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) 1998-2013, 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 procedure Get_Base_Time (Data : out Clock_Data); 94 -- Retrieve the base time and base ticks. These values will be used by 95 -- clock to compute the current time by adding to it a fraction of the 96 -- performance counter. This is for the implementation of a 97 -- high-resolution clock. Note that this routine does not change the base 98 -- monotonic values used by the monotonic clock. 99 100 ----------- 101 -- Clock -- 102 ----------- 103 104 -- This implementation of clock provides high resolution timer values 105 -- using QueryPerformanceCounter. This call return a 64 bits values (based 106 -- on the 8253 16 bits counter). This counter is updated every 1/1_193_182 107 -- times per seconds. The call to QueryPerformanceCounter takes 6 108 -- microsecs to complete. 109 110 function Clock return Duration is 111 Max_Shift : constant Duration := 2.0; 112 Hundreds_Nano_In_Sec : constant Long_Long_Float := 1.0E7; 113 Data : Clock_Data; 114 Current_Ticks : aliased LARGE_INTEGER; 115 Elap_Secs_Tick : Duration; 116 Elap_Secs_Sys : Duration; 117 Now : aliased Long_Long_Integer; 118 Sig1, Sig2 : Signature_Type; 119 120 begin 121 -- Try ten times to get a coherent set of base data. For this we just 122 -- check that the signature hasn't changed during the copy of the 123 -- current data. 124 -- 125 -- This loop will always be done once if there is no interleaved call 126 -- to Get_Base_Time. 127 128 for K in 1 .. 10 loop 129 Sig1 := Signature; 130 Data := Current.all; 131 Sig2 := Signature; 132 exit when Sig1 = Sig2; 133 end loop; 134 135 if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then 136 return 0.0; 137 end if; 138 139 GetSystemTimeAsFileTime (Now'Access); 140 141 Elap_Secs_Sys := 142 Duration (Long_Long_Float (abs (Now - Data.Base_Time)) / 143 Hundreds_Nano_In_Sec); 144 145 Elap_Secs_Tick := 146 Duration (Long_Long_Float (Current_Ticks - Data.Base_Ticks) / 147 Long_Long_Float (Tick_Frequency)); 148 149 -- If we have a shift of more than Max_Shift seconds we resynchronize 150 -- the Clock. This is probably due to a manual Clock adjustment, a DST 151 -- adjustment or an NTP synchronisation. And we want to adjust the time 152 -- for this system (non-monotonic) clock. 153 154 if abs (Elap_Secs_Sys - Elap_Secs_Tick) > Max_Shift then 155 Get_Base_Time (Data); 156 157 Elap_Secs_Tick := 158 Duration (Long_Long_Float (Current_Ticks - Data.Base_Ticks) / 159 Long_Long_Float (Tick_Frequency)); 160 end if; 161 162 return Data.Base_Clock + Elap_Secs_Tick; 163 end Clock; 164 165 ------------------- 166 -- Get_Base_Time -- 167 ------------------- 168 169 procedure Get_Base_Time (Data : out Clock_Data) is 170 171 -- The resolution for GetSystemTime is 1 millisecond 172 173 -- The time to get both base times should take less than 1 millisecond. 174 -- Therefore, the elapsed time reported by GetSystemTime between both 175 -- actions should be null. 176 177 epoch_1970 : constant := 16#19D_B1DE_D53E_8000#; -- win32 UTC epoch 178 system_time_ns : constant := 100; -- 100 ns per tick 179 Sec_Unit : constant := 10#1#E9; 180 181 Max_Elapsed : constant LARGE_INTEGER := 182 LARGE_INTEGER (Tick_Frequency / 100_000); 183 -- Look for a precision of 0.01 ms 184 185 Sig : constant Signature_Type := Signature; 186 187 Loc_Ticks, Ctrl_Ticks : aliased LARGE_INTEGER; 188 Loc_Time, Ctrl_Time : aliased Long_Long_Integer; 189 Elapsed : LARGE_INTEGER; 190 Current_Max : LARGE_INTEGER := LARGE_INTEGER'Last; 191 New_Data : Clock_Data_Access; 192 193 begin 194 -- Here we must be sure that both of these calls are done in a short 195 -- amount of time. Both are base time and should in theory be taken 196 -- at the very same time. 197 198 -- The goal of the following loop is to synchronize the system time 199 -- with the Win32 performance counter by getting a base offset for both. 200 -- Using these offsets it is then possible to compute actual time using 201 -- a performance counter which has a better precision than the Win32 202 -- time API. 203 204 -- Try at most 10 times to reach the best synchronisation (below 1 205 -- millisecond) otherwise the runtime will use the best value reached 206 -- during the runs. 207 208 Lock; 209 210 -- First check that the current value has not been updated. This 211 -- could happen if another task has called Clock at the same time 212 -- and that Max_Shift has been reached too. 213 -- 214 -- But if the current value has been changed just before we entered 215 -- into the critical section, we can safely return as the current 216 -- base data (time, clock, ticks) have already been updated. 217 218 if Sig /= Signature then 219 return; 220 end if; 221 222 -- Check for the unused data buffer and set New_Data to point to it 223 224 if Current = First'Access then 225 New_Data := Second'Access; 226 else 227 New_Data := First'Access; 228 end if; 229 230 for K in 1 .. 10 loop 231 if QueryPerformanceCounter (Loc_Ticks'Access) = Win32.FALSE then 232 pragma Assert 233 (Standard.False, 234 "Could not query high performance counter in Clock"); 235 null; 236 end if; 237 238 GetSystemTimeAsFileTime (Ctrl_Time'Access); 239 240 -- Scan for clock tick, will take up to 16ms/1ms depending on PC. 241 -- This cannot be an infinite loop or the system hardware is badly 242 -- damaged. 243 244 loop 245 GetSystemTimeAsFileTime (Loc_Time'Access); 246 247 if QueryPerformanceCounter (Ctrl_Ticks'Access) = Win32.FALSE then 248 pragma Assert 249 (Standard.False, 250 "Could not query high performance counter in Clock"); 251 null; 252 end if; 253 254 exit when Loc_Time /= Ctrl_Time; 255 Loc_Ticks := Ctrl_Ticks; 256 end loop; 257 258 -- Check elapsed Performance Counter between samples 259 -- to choose the best one. 260 261 Elapsed := Ctrl_Ticks - Loc_Ticks; 262 263 if Elapsed < Current_Max then 264 New_Data.Base_Time := Loc_Time; 265 New_Data.Base_Ticks := Loc_Ticks; 266 Current_Max := Elapsed; 267 268 -- Exit the loop when we have reached the expected precision 269 270 exit when Elapsed <= Max_Elapsed; 271 end if; 272 end loop; 273 274 New_Data.Base_Clock := 275 Duration 276 (Long_Long_Float 277 ((New_Data.Base_Time - epoch_1970) * system_time_ns) / 278 Long_Long_Float (Sec_Unit)); 279 280 -- At this point all the base values have been set into the new data 281 -- record. Change the pointer (atomic operation) to these new values. 282 283 Current := New_Data; 284 Data := New_Data.all; 285 286 -- Set new signature for this data set 287 288 Signature := Signature + 1; 289 290 Unlock; 291 292 exception 293 when others => 294 Unlock; 295 raise; 296 end Get_Base_Time; 297 298 --------------------- 299 -- Monotonic_Clock -- 300 --------------------- 301 302 function Monotonic_Clock return Duration is 303 Current_Ticks : aliased LARGE_INTEGER; 304 Elap_Secs_Tick : Duration; 305 306 begin 307 if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then 308 return 0.0; 309 310 else 311 Elap_Secs_Tick := 312 Duration (Long_Long_Float (Current_Ticks - Base_Monotonic_Ticks) / 313 Long_Long_Float (Tick_Frequency)); 314 return Base_Monotonic_Clock + Elap_Secs_Tick; 315 end if; 316 end Monotonic_Clock; 317 318 ----------------- 319 -- Timed_Delay -- 320 ----------------- 321 322 procedure Timed_Delay (Time : Duration; Mode : Integer) is 323 324 function Mode_Clock return Duration; 325 pragma Inline (Mode_Clock); 326 -- Return the current clock value using either the monotonic clock or 327 -- standard clock depending on the Mode value. 328 329 ---------------- 330 -- Mode_Clock -- 331 ---------------- 332 333 function Mode_Clock return Duration is 334 begin 335 case Mode is 336 when Absolute_RT => 337 return Monotonic_Clock; 338 when others => 339 return Clock; 340 end case; 341 end Mode_Clock; 342 343 -- Local Variables 344 345 Base_Time : constant Duration := Mode_Clock; 346 -- Base_Time is used to detect clock set backward, in this case we 347 -- cannot ensure the delay accuracy. 348 349 Rel_Time : Duration; 350 Abs_Time : Duration; 351 Check_Time : Duration := Base_Time; 352 353 -- Start of processing for Timed Delay 354 355 begin 356 if Mode = Relative then 357 Rel_Time := Time; 358 Abs_Time := Time + Check_Time; 359 else 360 Rel_Time := Time - Check_Time; 361 Abs_Time := Time; 362 end if; 363 364 if Rel_Time > 0.0 then 365 loop 366 Sleep (DWORD (Rel_Time * 1000.0)); 367 Check_Time := Mode_Clock; 368 369 exit when Abs_Time <= Check_Time or else Check_Time < Base_Time; 370 371 Rel_Time := Abs_Time - Check_Time; 372 end loop; 373 end if; 374 end Timed_Delay; 375 376 ---------------- 377 -- Initialize -- 378 ---------------- 379 380 Initialized : Boolean := False; 381 382 procedure Initialize is 383 begin 384 if Initialized then 385 return; 386 end if; 387 388 Initialized := True; 389 390 -- Get starting time as base 391 392 if QueryPerformanceFrequency (Tick_Frequency'Access) = Win32.FALSE then 393 raise Program_Error with 394 "cannot get high performance counter frequency"; 395 end if; 396 397 Get_Base_Time (Current.all); 398 399 -- Keep base clock and ticks for the monotonic clock. These values 400 -- should never be changed to ensure proper behavior of the monotonic 401 -- clock. 402 403 Base_Monotonic_Clock := Current.Base_Clock; 404 Base_Monotonic_Ticks := Current.Base_Ticks; 405 end Initialize; 406 407end System.OS_Primitives; 408