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• Returning large collections from WCF Serivce

  - by Nate Bross

  I'm trying to determine the best approach for building a WCF Service, and the area I'm struggling with most is returning lists of objects. The built-in maxMessageSize of 64k seems pretty high, and I really don't want to bump it up (quick googling finds 100s of places bumping the maxMessageSize up to multi-gigabyte range which seems foolish). But, when I'm returning a collection of objects (~150 items) I am exceeding the default 64k. I'm almost to the point of returning my own class which inherits IEnumerable and has properties for hasNext, hasPrevious and PageSize so that I can implement paging on the client side -- this seems like alot of code. The other option is to jackup the maxMessageSize and hope for the best, but that feels wrong. All other aspects of my service are working great, its just returning large collectiosn where I'm having issues. For background, there are two types of consumers of this service, UI applications which will be primarly web and/or wpf applications, and data processing applications, .NET console apps, and maybe some other non-UI apps. For the UI applications, I would like to keep them responsive and keep the messageSize low, on the console apps it doesn't matter as much as they are just pulling data down to do processing and push it back up to the service.

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• Can I use POSIX signals in my Perl program to create event-driven programming?

  - by Shiftbit

  Is there any POSIX signals that I could utilize in my Perl program to create event-driven programming? Currently, I have multi-process program that is able to cross communicate but my parent thread is only able to listen to listen at one child at a time. foreach (@proc) { sysread(${$_}{'read'}, my $line, 100); #problem here chomp($line); print "Parent hears: $line\n"; } The problem is that the parent sits in a continual wait state until it receives it a signal from the first child before it can continue on. I am relying on 'pipe' for my intercommunication. My current solution is very similar to: http://stackoverflow.com/questions/2558098/how-can-i-use-pipe-to-facilitate-interprocess-communication-in-perl If possible I would like to rely on a $SIG{...} event or any non-CPAN solution. Update: As Jonathan Leffler mentioned, kill can be used to send a signal: kill USR1 = $$; # send myself a SIGUSR1 My solution will be to send a USR1 signal to my child process. This event tells the parent to listen to the particular child. child: kill USR1 => $parentPID if($customEvent); syswrite($parentPipe, $msg, $buffer); #select $parentPipe; print $parentPipe $msg; parent: $SIG{USR1} = { #get child pid? sysread($array[$pid]{'childPipe'}, $msg, $buffer); }; But how do I get my the source/child pid that signaled the parent? Have the child Identify itself in its message. What happens if two children signal USR1 at the same time?

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• Jquery set tr with empty td lower than with text in td

  - by PavelBY

  I have html, and jquery for sorting my table (also there is non-standart sorting (with multi-tbody)). My code could be found here: http://jsfiddle.net/GuRxj/ As you can see there, td with prices (on russian ????) are sorted ascending (but tech-as not!? why? (it a question too))... But as you see, i need to send this tr's with prices to top of this tbody (now there are in the bottom), while empty-price-tr send to bottom... How to do this? part of js: $('.prcol').click(function(e) { var $sort = this; var $table = $('#articles-table'); var $rows = $('tbody.analogs_art > tr',$table); $rows.sort(function(a, b){ var keyA = $('td:eq(3)',a).text(); var keyB = $('td:eq(3)',b).text(); if (keyA.length > 0 && keyB.length > 0) { if($($sort).hasClass('asc')){ console.log("bbb"); return (keyA > keyB) ? 1 : 0; } else { console.log(keyA+"-"+keyB); return (keyA > keyB) ? 1 : 0; } } }); $.each($rows, function(index, row){ //console.log(row); $table.append(row); //$("table.123").append(row); }); e.preventDefault(); });

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• Database for Python Twisted

  - by Will

  There's an API for Twisted apps to talk to a database in a scalable way: twisted.enterprise.dbapi The confusing thing is, which database to pick? The database will have a Twisted app that is mostly making inserts and updates and relatively few selects, and then other strictly-read-only clients that are accessing the database directly making selects. (The read-only users are not necessarily selecting the data that the Twisted app is inserting; its not as though the database is being used as a message-queue) My understanding - which I'd like corrected/adviced - is that: Postgres is a great DB, but all the Python bindings - and there is a confusing maze of them - are abandonware There is psycopg2, but that makes a lot of noise about doing its own connection-pooling and things; does this co-exist gracefully/usefully/transparently with the Twisted async database connection pooling and such? SQLLite is a great database for little things but if used in a multi-user way it does whole-database locking, so performance would suck in the usage pattern I envisage MySQL - after the Oracle takeover, who'd want to adopt it now or adopt a fork? Is there anything else out there?

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• Testing subpackage modules in Python 3

  - by Mitchell Model

  I have been experimenting with various uses of hierarchies like this and the differences between absolute and relative imports, and can't figure out how to do routine things with the package, subpackages, and modules without simply putting everything on sys.path. I have a two-level package hierarchy: MyApp __init__.py Application __init__.py Module1 Module2 ... Domain __init__.py Module1 Module2 ... UI __init__.py Module1 Module2 ... I want to be able to do the following: Run test code in a Module's "if main" when the module imports from other modules in the same directory. Have one or more test code modules in each subpackage that runs unit tests on the modules in the subpackage. Have a set of unit tests that reside in someplace reasonable, but outside the subpackages, either in a sibling package, at the top-level package, or outside the top-level package (though all these might end up doing is running the tests in each subpackage) "Enter" the structure from any of the three subpackage levels, e.g. run code that just uses Domain modules, run code that just uses Application modules, but Application uses code from both Application and Domain modules, and run code from GUI uses code from both GUI and Application; for instance, Application test code would import Application modules but not Domain modules. After developing the bulk of the code without subpackages, continue developing and testing after organizing the modules into this hierarchy. I know how to use relative imports so that external code that puts MyApp on its sys.path can import MyApp, import any subpackages it wants, and import things from their modules, while the modules in each subpackage can import other modules from the same subpackage or from sibling packages. However, the development needs listed above seem incompatible with subpackage structuring -- in other words, I can't have it both ways: a well-structured multi-level package hierarchy used from the outside and also used from within, in particular for testing but also because modules from one design level (in particular the UI) should not import modules from a design level below the next one down. Sorry for the long essay, but I think it fairly represents the struggles a lot of people have been having adopting to the new relative import mechanisms.

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• ANSI or OEM Codepage when using MME and DirectMusic?

  - by Carl Seleborg

  Hello, I noticed that when reading MIDI port names from MME, the names are multi-byte strings encoded using the ANSI Codepage, which my app uses by default. When receiving those names from the DirectMusic driver, the names are wide-character strings encoded with the OEM Codepage. See this article by Raymond Chen for a quick refresher on Codepages. On my German system, this means that when using the current codepage, which turns out to be the ANSI one, I get "Audiogerät" from MME, and "Audiogeröt" from DirectMusic, the latter being wrong. This gets fixed when I treat that last name as OEM-encoded instead. So how do I know with which codepage to decode those names? Why does the name coming from DirectMusic get encoded differently? Does it come from the USB driver? The COM framework? DirectMusic? How can I know for sure which codepage to use when reading the names of my MIDI ports? For info: I use the MultiByteToWideChar() and WideCharToMultiByte() functions to perform the conversions, with CP_ACP and CP_OEMCP as argument for the codepage to use. I use midiInGetDeviceCaps() to get MIDI port information from the MME subsystem... ... and convert MIDIINCAPS.szPname using the CP_ACP (ANSI) codepage. I use IID_IDirectMusic8::EnumPort() to get port information from DirectMusic... ... and convert DMUS_PORTCAPS.wszDescription using the CP_OEMCP codepage.

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• DB2 Driver Connection Hanging in Glassfish Connection Pool

  - by Ant

  We have an intermittent issue around the DB2 used from a Glassfish connection pool. What happens is this: Under situations where the database (DB2 on ZOS) is under stress, our application (which is a multi-threaded application using connections to DB2 via a Glassfish connection pool) stops doing anything. The following are observed: 1) Looking at the server using JConsole, we can see a thread waiting indefinitely in the DB2 driver's getConnection() method. We can also see that it has gained a lock on a Vector within the driver. Several other threads are also calling the getConnection() method in the driver, and are hanging waiting for the lock on the Vector to be released. 2) Looking at the database itself, we can see that there are connections from the Glassfish server open and waiting to be used. It seems that there is some sort of mismatch between the connection pool on Glassfish and the connections actually open to DB2. Has anyone come across this issue before? Or something similar? If you need any more information that I haven't provided, then please let me know!

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• Opaque tenant identification with SQL Server & NHibernate

  - by Anton Gogolev

  Howdy! We're developing a nowadays-fashionable multi-tenanted SaaS app (shared database, shared schema), and there's one thing I don't like about it: public class Domain : BusinessObject { public virtual long TenantID { get; set; } public virtual string Name { get; set; } } The TenantID is driving me nuts, as it has to be accounted for almost everywhere, and it's a hassle from security standpoint: what happens if a malicious API user changes TenantID to some other value and will mix things up. What I want to do is to get rid of this TenantID in our domain objects altogether, and to have either NHibernate or SQL Server deal with it. From what I've already read on the Internets, this can be done with CONTEXT_INFO (here's a NHibernatebased implementation), NHibernate filters, SQL Views and with combination thereof. Now, my requirements are as follows: Remove any mentions of TenantID from domain objects ...but have SQL Server insert it where appropriate (I guess this is achieved with default constraints) ...and obviously provide support for filtering based on this criteria, so that customers will never see each other's data If possible, avoid SQL Server views. Have a solution which plays nicely with NHibernate, SQL Servers' MARS and general nature of SaaS apps being highly concurrent What are your thoughts on that?

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• Monotouch threads, GC, WCF

  - by cvista

  Hi This is a question about best practices i guess but it applies directly to my current MT project. I'm using WCF services to communicate with the server. To do this i do the following: services.MethodToCall(params); and the asynch: services.OnMethodToCallCompleted += delegate{ //do stuff and ting }; This can lead to issues if you're not careful in that variables defined within the scope of the asynch callback can sometimes be cleaned up by the gc and this can cause crashes. So - I am making it a practice to declare these outside of the scope of the callback unless I am 100% sure they are not needed. Now - when doing stuff and ting implies changing the ui - i wrap it all in an InvokeOnMainThread call. I guess wrapping everything in this would slow the main thread down and rubbish the point of having multi threads. Even though I'm being careful about all this i am still getting crashes and I have no idea why! I am certain it has something to do with threads, scope and all that. Now - the only thing I can think of outside of updating the UI that may need to happen inside of InvokeOnMainThread is that I have a singleton 'Database' class. This is based on the version 5 code from this thread http://www.yoda.arachsys.com/csharp/singleton.html So now if the service method returns data that needs to be added/updated to the Database class -I also wrap this inside an InvokeOnMainThread call. Still getting random crashes. So... My question is this: I am new to thick client dev - I'm coming from a web dev perspective where we don't need to worry about threads so much :) Aside from what I have mentioned -are there any other things I should be aware of? Is the above stuff correct? Or am i miss-understanding something? Cheers w://

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• UTF8 charset, diacritical elements, conversion problems - and Zend Framework form escaping

  - by imanc

  Hey, I am writing a webapp in ZF and am having serious issues with UTF8. It's using multi lingual content through Zend Form and it seems that ZF heavily escapes all of these characters and basically just won't show a field if there's diacritical elements 'é' and if I use the HTML entity equivalent e.g. é it gets escaped so that the user will see 'é'. Zend Form allows for having non escaped data, but trying to use this is confusing, and it seems it'd need to be used all over the place. So, I have been told that if the page and the text is in UTF8, no conversion to htmlentities is required. Is this true? And if the last question is true, then how do I convert the source text to UTF8? I am comfortable setting up apache so that it sends a default UTF8 charset heading, and also adding the charset meta tag to the html, but doing this I am still getting messed up encoding. I have also tried opening the translation csv file in TextWrangler on OSX as UTF8, but it has done nothing. Thanks! L

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• How to use multifieldquery and filters in Lucene.net

  - by Khotu Nam

  I want to perform a multi field search on a lucene.net index but filter the results based on one of the fields. Here's what I'm currently doing: To index the fields the definitions are: doc.Add(new Field("id", id.ToString(), Field.Store.YES, Field.Index.UN_TOKENIZED)); doc.Add(new Field("title", title, Field.Store.NO, Field.Index.TOKENIZED)); doc.Add(new Field("summary", summary, Field.Store.NO, Field.Index.TOKENIZED, Field.TermVector.YES)); doc.Add(new Field("description", description, Field.Store.NO, Field.Index.TOKENIZED, Field.TermVector.YES)); doc.Add(new Field("distribution", distribution, Field.Store.NO, Field.Index.UN_TOKENIZED)); When I perform the search I do the following: MultiFieldQueryParser parser = new MultiFieldQueryParser(new string[]{"title", "summary", "description"}, analyzer); parser.SetDefaultOperator(QueryParser.Operator.AND); Query query = parser.Parse(text); BooleanQuery bq = new BooleanQuery(); TermQuery tq = new TermQuery(new Term("distribution", distribution)); bq.Add(tq, BooleanClause.Occur.MUST); Filter filter = new QueryFilter(bq); Hits hits = searcher.Search(query, filter); However, the result is always 0 hits. What am I doing wrong?

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• Interface vs Abstract Class (general OO)

  - by Kave

  Hi, I have had recently two telephone interviews where I've been asked about the differences between an Interface and an Abstract class. I have explained every aspect of them I could think of, but it seems they are waiting for me to mention something specific, and I dont know what it is. From my experience I think the following is true, if i am missing a major point please let me know: Interface: Every single Method declared in an Interface will have to be implemented in the subclass. Only Events, Delegates, Properties (C#) and Methods can exist in a Interface. A class can implement multiple Interfaces. Abstract Class Only Abstract methods have to be implemented by the subclass. An Abstract class can have normal methods with implementations. Abstract class can also have class variables beside Events, Delegates, Properties and Methods. A class can only implement one abstract class only due non-existence of Multi-inheritance in C#. 1) After all that the interviewer came up with the question What if you had an Abstract class with only abstract methods, how would that be different from an interface? I didnt know the answer but I think its the inheritance as mentioned above right? 2) An another interviewer asked me what if you had a Public variable inside the interface, how would that be different than in Abstract Class? I insisted you can't have a public variable inside an interface. I didn't know what he wanted to hear but he wasn't satisfied either. Many Thanks for clarification, Kave See Also: When to use an interface instead of an abstract class and vice versa Interfaces vs. Abstract Classes How do you decide between using an Abstract Class and an Interface?

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• how to make Regular expression into non-greedy ?

  - by Rueta

  Hi everyone! I have made a Work with JQ. My Work is a string width a special character block begin and end of string. I want take the text in that special characters, i used regular expression for find in string, but how to make JQ find multi result when have two special character or more. My html here; <div id="container"> <div id="textcontainer"> Cu?c chi?n pháp lý gi?a [|co th?|nghi?m|] th? tru?ng [|test2|dây là test l?n 2|] ch?ng khoán [|M?|day la nuoc my|] và ngân hàng d?u tu quy?n l?c nh?t Ph? Wall m?i ch? b?t d?u. </div> </div> and my JQ $(document).ready(function() { var takedata = $("#textcontainer").text(); var test = 'abcd adddb'; var filterdata = takedata.match(/(\[.+\])/); alert(filterdata); //end write js }); my result is: [|co th?|nghi?m|] th? tru?ng [|test2|dây là test l?n 2|] ch?ng khoán [|M?|day la nuoc my|] . but this is'nt the result i want :(. How to get [text] for times 1 and [demo] for times 2 ?. pls help me !. thankyou :)

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• Database Functional Programming in Clojure

  - by Ralph

  "It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail." - Abraham Maslow I need to write a tool to dump a large hierarchical (SQL) database to XML. The hierarchy consists of a Person table with subsidiary Address, Phone, etc. tables. I have to dump thousands of rows, so I would like to do so incrementally and not keep the whole XML file in memory. I would like to isolate non-pure function code to a small portion of the application. I am thinking that this might be a good opportunity to explore FP and concurrency in Clojure. I can also show the benefits of immutable data and multi-core utilization to my skeptical co-workers. I'm not sure how the overall architecture of the application should be. I am thinking that I can use an impure function to retrieve the database rows and return a lazy sequence that can then be processed by a pure function that returns an XML fragment. For each Person row, I can create a Future and have several processed in parallel (the output order does not matter). As each Person is processed, the task will retrieve the appropriate rows from the Address, Phone, etc. tables and generate the nested XML. I can use a a generic function to process most of the tables, relying on database meta-data to get the column information, with special functions for the few tables that need custom processing. These functions could be listed in a map(table name -> function). Am I going about this in the right way? I can easily fall back to doing it in OO using Java, but that would be no fun. BTW, are there any good books on FP patterns or architecture? I have several good books on Clojure, Scala, and F#, but although each covers the language well, none look at the "big picture" of function programming design.

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• Where to post code for open source usage?

  - by Douglas

  I've been working for a few weeks now with the Google Maps API v3, and have done a good bit of development for the map I've been creating. Some of the things I've done have had to be done to add usability where there previously was not any, at least not that I could find online. Essentially, I made a list of what had to be done, searched all over the web for the ways to do what I needed, and found that some were not(at the time) possible(in the "grab an example off the web" sense). Thus, in my working on this map, I have created a number of very useful tools, which I would like to share with the development community. Is there anywhere I could use as a hub, apart from my portfolio ( http://dougglover.com ), to allow people to view and recycle my work? I know how hard it can be to need to do something, and be unable to find the solution elsewhere, and I don't think that if something has been done before, it should necessarily need to be written again and again. Hence open source code, right? Firstly, I was considering coming on here and asking a question, and then just answering it. Problem there is I assume that would just look like a big reputation grab. If not, please let me know and I'll go ahead and do that so people here can see it. Other suggestions appreciated. Some stuff I've made: A (new and improved) LatLng generator Works quicker, generates LatLng based on position of a draggable marker Allows searching for an address to place the marker on/near the desired location(much better than having to scroll to your location all the way from Siberia) Since it's a draggable marker, double-clicking zooms in, instead of creating a new LatLng marker like the one I was originally using The ability to create entirely custom "Smart Paths" Plot LatLng points on the map which connect to each other just like they do using the actual Google Maps Using Dijkstra's algorithm with Javascript, the routing is intelligent and always gives the shortest possible route, using the points provided Simple, easy to read multi-dimensional array system allows for easily adding new points to the grid Any suggestions, etc. appreciated.

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• SWT Drag and Drop support for Text widget

  - by bryantsai

  I've written an application recently using SWT. In one of its dialog box, I have a few widgets, one of which is Text, which is designed to support DND with other widgets. I've first added DND support for the 2 Tree widgets on the same dialog box (both drag source and drop target). Before I added DND support for that Text widget, I noticed that on Linux platform (gtk), SWT Text widget automatically get drag and drop support. That is, I can already drag from the other Tree widgets and drop on this Text (at any position to inserted there), as well as selecting and dragging any text from this Text to other Tree or Text widget. However, this is only working on Linux platform but not on Windows. The same program, if running on Windows, will not have any DND support for that Text widget (Tree widgets of course have DND support since I specifically write for them). So here's what I want to achieve on Windows as well: drop text at any position in Text widget. before dropping and while hovering, able to see the caret position clearly where the intended position to drop. caret position should move along with the mouse cursor. support multi-line in Text widget SOLUTION: DropTarget target = new DropTarget(sytledText, DND.DROP_MOVE | DND.DROP_COPY); target.setTransfer(new Transfer[] { TextTransfer.getInstance() }); target.addDropListener(new StyleTextDropTargetEffect(sytledText)); Use StyledText instead of Text widget Use StyledTextDropTargetEffect (or extend it) and add it as dr op listener

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• fullCalendar: Implementing a custom event fetcher using event as function

  - by Nick-ACNB

  If I specify a json feed, the events are re-fetched everytime and the fetching time shows the item appearing which causes a delay which is undesirable (at least after initial fetch was done). I am using the latest version from gitHub 1.4.6. The lazyFetching property seems to only work when you change views and you previously fetched for example a month and are drilling down to week/day which is unusable since I only use agendaDay. Here is what I am trying to achieve: $("#calendar").fullCalendar({ events: function(start, end, callback) { $.getJSON( "/GetEvents", { start: start.valueOf() }, function(data, textStatus) { $.each(data, function(i, event) { //Goal here is to only add items that aren't already rendered. if ($("#calendar") .fullCalendar('clientEvents', event.id)=="") $("#calendar").fullCalendar('renderEvent', event, true); }); } ); }); The goal is to use the sticky property in the renderEvent method so that on-screen they aren't re-rendered if they we're previously fetched. I omitted a part where I manually delete those that we're deleted and modify those that we're updated since I am in multi-user settings but you get the point. My issue is that they are fetched once and added. But once I change day and come back, they don't render even if I used sticky... has anyone gotten this error or did I code anything wrong? Also, is this a wrong way to go? I will consider any input. :) Thank you very much.

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• How to accommodate for the iPhone 4 screen resolution?

  - by dontWatchMyProfile

  This is a programming question! Read on before you vote to close! According to Apple, the iPhone 4 has a new and better screen resolution: 3.5-inch (diagonal) widescreen Multi-Touch display 960-by-640-pixel resolution at 326 ppi This little detail affects our apps in a heavy way. Most of the demo apps on the net have one thing in common: They position views in the believe that the screen has a fixed size of 320 x 480 pixels. So what most -if not all- developers do is: They designed everything in such a way, that a touchable area is -for example- 50 x 50 pixels big. Just enough to tap it. Things have been positioned relative to the upper left, to reach a specific position on screen - let's say the center, or somewhere at the bottom. Edit: It seems Apple has integrated an switch that allows to tell if an app is highRes or not. Nice. When we develop high-resolution apps, they probably won't work on older devices. And if they do, they would suffer a lot from 4-times the size of any image, having to scale them down in memory.

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• Python C API from C++ app - know when to lock

  - by Alex

  Hi Everyone, I am trying to write a C++ class that calls Python methods of a class that does some I/O operations (file, stdout) at once. The problem I have ran into is that my class is called from different threads: sometimes main thread, sometimes different others. Obviously I tried to apply the approach for Python calls in multi-threaded native applications. Basically everything starts from PyEval_AcquireLock and PyEval_ReleaseLock or just global locks. According to the documentation here when a thread is already locked a deadlock ensues. When my class is called from the main thread or other one that blocks Python execution I have a deadlock. Python Cfunc1() - C++ func that creates threads internally which lead to calls in "my class", It stuck on PyEval_AcquireLock, obviously the Python is already locked, i.e. waiting for C++ Cfunc1 call to complete... It completes fine if I omit those locks. Also it completes fine when Python interpreter is ready for the next user command, i.e. when thread is calling funcs in the background - not inside of a native call I am looking for a workaround. I need to distinguish whether or not the global lock is allowed, i.e. Python is not locked and ready to receive the next command... I tried PyGIL_Ensure, unfortunately I see hang. Any known API or solution for this ? (Python 2.4)

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• Seperate html pages for each screen in Jquery mobile

  - by vrs

  I am newbie to Jquery Mobile, so far what ever examples i searched contains only one html page for whole application, with multipe div tags where each page/screen is defined as div tag with data-role as page with some header and footers optionally. Based on user actions, we are hiding some div's(pages) and showing only expected page. Also, this multi-page template seems to be standard design, as written by some blogs. Are there any other designing ways? what I would like to have is multipe html pages, for ex one for login, one for home, one for contact etc. Other wise it is difficult to understand/code/debug issues, especially people from Java background like me.So, what I want is some kind of MVC design with JQueryMobile, like each view/screen as sepearate html associated with one js (Controller). Can we have multiple html pages in JqueryMobile app? If possible how to pass data/ maintain session between them? Any samples are most welcome. Thanks In Advance. Note: Also I don't want server side includes, may app contains 10 to 15 screens, each page will make a webservice call and fetch some data and map it to UI.

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• Reading same file from multiple threads in C#

  - by Gustavo Rubio

  Hi. I was googling for some advise about this and I found some links. The most obvious was this one but in the end what im wondering is how well my code is implemented. I have basically two classes. One is the Converter and the other is ConverterThread I create an instance of this Converter class that has a property ThreadNumber that tells me how many threads should be run at the same time (this is read from user) since this application will be used on multi-cpu systems (physically, like 8 cpu) so it is suppossed that this will speed up the import The Converter instance reads a file that can range from 100mb to 800mb and each line of this file is a tab-delimitted value record that is imported to another destination like a database. The ConverterThread class simply runs inside the thread (new Thread(ConverterThread.StartThread)) and has event notification so when its work is done it can notify the Converter class and then I can sum up the progress for all these threads and notify the user (in the GUI for example) about how many of these records have been imported and how many bytes have been read. It seems, however that I'm having some trouble because I get random errors about the file not being able to be read or that the sum of the progress (percentage) went above 100% which is not possible and I think that happens because threads are not being well managed and probably the information returned by the event is malformed (since it "travels" from one thread to another) Do you have any advise on better practices of implementation of threads so I can accomplish this? Thanks in advance.

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• Winsock WSAAsyncSelect sending without an infinite buffer

  - by Xexr

  Hi, This is more of a design question than a specific code question, I'm sure I am missing the obvious, I just need another set of eyes. I am writing a multi-client server based on WSAAsyncSelect, each connection is made into an object of a connection class I have written which contains associated settings and buffers etc. My question concerns FD_WRITE, I understand how it operates: One FD_WRITE is sent immediately after a connection is established. Thereafter, you should send until WSAEWOULDBLOCK is received at which point you store what is left to send in a buffer, and wait to be told that it is ok to send again. This is where I have a problem, how large do I make this holding buffer within each connections object? The amount of time until a new FD_WRITE is received is unknown, I could be attempting to send a lot of stuff during this period, all the time adding to my outgoing buffer. If I make the buffer dynamic, memory usage could spiral out of control if for whatever reason, I am unable to send() and reduce the buffer. So my question is how do you generally handle this situation? Note I am not talking about the network buffer itself which winsock uses, but one of my own creation used to "queue" up sends. Hope I explained that well enough, thanks all!

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• Thread-safe data structure design

  - by Inso Reiges

  Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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• Windows cmd encoding change causes Python crash.

  - by Alex

  First I chage Windows CMD encoding to utf-8 and run Python interpreter: chcp 65001 python Then I try to print a unicode sting inside it and when i do this Python crashes in a peculiar way (I just get a cmd prompt in the same window). >>> import sys >>> print u'ëèæîð'.encode(sys.stdin.encoding) Any ideas why it happens and how to make it work? UPD: sys.stdin.encoding returns 'cp65001' UPD2: It just came to me that the issue might be connected with the fact that utf-8 uses multi-byte character set (kcwu made a good point on that). I tried running the whole example with 'windows-1250' and got 'ëeaî?'. Windows-1250 uses single-character set so it worked for those characters it understands. However I still have no idea how to make 'utf-8' work here. UPD3: Oh, I found out it is a known Python bug. I guess what happens is that Python copies the cmd encoding as 'cp65001 to sys.stdin.encoding and tries to apply it to all the input. Since it fails to understand 'cp65001' it crushes on any input that contains non-ascii characters.

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• Access report not showing data

  - by Brian Smith

  I have two queries that I am using to generate a report from, the problem is when I run the report, three fields do not show any data at all for some reason. Query 1: SELECT ClientSummary.Field3 AS PM, ClientSummary.[Client Nickname 2] AS [Project #], ClientSummary.[Client Nickname 1] AS Customer, ClientSummary.[In Reference To] AS [Job Name], ClientSummary.Field10 AS Contract, (select sum([Billable Slip Value]) from Util_bydate as U1 where U1.[Client Nickname 2] = ClientSummary.[Client Nickname 2]) AS [This Week], (select sum([Billable Slip Value]) from Util as U2 where U2.[Client Nickname 2] = ClientSummary.[Client Nickname 2] ) AS [To Date], [To Date]/[Contract] AS [% Spent], 0 AS Backlog, ClientSummary.[Total Slip Fees & Costs] AS Billed, ClientSummary.Payments AS Paid, ClientSummary.[Total A/R] AS Receivable, [Forms]![ReportMenu]![StartDate] AS [Start Date], [Forms]![ReportMenu]![EndDate] AS [End Date] FROM ClientSummary; Query 2: SELECT JobManagement_Summary.pm, JobManagement_Summary.[project #], JobManagement_Summary.Customer, JobManagement_Summary.[Job Name], JobManagement_Summary.Contract, IIf(IsNull([This Week]),0,[This Week]) AS [N_This Week], IIf(IsNull([To Date]),0,[To Date]) AS [N_To Date], [% Spent], JobManagement_Summary.Backlog, JobManagement_Summary.Billed, JobManagement_Summary.Paid, JobManagement_Summary.Receivable, JobManagement_Summary.[Start Date], JobManagement_Summary.[End Date] FROM JobManagement_Summary; When I run the report from query 2 these 3 fields don't appear. N_This Week, N_To Date and % Spent. All have no data. It isn't the IIF functions, as it doesn't matter if I have those in there or remove them. Any thoughts? If I connect directly to the first recordset it works fine, but then SQL throws the error message: Multi-level GROUP BY cause not allowed in subquery. Is there any way to get around that message to link to it directly or does anyone have ANY clue why these fields are coming back blank? I am at wits end here!

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