js/util/ExponentialReExpressClosure.js

/**
 * @author: Jeff Thompson
 * See COPYING for copyright and distribution information.
 * This is the closure class for use in expressInterest to re express with exponential falloff.
 */

/**
 * Create a new ExponentialReExpressClosure where upcall responds to UPCALL_INTEREST_TIMED_OUT
 *   by expressing the interest again with double the interestLifetime. If the interesLifetime goes
 *   over maxInterestLifetime, then call callerClosure.upcall with UPCALL_INTEREST_TIMED_OUT.
 * When upcall is not UPCALL_INTEREST_TIMED_OUT, just call callerClosure.upcall.
 * @constructor
 * @param {Closure} callerClosure
 * @param {Object} settings if not null, an associative array with the following defaults:
 * {
 *   maxInterestLifetime: 16000 // milliseconds
 * }
 */
var ExponentialReExpressClosure = function ExponentialReExpressClosure
        (callerClosure, settings) {
    // Inherit from Closure.
    Closure.call(this);
    
    this.callerClosure = callerClosure;
    settings = (settings || {});
	this.maxInterestLifetime = (settings.maxInterestLifetime || 16000);
};

/**
 * Wrap this.callerClosure to responds to UPCALL_INTEREST_TIMED_OUT
 *   by expressing the interest again as described in the constructor.
 */
ExponentialReExpressClosure.prototype.upcall = function(kind, upcallInfo) {
    try {
        if (kind == Closure.UPCALL_INTEREST_TIMED_OUT) {
            var interestLifetime = upcallInfo.interest.interestLifetime;
            if (interestLifetime == null)
                return this.callerClosure.upcall(Closure.UPCALL_INTEREST_TIMED_OUT, upcallInfo);
            
            var nextInterestLifetime = interestLifetime * 2;
            if (nextInterestLifetime > this.maxInterestLifetime)
                return this.callerClosure.upcall(Closure.UPCALL_INTEREST_TIMED_OUT, upcallInfo);
            
            var nextInterest = upcallInfo.interest.clone();
            nextInterest.interestLifetime = nextInterestLifetime;
            upcallInfo.ndn.expressInterest(nextInterest.name, this, nextInterest);
            return Closure.RESULT_OK;
        }  
        else
            return this.callerClosure.upcall(kind, upcallInfo);
    } catch (ex) {
        console.log("ExponentialReExpressClosure.upcall exception: " + ex);
        return Closure.RESULT_ERR;
    }
};