| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- |
| -- -- |
| -- 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 -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 1992-2005, Free Software Foundation, Inc. -- |
| -- -- |
| -- GNARL is free software; you can redistribute it and/or modify it under -- |
| -- terms of the GNU General Public License as published by the Free Soft- -- |
| -- ware Foundation; either version 2, or (at your option) any later ver- -- |
| -- sion. GNARL is distributed in the hope that it will be useful, but WITH- -- |
| -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- |
| -- for more details. You should have received a copy of the GNU General -- |
| -- Public License distributed with GNARL; see file COPYING. If not, write -- |
| -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, -- |
| -- Boston, MA 02110-1301, USA. -- |
| -- -- |
| -- As a special exception, if other files instantiate generics from this -- |
| -- unit, or you link this unit with other files to produce an executable, -- |
| -- this unit does not by itself cause the resulting executable to be -- |
| -- covered by the GNU General Public License. This exception does not -- |
| -- however invalidate any other reasons why the executable file might be -- |
| -- covered by the GNU Public License. -- |
| -- -- |
| -- GNARL was developed by the GNARL team at Florida State University. -- |
| -- Extensive contributions were provided by Ada Core Technologies, Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- This package provides necessary definitions to handle simple (i.e without |
| -- entries) protected objects. |
| |
| -- All the routines that handle protected objects with entries have been moved |
| -- to two children: Entries and Operations. Note that Entries only contains |
| -- the type declaration and the OO primitives. This is needed to avoid |
| -- circular dependency. |
| |
| -- This package is part of the high level tasking interface used by the |
| -- compiler to expand Ada 95 tasking constructs into simpler run time calls |
| -- (aka GNARLI, GNU Ada Run-time Library Interface) |
| |
| -- Note: the compiler generates direct calls to this interface, via Rtsfind. |
| -- Any changes to this interface may require corresponding compiler changes |
| -- in exp_ch9.adb and possibly exp_ch7.adb |
| |
| package System.Tasking.Protected_Objects is |
| pragma Elaborate_Body; |
| |
| --------------------------------- |
| -- Compiler Interface (GNARLI) -- |
| --------------------------------- |
| |
| -- The compiler will expand in the GNAT tree the following construct: |
| |
| -- protected PO is |
| -- procedure P; |
| -- private |
| -- open : boolean := false; |
| -- end PO; |
| |
| -- protected body PO is |
| -- procedure P is |
| -- ...variable declarations... |
| -- begin |
| -- ...B... |
| -- end P; |
| -- end PO; |
| |
| -- as follows: |
| |
| -- protected type poT is |
| -- procedure p; |
| -- private |
| -- open : boolean := false; |
| -- end poT; |
| -- type poTV is limited record |
| -- open : boolean := false; |
| -- _object : aliased protection; |
| -- end record; |
| -- procedure poPT__pN (_object : in out poTV); |
| -- procedure poPT__pP (_object : in out poTV); |
| -- freeze poTV [ |
| -- procedure poTVI (_init : in out poTV) is |
| -- begin |
| -- _init.open := false; |
| -- object-init-proc (_init._object); |
| -- initialize_protection (_init._object'unchecked_access, |
| -- unspecified_priority); |
| -- return; |
| -- end _init_proc; |
| -- ] |
| -- po : poT; |
| -- poTVI (poTV!(po)); |
| |
| -- procedure poPT__pN (_object : in out poTV) is |
| -- poR : protection renames _object._object; |
| -- openP : boolean renames _object.open; |
| -- ...variable declarations... |
| -- begin |
| -- ...B... |
| -- return; |
| -- end poPT__pN; |
| |
| -- procedure poPT__pP (_object : in out poTV) is |
| -- procedure _clean is |
| -- begin |
| -- unlock (_object._object'unchecked_access); |
| -- return; |
| -- end _clean; |
| -- begin |
| -- lock (_object._object'unchecked_access); |
| -- B2b : begin |
| -- poPT__pN (_object); |
| -- at end |
| -- _clean; |
| -- end B2b; |
| -- return; |
| -- end poPT__pP; |
| |
| Null_Protected_Entry : constant := Null_Entry; |
| |
| Max_Protected_Entry : constant := Max_Entry; |
| |
| type Protected_Entry_Index is new Entry_Index |
| range Null_Protected_Entry .. Max_Protected_Entry; |
| |
| type Barrier_Function_Pointer is access |
| function |
| (O : System.Address; |
| E : Protected_Entry_Index) |
| return Boolean; |
| -- Pointer to a function which evaluates the barrier of a protected |
| -- entry body. O is a pointer to the compiler-generated record |
| -- representing the protected object, and E is the index of the |
| -- entry serviced by the body. |
| |
| type Entry_Action_Pointer is access |
| procedure |
| (O : System.Address; |
| P : System.Address; |
| E : Protected_Entry_Index); |
| -- Pointer to a procedure which executes the sequence of statements |
| -- of a protected entry body. O is a pointer to the compiler-generated |
| -- record representing the protected object, P is a pointer to the |
| -- record of entry parameters, and E is the index of the |
| -- entry serviced by the body. |
| |
| type Entry_Body is record |
| Barrier : Barrier_Function_Pointer; |
| Action : Entry_Action_Pointer; |
| end record; |
| -- The compiler-generated code passes objects of this type to the GNARL |
| -- to allow it to access the executable code of an entry body. |
| |
| type Entry_Body_Access is access all Entry_Body; |
| |
| type Protection is limited private; |
| -- This type contains the GNARL state of a protected object. The |
| -- application-defined portion of the state (i.e. private objects) |
| -- is maintained by the compiler-generated code. |
| -- Note that there are now 2 Protection types. One for the simple |
| -- case (no entries) and one for the general case that needs the whole |
| -- Finalization mechanism. |
| -- This split helps in the case of restricted run time where we want to |
| -- minimize the size of the code. |
| |
| type Protection_Access is access all Protection; |
| |
| Null_PO : constant Protection_Access := null; |
| |
| procedure Initialize_Protection |
| (Object : Protection_Access; |
| Ceiling_Priority : Integer); |
| -- Initialize the Object parameter so that it can be used by the runtime |
| -- to keep track of the runtime state of a protected object. |
| |
| procedure Lock (Object : Protection_Access); |
| -- Lock a protected object for write access. Upon return, the caller |
| -- owns the lock to this object, and no other call to Lock or |
| -- Lock_Read_Only with the same argument will return until the |
| -- corresponding call to Unlock has been made by the caller. |
| |
| procedure Lock_Read_Only (Object : Protection_Access); |
| -- Lock a protected object for read access. Upon return, the caller |
| -- owns the lock for read access, and no other calls to Lock with the |
| -- same argument will return until the corresponding call to Unlock |
| -- has been made by the caller. Other calls to Lock_Read_Only may (but |
| -- need not) return before the call to Unlock, and the corresponding |
| -- callers will also own the lock for read access. |
| -- |
| -- Note: we are not currently using this interface, it is provided |
| -- for possible future use. At the current time, everyone uses Lock |
| -- for both read and write locks. |
| |
| procedure Unlock (Object : Protection_Access); |
| -- Relinquish ownership of the lock for the object represented by |
| -- the Object parameter. If this ownership was for write access, or |
| -- if it was for read access where there are no other read access |
| -- locks outstanding, one (or more, in the case of Lock_Read_Only) |
| -- of the tasks waiting on this lock (if any) will be given the |
| -- lock and allowed to return from the Lock or Lock_Read_Only call. |
| |
| private |
| type Protection is record |
| L : aliased Task_Primitives.Lock; |
| -- Lock used to ensure mutual exclusive access to the protected object |
| |
| Ceiling : System.Any_Priority; |
| -- Ceiling priority associated to the protected object |
| |
| Owner : Task_Id; |
| -- This field contains the protected object's owner. Null_Task |
| -- indicates that the protected object is not currently being used. |
| -- This information is used for detecting the type of potentially |
| -- blocking operations described in the ARM 9.5.1, par. 15 (external |
| -- calls on a protected subprogram with the same target object as that |
| -- of the protected action). |
| end record; |
| |
| procedure Finalize_Protection (Object : in out Protection); |
| -- Clean up a Protection object (in particular, finalize the associated |
| -- Lock object). The compiler generates calls automatically to this |
| -- procedure |
| |
| end System.Tasking.Protected_Objects; |
