Nginad广告生成代码分析

大家都知道实时竞价的广告一般会在一个iframe中，这个iframe会有一个复杂的src。那么这个iframe是如何生成的？

这里分析NginAd作为exchange时，如何让媒体网站通过引用一段ad tag达到竞价的目的。

当一个媒体网站对接到NginAd，注册完毕后，NginAd会给出一段Ad Tag，将这个Tag加到媒体网站内便会出现一个实时竞价的iframe。给出一个Ad tag的示例：

script type='text/javascript' src='http://server.nginad.com/ad/nginad.js?pzoneid=7&height=400&width=240&tld=www.kliupubdomain.com&cb=1421739738'

这段Ad tag会执行nginad.js脚本，后面的参数附上了广告位的各种参数，那么这段脚本是怎么把广告拉进来的？我们分析下nginad.js的代码。 nginad.js的代码很长，我贴在最后，先讲解下它的执行过程。

1. 参数解析

标准html语法中，script标签是无法带参数的，所以这段tag只会简单的执行nginad.js。nginad.js脚本运行后，第一件事是从网页当前的dom树中找到自己所在的script节点，把参数

pzoneid=7&height=400&width=240&tld=www.kliupubdomain.com&cb=1421739738

解析出来，它的做法是在当前DOM中找到nginad.js所在的< script >元素，通过正则表达式的方式抽出参数字段并解析。

2. iframe创建

接下来，nginad.js解析自己script标签所在位置，如果它不在iframe的根部，就会自己创建一个iframe，并把它添加到dom树上自己的位置之前。

3. iframe src拼接

再接下来就是最关键的iframe src拼接，脚本会解析出当前网页所在url和可能的传递url，当前广告位是否在屏幕显示范围内，当前广告位的位置，大小等等一切信息，然后拼接成一个链接，链接的形式大致是

http://server.nginad.com/delivery?params

这个链接被作为iframe的src，查看nginad的源代码可知，当向这个地址发出http请求时，就相当于发出了一次竞价请求，nginad根据后面的params向所有注册的DPS发出广告竞价请求。最后获胜者给出的adm，也就是物料网址作为返回。因此当加载这个iframe时，用户便会看到最后竞价成功的广告内容。

附　nginad.js 代码

/**

 * CDNPAL NGINAD Project

 *

 * @link http://www.nginad.com

 * @copyright Copyright (c) 2013-2015 CDNPAL Ltd. All Rights Reserved

 * @license GPLv3

 */

var adserver_domain = 'localhost';

var script_name = 'nginad.js';

var delivery_path = '/delivery/impress';

var quality_scoring_pixels = [

	// QS SERVICE 1

	// "http://myqualityscore1.com/server/pixel.htm?uid=user_id",

	// QS SERVICE 2

	// "http://myqualityscore2.com/server/pixel.htm?uid=user_id",

	// QS SERVICE 3

	// "http://myqualityscore3.com/server/pixel.htm?uid=user_id",

];

var cookie_matching_pixels = [

	// ZENOVIA EXCHANGE

	// "http://sync.nj.zenoviaexchange.com/usersync2/partner_id",

	// TURN

	// "http://ad.turn.com/server/pixel.htm?fpid=13&r=12345",

	// MEDIA MATH

	// "http://pixel.mathtag.com/sync/js?sync=auto",

	// DSTILLERY

	// "http://idpix.media6degrees.com/orbserv/hbpix?pixId=1",

	// CHANGO

	// "http://lj.d.chango.com/m/lj?r=12345",

	// RFI HUB

	// "http://p.rfihub.com/cm?in=1&pub=1",

	// APPNEXUS

	// "http://ib.adnxs.com/getuid?http://mydomain.com/merge?pid=12&3pid=$UID",

	// RTB BIDDER

	// "http://match.rtbidder.net/match?p=31&ord=12345",

	// SITE SCOUT

	// "http://pixel.sitescout.com/dmp/pixelSync?network=partner_id",

	// CASALE MEDIA

	// "http://ip.casalemedia.com/usermatch?s=178636&cb=http%3A%2F%2Fmydomain.com%2Fmerge%3Fpid%3D18%263pid%3D",

	// IPONWEB:

	// "http://x.bidswitch.net/sync?ssp=fmx",

	// TRADE DESK

	// "http://data.adsrvr.org/track/cmf/generic?ttd_pid=partner_id",

	// RUBICON PROJECT

	// "http://pixel.rubiconproject.com/tap.php?v=other&nid=partner_id&put={user_token}&expires={days}",

	// AUDIENCE SCIENCE

	// "http://pix04.revsci.net/D08734/a3/0/3/0.302?matchId=100&PV=0"

];

function createTrackingPixel(url) {

	(new Image()).src = url;

}

function fireCookieMatchingPixels() {

	for (i in cookie_matching_pixels) {

		createTrackingPixel(cookie_matching_pixels[i]);

	}

}

function fireQSPixels() {

	for (i in quality_scoring_pixels) {

		createTrackingPixel(quality_scoring_pixels[i]);

	}

}

if (typeof NGIN_AdsiFrame_Opts === "undefined") {

	var NGIN_AdsiFrame_Opts = null;

}

if (typeof NGIN_placement_id === "undefined") {

	var NGIN_placement_id = null;

}

var NGIN_AdsiFrame=(function() {

  function isInIframe() {

	  return self !== top;

  }

  function getScriptTag() {

	  if('currentScript' in document) {

		  return document.currentScript;

	  }

	  var scripts = document.getElementsByTagName('script');

	  var last_script = scripts[scripts.length-1];

	  var rg = new RegExp(script_name, 'i');

	  if(last_script.src.search(rg) >= 0) {

		  return last_script;

	  } else {

		  try{

			  for(var n = scripts.length-1; n >= 0; n--) {

				  if(scripts[n].src.search(rg) >= 0) {

					  return scripts[n];

				  }

			  }

		  }catch(e) {

		  }

	  }

	  return last_script;

  }

  function getQueryString() {

    var myScript=getScriptTag();

    var rg = new RegExp(script_name, 'i');

    if(myScript.src.search(rg) >= 0) {

    	return myScript.src.replace(/^[^\?]+\??/,'');

    } else {

    	return false;

    }

  }

  function getQueryStringArg(qs, key, default_) {

    default_ = default_||'';

    var query_obj = {};

    qs.replace( new RegExp("([^?=&]+)(=([^&]*))?","g"), function($0,$1,$2,$3) { query_obj[$1] = $3; } );

    if(typeof(query_obj[key]) === 'undefined' || query_obj[key] === null) {

    	return default_;

    } else {

    	return query_obj[key];

    }

  }

  function getSiteURL() {

    var site_loc='';

    try{

    	if(isInIframe() && document.referrer) {

    		site_loc = document.referrer.replace(/^\s+|\s+$/g,'');

    	} else {

    		site_loc = document.location.href;

    	}

    } catch(e) {

    }

    return site_loc.replace(/["']/g,'');

  }

  function getRefSiteURL() {

    var ref='';

    if(!isInIframe()) {

    	ref=document.referrer.replace(/^\s+|\s+$|["']/g,'');

    }

    return ref;

  }

  function getOD() {

	  return parseUri(document.location.href.replace(/["']/g,'')).host;

  }

  function getNGINZoneId(zoneid) {

    var id = 'NGIN_' + zoneid;

    var obj = document.getElementById(id);

    if(!obj) {

    	return id;

    }

    var i = 1;

    while(obj) {

    	id = 'NGIN_' + zoneid + '_' + i;

    	obj = document.getElementById(id);

    	i++;

    }

    return id;

  }

  function getNGINAtf(id, viewport){

	  var ret="";

	  if(!viewport || viewport.status != "ok") {

		  ret="error";

	  }

	  try {

		  var rect = getNGINPosition(id);

		  ret = ((rect.x+rect.width <= viewport.x + viewport.width) && (rect.y + rect.height <= viewport.y + viewport.height));

	  } catch(e) { 

		  ret="error";

	  }

	  return ret == true ? 1 : 0;

  }

  function getNGINPosition(id, width, height) {

    var w = (width) ? width : 0;

    var h = (height) ? height : 0;

    var y = 0;

    var x = 0;

    var rect = { x:x, y:y, width:w, height:h };

    var de = document.documentElement;

    try {

      var obj = document.getElementById(id);

      while (obj) {

    	  rect.x += obj.offsetLeft;

    	  rect.y += obj.offsetTop;

    	  obj = obj.offsetParent;

      }

      if(self.pageYOffset) {

    	  rect.x -= self.pageXOffset;

    	  rect.y -= self.pageYOffset;

      } else if (de && de.scrollTop) {

    	  rect.x -= de.scrollLeft;

    	  rect.y -= de.scrollTop;

      } else if (document.body) {

    	  rect.x -= document.body.scrollLeft;

    	  rect.y -= document.body.scrollTop;

      }

    } catch(e){

    }

    return rect;

  }

function getNGINViewport() {

	  var viewport = {x:0,y:0,width:0,height:0,status:''}

	  var bw = 0;

	  var bh = 0;

	  var de = de;

	  var w = window;

	  var db = document.body;

    try {

    	if (typeof w.innerWidth==='number') {

    		bw=w.innerWidth;

    		bh=w.innerHeight;

    	} else if(de && (de.clientWidth || de.clientHeight)) {

    		bw = de.clientWidth;

    		bh = de.clientHeight;

    	} else if (db && (db.clientWidth || db.clientHeight)) {

    		bw = db.clientWidth;

    		bh = db.clientHeight;

    	} else if (de && (de.offsetWidth || de.offsetHeight)) {

    		bw = de.offsetWidth;

    		bh = de.offsetHeight;

    	}

    	viewport.status = "ok";

    	viewport.width = bw;

    	viewport.height = bh;

    } catch(e){

    	viewport.status="error";

    }

    return viewport;

  }

function parseUri(u) {

    try{

    	var o = {

    			key:["source","protocol","authority","userInfo","user","password","host","port","relative","path","directory","file","query","anchor"],

    			q:{name:"queryKey", parser:/(?:^|&)([^&=]*)=?([^&]*)/g},

    			parser:{loose:/^(?:(?![^:@]+:[^:@\/]*@)([^:\/?#.]+):)?(?:\/\/)?((?:(([^:@]*)(?::([^:@]*))?)?@)?([^:\/?#]*)(?::(\d*))?)(((\/(?:[^?#](?![^?#\/]*\.[^?#\/.]+(?:[?#]|$)))*\/?)?([^?#\/]*))(?:\?([^#]*))?(?:#(.*))?)/}

    	};

    	var m = o.parser.loose.exec(u);

    	var uri={};

    	var i = 14;

    	while(i--) {

    		uri[o.key[i]] = m[i] || '';

    	}

    	uri[o.q.name] = {};

    	uri[o.key[12]].replace(o.q.parser, function($0,$1,$2){ if($1) uri[o.q.name][$1]=$2; } );

    	return uri;

    } catch(e) {

    	this.reportError('Failed to get OD',e);

    }

    return u;

  }

function getNGINQueryString(id, qs, atf, add_all_tokens) {

	  var qstring = '?atf=' + atf;

	  var viewport = getNGINViewport();

	  if(viewport && viewport.status == "ok") {

		  qstring += '&scres_height=' + viewport.height;

		  qstring += '&scres_width=' + viewport.width;

	  }

	  var adPosition = getNGINPosition(id);

	  if(adPosition) {

		  qstring += '&adpos_x=' + adPosition.x;

		  qstring += '&adpos_y=' + adPosition.y;

	  }

	  var e = encodeURIComponent;

	  if (add_all_tokens) {

		  qstring += '&loc=' + e(getSiteURL()) + '&od=' + e(getOD()) + '&ref=' + e(getRefSiteURL());

	  }

	  var args = qs.split('&');

	  for (var i = 0; i < args.length; i++) {

		  var arg = args[i].split('=')

		  var key = arg[0]

		  var value = arg[1];

		  if (key === 'debug'

			  || key === 'u'

			  || key === 'zoneid'

			  || key === 'pzoneid'

			  || key === 'n'

			  || key === 'NGIN_domain'

			  || key.match(/^NGIN_/)

			) {

			  qstring += '&' + e(key) + "=" + e(value);

		  }

	  }

	  return qstring;

}

function createiFrame(id, width, height) {

	  var ifrm = document.createElement('iframe');

	  ifrm.setAttribute('id',id);

	  ifrm.setAttribute('margin','0');

	  ifrm.setAttribute('padding','0');

	  ifrm.setAttribute('frameBorder','0');

	  ifrm.setAttribute('width',width+'');

	  ifrm.setAttribute('height',height+'');

	  ifrm.setAttribute('scrolling','no');

	  try {

		  ifrm.style.margin = "0px";

		  ifrm.style.padding = "0px";

		  ifrm.style.border = '0px none';

		  ifrm.style.width = width + "px";

		  ifrm.style.height = height + "px";

		  ifrm.style.overflow = 'hidden';

	  } catch(e) {

	  }

	  return ifrm;

}

// fire off cookie matching pixels first

fireCookieMatchingPixels();

// next, fire off quality scoring pixels

fireQSPixels();

// now process the ad tag

var qs = null;

var scriptTag;

var fpTag;

if (NGIN_AdsiFrame_Opts!==null) {

	  qs = NGIN_AdsiFrame_Opts;

} else {

	  qs = getQueryString();

}

var cdpnLocTag = "<script type='text/javascript'>var NGIN_Loc={};" + "NGIN_Loc.loc='" + getSiteURL()

					+ "';NGIN_Loc.ref='" + getRefSiteURL()

					+ "';NGIN_Loc.ifr='" + (isInIframe() ? '1' : '0')

					+ "';NGIN_Loc.od='" + getOD() + "';</script>";

var domain = getQueryStringArg(qs,'NGIN_domain', adserver_domain);

var abf = 0;

var id = getQueryStringArg(qs, 'pzoneid');

if (!id) {

	id = getQueryStringArg(qs, 'zoneid');

}

abf = getNGINAtf(id, getNGINViewport());

var org_tld = getQueryStringArg(qs, 'tld', "");

var ct_url = getQueryStringArg(qs, 'ct0', "");

var buyer_id = getQueryStringArg(qs, 'buyerid', "");

var sndprc = getQueryStringArg(qs, 'sndprc', "");

var ui = getQueryStringArg(qs, 'ui', "");

var cb = Math.round(new Date().getTime() / 1000);

var adQueryString = getNGINQueryString(id, qs, abf, false);

adQueryString += "&dt=in";

adQueryString += "&buyerid=" + escape(buyer_id);

adQueryString += "&loc=" + escape(getSiteURL());

adQueryString += "&ref=" + escape(getRefSiteURL());

adQueryString += "&ifr=" + (isInIframe() ? '1' : '0');

adQueryString += "&tld=" + escape(getOD());

adQueryString += "&sndprc=" + escape(sndprc);

adQueryString += "&ui=" + ui;

adQueryString += "&ct=" + escape(ct_url);

adQueryString += "&org_tld=" + escape(org_tld);

adQueryString += "&cb=" + cb;

var fpTag = '<scr'+'ipt type="text/javascript" src="http://' + domain + delivery_path

			  + adQueryString + '"></scr' + 'ipt>';

var htmlPrefix = "<html><head><title></title></head><body style='padding:0px;margin:0px;'>";

var htmlSuffix = "<![if !IE]><script type='text/javascript'>document.close();</script><![endif]></body></html>";

if (isInIframe()) {

	document.write(fpTag);

} else {

  if (NGIN_AdsiFrame_Opts !== null) {

  	var placement = NGIN_placement_id || "NGIN_FPI_" + getQueryStringArg(qs, 'z', 0);

  	scriptTag = document.getElementById(placement) || getScriptTag();

  } else {

  	scriptTag = getScriptTag();

  }

  var width = getQueryStringArg(qs, 'width', 160);

  var height = getQueryStringArg(qs, 'height', 600);

  var ifrm = createiFrame(id, width, height);

  scriptTag.parentNode.insertBefore(ifrm, scriptTag);

  fpTag = '<scr'+'ipt type="text/javascript" src="http://' + domain + delivery_path + adQueryString + '"></scr'+'ipt>';

  if(getQueryStringArg(qs, 'NGIN_src', '0') === '1') {

    var ad_server_domain = getQueryStringArg(qs, 'NGIN_ad_domain', adserver_domain);

    ifrm.src = 'http://' + ad_server_domain + delivery_path + adQueryString;

  } else {

    var ifr_content = ifrm.contentWindow.document || ifrm.contentDocument;

    ifr_content.write(htmlPrefix + fpTag + htmlSuffix);

  }

}

  return {};

})();

NGIN_placement_id = null;

NGIN_AdsiFrame_Opts = null;

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