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  • Javascript scope problem with object and setTimeout

    - by Shabbyrobe
    I'm trying to make a jQuery plugin that executes a method on a timer. I'd like it to work on multiple elements on a page independently. I've reached a point where the timer executes for each element, but the method called in the setTimeout seems to only know about the last instance of the plugin. I know I'm doing something fundamentally stupid here, but I'm danged if I know what. I know stuff like this has been asked 8 million times on here before, but I've not managed to find an answer that relates to my specific problem. Here's a script that demonstrates the structure of what I'm doing. <html> <head> <script type="text/javascript" src="assets/jquery.min.js"></script> <script type="text/javascript"> var crap = 0; (function($) { jQuery.fn.pants = function(options) { var trousers = { id: null, current: 0, waitTimeMs: 1000, begin: function() { var d = new Date(); this.id = crap++; console.log(this.id); // do a bunch of stuff window.setTimeout(function(self) {return function() {self.next();}}(this), this.waitTimeMs); }, next: function() { this.current ++; console.log(this.id); window.setTimeout(function(self) {return function() {self.next();}}(this), this.waitTimeMs); }, }; options = options || {}; $.extend(trousers, options); this.each(function(index, element) { trousers.begin(); }); return this; }; } )(jQuery); jQuery(document).ready(function() { jQuery("div.wahey").pants(); }); </script> </head> <body> <div class="wahey"></div> <div class="wahey"></div> </body> </html> The output I get is this: 0 1 1 1 1 1 The output I expect to get is this: 0 1 0 1 0 1

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  • Using XAML + designer to edit Plain Old CLR Objects?

    - by Joe White
    I want to write a POCO in XAML, and use a DataTemplate to display that object in the GUI at runtime. So far, so good; I know how to do all that. Since I'll already have a DataTemplate that can transform my POCO into a WPF visual tree, is there any way to get the Visual Studio designer to play along, and have the Design View show me the POCO+DataTemplate's resulting GUI, as I edit the POCO's XAML? (Obviously the designer wouldn't know how to edit the "design view"; I wouldn't expect the Toolbox or click-and-drag to work on the design surface. That's fine -- I just want to see a preview as I edit.) If you're curious, the POCOs in question would be level maps for a game. (At this point, I'm not planning to ship an end-user map editor, so I'll be doing all the editing myself in Visual Studio.) So the XAML isn't WPF GUI objects like Window and UserControl, but it's still not something where I would want to blindly bang out some XAML and hope for the best. I want to see what I'm doing (the GUI map) as I'm doing it. If I try to make a XAML file whose root is my map object, the designer shows "Intentionally Left Blank - The document root element is not supported by the visual designer." It does this even if I've defined a DataTemplate in App.xaml's <Application.Resources>. But I know the designer can show my POCO, when it's inside a WPF object. One possible way of accomplishing what I want would be to have a ScratchUserControl that just contains a ContentPresenter, and write my POCO XAML inside that ContentPresenter's Content property, e.g.: <UserControl ...> <ContentPresenter> <ContentPresenter.Content> <Maps:Map .../> </ContentPresenter.Content> </ContentPresenter> </UserControl> But then I would have to be sure to copy the content back out into its own file when I was done editing, which seems tedious and error-prone, and I don't like tedious and error-prone. And since I can preview my XAML this way, isn't there some way to do it without the UserControl?

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  • SQL/Schema comparison and upgrade

    - by Workshop Alex
    I have a simple situation. A large organisation is using several different versions of some (desktop) application and each version has it's own database structure. There are about 200 offices and each office will have it's own version, which can be one of 7 different ones. The company wants to upgrade all applications to the latest versions, which will be version 8. The problem is that they don't have a separate database for each version. Nor do they have a separate database for each office. They have one single database which is handled by a dedicated server, thus keeping things like management and backups easier. Every office has it's own database schema and within the schema there's the whole database structure for their specific application version. As a result, I'm dealing with 200 different schema's which need to be upgraded, each with 7 possible versions. Fortunately, every schema knows the proper version so checking the version isn't difficult. But my problem is that I need to create upgrade scripts which can upgrade from version 1 to version 2 to version 3 to etc... Basically, all schema's need to be bumped up one version until they're all version 8. Writing the code that will do this is no problem. the challenge is how to create the upgrade script from one version to the other? Preferably with some automated tool. I've examined RedGate's SQL Compare and Altova's DatabaseSpy but they're not practical. Altova is way too slow. RedGate requires too much processing afterwards, since the generated SQL Script still has a few errors and it refers to the schema name. Furthermore, the code needs to become part of a stored procedure and the code generated by RedGate doesn't really fit inside a single procedure. (Plus, it's doing too much transaction-handling, while I need everything within a single transaction. I have been considering using another SQL Comparison tool but it seems to me that my case is just too different from what standard tools can deliver. So I'm going to write my own comparison tool. To do this, I'll be using ADOX with Delphi to read the catalogues for every schema version in the database, then use this to write the SQL Statements that will need to upgrade these schema's to their next version. (Comparing 1 with 2, 2 with 3, 3 with 4, etc.) I'm not unfamiliar with generating SQL-Script-Generators so I don't expect too many problems. And I'll only be upgrading the table structures, not any of the other database objects. So, does anyone have some good tips and tricks to apply when doing this kind of comparisons? Things to be aware of? Practical tips to increase speed?

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  • .NET: Is there a way to finagle a default namespace in an XPath 1.0 query?

    - by Cheeso
    I'm building a tool that performs xpath 1.0 queries on XHTML documents. The requirement to use a namespace prefix in the query is killing me. The query looks like this: html/body/div[@class='contents']/div[@class='body']/ div[@class='pgdbbyauthor']/h2[a[@name][starts-with(.,'Quick')]]/ following-sibling::ul[1]/li/a (all on one line) ...which is bad enough, except because it's xpath 1.0, I need to use an explicit namespace prefix on each QName, so it looks like this: ns1:html/ns1:body/ns1:div[@class='contents']/ns1:div[@class='body']/ ns1:div[@class='pgdbbyauthor']/ns1:h2[ns1:a[@name][starts-with(.,'Quick')]]/ following-sibling::ns1:ul[1]/ns1:li/ns1:a To set up the query, I do something like this: var xpathDoc = new XPathDocument(new StringReader(theText)); var nav = xpathDoc.CreateNavigator(); var xmlns = new XmlNamespaceManager(nav.NameTable); foreach (string prefix in xmlNamespaces.Keys) xmlns.AddNamespace(prefix, xmlNamespaces[prefix]); XPathNodeIterator selection = nav.Select(xpathExpression, xmlns); But what I want is for the xpathExpression to use the implicit default namespace. Is there a way for me to transform the unadorned xpath expression, after it's been written, to inject a namespace prefix for each element name in the query? I'm thinking, anything between two slashes, I could inject a prefix there. Excepting of course axis names like "parent::" and "preceding-sibling::" . And wildcards. That's what I mean by "finagle a default namespace". Is this hack gonna work? Addendum Here's what I mean. suppose I have an xpath expression, and before passing it to nav.Select(), I transform it. Something like this: string FixupWithDefaultNamespace(string expr) { string s = expr; s = Regex.Replace(s, "^(?!::)([^/:]+)(?=/)", "ns1:$1"); // beginning s = Regex.Replace(s, "/([^/:]+)(?=/)", "/ns1:$1"); // stanza s = Regex.Replace(s, "::([A-Za-z][^/:*]*)(?=/)", "::ns1:$1"); // axis specifier s = Regex.Replace(s, "\\[([A-Za-z][^/:*\\(]*)(?=[\\[\\]])", "[ns1:$1"); // predicate s = Regex.Replace(s, "/([A-Za-z][^/:]*)(?!<::)$", "/ns1:$1"); // end s = Regex.Replace(s, "^([A-Za-z][^/:]*)$", "ns1:$1"); // edge case s = Regex.Replace(s, "([-A-Za-z]+)\\(([^/:\\.,\\)]+)(?=[,\\)])", "$1(ns1:$2"); // xpath functions return s; } This actually works for simple cases I tried. To use the example from above - if the input is the first xpath expression, the output I get is the 2nd one, with all the ns1 prefixes. The real question is, is it hopeless to expect this Regex.Replace approach to work, as the xpath expressions get more complicated?

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  • IE browser caching and the jQuery Form Plugin

    - by Harfleur
    Like so many lost souls before me, I'm floundering in the snake pit that is Ajax form submission and IE browser caching. I'm trying to write a simple script using the jQuery Form Plugin to Ajaxify Wordpress comments. It's working fine in Firefox, Chrome, Safari, et. al., but in IE, the response text is cached with the result that Ajax is pulling in the wrong comment. jQuery(this).ajaxSubmit({ success: function(data) { var response = $("<ol>"+data+"</ol>"); response.find('.commentlist li:last').hide().appendTo(jQuery('.commentlist')).slideDown('slow'); } }); ajaxSubmit sends the comment to wp-comments-post.php, which inelegantly spits back the entire page as a response. So, despite the fact that it's ugly as toads, I'm sticking the response text in a variable, using :last to isolate the most recent comment, and sliding it down in its place. IE, however, is returning the cached version of the page, which doesn't include the new comment. So ".commentlist li:last" selects the previous comment, a duplicate of which then uselessly slides down beneath the original. I've tried setting "cache: false" in the ajaxSubmit options, but it has no effect. I've tried setting a url option and tacking on a random number or timestamp, but it winds up being attached to the POST that submits the comment to the server rather than the GET that returns the response, and so has no effect. I'm not sure what else to try. Everything works fine in IE if I turn off browser caching, but that's obviously not something I can expect anyone viewing the page to do. Any help will be hugely appreciated. Thanks in advance! EDIT WITH A PROGRESS REPORT: A couple of people have suggested using PHP headers to prevent caching, and this does indeed work. The trouble is that wp-comments-post is spitting back the entire page when a new comment is submitted, and the only way I can see to add headers is to put them in the Wordpress post template, which disables caching on all posts at all times--not quite the behavior I'm looking for. Is there a way to set a php conditional--"if is_ajax" or something like that--that would keep the headers from being applied during regular pageloads, but plug them in if the page was called by an Ajax GET?

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  • Can sorting Japanese kanji words be done programatically?

    - by Mason
    I've recently discovered, to my astonishment (having never really thought about it before), machine-sorting Japanese proper nouns is apparently not possible. I work on an application that must allow the user to select a hospital from a 3-menu interface. The first menu is Prefecture, the second is City Name, and the third is Hospital. Each menu should be sorted, as you might expect, so the user can find what they want in the menu. Let me outline what I have found, as preamble to my question: The expected sort order for Japanese words is based on their pronunciation. Kanji do not have an inherent order (there are tens of thousands of Kanji in use), but the Japanese phonetic syllabaries do have an order: ???????????????????... and on for the fifty traditional distinct sounds (a few of which are obsolete in modern Japanese). This sort order is called ???? (gojuu on jun , or '50-sound order'). Therefore, Kanji words should be sorted in the same order as they would be if they were written in hiragana. (You can represent any kanji word in phonetic hiragana in Japanese.) The kicker: there is no canonical way to determine the pronunciation of a given word written in kanji. You never know. Some kanji have ten or more different pronunciations, depending on the word. Many common words are in the dictionary, and I could probably hack together a way to look them up from one of the free dictionary databases, but proper nouns (e.g. hospital names) are not in the dictionary. So, in my application, I have a list of every prefecture, city, and hospital in Japan. In order to sort these lists, which is a requirement, I need a matching list of each of these names in phonetic form (kana). I can't come up with anything other than paying somebody fluent in Japanese (I'm only so-so) to manually transcribe them. Before I do so though: Is it possible that I am totally high on fire, and there actually is some way to do this sorting without creating my own mappings of kanji words to phonetic readings, that I have somehow overlooked? Is there a publicly available mapping of prefecture/city names, from the government or something? That would reduce the manual mapping I'd need to do to only hospital names. Does anybody have any other advice on how to approach this problem? Any programming language is fine--I'm working with Ruby on Rails but I would be delighted if I could just write a program that would take the kanji input (say 40,000 proper nouns) and then output the phonetic representations as data that I could import into my Rails app. ??????????

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  • Several client waiting for the same event

    - by ff8mania
    I'm developing a communication API to be used by a lot of generic clients to communicate with a proprietary system. This proprietary system exposes an API, and I use a particular classes to send and wait messages from this system: obviously the system alert me that a message is ready using an event. The event is named OnMessageArrived. My idea is to expose a simple SendSyncMessage(message) method that helps the user/client to simply send a message and the method returns the response. The client: using ( Communicator c = new Communicator() ) { response = c.SendSync(message); } The communicator class is done in this way: public class Communicator : IDisposable { // Proprietary system object ExternalSystem c; String currentRespone; Guid currentGUID; private readonly ManualResetEvent _manualResetEvent; private ManualResetEvent _manualResetEvent2; String systemName = "system"; String ServerName = "server"; public Communicator() { _manualResetEvent = new ManualResetEvent(false); //This methods are from the proprietary system API c = SystemInstance.CreateInstance(); c.Connect(systemName , ServerName); } private void ConnectionStarter( object data ) { c.OnMessageArrivedEvent += c_OnMessageArrivedEvent; _manualResetEvent.WaitOne(); c.OnMessageArrivedEvent-= c_OnMessageArrivedEvent; } public String SendSync( String Message ) { Thread _internalThread = new Thread(ConnectionStarter); _internalThread.Start(c); _manualResetEvent2 = new ManualResetEvent(false); String toRet; int messageID; currentGUID = Guid.NewGuid(); c.SendMessage(Message, "Request", currentGUID.ToString()); _manualResetEvent2.WaitOne(); toRet = currentRespone; return toRet; } void c_OnMessageArrivedEvent( int Id, string root, string guid, int TimeOut, out int ReturnCode ) { if ( !guid.Equals(currentGUID.ToString()) ) { _manualResetEvent2.Set(); ReturnCode = 0; return; } object newMessage; c.FetchMessage(Id, 7, out newMessage); currentRespone = newMessage.ToString(); ReturnCode = 0; _manualResetEvent2.Set(); } } I'm really noob in using waithandle, but my idea was to create an instance that sends the message and waits for an event. As soon as the event arrived, checks if the message is the one I expect (checking the unique guid), otherwise continues to wait for the next event. This because could be (and usually is in this way) a lot of clients working concurrently, and I want them to work parallel. As I implemented my stuff, at the moment if I run client 1, client 2 and client 3, client 2 starts sending message as soon as client 1 has finished, and client 3 as client 2 has finished: not what I'm trying to do. Can you help me to fix my code and get my target? Thanks!

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  • jquery event namespace bubbling issue

    - by Adrian Adkison
    Hi, I stumbled upon an issue with event namespacing while developing a jQuery plugin. here is the html <div class="parent"> <div class="child"> </div> </div> <a class="btn-a">trigger a</a> <a class="btn-b">trigger b</a> <a class="btn-c">trigger c</a> Here is the jQuery jQuery('#content div.child') .bind('child.a',function(){alert('a-child');}) .bind('child.b',function(){alert('b-child');}) .bind('child.c',function(){alert('c-child');}); jQuery('#content div.parent') .bind('child.b',function(){alert('b-parent');}) .bind('child.c',function(){alert('c-parent');}); jQuery('a.btn-a') .click(function(){ jQuery('#content div.child').trigger('a.a'); }); jQuery('a.btn-b') .click(function(){ jQuery('#content div.child').trigger('a.b'); }); jQuery('a.btn-c') .click(function(){ jQuery('#content div.child').trigger('a.c'); }); In sum, I have attached a namespaced event listener to the child and parent and created three buttons that trigger each of the events(a.a, a.b, a.c). Note the parent is only listening to a.b and a.c. When I click on the button that triggers a.a on the child, only the div.child listener for a.a is fired, but the entire 'a' namespace event bubbles up to div.parent listeners, a.b and a.c, and triggers them. My question is, how would I still use event namespacing but only have the intended event bubble up(i.e. a.a is the only event that fires for both child and parent). I am aware of stopPropagation and stopImmediatePropagation. I would not want to put these on the child a.b and a.c listeners because there are times when i do want them to bubble. For instance when I trigger 'a.b' on the child, I would expect the 'a.b' and only the 'a.b' event to be handled by the child and the parent. Thanks

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  • Remote Postgresql - extremely slow

    - by Muffinbubble
    Hi, I have setup PostgreSQL on a VPS I own - the software that accesses the database is a program called PokerTracker. PokerTracker logs all your hands and statistics whilst playing online poker. I wanted this accessible from several different computers so decided to installed it on my VPS and after a few hiccups I managed to get it connecting without errors. However, the performance is dreadful. I have done tons of research on 'remote postgresql slow' etc and am yet to find an answer so am hoping someone is able to help. Things to note: The query I am trying to execute is very small. Whilst connecting locally on the VPS, the query runs instantly. While running it remotely, it takes about 1 minute and 30 seconds to run the query. The VPS is running 100MBPS and then computer I'm connecting to it from is on an 8MB line. The network communication between the two is almost instant, I am able to remotely connect fine with no lag whatsoever and am hosting several websites running MSSQL and all the queries run instantly, whether connected remotely or locally so it seems specific to PostgreSQL. I'm running their newest version of the software and the newest compatible version of PostgreSQL with their software. The database is a new database, containing hardly any data and I've ran vacuum/analyze etc all to no avail, I see no improvements. I don't understand how MSSQL can query almost instantly yet PostgreSQL struggles so much. I am able to telnet to the post 5432 on the VPS IP with no problems, and as I say the query does execute it just takes an extremely long time. What I do notice is on the router when the query is running that hardly any bandwidth is being used - but then again I wouldn't expect it to for a simple query but am not sure if this is the issue. I've tried connecting remotely on 3 different networks now (including different routers) but the problem remains. Connecting remotely via another machine via the LAN is instant. I have also edited the postgre conf file to allow for more memory/buffers etc but I don't think this is the problem - what I am asking it to do is very simple - it shouldn't be intensive at all. Thanks, Ricky

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  • General ORM design question

    - by Calvin
    Suppose you have 2 classes, Person and Rabbit. A person can do a number of things to a rabbit, s/he can either feed it, buy it and become its owner, or give it away. A rabbit can have none or at most 1 owner at a time. And if it is not fed for a while, it may die. Class Person { Void Feed(Rabbit r); Void Buy(Rabbit r); Void Giveaway(Person p, Rabbit r); Rabbit[] rabbits; } Class Rabbit { Bool IsAlive(); Person pwner; } There are a couple of observations from the domain model: Person and Rabbit can have references to each other Any actions on 1 object can also change the state of the other object Even if no explicit actions are invoked, there can still be a change of state in the objects (e.g. Rabbit can be starved to death, and that causes it to be removed from the Person.rabbits array) As DDD is concerned, I think the correct approach is to synchronize all calls that may change the states in the domain model. For instance, if a Person buys a Rabbit, s/he would need to acquire a lock in Person to make a change to the rabbits array AND also another lock in Rabbit to change its owner before releasing the first one. This would prevent a race condition where 2 Persons claim to be the owner of the little Rabbit. The other approach is to let the database to handle all these synchronizations. Who makes the first call wins, but then the DB needs to have some kind of business logics to figure out if it is a valid transaction (e.g. if a Rabbit already has an owner, it cannot change its owner unless the Person gives it away). There are both pros/cons in either approach, and I’d expect the “best” solution would be somewhere in-between. How would you do it in real life? What’s your take and experience? Also, is it a valid concern that there can be another race condition the domain model has committed its change but before it is fully committed in the database? And for the 3rd observation (i.e. state change due to time factor). How will you do it?

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  • newbie problems with codeigniter

    - by Patrick
    hi, i'm trying to learn codeigniter (following a book) but don't understand why the web page comes out empty. my controller is class Welcome extends Controller { function Welcome() { parent::Controller(); } function index() { $data['title'] = "Welcome to Claudia's Kids"; $data['navlist'] = $this->MCats->getCategoriesNav(); $data['mainf'] = $this->MProducts->getMainFeature(); $skip = $data['mainf']['id']; $data['sidef'] = $this->MProducts->getRandomProducts(3, $skip); $data['main'] = "home"; $this->load->vars($data); $this->load->view('template'); } the view is: <--doctype declaration etc etc.. --> </head> <body> <div id="wrapper"> <div id="header"> <?php $this->load->view('header');?> </div> <div id='nav'> <?php $this->load->view('navigation');?> </div> <div id="main"> <?php $this->load->view($main);?> </div> <div id="footer"> <?php $this->load->view('footer');?> </div> </div> </body> </html> Now I know the model is passing back the right variables, but the page appears completely blank. I would expect at least to see an error, or the basic html structure, but the page is just empty. Moreover, the controller doesn't work even if I modify it as follows: function index() { echo "hello."; } What am I doing wrong? Everything was working until I made some changes to the model - but even if I delete all those new changes, the page is still blank.. i'm really confused! thanks, P.

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  • Using a map with set_intersection

    - by Robin Welch
    Not used set_intersection before, but I believe it will work with maps. I wrote the following example code but it doesn't give me what I'd expect: #include <map> #include <string> #include <iostream> #include <algorithm> using namespace std; struct Money { double amount; string currency; bool operator< ( const Money& rhs ) const { if ( amount != rhs.amount ) return ( amount < rhs.amount ); return ( currency < rhs.currency ); } }; int main( int argc, char* argv[] ) { Money mn[] = { { 2.32, "USD" }, { 2.76, "USD" }, { 4.30, "GBP" }, { 1.21, "GBP" }, { 1.37, "GBP" }, { 6.74, "GBP" }, { 2.55, "EUR" } }; typedef pair< int, Money > MoneyPair; typedef map< int, Money > MoneyMap; MoneyMap map1; map1.insert( MoneyPair( 1, mn[1] ) ); map1.insert( MoneyPair( 2, mn[2] ) ); map1.insert( MoneyPair( 3, mn[3] ) ); // (3) map1.insert( MoneyPair( 4, mn[4] ) ); // (4) MoneyMap map2; map1.insert( MoneyPair( 3, mn[3] ) ); // (3) map1.insert( MoneyPair( 4, mn[4] ) ); // (4) map1.insert( MoneyPair( 5, mn[5] ) ); map1.insert( MoneyPair( 6, mn[6] ) ); map1.insert( MoneyPair( 7, mn[7] ) ); MoneyMap out; MoneyMap::iterator out_itr( out.begin() ); set_intersection( map1.begin(), map1.end(), map2.begin(), map2.end(), inserter( out, out_itr ) ); cout << "intersection has " << out.size() << " elements." << endl; return 0; } Since the pair labelled (3) and (4) appear in both maps, I was expecting that I'd get 2 elements in the intersection, but no, I get: intersection has 0 elements. I'm sure this is something to do with the comparitor on the map / pair but can't figure it out.

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  • How to stream semi-live audio over internet

    - by Thomas Tempelmann
    I want to write something like Skype, i.e. I have a constant audio stream on one computer and then recompress it in a format that's suitable for a latent internet connection, receive it on the other end and play it. Let's also assume that the internet connection is fairly modern and fast, i.e. DSL or alike, no slow connections over phone and such. The involved computers will also be rather modern (Dual Core Intel CPUs at 2GHz or more). I know how to handle the audio on the machines. What I don't know is how to transmit the audio in an efficient way. The challenges are: I'd like get good audio quality across the line. The stream should be received without drops. The stream may, however, be received with a little delay (a second delay is acceptable). I imagine that the transport software could first determine the average (and max) latency, then start the stream and tell the receiver to wait for that max latency before starting to play the audio. With that, if the latency doesn't get any higher, the entire stream will be playable on the other side without stutter or drops. If, due to unexpected IP latencies or blockages, the stream does get cut off, I want to be able to notice this so that I can take actions (e.g. abort the stream) and eventually start a new transmission. What are my options if I want do use ready-made software for the compression and tranmission? I have no intention to write my own audio compression engine, really. OTOH, I plan to sell the solution in a vertical market, meaning I can afford a few dollars of license fees per copy, but not $100s. I guess the simplest solution would be to just open a TCP stream, send a few packets back and forth to determine their running time (or even use UDP for that), then use the results as the guide for my max latency value, then simply fire the audio data in its raw form (uncompressed 16 bit stereo), along with a timing code over the TCP connection. The receiver reads the data and plays it with the pre-determined delay. That might just work with the type of fast connection I expect. I just wonder if there are better solutions to reach this goal, with better performance (lower latency) and less data (compressed). BTW, I first try to implement this on OS X, but might want to do it on Windows, too, if it proves successful.

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  • Implementing coroutines in Java

    - by JUST MY correct OPINION
    This question is related to my question on existing coroutine implementations in Java. If, as I suspect, it turns out that there is no full implementation of coroutines currently available in Java, what would be required to implement them? As I said in that question, I know about the following: You can implement "coroutines" as threads/thread pools behind the scenes. You can do tricksy things with JVM bytecode behind the scenes to make coroutines possible. The so-called "Da Vinci Machine" JVM implementation has primitives that make coroutines doable without bytecode manipulation. There are various JNI-based approaches to coroutines also possible. I'll address each one's deficiencies in turn. Thread-based coroutines This "solution" is pathological. The whole point of coroutines is to avoid the overhead of threading, locking, kernel scheduling, etc. Coroutines are supposed to be light and fast and to execute only in user space. Implementing them in terms of full-tilt threads with tight restrictions gets rid of all the advantages. JVM bytecode manipulation This solution is more practical, albeit a bit difficult to pull off. This is roughly the same as jumping down into assembly language for coroutine libraries in C (which is how many of them work) with the advantage that you have only one architecture to worry about and get right. It also ties you down to only running your code on fully-compliant JVM stacks (which means, for example, no Android) unless you can find a way to do the same thing on the non-compliant stack. If you do find a way to do this, however, you have now doubled your system complexity and testing needs. The Da Vinci Machine The Da Vinci Machine is cool for experimentation, but since it is not a standard JVM its features aren't going to be available everywhere. Indeed I suspect most production environments would specifically forbid the use of the Da Vinci Machine. Thus I could use this to make cool experiments but not for any code I expect to release to the real world. This also has the added problem similar to the JVM bytecode manipulation solution above: won't work on alternative stacks (like Android's). JNI implementation This solution renders the point of doing this in Java at all moot. Each combination of CPU and operating system requires independent testing and each is a point of potentially frustrating subtle failure. Alternatively, of course, I could tie myself down to one platform entirely but this, too, makes the point of doing things in Java entirely moot. So... Is there any way to implement coroutines in Java without using one of these four techniques? Or will I be forced to use the one of those four that smells the least (JVM manipulation) instead?

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  • Looking for an Open Source Project in need of help

    - by hvidgaard
    Hi StackOverflow! I'm a CS student on well on my way to graduate. I have had a difficult time of finding relevant student jobs (they seems to be taken merely hours after the notice gets on the board) , so instead I'm looking for an open source project in need of help. I'm aware that I should choose one that I use, but I'm not aware of any OS-project that I use that needs help. That's why I'm asking you. I don't have any deep experience, but I here are some of my biggest projects so far: BitTorrent-ish client in Python (a subset of BitTorrent) HTTP 1.1 webserver in Java Compiler from a subset of Java to run on JRE Flash-framework project to model an iPad look and feel (not to run actual iPad programs) complete with an API for programs. Complete MySQL database for a booking system, with departure and arrival times, so you could only book valid tickets (with a Java frontend). I know, Java and languages like AS3 and C# feels natural per se, Python, and have done a fair bit of hacking around in C, but I don't feel very comfortable with it. Mostly I'm afraid to make a fuckup because I have such a high degree of control. I would like to think I'm well aware of good software design practices, but in reality what I do is ask myself "would I like to use/maintain this?", and I love to refactor my code because I see optimizations. I love algorithms and to make them run in the best possible time. I don't have any preferred domain to work in, but I wouldn't mind it to be graphics or math heavy. Ideally I'm looking for a project in C++ to learn the in's and out's of it, but I'm well aware that I don't know that language very well. I would like to have a mentor-like figure until I'm confident enough to stand on my own, not one to review all my code (I'm sure someone will to start with anyway), but to ask questions about the project and language in question. I do have a wife and two children, so don't expect me to put in 10+ hours every week. In return I can work on my own, I strive to program modular and maintainable code. Know how to read an API, use Google, StackOverflow and online resources in general. If you have any questions, shoot. I'm looking forward to your suggestions.

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  • Combining FileStream and MemoryStream to avoid disk accesses/paging while receiving gigabytes of data?

    - by w128
    I'm receiving a file as a stream of byte[] data packets (total size isn't known in advance) that I need to store somewhere before processing it immediately after it's been received (I can't do the processing on the fly). Total received file size can vary from as small as 10 KB to over 4 GB. One option for storing the received data is to use a MemoryStream, i.e. a sequence of MemoryStream.Write(bufferReceived, 0, count) calls to store the received packets. This is very simple, but obviously will result in out of memory exception for large files. An alternative option is to use a FileStream, i.e. FileStream.Write(bufferReceived, 0, count). This way, no out of memory exceptions will occur, but what I'm unsure about is bad performance due to disk writes (which I don't want to occur as long as plenty of memory is still available) - I'd like to avoid disk access as much as possible, but I don't know of a way to control this. I did some testing and most of the time, there seems to be little performance difference between say 10 000 consecutive calls of MemoryStream.Write() vs FileStream.Write(), but a lot seems to depend on buffer size and the total amount of data in question (i.e the number of writes). Obviously, MemoryStream size reallocation is also a factor. Does it make sense to use a combination of MemoryStream and FileStream, i.e. write to memory stream by default, but once the total amount of data received is over e.g. 500 MB, write it to FileStream; then, read in chunks from both streams for processing the received data (first process 500 MB from the MemoryStream, dispose it, then read from FileStream)? Another solution is to use a custom memory stream implementation that doesn't require continuous address space for internal array allocation (i.e. a linked list of memory streams); this way, at least on 64-bit environments, out of memory exceptions should no longer be an issue. Con: extra work, more room for mistakes. So how do FileStream vs MemoryStream read/writes behave in terms of disk access and memory caching, i.e. data size/performance balance. I would expect that as long as enough RAM is available, FileStream would internally read/write from memory (cache) anyway, and virtual memory would take care of the rest. But I don't know how often FileStream will explicitly access a disk when being written to. Any help would be appreciated.

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  • BufferedReader no longer buffering after a while?

    - by BobTurbo
    Sorry I can't post code but I have a bufferedreader with 50000000 bytes set as the buffer size. It works as you would expect for half an hour, the HDD light flashing every two minutes or so, reading in the big chunk of data, and then going quiet again as the CPU processes it. But after about half an hour (this is a very big file), the HDD starts thrashing as if it is reading one byte at a time. It is still in the same loop and I think I checked free ram to rule out swapping (heap size is default). Probably won't get any helpful answers, but worth a try. OK I have changed heap size to 768mb and still nothing. There is plenty of free memory and java.exe is only using about 300mb. Now I have profiled it and heap stays at about 200MB, well below what is available. CPU stays at 50%. Yet the HDD starts thrashing like crazy. I have.. no idea. I am going to rewrite the whole thing in c#, that is my solution. Here is the code (it is just a throw-away script, not pretty): BufferedReader s = null; HashMap<String, Integer> allWords = new HashMap<String, Integer>(); HashSet<String> pageWords = new HashSet<String>(); long[] pageCount = new long[78592]; long pages = 0; Scanner wordFile = new Scanner(new BufferedReader(new FileReader("allWords.txt"))); while (wordFile.hasNext()) { allWords.put(wordFile.next(), Integer.parseInt(wordFile.next())); } s = new BufferedReader(new FileReader("wikipedia/enwiki-latest-pages-articles.xml"), 50000000); StringBuilder words = new StringBuilder(); String nextLine = null; while ((nextLine = s.readLine()) != null) { if (a.matcher(nextLine).matches()) { continue; } else if (b.matcher(nextLine).matches()) { continue; } else if (c.matcher(nextLine).matches()) { continue; } else if (d.matcher(nextLine).matches()) { nextLine = s.readLine(); if (e.matcher(nextLine).matches()) { if (f.matcher(s.readLine()).matches()) { pageWords.addAll(Arrays.asList(words.toString().toLowerCase().split("[^a-zA-Z]"))); words.setLength(0); pages++; for (String word : pageWords) { if (allWords.containsKey(word)) { pageCount[allWords.get(word)]++; } else if (!word.isEmpty() && allWords.containsKey(word.substring(0, word.length() - 1))) { pageCount[allWords.get(word.substring(0, word.length() - 1))]++; } } pageWords.clear(); } } } else if (g.matcher(nextLine).matches()) { continue; } words.append(nextLine); words.append(" "); }

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  • Permanent mutex locking causing deadlock?

    - by Daniel
    I am having a problem with mutexes (pthread_mutex on Linux) where if a thread locks a mutex right again after unlocking it, another thread is not very successful getting a lock. I've attached test code where one mutex is created, along with two threads that in an endless loop lock the mutex, sleep for a while and unlock it again. The output I expect to see is "alive" messages from both threads, one from each (e.g. 121212121212. However what I get is that one threads gets the majority of locks (e.g. 111111222222222111111111 or just 1111111111111...). If I add a usleep(1) after the unlocking, everything works as expected. Apparently when the thread goes to SLEEP the other thread gets its lock - however this is not the way I was expecting it, as the other thread has already called pthread_mutex_lock. I suspect this is the way this is implemented, in that the actice thread has priority, however it causes certain problem in this particular testcase. Is there any way to prevent it (short of adding a deliberately large enough delay or some kind of signaling) or where is my error in understanding? #include <pthread.h> #include <stdio.h> #include <string.h> #include <sys/time.h> #include <unistd.h> pthread_mutex_t mutex; void* threadFunction(void *id) { int count=0; while(true) { pthread_mutex_lock(&mutex); usleep(50*1000); pthread_mutex_unlock(&mutex); // usleep(1); ++count; if (count % 10 == 0) { printf("Thread %d alive\n", *(int*)id); count = 0; } } return 0; } int main() { // create one mutex pthread_mutexattr_t attr; pthread_mutexattr_init(&attr); pthread_mutex_init(&mutex, &attr); // create two threads pthread_t thread1; pthread_t thread2; pthread_attr_t attributes; pthread_attr_init(&attributes); int id1 = 1, id2 = 2; pthread_create(&thread1, &attributes, &threadFunction, &id1); pthread_create(&thread2, &attributes, &threadFunction, &id2); pthread_attr_destroy(&attributes); sleep(1000); return 0; }

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  • Flex bug?? Get messed up stacked ColumnChart with type="100%"

    - by Nir
    I am trying to do a stacked Column chart with type="100%" and a mixture of positive and negative values. When all the values are positive, is functions well, but when negative numbers come to the game, it looks totally messed up. When I also look at Adobe documentation (look here), I see the following code for stacked column chart involving negative numbers: <?xml version="1.0"?> <!-- charts/StackedNegative.mxml --> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:Script><![CDATA[ import mx.collections.ArrayCollection; [Bindable] public var expenses:ArrayCollection = new ArrayCollection([ {Month:"Jan", Profit:-2000, Expenses:-1500}, {Month:"Feb", Profit:1000, Expenses:-200}, {Month:"Mar", Profit:1500, Expenses:-500} ]); ]]></mx:Script> <mx:Panel title="Column Chart"> <mx:ColumnChart id="myChart" dataProvider="{expenses}" showDataTips="true"> <mx:horizontalAxis> <mx:CategoryAxis dataProvider="{expenses}" categoryField="Month" /> </mx:horizontalAxis> <mx:series> <mx:ColumnSet type="stacked" allowNegativeForStacked="true"> <mx:series> <mx:ColumnSeries xField="Month" yField="Profit" displayName="Profit" /> <mx:ColumnSeries xField="Month" yField="Expenses" displayName="Expenses" /> </mx:series> </mx:ColumnSet> </mx:series> </mx:ColumnChart> <mx:Legend dataProvider="{myChart}"/> </mx:Panel> </mx:Application> It works fine. But try to change: <mx:ColumnSet type="stacked" allowNegativeForStacked="true"> to: <mx:ColumnSet type="100%" allowNegativeForStacked="true"> and you'll see that it doesn't on January data, where both values are negative, the chart shows as if they are positive, and on the other two where one value is positive and the other is negative, it shows only the positive part as 100%... Isn't it a Flex Bug? I have my own case with such data and it behaves wrong the same way. I'd expect that if it has 800 stacked on -200, it will show 80% up and 20% down, totalling 100%. BTW: Using Flex 4, though these are all mx components. Thanks a lot and regards from Berlin, Germany, Nir.

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  • git: setting a single tracking remote from a public repo.

    - by Gauthier
    I am confused with remote branches. My local repo: (local) ---A---B---C-master My remote repo (called int): (int) ---A---B---C---D---E-master What I want to do is to setup the local repo's master branch to follow that of int. Local repo: (local) ---A---B---C---D---E-master-remotes/int/master So that when int changes to: (int) ---A---B---C---D---E---F-master I can run git pull from the local repo's master and get (local) ---A---B---C---D---E---F-master-remotes/int/master Here's what I have tried: git fetch int gets me all the branches of int into remote branches. This can get messy since int might have hundreds of branches. git fetch int master gets me the commits, but no ref to it, only FETCH_HEAD. No remote branch either. git fetch int master:new_master works but I don't want a new name every time I update, and no remote branch is setup. git pull int master does what I want, but there is still no remote branch setup. I feel that it is ok to do so (that's the best I have now), but I read here and there that with the remote setup it is enough with git pull. git branch --track new_master int/master, as per http://www.gitready.com/beginner/2009/03/09/remote-tracking-branches.html . I get "not a valid object name: int/master". git remote -v does show me that int is defined and points at the correct location (1. worked). What I miss is the int/master branch, which is precisely what I want to get. git fetch in master:int/master. Well, int/master is created, but is no remote. So to summarize, I've tried some stuff with no luck. I would expect 2 to give me the remote branch to master in the repo int. The solution I use now is option 3. I read somewhere that you could change some config file by hand, but isn't that a bit cumbersome? The "cumbersome" way of editting the config file did work: [branch "master"] remote = int merge = master It can be done from command line: $ git config branch.master.remote int $ git config branch.master.merge master Any reason why option 2 above wouldn't do that automatically? Even in that case, git pull fetches all branches from the remote.

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  • Simple Modal with Autocomplete in ASP.NET

    - by DanielJaymes
    Hello, I am quite new to this so any help is very much appreciated. I am generating a modal pop using Simple Modal, this works ok. I now want to add jquery autocomplete to the element txtEmail. When I run the page outside of Simple Modal I can use Autocomplete, however when the page is loaded through Simple Modal it does not work. I have checked to ensure the element is loaded, and it is allowing me to change the text color, but I can not add autocomplete to it. The code is /** * @author Daniel */ jQuery(function($) { $("input.ema, a.ema").click(function(e) { e.preventDefault(); $("#osx-modal-content").modal({ appendTo: 'form', overlayId: 'osx-overlay', containerId: 'osx-container', closeHTML: '<div class="close"><a href="#" class="simplemodal-close">X</a></div>', minHeight: 80, opacity: 65, position: ['0', ], overlayClose: true, onOpen: OSX.open, onClose: OSX.close, onShow: OSX.show }); }); var OSX = { container: null, open: function(d) { var self = this; $.ajax({ url: "/Message/UserMessage/", type: 'GET', dataType: 'html', // <-- to expect an html response success: function(result) { var data = "Core Selectors Attributes Traversing Manipulation CSS Events Effects Ajax Utilities".split(" "); $('div#osx-modal-data').html(result).find("#txtEmail").css('color', '#c00'); if ($('div#osx-modal-data').find("#txtEmail").length) { // implies *not* zero $('div#osx-modal-data').find("#txtEmail").autocomplete(data); alert('We found img elements on the page using "img"'); } else { alert('No txtEmail elements found'); } } }); self.container = d.container[0]; d.overlay.fadeIn('slow', function() { $("#osx-modal-content", self.container).show(); $('div#osx-modal-title').html("Send Email"); var title = $("#osx-modal-title", self.container); title.show(); d.container.slideDown('slow', function() { setTimeout(function() { var h = $("#osx-modal-data", self.container).height() + title.height() + 20; // padding d.container.animate({ height: h }, 200, function() { $("div.close", self.container).show(); $("#osx-modal-data", self.container).show(); }); }, 300); }); }) }, close: function(d) { var self = this; d.container.animate({ top: "-" + (d.container.height() + 20) }, 500, function() { self.close(); // or $.modal.close(); }); }, show: function(d) { // $('div#osx-modal-data').find("#txtEmail").css('color', '#ccc') } }; });

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  • Can't figure out the color of an svg element

    - by yass
    I have a very simple HTML page, viewable on gh-pages with the following code: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <link href="style.css" media="screen" rel="stylesheet" type="text/css"> <script src='http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js'> </script> </head> <body> <div id="page"> <div id="content"> <div id="heatmap"> <svg style="margin-left: 80px; color: rgb(255, 255, 255);" width="800" height="880"> <g transform="translate(80,80)"> <rect style="color: rgb(255, 255, 255);" height="720" width="720"> </rect> </g> </svg> </div> </div> </div> </body> </html> with the following CSS: body { background-color: #FFFFFF; font-family: Arial, Helvetica, sans-serif; font-size: 14px; color: #FFFFFF; } #wrapper { margin: 0 auto; padding: 0; } #page { width: 1000px; margin: 0 auto; padding: 40px 0px 0px 0px; } #content { float: left; width: 660px; padding: 0px 0px 0px 0px; background: #FFFFFF; } I expect the rectangle, 'svg rect' to be the color #FFFFFF, or white. But it shows up as some other color. I opened it up in firebug, and it shows the computed color to be #FFFFF:

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  • Ruby/Rails - Add records to an object with each loop iteration / Object vs Arrays

    - by ChrisWesAllen
    I'm trying to figure out how to add records to an existing object for each iteration of a loop. I'm having a hard time discovering the difference between an object and an array. I have this @events = Event.find(1) @loops = Choices.find(:all, :limit => 5) #so loop for 5 instances of choice model for loop in @loops @events = Event.find(:all,:conditions => ["event.id = ?", loop.event_id ]) end I'm trying to add a new events to the existing @events object based on the id of whatever the loop variable is. But the ( = ) operator just creates a new instance of the @events object. I tried ( += ) and ( << ) as operators but got the error "You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil" I tried created an array events = [] events << Event.find(1) @loops = Choices.find(:all, :limit => 5) #so loop for 5 instances of choice model for loop in @loops events << Event.find(:all,:conditions => ["event.id = ?", loop.event_id ]) end But I dont know how to call that arrays attributes within the view With objects I was able do create a loop within the view and call all the attributes of that object as well... <table> <% for event in @events %> <tr> <td><%= link_to event.title, event %></td> <td><%= event.start_date %></td> <td><%= event.price %></td> </tr> <% end %> </table> How could i do this with an array set? So the questions are 1) Whats the difference between arrays and objects? 2) Is there a way to add into the existing object for each iteration? 3) If I use an array, is there a way to call the attributes for each array record within the view?

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  • Race condition for thread startup

    - by Ozzah
    A similar question was asked here, but the answers generally all seem to relate to the lambda notation. I get a similar result without the lambda so I thought I'd ask for some clarification: Say I have something like this: for (int i = 0; i < 5; i++) (new Thread(new ThreadStart(delegate() { Console.WriteLine("Thread " + i); }))).Start(); One would expect the following output: Thread 0 Thread 1 Thread 2 Thread 3 Thread 4 Now I realise that the threads aren't started in any particular order, so let's just assume that the above lines can come out in any order. But that is not what happens. What instead happens: Thread 3 Thread 4 Thread 4 Thread 4 Thread 4 or something similar, which leads me to believe that rather than passing the value if i, it is passing the reference. (Which is weird, since an int is a value type). Doing something like this: for (int i = 0; i < 5; i++) (new Thread(new ThreadStart(delegate() { int j = i; Console.WriteLine("Thread " + j); }))).Start(); does not help either, even though we have made a copy of i. I am assuming the reason is that it hasn't made a copy of i in time. Doing something like this: for (int i = 0; i < 5; i++) { (new Thread(new ThreadStart(delegate() { Console.WriteLine("Thread " + i); }))).Start(); Thread.Sleep(50); } seems to fix the problem, however it is extremely undesirable as we're wasting 50ms on each iteration, not to mention the fact that if the computer is heavily loaded then maybe 50ms may not be enough. Here is a sample with my current, specific problem: Thread t = new Thread(new ThreadStart(delgate() { threadLogic(param1, param2, param3, param4); })); t.Start(); param1 = param2 = param3 = param4 = null; with: void threadLogic(object param1, object param2, object param3, object param4) { // Do some stuff here... } I want threadLogic() to run in its own thread, however the above code gives a null reference exception. I assume this is because the values are set to null before the thread has had a chance to start. Again, putting a Thread.Sleep(100) works, but it is an awful solution from every aspect. What do you guys recommend for this particular type of race condition?

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  • How do I use Ruby metaprogramming to refactor this common code?

    - by James Wenton
    I inherited a project with a lot of badly-written Rake tasks that I need to clean up a bit. Because the Rakefiles are enormous and often prone to bizarre nonsensical dependencies, I'm simplifying and isolating things a bit by refactoring everything to classes. Specifically, that pattern is the following: namespace :foobar do desc "Frozz the foobar." task :frozzify do unless Rake.application.lookup('_frozzify') require 'tasks/foobar' Foobar.new.frozzify end Rake.application['_frozzify'].invoke end # Above pattern repeats many times. end # Several namespaces, each with tasks that follow this pattern. In tasks/foobar.rb, I have something that looks like this: class Foobar def frozzify() # The real work happens here. end # ... Other tasks also in the :foobar namespace. end For me, this is great, because it allows me to separate the task dependencies from each other and to move them to another location entirely, and I've been able to drastically simplify things and isolate the dependencies. The Rakefile doesn't hit a require until you actually try to run a task. Previously this was causing serious issues because you couldn't even list the tasks without it blowing up. My problem is that I'm repeating this idiom very frequently. Notice the following patterns: For every namespace :xyz_abc, there is a corresponding class in tasks/... in the file tasks/[namespace].rb, with a class name that looks like XyzAbc. For every task in a particular namespace, there is an identically named method in the associated namespace class. For example, if namespace :foo_bar has a task :apples, you would expect to see def apples() ... inside the FooBar class, which itself is in tasks/foo_bar.rb. Every task :t defines a "meta-task" _t (that is, the task name prefixed with an underscore) which is used to do the actual work. I still want to be able to specify a desc-description for the tasks I define, and that will be different for each task. And, of course, I have a small number of tasks that don't follow the above pattern at all, so I'll be specifying those manually in my Rakefile. I'm sure that this can be refactored in some way so that I don't have to keep repeating the same idiom over and over, but I lack the experience to see how it could be done. Can someone give me an assist?

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