1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . O S _ P R I M I T I V E S --
9 -- Copyright (C) 1998-2009, Free Software Foundation, Inc. --
11 -- GNARL is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
18 -- As a special exception under Section 7 of GPL version 3, you are granted --
19 -- additional permissions described in the GCC Runtime Library Exception, --
20 -- version 3.1, as published by the Free Software Foundation. --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
27 -- GNARL was developed by the GNARL team at Florida State University. --
28 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
30 ------------------------------------------------------------------------------
32 -- This is the NT version of this package
34 with System
.Win32
.Ext
;
36 package body System
.OS_Primitives
is
41 ----------------------------------------
42 -- Data for the high resolution clock --
43 ----------------------------------------
45 -- Declare some pointers to access multi-word data above. This is needed
46 -- to workaround a limitation in the GNU/Linker auto-import feature used
47 -- to build the GNAT runtime DLLs. In fact the Clock and Monotonic_Clock
48 -- routines are inlined and they are using some multi-word variables.
49 -- GNU/Linker will fail to auto-import those variables when building
50 -- libgnarl.dll. The indirection level introduced here has no measurable
53 -- Note that access variables below must not be declared as constant
54 -- otherwise the compiler optimization will remove this indirect access.
56 type DA
is access all Duration;
57 -- Use to have indirect access to multi-word variables
59 type LIA
is access all LARGE_INTEGER
;
60 -- Use to have indirect access to multi-word variables
62 type LLIA
is access all Long_Long_Integer;
63 -- Use to have indirect access to multi-word variables
65 Tick_Frequency
: aliased LARGE_INTEGER
;
66 TFA
: constant LIA
:= Tick_Frequency
'Access;
67 -- Holds frequency of high-performance counter used by Clock
68 -- Windows NT uses a 1_193_182 Hz counter on PCs.
70 Base_Ticks
: aliased LARGE_INTEGER
;
71 BTA
: constant LIA
:= Base_Ticks
'Access;
72 -- Holds the Tick count for the base time
74 Base_Monotonic_Ticks
: aliased LARGE_INTEGER
;
75 BMTA
: constant LIA
:= Base_Monotonic_Ticks
'Access;
76 -- Holds the Tick count for the base monotonic time
78 Base_Clock
: aliased Duration;
79 BCA
: constant DA
:= Base_Clock
'Access;
80 -- Holds the current clock for the standard clock's base time
82 Base_Monotonic_Clock
: aliased Duration;
83 BMCA
: constant DA
:= Base_Monotonic_Clock
'Access;
84 -- Holds the current clock for monotonic clock's base time
86 Base_Time
: aliased Long_Long_Integer;
87 BTiA
: constant LLIA
:= Base_Time
'Access;
88 -- Holds the base time used to check for system time change, used with
89 -- the standard clock.
91 procedure Get_Base_Time
;
92 -- Retrieve the base time and base ticks. These values will be used by
93 -- clock to compute the current time by adding to it a fraction of the
94 -- performance counter. This is for the implementation of a
95 -- high-resolution clock. Note that this routine does not change the base
96 -- monotonic values used by the monotonic clock.
102 -- This implementation of clock provides high resolution timer values
103 -- using QueryPerformanceCounter. This call return a 64 bits values (based
104 -- on the 8253 16 bits counter). This counter is updated every 1/1_193_182
105 -- times per seconds. The call to QueryPerformanceCounter takes 6
106 -- microsecs to complete.
108 function Clock
return Duration is
109 Max_Shift
: constant Duration := 2.0;
110 Hundreds_Nano_In_Sec
: constant Long_Long_Float := 1.0E7
;
111 Current_Ticks
: aliased LARGE_INTEGER
;
112 Elap_Secs_Tick
: Duration;
113 Elap_Secs_Sys
: Duration;
114 Now
: aliased Long_Long_Integer;
117 if QueryPerformanceCounter
(Current_Ticks
'Access) = Win32
.FALSE then
121 GetSystemTimeAsFileTime
(Now
'Access);
124 Duration (Long_Long_Float (abs (Now
- BTiA
.all)) /
125 Hundreds_Nano_In_Sec
);
128 Duration (Long_Long_Float (Current_Ticks
- BTA
.all) /
129 Long_Long_Float (TFA
.all));
131 -- If we have a shift of more than Max_Shift seconds we resynchronize
132 -- the Clock. This is probably due to a manual Clock adjustment, an
133 -- DST adjustment or an NTP synchronisation. And we want to adjust the
134 -- time for this system (non-monotonic) clock.
136 if abs (Elap_Secs_Sys
- Elap_Secs_Tick
) > Max_Shift
then
140 Duration (Long_Long_Float (Current_Ticks
- BTA
.all) /
141 Long_Long_Float (TFA
.all));
144 return BCA
.all + Elap_Secs_Tick
;
151 procedure Get_Base_Time
is
153 -- The resolution for GetSystemTime is 1 millisecond
155 -- The time to get both base times should take less than 1 millisecond.
156 -- Therefore, the elapsed time reported by GetSystemTime between both
157 -- actions should be null.
159 Max_Elapsed
: constant := 0;
160 epoch_1970
: constant := 16#
19D_B1DE_D53E_8000#
; -- win32 UTC epoch
161 system_time_ns
: constant := 100; -- 100 ns per tick
162 Sec_Unit
: constant := 10#
1#E9
;
163 Test_Now
: aliased Long_Long_Integer;
164 Loc_Ticks
: aliased LARGE_INTEGER
;
165 Loc_Time
: aliased Long_Long_Integer;
166 Elapsed
: Long_Long_Integer;
167 Current_Max
: Long_Long_Integer := Long_Long_Integer'Last;
170 -- Here we must be sure that both of these calls are done in a short
171 -- amount of time. Both are base time and should in theory be taken
172 -- at the very same time.
174 -- The goal of the following loop is to synchronize the system time
175 -- with the Win32 performance counter by getting a base offset for both.
176 -- Using these offsets it is then possible to compute actual time using
177 -- a performance counter which has a better precision than the Win32
180 -- Try at most 10th times to reach the best synchronisation (below 1
181 -- millisecond) otherwise the runtime will use the best value reached
184 for K
in 1 .. 10 loop
185 GetSystemTimeAsFileTime
(Loc_Time
'Access);
187 if QueryPerformanceCounter
(Loc_Ticks
'Access) = Win32
.FALSE then
190 "Could not query high performance counter in Clock");
194 GetSystemTimeAsFileTime
(Test_Now
'Access);
196 Elapsed
:= Test_Now
- Loc_Time
;
198 if Elapsed
< Current_Max
then
199 Base_Time
:= Loc_Time
;
200 Base_Ticks
:= Loc_Ticks
;
201 Current_Max
:= Elapsed
;
204 exit when Elapsed
= Max_Elapsed
;
207 Base_Clock
:= Duration
208 (Long_Long_Float ((Base_Time
- epoch_1970
) * system_time_ns
) /
209 Long_Long_Float (Sec_Unit
));
212 ---------------------
213 -- Monotonic_Clock --
214 ---------------------
216 function Monotonic_Clock
return Duration is
217 Current_Ticks
: aliased LARGE_INTEGER
;
218 Elap_Secs_Tick
: Duration;
220 if QueryPerformanceCounter
(Current_Ticks
'Access) = Win32
.FALSE then
224 Duration (Long_Long_Float (Current_Ticks
- BMTA
.all) /
225 Long_Long_Float (TFA
.all));
226 return BMCA
.all + Elap_Secs_Tick
;
234 procedure Timed_Delay
(Time
: Duration; Mode
: Integer) is
236 function Mode_Clock
return Duration;
237 pragma Inline
(Mode_Clock
);
238 -- Return the current clock value using either the monotonic clock or
239 -- standard clock depending on the Mode value.
245 function Mode_Clock
return Duration is
249 return Monotonic_Clock
;
257 Base_Time
: constant Duration := Mode_Clock
;
258 -- Base_Time is used to detect clock set backward, in this case we
259 -- cannot ensure the delay accuracy.
263 Check_Time
: Duration := Base_Time
;
265 -- Start of processing for Timed Delay
268 if Mode
= Relative
then
270 Abs_Time
:= Time
+ Check_Time
;
272 Rel_Time
:= Time
- Check_Time
;
276 if Rel_Time
> 0.0 then
278 Sleep
(DWORD
(Rel_Time
* 1000.0));
279 Check_Time
:= Mode_Clock
;
281 exit when Abs_Time
<= Check_Time
or else Check_Time
< Base_Time
;
283 Rel_Time
:= Abs_Time
- Check_Time
;
292 Initialized
: Boolean := False;
294 procedure Initialize
is
302 -- Get starting time as base
304 if QueryPerformanceFrequency
(Tick_Frequency
'Access) = Win32
.FALSE then
305 raise Program_Error
with
306 "cannot get high performance counter frequency";
311 -- Keep base clock and ticks for the monotonic clock. These values
312 -- should never be changed to ensure proper behavior of the monotonic
315 Base_Monotonic_Clock
:= Base_Clock
;
316 Base_Monotonic_Ticks
:= Base_Ticks
;
319 end System
.OS_Primitives
;