gcc/ada/5wosprim.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNU ADA 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) 1998-2003 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,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, 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 Ada.Exceptions;
  37 with Interfaces.C;
  38
  39 package body System.OS_Primitives is
  40
  41    ---------------------------
  42    -- Win32 API Definitions --
  43    ---------------------------
  44
  45    --  These definitions are copied from System.OS_Interface because we do not
  46    --  want to depend on gnarl here.
  47
  48    type DWORD is new Interfaces.C.unsigned_long;
  49
  50    type LARGE_INTEGER is delta 1.0 range -2.0**63 .. 2.0**63 - 1.0;
  51
  52    type BOOL is new Boolean;
  53    for BOOL'Size use Interfaces.C.unsigned_long'Size;
  54
  55    procedure GetSystemTimeAsFileTime (lpFileTime : access Long_Long_Integer);
  56    pragma Import (Stdcall, GetSystemTimeAsFileTime, "GetSystemTimeAsFileTime");
  57
  58    function QueryPerformanceCounter
  59      (lpPerformanceCount : access LARGE_INTEGER) return BOOL;
  60    pragma Import
  61      (Stdcall, QueryPerformanceCounter, "QueryPerformanceCounter");
  62
  63    function QueryPerformanceFrequency
  64      (lpFrequency : access LARGE_INTEGER) return BOOL;
  65    pragma Import
  66      (Stdcall, QueryPerformanceFrequency, "QueryPerformanceFrequency");
  67
  68    procedure Sleep (dwMilliseconds : DWORD);
  69    pragma Import (Stdcall, Sleep, External_Name => "Sleep");
  70
  71    ----------------------------------------
  72    -- Data for the high resolution clock --
  73    ----------------------------------------
  74
  75    --  Declare some pointers to access multi-word data above. This is needed
  76    --  to workaround a limitation in the GNU/Linker auto-import feature used
  77    --  to build the GNAT runtime DLLs. In fact the Clock and Monotonic_Clock
  78    --  routines are inlined and they are using some multi-word variables.
  79    --  GNU/Linker will fail to auto-import those variables when building
  80    --  libgnarl.dll. The indirection level introduced here has no measurable
  81    --  penalties.
  82    --
  83    --  Note that access variables below must not be declared as constant
  84    --  otherwise the compiler optimization will remove this indirect access.
  85
  86    type DA is access all Duration;
  87    --  Use to have indirect access to multi-word variables
  88
  89    type LIA is access all LARGE_INTEGER;
  90    --  Use to have indirect access to multi-word variables
  91
  92    type LLIA is access all Long_Long_Integer;
  93    --  Use to have indirect access to multi-word variables
  94
  95    Tick_Frequency : aliased LARGE_INTEGER;
  96    TFA : constant LIA := Tick_Frequency'Access;
  97    --  Holds frequency of high-performance counter used by Clock
  98    --  Windows NT uses a 1_193_182 Hz counter on PCs.
  99
 100    Base_Ticks : aliased LARGE_INTEGER;
 101    BTA : constant LIA := Base_Ticks'Access;
 102    --  Holds the Tick count for the base time.
 103
 104    Base_Monotonic_Ticks : aliased LARGE_INTEGER;
 105    BMTA : constant LIA := Base_Monotonic_Ticks'Access;
 106    --  Holds the Tick count for the base monotonic time
 107
 108    Base_Clock : aliased Duration;
 109    BCA : constant DA := Base_Clock'Access;
 110    --  Holds the current clock for the standard clock's base time
 111
 112    Base_Monotonic_Clock : aliased Duration;
 113    BMCA : constant DA := Base_Monotonic_Clock'Access;
 114    --  Holds the current clock for monotonic clock's base time
 115
 116    Base_Time : aliased Long_Long_Integer;
 117    BTiA : constant LLIA := Base_Time'Access;
 118    --  Holds the base time used to check for system time change, used with
 119    --  the standard clock.
 120
 121    procedure Get_Base_Time;
 122    --  Retrieve the base time and base ticks. These values will be used by
 123    --  clock to compute the current time by adding to it a fraction of the
 124    --  performance counter. This is for the implementation of a
 125    --  high-resolution clock. Note that this routine does not change the base
 126    --  monotonic values used by the monotonic clock.
 127
 128    -----------
 129    -- Clock --
 130    -----------
 131
 132    --  This implementation of clock provides high resolution timer values
 133    --  using QueryPerformanceCounter. This call return a 64 bits values (based
 134    --  on the 8253 16 bits counter). This counter is updated every 1/1_193_182
 135    --  times per seconds. The call to QueryPerformanceCounter takes 6
 136    --  microsecs to complete.
 137
 138    function Clock return Duration is
 139       Max_Shift            : constant Duration        := 2.0;
 140       Hundreds_Nano_In_Sec : constant Long_Long_Float := 1.0E7;
 141       Current_Ticks        : aliased LARGE_INTEGER;
 142       Elap_Secs_Tick       : Duration;
 143       Elap_Secs_Sys        : Duration;
 144       Now                  : aliased Long_Long_Integer;
 145
 146    begin
 147       if not QueryPerformanceCounter (Current_Ticks'Access) then
 148          return 0.0;
 149       end if;
 150
 151       GetSystemTimeAsFileTime (Now'Access);
 152
 153       Elap_Secs_Sys :=
 154         Duration (Long_Long_Float (abs (Now - BTiA.all)) /
 155                     Hundreds_Nano_In_Sec);
 156
 157       Elap_Secs_Tick :=
 158         Duration (Long_Long_Float (Current_Ticks - BTA.all) /
 159                   Long_Long_Float (TFA.all));
 160
 161       --  If we have a shift of more than Max_Shift seconds we resynchonize the
 162       --  Clock. This is probably due to a manual Clock adjustment, an DST
 163       --  adjustment or an NTP synchronisation. And we want to adjust the
 164       --  time for this system (non-monotonic) clock.
 165
 166       if abs (Elap_Secs_Sys - Elap_Secs_Tick) > Max_Shift then
 167          Get_Base_Time;
 168
 169          Elap_Secs_Tick :=
 170            Duration (Long_Long_Float (Current_Ticks - BTA.all) /
 171                      Long_Long_Float (TFA.all));
 172       end if;
 173
 174       return BCA.all + Elap_Secs_Tick;
 175    end Clock;
 176
 177    -------------------
 178    -- Get_Base_Time --
 179    -------------------
 180
 181    procedure Get_Base_Time is
 182       --  The resolution for GetSystemTime is 1 millisecond.
 183
 184       --  The time to get both base times should take less than 1 millisecond.
 185       --  Therefore, the elapsed time reported by GetSystemTime between both
 186       --  actions should be null.
 187
 188       Max_Elapsed    : constant := 0;
 189
 190       Test_Now       : aliased Long_Long_Integer;
 191
 192       epoch_1970     : constant := 16#19D_B1DE_D53E_8000#; -- win32 UTC epoch
 193       system_time_ns : constant := 100;                    -- 100 ns per tick
 194       Sec_Unit       : constant := 10#1#E9;
 195
 196    begin
 197       --  Here we must be sure that both of these calls are done in a short
 198       --  amount of time. Both are base time and should in theory be taken
 199       --  at the very same time.
 200
 201       loop
 202          GetSystemTimeAsFileTime (Base_Time'Access);
 203
 204          if not QueryPerformanceCounter (Base_Ticks'Access) then
 205             pragma Assert
 206               (Standard.False,
 207                "Could not query high performance counter in Clock");
 208             null;
 209          end if;
 210
 211          GetSystemTimeAsFileTime (Test_Now'Access);
 212
 213          exit when Test_Now - Base_Time = Max_Elapsed;
 214       end loop;
 215
 216       Base_Clock := Duration
 217         (Long_Long_Float ((Base_Time - epoch_1970) * system_time_ns) /
 218          Long_Long_Float (Sec_Unit));
 219    end Get_Base_Time;
 220
 221    ---------------------
 222    -- Monotonic_Clock --
 223    ---------------------
 224
 225    function Monotonic_Clock return Duration is
 226       Current_Ticks  : aliased LARGE_INTEGER;
 227       Elap_Secs_Tick : Duration;
 228    begin
 229       if not QueryPerformanceCounter (Current_Ticks'Access) then
 230          return 0.0;
 231       end if;
 232
 233       Elap_Secs_Tick :=
 234         Duration (Long_Long_Float (Current_Ticks - BMTA.all) /
 235                   Long_Long_Float (TFA.all));
 236
 237       return BMCA.all + Elap_Secs_Tick;
 238    end Monotonic_Clock;
 239
 240    -----------------
 241    -- Timed_Delay --
 242    -----------------
 243
 244    procedure Timed_Delay (Time : Duration; Mode : Integer) is
 245       Rel_Time   : Duration;
 246       Abs_Time   : Duration;
 247       Check_Time : Duration := Monotonic_Clock;
 248
 249    begin
 250       if Mode = Relative then
 251          Rel_Time := Time;
 252          Abs_Time := Time + Check_Time;
 253       else
 254          Rel_Time := Time - Check_Time;
 255          Abs_Time := Time;
 256       end if;
 257
 258       if Rel_Time > 0.0 then
 259          loop
 260             Sleep (DWORD (Rel_Time * 1000.0));
 261             Check_Time := Monotonic_Clock;
 262
 263             exit when Abs_Time <= Check_Time;
 264
 265             Rel_Time := Abs_Time - Check_Time;
 266          end loop;
 267       end if;
 268    end Timed_Delay;
 269
 270 --  Package elaboration, get starting time as base
 271
 272 begin
 273    if not QueryPerformanceFrequency (Tick_Frequency'Access) then
 274       Ada.Exceptions.Raise_Exception
 275         (Program_Error'Identity,
 276          "cannot get high performance counter frequency");
 277    end if;
 278
 279    Get_Base_Time;
 280
 281    --  Keep base clock and ticks for the monotonic clock. These values should
 282    --  never be changed to ensure proper behavior of the monotonic clock.
 283
 284    Base_Monotonic_Clock := Base_Clock;
 285    Base_Monotonic_Ticks := Base_Ticks;
 286 end System.OS_Primitives;