gm2-libs-iso/COROUTINES

DEFINITION MODULE COROUTINES;

(* Facilities for coroutines and the handling of interrupts *)

IMPORT SYSTEM ;

CONST
UnassignedPriority  (const)
  UnassignedPriority = 0 ;

TYPE
COROUTINE (type)
  COROUTINE ; (* Values of this type are created dynamically by NEWCOROUTINE
                 and identify the coroutine in subsequent operations *)
INTERRUPTSOURCE (type)
  INTERRUPTSOURCE = CARDINAL ;
PROTECTION (type)
  PROTECTION = [UnassignedPriority..7] ;

NEWCOROUTINE
PROCEDURE NEWCOROUTINE (procBody: PROC;
                        workspace: SYSTEM.ADDRESS;
                        size: CARDINAL;
                        VAR cr: COROUTINE;
                        [initProtection: PROTECTION = UnassignedPriority]);
  (* Creates a new coroutine whose body is given by procBody, and
     returns the identity of the coroutine in cr. workspace is a
     pointer to the work space allocated to the coroutine; size
     specifies the size of this workspace in terms of SYSTEM.LOC.

     The optarg, initProtection, may contain a single parameter which
     specifies the initial protection level of the coroutine.
  *)

TRANSFER
PROCEDURE TRANSFER (VAR from: COROUTINE; to: COROUTINE);
  (* Returns the identity of the calling coroutine in from, and
     transfers control to the coroutine specified by to.
  *)

IOTRANSFER
PROCEDURE IOTRANSFER (VAR from: COROUTINE; to: COROUTINE);
  (* Returns the identity of the calling coroutine in from and
     transfers control to the coroutine specified by to.  On
     occurrence of an interrupt, associated with the caller, control
     is transferred back to the caller, and the identity of the
     interrupted coroutine is returned in from.  The calling coroutine
     must be associated with a source of interrupts.
  *)

ATTACH
PROCEDURE ATTACH (source: INTERRUPTSOURCE);
  (* Associates the specified source of interrupts with the calling
     coroutine. *)

DETACH
PROCEDURE DETACH (source: INTERRUPTSOURCE);
  (* Dissociates the specified source of interrupts from the calling
     coroutine. *)

IsATTACHED
PROCEDURE IsATTACHED (source: INTERRUPTSOURCE): BOOLEAN;
  (* Returns TRUE if and only if the specified source of interrupts is
     currently associated with a coroutine; otherwise returns FALSE.
  *)

HANDLER
PROCEDURE HANDLER (source: INTERRUPTSOURCE): COROUTINE;
  (* Returns the coroutine, if any, that is associated with the source
     of interrupts. The result is undefined if IsATTACHED(source) =
     FALSE.
  *)

CURRENT
PROCEDURE CURRENT (): COROUTINE;
  (* Returns the identity of the calling coroutine. *)

LISTEN
PROCEDURE LISTEN (p: PROTECTION);
  (* Momentarily changes the protection of the calling coroutine to
     p. *)

PROT
PROCEDURE PROT (): PROTECTION;
  (* Returns the protection of the calling coroutine. *)

(*
   TurnInterrupts - switches processor interrupts to the protection
                    level, to.  It returns the old value.
*)

TurnInterrupts
PROCEDURE TurnInterrupts (to: PROTECTION) : PROTECTION ;

(*
   ListenLoop - should be called instead of users writing:

                LOOP
                   LISTEN
                END

                It performs the same function but yields
                control back to the underlying operating system.
                It also checks for deadlock.
                Note that this function does return when an interrupt occurs.
                (File descriptor becomes ready or time event expires).
*)

ListenLoop
PROCEDURE ListenLoop ;

END COROUTINES.