(*
 * Copyright 1987, 1989 Samuel H. Smith;  All rights reserved
 *
 * This is a component of the ProDoor System.
 * Do not distribute modified versions without my permission.
 * Do not remove or alter this notice or any other copyright notice.
 * If you use this in your own program you must distribute source code.
 * Do not use any of this in a commercial product.
 *
 *)

type
   longlink = record
      ofs:  integer;
      seg:  integer;
   end;

procedure DISABLE_INT;
   inline($FA);
   (* disable further processor interrupts *)

procedure ENABLE_INT;
   inline($FB);
   (* enable processor interrupts *)

procedure ENTER_INTERRUPT;
   (* prologue for interrupt handlers *)
   inline($90);

procedure LINK_CALL(vec: longlink);
   (* call the old handler through the *)      
   (* specified link variable *)               
   inline($2E/$FF/$1E{/>vec});       (* call far cs:oldvec *)

procedure LINK_JMP(vec: longlink);
   (* epilogue for interrupt handlers *)       
   (* jumping to the old handler through *)    
   (* the specified link variable *)           
   inline($1F/          (* pop ds *)           
          $07/          (* pop es *)           
          $5E/          (* pop si *)           
          $5F/          (* pop di *)           
          $5A/          (* pop dx *)           
          $59/          (* pop cx *)           
          $5B/          (* pop bx *)           
          $58/          (* pop ax *)           
          $89/$EC/      (* mov sp,bp *)        
          $5D/          (* pop bp *)           
          $2E/$FF/$2E{/>vec});     (* jmp far cs:oldvec *)

procedure EXIT_INTERRUPT;
   (* epilogue for interrupt handlers *)       
   (* does not call old handler at all *)      
   inline($90);

procedure get_handler(vector:      integer;     {vector number}
                      var link:    longlink);   {cseg link to old handler}

   (* get a pointer to the current handler for an interrupt vector *)

procedure attach_handler(vector:      integer;     {vector number}
                         handler:     integer;     {cseg ofs of new handler}
                         var link:    longlink);   {cseg link to old handler}

   (* attach an interrupt handler to the specified vector number;
      handler is the cseg offset of the new handler; link will
      contain a long pointer to the previous handler *)

procedure remove_handler(vector:      integer;     {vector number}
                         var link:    longlink);   {cseg link to old handler}

   (* remove an interrupt handler and replace the old handler *)