| ------------------------------------------------------------------------------ |
| -- -- |
| -- 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; |
