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------------------------------------------------------------------------------

--                                                                          --

--                 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) 1991-2009, 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.     --

--                                                                          --

------------------------------------------------------------------------------

--  This is the Alpha/VMS version of this package

--  This package encapsulates and centralizes information about all uses of

--  interrupts (or signals), including the target-dependent mapping of

--  interrupts (or signals) to exceptions.

--  PLEASE DO NOT add any with-clauses to this package

--  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 below are

--  implemented as visible arrays rather than functions.)

with System.OS_Interface;

package System.Interrupt_Management is

   pragma Preelaborate;

   type Interrupt_Mask is limited private;

   type Interrupt_ID is new System.OS_Interface.Signal;

   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;

   --  Then 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.

   Keep_Masked : Interrupt_Set := (others => False);

   --  Keep_Masked (I) is true iff the interrupt I must always be masked.

   --  Where interrupts are implemented as OS signals, and signal masking is

   --  per-task, the interrupt should be masked in ALL TASKS. There might not

   --  be any interrupts in this class, depending on the environment. For

   --  example, if interrupts are OS signals and signal masking is per-task,

   --  use of the sigwait operation requires the signal be masked in all tasks.

   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

   use type System.OS_Interface.unsigned_long;

   type Interrupt_Mask is new System.OS_Interface.sigset_t;

   --  Interrupts on VMS are implemented with a mailbox. A QIO read is

   --  registered on the Rcv channel and the interrupt occurs by registering

   --  a QIO write on the Snd channel. The maximum number of pending

   --  interrupts is arbitrarily set at 1000. One nice feature of using

   --  a mailbox is that it is trivially extendable to cross process

   --  interrupts.

   Rcv_Interrupt_Chan : System.OS_Interface.unsigned_short := 0;

   Snd_Interrupt_Chan : System.OS_Interface.unsigned_short := 0;

   Interrupt_Mailbox  : Interrupt_ID := 0;

   Interrupt_Bufquo   : System.OS_Interface.unsigned_long :=

                          1000 * (Interrupt_ID'Size / 8);

end System.Interrupt_Management;