-- Therefore, the elapsed time reported by GetSystemTime between both
-- actions should be null.
- Max_Elapsed : constant := 0;
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;
- Test_Now : aliased Long_Long_Integer;
- Loc_Ticks : aliased LARGE_INTEGER;
- Loc_Time : aliased Long_Long_Integer;
- Elapsed : Long_Long_Integer;
- Current_Max : Long_Long_Integer := Long_Long_Integer'Last;
+ Max_Elapsed : constant LARGE_INTEGER :=
+ LARGE_INTEGER (Tick_Frequency / 100_000);
+ -- Look for a precision of 0.01 ms
+
+ 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;
begin
-- Here we must be sure that both of these calls are done in a short
-- during the runs.
for K in 1 .. 10 loop
- GetSystemTimeAsFileTime (Loc_Time'Access);
-
if QueryPerformanceCounter (Loc_Ticks'Access) = Win32.FALSE then
pragma Assert
(Standard.False,
null;
end if;
- GetSystemTimeAsFileTime (Test_Now'Access);
+ GetSystemTimeAsFileTime (Ctrl_Time'Access);
+
+ -- Scan for clock tick, will take upto 16ms/1ms depending on PC.
+ -- This cannot be an infinite loop or the system hardware is badly
+ -- dammaged.
+
+ 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;
- Elapsed := Test_Now - Loc_Time;
+ 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
Base_Time := Loc_Time;
Base_Ticks := Loc_Ticks;
Current_Max := Elapsed;
- end if;
- exit when Elapsed = Max_Elapsed;
+ -- Exit the loop when we have reached the expected precision
+
+ exit when Elapsed <= Max_Elapsed;
+ end if;
end loop;
Base_Clock := Duration