User Guide

98 Application Development Tips and Tricks

Simple-system call example

The following simple-system call example implements an ID generator. The generator must

generate an increasing number for each new ID. If you write the generator code in the

main.asc file, any part of the script could easily redefine the

nextID() function or directly

modify the

_nextID value, as in the following:

idGen = {};

idGen._nextID = 0;

idGen.nextID = function() {return this._nextID++;}

If you move the generator code to the secure.asc file, it loads before the main.asc file and isn’t

accessible by code in the main.asc file. The following is the secure.asc file:

// Begin secure.asc.

trace("loading secure.asc");

var global = getGlobal(); // Grab the global object.

var idgen = {};

idgen._nextID = 0;

idgen.nextID = function() {return this._nextID++;}

// Create a protected object out of idgen and make it

// available globally as idGen.

global.idGen = protectObject(idgen);

// Make idGen non-enumerable, read-only, and permanent.

setAttributes(global, "idGen", false, true, true);

The following is the main.asc file that attempts to access the idGen variable that was protected

in the secure.asc file:

// main.asc

trace("Loading main.asc");

trace("idGen = " + idGen);

idGen = 50;

trace("idGen = " + idGen);

The following is the output from both files:

Loading secure.asc

Loading main.asc

idGen = [object Redirector]

Synchronous system calls

A synchronous call performs its action completely by the time the call returns. A synchronous

system call is a synchronous call that is protected and routed through a system object.