------------------------------------------------------------------------------
--                                                                          --
--                GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS               --
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--                     S Y S T E M . I N T E R R U P T S                    --
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--          Copyright (C) 1992-2001 Free Software Foundation, Inc.          --
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------------------------------------------------------------------------------

--  Note: the compiler generates direct calls to this interface, via Rtsfind.
--  Any changes to this interface may require corresponding compiler changes.

--  This package encapsulates the implementation of interrupt or signal
--  handlers.  It is logically an extension of the body of Ada.Interrupts.
--  It is made a child of System to allow visibility of various
--  runtime system internal data and operations.

--  See System.Interrupt_Management for core interrupt/signal interfaces.

--  These two packages are separated in order to allow
--  System.Interrupt_Management to be used without requiring the whole
--  tasking implementation to be linked and elaborated.

with System.Tasking;
--  used for Task_ID

with System.Tasking.Protected_Objects.Entries;
--  used for Protection_Entries

with System.OS_Interface;
--  used for Max_Interrupt

package System.Interrupts is

   pragma Elaborate_Body;
   --  Comment needed on why this is here ???

   -------------------------
   -- Constants and types --
   -------------------------

   Default_Interrupt_Priority : constant System.Interrupt_Priority :=
     System.Interrupt_Priority'Last;
   --  Default value used when a pragma Interrupt_Handler or Attach_Handler is
   --  specified without an Interrupt_Priority pragma, see D.3(10).

   type Ada_Interrupt_ID is range 0 .. System.OS_Interface.Max_Interrupt;
   --  Avoid inheritance by Ada.Interrupts.Interrupt_ID of unwanted operations

   type Interrupt_ID is range 0 .. System.OS_Interface.Max_Interrupt;

   type Parameterless_Handler is access protected procedure;

   ----------------------
   -- General services --
   ----------------------

   --  Attempt to attach a Handler to an Interrupt to which an Entry is
   --  already bound will raise a Program_Error.

   function Is_Reserved (Interrupt : Interrupt_ID) return Boolean;

   function Is_Entry_Attached (Interrupt : Interrupt_ID) return Boolean;

   function Is_Handler_Attached (Interrupt : Interrupt_ID) return Boolean;

   function Current_Handler
     (Interrupt : Interrupt_ID)
      return Parameterless_Handler;

   --  Calling the following procedures with New_Handler = null
   --  and Static = true means that we want to modify the current handler
   --  regardless of the previous handler's binding status.
   --  (i.e. we do not care whether it is a dynamic or static handler)

   procedure Attach_Handler
     (New_Handler : Parameterless_Handler;
      Interrupt   : Interrupt_ID;
      Static      : Boolean := False);

   procedure Exchange_Handler
     (Old_Handler : out Parameterless_Handler;
      New_Handler : Parameterless_Handler;
      Interrupt   : Interrupt_ID;
      Static      : Boolean := False);

   procedure Detach_Handler
     (Interrupt : Interrupt_ID;
      Static    : Boolean := False);

   function Reference
     (Interrupt : Interrupt_ID)
     return       System.Address;

   ---------------------------------
   --  Interrupt entries services --
   ---------------------------------

   --  Routines needed for Interrupt Entries
   --  Attempt to bind an Entry to an Interrupt to which a Handler is
   --  already attached will raise a Program_Error.

   procedure Bind_Interrupt_To_Entry
     (T       : System.Tasking.Task_ID;
      E       : System.Tasking.Task_Entry_Index;
      Int_Ref : System.Address);

   procedure Detach_Interrupt_Entries (T : System.Tasking.Task_ID);
   --  This procedure detaches all the Interrupt Entries bound to a task.

   -------------------------------
   --  POSIX.5 signals services --
   -------------------------------

   --  Routines needed for POSIX dot5 POSIX_Signals

   procedure Block_Interrupt (Interrupt : Interrupt_ID);
   --  Block the Interrupt on the process level

   procedure Unblock_Interrupt (Interrupt : Interrupt_ID);

   function Unblocked_By
     (Interrupt   : Interrupt_ID)
      return System.Tasking.Task_ID;
   --  It returns the ID of the last Task which Unblocked this Interrupt.
   --  It returns Null_Task if no tasks have ever requested the
   --  Unblocking operation or the Interrupt is currently Blocked.

   function Is_Blocked (Interrupt : Interrupt_ID) return Boolean;
   --  Comment needed ???

   procedure Ignore_Interrupt (Interrupt : Interrupt_ID);
   --  Set the sigacion for the interrupt to SIG_IGN.

   procedure Unignore_Interrupt (Interrupt : Interrupt_ID);
   --  Comment needed ???

   function Is_Ignored (Interrupt : Interrupt_ID) return Boolean;
   --  Comment needed ???

   --  Note : Direct calls to sigaction, sigprocmask, thr_sigsetmask or any
   --  other low-level interface that changes the signal action or signal mask
   --  needs a careful thought.

   --  One may acheive the effect of system calls first making RTS blocked
   --  (by calling Block_Interrupt) for the signal under consideration.
   --  This will make all the tasks in RTS blocked for the Interrupt.

   ----------------------
   -- Protection types --
   ----------------------

   --  Routines and types needed to implement Interrupt_Handler and
   --  Attach_Handler.

   --  There are two kinds of protected objects that deal with interrupts:

   --  (1) Only Interrupt_Handler pragmas are used. We need to be able to
   --  tell if an Interrupt_Handler applies to a given procedure, so
   --  Register_Interrupt_Handler has to be called for all the potential
   --  handlers, it should be done by calling Register_Interrupt_Handler
   --  with the handler code address. On finalization, which can happen only
   --  has part of library level finalization since PO with
   --  Interrupt_Handler pragmas can only be declared at library level,
   --  nothing special needs to be done since the default handlers have been
   --  restored as part of task completion which is done just before global
   --  finalization.  Dynamic_Interrupt_Protection should be used in this
   --  case.

   --  (2) Attach_Handler pragmas are used, and possibly Interrupt_Handler
   --  pragma. We need to attach the handlers to the given interrupts when
   --  the objet is elaborated. This should be done by constructing an array
   --  of pairs (interrupt, handler) from the pragmas and calling
   --  Install_Handlers with it (types to be used are New_Handler_Item and
   --  New_Handler_Array). On finalization, we need to restore the handlers
   --  that were installed before the elaboration of the PO, so we need to
   --  store these previous handlers. This is also done by Install_Handlers,
   --  the room for these informations is provided by adding a discriminant
   --  which is the number of Attach_Handler pragmas and an array of this
   --  size in the protection type, Static_Interrupt_Protection.

   procedure Register_Interrupt_Handler
     (Handler_Addr : System.Address);
   --  This routine should be called by the compiler to allow the
   --  handler be used as an Interrupt Handler. That means call this
   --  procedure for each pragma Interrup_Handler providing the
   --  address of the handler (not including the pointer to the
   --  actual PO, this way this routine is called only once for
   --  each type definition of PO).

   type Static_Handler_Index is range 0 .. Integer'Last;
   subtype Positive_Static_Handler_Index is
     Static_Handler_Index range 1 .. Static_Handler_Index'Last;
   --  Comment needed ???

   type Previous_Handler_Item is record
      Interrupt : Interrupt_ID;
      Handler   : Parameterless_Handler;
      Static    : Boolean;
   end record;
   --  Contains all the information needed to restore a previous handler.

   type Previous_Handler_Array is array
     (Positive_Static_Handler_Index range <>) of Previous_Handler_Item;

   type New_Handler_Item is record
      Interrupt : Interrupt_ID;
      Handler   : Parameterless_Handler;
   end record;
   --  Contains all the information from an Attach_Handler pragma.

   type New_Handler_Array is
     array (Positive_Static_Handler_Index range <>) of New_Handler_Item;
   --  Comment needed ???

   --  Case (1)

   type Dynamic_Interrupt_Protection is new
     Tasking.Protected_Objects.Entries.Protection_Entries with null record;

   --  ??? Finalize is not overloaded since we currently have no
   --  way to detach the handlers during library level finalization.

   function Has_Interrupt_Or_Attach_Handler
     (Object : access Dynamic_Interrupt_Protection) return Boolean;
   --  Returns True.

   --  Case (2)

   type Static_Interrupt_Protection
     (Num_Entries        : Tasking.Protected_Objects.Protected_Entry_Index;
      Num_Attach_Handler : Static_Handler_Index)
   is new
     Tasking.Protected_Objects.Entries.Protection_Entries (Num_Entries) with
     record
       Previous_Handlers : Previous_Handler_Array (1 .. Num_Attach_Handler);
     end record;

   function Has_Interrupt_Or_Attach_Handler
     (Object : access Static_Interrupt_Protection)
      return   Boolean;
   --  Returns True.

   procedure Finalize (Object : in out Static_Interrupt_Protection);
   --  Restore previous handlers as required by C.3.1(12) then call
   --  Finalize (Protection).

   procedure Install_Handlers
     (Object       : access Static_Interrupt_Protection;
      New_Handlers : in New_Handler_Array);
   --  Store the old handlers in Object.Previous_Handlers and install
   --  the new static handlers.

end System.Interrupts;
