276 lines
12 KiB
Ada
276 lines
12 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2013, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNARL was developed by the GNARL team at Florida State University. --
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-- Extensive contributions were provided by Ada Core Technologies, Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package provides an optimized version of Protected_Objects.Operations
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-- and Protected_Objects.Entries making the following assumptions:
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-- PO have only one entry
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-- There is only one caller at a time (No_Entry_Queue)
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-- There is no dynamic priority support (No_Dynamic_Priorities)
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-- No Abort Statements
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-- (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)
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-- PO are at library level
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-- None of the tasks will terminate (no need for finalization)
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-- This interface is intended to be used in the Ravenscar profile, the
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-- compiler is responsible for ensuring that the conditions mentioned above
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-- are respected, except for the No_Entry_Queue restriction that is checked
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-- dynamically in this package, since the check cannot be performed at compile
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-- time, and is relatively cheap (see body).
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-- This package is part of the high level tasking interface used by the
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-- compiler to expand Ada 95 tasking constructs into simpler run time calls
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-- (aka GNARLI, GNU Ada Run-time Library Interface)
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-- Note: the compiler generates direct calls to this interface, via Rtsfind.
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-- Any changes to this interface may require corresponding compiler changes
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-- in exp_ch9.adb and possibly exp_ch7.adb
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package System.Tasking.Protected_Objects.Single_Entry is
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pragma Elaborate_Body;
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---------------------------------
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-- Compiler Interface (GNARLI) --
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---------------------------------
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-- The compiler will expand in the GNAT tree the following construct:
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-- protected PO is
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-- entry E;
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-- procedure P;
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-- private
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-- Open : Boolean := False;
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-- end PO;
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-- protected body PO is
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-- entry E when Open is
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-- ...variable declarations...
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-- begin
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-- ...B...
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-- end E;
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-- procedure P is
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-- ...variable declarations...
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-- begin
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-- ...C...
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-- end P;
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-- end PO;
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-- as follows:
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-- protected type poT is
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-- entry e;
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-- procedure p;
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-- private
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-- open : boolean := false;
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-- end poT;
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-- type poTV is limited record
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-- open : boolean := false;
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-- _object : aliased protection_entry;
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-- end record;
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-- procedure poPT__E1s (O : address; P : address; E :
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-- protected_entry_index);
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-- function poPT__B2s (O : address; E : protected_entry_index) return
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-- boolean;
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-- procedure poPT__pN (_object : in out poTV);
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-- procedure poPT__pP (_object : in out poTV);
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-- poTA : aliased entry_body := (
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-- barrier => poPT__B2s'unrestricted_access,
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-- action => poPT__E1s'unrestricted_access);
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-- freeze poTV [
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-- procedure poTVIP (_init : in out poTV) is
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-- begin
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-- _init.open := false;
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-- object-init-proc (_init._object);
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-- initialize_protection_entry (_init._object'unchecked_access,
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-- unspecified_priority, _init'address, poTA'
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-- unrestricted_access);
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-- return;
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-- end poTVIP;
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-- ]
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-- po : poT;
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-- poTVIP (poTV!(po));
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-- function poPT__B2s (O : address; E : protected_entry_index) return
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-- boolean is
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-- type poTVP is access poTV;
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-- _object : poTVP := poTVP!(O);
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-- poR : protection_entry renames _object._object;
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-- openP : boolean renames _object.open;
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-- begin
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-- return open;
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-- end poPT__B2s;
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-- procedure poPT__E1s (O : address; P : address; E :
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-- protected_entry_index) is
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-- type poTVP is access poTV;
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-- _object : poTVP := poTVP!(O);
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-- begin
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-- B1b : declare
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-- poR : protection_entry renames _object._object;
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-- openP : boolean renames _object.open;
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-- ...variable declarations...
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-- begin
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-- ...B...
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-- end B1b;
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-- complete_single_entry_body (_object._object'unchecked_access);
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-- return;
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-- exception
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-- when all others =>
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-- exceptional_complete_single_entry_body (_object._object'
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-- unchecked_access, get_gnat_exception);
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-- return;
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-- end poPT__E1s;
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-- procedure poPT__pN (_object : in out poTV) is
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-- poR : protection_entry renames _object._object;
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-- openP : boolean renames _object.open;
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-- ...variable declarations...
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-- begin
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-- ...C...
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-- return;
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-- end poPT__pN;
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-- procedure poPT__pP (_object : in out poTV) is
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-- procedure _clean is
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-- begin
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-- service_entry (_object._object'unchecked_access);
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-- return;
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-- end _clean;
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-- begin
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-- lock_entry (_object._object'unchecked_access);
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-- B5b : begin
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-- poPT__pN (_object);
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-- at end
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-- _clean;
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-- end B5b;
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-- return;
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-- end poPT__pP;
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type Protection_Entry is limited private;
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-- This type contains the GNARL state of a protected object. The
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-- application-defined portion of the state (i.e. private objects)
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-- is maintained by the compiler-generated code.
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type Protection_Entry_Access is access all Protection_Entry;
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procedure Initialize_Protection_Entry
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(Object : Protection_Entry_Access;
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Ceiling_Priority : Integer;
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Compiler_Info : System.Address;
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Entry_Body : Entry_Body_Access);
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-- Initialize the Object parameter so that it can be used by the run time
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-- to keep track of the runtime state of a protected object.
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procedure Lock_Entry (Object : Protection_Entry_Access);
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-- Lock a protected object for write access. Upon return, the caller owns
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-- the lock to this object, and no other call to Lock or Lock_Read_Only
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-- with the same argument will return until the corresponding call to
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-- Unlock has been made by the caller.
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procedure Lock_Read_Only_Entry
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(Object : Protection_Entry_Access);
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-- Lock a protected object for read access. Upon return, the caller owns
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-- the lock for read access, and no other calls to Lock with the same
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-- argument will return until the corresponding call to Unlock has been
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-- made by the caller. Other calls to Lock_Read_Only may (but need not)
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-- return before the call to Unlock, and the corresponding callers will
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-- also own the lock for read access.
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procedure Unlock_Entry (Object : Protection_Entry_Access);
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-- Relinquish ownership of the lock for the object represented by the
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-- Object parameter. If this ownership was for write access, or if it was
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-- for read access where there are no other read access locks outstanding,
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-- one (or more, in the case of Lock_Read_Only) of the tasks waiting on
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-- this lock (if any) will be given the lock and allowed to return from
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-- the Lock or Lock_Read_Only call.
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procedure Service_Entry (Object : Protection_Entry_Access);
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-- Service the entry queue of the specified object, executing the
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-- corresponding body of any queued entry call that is waiting on True
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-- barrier. This is used when the state of a protected object may have
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-- changed, in particular after the execution of the statement sequence
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-- of a protected procedure.
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--
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-- This must be called with abort deferred and with the corresponding
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-- object locked. Object is unlocked on return.
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procedure Protected_Single_Entry_Call
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(Object : Protection_Entry_Access;
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Uninterpreted_Data : System.Address);
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-- Make a protected entry call to the specified object
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--
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-- Pends a protected entry call on the protected object represented by
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-- Object. A pended call is not queued; it may be executed immediately
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-- or queued, depending on the state of the entry barrier.
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--
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-- Uninterpreted_Data
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-- This will be returned by Next_Entry_Call when this call is serviced.
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-- It can be used by the compiler to pass information between the
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-- caller and the server, in particular entry parameters.
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procedure Exceptional_Complete_Single_Entry_Body
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(Object : Protection_Entry_Access;
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Ex : Ada.Exceptions.Exception_Id);
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-- Perform all of the functions of Complete_Entry_Body. In addition, report
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-- in Ex the exception whose propagation terminated the entry body to the
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-- runtime system.
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function Protected_Count_Entry (Object : Protection_Entry) return Natural;
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-- Return the number of entry calls on Object (0 or 1)
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function Protected_Single_Entry_Caller
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(Object : Protection_Entry) return Task_Id;
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-- Return value of E'Caller, where E is the protected entry currently being
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-- handled. This will only work if called from within an entry body, as
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-- required by the LRM (C.7.1(14)).
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private
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type Protection_Entry is record
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Common : aliased Protection;
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-- State of the protected object. This part is common to any protected
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-- object, including those without entries.
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Compiler_Info : System.Address;
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-- Pointer to compiler-generated record representing protected object
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Call_In_Progress : Entry_Call_Link;
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-- Pointer to the entry call being executed (if any)
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Entry_Body : Entry_Body_Access;
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-- Pointer to executable code for the entry body of the protected type
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Entry_Queue : Entry_Call_Link;
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-- Place to store the waiting entry call (if any)
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end record;
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end System.Tasking.Protected_Objects.Single_Entry;
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