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  • Will PHP Die In Web Page Development World?

    - by Morgan Cheng
    I know that PHP is still the most popular web programming language in the world. This question just want to bring some of my concerns about PHP. PHP is naturally bound to C10K problem. Since PHP (generally run in Apache) cannot be event-driven or asynchronous, each HTTP request will occupy at least one thread or process. This makes it resistant to be more scalable. Currently, a lot of web sites (like Facebook) with high performance and scalability still depends on PHP in their front end servers. I suppose it is due to legacy reason. Is it possible that PHP will be replaced by language more suitable for C10K?

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  • Must a Language that Implements Monads be Statically Typed?

    - by Morgan Cheng
    I am learning functional programming style. From this link http://channel9.msdn.com/shows/Going+Deep/Brian-Beckman-Dont-fear-the-Monads/, Brian Beckman gave a brilliant introduction about Monad. He mentioned that Monad is about composition of functions so as to address complexity. A Monad includes a unit function that transfers type T to an amplified type M(T); and a Bind function that, given function from T to M(U), transforms type M(T) to another type M(U). (U can be T, but is not necessarily). In my understanding, the language implementing monad should be type-checked statically. Otherwise, type errors cannot be found during compilation and "Complexity" is not controlled. Is my understanding correct?

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  • How to Treat Race Condition of Session in Web Application?

    - by Morgan Cheng
    I was in a ASP.NET application has heavy traffic of AJAX requests. Once a user login our web application, a session is created to store information of this user's state. Currently, our solution to keep session data consistent is quite simple and brutal: each request needs to acquire a exclusive lock before being processed. This works fine for tradition web application. But, when the web application turns to support AJAX, it turns to not efficient. It is quite possible that multiple AJAX requests are sent to server at the same time without reloading the web page. If all AJAX requests are serialized by the exclusive lock, the response is not so quick. Anyway, many AJAX requests that doesn't access same session variables are blocked as well. If we don't have a exclusive lock for each requests, then we need to treat all race condition carefully to avoid dead lock. I'm afraid that would make the code complex and buggy. So, is there any best practice to keep session data consistent and keep code simple and clean?

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  • Why Enumerable.Range is faster than a direct yield loop?

    - by Morgan Cheng
    Below code is checking performance of three different ways to do same solution. public static void Main(string[] args) { // for loop { Stopwatch sw = Stopwatch.StartNew(); int accumulator = 0; for (int i = 1; i <= 100000000; ++i) { accumulator += i; } sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, accumulator); } //Enumerable.Range { Stopwatch sw = Stopwatch.StartNew(); var ret = Enumerable.Range(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } //self-made IEnumerable<int> { Stopwatch sw = Stopwatch.StartNew(); var ret = GetIntRange(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } } private static IEnumerable<int> GetIntRange(int start, int count) { int end = start + count; for (int i = start; i < end; ++i) { yield return i; } } } The result is like this: time = 306; result = 987459712 time = 1301; result = 987459712 time = 2860; result = 987459712 It is not surprising that "for loop" is faster than the other two solutions, because Enumerable.Aggregate takes more method invocations. However, it really surprises that "Enumerable.Range" is faster than the "self-made IEnumerable". I thought that Enumerable.Range will take more overhead than the simple GetIntRange method. What is the possible reason for this?

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  • Is it possible to listen to relational database update?

    - by Morgan Cheng
    Is it possible to listen to relation database update? For example, my web app want to send data update to client through Comet technology. I can have the program to poll the database periodically, but that would not be performant and scalable. If app can hood to a "event handler" of database, then app can get notification every time given database table data is updated. This sounds more promising, but I didn't find any concrete example for it. This is listener pattern. Does common relational database support such feature?

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  • Expanding Rows for Unique Checkboxes

    - by Marc Morgan
    I was just recently given a project for my job to write a script that compares two mysql databases and print out information into an html table. Currently, I am trying to insert a checkbox by each individual's name and when selected, rows pertaining to that individual will expand underneath the person's name. I am combining javascript into my script to do this, although I really have no experience is it. The problem I am having is that when any checkbox is selected, all the rows for each individual is expanding instead of the rows pertaining only to the one individual selected. Here is the coding so far: <?php $link = mysql_connect ($server = "harris.lib.fit.edu", $username = "", $password = "") or die(mysql_error()); $db = mysql_select_db ("library-test") or die(mysql_error()); $ids = mysql_query("SELECT * FROM `ifc_studylog`") or die(mysql_error()); //not single quotes (tilda apostrophy) $x=0; $n=0; while($row = mysql_fetch_array( $ids )) { $tracksid1[$x] = $row['fitID']; $checkin[$x] = $row['checkin']; $checkout[$x] = $row['checkout']; $n++; $x++; } $names = mysql_query("SELECT * FROM `ifc_users`") or die(mysql_error()); //not single quotes (tilda apostrophy) $x=0; while($row = mysql_fetch_array( $names )) { $tracksnamefirst[$x] = $row['firstName']; $tracksnamesecond[$x] = $row['lastname']; $tracksid2[$x] = $row['fitID']; $tracksuser[$x] = $row['tracks']; $x++; } $x=0; foreach($tracksid2 as $comparename) { $chk = strval($x); ?> <script type='text/javascript' src='http://code.jquery.com/jquery-1.4.2.js'></script> <script type='text/javascript'> $(window).load(function () { $('.varx').click(function () { $('.text').toggle(this.checked); });}); </script> <?php echo '<td><input id = "<?=$chk?>" type="checkbox" class="varx" /></td>'; echo '<td align="center">'.$comparename.'</td>'; echo'<td align="center">'.$tracksnamefirst[$x].'</td>'; echo'<td align="center">'.$tracksnamesecond[$x].'</td>'; $z=0; foreach($tracksid1 as $compareid) { $HH=0; $MM =0; $SS =0; if($compareid == $comparename)// && $tracks==$tracksuser[$x]) { $SS = sprintf("%02s",(($checkout[$z]-$checkin[$z])%60)); $MM = sprintf("%02s",(($checkout[$z]-$checkin[$z])/60 %60)); $HH = sprintf("%02s",(($checkout[$z]-$checkin[$z])/3600 %24)); // echo'<td align="center">'.$HH.':'.$MM.':'.$SS.'</td>'; echo '</tr>'; echo '<tr>'; echo "<td id='txt' class='text' align='center' colspan='2' style='display:none'></td>"; echo "<td id='txt' class='text' align='center' style='display:none'>".$checkin[$z]."</td>"; echo '</tr>'; } echo '<tr>'; $z++; echo '</tr>'; } $x++; } } ?> Any Help is appreciated and sorry if I am too vague on the subject. The username and password is left off for security purposes.

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  • Why is calling close() after fopen() not closing?

    - by Richard Morgan
    I ran across the following code in one of our in-house dlls and I am trying to understand the behavior it was showing: long GetFD(long* fd, const char* fileName, const char* mode) { string fileMode; if (strlen(mode) == 0 || tolower(mode[0]) == 'w' || tolower(mode[0]) == 'o') fileMode = string("w"); else if (tolower(mode[0]) == 'a') fileMode = string("a"); else if (tolower(mode[0]) == 'r') fileMode = string("r"); else return -1; FILE* ofp; ofp = fopen(fileName, fileMode.c_str()); if (! ofp) return -1; *fd = (long)_fileno(ofp); if (*fd < 0) return -1; return 0; } long CloseFD(long fd) { close((int)fd); return 0; } After repeated calling of GetFD with the appropriate CloseFD, the whole dll would no longer be able to do any file IO. I wrote a tester program and found that I could GetFD 509 times, but the 510th time would error. Using Process Explorer, the number of Handles did not increase. So it seems that the dll is reaching the limit for the number of open files; setting _setmaxstdio(2048) does increase the amount of times we can call GetFD. Obviously, the close() is working quite right. After a bit of searching, I replaced the fopen() call with: long GetFD(long* fd, const char* fileName, const char* mode) { *fd = (long)open(fileName, 2); if (*fd < 0) return -1; return 0; } Now, repeatedly calling GetFD/CloseFD works. What is going on here?

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  • How to make write operation idempotent?

    - by Morgan Cheng
    I'm reading article about recently release Gizzard sharding framework by twitter(http://engineering.twitter.com/2010/04/introducing-gizzard-framework-for.html). It mentions that all write operations must be idempotent to make sure high reliability. According to wikipedia, "Idempotent operations are operations that can be applied multiple times without changing the result." But, IMHO, in Gazzard case, idempotent write operation should be operations that sequence doesn't matter. Now, my question is: How to make write operation idempotent? The only thing I can image is to have a version number attached to each write. For example, in blog system. Each blog must have a $blog_id and $content. In application level, we always write a blog content like this write($blog_id, $content, $version). The $version is determined to be unique in application level. So, if application first try to set one blog to "Hello world" and second want it to be "Goodbye", the write is idempotent. We have such two write operations: write($blog_id, "Hello world", 1); write($blog_id, "Goodbye", 2); These two operations are supposed to changed two different records in DB. So, no matter how many times and what sequence these two operations executed, the results are same. This is just my understanding. Please correct me if I'm wrong.

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  • Dangers when deploying Flash/Flex UI test automation hooks to production?

    - by Merlyn Morgan-Graham
    I am interested in doing automated testing against a Flex based UI. I have found out that my best options for UI automation (due to being C# controllable, good licensing conditions, etc) all seem to require that I compile test hooks into my application. Because of this, I am thinking of recommending that these hooks be compiled into our build. I have found a few places on the net that recommend not deploying bits with this instrumentation enabled, and I'd like to know why. Is it a performance drain, or a security risk? If it is a security risk, can you explain how the attack surface is increased? I am not a Flash or Flex developer, though I have some experience with threat modeling. For reference, here's the tools I'm specifically considering: QTP Selenium-Flex API I am having problems finding all the warnings/suggestions I found last night, but here's an example that I can find: http://www.riatest.com/products/getting-started.html Warning! Automation enabled applications expose all properties of all GUI components. This makes them vulnerable to malicious use. Never make automation enabled application publicly available. Always restrict access to such applications and to RIATest Loader to trusted users only. Related question (how to do conditional compilation to insert/remove those hooks): Conditionally including Flex libraries (SWCs) in mxmlc/compc ant tasks

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  • How to check whether user is login in web application?

    - by Morgan Cheng
    I want to learn the whole details of web application authentication. So, I decided to write a CodeIgniter authentication library from scratch. Now, I have to make design decision about how to determine whether one user is login. Basically, after user input username & password pair. A cookie is set for this session, following navigations in the web application will not require username & password. The server side will check whether the session cookie is valid to determine whether current user is login. The question is: how to determine whether cookie is valid cookie issued from server side? I can image the most simple way is to have the cookie value stored in session status as well. For each HTTP request, compare the value from cookie and the value from server session. (Since CodeIgniter session library store session variables in cookies, it is not applicable without some tweak.) This method requires storage in server side. For huge web application that is deployed in multiple datacenters. It is possible that user input username & password when browsing in one datacenter, while he/she access the web application in another datacenter later. The expected behavior is that user just input username & password once. As a result, all datacenters should be able to access the session status. That is possible not applicable even the session status is stored in external storage such as database. I tried Google. I login Google with Asian proxy which is supposed to direct me to datacenters in Asian. Then I switch to North American proxy which should direct me to datacenters in North America. It recognize my login without asking username and password again. So, is there any way to determine whether user is login without server side session status?

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  • Find directories not containing a specific directory

    - by Morgan ARR Allen
    Been searching around for a bit and cannot find a solution for this one. I guess I'm looking for a leaf-directory by name. In this example I'd like to get a list of directories call 'modules' that do NOT have a subdirectory called module. modules/package1/modules/spackage1 modules/package1/modules/spackage2 modules/package1/modules/spackage3/modules modules/package1/modules/spackage3/modules/spackage1 modules/package2/modules/ The list I desire would contain modules/package1/modules/spackage3/modules/ modules/package2/modules/ All the directories named module that do not have a subdirectory called module I started with trying something this with no luck find . -name modules \! -exec sh -c 'find -name modules' \; -exec works on exit code, okay lets pass the count as exit code find . -name modules -exec sh -c 'exit $(find {} -name modules|grep -n ""|tail -n1|cut -d: -f1)' \; This should take the count of each subdirectory called modules and exit with it. No such love.

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  • Trying to output a list using class

    - by captain morgan
    Am trying to get the moving average of a price..but i keep getting an attribute error in my Moving_Average class. ('Moving_Average' object has no attribute 'days'). Here is what I have: class Moving_Average: def calculation(self, alist:list,days:int): m = self.days prices = alist[1::2] average = [0]* len(prices) signal = ['']* len(prices) for m in range(0,len(prices)-days+1): average[m+2] = sum(prices[m:m+days])/days if prices[m+2] < average[m+2]: signal[m+2]='SELL' elif prices[m+2] > average[m+2] and prices[m+1] < average[m+1]: signal[m+2]='BUY' else: signal[m+2] ='' return average,signal def print_report(symbol:str,strategy:str): print('SYMBOL: ', symbol) print('STRATEGY: ', strategy) print('Date Closing Strategy Signal') def user(): strategy = ''' Which of the following strategy would you like to use? * Simple Moving Average [S] * Directional Indicator[D] Please enter your choice: ''' if signal_strategy in 'Ss': days = input('Please enter the number of days for the average') days = int(days) strategy = 'Simple Moving Average {}-days'.format(str(days)) m = Moving_Average() ma = m.calculation(gg, days) print(ma) gg is an list that contains date and prices. [2013-10-01,60,2013-10-02,60] The output is supposed to look like: Date Price Average Signal 2013-10-01 60.0 2013-10-02 60.0 60.00 BUY

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  • What's the best way to store Logon User information for Web Application?

    - by Morgan Cheng
    I was once in a project of web application developed on ASP.NET. For each logon user, there is an object (let's call it UserSessionObject here) created and stored in RAM. For each HTTP request of given user, matching UserSessoinObject instance is used to visit user state information and connection to database. So, this UserSessionObject is pretty important. This design brings several problems found later: 1) Since this UserSessionObject is cached in ASP.NET memory space, we have to config load balancer to be sticky connection. That is, HTTP request in single session would always be sent to one web server behind. This limit scalability and maintainability. 2) This UserSessionObject is accessed in every HTTP request. To keep the consistency, there is a exclusive lock for the UserSessionObject. Only one HTTP request can be processed at any given time because it must to obtain the lock first. The performance and response time is affected. Now, I'm wondering whether there is better design to handle such logon user case. It seems Sharing-Nothing-Architecture helps. That means long user info is retrieved from database each time. I'm afraid that would hurt performance. Is there any design pattern for long user web app? Thanks.

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  • How to design data storage for partitioned tagging system?

    - by Morgan Cheng
    How to design data storage for huge tagging system (like digg or delicious)? There is already discussion about it, but it is about centralized database. Since the data is supposed to grow, we'll need to partition the data into multiple shards soon or later. So, the question turns to be: How to design data storage for partitioned tagging system? The tagging system basically has 3 tables: Item (item_id, item_content) Tag (tag_id, tag_title) TagMapping(map_id, tag_id, item_id) That works fine for finding all items for given tag and finding all tags for given item, if the table is stored in one database instance. If we need to partition the data into multiple database instances, it is not that easy. For table Item, we can partition its content with its key item_id. For table Tag, we can partition its content with its key tag_id. For example, we want to partition table Tag into K databases. We can simply choose number (tag_id % K) database to store given tag. But, how to partition table TagMapping? The TagMapping table represents the many-to-many relationship. I can only image to have duplication. That is, same content of TagMappping has two copies. One is partitioned with tag_id and the other is partitioned with item_id. In scenario to find tags for given item, we use partition with tag_id. If scenario to find items for given tag, we use partition with item_id. As a result, there is data redundancy. And, the application level should keep the consistency of all tables. It looks hard. Is there any better solution to solve this many-to-many partition problem?

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  • How to Implement Dynamic Timestamp in Web Page?

    - by Morgan Cheng
    In Facebook and twitter, we can see that there is a timestamp like "23 seconds ago" or "1 hour ago" for each event & tweet. If we leave the page for some time, the timestamp changes accordingly. Since it is possible that user machine doesn't have same system time as server machine, how to make the dynamic timestamp accurate? My idea is: It is always based on server time. When request is sent to server for the web page, timestamp T1 (seconds to 1970/1/1) is rendered into inline javascript variable. The displayed timestamp ("23 seconds ago") is calculated by T1 instead of local time. I'm not sure whether this is how Facebook/Twitter do it. Is there any better idea?

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  • What requests do browsers' "F5" and "Ctrl + F5" refreshes generate?

    - by Morgan Cheng
    Is there a standard for what actions F5 and Ctrl+F5 trigger in web browsers? I once did experiment in IE6 and Firefox 2.x. The "F5" refresh would trigger a HTTP request sent to the server with an "If-Modified-Since" header, while "Ctrl+F5" would not have such a header. In my understanding, F5 will try to utilize cached content as much as possible, while "Ctrl+F5" is intended to abandon all cached content and just retrieve all content from the servers again. But today, I noticed that in some of the latest browsers (Chrome, IE8) it doesn't work in this way anymore. Both "F5" and "Ctrl+F5" send the "If-Modified-Since" header. So how is this supposed to work, or (if there is no standard) how do the major browsers differ in how they implement these refresh features?

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  • Filter Datagrid onLoad

    - by Morgan Delvanna
    My data grid successfully filters when I select a month from a dropdown list, however when I try to filter it onLoad it just doesn't filter. The dropdown successfully displays the current month, and the grid should also show the current month data. <script type="text/javascript"> dojo.require("dojox.grid.DataGrid"); dojo.require("dojox.data.XmlStore"); dojo.require("dijit.form.FilteringSelect"); dojo.require("dojo.data.ItemFileReadStore"); dojo.require("dojo.date"); theMonth = new Date(); dojo.addOnLoad(function() { dojo.byId('monthInput').value = month_name[(theMonth.getMonth()+1)]; var filterString='{month: "' + theMonth.getMonth() + '"}'; var filterObject=eval('('+filterString+')'); dijit.byId("eventGrid").filter(filterObject); } ); var eventStore = new dojox.data.XmlStore({url: "events.xml", rootItem: "event", keyAttribute: "dateSort"}); function monthClick() { var ctr, test, rtrn; test = dojo.byId('monthInput').value; for (ctr=0;ctr<=11;ctr++) { if (test==month_name[ctr]) { rtrn = ctr; } } var filterString='{month: "' + rtrn + '"}'; var filterObject=eval('('+filterString+')'); eventGrid.setQuery(filterObject); } </script> </head> <body class="tundra"> <div id="header" dojoType="dijit.layout.ContentPane" region="top" class="pfga"></div> <div id="menu" dojoType="dijit.layout.ContentPane" region="left" class="pfga"></div> <div id="content" style="width:750px; overflow:visible" dojoType="dijit.layout.ContentPane" region="center" class="pfga"> <div dojotype="dojo.data.ItemFileReadStore" url="months.json" jsID="monthStore"></div> <div id="pagehead" class="Heading1" >Upcoming Events</div> <p> <input dojoType="dijit.form.FilteringSelect" store="monthStore" searchAttr="month" name="id" id="monthInput" class="pfga" onChange="monthClick()" /> </p> <table dojoType="dojox.grid.DataGrid" store="eventStore" class="pfga" style="height:500px; width:698px" clientSort="true" jsID="eventGrid"> <thead> <tr> <th field="date" width="80px">Date</th> <th field="description" width="600px">Description</th> </tr> <tr> <th field="time" colspan="2">Details</th> </tr> </thead> </table> </div> <div id="footer"></div>

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  • Why Windows Live Spaces Fetch Image Through HTTPS?

    - by Morgan Cheng
    I happens to find that, when a live space page is loaded, inline images are fetched by https protocol instead of http protocol. This doesn't make sense. The text part of live space is not fetched by https, why images are fetched with https? I bet the https way to fetch image just make the page loaded slower. Is there any special advantage to choose https over http in this case?

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  • How to invoke static method in C#4.0 with dynamic type?

    - by Morgan Cheng
    In C#4.0, we have dynamic type, but how to invoke static method of dynamic type object? Below code will generate exception at run time. class Foo { public static int Sum(int x, int y) { return x + y; } } class Program { static void Main(string[] args) { dynamic d = new Foo(); Console.WriteLine(d.Sum(1, 3)); } } IMHO, dynamic is invented to bridge C# and other programming language. There is some other language (e.g. Java) allows to invoke static method through object instead of type. BTW, The introduction of C#4.0 is not so impressive compared to C#3.0.

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  • Is Form Tag Necessary in AJAX Web Application?

    - by Morgan Cheng
    I read some AJAX-Form tutorial like this. The tag form is used in HTML code. However, I believed that it is not necessary. Since we send HTTP request through XmlHttpRequest, the sent data can be anything, not necessary input in form. So, is there any reason to have form tag in HTML for AJAX application?

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  • why multipart/x-mixed-replace is needed for Comet?

    - by Morgan Cheng
    I'm reading this article about Comet http://en.wikipedia.org/wiki/Comet_(programming). It mentions that browser should support multipart/x-mixed-replace to make XmlHttpRequest Streaming possible. Why this multipart/x-mixed-replace is necessary? Without this header, HTTP response can still be chunked and sent piece by piece to browser, right?

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  • Is It Possible to Make Close Sourced PHP Product?

    - by Morgan Cheng
    I'm curious that whether all PHP product must be open sourced if it is to be deployed to other's web site. Since PHP code is executed by interpretation, if I have PHP product to be deployed on other's host, it seems no reason to prevent others view the source code. So, PHP product is destined to be open source, right?

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  • Multiple key map in c++

    - by Morgan
    Hi, I'm wondering if any of you know of a c++ associative map container type which I can perform multiple key lookups on. The map needs to have constant time lookups but I don't care if it's ordered or unordered. It just needs to be fast. For example, I want to store a bunch of std::vector objects in a map with an integer and a void* as the lookup keys. Both the int and the void* must match for my vector to be retrieved. Does anything like this exist already? Or am I going to have to roll my own. If so, any suggestions? I've been trying to store a boost::unordered_map inside another boost::unordered_map, but I have not had any success with this method yet. Maybe I will continue Pershing this method if there is no simpler way. Thanks!

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