// -----------------------------------------
// Jscript name  : csfXmlHttp.js
// description   : create XMLHttpRequest
// author        : CSF
// mail address  : axcsf@163.com
// create time   : 2008-10-15 PM
// last modify time: 2008-12-04 PM
// ------------------------------------------
		
var XMLHttp = 
{
    _objPool: [], 
    _getInstance: function () 
    {
        for (var i = 0; i < this._objPool.length; i ++)
        {
            if (this._objPool[i].readyState == 0 || this._objPool[i].readyState == 4)
            {
                return this._objPool[i]; 
            }
        }

        this._objPool[this._objPool.length] = this._createObj();
        return this._objPool[this._objPool.length - 1]; 
    },
    _createObj: function ()
    {
        if (window.XMLHttpRequest)
        {
            var objXMLHttp = new XMLHttpRequest();
        }
        else
        {
            var MSXML = ['MSXML2.XMLHTTP.6.0', 'MSXML2.XMLHTTP.5.0', 'MSXML2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP', 'Microsoft.XMLHTTP'];
            for(var j = 0; j < MSXML.length; j++)
            {
                try
                {
                    var objXMLHttp = new ActiveXObject(MSXML[j]);
                    break;
                }
                catch(e)
                {
                }
            }
         }    
               
        if (objXMLHttp.readyState == null)
        {
            objXMLHttp.readyState = 0;
            objXMLHttp.addEventListener("load", function ()
                {
                    objXMLHttp.readyState = 4;
                    if (typeof objXMLHttp.onreadystatechange == "function")
                    {
                        objXMLHttp.onreadystatechange();
                    }
                },  false);
        }
        return objXMLHttp;
    },

    sendReq: function (method, url, data, callback)
    {
        var objXMLHttp = this._getInstance();
        with(objXMLHttp)
        {
            try
            {
                if (url.indexOf("?") > 0)
                {
                    url += "&randnum=" + Math.random();
                }
                else
                {
                    url += "?randnum=" + Math.random();
                }
                open(method, url, true);
                setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
                send(data);
                onreadystatechange = function ()
                {
                    if (objXMLHttp.readyState == 4 && (objXMLHttp.status == 200 || objXMLHttp.status == 304))
                    {
                        callback(objXMLHttp);
                    }
                }
            }
            catch(e)
            {
            }
        }
    }
};  

function csf(obj){return document.getElementById(obj);}