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

--                                                                          --

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

--                                                                          --

--             S Y S T E M . T A S K I N G . R E N D E Z V O U S            --

--                                                                          --

--                                  S p e c                                 --

--                                                                          --

--          Copyright (C) 1992-2012, 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.     --

--                                                                          --

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

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

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

with Ada.Exceptions;

with System.Tasking.Protected_Objects.Entries;

package System.Tasking.Rendezvous is

   package STPE renames System.Tasking.Protected_Objects.Entries;

   procedure Task_Entry_Call

     (Acceptor              : Task_Id;

      E                     : Task_Entry_Index;

      Uninterpreted_Data    : System.Address;

      Mode                  : Call_Modes;

      Rendezvous_Successful : out Boolean);

   --  General entry call used to implement ATC or conditional entry calls.

   --  Compiler interface only. Do not call from within the RTS.

   --  Acceptor is the ID of the acceptor task.

   --  E is the entry index requested.

   --  Uninterpreted_Data represents the parameters of the entry. It is

   --  constructed by the compiler for the caller and the callee; therefore,

   --  the run time never needs to decode this data.

   --  Mode can be either Asynchronous_Call (ATC) or Conditional_Call.

   --  Rendezvous_Successful is set to True on return if the call was serviced.

   procedure Timed_Task_Entry_Call

     (Acceptor              : Task_Id;

      E                     : Task_Entry_Index;

      Uninterpreted_Data    : System.Address;

      Timeout               : Duration;

      Mode                  : Delay_Modes;

      Rendezvous_Successful : out Boolean);

   --  Timed entry call without using ATC.

   --  Compiler interface only. Do not call from within the RTS.

   --  See Task_Entry_Call for details on Acceptor, E and Uninterpreted_Data.

   --  Timeout is the value of the time out.

   --  Mode determines whether the delay is relative or absolute.

   procedure Call_Simple

     (Acceptor           : Task_Id;

      E                  : Task_Entry_Index;

      Uninterpreted_Data : System.Address);

   --  Simple entry call.

   --  Compiler interface only. Do not call from within the RTS.

   --

   --  source:

   --     T.E1 (Params);

   --

   --  expansion:

   --    declare

   --       P : parms := (parm1, parm2, parm3);

   --       X : Task_Entry_Index := 1;

   --    begin

   --       Call_Simple (t._task_id, X, P'Address);

   --       parm1 := P.param1;

   --       parm2 := P.param2;

   --       ...

   --    end;

   procedure Cancel_Task_Entry_Call (Cancelled : out Boolean);

   --  Cancel pending asynchronous task entry call.

   --  Compiler interface only. Do not call from within the RTS.

   --  See Exp_Ch9.Expand_N_Asynchronous_Select for code expansion.

   procedure Requeue_Task_Entry

     (Acceptor   : Task_Id;

      E          : Task_Entry_Index;

      With_Abort : Boolean);

   --  Requeue from a task entry to a task entry.

   --  Compiler interface only. Do not call from within the RTS.

   --  The code generation for task entry requeues is different from that for

   --  protected entry requeues. There is a "goto" that skips around the call

   --  to Complete_Rendezvous, so that Requeue_Task_Entry must also do the work

   --  of Complete_Rendezvous. The difference is that it does not report that

   --  the call's State = Done.

   --

   --  source:

   --     accept e1 do

   --       ...A...

   --       requeue e2;

   --       ...B...

   --     end e1;

   --

   --  expansion:

   --     A62b : address;

   --     L61b : label

   --     begin

   --        accept_call (1, A62b);

   --        ...A...

   --        requeue_task_entry (tTV!(t)._task_id, 2, false);

   --        goto L61b;

   --        ...B...

   --        complete_rendezvous;

   --        <<L61b>>

   --     exception

   --        when others =>

   --           exceptional_complete_rendezvous (current_exception);

   --     end;

   procedure Requeue_Protected_To_Task_Entry

     (Object     : STPE.Protection_Entries_Access;

      Acceptor   : Task_Id;

      E          : Task_Entry_Index;

      With_Abort : Boolean);

   --  Requeue from a protected entry to a task entry.

   --  Compiler interface only. Do not call from within the RTS.

   --

   --  source:

   --     entry e2 when b is

   --     begin

   --        b := false;

   --        ...A...

   --        requeue t.e2;

   --     end e2;

   --

   --  expansion:

   --     procedure rPT__E14b (O : address; P : address; E :

   --       protected_entry_index) is

   --        type rTVP is access rTV;

   --        freeze rTVP []

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

   --     begin

   --        declare

   --           rR : protection renames _object._object;

   --           vP : integer renames _object.v;

   --           bP : boolean renames _object.b;

   --        begin

   --           b := false;

   --           ...A...

   --           requeue_protected_to_task_entry (rR'unchecked_access, tTV!(t).

   --             _task_id, 2, false);

   --           return;

   --        end;

   --        complete_entry_body (_object._object'unchecked_access, objectF =>

   --          0);

   --        return;

   --     exception

   --        when others =>

   --           abort_undefer.all;

   --           exceptional_complete_entry_body (_object._object'

   --             unchecked_access, current_exception, objectF => 0);

   --           return;

   --     end rPT__E14b;

   procedure Selective_Wait

     (Open_Accepts       : Accept_List_Access;

      Select_Mode        : Select_Modes;

      Uninterpreted_Data : out System.Address;

      Index              : out Select_Index);

   --  Implement select statement.

   --  Compiler interface only. Do not call from within the RTS.

   --  See comments on Accept_Call.

   --

   --  source:

   --     select accept e1 do

   --           ...A...

   --        end e1;

   --        ...B...

   --     or accept e2;

   --        ...C...

   --     end select;

   --

   --  expansion:

   --     A32b : address;

   --     declare

   --        A37b : T36b;

   --        A37b (1) := (null_body => false, s => 1);

   --        A37b (2) := (null_body => true, s => 2);

   --        S0 : aliased T36b := accept_list'A37b;

   --        J1 : select_index := 0;

   --        procedure e1A is

   --        begin

   --           abort_undefer.all;

   --           ...A...

   --           <<L31b>>

   --           complete_rendezvous;

   --        exception

   --           when all others =>

   --              exceptional_complete_rendezvous (get_gnat_exception);

   --        end e1A;

   --     begin

   --        selective_wait (S0'unchecked_access, simple_mode, A32b, J1);

   --        case J1 is

   --           when 0 =>

   --              goto L3;

   --           when 1 =>

   --              e1A;

   --              goto L1;

   --           when 2 =>

   --              goto L2;

   --           when others =>

   --              goto L3;

   --        end case;

   --        <<L1>>

   --        ...B...

   --        goto L3;

   --        <<L2>>

   --        ...C...

   --        goto L3;

   --        <<L3>>

   --     end;

   procedure Timed_Selective_Wait

     (Open_Accepts       : Accept_List_Access;

      Select_Mode        : Select_Modes;

      Uninterpreted_Data : out System.Address;

      Timeout            : Duration;

      Mode               : Delay_Modes;

      Index              : out Select_Index);

   --  Selective wait with timeout without using ATC.

   --  Compiler interface only. Do not call from within the RTS.

   procedure Accept_Call

     (E                  : Task_Entry_Index;

      Uninterpreted_Data : out System.Address);

   --  Accept an entry call.

   --  Compiler interface only. Do not call from within the RTS.

   --

   --  source:

   --              accept E do  ...A... end E;

   --  expansion:

   --              A27b : address;

   --              L26b : label

   --              begin

   --                 accept_call (1, A27b);

   --                 ...A...

   --                 complete_rendezvous;

   --              <<L26b>>

   --              exception

   --              when all others =>

   --                 exceptional_complete_rendezvous (get_gnat_exception);

   --              end;

   --

   --  The handler for Abort_Signal (*all* others) is to handle the case when

   --  the acceptor is aborted between Accept_Call and the corresponding

   --  Complete_Rendezvous call. We need to wake up the caller in this case.

   --

   --   See also Selective_Wait

   procedure Accept_Trivial (E : Task_Entry_Index);

   --  Accept an entry call that has no parameters and no body.

   --  Compiler interface only. Do not call from within the RTS.

   --  This should only be called when there is no accept body, or the accept

   --  body is empty.

   --

   --  source:

   --               accept E;

   --  expansion:

   --               accept_trivial (1);

   --

   --  The compiler is also able to recognize the following and

   --  translate it the same way.

   --

   --     accept E do null; end E;

   function Task_Count (E : Task_Entry_Index) return Natural;

   --  Return number of tasks waiting on the entry E (of current task)

   --  Compiler interface only. Do not call from within the RTS.

   function Callable (T : Task_Id) return Boolean;

   --  Return T'Callable

   --  Compiler interface. Do not call from within the RTS, except for body of

   --  Ada.Task_Identification.

   type Task_Entry_Nesting_Depth is new Task_Entry_Index

     range 0 .. Max_Task_Entry;

   function Task_Entry_Caller (D : Task_Entry_Nesting_Depth) return Task_Id;

   --  Return E'Caller. This will only work if called from within an

   --  accept statement that is handling E, as required by the LRM (C.7.1(14)).

   --  Compiler interface only. Do not call from within the RTS.

   procedure Complete_Rendezvous;

   --  Called by acceptor to wake up caller

   procedure Exceptional_Complete_Rendezvous

     (Ex : Ada.Exceptions.Exception_Id);

   pragma No_Return (Exceptional_Complete_Rendezvous);

   --  Called by acceptor to mark the end of the current rendezvous and

   --  propagate an exception to the caller.

   --  For internal use only:

   function Task_Do_Or_Queue

     (Self_ID    : Task_Id;

      Entry_Call : Entry_Call_Link) return Boolean;

   --  Call this only with abort deferred and holding no locks, except

   --  the global RTS lock when Single_Lock is True which must be owned.

   --  Returns False iff the call cannot be served or queued, as is the

   --  case if the caller is not callable; i.e., a False return value

   --  indicates that Tasking_Error should be raised.

   --  Either initiate the entry call, such that the accepting task is

   --  free to execute the rendezvous, queue the call on the acceptor's

   --  queue, or cancel the call. Conditional calls that cannot be

   --  accepted immediately are cancelled.

end System.Tasking.Rendezvous;