gcc/ada/s-osprim-mingw.adb

   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) 1998-2008, 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 2,  or (at your option) any later ver- --
  14 -- sion. GNARL 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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNARL was developed by the GNARL team at Florida State University.       --
  30 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This is the NT version of this package
  35
  36 with System.Win32.Ext;
  37
  38 package body System.OS_Primitives is
  39
  40    use System.Win32;
  41    use System.Win32.Ext;
  42
  43    ----------------------------------------
  44    -- Data for the high resolution clock --
  45    ----------------------------------------
  46
  47    --  Declare some pointers to access multi-word data above. This is needed
  48    --  to workaround a limitation in the GNU/Linker auto-import feature used
  49    --  to build the GNAT runtime DLLs. In fact the Clock and Monotonic_Clock
  50    --  routines are inlined and they are using some multi-word variables.
  51    --  GNU/Linker will fail to auto-import those variables when building
  52    --  libgnarl.dll. The indirection level introduced here has no measurable
  53    --  penalties.
  54
  55    --  Note that access variables below must not be declared as constant
  56    --  otherwise the compiler optimization will remove this indirect access.
  57
  58    type DA is access all Duration;
  59    --  Use to have indirect access to multi-word variables
  60
  61    type LIA is access all LARGE_INTEGER;
  62    --  Use to have indirect access to multi-word variables
  63
  64    type LLIA is access all Long_Long_Integer;
  65    --  Use to have indirect access to multi-word variables
  66
  67    Tick_Frequency : aliased LARGE_INTEGER;
  68    TFA : constant LIA := Tick_Frequency'Access;
  69    --  Holds frequency of high-performance counter used by Clock
  70    --  Windows NT uses a 1_193_182 Hz counter on PCs.
  71
  72    Base_Ticks : aliased LARGE_INTEGER;
  73    BTA : constant LIA := Base_Ticks'Access;
  74    --  Holds the Tick count for the base time
  75
  76    Base_Monotonic_Ticks : aliased LARGE_INTEGER;
  77    BMTA : constant LIA := Base_Monotonic_Ticks'Access;
  78    --  Holds the Tick count for the base monotonic time
  79
  80    Base_Clock : aliased Duration;
  81    BCA : constant DA := Base_Clock'Access;
  82    --  Holds the current clock for the standard clock's base time
  83
  84    Base_Monotonic_Clock : aliased Duration;
  85    BMCA : constant DA := Base_Monotonic_Clock'Access;
  86    --  Holds the current clock for monotonic clock's base time
  87
  88    Base_Time : aliased Long_Long_Integer;
  89    BTiA : constant LLIA := Base_Time'Access;
  90    --  Holds the base time used to check for system time change, used with
  91    --  the standard clock.
  92
  93    procedure Get_Base_Time;
  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       Current_Ticks        : aliased LARGE_INTEGER;
 114       Elap_Secs_Tick       : Duration;
 115       Elap_Secs_Sys        : Duration;
 116       Now                  : aliased Long_Long_Integer;
 117
 118    begin
 119       if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then
 120          return 0.0;
 121       end if;
 122
 123       GetSystemTimeAsFileTime (Now'Access);
 124
 125       Elap_Secs_Sys :=
 126         Duration (Long_Long_Float (abs (Now - BTiA.all)) /
 127                     Hundreds_Nano_In_Sec);
 128
 129       Elap_Secs_Tick :=
 130         Duration (Long_Long_Float (Current_Ticks - BTA.all) /
 131                   Long_Long_Float (TFA.all));
 132
 133       --  If we have a shift of more than Max_Shift seconds we resynchronize
 134       --  the Clock. This is probably due to a manual Clock adjustment, an
 135       --  DST adjustment or an NTP synchronisation. And we want to adjust the
 136       --  time for this system (non-monotonic) clock.
 137
 138       if abs (Elap_Secs_Sys - Elap_Secs_Tick) > Max_Shift then
 139          Get_Base_Time;
 140
 141          Elap_Secs_Tick :=
 142            Duration (Long_Long_Float (Current_Ticks - BTA.all) /
 143                      Long_Long_Float (TFA.all));
 144       end if;
 145
 146       return BCA.all + Elap_Secs_Tick;
 147    end Clock;
 148
 149    -------------------
 150    -- Get_Base_Time --
 151    -------------------
 152
 153    procedure Get_Base_Time is
 154
 155       --  The resolution for GetSystemTime is 1 millisecond
 156
 157       --  The time to get both base times should take less than 1 millisecond.
 158       --  Therefore, the elapsed time reported by GetSystemTime between both
 159       --  actions should be null.
 160
 161       Max_Elapsed : constant := 0;
 162
 163       Test_Now : aliased Long_Long_Integer;
 164
 165       epoch_1970     : constant := 16#19D_B1DE_D53E_8000#; -- win32 UTC epoch
 166       system_time_ns : constant := 100;                    -- 100 ns per tick
 167       Sec_Unit       : constant := 10#1#E9;
 168
 169    begin
 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.
 173
 174       loop
 175          GetSystemTimeAsFileTime (Base_Time'Access);
 176
 177          if QueryPerformanceCounter (Base_Ticks'Access) = Win32.FALSE then
 178             pragma Assert
 179               (Standard.False,
 180                "Could not query high performance counter in Clock");
 181             null;
 182          end if;
 183
 184          GetSystemTimeAsFileTime (Test_Now'Access);
 185
 186          exit when Test_Now - Base_Time = Max_Elapsed;
 187       end loop;
 188
 189       Base_Clock := Duration
 190         (Long_Long_Float ((Base_Time - epoch_1970) * system_time_ns) /
 191          Long_Long_Float (Sec_Unit));
 192    end Get_Base_Time;
 193
 194    ---------------------
 195    -- Monotonic_Clock --
 196    ---------------------
 197
 198    function Monotonic_Clock return Duration is
 199       Current_Ticks  : aliased LARGE_INTEGER;
 200       Elap_Secs_Tick : Duration;
 201
 202    begin
 203       if QueryPerformanceCounter (Current_Ticks'Access) = Win32.FALSE then
 204          return 0.0;
 205       end if;
 206
 207       Elap_Secs_Tick :=
 208         Duration (Long_Long_Float (Current_Ticks - BMTA.all) /
 209                   Long_Long_Float (TFA.all));
 210
 211       return BMCA.all + Elap_Secs_Tick;
 212    end Monotonic_Clock;
 213
 214    -----------------
 215    -- Timed_Delay --
 216    -----------------
 217
 218    procedure Timed_Delay (Time : Duration; Mode : Integer) is
 219
 220       function Mode_Clock return Duration;
 221       pragma Inline (Mode_Clock);
 222       --  Return the current clock value using either the monotonic clock or
 223       --  standard clock depending on the Mode value.
 224
 225       ----------------
 226       -- Mode_Clock --
 227       ----------------
 228
 229       function Mode_Clock return Duration is
 230       begin
 231          case Mode is
 232             when Absolute_RT =>
 233                return Monotonic_Clock;
 234             when others =>
 235                return Clock;
 236          end case;
 237       end Mode_Clock;
 238
 239       --  Local Variables
 240
 241       Base_Time : constant Duration := Mode_Clock;
 242       --  Base_Time is used to detect clock set backward, in this case we
 243       --  cannot ensure the delay accuracy.
 244
 245       Rel_Time   : Duration;
 246       Abs_Time   : Duration;
 247       Check_Time : Duration := Base_Time;
 248
 249    --  Start of processing for Timed Delay
 250
 251    begin
 252       if Mode = Relative then
 253          Rel_Time := Time;
 254          Abs_Time := Time + Check_Time;
 255       else
 256          Rel_Time := Time - Check_Time;
 257          Abs_Time := Time;
 258       end if;
 259
 260       if Rel_Time > 0.0 then
 261          loop
 262             Sleep (DWORD (Rel_Time * 1000.0));
 263             Check_Time := Mode_Clock;
 264
 265             exit when Abs_Time <= Check_Time or else Check_Time < Base_Time;
 266
 267             Rel_Time := Abs_Time - Check_Time;
 268          end loop;
 269       end if;
 270    end Timed_Delay;
 271
 272    ----------------
 273    -- Initialize --
 274    ----------------
 275
 276    Initialized : Boolean := False;
 277
 278    procedure Initialize is
 279    begin
 280       if Initialized then
 281          return;
 282       end if;
 283
 284       Initialized := True;
 285
 286       --  Get starting time as base
 287
 288       if QueryPerformanceFrequency (Tick_Frequency'Access) = Win32.FALSE then
 289          raise Program_Error with
 290            "cannot get high performance counter frequency";
 291       end if;
 292
 293       Get_Base_Time;
 294
 295       --  Keep base clock and ticks for the monotonic clock. These values
 296       --  should never be changed to ensure proper behavior of the monotonic
 297       --  clock.
 298
 299       Base_Monotonic_Clock := Base_Clock;
 300       Base_Monotonic_Ticks := Base_Ticks;
 301    end Initialize;
 302
 303 end System.OS_Primitives;