/*********************************************************************** * * @file queue.js * * $Id: queue.js 84 2006-12-15 17:06:03Z tim_j_welch $ * $URL: https://map-fu.svn.sourceforge.net/svnroot/map-fu/trunk/includes/Javascript/queue.js $ * * @project Map-Fu * * This project was developed as part of the Oregon Sustainable * Community Digital Library (OSCDL) by Academic & Research Computing * at Portland State University with support by Oregon State * Library grants 245020, 245021. Special thanks to Rose Jackson and * the OSCDL project. * * @contributors Eric Hanson, Morgan Harvey, Cristopher Holm, * David Percy * * Copyright (c) 2006, Academic & Research Computing, * Portland State University, Portland Oregon. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following * disclaimer in the documentation and/or other materials provided * with the distribution. * * * Neither the names of Academic and Research Computing or Portland * State University nor the names of their contributors may be used * to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. * ***********************************************************************/ /**************************************************************************** * This file contains 2 objects: Queue and QueueItem. QueueItem holds the * state of a given AJAX request that has been queued to run synchronously with * other AJAX requests that may or may not have interdependencies (hence the * need to have them run synchronously). The Queue object manages the requests * and responses on behalf of each QueueItem object. ***************************************************************************/ /**************************************************************************** * QueueItem object * * holds the state of an AJAX request ***************************************************************************/ function QueueItem(name,notifyFunction,url,useXML,timeout) { this.name=name; // a name to identify the request this.state="pending"; // state of the request. possible values are: // pending, working and notifying this.notifyFunction=notifyFunction; // a function to call with the response. // the notify function will always be passed 2 // arguments: status of the request and the response // either a DOM object or text this.url=url; // the url that will process the AJAX request. this // includes the server-side file and any arguments // encoded in a GET string. this.status="OK"; // status of the request. possible values are: // OK, Timeout or an Error message this.processTimestamp=null; // a timestamp of when the request was sent (used // in determining timeout) this.useXML=useXML; // boolean specifying if the request expects an XML // (DOM object) or plain text response this.http_request=null; // the XMLHttpRequest object processing this request this.timeout=timeout; // the time allowed for this request to process // before aborting (in milliseconds) return this; } /**************************************************************************** * Queue object * * manages the activity of all queued requests. ***************************************************************************/ function Queue() { this.items=new Array(); this.timeout=30000; // default timeout of 10 seconds (in milliseconds) // allowed for a queued item to run this.isIE=false; return this; } /**************************************************************************** * init * initializes the state of the Queue object ***************************************************************************/ Queue.prototype.init=function() { if (window.ActiveXObject) this.isIE=true; this.abortAll(); this.items=new Array(); // set the interval at which the queue should be checked for new requests // to process window.setInterval("queue.CheckQueue()",400); } /**************************************************************************** * EnqueueItem * appends a new request onto the list of waiting requests. an optional 5th * argument, if supplied will be assumed to be a timeout value. if not supplied, * the default will be used. ***************************************************************************/ Queue.prototype.EnqueueItem=function(name,notifyFunction,url,useXML) { var timeout=(arguments.length==5)?arguments[4]:this.timeout; var queueItem=new QueueItem(name,notifyFunction,url,useXML,timeout); this.items.push(queueItem); } /**************************************************************************** * CheckQueue * checks the queue for waiting requests that should be aborted (due to * timeout) or new requests that should be started. ***************************************************************************/ Queue.prototype.CheckQueue=function() { if (queue.items.length>0) { var queueItem=queue.items[0]; if (queueItem.state=="pending") { queue.ProcessRequest(); } else if (queueItem.state=="working") { // check the timestamp to see how long its been working var now=new Date(); if (now - queueItem.processTimestamp > queueItem.timeout) { // it's been running for longer than the timeout, so kill it queueItem.http_request.abort(); // remove the item from the queue and notify the user queue.items.shift(); if (queueItem.notifyFunction) { try { queueItem.notifyFunction('Timeout',''); } catch (e) { error.print("Error notifying '"+queueItem.name+"': "+e.message); hideAlert(); } } else { error.print("http request for '"+queueItem.name+"' timed out."); } } } } } /**************************************************************************** * ProcessRequest * creates an XMLHttpRequest object (or the IE equivalent) for a queued * request and sends the request off. ***************************************************************************/ Queue.prototype.ProcessRequest=function() { var queueItem=queue.items[0]; if (window.XMLHttpRequest) { try { queueItem.http_request=new XMLHttpRequest(); } catch (e) { error.print("Error creating XMLHttpRequest object: "+e.message); } } else if (window.ActiveXObject) { try { queueItem.http_request=new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { queueItem.http_request=new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { error.print("Error creating ActiveX http request object: "+e.message); } } } if (queueItem.http_request!=null) { queueItem.http_request.onreadystatechange=queue.RequestHandler; queueItem.http_request.open("GET",queueItem.url,true); queueItem.state="working"; queueItem.processTimestamp=new Date(); try { if (queue.isIE) queueItem.http_request.send(); else queueItem.http_request.send(null); } catch (e) { queueItem.http_request=null; error.print("Error sending http request for '"+queueItem.name+"': "+e.message); } } } /**************************************************************************** * RequestHandler * handles a request's reponse when it has finished. ***************************************************************************/ Queue.prototype.RequestHandler=function() { var queueItem=queue.items[0]; if (queueItem.http_request.readyState == 4) { queueItem.state="notifying"; if (queueItem.http_request.status == 200) { queueItem.status="OK"; } else { queueItem.status="Error. Status code: "+queueItem.http_request.status+"; message: "+queueItem.http_request.statusText; } if (queueItem.notifyFunction) { var tryNotification=true; var response=""; if (queueItem.useXML) { if (queueItem.http_request.responseXML) { response=queueItem.http_request.responseXML; } else { error.print("Error notifying '"+queueItem.name+"': invalid responseXML.\n"+ "Please check the files relating to the url for errors:\n"+queueItem.url); tryNotification=false; } } else { if (queueItem.http_request.responseText) { response=queueItem.http_request.responseText; } else { error.print("Error notifying '"+queueItem.name+"': invalid responseText.\n"+ "Please check the files relating to the url for errors:\n"+queueItem.url); tryNotification=false; } } if (tryNotification) { try { queueItem.notifyFunction(queueItem.status,response); } catch (e) { error.print("Error notifying '"+queueItem.name+"': "+e.message); hideAlert(); } } } queueItem.http_request=null; queueItem=null; queue.items.shift(); } } /**************************************************************************** * abortAll * aborts all pending AJAX requests. this should only be the first one in the * queue (because that's how a queue is supposed to work), but all are queued * requests checked for completeness. ***************************************************************************/ Queue.prototype.abortAll=function() { for (var i=0;i