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      1 /*
      2   Copyright (c) 2012 The Chromium Authors. All rights reserved.
      3   Use of this source code is governed by a BSD-style license that can be
      4   found in the LICENSE file.
      5 */
      6 
      7 /**
      8  * @fileoverview Common methods for performance-plotting Javascript.
      9  */
     10 
     11 /**
     12  * Fetches a URL asynchronously and invokes a callback when complete.
     13  *
     14  * @param {string} url URL to fetch.
     15  * @param {Function(string, string)} callback The function to invoke when the
     16  *     results of the URL fetch are complete.  The function should accept two
     17  *     strings representing the URL data, and any errors, respectively.
     18  */
     19 function Fetch(url, callback) {
     20   var r = new XMLHttpRequest();
     21   r.open('GET', url, true);
     22   r.setRequestHeader('pragma', 'no-cache');
     23   r.setRequestHeader('cache-control', 'no-cache');
     24 
     25   r.onreadystatechange = function() {
     26     if (r.readyState == 4) {
     27       var text = r.responseText;
     28       var error;
     29       if (r.status != 200)
     30         error = url + ': ' + r.status + ': ' + r.statusText;
     31       else if (!text)
     32         error = url + ': null response';
     33       callback(text, error);
     34     }
     35   }
     36 
     37   r.send(null);
     38 }
     39 
     40 /**
     41  * Parses the parameters of the current page's URL.
     42  *
     43  * @return {Object} An object with properties given by the parameters specified
     44  *     in the URL's query string.
     45  */
     46 function ParseParams() {
     47   var result = new Object();
     48 
     49   var query = window.location.search.substring(1)
     50   if (query.charAt(query.length - 1) == '/')
     51     query = query.substring(0, query.length - 1)  // Strip trailing slash.
     52   var s = query.split('&');
     53 
     54   for (i = 0; i < s.length; ++i) {
     55     var v = s[i].split('=');
     56     var key = v[0];
     57     var value = unescape(v[1]);
     58     result[key] = value;
     59   }
     60 
     61   if ('history' in result) {
     62     result['history'] = parseInt(result['history']);
     63     result['history'] = Math.max(result['history'], 2);
     64   }
     65   if ('rev' in result) {
     66     result['rev'] = parseInt(result['rev']);
     67     result['rev'] = Math.max(result['rev'], -1);
     68   }
     69 
     70   return result;
     71 }
     72 
     73 /**
     74  * Creates the URL constructed from the current pathname and the given params.
     75  *
     76  * @param {Object} An object containing parameters for a URL query string.
     77  * @return {string} The URL constructed from the given params.
     78  */
     79 function MakeURL(params) {
     80   var url = window.location.pathname;
     81   var sep = '?';
     82   for (p in params) {
     83     if (!p)
     84       continue;
     85     url += sep + p + '=' + params[p];
     86     sep = '&';
     87   }
     88   return url;
     89 }
     90