gcc/ada/s-taprob.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS               --
   4 --                                                                          --
   5 --      S Y S T E M . T A S K I N G . P R O T E C T E D _ O B J E C T S     --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --                                                                          --
  10 --          Copyright (C) 1992-2001, Free Software Foundation, Inc.         --
  11 --                                                                          --
  12 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  20 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNARL was developed by the GNARL team at Florida State University. It is --
  31 -- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
  32 -- State University (http://www.gnat.com).                                  --
  33 --                                                                          --
  34 ------------------------------------------------------------------------------
  35
  36 --  This package provides necessary definitions to handle simple (i.e without
  37 --  entries) protected objects.
  38 --
  39 --  All the routines that handle protected objects with entries have been moved
  40 --  to two children: Entries and Operations. Note that Entries only contains
  41 --  the type declaration and the OO primitives. This is needed to avoid
  42 --  circular dependency.
  43
  44 --  This package is part of the high level tasking interface used by the
  45 --  compiler to expand Ada 95 tasking constructs into simpler run time calls
  46 --  (aka GNARLI, GNU Ada Run-time Library Interface)
  47
  48 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  49 --  Any changes to this interface may require corresponding compiler changes
  50 --  in exp_ch9.adb and possibly exp_ch7.adb
  51
  52 package System.Tasking.Protected_Objects is
  53    pragma Elaborate_Body;
  54
  55    ---------------------------------
  56    -- Compiler Interface (GNARLI) --
  57    ---------------------------------
  58
  59    --  The compiler will expand in the GNAT tree the following construct:
  60    --
  61    --  protected PO is
  62    --     procedure P;
  63    --  private
  64    --     open : boolean := false;
  65    --  end PO;
  66    --
  67    --  protected body PO is
  68    --     procedure P is
  69    --        ...variable declarations...
  70    --     begin
  71    --        ...B...
  72    --     end P;
  73    --  end PO;
  74    --
  75    --  as follows:
  76    --
  77    --  protected type poT is
  78    --     procedure p;
  79    --  private
  80    --     open : boolean := false;
  81    --  end poT;
  82    --  type poTV is limited record
  83    --     open : boolean := false;
  84    --     _object : aliased protection;
  85    --  end record;
  86    --  procedure poPT__pN (_object : in out poTV);
  87    --  procedure poPT__pP (_object : in out poTV);
  88    --  freeze poTV [
  89    --     procedure _init_proc (_init : in out poTV) is
  90    --     begin
  91    --        _init.open := false;
  92    --        _init_proc (_init._object);
  93    --        initialize_protection (_init._object'unchecked_access,
  94    --          unspecified_priority);
  95    --        return;
  96    --     end _init_proc;
  97    --  ]
  98    --  po : poT;
  99    --  _init_proc (poTV!(po));
 100    --
 101    --  procedure poPT__pN (_object : in out poTV) is
 102    --     poR : protection renames _object._object;
 103    --     openP : boolean renames _object.open;
 104    --     ...variable declarations...
 105    --  begin
 106    --     ...B...
 107    --     return;
 108    --  end poPT__pN;
 109    --
 110    --  procedure poPT__pP (_object : in out poTV) is
 111    --     procedure _clean is
 112    --     begin
 113    --        unlock (_object._object'unchecked_access);
 114    --        return;
 115    --     end _clean;
 116    --  begin
 117    --     lock (_object._object'unchecked_access);
 118    --     B2b : begin
 119    --        poPT__pN (_object);
 120    --     at end
 121    --        _clean;
 122    --     end B2b;
 123    --     return;
 124    --  end poPT__pP;
 125
 126    Null_Protected_Entry : constant := Null_Entry;
 127
 128    Max_Protected_Entry : constant := Max_Entry;
 129
 130    type Protected_Entry_Index is new Entry_Index
 131      range Null_Protected_Entry .. Max_Protected_Entry;
 132
 133    type Barrier_Function_Pointer is access
 134      function
 135        (O    : System.Address;
 136         E    : Protected_Entry_Index)
 137         return Boolean;
 138    --  Pointer to a function which evaluates the barrier of a protected
 139    --  entry body. O is a pointer to the compiler-generated record
 140    --  representing the protected object, and E is the index of the
 141    --  entry serviced by the body.
 142
 143    type Entry_Action_Pointer is access
 144      procedure
 145        (O : System.Address;
 146         P : System.Address;
 147         E : Protected_Entry_Index);
 148    --  Pointer to a procedure which executes the sequence of statements
 149    --  of a protected entry body. O is a pointer to the compiler-generated
 150    --  record representing the protected object, P is a pointer to the
 151    --  record of entry parameters, and E is the index of the
 152    --  entry serviced by the body.
 153
 154    type Entry_Body is record
 155       Barrier : Barrier_Function_Pointer;
 156       Action  : Entry_Action_Pointer;
 157    end record;
 158    --  The compiler-generated code passes objects of this type to the GNARL
 159    --  to allow it to access the executable code of an entry body.
 160
 161    type Entry_Body_Access is access all Entry_Body;
 162
 163    type Protection is limited private;
 164    --  This type contains the GNARL state of a protected object. The
 165    --  application-defined portion of the state (i.e. private objects)
 166    --  is maintained by the compiler-generated code.
 167    --  Note that there are now 2 Protection types. One for the simple
 168    --  case (no entries) and one for the general case that needs the whole
 169    --  Finalization mechanism.
 170    --  This split helps in the case of restricted run time where we want to
 171    --  minimize the size of the code.
 172
 173    type Protection_Access is access all Protection;
 174
 175    Null_PO : constant Protection_Access := null;
 176
 177    procedure Initialize_Protection
 178      (Object           : Protection_Access;
 179       Ceiling_Priority : Integer);
 180    --  Initialize the Object parameter so that it can be used by the runtime
 181    --  to keep track of the runtime state of a protected object.
 182
 183    procedure Lock (Object : Protection_Access);
 184    --  Lock a protected object for write access. Upon return, the caller
 185    --  owns the lock to this object, and no other call to Lock or
 186    --  Lock_Read_Only with the same argument will return until the
 187    --  corresponding call to Unlock has been made by the caller.
 188
 189    procedure Lock_Read_Only (Object : Protection_Access);
 190    --  Lock a protected object for read access. Upon return, the caller
 191    --  owns the lock for read access, and no other calls to Lock with the
 192    --  same argument will return until the corresponding call to Unlock
 193    --  has been made by the caller. Other calls to Lock_Read_Only may (but
 194    --  need not) return before the call to Unlock, and the corresponding
 195    --  callers will also own the lock for read access.
 196    --
 197    --  Note: we are not currently using this interface, it is provided
 198    --  for possible future use. At the current time, everyone uses Lock
 199    --  for both read and write locks.
 200
 201    procedure Unlock (Object : Protection_Access);
 202    --  Relinquish ownership of the lock for the object represented by
 203    --  the Object parameter. If this ownership was for write access, or
 204    --  if it was for read access where there are no other read access
 205    --  locks outstanding, one (or more, in the case of Lock_Read_Only)
 206    --  of the tasks waiting on this lock (if any) will be given the
 207    --  lock and allowed to return from the Lock or Lock_Read_Only call.
 208
 209 private
 210    type Protection is record
 211       L       : aliased Task_Primitives.Lock;
 212       Ceiling : System.Any_Priority;
 213    end record;
 214    pragma Volatile (Protection);
 215    for Protection'Alignment use Standard'Maximum_Alignment;
 216    --  Needed so that we can uncheck convert a Protection_Access to a
 217    --  Protection_Entries_Access.
 218
 219    procedure Finalize_Protection (Object : in out Protection);
 220    --  Clean up a Protection object; in particular, finalize the associated
 221    --  Lock object. The compiler generates automatically calls to this
 222    --  procedure
 223
 224 end System.Tasking.Protected_Objects;