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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2022, Free Software Foundation, Inc. --
-- --
-- GNAT 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);
-- 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;
type Entry_Body_Access is access constant Entry_Body;
-- Access to barrier and action function of an 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);
-- Make a protected entry call to the specified object
--
-- Pends 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.
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;