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 --                             $Revision: 1.1.16.1 $
  10 --                                                                          --
  11 --          Copyright (C) 1998-2001 Free Software Foundation, Inc.          --
  12 --                                                                          --
  13 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  14 -- terms of the  GNU General Public License as published  by the Free Soft- --
  15 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  16 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  17 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  18 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  19 -- for  more details.  You should have  received  a copy of the GNU General --
  20 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  21 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  22 -- MA 02111-1307, USA.                                                      --
  23 --                                                                          --
  24 -- As a special exception,  if other files  instantiate  generics from this --
  25 -- unit, or you link  this unit with other files  to produce an executable, --
  26 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  27 -- covered  by the  GNU  General  Public  License.  This exception does not --
  28 -- however invalidate  any other reasons why  the executable file  might be --
  29 -- covered by the  GNU Public License.                                      --
  30 --                                                                          --
  31 -- GNARL was developed by the GNARL team at Florida State University.       --
  32 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  33 --                                                                          --
  34 ------------------------------------------------------------------------------
  35
  36 --  This is the NT version of this package
  37
  38 with Ada.Exceptions;
  39 with System.OS_Interface;
  40
  41 package body System.OS_Primitives is
  42
  43    use System.OS_Interface;
  44
  45    ---------------------------------------
  46    -- Data for the high resolution clock --
  47    ---------------------------------------
  48
  49    Tick_Frequency       : aliased LARGE_INTEGER;
  50    --  Holds frequency of high-performance counter used by Clock
  51    --  Windows NT uses a 1_193_182 Hz counter on PCs.
  52
  53    Base_Ticks           : aliased LARGE_INTEGER;
  54    --  Holds the Tick count for the base time.
  55
  56    Base_Clock           : Duration;
  57    --  Holds the current clock for the standard clock's base time
  58
  59    Base_Monotonic_Clock : Duration;
  60    --  Holds the current clock for monotonic clock's base time
  61
  62    Base_Time            : aliased Long_Long_Integer;
  63    --  Holds the base time used to check for system time change, used with
  64    --  the standard clock.
  65
  66    procedure Get_Base_Time;
  67    --  Retrieve the base time. This base time will be used by clock to
  68    --  compute the current time by adding to it a fraction of the
  69    --  performance counter. This is for the implementation of a
  70    --  high-resolution clock.
  71
  72    -----------
  73    -- Clock --
  74    -----------
  75
  76    --  This implementation of clock provides high resolution timer values
  77    --  using QueryPerformanceCounter. This call return a 64 bits values (based
  78    --  on the 8253 16 bits counter). This counter is updated every 1/1_193_182
  79    --  times per seconds. The call to QueryPerformanceCounter takes 6
  80    --  microsecs to complete.
  81
  82    function Clock return Duration is
  83       Max_Shift            : constant Duration := 2.0;
  84       Hundreds_Nano_In_Sec : constant := 1E7;
  85       Current_Ticks        : aliased LARGE_INTEGER;
  86       Elap_Secs_Tick       : Duration;
  87       Elap_Secs_Sys        : Duration;
  88       Now                  : aliased Long_Long_Integer;
  89
  90    begin
  91       if not QueryPerformanceCounter (Current_Ticks'Access) then
  92          return 0.0;
  93       end if;
  94
  95       GetSystemTimeAsFileTime (Now'Access);
  96
  97       Elap_Secs_Sys :=
  98         Duration (abs (Now - Base_Time) / Hundreds_Nano_In_Sec);
  99
 100       Elap_Secs_Tick :=
 101         Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
 102                   Long_Long_Float (Tick_Frequency));
 103
 104       --  If we have a shift of more than Max_Shift seconds we resynchonize the
 105       --  Clock. This is probably due to a manual Clock adjustment, an DST
 106       --  adjustment or an NNTP synchronisation. And we want to adjust the
 107       --  time for this system (non-monotonic) clock.
 108
 109       if abs (Elap_Secs_Sys - Elap_Secs_Tick) > Max_Shift then
 110          Get_Base_Time;
 111
 112          Elap_Secs_Tick :=
 113            Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
 114                      Long_Long_Float (Tick_Frequency));
 115       end if;
 116
 117       return Base_Clock + Elap_Secs_Tick;
 118    end Clock;
 119
 120    -------------------
 121    -- Get_Base_Time --
 122    -------------------
 123
 124    procedure Get_Base_Time is
 125       use System.OS_Interface;
 126
 127       --  The resolution for GetSystemTime is 1 millisecond.
 128
 129       --  The time to get both base times should take less than 1 millisecond.
 130       --  Therefore, the elapsed time reported by GetSystemTime between both
 131       --  actions should be null.
 132
 133       Max_Elapsed    : constant := 0;
 134
 135       Test_Now       : aliased Long_Long_Integer;
 136
 137       epoch_1970     : constant := 16#19D_B1DE_D53E_8000#; -- win32 UTC epoch
 138       system_time_ns : constant := 100;                    -- 100 ns per tick
 139       Sec_Unit       : constant := 10#1#E9;
 140
 141    begin
 142       --  Here we must be sure that both of these calls are done in a short
 143       --  amount of time. Both are base time and should in theory be taken
 144       --  at the very same time.
 145
 146       loop
 147          GetSystemTimeAsFileTime (Base_Time'Access);
 148
 149          if not QueryPerformanceCounter (Base_Ticks'Access) then
 150             pragma Assert
 151               (Standard.False,
 152                "Could not query high performance counter in Clock");
 153             null;
 154          end if;
 155
 156          GetSystemTimeAsFileTime (Test_Now'Access);
 157
 158          exit when Test_Now - Base_Time = Max_Elapsed;
 159       end loop;
 160
 161       Base_Clock := Duration
 162         (Long_Long_Float ((Base_Time - epoch_1970) * system_time_ns) /
 163          Long_Long_Float (Sec_Unit));
 164    end Get_Base_Time;
 165
 166    ---------------------
 167    -- Monotonic_Clock --
 168    ---------------------
 169
 170    function Monotonic_Clock return Duration is
 171       Current_Ticks  : aliased LARGE_INTEGER;
 172       Elap_Secs_Tick : Duration;
 173    begin
 174       if not QueryPerformanceCounter (Current_Ticks'Access) then
 175          return 0.0;
 176       end if;
 177
 178       Elap_Secs_Tick :=
 179         Duration (Long_Long_Float (Current_Ticks - Base_Ticks) /
 180                   Long_Long_Float (Tick_Frequency));
 181
 182       return Base_Monotonic_Clock + Elap_Secs_Tick;
 183    end Monotonic_Clock;
 184
 185    -----------------
 186    -- Timed_Delay --
 187    -----------------
 188
 189    procedure Timed_Delay (Time : Duration; Mode : Integer) is
 190       Rel_Time   : Duration;
 191       Abs_Time   : Duration;
 192       Check_Time : Duration := Monotonic_Clock;
 193
 194    begin
 195       if Mode = Relative then
 196          Rel_Time := Time;
 197          Abs_Time := Time + Check_Time;
 198       else
 199          Rel_Time := Time - Check_Time;
 200          Abs_Time := Time;
 201       end if;
 202
 203       if Rel_Time > 0.0 then
 204          loop
 205             Sleep (DWORD (Rel_Time * 1000.0));
 206             Check_Time := Monotonic_Clock;
 207
 208             exit when Abs_Time <= Check_Time;
 209
 210             Rel_Time := Abs_Time - Check_Time;
 211          end loop;
 212       end if;
 213    end Timed_Delay;
 214
 215 --  Package elaboration, get starting time as base
 216
 217 begin
 218    if not QueryPerformanceFrequency (Tick_Frequency'Access) then
 219       Ada.Exceptions.Raise_Exception
 220         (Program_Error'Identity,
 221          "cannot get high performance counter frequency");
 222    end if;
 223
 224    Get_Base_Time;
 225
 226    Base_Monotonic_Clock := Base_Clock;
 227 end System.OS_Primitives;