1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- 4-- -- 5-- S Y S T E M . O S _ P R I M I T I V E S -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 1998-2015, Free Software Foundation, Inc. -- 10-- -- 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. -- 17-- -- 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. -- 21-- -- 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/>. -- 26-- -- 27-- GNARL was developed by the GNARL team at Florida State University. -- 28-- Extensive contributions were provided by Ada Core Technologies, Inc. -- 29-- -- 30------------------------------------------------------------------------------ 31 32-- This is the NT version of this package 33 34with System.Task_Lock; 35with System.Win32.Ext; 36 37package body System.OS_Primitives is 38 39 use System.Task_Lock; 40 use System.Win32; 41 use System.Win32.Ext; 42 43 ---------------------------------------- 44 -- Data for the high resolution clock -- 45 ---------------------------------------- 46 47 Tick_Frequency : aliased LARGE_INTEGER; 48 -- Holds frequency of high-performance counter used by Clock 49 -- Windows NT uses a 1_193_182 Hz counter on PCs. 50 51 Base_Monotonic_Ticks : LARGE_INTEGER; 52 -- Holds the Tick count for the base monotonic time 53 54 Base_Monotonic_Clock : Duration; 55 -- Holds the current clock for monotonic clock's base time 56 57 type Clock_Data is record 58 Base_Ticks : LARGE_INTEGER; 59 -- Holds the Tick count for the base time 60 61 Base_Time : Long_Long_Integer; 62 -- Holds the base time used to check for system time change, used with 63 -- the standard clock. 64 65 Base_Clock : Duration; 66 -- Holds the current clock for the standard clock's base time 67 end record; 68 69 type Clock_Data_Access is access all Clock_Data; 70 71 -- Two base clock buffers. This is used to be able to update a buffer while 72 -- the other buffer is read. The point is that we do not want to use a lock 73 -- inside the Clock routine for performance reasons. We still use a lock 74 -- in the Get_Base_Time which is called very rarely. Current is a pointer, 75 -- the pragma Atomic is there to ensure that the value can be set or read 76 -- atomically. That's it, when Get_Base_Time has updated a buffer the 77 -- switch to the new value is done by changing Current pointer. 78 79 First, Second : aliased Clock_Data; 80 81 Current : Clock_Data_Access := First'Access; 82 pragma Atomic (Current); 83 84 -- The following signature is to detect change on the base clock data 85 -- above. The signature is a modular type, it will wrap around without 86 -- raising an exception. We would need to have exactly 2**32 updates of 87 -- the base data for the changes to get undetected. 88 89 type Signature_Type is mod 2**32; 90 Signature : Signature_Type := 0; 91 pragma Atomic (Signature); 92 93 function Monotonic_Clock return Duration; 94 pragma Export (Ada, Monotonic_Clock, "__gnat_monotonic_clock"); 95 -- Return "absolute" time, represented as an offset relative to "the Unix 96 -- Epoch", which is Jan 1, 1970 00:00:00 UTC. This clock implementation is 97 -- immune to the system's clock changes. Export this function so that it 98 -- can be imported from s-taprop-mingw.adb without changing the shared 99 -- spec (s-osprim.ads). 100 101 procedure Get_Base_Time (Data : in out Clock_Data); 102 -- Retrieve the base time and base ticks. These values will be used by 103 -- clock to compute the current time by adding to it a fraction of the 104 -- performance counter. This is for the implementation of a high-resolution 105 -- clock. Note that this routine does not change the base monotonic values 106 -- used by the monotonic clock. 107 108 ----------- 109 -- Clock -- 110 ----------- 111 112 -- This implementation of clock provides high resolution timer values 113 -- using QueryPerformanceCounter. This call return a 64 bits values (based 114 -- on the 8253 16 bits counter). This counter is updated every 1/1_193_182 115 -- times per seconds. The call to QueryPerformanceCounter takes 6 116 -- microsecs to complete. 117 118 function Clock return Duration is 119 Max_Shift : constant Duration := 2.0; 120 Hundreds_Nano_In_Sec : constant Long_Long_Float := 1.0E7; 121 Data : Clock_Data; 122 Current_Ticks : aliased LARGE_INTEGER; 123 Elap_Secs_Tick : Duration; 124 Elap_Secs_Sys : Duration; 125 Now : aliased Long_Long_Integer; 126 Sig1, Sig2 : Signature_Type; 127 128 begin 129 -- Try ten times to get a coherent set of base data. For this we just 130 -- check that the signature hasn't changed during the copy of the 131 -- current data. 132 -- 133 -- This loop will always be done once if there is no interleaved call 134 -- to Get_Base_Time. 135 136 for K in 1 .. 10 loop 137 Sig1 := Signature; 138 Data := Current.all; 139 Sig2 := Signature; 140 exit when Sig1 = Sig2; 141 end loop; 142 143 if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then 144 return 0.0; 145 end if; 146 147 GetSystemTimeAsFileTime (Now'Access); 148 149 Elap_Secs_Sys := 150 Duration (Long_Long_Float (abs (Now - Data.Base_Time)) / 151 Hundreds_Nano_In_Sec); 152 153 Elap_Secs_Tick := 154 Duration (Long_Long_Float (Current_Ticks - Data.Base_Ticks) / 155 Long_Long_Float (Tick_Frequency)); 156 157 -- If we have a shift of more than Max_Shift seconds we resynchronize 158 -- the Clock. This is probably due to a manual Clock adjustment, a DST 159 -- adjustment or an NTP synchronisation. And we want to adjust the time 160 -- for this system (non-monotonic) clock. 161 162 if abs (Elap_Secs_Sys - Elap_Secs_Tick) > Max_Shift then 163 Get_Base_Time (Data); 164 165 Elap_Secs_Tick := 166 Duration (Long_Long_Float (Current_Ticks - Data.Base_Ticks) / 167 Long_Long_Float (Tick_Frequency)); 168 end if; 169 170 return Data.Base_Clock + Elap_Secs_Tick; 171 end Clock; 172 173 ------------------- 174 -- Get_Base_Time -- 175 ------------------- 176 177 procedure Get_Base_Time (Data : in out Clock_Data) is 178 179 -- The resolution for GetSystemTime is 1 millisecond 180 181 -- The time to get both base times should take less than 1 millisecond. 182 -- Therefore, the elapsed time reported by GetSystemTime between both 183 -- actions should be null. 184 185 epoch_1970 : constant := 16#19D_B1DE_D53E_8000#; -- win32 UTC epoch 186 system_time_ns : constant := 100; -- 100 ns per tick 187 Sec_Unit : constant := 10#1#E9; 188 189 Max_Elapsed : constant LARGE_INTEGER := 190 LARGE_INTEGER (Tick_Frequency / 100_000); 191 -- Look for a precision of 0.01 ms 192 193 Sig : constant Signature_Type := Signature; 194 195 Loc_Ticks, Ctrl_Ticks : aliased LARGE_INTEGER; 196 Loc_Time, Ctrl_Time : aliased Long_Long_Integer; 197 Elapsed : LARGE_INTEGER; 198 Current_Max : LARGE_INTEGER := LARGE_INTEGER'Last; 199 New_Data : Clock_Data_Access; 200 201 begin 202 -- Here we must be sure that both of these calls are done in a short 203 -- amount of time. Both are base time and should in theory be taken 204 -- at the very same time. 205 206 -- The goal of the following loop is to synchronize the system time 207 -- with the Win32 performance counter by getting a base offset for both. 208 -- Using these offsets it is then possible to compute actual time using 209 -- a performance counter which has a better precision than the Win32 210 -- time API. 211 212 -- Try at most 10 times to reach the best synchronisation (below 1 213 -- millisecond) otherwise the runtime will use the best value reached 214 -- during the runs. 215 216 Lock; 217 218 -- First check that the current value has not been updated. This 219 -- could happen if another task has called Clock at the same time 220 -- and that Max_Shift has been reached too. 221 -- 222 -- But if the current value has been changed just before we entered 223 -- into the critical section, we can safely return as the current 224 -- base data (time, clock, ticks) have already been updated. 225 226 if Sig /= Signature then 227 Unlock; 228 return; 229 end if; 230 231 -- Check for the unused data buffer and set New_Data to point to it 232 233 if Current = First'Access then 234 New_Data := Second'Access; 235 else 236 New_Data := First'Access; 237 end if; 238 239 for K in 1 .. 10 loop 240 if QueryPerformanceCounter (Loc_Ticks'Access) = Win32.FALSE then 241 pragma Assert 242 (Standard.False, 243 "Could not query high performance counter in Clock"); 244 null; 245 end if; 246 247 GetSystemTimeAsFileTime (Ctrl_Time'Access); 248 249 -- Scan for clock tick, will take up to 16ms/1ms depending on PC. 250 -- This cannot be an infinite loop or the system hardware is badly 251 -- damaged. 252 253 loop 254 GetSystemTimeAsFileTime (Loc_Time'Access); 255 256 if QueryPerformanceCounter (Ctrl_Ticks'Access) = Win32.FALSE then 257 pragma Assert 258 (Standard.False, 259 "Could not query high performance counter in Clock"); 260 null; 261 end if; 262 263 exit when Loc_Time /= Ctrl_Time; 264 Loc_Ticks := Ctrl_Ticks; 265 end loop; 266 267 -- Check elapsed Performance Counter between samples 268 -- to choose the best one. 269 270 Elapsed := Ctrl_Ticks - Loc_Ticks; 271 272 if Elapsed < Current_Max then 273 New_Data.Base_Time := Loc_Time; 274 New_Data.Base_Ticks := Loc_Ticks; 275 Current_Max := Elapsed; 276 277 -- Exit the loop when we have reached the expected precision 278 279 exit when Elapsed <= Max_Elapsed; 280 end if; 281 end loop; 282 283 New_Data.Base_Clock := 284 Duration 285 (Long_Long_Float 286 ((New_Data.Base_Time - epoch_1970) * system_time_ns) / 287 Long_Long_Float (Sec_Unit)); 288 289 -- At this point all the base values have been set into the new data 290 -- record. Change the pointer (atomic operation) to these new values. 291 292 Current := New_Data; 293 Data := New_Data.all; 294 295 -- Set new signature for this data set 296 297 Signature := Signature + 1; 298 299 Unlock; 300 301 exception 302 when others => 303 Unlock; 304 raise; 305 end Get_Base_Time; 306 307 --------------------- 308 -- Monotonic_Clock -- 309 --------------------- 310 311 function Monotonic_Clock return Duration is 312 Current_Ticks : aliased LARGE_INTEGER; 313 Elap_Secs_Tick : Duration; 314 315 begin 316 if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then 317 return 0.0; 318 319 else 320 Elap_Secs_Tick := 321 Duration (Long_Long_Float (Current_Ticks - Base_Monotonic_Ticks) / 322 Long_Long_Float (Tick_Frequency)); 323 return Base_Monotonic_Clock + Elap_Secs_Tick; 324 end if; 325 end Monotonic_Clock; 326 327 ----------------- 328 -- Timed_Delay -- 329 ----------------- 330 331 procedure Timed_Delay (Time : Duration; Mode : Integer) is 332 333 function Mode_Clock return Duration; 334 pragma Inline (Mode_Clock); 335 -- Return the current clock value using either the monotonic clock or 336 -- standard clock depending on the Mode value. 337 338 ---------------- 339 -- Mode_Clock -- 340 ---------------- 341 342 function Mode_Clock return Duration is 343 begin 344 case Mode is 345 when Absolute_RT => 346 return Monotonic_Clock; 347 when others => 348 return Clock; 349 end case; 350 end Mode_Clock; 351 352 -- Local Variables 353 354 Base_Time : constant Duration := Mode_Clock; 355 -- Base_Time is used to detect clock set backward, in this case we 356 -- cannot ensure the delay accuracy. 357 358 Rel_Time : Duration; 359 Abs_Time : Duration; 360 Check_Time : Duration := Base_Time; 361 362 -- Start of processing for Timed Delay 363 364 begin 365 if Mode = Relative then 366 Rel_Time := Time; 367 Abs_Time := Time + Check_Time; 368 else 369 Rel_Time := Time - Check_Time; 370 Abs_Time := Time; 371 end if; 372 373 if Rel_Time > 0.0 then 374 loop 375 Sleep (DWORD (Rel_Time * 1000.0)); 376 Check_Time := Mode_Clock; 377 378 exit when Abs_Time <= Check_Time or else Check_Time < Base_Time; 379 380 Rel_Time := Abs_Time - Check_Time; 381 end loop; 382 end if; 383 end Timed_Delay; 384 385 ---------------- 386 -- Initialize -- 387 ---------------- 388 389 Initialized : Boolean := False; 390 391 procedure Initialize is 392 begin 393 if Initialized then 394 return; 395 end if; 396 397 Initialized := True; 398 399 -- Get starting time as base 400 401 if QueryPerformanceFrequency (Tick_Frequency'Access) = Win32.FALSE then 402 raise Program_Error with 403 "cannot get high performance counter frequency"; 404 end if; 405 406 Get_Base_Time (Current.all); 407 408 -- Keep base clock and ticks for the monotonic clock. These values 409 -- should never be changed to ensure proper behavior of the monotonic 410 -- clock. 411 412 Base_Monotonic_Clock := Current.Base_Clock; 413 Base_Monotonic_Ticks := Current.Base_Ticks; 414 end Initialize; 415 416end System.OS_Primitives; 417