(* interrupts.sig *)

(* Copyright (C) 2007 Alley Stoughton

   This file is part of crypto, a cryptogram encoder/decoder.  See the
   file COPYING.txt for copying and usage restrictions *)

(* interrupt handling *)

signature INTERRUPTS =
sig

(* ignore f saves the current handling action for interrupts (the
   default action is termination), begins ignoring interrupts, and then
   evaluates f()

   if this evaluation yields the value v, then ignore restores the saved
   action for interrupts, and then returns v

   if this evaluation raises the exception ex, then ignore restores the
   saved action for interrupts, and then raises ex

   f() should not do any explicit interrupt processing, and should
   not call ignore *)

val ignore : (unit -> 'a) -> 'a

(* track f evaluates f() while keeping track of interrupts

   if this evaluation yields the value v, then track clears the
   interrupt signaling record, and then returns v

   if this evaluation raises the exception ex, then track clears the
   interrupt signaling record, and then raises ex

   f() should not do any explicit interrupt processing, and should
   not call ignore or track

   any input/output operations performed by f() should be done in
   protected mode (see the function protect, below) *)

val track : (unit -> 'a) -> 'a

(* protect f evaluates f() in PROTECTED MODE (also see track, above)

   f() should not do any interrupt processing either directly
   or using any of these functions *)

val protect : (unit -> 'a) -> 'a

(* check() checks whether any interrupts have been signaled, returning
   true (and clearing the interrupt signaling record) if the answer is yes,
   and returning false, otherwise *)

val check : unit -> bool

end;