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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) 1992-2009, 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. --
-- --
------------------------------------------------------------------------------
-- 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);
-- 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;
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