The script overwrites document.write in order to serialize all rendering

The first version of openx.js had sometimes freezed the IE 8. The cause of
this probably was a race-condition while moving the nodes with the banner
to their final destination.

Because of that, the script serializes all modifications of the DOM
strictly now. Implementation-Details:
 * The HTML delivered by OpenX is parsed, in order to detect included
   script-tags.
 * HTML-code is written to the destination-node directly.
 * script-tags, that load additional code are loaded via a script-node,
   that is appended to the end of the page. The script waits, until the
   additional code is loaded, by adding an onload-event to the appended
   script-node.
 * script-tags with inline-code are executed directly via eval().
 * Calls to document.write() in the additional scripts are catched. To
   achieve that, openx.js overwrites document.write with its own
   implementation, that simply adds the code to an execution-queue, that
   is processed, when the onload-event fires or when the eval()-call
   returns.

TODO:
 * Not tested with IE!

diff --git a/openx.js b/openx.js
index 68cc431..b916e78 100644 (file)
--- a/openx.js
+++ b/openx.js
@@ -4,18 +4,31 @@
 
 (function( openx, $, undefined ) {
 
+  var body = document.getElementsByTagName('body')[0];
+
+  var id;
+  var node;
+
   var count = 0;
   var slots = {};
-  var ads = new Array();
+  var ads = [];
+
+
+  openx.show_ads = function(server, zones) {
 
+    document.write = render;
+    document.writeln = render;
 
-  openx.fetch_ads = function(server, zones) {
+    var domain = document.location.protocol == 'https:' ? 'https://' + server + ':8443':'http://' + server;
 
-    var spc;
+    var spc = document.createElement('script');
 
-    spc  = "<script type='text/javascript' src='";
-    spc += location.protocol == 'https:' ? 'https://' + server + ':8443':'http://' + server;
-    spc += "/www/delivery/spc.php?zones=";
+    spc.type = 'text/javascript';
+    spc.async = false;
+    spc.defer = false;
+
+    spc.src = domain;
+    spc.src += "/www/delivery/spc.php?zones=";
 
     /** Only fetch banners, that are really included in this page */
     $('.oa').each(function() {
@@ -24,48 +37,120 @@
         if (node.hasClass(name)) {
           var id = 'oa_' + ++count;
           slots[id] = node;
-          spc += escape(id + '=' + zones[name] + "|");
+          spc.src += escape(id + '=' + zones[name] + "|");
         }
       }
     });
 
-    spc += "&amp;nz=1&amp;source=" + escape(OA_source);
-    spc += "&amp;r=" + Math.floor(Math.random()*99999999);
-    spc += "&amp;block=1&amp;charset=UTF-8";
+    spc.src += "&nz=1&source=" + escape(OA_source);
+    spc.src += "&r=" + Math.floor(Math.random()*99999999);
+    spc.src += "&block=1&charset=UTF-8";
 
-    if (window.location)   spc += "&amp;loc=" + escape(window.location);
-    if (document.referrer) spc += "&amp;referer=" + escape(document.referrer);
+    if (window.location)   spc.src += "&loc=" + escape(window.location);
+    if (document.referrer) spc.src += "&referer=" + escape(document.referrer);
 
-    spc+="'></script>";
+    spc.onload = init_ads;
+
+    body.appendChild(spc);
 
-    document.write(spc);
-    document.write("<script type='text/javascript' src='http://" + server + "/www/delivery/fl.js'></script>");
-  }
 
+    var fl = document.createElement('script');
 
-  openx.render_ads = function() {
+    fl.type = 'text/javascript';
+    fl.async = false;
+    fl.defer = false;
+
+    fl.src = domain + '/www/delivery/fl.js';
+
+    body.appendChild(fl);
+
+  }
+
+  function init_ads() {
 
-    /** Render the fetched ad-banners... */
     for (var id in slots) {
-      // alert(id + ": " + OA_output[id]);
-      if (typeof(OA_output[id]) != 'undefined' && OA_output[id] != '') {
-        document.write("<div id='" + id + "'>");
-        document.write(OA_output[id]);
-        document.write("</div>");
+      if (typeof(OA_output[id]) != 'undefined' && OA_output[id] != '')
         ads.push(id);
-        // alert('Banner ' + id + ': ' + OA_output[id]);
-      }
     }
 
+    render_ad();
+
   }
 
-  openx.show_ads = function() {
+  function render_ad() {
 
-    /** Show the rendered banners */
-    for (var i=0; i<ads.length; i++) {
-      var ad = $('#'+ads[i]).detach();
-      slots[ads[i]].append(ad);
+    if (ads.length == 0) {
+      id = undefined;
+      node = undefined;
+      return;
     }
+
+    id = ads.pop();
+    node = slots[id];
+
+    // node.append(id + ": " + node.attr('class'));
+
+    var result;
+    var script;
+    var src;
+    var inline;
+
+    while ((result = /<script/i.exec(OA_output[id])) != null) {
+      node.append(OA_output[id].slice(0,result.index));
+      /** Strip all text before "<script" from OA_output[id] */
+      OA_output[id] = OA_output[id].slice(result.index,OA_output[id].length);
+      result = /^([^>]*)>([\s\S]*?)<\\?\/script>/i.exec(OA_output[id]);
+      if (result == null) {
+        /** Invalid syntax in delivered banner-code: ignoring the rest of this banner-code! */
+        // alert(OA_output[id]);
+        OA_output[id] = "";
+        render_ad();
+        return;
+      }
+      /** Remember iinline-code, if present */
+      src = result[1]
+      inline = result[2];
+      /** Strip all text up to and including "</script>" from OA_output[id] */
+      OA_output[id] = OA_output[id].slice(result[0].length,OA_output[id].length);
+      result = /src\s*=\s*['"]([^'"]*)['"]/i.exec(src);
+      if (result == null) {
+        /** script-tag with inline-code: execute inline-code! */
+        eval(inline);
+      }
+      else {
+        /** script-tag with src-URL! */
+        script = document.createElement('script');
+        script.type = 'text/javascript';
+        script.async = false;
+        script.defer = false;
+        script.src = result[1];
+        script.onload = render_ad;
+        /** The banner might not be rendered fully, or include more calls to document.write(). */
+        ads.push(id);
+        /** Load the script and halt all work until the script is loaded and executed... */
+        body.appendChild(script); // << The onload-event is only fired when appendChild is used!
+        return;
+      }
+    }
+    node.append(OA_output[id]);
+    OA_output[id] = "";
+
+    /** This statement will only reached, when no script-element was rendered! */
+    render_ad();
+
+  }
+
+  function render() {
+
+    if (id == undefined)
+      return;
+
+    var str = "";
+    for (var i=0; i < arguments.length; i++)
+      str += arguments[i];
+
+    OA_output[id] = str + OA_output[id];
+
   }
 
 } ( window.openx = window.openx || {}, jQuery ));