); -- Look for a precision of 0.01 ms Sig : constant Signature_Type := Signature; Loc_Ticks, Ctrl_Ticks : aliased LARGE_INTEGER; Loc_Time, Ctrl_Time : aliased Long_Long_Integer; Elapsed : LARGE_INTEGER; Current_Max : LARGE_INTEGER := LARGE_INTEGER'Last; New_Data : Clock_Data_Access; 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. -- The goal of the following loop is to synchronize the system time -- with the Win32 performance counter by getting a base offset for both. -- Using these offsets it is then possible to compute actual time using -- a performance counter which has a better precision than the Win32 -- time API. -- Try at most 10 times to reach the best synchronisation (below 1 -- millisecond) otherwise the runtime will use the best value reached -- during the runs. Lock; -- First check that the current value has not been updated. This -- could happen if another task has called Clock at the same time -- and that Max_Shift has been reached too. -- -- But if the current value has been changed just before we entered -- into the critical section, we can safely return as the current -- base data (time, clock, ticks) have already been updated. if Sig /= Signature then return; end if; -- Check for the unused data buffer and set New_Data to point to it if Current = First'Access then New_Data := Second'Access; else New_Data := First'Access; end if; for K in 1 .. 10 loop if QueryPerformanceCounter (Loc_Ticks'Access) = Win32.FALSE then pragma Assert (Standard.False, "Could not query high performance counter in Clock"); null; end if; GetSystemTimeAsFileTime (Ctrl_Time'Access); -- Scan for clock tick, will take up to 16ms/1ms depending on PC. -- This cannot be an infinite loop or the system hardware is badly -- damaged. loop GetSystemTimeAsFileTime (Loc_Time'Access); if QueryPerformanceCounter (Ctrl_Ticks'Access) = Win32.FALSE then pragma Assert (Standard.False, "Could not query high performance counter in Clock"); null; end if; exit when Loc_Time /= Ctrl_Time; Loc_Ticks := Ctrl_Ticks; end loop; -- Check elapsed Performance Counter between samples -- to choose the best one. Elapsed := Ctrl_Ticks - Loc_Ticks; if Elapsed < Current_Max then New_Data.Base_Time := Loc_Time; New_Data.Base_Ticks := Loc_Ticks; Current_Max := Elapsed; -- Exit the loop when we have reached the expected precision exit when Elapsed <= Max_Elapsed; end if; end loop; New_Data.Base_Clock := Duration (Long_Long_Float ((New_Data.Base_Time - epoch_1970) * system_time_ns) / Long_Long_Float (Sec_Unit)); -- At this point all the base values have been set into the new data -- record. Change the pointer (atomic operation) to these new values. Current := New_Data; Data := New_Data.all; -- Set new signature for this data set Signature := Signature + 1; Unlock; exception when others => Unlock; raise; end Get_Base_Time; --------------------- -- Monotonic_Clock -- --------------------- function Monotonic_Clock return Duration is Current_Ticks : aliased LARGE_INTEGER; Elap_Secs_Tick : Duration; begin if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then return 0.0; else Elap_Secs_Tick := Duration (Long_Long_Float (Current_Ticks - Base_Monotonic_Ticks) / Long_Long_Float (Tick_Frequency)); return Base_Monotonic_Clock + Elap_Secs_Tick; end if; end Monotonic_Clock; ----------------- -- Timed_Delay -- ----------------- procedure Timed_Delay (Time : Duration; Mode : Integer) is function Mode_Clock return Duration; pragma Inline (Mode_Clock); -- Return the current clock value using either the monotonic clock or -- standard clock depending on the Mode value. ---------------- -- Mode_Clock -- ---------------- function Mode_Clock return Duration is begin case Mode is when Absolute_RT => return Monotonic_Clock; when others => return Clock; end case; end Mode_Clock; -- Local Variables Base_Time : constant Duration := Mode_Clock; -- Base_Time is used to detect clock set backward, in this case we -- cannot ensure the delay accuracy. Rel_Time : Duration; Abs_Time : Duration; Check_Time : Duration := Base_Time; -- Start of processing for Timed Delay 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 := Mode_Clock; exit when Abs_Time <= Check_Time or else Check_Time < Base_Time; Rel_Time := Abs_Time - Check_Time; end loop; end if; end Timed_Delay; ---------------- -- Initialize -- ---------------- Initialized : Boolean := False; procedure Initialize is begin if Initialized then return; end if; Initialized := True; -- Get starting time as base if QueryPerformanceFrequency (Tick_Frequency'Access) = Win32.FALSE then raise Program_Error with "cannot get high performance counter frequency"; end if; Get_Base_Time (Current.all); -- 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 := Current.Base_Clock; Base_Monotonic_Ticks := Current.Base_Ticks; end Initialize; end System.OS_Primitives;