storage1.def

DEFINITION MODULE Storage1;

	(********************************************************)
	(*							*)
	(*  Storage allocation with critical section protection	*)
	(*							*)
	(*  Programmer:		P. Moylan			*)
	(*  Last edited:	26 February 1995		*)
	(*  Status:		OK				*)
	(*							*)
	(********************************************************)

(************************************************************************)
(*  This module supports the Modula-2 NEW and DISPOSE operations.	*)
(*									*)
(*  Why should you use this module, when the standard module Storage	*)
(*  already provides the necessary facilities?  The answer is that	*)
(*  most "normal" implementations of Storage don't provide critical	*)
(*  section protection.  Some very nasty things can happen if there's	*)
(*  a task switch in the middle of heap manipulation; and the fault	*)
(*  is typically non-repeatable and hard to track down.			*)
(*									*)
(*  In the case of TopSpeed Modula-2 the MThread memory model takes	*)
(*  care of this; but you might not want that solution, for two reasons:*)
(*	1. It removes the possibility of using PMOS under the more	*)
(*	   economical memory models.					*)
(*	2. The TopSpeed solution is to disable interrupts, which could	*)
(*	   be unacceptable in real-time applications.  The solution	*)
(*	   adopted in the present model is better in terms of		*)
(*	   interrupt latency.						*)
(*									*)
(************************************************************************)

PROCEDURE ALLOCATE (VAR (*OUT*) p: ADDRESS;  size: CARDINAL);

    (* Allocates a block of size bytes. *)

PROCEDURE DEALLOCATE (VAR (*INOUT*) p: ADDRESS;  size: CARDINAL);

    (* Deallocates memory that was allocated by ALLOCATE. *)

END Storage1.