------------------------------------------------------------------------------ -- -- -- GNU ADA 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) 1992-2001, 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, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, 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 _init_proc (_init : in out poTV) is -- begin -- _init.open := false; -- _init_proc (_init._object); -- initialize_protection (_init._object'unchecked_access, -- unspecified_priority); -- return; -- end _init_proc; -- ] -- po : poT; -- _init_proc (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; Ceiling : System.Any_Priority; end record; pragma Volatile (Protection); for Protection'Alignment use Standard'Maximum_Alignment; -- Needed so that we can uncheck convert a Protection_Access to a -- Protection_Entries_Access. procedure Finalize_Protection (Object : in out Protection); -- Clean up a Protection object; in particular, finalize the associated -- Lock object. The compiler generates automatically calls to this -- procedure end System.Tasking.Protected_Objects;