ndn-js
Version:
A JavaScript client library for Named Data Networking
85 lines (78 loc) • 3.03 kB
JavaScript
/**
* Copyright (C) 2014-2019 Regents of the University of California.
* @author: Jeff Thompson <jefft0@remap.ucla.edu>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
* A copy of the GNU Lesser General Public License is in the file COPYING.
*/
/**
* A ChangeCounter keeps a target object whose change count is tracked by a
* local change count. You can set to a new target which updates the local
* change count, and you can call checkChanged to check if the target (or one of
* the target's targets) has been changed. The target object must have a method
* getChangeCount.
*
* Create a new ChangeCounter to track the given target. If target is not null,
* this sets the local change counter to target.getChangeCount().
* @param {object} target The target to track, as an object with the method
* getChangeCount().
* @constructor
*/
var ChangeCounter = function ChangeCounter(target)
{
this.target = target;
this.changeCount = (target == null ? 0 : target.getChangeCount());
};
exports.ChangeCounter = ChangeCounter;
/**
* Get the target object. If the target is changed, then checkChanged will
* detect it.
* @return {object} The target, as an object with the method
* getChangeCount().
*/
ChangeCounter.prototype.get = function()
{
return this.target;
};
/**
* Set the target to the given target. If target is not null, this sets the
* local change counter to target.getChangeCount().
* @param {object} target The target to track, as an object with the method
* getChangeCount().
*/
ChangeCounter.prototype.set = function(target)
{
this.target = target;
this.changeCount = (target == null ? 0 : target.getChangeCount());
};
/**
* If the target's change count is different than the local change count, then
* update the local change count and return true. Otherwise return false,
* meaning that the target has not changed. Also, if the target is null,
* simply return false. This is useful since the target (or one of the target's
* targets) may be changed and you need to find out.
* @return {boolean} True if the change count has been updated, false if not.
*/
ChangeCounter.prototype.checkChanged = function()
{
if (this.target == null)
return false;
var targetChangeCount = this.target.getChangeCount();
if (this.changeCount != targetChangeCount) {
this.changeCount = targetChangeCount;
return true;
}
else
return false;
};