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

--                                                                          --

--                GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                  --

--                                                                          --

--             SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY                --

--                                                                          --

--                                  S p e c                                 --

--                                                                          --

--          Copyright (C) 1992-2009, 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 3,  or (at your option) any later ver- --

-- sion.  GNAT 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.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNARL was developed by the GNARL team at Florida State University.       --

-- Extensive contributions were provided by Ada Core Technologies, Inc.     --

--                                                                          --

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

--  This package provides an optimized version of Protected_Objects.Operations

--  and Protected_Objects.Entries making the following assumptions:

--

--    PO have only one entry

--    There is only one caller at a time (No_Entry_Queue)

--    There is no dynamic priority support (No_Dynamic_Priorities)

--    No Abort Statements

--      (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)

--    PO are at library level

--    None of the tasks will terminate (no need for finalization)

--

--  This interface is intended to be used in the ravenscar profile, the

--  compiler is responsible for ensuring that the conditions mentioned above

--  are respected, except for the No_Entry_Queue restriction that is checked

--  dynamically in this package, since the check cannot be performed at compile

--  time, and is relatively cheap (see body).

--

--  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.Single_Entry is

   pragma Elaborate_Body;

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

   -- Compiler Interface (GNARLI) --

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

   --  The compiler will expand in the GNAT tree the following construct:

   --  protected PO is

   --     entry E;

   --     procedure P;

   --  private

   --     Open : Boolean := False;

   --  end PO;

   --  protected body PO is

   --     entry E when Open is

   --        ...variable declarations...

   --     begin

   --        ...B...

   --     end E;

   --     procedure P is

   --        ...variable declarations...

   --     begin

   --        ...C...

   --     end P;

   --  end PO;

   --  as follows:

   --  protected type poT is

   --     entry e;

   --     procedure p;

   --  private

   --     open : boolean := false;

   --  end poT;

   --  type poTV is limited record

   --     open : boolean := false;

   --     _object : aliased protection_entry;

   --  end record;

   --  procedure poPT__E1s (O : address; P : address; E :

   --    protected_entry_index);

   --  function poPT__B2s (O : address; E : protected_entry_index) return

   --    boolean;

   --  procedure poPT__pN (_object : in out poTV);

   --  procedure poPT__pP (_object : in out poTV);

   --  poTA : aliased entry_body := (

   --     barrier => poPT__B2s'unrestricted_access,

   --     action => poPT__E1s'unrestricted_access);

   --  freeze poTV [

   --     procedure poTVIP (_init : in out poTV) is

   --     begin

   --        _init.open := false;

   --        object-init-proc (_init._object);

   --        initialize_protection_entry (_init._object'unchecked_access,

   --          unspecified_priority, _init'address, poTA'

   --          unrestricted_access);

   --        return;

   --     end poTVIP;

   --  ]

   --  po : poT;

   --  poTVIP (poTV!(po));

   --  function poPT__B2s (O : address; E : protected_entry_index) return

   --    boolean is

   --     type poTVP is access poTV;

   --     _object : poTVP := poTVP!(O);

   --     poR : protection_entry renames _object._object;

   --     openP : boolean renames _object.open;

   --  begin

   --     return open;

   --  end poPT__B2s;

   --  procedure poPT__E1s (O : address; P : address; E :

   --    protected_entry_index) is

   --     type poTVP is access poTV;

   --     _object : poTVP := poTVP!(O);

   --  begin

   --     B1b : declare

   --        poR : protection_entry renames _object._object;

   --        openP : boolean renames _object.open;

   --        ...variable declarations...

   --     begin

   --        ...B...

   --     end B1b;

   --     complete_single_entry_body (_object._object'unchecked_access);

   --     return;

   --  exception

   --     when all others =>

   --        exceptional_complete_single_entry_body (_object._object'

   --          unchecked_access, get_gnat_exception);

   --        return;

   --  end poPT__E1s;

   --  procedure poPT__pN (_object : in out poTV) is

   --     poR : protection_entry renames _object._object;

   --     openP : boolean renames _object.open;

   --     ...variable declarations...

   --  begin

   --     ...C...

   --     return;

   --  end poPT__pN;

   --  procedure poPT__pP (_object : in out poTV) is

   --     procedure _clean is

   --     begin

   --        service_entry (_object._object'unchecked_access);

   --        unlock_entry (_object._object'unchecked_access);

   --        return;

   --     end _clean;

   --  begin

   --     lock_entry (_object._object'unchecked_access);

   --     B5b : begin

   --        poPT__pN (_object);

   --     at end

   --        _clean;

   --     end B5b;

   --     return;

   --  end poPT__pP;

   type Protection_Entry 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.

   type Protection_Entry_Access is access all Protection_Entry;

   procedure Initialize_Protection_Entry

     (Object            : Protection_Entry_Access;

      Ceiling_Priority  : Integer;

      Compiler_Info     : System.Address;

      Entry_Body        : Entry_Body_Access);

   --  Initialize the Object parameter so that it can be used by the run time

   --  to keep track of the runtime state of a protected object.

   procedure Lock_Entry (Object : Protection_Entry_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_Entry

     (Object : Protection_Entry_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.

   procedure Unlock_Entry (Object : Protection_Entry_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.

   procedure Service_Entry (Object : Protection_Entry_Access);

   --  Service the entry queue of the specified object, executing the

   --  corresponding body of any queued entry call that is waiting on True

   --  barrier. This is used when the state of a protected object may have

   --  changed, in particular after the execution of the statement sequence of

   --  a protected procedure.

   --

   --  This must be called with abort deferred and with the corresponding

   --  object locked. Object is unlocked on return.

   procedure Protected_Single_Entry_Call

     (Object              : Protection_Entry_Access;

      Uninterpreted_Data  : System.Address;

      Mode                : Call_Modes);

   --  Make a protected entry call to the specified object.

   --  Pend a protected entry call on the protected object represented

   --  by Object. A pended call is not queued; it may be executed immediately

   --  or queued, depending on the state of the entry barrier.

   --

   --    Uninterpreted_Data

   --      This will be returned by Next_Entry_Call when this call is serviced.

   --      It can be used by the compiler to pass information between the

   --      caller and the server, in particular entry parameters.

   --

   --    Mode

   --      The kind of call to be pended

   procedure Timed_Protected_Single_Entry_Call

     (Object                : Protection_Entry_Access;

      Uninterpreted_Data    : System.Address;

      Timeout               : Duration;

      Mode                  : Delay_Modes;

      Entry_Call_Successful : out Boolean);

   --  Same as the Protected_Entry_Call but with time-out specified.

   --  This routine is used to implement timed entry calls.

   procedure Complete_Single_Entry_Body

     (Object : Protection_Entry_Access);

   pragma Inline (Complete_Single_Entry_Body);

   --  Called from within an entry body procedure, indicates that the

   --  corresponding entry call has been serviced.

   procedure Exceptional_Complete_Single_Entry_Body

     (Object : Protection_Entry_Access;

      Ex     : Ada.Exceptions.Exception_Id);

   --  Perform all of the functions of Complete_Entry_Body. In addition,

   --  report in Ex the exception whose propagation terminated the entry

   --  body to the runtime system.

   function Protected_Count_Entry (Object : Protection_Entry)

     return Natural;

   --  Return the number of entry calls on Object (0 or 1)

   function Protected_Single_Entry_Caller (Object : Protection_Entry)

     return Task_Id;

   --  Return value of E'Caller, where E is the protected entry currently

   --  being handled. This will only work if called from within an

   --  entry body, as required by the LRM (C.7.1(14)).

private

   type Protection_Entry is record

      Common : aliased Protection;

      --  State of the protected object. This part is common to any protected

      --  object, including those without 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)

      Entry_Body : Entry_Body_Access;

      --  Pointer to executable code for the entry body of the protected type

      Entry_Queue : Entry_Call_Link;

      --  Place to store the waiting entry call (if any)

   end record;

end System.Tasking.Protected_Objects.Single_Entry;