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 72 -- while the other buffer is read. The point is that we do not want to 73 -- use a lock inside the Clock routine for performance reasons. We still 74 -- use a lock in the Get_Base_Time which is called very rarely. Current 75 -- is a pointer, the pragma Atomic is there to ensure that the value can 76 -- be set or read atomically. That's it, when Get_Base_Time has updated 77 -- a buffer the switch to the new value is done by changing Current 78 -- pointer. 79 80 First, Second : aliased Clock_Data; 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 Max_Elapsed : constant LARGE_INTEGER := 181 LARGE_INTEGER (Tick_Frequency / 100_000); 182 -- Look for a precision of 0.01 ms 183 Sig : constant Signature_Type := Signature; 184 185 Loc_Ticks, Ctrl_Ticks : aliased LARGE_INTEGER; 186 Loc_Time, Ctrl_Time : aliased Long_Long_Integer; 187 Elapsed : LARGE_INTEGER; 188 Current_Max : LARGE_INTEGER := LARGE_INTEGER'Last; 189 New_Data : Clock_Data_Access; 190 191 begin 192 -- Here we must be sure that both of these calls are done in a short 193 -- amount of time. Both are base time and should in theory be taken 194 -- at the very same time. 195 196 -- The goal of the following loop is to synchronize the system time 197 -- with the Win32 performance counter by getting a base offset for both. 198 -- Using these offsets it is then possible to compute actual time using 199 -- a performance counter which has a better precision than the Win32 200 -- time API. 201 202 -- Try at most 10 times to reach the best synchronisation (below 1 203 -- millisecond) otherwise the runtime will use the best value reached 204 -- during the runs. 205 206 Lock; 207 208 -- First check that the current value has not been updated. This 209 -- could happen if another task has called Clock at the same time 210 -- and that Max_Shift has been reached too. 211 -- 212 -- But if the current value has been changed just before we entered 213 -- into the critical section, we can safely return as the current 214 -- base data (time, clock, ticks) have already been updated. 215 216 if Sig /= Signature then 217 return; 218 end if; 219 220 -- Check for the unused data buffer and set New_Data to point to it 221 222 if Current = First'Access then 223 New_Data := Second'Access; 224 else 225 New_Data := First'Access; 226 end if; 227 228 for K in 1 .. 10 loop 229 if QueryPerformanceCounter (Loc_Ticks'Access) = Win32.FALSE then 230 pragma Assert 231 (Standard.False, 232 "Could not query high performance counter in Clock"); 233 null; 234 end if; 235 236 GetSystemTimeAsFileTime (Ctrl_Time'Access); 237 238 -- Scan for clock tick, will take up to 16ms/1ms depending on PC. 239 -- This cannot be an infinite loop or the system hardware is badly 240 -- damaged. 241 242 loop 243 GetSystemTimeAsFileTime (Loc_Time'Access); 244 245 if QueryPerformanceCounter (Ctrl_Ticks'Access) = Win32.FALSE then 246 pragma Assert 247 (Standard.False, 248 "Could not query high performance counter in Clock"); 249 null; 250 end if; 251 252 exit when Loc_Time /= Ctrl_Time; 253 Loc_Ticks := Ctrl_Ticks; 254 end loop; 255 256 -- Check elapsed Performance Counter between samples 257 -- to choose the best one. 258 259 Elapsed := Ctrl_Ticks - Loc_Ticks; 260 261 if Elapsed < Current_Max then 262 New_Data.Base_Time := Loc_Time; 263 New_Data.Base_Ticks := Loc_Ticks; 264 Current_Max := Elapsed; 265 266 -- Exit the loop when we have reached the expected precision 267 268 exit when Elapsed <= Max_Elapsed; 269 end if; 270 end loop; 271 272 New_Data.Base_Clock := Duration 273 (Long_Long_Float ((New_Data.Base_Time - epoch_1970) * system_time_ns) / 274 Long_Long_Float (Sec_Unit)); 275 276 -- At this point all the base values have been set into the new data 277 -- record. We just change the pointer (atomic operation) to this new 278 -- values. 279 280 Current := New_Data; 281 Data := New_Data.all; 282 283 -- Set new signature for this data set 284 285 Signature := Signature + 1; 286 287 Unlock; 288 289 exception 290 when others => 291 Unlock; 292 raise; 293 end Get_Base_Time; 294 295 --------------------- 296 -- Monotonic_Clock -- 297 --------------------- 298 299 function Monotonic_Clock return Duration is 300 Current_Ticks : aliased LARGE_INTEGER; 301 Elap_Secs_Tick : Duration; 302 303 begin 304 if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then 305 return 0.0; 306 307 else 308 Elap_Secs_Tick := 309 Duration (Long_Long_Float (Current_Ticks - Base_Monotonic_Ticks) / 310 Long_Long_Float (Tick_Frequency)); 311 return Base_Monotonic_Clock + Elap_Secs_Tick; 312 end if; 313 end Monotonic_Clock; 314 315 ----------------- 316 -- Timed_Delay -- 317 ----------------- 318 319 procedure Timed_Delay (Time : Duration; Mode : Integer) is 320 321 function Mode_Clock return Duration; 322 pragma Inline (Mode_Clock); 323 -- Return the current clock value using either the monotonic clock or 324 -- standard clock depending on the Mode value. 325 326 ---------------- 327 -- Mode_Clock -- 328 ---------------- 329 330 function Mode_Clock return Duration is 331 begin 332 case Mode is 333 when Absolute_RT => 334 return Monotonic_Clock; 335 when others => 336 return Clock; 337 end case; 338 end Mode_Clock; 339 340 -- Local Variables 341 342 Base_Time : constant Duration := Mode_Clock; 343 -- Base_Time is used to detect clock set backward, in this case we 344 -- cannot ensure the delay accuracy. 345 346 Rel_Time : Duration; 347 Abs_Time : Duration; 348 Check_Time : Duration := Base_Time; 349 350 -- Start of processing for Timed Delay 351 352 begin 353 if Mode = Relative then 354 Rel_Time := Time; 355 Abs_Time := Time + Check_Time; 356 else 357 Rel_Time := Time - Check_Time; 358 Abs_Time := Time; 359 end if; 360 361 if Rel_Time > 0.0 then 362 loop 363 Sleep (DWORD (Rel_Time * 1000.0)); 364 Check_Time := Mode_Clock; 365 366 exit when Abs_Time <= Check_Time or else Check_Time < Base_Time; 367 368 Rel_Time := Abs_Time - Check_Time; 369 end loop; 370 end if; 371 end Timed_Delay; 372 373 ---------------- 374 -- Initialize -- 375 ---------------- 376 377 Initialized : Boolean := False; 378 379 procedure Initialize is 380 begin 381 if Initialized then 382 return; 383 end if; 384 385 Initialized := True; 386 387 -- Get starting time as base 388 389 if QueryPerformanceFrequency (Tick_Frequency'Access) = Win32.FALSE then 390 raise Program_Error with 391 "cannot get high performance counter frequency"; 392 end if; 393 394 Get_Base_Time (Current.all); 395 396 -- Keep base clock and ticks for the monotonic clock. These values 397 -- should never be changed to ensure proper behavior of the monotonic 398 -- clock. 399 400 Base_Monotonic_Clock := Current.Base_Clock; 401 Base_Monotonic_Ticks := Current.Base_Ticks; 402 end Initialize; 403 404end System.OS_Primitives; 405