Subversion Repositories scarts

------------------------------------------------------------------------------

--                                                                          --

--                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 .   --

--                               E N T R I E 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 contains all the simple primitives related to

--  Protected_Objects with entries (i.e init, lock, unlock).

--  The handling of protected objects with no entries is done in

--  System.Tasking.Protected_Objects, the complex routines for protected

--  objects with entries in System.Tasking.Protected_Objects.Operations.

--  The split between Entries and Operations is needed to break circular

--  dependencies inside the run time.

--  Note: the compiler generates direct calls to this interface, via Rtsfind.

--  Any changes to this interface may require corresponding compiler changes.

with Ada.Finalization;

--  used for Limited_Controlled

with Unchecked_Conversion;

package System.Tasking.Protected_Objects.Entries is

   pragma Elaborate_Body;

   subtype Positive_Protected_Entry_Index is

     Protected_Entry_Index range  1 .. Protected_Entry_Index'Last;

   type Find_Body_Index_Access is access

     function

       (O : System.Address;

        E : Protected_Entry_Index)

        return Protected_Entry_Index;

   type Protected_Entry_Body_Array is

     array (Positive_Protected_Entry_Index range <>) of Entry_Body;

   --  This is an array of the executable code for all entry bodies of

   --  a protected type.

   type Protected_Entry_Body_Access is access all Protected_Entry_Body_Array;

   type Protected_Entry_Queue_Array is

     array (Protected_Entry_Index range <>) of Entry_Queue;

   --  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 is a simplified version of this type declared in

   --  System.Tasking.PO_Simple that handle the simple case (no entries).

   type Protection_Entries (Num_Entries : Protected_Entry_Index) is new

     Ada.Finalization.Limited_Controlled

   with record

      L                 : aliased Task_Primitives.Lock;

      --  The underlying lock associated with a Protection_Entries.

      --  Note that you should never (un)lock Object.L directly, but instead

      --  use Lock_Entries/Unlock_Entries.

      Compiler_Info : System.Address;

      --  Pointer to compiler-generated record representing protected object

      Call_In_Progress : Entry_Call_Link;

      --  Pointer to the entry call being executed (if any)

      Ceiling : System.Any_Priority;

      --  Ceiling priority associated with 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).

      Old_Base_Priority : System.Any_Priority;

      --  Task's base priority when the protected operation was called

      Pending_Action  : Boolean;

      --  Flag indicating that priority has been dipped temporarily in order

      --  to avoid violating the priority ceiling of the lock associated with

      --  this protected object, in Lock_Server. The flag tells Unlock_Server

      --  or Unlock_And_Update_Server to restore the old priority to

      --  Old_Base_Priority. This is needed because of situations (bad

      --  language design?) where one needs to lock a PO but to do so would

      --  violate the priority ceiling. For example, this can happen when an

      --  entry call has been requeued to a lower-priority object, and the

      --  caller then tries to cancel the call while its own priority is

      --  higher than the ceiling of the new PO.

      Finalized : Boolean := False;

      --  Set to True by Finalize to make this routine idempotent

      Entry_Bodies : Protected_Entry_Body_Access;

      --  Pointer to an array containing the executable code for all entry

      --  bodies of a protected type.

      --  The following function maps the entry index in a call (which denotes

      --  the queue to the proper entry) into the body of the entry.

      Find_Body_Index : Find_Body_Index_Access;

      Entry_Queues      : Protected_Entry_Queue_Array (1 .. Num_Entries);

   end record;

   --  No default initial values for this type, since call records

   --  will need to be re-initialized before every use.

   type Protection_Entries_Access is access all Protection_Entries'Class;

   --  See comments in s-tassta.adb about the implicit call to Current_Master

   --  generated by this declaration.

   function To_Address is

     new Unchecked_Conversion (Protection_Entries_Access, System.Address);

   function To_Protection is

     new Unchecked_Conversion (System.Address, Protection_Entries_Access);

   function Has_Interrupt_Or_Attach_Handler

     (Object : Protection_Entries_Access) return Boolean;

   --  Returns True if an Interrupt_Handler or Attach_Handler pragma applies

   --  to the protected object. That is to say this primitive returns False for

   --  Protection, but is overriden to return True when interrupt handlers are

   --  declared so the check required by C.3.1(11) can be implemented in

   --  System.Tasking.Protected_Objects.Initialize_Protection.

   procedure Initialize_Protection_Entries

     (Object           : Protection_Entries_Access;

      Ceiling_Priority : Integer;

      Compiler_Info    : System.Address;

      Entry_Bodies     : Protected_Entry_Body_Access;

      Find_Body_Index  : Find_Body_Index_Access);

   --  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_Entries (Object : Protection_Entries_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. Program_Error is raised in case of

   --  ceiling violation.

   procedure Lock_Entries

     (Object : Protection_Entries_Access; Ceiling_Violation : out Boolean);

   --  Same as above, but return the ceiling violation status instead of

   --  raising Program_Error.

   procedure Lock_Read_Only_Entries (Object : Protection_Entries_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_Entries (Object : Protection_Entries_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

   procedure Finalize (Object : in out Protection_Entries);

   --  Clean up a Protection object; in particular, finalize the associated

   --  Lock object.

end System.Tasking.Protected_Objects.Entries;