writing - Page 437 - Developer IT

Core-Data + AFNetworking + UI Updating (Responsiveness)

- by Mustafa

Here's the scenario: I'm writing a DownloadManager, that allows the user to download, pause, cancel, download all, and pause all. The DownloadManager is a singleton, and uses AFNetworking to download files. It has it's own private managed object context, so that user can freely use other parts of the application (by adding, editing, deleting) core-data objects. I have a core-data entity DownloadInfo that stores the download information i.e. fileURL, fileSize, bytesRead, etc. The DownloadManager updates the download progress in DownloadInfo (one for each file). I have a DownloadManagerViewController which uses NSFetchedResultsController to show the download status to the user. This download view controller is using the main managed object context. Now let's say that I have 20 files in the download queue. And let's say that only 3 concurrent downloads are allowed. The download manager should download the file, and show the download progress. Problem: The DownloadInfo objects are being updated by the DownloadManager at a very high rate. The DownloadManagerViewController (responsible for showing the download progress) is updating the list using NSFetchedResultsControllerDelegate methods. The result is that a lot is happening in the main queue and application has very poor responsiveness. How can I fix this? How can I make the application responsive, while showing the download progress? I don't know how else to communicate that the download status between DownloadManager and DownloadManagerViewController. Is there another/ a better way to do this? I don't want to use main managed object context in my DownloadManager, for reasons mentioned above. Note, that the DownloadManager is using AFNetworking which is handling the requests asynchronously, but eventually the DownloadInfo objects are updated in the main thread (as a result of the callback methods). Maybe there's a way to handle the downloads and status update operations in a background thread? but how? How will I communicate between the main thread and the background thread i.e. how will I tell the background thread to queue another file for download? Thanks.

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Performance of tokenizing CSS in PHP

- by Boldewyn

This is a noob question from someone who hasn't written a parser/lexer ever before. I'm writing a tokenizer/parser for CSS in PHP (please don't repeat with 'OMG, why in PHP?'). The syntax is written down by the W3C neatly here (CSS2.1) and here (CSS3, draft). It's a list of 21 possible tokens, that all (but two) cannot be represented as static strings. My current approach is to loop through an array containing the 21 patterns over and over again, do an if (preg_match()) and reduce the source string match by match. In principle this works really good. However, for a 1000 lines CSS string this takes something between 2 and 8 seconds, which is too much for my project. Now I'm banging my head how other parsers tokenize and parse CSS in fractions of seconds. OK, C is always faster than PHP, but nonetheless, are there any obvious D'Oh! s that I fell into? I made some optimizations, like checking for '@', '#' or '"' as the first char of the remaining string and applying only the relevant regexp then, but this hadn't brought any great performance boosts. My code (snippet) so far: $TOKENS = array( 'IDENT' => '...regexp...', 'ATKEYWORD' => '@...regexp...', 'String' => '"...regexp..."|\'...regexp...\'', //... ); $string = '...CSS source string...'; $stream = array(); // we reduce $string token by token while ($string != '') { $string = ltrim($string, " \t\r\n\f"); // unconsumed whitespace at the // start is insignificant but doing a trim reduces exec time by 25% $matches = array(); // loop through all possible tokens foreach ($TOKENS as $t => $p) { // The '&' is used as delimiter, because it isn't used anywhere in // the token regexps if (preg_match('&^'.$p.'&Su', $string, $matches)) { $stream[] = array($t, $matches[0]); $string = substr($string, strlen($matches[0])); // Yay! We found one that matches! continue 2; } } // if we come here, we have a syntax error and handle it somehow } // result: an array $stream consisting of arrays with // 0 => type of token // 1 => token content

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C++: Implementing Named Pipes using the Win32 API

- by Mike Pateras

I'm trying to implement named pipes in C++, but either my reader isn't reading anything, or my writer isn't writing anything (or both). Here's my reader: int main() { HANDLE pipe = CreateFile(GetPipeName(), GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL); char data[1024]; DWORD numRead = 1; while (numRead >= 0) { ReadFile(pipe, data, 1024, &numRead, NULL); if (numRead > 0) cout << data; } return 0; } LPCWSTR GetPipeName() { return L"\\\\.\\pipe\\LogPipe"; } And here's my writer: int main() { HANDLE pipe = CreateFile(GetPipeName(), GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL); string message = "Hi"; WriteFile(pipe, message.c_str(), message.length() + 1, NULL, NULL); return 0; } LPCWSTR GetPipeName() { return L"\\\\.\\pipe\\LogPipe"; } Does that look right? numRead in the reader is always 0, for some reason, and it reads nothing but 1024 -54's (some weird I character). Solution: Reader (Server): while (true) { HANDLE pipe = CreateNamedPipe(GetPipeName(), PIPE_ACCESS_INBOUND | PIPE_ACCESS_OUTBOUND , PIPE_WAIT, 1, 1024, 1024, 120 * 1000, NULL); if (pipe == INVALID_HANDLE_VALUE) { cout << "Error: " << GetLastError(); } char data[1024]; DWORD numRead; ConnectNamedPipe(pipe, NULL); ReadFile(pipe, data, 1024, &numRead, NULL); if (numRead > 0) cout << data << endl; CloseHandle(pipe); } Writer (client): HANDLE pipe = CreateFile(GetPipeName(), GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL); if (pipe == INVALID_HANDLE_VALUE) { cout << "Error: " << GetLastError(); } string message = "Hi"; cout << message.length(); DWORD numWritten; WriteFile(pipe, message.c_str(), message.length(), &numWritten, NULL); return 0; The server blocks until it gets a connected client, reads what the client writes, and then sets itself up for a new connection, ad infinitum. Thanks for the help, all!

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architecture python question

- by tom smith

hi. creating a distributed crawling python app. it consists of a master server, and associated client apps that will run on client servers. the purpose of the client app is to run across a targeted site, to extract specific data. the clients need to go "deep" within the site, behind multiple levels of forms, so each client is specifically geared towards a given site. each client app looks something like main: parse initial url call function level1 (data1) function level1 (data) parse the url, for data1 use the required xpath to get the dom elements call the next function call level2 (data) function level2 (data2) parse the url, for data2 use the required xpath to get the dom elements call the next function call level3 function level3 (dat3) parse the url, for data3 use the required xpath to get the dom elements call the next function call level4 function level4 (data) parse the url, for data4 use the required xpath to get the dom elements at the final function.. --all the data output, and eventually returned to the server --at this point the data has elements from each function... my question: given that the number of calls that is made to the child function by the current function varies, i'm trying to figure out the best approach. each function essentialy fetches a page of content, and then parses the page using a number of different XPath expressions, combined with different regex expressions depending on the site/page. if i run a client on a single box, as a sequential process, it'll take awhile, but the load on the box is rather small. i've thought of attempting to implement the child functions as threads from the current function, but that could be a nightmare, as well as quickly bring the "box" to its knees! i've thought of breaking the app up in a manner that would allow the master to essentially pass packets to the client boxes, in a way to allow each client/function to be run directly from the master. this process requires a bit of rewrite, but it has a number of advantages. a bunch of redundancy, and speed. it would detect if a section of the process was crashing and restart from that point. but not sure if it would be any faster... i'm writing the parsing scripts in python.. so... any thoughts/comments would be appreciated... i can get into a great deal more detail, but didn't want to bore anyone!! thanks! tom

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Re-Centering JQuery Tooltips when resizing the window

- by leeand00

I have written a function that positions a tooltip just above a textbox. The function takes two arguments: textBoxId - The ID of the textbox above which the tooltip will appear. Example: "#textBoxA" toolTipId - The ID of the tooltip which will appear above the textbox. Example: "#toolTipA" function positionTooltip(textBoxId, toolTipId){ var hoverElementOffsetLeft = $(textBoxId).offset().left; var hoverElementOffsetWidth = $(textBoxId)[0].offsetWidth; var toolTipElementOffsetLeft = $(toolTipId).offset().left; var toolTipElementOffsetWidth = $(toolTipId)[0].offsetWidth; // calcluate the x coordinate of the center of the hover element. var hoverElementCenterX = hoverElementOffsetLeft + (hoverElementOffsetWidth / 2); // calculate half the width of the toolTipElement var toolTipElementHalfWidth = toolTipElementOffsetWidth / 2; var toolTipElementLeft = hoverElementCenterX - toolTipElementHalfWidth; $(toolTipId)[0].style.left = toolTipElementLeft + "px"; var toolTipElementHeight = $(toolTipId)[0].offsetHeight; var hoverElementOffsetTop = $(textBoxId).offset().top; var toolTipYCoord = hoverElementOffsetTop - toolTipElementHeight; toolTipYCoord = toolTipYCoord - 10; $(toolTipId)[0].style.top = toolTipYCoord + "px"; $(toolTipId).hide(); $(textBoxId).hover( function(){ $(toolTipId + ':hidden').fadeIn(); }, function(){ $(toolTipId + ':visible').fadeOut(); } ); $(textBoxId).focus ( function(){ $(toolTipId + ':hidden').fadeIn(); } ); $(textBoxId).blur ( function(){ $(toolTipId+ ':visible').fadeOut(); } ); } The function works fine upon initial page load: However, after the user resizes the window the tooltips move to locations that no longer display above their associated textbox. I've tried writing some code to fix the problem by calling the positionTooltip() function when the window is resized but for some reason the tooltips do not get repositioned as they did when the page loaded: var _resize_timer = null; $(window).resize(function() { if (_resize_timer) {clearTimeout(_resize_timer);} _resize_timer = setTimeout(function(){ positionTooltip('#textBoxA', ('#toolTipA')); }, 1000); }); I'm really at a loss here as to why it doesn't reposition the tooltip correctly as it did when the page was initially loaded after a resize.

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What was "The Next Big Thing" when you were just starting out in programming?

- by Andrew

I'm at the beginning of my career and there are lots of things which are being touted as "The Next Big Thing". For example: Dependency Injection (Spring, etc) MVC (Struts, ASP.NET MVC) ORMs (Linq To SQL, Hibernate) Agile Software Development These things have probably been around for some time, but I've only just started out. And don't get me wrong, I think these things are great! So, what was "The Next Big Thing" when you were starting out? When was it? Were people sceptical of it at first? Why? Did you think it would catch on? Did it pan out and become widely accepted/used? If not, why not? EDIT It's been nearly a week since I first posted this question and I can safely say that I did not expect such explosive interest. I asked the question so that I could gain a perspective of what kinds of innovations in programming people thought were most important when they were starting out. At the time of writing this I have read ~95% of all answers. To answer a few questions, the "Next Big Things" I listed are ones that I am currently really excited about and that I had not really been exposed to until I started working. I'm hoping to implement some or all of these in the near future at my current workplace. To many people they are probably old news. In regards to the "is this a real question" debate, I can see that obviously hasn't been settled yet. I feel bad whenever I read a comment saying that these kinds of questions take away from the real meaning of SO. I'm not wholly convinced that it doesn't. On the other hand, I have seen a lot of comments saying what a great question it is. Anyway, I have chosen "The Internet!" as my answer to this question. I don't think (in my very humble opinion, and, it seems many SOers opinions) that many things related to programming can compare. Nowadays every business and their dog has a website which can do anything from simply supplying information to purchasing goods halfway around the world to updating your blog. And of course, all these businesses need people like us. Thanks to everyone for all the great answers!

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Java: Reading a pdf file from URL into Byte array/ByteBuffer in an applet.

- by Pol

I'm trying to figure out why this particular snippet of code isn't working for me. I've got an applet which is supposed to read a .pdf and display it with a pdf-renderer library, but for some reason when I read in the .pdf files which sit on my server, they end up as being corrupt. I've tested it by writing the files back out again. I've tried viewing the applet in both IE and Firefox and the corrupt files occur. Funny thing is, when I trying viewing the applet in Safari (for Windows), the file is actually fine! I understand the JVM might be different, but I am still lost. I've compiled in Java 1.5. JVMs are 1.6. The snippet which reads the file is below. public static ByteBuffer getAsByteArray(URL url) throws IOException { ByteArrayOutputStream tmpOut = new ByteArrayOutputStream(); URLConnection connection = url.openConnection(); int contentLength = connection.getContentLength(); InputStream in = url.openStream(); byte[] buf = new byte[512]; int len; while (true) { len = in.read(buf); if (len == -1) { break; } tmpOut.write(buf, 0, len); } tmpOut.close(); ByteBuffer bb = ByteBuffer.wrap(tmpOut.toByteArray(), 0, tmpOut.size()); //Lines below used to test if file is corrupt //FileOutputStream fos = new FileOutputStream("C:\\abc.pdf"); //fos.write(tmpOut.toByteArray()); return bb; } I must be missing something, and I've been banging my head trying to figure it out. Any help is greatly appreciated. Thanks. Edit: To further clarify my situation, the difference in the file before I read then with the snippet and after, is that the ones I output after reading are significantly smaller than they originally are. When opening them, they are not recognized as .pdf files. There are no exceptions being thrown that I ignore, and I have tried flushing to no avail. This snippet works in Safari, meaning the files are read in it's entirety, with no difference in size, and can be opened with any .pdf reader. In IE and Firefox, the files always end up being corrupted, consistently the same smaller size. I monitored the len variable (when reading a 59kb file), hoping to see how many bytes get read in at each loop. In IE and Firefox, at 18kb, the in.read(buf) returns a -1 as if the file has ended. Safari does not do this. I'll keep at it, and I appreciate all the suggestions so far.

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Recursive XSLT, part 2

- by Eric

Ok, following on from my question here. Lets say my pages are now like this: A.xml: <page> <header>Page A</header> <content-a>Random content for page A</content-a> <content-b>More of page A's content</content-b> <content-c>More of page A's content</content-c>  </page> B.xml: <page include="A.xml"> <header>Page B</header> <content-a>Random content for page B</content-a> <content-b>More of page B's content</content-b> <content-c>More of page B's content</content-c> </page> C.xml: <page include="B.xml"> <header>Page C</header> <content-a>Random content for page C</content-a> <content-b>More of page C's content</content-b> <content-c>More of page C's content</content-c> </page> After the transform (on C.xml), I'd like to end up with this: <h1>Page C</h1> <div> <p>Random content for page C</p> <p>Random content for page B</p> <p>Random content for page A</p> </div> <div> <p>More of page C's content</p> <p>More of page B's content</p> <p>More of page A's content</p> </div> <div> <p>Yet more of page C's content</p> <p>Yet more of page B's content</p> <p>Yet more of page A's content</p> </div> I know that I can use document(@include) to include another document. However, the recursion is a bit beyond me. How would I go about writing such a transform?

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Storing simulation results in a persistent manner for Python?

- by Az

Background: I'm running multiple simuations on a set of data. For each session, I'm allocating projects to students. The difference between each session is that I'm randomising the order of the students such that all the students get a shot at being assigned a project they want. I was writing out some of the allocations in a spreadsheet (i.e. Excel) and it basically looked like this (tiny snapshot, actual table extends to a few thousand sessions, roughly 100 students). | | Session 1 | Session 2 | Session 3 | |----------|-----------|-----------|-----------| |Stu1 |Proj_AA |Proj_AB |Proj_AB | |----------|-----------|-----------|-----------| |Stu2 |Proj_AB |Proj_AA |Proj_AC | |----------|-----------|-----------|-----------| |Stu3 |Proj_AC |Proj_AC |Proj_AA | |----------|-----------|-----------|-----------| Now, the code that deals with the allocation currently stores a session in an object. The next time the allocation is run, the object is over-written. Thus what I'd really like to do is to store all the allocation results. This is important since I later need to derive from the data, information such as: which project Stu1 got assigned to the most or perhaps how popular Proj_AC was (how many times it was assigned / number of sessions). Question(s): What methods can I possibly use to basically store such session information persistently? Basically, each session output needs to add itself to the repository after ending and before beginning the next allocation cycle. One solution that was suggested by a friend was mapping these results to a relational database using SQLAlchemy. I kind of like the idea since this does give me an opportunity to delve into databases. Now the database structure I was recommended was: |----------|-----------|-----------| |Session |Student |Project | |----------|-----------|-----------| |1 |Stu1 |Proj_AA | |----------|-----------|-----------| |1 |Stu2 |Proj_AB | |----------|-----------|-----------| |1 |Stu3 |Proj_AC | |----------|-----------|-----------| |2 |Stu1 |Proj_AB | |----------|-----------|-----------| |2 |Stu2 |Proj_AA | |----------|-----------|-----------| |2 |Stu3 |Proj_AC | |----------|-----------|-----------| |3 |Stu1 |Proj_AB | |----------|-----------|-----------| |3 |Stu2 |Proj_AC | |----------|-----------|-----------| |3 |Stu3 |Proj_AA | |----------|-----------|-----------| Here, it was suggested that I make the Session and Student columns a composite key. That way I can access a specific record for a particular student for a particular session. Or I can merely get the entire allocation run for a particular session. Questions: Is the idea a good one? How does one implement and query a composite key using SQLAlchemy? What happens to the database if a particular student is not assigned a project (happens if all projects that he wants are taken)? In the code, if a student is not assigned a project, instead of a proj_id he simply gets None for that field/object. I apologise for asking multiple questions but since these are closely-related, I thought I'd ask them in the same space.

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Data access pattern, combining push and pull?

- by andlju

I need some advice on what kind of pattern(s) I should use for pushing/pulling data into my application. I'm writing a rule-engine that needs to hold quite a large amount of data in-memory in order to be efficient enough. I have some rather conflicting requirements; It is not acceptable for the engine to always have to wait for a full pre-load of all data before it is functional. Only fetching and caching data on-demand will lead to the engine taking too long before it is running quickly enough. An external event can trigger the need for specific parts of the data to be reloaded. Basically, I think I need a combination of pushing and pulling data into the application. A simplified version of my current "pattern" looks like this (in psuedo-C# written in notepad): // This interface is implemented by all classes that needs the data interface IDataSubscriber { void RegisterData(Entity data); } // This interface is implemented by the data access class interface IDataProvider { void EnsureLoaded(Key dataKey); void RegisterSubscriber(IDataSubscriber subscriber); } class MyClassThatNeedsData : IDataSubscriber { IDataProvider _provider; MyClassThatNeedsData(IDataProvider provider) { _provider = provider; _provider.RegisterSubscriber(this); } public void RegisterData(Entity data) { // Save data for later StoreDataInCache(data); } void UseData(Key key) { // Make sure that the data has been stored in cache _provider.EnsureLoaded(key); Entity data = GetDataFromCache(key); } } class MyDataProvider : IDataProvider { List<IDataSubscriber> _subscribers; // Make sure that the data for key has been loaded to all subscribers public void EnsureLoaded(Key key) { if (HasKeyBeenMarkedAsLoaded(key)) return; PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } // Force all subscribers to get a new version of the data for key public void ForceReload(Key key) { PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } void PublishDataToSubscribers(Key key) { Entity data = FetchDataFromStore(key); foreach(var subscriber in _subscribers) { subscriber.RegisterData(data); } } } // This class will be spun off on startup and should make sure that all data is // preloaded as quickly as possible class MyPreloadingThread { IDataProvider _provider; MyPreloadingThread(IDataProvider provider) { _provider = provider; } void RunInBackground() { IEnumerable<Key> allKeys = GetAllKeys(); foreach(var key in allKeys) { _provider.EnsureLoaded(key); } } } I have a feeling though that this is not necessarily the best way of doing this.. Just the fact that explaining it seems to take two pages feels like an indication.. Any ideas? Any patterns out there I should have a look at?

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sql to xml using linq - nested collections

- by nelsonwebs

I have a table of data that looks something like this. name, hour, price1, price2, price3, price4, price5 fred, 3, 12.5, 13.5, 14, 15, 16 dave, 6, 8, 12, 18, 20.2, 25 fred, 6, 10, 11, 14, 15, 19.7 This table needs to be output to an xml file that looks like this. <timeCost> <person name="fred"> <time hour="5"> <cost price="12.5" /> <cost price="13.5" /> <cost price="14" /> <cost price="15" /> <cost price="16" /> </time> <time hour="6"> <cost price="10" /> <cost price="11" /> <cost price="14" /> <cost price="15" /> <cost price="19.7" /> </time> </person> <person name="dave"> <time hour="6"> <cost price="8" /> <cost price="12" /> <cost price="18" /> <cost price="20.2" /> <cost price="25" /> </time> </person> </timeCost> I have a linq query to get the data from SQL something like this. // initialize data context var people = from p in dc.people orderby p.name, p.hour select p; However, I'm having trouble writing the xml out using linq (csharp). Specifically, the problem is I don't know how to deal with having multiple time nodes under each name node (nested loops/collections). How can this be done? This is a sql 08 ent db if it matters to anyone.

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Adding a generic image field onto a ModelForm in django

- by Prairiedogg

I have two models, Room and Image. Image is a generic model that can tack onto any other model. I want to give users a form to upload an image when they post information about a room. I've written code that works, but I'm afraid I've done it the hard way, and specifically in a way that violates DRY. Was hoping someone who's a little more familiar with django forms could point out where I've gone wrong. Update: I've tried to clarify why I chose this design in comments to the current answers. To summarize: I didn't simply put an ImageField on the Room model because I wanted more than one image associated with the Room model. I chose a generic Image model because I wanted to add images to several different models. The alternatives I considered were were multiple foreign keys on a single Image class, which seemed messy, or multiple Image classes, which I thought would clutter my schema. I didn't make this clear in my first post, so sorry about that. Seeing as none of the answers so far has addressed how to make this a little more DRY I did come up with my own solution which was to add the upload path as a class attribute on the image model and reference that every time it's needed. # Models class Image(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') image = models.ImageField(_('Image'), height_field='', width_field='', upload_to='uploads/images', max_length=200) class Room(models.Model): name = models.CharField(max_length=50) image_set = generic.GenericRelation('Image') # The form class AddRoomForm(forms.ModelForm): image_1 = forms.ImageField() class Meta: model = Room # The view def handle_uploaded_file(f): # DRY violation, I've already specified the upload path in the image model upload_suffix = join('uploads/images', f.name) upload_path = join(settings.MEDIA_ROOT, upload_suffix) destination = open(upload_path, 'wb+') for chunk in f.chunks(): destination.write(chunk) destination.close() return upload_suffix def add_room(request, apartment_id, form_class=AddRoomForm, template='apartments/add_room.html'): apartment = Apartment.objects.get(id=apartment_id) if request.method == 'POST': form = form_class(request.POST, request.FILES) if form.is_valid(): room = form.save() image_1 = form.cleaned_data['image_1'] # Instead of writing a special function to handle the image, # shouldn't I just be able to pass it straight into Image.objects.create # ...but it doesn't seem to work for some reason, wrong syntax perhaps? upload_path = handle_uploaded_file(image_1) image = Image.objects.create(content_object=room, image=upload_path) return HttpResponseRedirect(room.get_absolute_url()) else: form = form_class() context = {'form': form, } return direct_to_template(request, template, extra_context=context)

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How do I read Unicode characters from an MS Access 2007 database through Java?

- by Peter

In Java, I have written a program that reads a UTF8 text file. The text file contains a SQL query of the SELECT kind. The program then executes the query on the Microsoft Access 2007 database and writes all fields of the first row to a UTF8 text file. The problem I have is when a row is returned that contains unicode characters, such as "?". These characters show up as "?" in the text file. I know that the text files are read and written correctly, because a dummy UTF8 character ("?") is read from the text file containing the SQL query and written to the text file containing the resulting row. The UTF8 character looks correct when the written text file is opened in Notepad, so the reading and writing of the text files are not part of the problem. This is how I connect to the database and how I execute the SQL query: ---- START CODE Connection c = DriverManager.getConnection("jdbc:odbc:Driver={Microsoft Access Driver (*.mdb, *.accdb)};DBQ=C:/database.accdb;Pwd=temp"); ResultSet r = c.createStatement().executeQuery(sql); ---- END CODE I have tried making a charSet property to the Connection but it makes no difference: ---- START CODE Properties p = new Properties(); p.put("charSet", "utf-8"); p.put("lc_ctype", "utf-8"); p.put("encoding", "utf-8"); Connection c = DriverManager.getConnection("...", p); ---- END CODE Tried with "utf8"/"UTF8"/"UTF-8", no difference. If I enter "UTF-16" I get the following exception: "java.lang.IllegalArgumentException: Illegal replacement". Been searching around for hours with no results and now turn my hope to you. Please help! I also accept workaround suggestions. =) What I want to be able to do is to make a Unicode query (for example one that searches for posts that contain the "?" character) and to have results with Unicode characters receieved and saved correctly. Thank you!

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What's the best way to do base36 arithmetic in perl?

- by DVK

What's the best way to do base36 arithmetic in Perl? To be more specific, I need to be able to do the following: Operate on positive N-digit numbers in base 36 (e.g. digits are 0-9 A-Z) N is finite, say 9 Provide basic arithmetic, at the very least the following 3: Addition (A+B) Subtraction (A-B) Whole division, e.g. floor(A/B). Strictly speaking, I don't really need a base10 conversion ability - the numbers will 100% of time be in base36. So I'm quite OK if the solution does NOT implement conversion from base36 back to base10 and vice versa. I don't much care whether the solution is brute-force "convert to base 10 and back" or converting to binary, or some more elegant approach "natively" performing baseN operations (as stated above, to/from base10 conversion is not a requirement). My only 3 considerations are: It fits the minimum specifications above It's "standard". Currently we're using and old homegrown module based on base10 conversion done by hand that is buggy and sucks. I'd much rather replace that with some commonly used CPAN solution instead of re-writing my own bicycle from scratch, but I'm perfectly capable of building it if no better standard possibility exists. It must be fast-ish (though not lightning fast). Something that takes 1 second to sum up 2 9-digit base36 numbers is worse than anything I can roll on my own :) P.S. Just to provide some context in case people decide to solve my XY problem for me in addition to answering the technical question above :) We have a fairly large tree (stored in DB as a bunch of edges), and we need to superimpose order on a subset of that tree. The tree dimentions are big both depth- and breadth- wise. The tree is VERY actively updated (inserts and deletes and branch moves). This is currently done by having a second table with 3 columns: parent_vertex, child_vertex, local_order, where local_order is an 9-character string built of A-Z0-9 (e.g. base 36 number). Additional considerations: It is required that the local order is unique per child (and obviously unique per parent), Any complete re-ordering of a parent is somewhat expensive, and thus the implementation is to try and assign - for a parent with X children - the orders which are somewhat evenly distributed between 0 and 36**10-1, so that almost no tree inserts result in a full re-ordering.

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jQuery: Trying to write my first plugin, how can I pass a selector to my func?

- by Jannis

Hi, I am trying to start writing some simple jQuery plugins and for my first try if figured I would write something that does nothing else but apply .first & .last classes to passed elements. so for instance i want to ultimately be able to: $('li').firstnlast(); So that in this html structure: <ul> <li></li> <li></li> <li></li> <li></li> </ul> <ul> <li></li> <li></li> </ul> it would create the following: <ul> <li class="first"></li> <li></li> <li></li> <li class="last"></li> </ul> <ul> <li class="first"></li> <li class="last"></li> </ul> What i have written so far in my plugin is this: (function($) { $.fn.extend({ firstnlast: function() { $(this) .first() .addClass('first') .end() .last() .addClass('last'); } }); })(jQuery); However the above only returns this: <ul> <li class="first"></li> <li></li> <li></li> <li></li> </ul> <ul> <li></li> <li class="last"></li> </ul> It seems that passing only the li into the function it will look at all li elements on the entire page and then apply the classes to it. What I need to figure out is how i can basically make the function 'context aware' so that passing the above li into the function would apply the classes to those lis inside of the parent ul, not to the first and last li on the entire page. Any hints, ideas and help would be much appreciated. Thanks for reading, Jannis

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Using JUnit as an acceptance test framework

- by Chris Knight

OK, so I work for a company who has openly adopted agile practices for development in recent years. Our unit tests and code quality are improving. One area we still are working on is to find what works best for us in the automated acceptance test arena. We want to take our well formed user stories and use these to drive the code in a test driven manner. This will also give us acceptance level tests for each user story which we can then automate. To date, we've tried Fit, Fitnesse and Selenium. Each have their advantages, but we've also had real issues with them as well. With Fit and Fitnesse, we can't help but feel they overcomplicate things and we've had many technical issues using them. The business haven't fully bought in these tools and aren't particularly keen on maintaining the scripts all the time (and aren't big fans of the table style). Selenium is really good, but slow and relies on real time data and resources. One approach we are now considering is the use of the JUnit framework to provide similiar functionality. Rather than testing just a small unit of work using JUnit, why not use it to write a test (using the JUnit framework) to cover an acceptance level swath of the application? I.e. take a new story ("As a user I would like to see basic details of my policy...") and write a test in JUnit which starts executing application code at the point of entry for the policy details link but covers all code and logic down to the stubbed data access layer and back to the point of forwarding to the next page in the application, asserting on what data the user should see on that page. This seems to me to have the following advantages: Simplicity (no additional frameworks required) Zero effort to integrate with our Continuous Integration build server (since it already handles our JUnit tests) Full skillset already present in the team (its just a JUnit test after all) And the downsides being: Less customer involvement (though they are heavily involved in writing the user stories in the first place from which the acceptance tests will be written) Perhaps more difficult to understand (or make understood) the user story and acceptance criteria in a JUnit class verses a freetext specification ala Fit or Fitnesse So, my question is really, have you ever tried this method? Ever considered it? What are your thoughts? What do you like and dislike about this approach? Finally, please only mention alternative frameworks if you can say why you like or dislike them more than this approach.

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SimpleXML SOAP response Namespace issues

- by Stu

Hi. After spending SEVERAL frustrated hours on this I am asking for your help. I am trying to get the content of particular nodes from a SOAP response. The response is $XmlStr = <?xml version="1.0" encoding="UTF-8"?><env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope"<xmlns:ns1="http://soap.xxxxxx.co.uk/"><env:Body><ns1:PlaceOrderResponse><xxxxxOrderNumber></xxxxxOrderNumber><ErrorArray><Error><ErrorCode>24</ErrorCode><ErrorText>The+client+order+number+3002254+is+already+in+use</ErrorText></Error><Error><ErrorCode>1</ErrorCode><ErrorText>Aborting</ErrorText></Error></ErrorArray></ns1:PlaceOrderResponse></env:Body></env:Envelope> I am trying to get at the nodes and children of <ErrorArray. Because of the XML containing namespaces $XmlArray = new SimpleXMLElement($XmlStr); foreach ($XmlArray->env:Envelope->env:Body->ns1:PlaceOrderResponse->ErrorArray->Error as $Error) { echo $Error->ErrorCode."<br />";<br /> } doesn't work. I have read a number of articles such as http://www.sitepoint.com/blogs/2005/10/20/simplexml-and-namespaces/ htp://blog.stuartherbert.com/php/2007/01/07/using-simplexml-to-parse-rss-feeds/ and about 20 questions on this site which unfortunately are not helping. (the second link has htp:// as a newbie here I cannot post more than one link) Even writing, $XmlArray = new SimpleXMLElement($XmlStr); echo "<br /><br /><pre>\n"; print_r($XmlArray); echo "<pre><br /><br />\n"; gives SimpleXMLElement Object ( ) which makes me wonder if the soap response ($XmlStr) is actually a valid input for SimpleXMLElement. It seems that the line $XmlArray = new SimpleXMLElement($XmlStr); is not doing what I expect it to. Any help on how to get the nodes from the XML above would be very welcome. Obviously getting it to work (having a working example) is what I need in the short term, but if someone could help me understand what I am doing wrong would be better in the long term. Cheers. Stu

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iPhone dev: load a file from resource folder

- by thomax

I'm writing an iPhone app with a UIWebView which should display various html files I have in the app resource folder. In xcode my project overview, these html files are displayed like this: dirA |---> index.html |---> a1.html |---> a2.html |---> my.css |---> dirB |---> b1.html |---> b2.html |---> dirC |---> c1.html |---> c2.html These resources where added to the project as such: - Checked "Copy items into destination groups folder (if needed)". - Reference type: Default. - Text encoding: Unicode (utf-8). - Recursively create groups for any added folders. The links in my html are relative, meaning they look like this: <a href="a1.html">a2</a> <a href="a2.html">a2</a> <a href="dirB/b2.html">b2</a> <a href="dirC/c1.html">b2</a> In order to display the index.html when the app starts up, I use the following code: NSString *path = [[NSBundle mainBundle] pathForResource:@"index" ofType:@"html"]; NSURL *url = [NSURL fileURLWithPath:path]; NSURLRequest *request = [NSURLRequest requestWithURL:url]; [webView loadRequest:request]; This works fine. Following links from the index file also works fine, as long as the html files requested are directly under dirA. If the link followed points to a file in a sub-directory, then didFailLoadWithError will catch the situation and report that the requested file does not exist. Note that [webView loadHtmlString:myHtml]; cannot be part of the solution, as I need back and forward buttons to work in my web view. So the question is: How can I follow a relative link to an html file in a sub directory within my resources? I've been all over stackoverflow and the rest of the tubes for the past few days trying to figure this one out, but nowhere have I come across the solution to this exact problem. Any insight at all would be very, very much appreciated!

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Wordpress: how to call a plugin function with an ajax call?

- by Bee

I'm writing a Wordpress MU plugin, it includes a link with each post and I want to use ajax to call one of the plugin functions when the user clicks on this link, and then dynamically update the link-text with output from that function. I'm stuck with the ajax query. I've got this complicated, clearly hack-ish, way to do it, but it is not quite working. What is the 'correct' or 'wordpress' way to include ajax functionality in a plugin? (My current hack code is below. When I click the generate link I don't get the same output I get in the wp page as when I go directly to sample-ajax.php in my browser.) I've got my code[1] set up as follows: mu-plugins/sample.php: <?php /* Plugin Name: Sample Plugin */ if (!class_exists("SamplePlugin")) { class SamplePlugin { function SamplePlugin() {} function addHeaderCode() { echo '<link type="text/css" rel="stylesheet" href="'.get_bloginfo('wpurl'). '/wp-content/mu-plugins/sample/sample.css" />\n'; wp_enqueue_script('sample-ajax', get_bloginfo('wpurl') . '/wp-content/mu-plugins/sample/sample-ajax.js.php', array('jquery'), '1.0'); } // adds the link to post content. function addLink($content = '') { $content .= "<span class='foobar clicked'><a href='#'>click</a></span>"; return $content; } function doAjax() { // echo "<a href='#'>AJAX!</a>"; } } } if (class_exists("SamplePlugin")) { $sample_plugin = new SamplePlugin(); } if (isset($sample_plugin)) { add_action('wp_head',array(&$sample_plugin,'addHeaderCode'),1); add_filter('the_content', array(&$sample_plugin, 'addLink')); } mu-plugins/sample/sample-ajax.js.php: <?php if (!function_exists('add_action')) { require_once("../../../wp-config.php"); } ?> jQuery(document).ready(function(){ jQuery(".foobar").bind("click", function() { var aref = this; jQuery(this).toggleClass('clicked'); jQuery.ajax({ url: "http://mysite/wp-content/mu-plugins/sample/sample-ajax.php", success: function(value) { jQuery(aref).html(value); } }); }); }); mu-plugins/sample/sample-ajax.php: <?php if (!function_exists('add_action')) { require_once("../../../wp-config.php"); } if (isset($sample_plugin)) { $sample_plugin->doAjax(); } else { echo "unset"; } ?> [1] Note: The following tutorial got me this far, but I'm stumped at this point. http://www.devlounge.net/articles/using-ajax-with-your-wordpress-plugin

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Exposing C# COM server events to Delphi client applications

- by hectorsosajr

My question is very similar to these two: http://stackoverflow.com/questions/1140984/c-component-events http://stackoverflow.com/questions/1638372/c-writing-a-com-server-events-not-firing-on-client However, what worked for them is not working for me. The type library file, does not have any hints of events definitions, so Delphi doesn't see it. The class works fine for other C# applications, as you would expect. COM Server tools: Visual Studio 2010 .NET 4.0 Delphi applications: Delphi 2010 Delphi 7 Here's a simplified version of the code: /// <summary> /// Call has arrived delegate. /// </summary> [ComVisible(false)] public delegate void CallArrived(object sender, string callData); /// <summary> /// Interface to expose SimpleAgent events to COM /// </summary> [ComVisible(true)] [GuidAttribute("1FFBFF09-3AF0-4F06-998D-7F4B6CB978DD")] [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IAgentEvents { ///<summary> /// Handles incoming calls from the predictive manager. ///</summary> ///<param name="sender">The class that initiated this event</param> ///<param name="callData">The data associated with the incoming call.</param> [DispId(1)] void OnCallArrived(object sender, string callData); } /// <summary> /// Represents the agent side of the system. This is usually related to UI interactions. /// </summary> [ComVisible(true)] [GuidAttribute("EF00685F-1C14-4D05-9EFA-538B3137D86C")] [ClassInterface(ClassInterfaceType.None)] [ComSourceInterfaces(typeof(IAgentEvents))] public class SimpleAgent { /// <summary> /// Occurs when a call arrives. /// </summary> public event CallArrived OnCallArrived; public SimpleAgent() {} public string AgentName { get; set; } public string CurrentPhoneNumber { get; set; } public void FireOffCall() { if (OnCallArrived != null) { OnCallArrived(this, "555-123-4567"); } } } The type library file has the definitions for the properties and methods, but no events are visible. I even opened the type library in Delphi's viewer to make sure. The Delphi app can see and use any property, methods, and functions just fine. It just doesn't see the events. I would appreciate any pointers or articles to read. Thanks!

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Boggling Direct3D9 dynamic vertex buffer Lock crash/post-lock failure on Intel GMA X3100.

- by nj

Hi, For starters I'm a fairly seasoned graphics programmer but as wel all know, everyone makes mistakes. Unfortunately the codebase is a bit too large to start throwing sensible snippets here and re-creating the whole situation in an isolated CPP/codebase is too tall an order -- for which I am sorry, do not have the time. I'll do my best to explain. B.t.w, I will of course supply specific pieces of code if someone wonders how I'm handling this-or-that! As with all resources in the D3DPOOL_DEFAULT pool, when the device context is taken away from you you'll sooner or later will have to reset your resources. I've built a mechanism to handle this for all relevant resources that's been working for years; but that fact nothingwithstanding I've of course checked, asserted and doubted any assumption since this bug came to light. What happens is as follows: I have a rather large dynamic vertex buffer, exact size 18874368 bytes. This buffer is locked (and discarded fully using the D3DLOCK_DISCARD flag) each frame prior to generating dynamic geometry (isosurface-related, f.y.i) to it. This works fine, until, of course, I start to reset. It might take 1 time, it might take 2 or it might take 5 resets to set off a bug that causes an access violation either on the pointer returned by the Lock() operation on the renewed resource or a plain crash -- regarding a somewhat similar address, but without the offset that it has tacked on to it in the first case because in that case we're somewhere halfway writing -- iside the D3D9 dll Lock() call. I've tested this on other hardware, upgraded my GMA X3100 drivers (using a MacBook with BootCamp) to the latest ones, but I can't reproduce it on any other machine and I'm at a loss about what's wrong here. I have tried to reproduce a similar situation with a similar buffer (I've got a large scratch pad of the same type I filled with quads) and beyond a certain amount of bytes it started to behave likewise. I'm not asking for a solution here but I'm very interested if there are other developers here who have battled with the same foe or maybe some who can point me in some insightful direction, maybe ask some questions that might shed a light on what I may or may not be overlooking. Another interesting artifact is that the vertex buffer starts to bug if I supply both D3DLOCK_DISCARD and D3DLOCK_NOOVERWRITE together which, even though not very logical (you're not going to overwrite if you've just discarded all), gives graphics glitches. Thanks and any corrections are more than welcome. Niels p.s - A friend of mine raised the valid point that it is a huge buffer for onboard video RAM and it's being at least double or triple buffered internally due to it's dynamic nature. On the other hand, the debug output (D3D9 debug DLL + max. warning output) remains silent. p.s 2 - Had it tested on more machines and still works -- it's probably a matter of circumstance: the huge dynamic, internally double/trippled buffered buffer, not a lot of memory and drivers that don't complain when they should.. Unless someone has a better suggestion; I'd still love to hear it :)

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Stack and queue operations on the same array.

- by Passonate Learner

Hi. I've been thinking about a program logic, but I cannot draw a conclusion to my problem. Here, I've implemented stack and queue operations to a fixed array. int A[1000]; int size=1000; int top; int front; int rear; bool StackIsEmpty() { return (top==0); } bool StackPush( int x ) { if ( top >= size ) return false; A[top++] = x; return true; } int StackTop( ) { return A[top-1]; } bool StackPop() { if ( top <= 0 ) return false; A[--top] = 0; return true; } bool QueueIsEmpty() { return (front==rear); } bool QueuePush( int x ) { if ( rear >= size ) return false; A[rear++] = x; return true; } int QueueFront( ) { return A[front]; } bool QueuePop() { if ( front >= rear ) return false; A[front++] = 0; return true; } It is presumed(or obvious) that the bottom of the stack and the front of the queue is pointing at the same location, and vice versa(top of the stack points the same location as rear of the queue). For example, integer 1 and 2 is inside an array in order of writing. And if I call StackPop(), the integer 2 will be popped out, and if I call QueuePop(), the integer 1 will be popped out. My problem is that I don't know what happens if I do both stack and queue operations on the same array. The example above is easy to work out, because there are only two values involved. But what if there are more than 2 values involved? For example, if I call StackPush(1); QueuePush(2); QueuePush(4); StackPop(); StackPush(5); QueuePop(); what values will be returned in the order of bottom(front) from the final array? I know that if I code a program, I would receive a quick answer. But the reason I'm asking this is because I want to hear a logical explanations from a human being, not a computer.

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Unique element ID, even if element doesn't have one

- by Robert J. Walker

I'm writing a GreaseMonkey script where I'm iterating through a bunch of elements. For each element, I need a string ID that I can use to reference that element later. The element itself doesn't have an id attribute, and I can't modify the original document to give it one (although I can make DOM changes in my script). I can't store the references in my script because when I need them, the GreaseMonkey script itself will have gone out of scope. Is there some way to get at an "internal" ID that the browser uses, for example? A Firefox-only solution is fine; a cross-browser solution that could be applied in other scenarios would be awesome. Edit: If the GreaseMonkey script is out of scope, how are you referencing the elements later? They GreaseMonkey script is adding events to DOM objects. I can't store the references in an array or some other similar mechanism because when the event fires, the array will be gone because the GreaseMonkey script will have gone out of scope. So the event needs some way to know about the element reference that the script had when the event was attached. And the element in question is not the one to which it is attached. Can't you just use a custom property on the element? Yes, but the problem is on the lookup. I'd have to resort to iterating through all the elements looking for the one that has that custom property set to the desired id. That would work, sure, but in large documents it could be very time consuming. I'm looking for something where the browser can do the lookup grunt work. Wait, can you or can you not modify the document? I can't modify the source document, but I can make DOM changes in the script. I'll clarify in the question. Can you not use closures? Closuses did turn out to work, although I initially thought they wouldn't. See my later post. It sounds like the answer to the question: "Is there some internal browser ID I could use?" is "No."

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Printf in assembler doesn't print

- by Gaim

Hi there, I have got a homework to hack program using buffer overflow ( with disassambling, program was written in C++, I haven't got the source code ). I have already managed it but I have a problem. I have to print some message on the screen, so I found out address of printf function, pushed address of "HACKED" and address of "%s" on the stack ( in this order ) and called that function. Called code passed well but nothing had been printed. I have tried to simulate the environment like in other place in the program but there has to be something wrong. Do you have any idea what I am doing wrong that I have no output, please? Thanks a lot EDIT: This program is running on Windows XP SP3 32b, written in C++, Intel asm there is the "hack" code CPU Disasm Address Hex dump Command Comments 0012F9A3 90 NOP ;hack begins 0012F9A4 90 NOP 0012F9A5 90 NOP 0012F9A6 89E5 MOV EBP,ESP 0012F9A8 83EC 7F SUB ESP,7F ;creating a place for working data 0012F9AB 83EC 7F SUB ESP,7F 0012F9AE 31C0 XOR EAX,EAX 0012F9B0 50 PUSH EAX 0012F9B1 50 PUSH EAX 0012F9B2 50 PUSH EAX 0012F9B3 89E8 MOV EAX,EBP 0012F9B5 83E8 09 SUB EAX,9 0012F9B8 BA 1406EDFF MOV EDX,FFED0614 ;address to jump, it is negative because there mustn't be 00 bytes 0012F9BD F7DA NOT EDX 0012F9BF FFE2 JMP EDX ;I have to jump because there are some values overwritten by the program 0012F9C1 90 NOP 0012F9C2 0090 00000000 ADD BYTE PTR DS:[EAX],DL 0012F9C8 90 NOP 0012F9C9 90 NOP 0012F9CA 90 NOP 0012F9CB 90 NOP 0012F9CC 6C INS BYTE PTR ES:[EDI],DX ; I/O command 0012F9CD 65:6E OUTS DX,BYTE PTR GS:[ESI] ; I/O command 0012F9CF 67:74 68 JE SHORT 0012FA3A ; Superfluous address size prefix 0012F9D2 2069 73 AND BYTE PTR DS:[ECX+73],CH 0012F9D5 203439 AND BYTE PTR DS:[EDI+ECX],DH 0012F9D8 34 2C XOR AL,2C 0012F9DA 2066 69 AND BYTE PTR DS:[ESI+69],AH 0012F9DD 72 73 JB SHORT 0012FA52 0012F9DF 74 20 JE SHORT 0012FA01 0012F9E1 3120 XOR DWORD PTR DS:[EAX],ESP 0012F9E3 6C INS BYTE PTR ES:[EDI],DX ; I/O command 0012F9E4 696E 65 7300909 IMUL EBP,DWORD PTR DS:[ESI+65],-6F6FFF8D 0012F9EB 90 NOP 0012F9EC 90 NOP 0012F9ED 90 NOP 0012F9EE 31DB XOR EBX,EBX ; hack continues 0012F9F0 8818 MOV BYTE PTR DS:[EAX],BL ; writing 00 behind word "HACKED" 0012F9F2 83E8 06 SUB EAX,6 0012F9F5 50 PUSH EAX ; address of "HACKED" 0012F9F6 B8 3B8CBEFF MOV EAX,FFBE8C3B 0012F9FB F7D0 NOT EAX 0012F9FD 50 PUSH EAX ; address of "%s" 0012F9FE B8 FFE4BFFF MOV EAX,FFBFE4FF 0012FA03 F7D0 NOT EAX 0012FA05 FFD0 CALL EAX ;address of printf This code is really ugly because I am new in assembler and there mustn't be null bytes because of buffer-overflow bug

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