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/* IVLE - Informatics Virtual Learning Environment
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* Copyright (C) 2007-2008 The University of Melbourne
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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* Module: JavaScript Utilities
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* Defines some generic JavaScript utility functions.
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/* Expects the following variables to have been declared by JavaScript in
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* the HTML generated by the server:
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/** Removes all children of a given DOM element
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* \param elem A DOM Element. Will be modified.
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function dom_removechildren(elem)
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while (elem.lastChild != null)
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elem.removeChild(elem.lastChild);
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/** Creates a DOM element with simple text inside it.
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* \param tagname String. Name of the element's tag (eg. "p").
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* \param text String. Text to be placed inside the element.
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* \param title String, optional. Tooltip for the text.
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* (Note, title creates a span element around the text).
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* \return DOM Element object.
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function dom_make_text_elem(tagname, text, title)
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if (text == null) text = "";
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var elem = document.createElement(tagname);
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textnode = document.createTextNode(text);
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textnode = document.createElement("span");
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textnode.setAttribute("title", title);
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textnode.appendChild(document.createTextNode(text));
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elem.appendChild(textnode);
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/** Creates a DOM element with hyperlinked text inside it.
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* \param tagname String. Name of the element's tag (eg. "p").
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* \param text String. Text to be placed inside the element.
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* \param title String, optional. Sets a tooltip for the link.
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* \param href String. URL the text will link to. This is a raw string,
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* it will automatically be URL-encoded.
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* \param onclick Optional string. Will be set as the "onclick" attribute
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* \param dontencode Optional boolean. If true, will not encode the href.
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* if including query strings, you must set this to true and use build_url
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* to escape the URI correctly.
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* \return DOM Element object.
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function dom_make_link_elem(tagname, text, title, href, onclick, dontencode)
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if (text == null) text = "";
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if (href == null) href = "";
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var elem = document.createElement(tagname);
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var link = document.createElement("a");
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if (dontencode != true)
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href = urlencode_path(href);
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link.setAttribute("href", href);
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link.setAttribute("title", title);
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link.setAttribute("onclick", onclick);
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link.appendChild(document.createTextNode(text));
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elem.appendChild(link);
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/** Creates a DOM img element. All parameters are optional except src.
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* If alt (compulsory in HTML) is omitted, will be set to "".
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function dom_make_img(src, width, height, title, alt)
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var img = document.createElement("img");
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img.setAttribute("src", urlencode_path(src));
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img.setAttribute("width", width);
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img.setAttribute("height", height);
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img.setAttribute("title", title);
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if (alt == null) alt = "";
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img.setAttribute("alt", alt);
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/** Given a number of bytes, returns a string representing the file size in a
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* human-readable format.
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* eg. nice_filesize(6) -> "6 bytes"
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* nice_filesize(81275) -> "79.4 kB"
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* nice_filesize(13498346) -> "12.9 MB"
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* \param bytes Number of bytes. Must be an integer.
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function nice_filesize(bytes)
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if (bytes == null) return "";
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return bytes.toString() + " B";
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return size.toFixed(1) + " kB";
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return size.toFixed(1) + " MB";
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return size.toFixed(1) + " GB";
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/** Given a URL, returns an object containing a number of attributes
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* describing the components of the URL, similar to CGI request variables.
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* The object has the following attributes:
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* The first five of these are strings, which comprise the URL as follows:
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* <scheme> "://" <server_name> ":" <server_port> <path> "?" <query_string>
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* Any of these strings may be set to null if not found.
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* "args" is an object whose attributes are the query_string arguments broken
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* Args values are strings for single values, arrays of strings for values
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* whose names appear multiple times.
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* args is never null, though it may be empty.
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* All strings are decoded/unescaped. Reserved characters
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* (; , / ? : @ & = + * $) are not decoded except in args and path.
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* \param url String. A URL. To read from the current browser window, use
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* window.location.href.
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* \return The above described object.
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function parse_url(url)
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/* Split scheme from rest */
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index = url.indexOf("://");
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obj.scheme = url.substr(0, index);
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url = url.substr(index+3);
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/* Split server name/port from rest */
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index = url.indexOf("/");
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serverpart = url.substr(0, index);
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url = url.substr(index);
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/* Split server name from port */
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index = serverpart.indexOf(":");
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obj.server_name = serverpart;
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obj.server_port = null;
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obj.server_name = serverpart.substr(0, index);
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obj.server_port = serverpart.substr(index+1);
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/* Split path from query string */
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obj.query_string = null;
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index = url.indexOf("?");
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obj.query_string = null;
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obj.path = url.substr(0, index);
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obj.query_string = url.substr(index+1);
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obj.path = decodeURIComponent(obj.path);
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/* Split query string into arguments */
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if (obj.query_string != null)
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var args_strs = obj.query_string.split("&");
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var arg_key, arg_val;
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for (var i=0; i<args_strs.length; i++)
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arg_str = args_strs[i];
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index = arg_str.indexOf("=");
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/* Ignore malformed args */
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arg_key = decodeURIComponent(arg_str.substr(0, index));
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arg_val = decodeURIComponent(arg_str.substr(index+1));
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/* Collision - make an array */
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if (args[arg_key] instanceof Array)
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args[arg_key][args[arg_key].length] = arg_val;
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args[arg_key] = [args[arg_key], arg_val];
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args[arg_key] = arg_val;
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/** Builds a query_string from an args object. Encodes the arguments.
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* \param args Args object as described in parse_url.
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* \return Query string portion of a URL.
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function make_query_string(args)
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var query_string = "";
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for (var arg_key in args)
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arg_val = args[arg_key];
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if (arg_val instanceof Array)
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for (var i=0; i<arg_val.length; i++)
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query_string += "&" + encodeURIComponent(arg_key) + "=" +
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encodeURIComponent(arg_val[i]);
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query_string += "&" + encodeURIComponent(arg_key) + "=" +
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encodeURIComponent(arg_val);
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if (query_string != "")
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/* Drop the first "&" */
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query_string = query_string.substr(1);
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/** Given an object exactly of the form described for the output of parseurl,
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* returns a URL string built from those parameters. The URL is properly
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* parseurl and buildurl are strict inverses of each other.
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* Note that either query_string or args may be supplied. If both are
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* supplied, query_string is preferred (because it keeps the argument order).
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* If you take a url from parseurl, modify args, and pass to buildurl,
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* you need to set query_string to null to use the new args.
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* \param obj Object as returned by parseurl.
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* \return String, a URL.
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function build_url(obj)
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var query_string = null;
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if (("scheme" in obj) && obj.scheme != null)
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url = obj.scheme.toString() + "://";
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if (("server_name" in obj) && obj.server_name != null)
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url += obj.server_name.toString();
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if (("server_port" in obj) && obj.server_port != null)
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url += ":" + obj.server_port.toString();
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if (("path" in obj) && obj.path != null)
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var path = urlencode_path(obj.path.toString());
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if (url.length > 0 && path.length > 0 && path.charAt(0) != "/")
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if (("query_string" in obj) && obj.query_string != null)
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query_string = encodeURI(obj.query_string.toString());
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else if (("args" in obj) && obj.args != null)
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query_string = make_query_string(obj.args);
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if (query_string != "" && query_string != null)
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url += "?" + query_string;
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/** URL-encodes a path. This is a special case of URL encoding as all
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* characters *except* the slash must be encoded.
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function urlencode_path(path)
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/* Split up the path, URLEncode each segment with encodeURIComponent,
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var split = path.split('/');
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for (var i=0; i<split.length; i++)
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split[i] = encodeURIComponent(split[i]);
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path = path_join.apply(null, split);
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if (split[0] == "" && split.length > 1) path = "/" + path;
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/** Writes a JSONable object to the cookie under a particular key
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* (JSON encoded and URL encoded).
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function write_cookie(key, value)
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var sendstr = encodeURIComponent(key) + "="
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+ encodeURIComponent(JSON.stringify(value))
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+ "; path=" + urlencode_path(root_dir);
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/* This actually just assigns to the key, not replacing the whole cookie
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* as it appears to. */
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document.cookie = sendstr;
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/** Reads a cookie which has a JSONable object encoded as its value.
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* Returns the object, parsed from JSON.
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function read_cookie(key)
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var cookies = document.cookie.split(";");
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var checkstart = encodeURIComponent(key) + "=";
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var checklen = checkstart.length;
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for (var i=0; i<cookies.length; i++)
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var cookie = cookies[i];
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while (cookie[0] == ' ')
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cookie = cookie.substr(1);
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if (cookie.substr(0, checklen) == checkstart)
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var valstr = cookie.substr(checklen);
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valstr = decodeURIComponent(valstr);
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return JSON.parse(valstr);
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/** Given an argument map, as output in the args parameter of the return of
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* parseurl, gets the first occurence of an argument in the URL string.
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* If the argument was not found, returns null.
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* If there was a single argument, returns the argument.
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* If there were multiple arguments, returns the first.
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* \param args Object mapping arguments to strings or arrays of strings.
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* \param arg String. Argument name.
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function arg_getfirst(args, arg)
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if (r instanceof Array)
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/** Given an argument map, as output in the args parameter of the return of
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* parseurl, gets all occurences of an argument in the URL string, as an
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* If the argument was not found, returns [].
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* Otherwise, returns all occurences as an array, even if there was only one.
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* \param args Object mapping arguments to strings or arrays of strings.
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* \param arg String. Argument name.
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* \return Array of strings.
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function arg_getlist(args, arg)
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if (r instanceof Array)
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/** Joins one or more paths together. Accepts 1 or more arguments.
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function path_join(path1 /*, path2, ... */)
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for (var i=0; i<arguments.length; i++)
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if (arg.length == 0) continue;
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if (arg.charAt(0) == '/')
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if (path.length > 0 && path.charAt(path.length-1) != '/')
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/** Builds a multipart_formdata string from an args object. Similar to
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* make_query_string, but it returns data of type "multipart/form-data"
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* instead of "application/x-www-form-urlencoded". This is good for
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* encoding large strings such as text objects from the editor.
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* Should be written with a Content-Type of
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* "multipart/form-data, boundary=<boundary>".
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* All fields are sent with a Content-Type of text/plain.
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* \param args Args object as described in parse_url.
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* \param boundary Random "magic" string which DOES NOT appear in any of
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* the argument values. This should match the "boundary=" value written to
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* the Content-Type header.
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* \return String in multipart/form-data format.
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function make_multipart_formdata(args, boundary)
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var extend_data = function(arg_key, arg_val)
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/* FIXME: Encoding not supported here (should not matter if we
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* only use ASCII names */
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data += "--" + boundary + "\r\n"
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+ "Content-Disposition: form-data; name=\"" + arg_key
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for (var arg_key in args)
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arg_val = args[arg_key];
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if (arg_val instanceof Array)
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for (var i=0; i<arg_val.length; i++)
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extend_data(arg_key, arg_val[i]);
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extend_data(arg_key, arg_val);
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data += "--" + boundary + "--\r\n";
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/** Converts a list of directories into a path name, with a slash at the end.
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* \param pathlist List of strings.
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function pathlist_to_path(pathlist)
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ret = path_join.apply(null, pathlist);
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if (ret.charAt(ret.length-1) != '/')
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/** Given a path relative to the IVLE root, gives a path relative to
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function make_path(path)
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return path_join(root_dir, path);
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/** Shorthand for make_path(path_join(app, ...))
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* Creates an absolute path for a given path within a given app.
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function app_path(app /*,...*/)
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return make_path(path_join.apply(null, arguments));
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/** Generates an absolute URL to a public application
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function public_app_path(app /*,...*/)
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return location.protocol + "//" + public_host
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+ make_path(path_join.apply(null, arguments));
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/** Given a path, gets the "basename" (the last path segment).
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function path_basename(path)
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segments = path.split("/");
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if (segments[segments.length-1].length == 0)
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return segments[segments.length-2];
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return segments[segments.length-1];
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/** Given a string str, determines whether it ends with substr */
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function endswith(str, substring)
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if (str.length < substring.length) return false;
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return str.substr(str.length - substring.length) == substring;
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/** Removes all occurences of a value from an array.
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Array.prototype.removeall = function(val)
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for (i=0; i<arr.length; i++)
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if (arr[i] != val) j++;
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/** Shallow-clones an object */
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function shallow_clone_object(obj)
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/** Returns a new XMLHttpRequest object, in a somewhat browser-agnostic
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function new_xmlhttprequest()
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return new XMLHttpRequest();
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/* Internet Explorer */
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return new ActiveXObject("Msxml2.XMLHTTP");
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return new ActiveXObject("Microsoft.XMLHTTP");
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throw("Your browser does not support AJAX. "
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+ "IVLE requires a modern browser.");
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/** Creates a random string of length length,
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* consisting of alphanumeric characters.
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var rand_chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZ"
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+ "abcdefghiklmnopqrstuvwxyz";
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function random_string(length)
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var str = Array(length);
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for (var i=0; i<length; i++)
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v = Math.floor(Math.random() * rand_chars.length);
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str[i] = rand_chars.charAt(v);
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/** Makes an XMLHttpRequest call to the server.
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* Sends the XMLHttpRequest object containing the completed response to a
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* specified callback function.
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* \param callback A callback function. Will be called when the response is
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* complete. Passed 1 parameter, an XMLHttpRequest object containing the
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* completed response. If callback is null this is a syncronous request
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* otherwise this is an asynchronous request.
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* \param app IVLE app to call (such as "fileservice").
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* \param path URL path to make the request to, within the application.
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* \param args Argument object, as described in parse_url and friends.
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* \param method String; "GET", "POST", "PUT", or "PATCH"
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* \param content_type String, optional.
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* Defaults to "application/x-www-form-urlencoded".
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function ajax_call(callback, app, path, args, method, content_type)
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content_type = "application/x-www-form-urlencoded";
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path = app_path(app, path);
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/* A random string, for multipart/form-data
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* (This is not checked against anywhere else, it is solely defined and
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* used within this function) */
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var boundary = random_string(20);
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var xhr = new_xmlhttprequest();
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var asyncronous = callback != null;
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xhr.onreadystatechange = function()
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if (xhr.readyState == 4)
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/* GET sends the args in the URL */
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url = build_url({"path": path, "args": args});
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/* open's 3rd argument = true -> asynchronous */
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xhr.open(method, url, asyncronous);
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/* POST & PUT & PATCH sends the args in the request body */
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url = encodeURI(path);
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xhr.open(method, url, asyncronous);
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if (content_type == "multipart/form-data")
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xhr.setRequestHeader("Content-Type",
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"multipart/form-data; boundary=" + boundary);
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message = make_multipart_formdata(args, boundary);
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else if (content_type == "application/x-www-form-urlencoded")
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xhr.setRequestHeader("Content-Type", content_type);
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message = make_query_string(args);
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else if (content_type == "application/json")
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xhr.setRequestHeader("Content-Type", content_type);
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message = JSON.stringify(args);
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xhr.setRequestHeader("Content-Type", content_type);
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/* Only return the XHR for syncronous requests */
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/** Attempts to JSON decodes a response object
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* If a non-200 response or the JSON decode fails then returns null
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function decode_response(response)
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if (response.status == 200)
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var responseText = response.responseText;
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return JSON.parse(responseText);
added
removed
www/media/common/util.js
