------------------------------------------------------------------------------
--                                                                          --
--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
--                                                                          --
--            S Y S T E M . I N T E R R U P T _ M A N A G E M E N T         --
--                                                                          --
--                                  S p e c                                 --
--                                                                          --
--          Copyright (C) 1992-2021, 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.     --
--                                                                          --
------------------------------------------------------------------------------

--  This package encapsulates and centralizes information about all uses of
--  interrupts (or signals), including the target-dependent mapping of
--  interrupts (or signals) to exceptions.

--  Unlike the original design, System.Interrupt_Management can only be used
--  for tasking systems.

--  PLEASE DO NOT put any subprogram declarations with arguments of type
--  Interrupt_ID into the visible part of this package. The type Interrupt_ID
--  is used to derive the type in Ada.Interrupts, and adding more operations
--  to that type would be illegal according to the Ada Reference Manual. This
--  is the reason why the signals sets are implemented using visible arrays
--  rather than functions.

with System.OS_Interface;

with Interfaces.C;

package System.Interrupt_Management is
   pragma Preelaborate;

   type Interrupt_Mask is limited private;

   type Interrupt_ID is new Interfaces.C.int
     range 0 .. System.OS_Interface.Max_Interrupt;

   type Interrupt_Set is array (Interrupt_ID) of Boolean;

   --  The following objects serve as constants, but are initialized in the
   --  body to aid portability. This permits us to use more portable names for
   --  interrupts, where distinct names may map to the same interrupt ID
   --  value.

   --  For example, suppose SIGRARE is a signal that is not defined on all
   --  systems, but is always reserved when it is defined. If we have the
   --  convention that ID zero is not used for any "real" signals, and SIGRARE
   --  = 0 when SIGRARE is not one of the locally supported signals, we can
   --  write:
   --     Reserved (SIGRARE) := True;
   --  and the initialization code will be portable.

   Abort_Task_Interrupt : Interrupt_ID;
   --  The interrupt that is used to implement task abort if an interrupt is
   --  used for that purpose. This is one of the reserved interrupts.

   Keep_Unmasked : Interrupt_Set := (others => False);
   --  Keep_Unmasked (I) is true iff the interrupt I is one that must be kept
   --  unmasked at all times, except (perhaps) for short critical sections.
   --  This includes interrupts that are mapped to exceptions (see
   --  System.Interrupt_Exceptions.Is_Exception), but may also include
   --  interrupts (e.g. timer) that need to be kept unmasked for other
   --  reasons. Where interrupts are implemented as OS signals, and signal
   --  masking is per-task, the interrupt should be unmasked in ALL TASKS.

   Reserve : Interrupt_Set := (others => False);
   --  Reserve (I) is true iff the interrupt I is one that cannot be permitted
   --  to be attached to a user handler. The possible reasons are many. For
   --  example, it may be mapped to an exception used to implement task abort,
   --  or used to implement time delays.

   procedure Initialize;
   --  Initialize the various variables defined in this package. This procedure
   --  must be called before accessing any object from this package, and can be
   --  called multiple times.

private
   type Interrupt_Mask is new System.OS_Interface.sigset_t;
   --  In some implementations Interrupt_Mask is represented as a linked list

   procedure Adjust_Context_For_Raise
     (Signo    : System.OS_Interface.Signal;
      Ucontext : System.Address);
   pragma Import
     (C, Adjust_Context_For_Raise, "__gnat_adjust_context_for_raise");
   --  Target specific hook performing adjustments to the signal's machine
   --  context, to be called before an exception may be raised from a signal
   --  handler. This service is provided by init.c, together with the
   --  non-tasking signal handler.

end System.Interrupt_Management;