interview questions - Page 460

OutOfMemoryException, large Private Data

- by Captain Comic

Hello, In previous series: http://stackoverflow.com/questions/2543648/outofmemoryexception-stack-size-is-huge-large-number-of-threads I have a .net windows service that consumes a lot of memory. The GC heap is not big. Also the stack size is not big. What is big is something called a private data. Also I can see in task manager that my application consumes a lot something that taskmanager calls a handle. My application consumes 2326 handles. I believe that these handles are some windows handles that occupy private data. I can see that this private data is occupied by blocks marked as Thread Environment Block. What is that? Screenshot of my application memory usage by VMMap Screenshot of my application memory usage by Task Manager UPDATE I run ProcessExplorer. I have two instances of my service running at the moment. I can see that they consume a lot of virtual memory for Gen2 GC. This look suspicios. Also total reserved for GC Heap size is the same for two processes.

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pointer being freed was not allocated. Complex malloc history help

- by Martin KS

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EXC_BREAKPOINT when starting iPhone app

- by pgb

A user of our app sent me the following crash log: Incident Identifier: 59D4D5E7-570A-4047-A679-3016B2A226C4 CrashReporter Key: d8284d671ee22ad17511360ce73409ebfa8b84bb Process: .... [63] Path: /var/mobile/Applications/.... Identifier: ... Version: ??? (???) Code Type: ARM (Native) Parent Process: launchd [1] Date/Time: 2010-03-08 17:00:15.437 -0800 OS Version: iPhone OS 2.2.1 (5H11a) Report Version: 103 Exception Type: EXC_BREAKPOINT (SIGTRAP) Exception Codes: 0x00000001, 0xe7ffdefe Crashed Thread: 0 Thread 0 Crashed: 0 dyld 0x2fe01060 dyld_fatal_error + 0 1 dyld 0x2fe088d4 dyld::_main(mach_header const*, unsigned long, int, char const**, char const**, char const**) + 3064 2 dyld 0x2fe0196c dyldbootstrap::start(mach_header const*, int, char const**, long) + 884 3 dyld 0x2fe01048 _dyld_start + 32 Thread 0 crashed with ARM Thread State: r0: 0x2fe23ca0 r1: 0x00000000 r2: 0x2fe23ca0 r3: 0x00000000 r4: 0x2ffff4e0 r5: 0x2ffff4bc r6: 0x2fe005c0 r7: 0x2ffffb00 r8: 0x00000004 r9: 0x2fe57cf0 r10: 0x2fe236c8 r11: 0x00000009 ip: 0x0000018d sp: 0x2ffff5b8 lr: 0x2fe088dc pc: 0x2fe01060 cpsr: 0x00000010 Binary Images: 0x2fe00000 - 0x2fe22fff dyld ??? (???) <f6a50d5f57a676b54276d0ecef46d5f0> /usr/lib/dyld My app uses OpenFeint and PinchMedia analytics. For PinchMedia, I'm linking using their provided .a file, and for OpenFeint, I'm compiling their code (as per their guidelines). The frameworks / libs I'm linking are: UIKit.framework (Weak) MapKit.framework (Weak) Foundation.framework CoreGraphics.framework OpenAL.framework AudioToolbox.framework libsqlite3 SystemConfiguration.framework CoreLocation.framework PinchMedia analytics Security.framework QuartzCore.framework CFNetwork.framework My base SDK is iPhone 3.0, and my Base OS Deployment Target is 2.2.1. There are two things I find weird: The app crashes even before the main method is invoked. The crash log looks exactly like the one posted here: http://stackoverflow.com/questions/2368689/objective-c-iphone-app-exc-breakpoint-sigtrap The user that sent me this crash is using a 2nd gen iPod Touch with OS 2.2.1. I wasn't able to reproduce the issue, but based on the comments in iTunes, it seems that more people is having the same issue.

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JSF ui:repeat and f:ajax giving wrong value for h:inputText after rerender.

- by Andrew

I have a list of questions and I can display them ok using a ui:repeat, but after clicking the Edit button the rerendered inputText is given the wrong question.id. For some reason, if you click Edit on the first item, the inputText value assigned is that of the second item in the list, even though other outputs (other than the h:inputText element) are correct. <h:form id="questionnaireForm"> <ui:repeat value="#{ProjectManager.currentProject.preQuestions}" var="question" varStatus="current" id="preQuestionsRepeat"> <div> <ui:fragment rendered="#{!question.editing}"> <f:ajax render="@form"> <p>#{question.id} #{question.questionText}</p> <h:inputText value="#{question.id}"/> <h:commandLink styleClass="link" action="#{question.setEditing}" value="Edit"> </h:commandLink> </f:ajax> </ui:fragment> </div> <div> <ui:fragment rendered="#{question.editing}"> <f:ajax render="@form"> <p>#{question.id} #{question.questionText}</p> <h:inputText value="#{question.id}"/> </f:ajax> </ui:fragment> </div> </ui:repeat> </h:form> Obviously I don't really want to edit the id. I just want the correct question.something to show up in my inputText :-) Perhaps I'm not using correctly? It seems fine according to my reading so far. Many thanks for your assistance.

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What is the difference between the Lego Mindstorms 1.0 and 2.0

- by Gavimoss

I am thinking about buying a mindstorms kit (I don't currently own one but I have used 1.0 at university) and I am a bit unsure as to the benefits of 2.0 over 1.0. I have seen other posts on the subject all saying generally 2.0 is better but I have some more specific questions about this that I can't seem to find any answers on. Apart from the different lego pieces and sensors you get with the 2.0 kit, is there any difference between a 1.0 nxt brick and 2.0 nxt brick? From what I can determine from other sources, they are the same except for the firmware installed. Am I right in saying I could buy a 1.0 kit and install the same firmware that comes with the 2.0 kit and the bricks would be the same or is the 1.0 brick not compatible with the 2.0 firmware??? Also, I plan to use a different programming language like c or java so I need to install specific firmware for that anyway like librcx or lejos right? So if using c or java as opposed to the provided lego coding methods it doesn't matter if I am using 1.0 or 2.0 (except for the lego pieces in the kit) am I right? In a nutshell, assuming I am using librcx or lejos and I don't care about the sensors and lego pieces included, is there any benefit to buying a 2.0 kit over the 1.0 kit? Thanks in advance

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SHA1 hashing in Delphi XE

- by Leonardo Herrera

Hello, I'm in the process of implementing XML digital signatures. I'm starting with little steps, so right now I want to solve the problem of SHA-1 hashing. There are lots of questions about this in SO: Digitially Sign Key with Lockbox Encryption library for Delphi Convert this php digital signing to Delphi Delphi: is there a version of LockBox for Delphi-XE Delphi 2010 Cryptography libraries ...and probably more. However, I'm using Delphi XE. So far, I've tried LockBox 2 (both the Songbeamer and Sourceforge versions), Lock Box 3, DCPCrypto2 and some others (Hashes is an easy to use unit which uses Windows crypto functions) I prepared a small test rig that gives me the following: LockBox2 FAILED: 1 ('abc') Got: '9f04f41a848514162050e3d68c1a7abb441dc2b5' Expected: 'a9993e364706816aba3e25717850c26c9cd0d89d' FAILED: 2 ('abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq') Got: '51d7d8769ac72c409c5b0e3f69c60adc9a039014' Expected: '84983e441c3bd26ebaae4aa1f95129e5e54670f1' LockBox3 FAILED: 1 ('abc') Got: '9f04f41a848514162050e3d68c1a7abb441dc2b5' Expected: 'a9993e364706816aba3e25717850c26c9cd0d89d' FAILED: 2 ('abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq') Got: '51d7d8769ac72c409c5b0e3f69c60adc9a039014' Expected: '84983e441c3bd26ebaae4aa1f95129e5e54670f1' DCPCrypto2 FAILED: 1 ('abc') Got: '9f04f41a848514162050e3d68c1a7abb441dc2b5' Expected: 'a9993e364706816aba3e25717850c26c9cd0d89d' FAILED: 2 ('abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq') Got: '51d7d8769ac72c409c5b0e3f69c60adc9a039014' Expected: '84983e441c3bd26ebaae4aa1f95129e5e54670f1' Hashes Test 1 passes Test 2 passes Have you succeeded in compile the mentioned libraries under Delphi XE and make them give the appropriate values? I'm particularly interested in DCPCrypt2 SelfTest procedure. Edit: I've added this answer with the fixed source code. Thank you all for your help, it is most appreciated.

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iPhone: In landscape-only, after first addSubview, UITableViewController doesn't rotate properly

- by Clay Bridges

A minimal illustrative Xcode project for this is available on github. On my UIWindow, when I add second (and subsequent) UITableView's as subviews, they do not rotate properly, and thus appear sideways. This is only tested in the Simulator. Here's a little code for you: - (void)applicationDidFinishLaunching:(UIApplication *)application { ShellTVC* viewA = [[ShellTVC alloc] initWithTitle:@"View A"]; ShellTVC* viewB = [[ShellTVC alloc] initWithTitle:@"View B"]; // The first subview added will rotate to landscape correctly. // Any subsequent subview added will not. // You may try this by various commentings and rearranging of these two statements. [window addSubview:[viewA tableView]]; [window addSubview:[viewB tableView]]; [window makeKeyAndVisible]; } viewB appears sideways. Comment out the addSubview for viewB, and viewA appears correctly. Do that for viewA only, and viewB appears correctly. I am not creating these UITableViewControllers via NIBs, though the UIWindow is. In case you are wondering, ShellTVC is-a UITableViewController, and implements this method: - (BOOL) shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return (interfaceOrientation == UIInterfaceOrientationLandscapeLeft); } Also, I have set the UIInterfaceOrientation in the plist file to UIInterfaceOrientationLandscapeLeft. Probably related -- and unanswered -- SO questions here and here.

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SQL Server transaction log backups,

- by krimerd

Hi there, I have a question regarding the transaction log backups in sql server 2008. I am currently taking full backups once a week (Sunday) and transaction log backups daily. I put full backup in folder1 on Sunday and then on Monday I also put the 1st transaction log backup in the same folder. On tuesday, before I take the 2nd transaction log backup I move the first transaction log backup from folder1 an put it into folder2 and then I take the 2nd transaction log backup and put it in the folder1. Same thing on Wed, Thurs and so on. Basicaly in folder1 I always have the latest full backup and the latest transaction log backup while the other transaction log backups are in folder2. My questions is, when sql server is about to take, lets say 4th (Thursday) transaction log backup, does it look for the previous transac log backups (1st, 2nd, and 3rd) so that this new backup will only include the transactions from the last backup or it has some other way of knowing whether there are other transac log backups. Basically, I am asking this because all my transaction log backups seem to be about the same size and I thought that their size will depend on the amount of transactions since the last transaction log backup. Can anyone please explain if my assumptions are right? Thanks...

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GNU Make: How to call $(wildcard) within $(eval)

- by bengineerd

I'm trying to create a generic build template for my Makefiles, kind of like they discuss in the eval documentation. I can't seem to get the wildcard function to work within an eval. The basic code I'm having issues with looks like this. SRC_DIR = ./src/ PROG_NAME = test define PROGRAM_template $(1)_SRC_DIR = $(join $(SRC_DIR), $(1)/) $(1)_SRC_FILES = $(wildcard $$($(1)_SRC_DIR)*.c) endef $(eval $(call PROGRAM_template, $(PROG_NAME))) all: @echo $(test_SRC_DIR) @echo $(test_SRC_FILES) @echo $(wildcard $(wildcard $(test_SRC_DIR)*.c) When I run make with this, the output is ./src/test [correct list of all .c files in ./src/test/] Basically, the wildcard call within PROGRAM_template is not being eval'd as I expect it. The call results in an empty list. The join call is being eval'd correctly though. So, what am I doing wrong? My guess is that $$($(1)_SRC_DIR) is not correct, but I can't figure out the right way to do it. EDIT Once this was solved, it didn't take long for me to hit another issue with eval. I posted it as a new question at http://stackoverflow.com/questions/2428506/workaround-for-gnu-make-3-80-eval-bug

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Wrapping malloc - C

- by Appu

I am a beginner in C. While reading git's source code, I found this wrapper function around malloc. void *xmalloc(size_t size) { void *ret = malloc(size); if (!ret && !size) ret = malloc(1); if (!ret) { release_pack_memory(size, -1); ret = malloc(size); if (!ret && !size) ret = malloc(1); if (!ret) die("Out of memory, malloc failed"); } #ifdef XMALLOC_POISON memset(ret, 0xA5, size); #endif return ret; } Questions I couldn't understand why are they using malloc(1)? What does release_pack_memory does and I can't find this functions implementation in the whole source code. What does the #ifdef XMALLOC_POISON memset(ret, 0xA5, size); does? I am planning to reuse this function on my project. Is this a good wrapper around malloc? Any help would be great.

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Emacs recursive project search

- by hekevintran

I am switching to Emacs from TextMate. One feature of TextMate that I would really like to have in Emacs is the "Find in Project" search box that uses fuzzy matching. Emacs sort of has this with ido, but ido does not search recursively through child directories. It searches only within one directory. Is there a way to give ido a root directory and to search everything under it? Update: The questions below pertain to find-file-in-project.el from Michal Marczyk's answer. If anything in this message sounds obvious it's because I have used Emacs for less than one week. :-) As I understand it, project-local-variables lets me define things in a .emacs-project file that I keep in my project root. How do I point find-file-in-project to my project root? I am not familiar with regex syntax in Emacs Lisp. The default value for ffip-regexp is: ".*\\.\$rb\\|js\\|css\\|yml\\|yaml\\|rhtml\\|erb\\|html\\|el\$" I presume that I can just switch the extensions to the ones appropriate for my project. Could you explain the ffip-find-options? From the file: (defvar ffip-find-options "" "Extra options to pass to `find' when using find-file-in-project. Use this to exclude portions of your project: \"-not -regex \\".vendor.\\"\"") What does this mean exactly and how do I use it to exclude files/directories? Could you share an example .emacs-project file?

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How to implement YQL paging?

- by Erik Vold

I've read the YQL guide, and I keep reviewing http://developer.yahoo.com/yql/guide/yql-o...entables-paging and I have been looking at a few examples, but I'm still left pretty confused how YQL paging works. The problem that I am trying to tackle is creating a YQL open data table for the Mozilla labs Jetpack Gallery's jetpacks pages http://jetpackgallery.mozillalabs.com/jetpacks You flip through the pages of jetpacks with the ?page query variable and there is an order_by query variable. You can only see 10 results per page. Questions: List item Should I use or ? How do I specify the query parameter that indicates the page? in this case it is the 'page' query parameter. I am assuming I should use: <urls><url>http://jetpackgallery.mozillalabs.com/jetpacks</url></urls> is this correct? In the execute element, I will need to extract the details for each jetpack on the page? if so how would I organize that for the response.object? Can anyone provide some help? or perhaps point to a data table that I can look at as a reference? or better documentation on how paging works?

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Inheriting from ViewPage forces explicit casting of model in view

- by Martin Hansen

I try to inhering from ViewPage as shown in this question http://stackoverflow.com/questions/370500/inheriting-from-viewpage But I get a Compiler Error Message: CS1061: 'object' does not contain a definition for 'Spot' and no extension method 'Spot' accepting a first argument of type 'object' could be found (are you missing a using directive or an assembly reference?) My viewpage, normally I can do Model.ChildProperty(Spot) when I inherit from ViewPage directly, so I do that here too. But it fails. <%@ Page Language="C#" Inherits="Company.Site.ViewPageBase<WebSite.Models.SpotEntity>" %> <h1><%= Html.Encode(Model.Spot.Title) %></h1> To get it working correctly I have to do like this: <%@ Page Language="C#" Inherits="Company.Site.ViewPageBase<WebSite.Models.SpotEntity>" %> <h1><%= Html.Encode(((WebSite.Models.SpotEntity)Model).Spot.Title) %></h1> Here is my classes: namespace Company.Site { public class ViewPageBase<TModel> : Company.Site.ViewPageBase where TModel:class { private ViewDataDictionary<TModel> _viewData; [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")] public new ViewDataDictionary<TModel> ViewData { get { if (_viewData == null) { SetViewData(new ViewDataDictionary<TModel>()); } return _viewData; } set { SetViewData(value); } } protected override void SetViewData(ViewDataDictionary viewData) { _viewData = new ViewDataDictionary<TModel>(viewData); base.SetViewData(_viewData); } } public class ViewPageBase : System.Web.Mvc.ViewPage { } } So how do I get it to work without the explicit cast?

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SVM Classification - minimum number of input sets for each class

- by Amol Joshi

Im trying to build an app to detect images which are advertisements from the webpages. Once I detect those Ill not be allowing those to be displayed on the client side. From the help that I got here in stackoverflow, I thought SVM is the best approach to my aim. So, I have coded SVM and an SMO myself. The dataset which I have got from UCI data repository has 3280 instances ( Link to Dataset- http://archive.ics.uci.edu/ml/datasets/Internet+Advertisements )where around 400 of them are from class representing Advertisement images and rest of them representing non-advertisement images. Right now Im taking the first 2800 input sets and training the SVM. But after looking at the accuracy rate I realised that most of those 2800 input sets are from non-advertisement image class. So Im getting very good accuracy for that class. So what can I do here? About how many input set shall I give to SVM to train and how many of them for each class? Thanks. Cheers. ( Basically made a new question because the context was different from my previous question. http://stackoverflow.com/questions/1991113/optimization-of-neural-network-input-data )

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what can be causes of http server crash?

- by mithunmo

Hello , I am using WAMP server on Windows XP. - Apache 2.2.11 - MySQL 5.1.36 (INNODB engine) - PHP 5.3.0 I observe that my WAMP server crashes in the following scenarios 1) IF I use a Low end PC ( low processor speed and low RAM) 2) After making some changes to httpd.conf file .For eg changing the Allow from IP address . But here it crashes only once and then it starts to work fine. 3) Random crashes CRASH LOG szAppName : httpd.exe szAppVer : 2.2.11.0 szModName : php5ts.dll szModVer : 5.3.0.0 offset : 0000c309 C:\DOCUME~1\blrcom\LOCALS~1\Temp\WERc677.dir00\httpd.exe.mdmp C:\DOCUME~1\blrcom\LOCALS~1\Temp\WERc677.dir00\appcompat.txt My questions 1) Does high CPU utilization/LOW RAM can also cause the HTTP server to crash ? 2) excessive file reading as in every 10 seconds ? 3) unlimited script execution time . I have set the maximum execution time in php script to 0 as my script has to execute for sometimes 2-3 days. Is there any way to avoid this ? 4) Access to Database ? Should we use lock before reading and writing Can these be the reasons for random wamp server crashes ? OR is is some other programming error ? Please guide me . Regards, Mithun

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Lisp Style question label local functions or not?

- by Andrew Myers

I was wondering if there is a standard practice regarding the use of labels in Lisp. I've been messing around with a Lisp implementation of the algorithm described in the first answer here http://stackoverflow.com/questions/352203/generating-permutations-lazily My current version uses labels to break out portions of functionality. (defun next-permutation (pmute) (declare (vector pmute)) (let ((len (length pmute))) (if (> len 2) (labels ((get-pivot () (do ((pivot (1- len) (1- pivot))) ((or (= pivot 0) (< (aref pmute (1- pivot)) (aref pmute pivot))) pivot))) (get-swap (pivot) (let ((swp (1- len))) (loop for i from (1- len) downto pivot do (if (or (and (> (aref pmute i) (aref pmute (1- pivot))) (< (aref pmute i) (aref pmute swp))) (< (aref pmute swp) (aref pmute (1- pivot)))) (setf swp i))) swp)) (next (swp pivot) (rotatef (aref pmute (1- pivot)) (aref pmute swp)) (reverse-vector pmute pivot (1- len)))) (let ((piv (get-pivot))) (if (> piv 0) (next (get-swap piv) piv) nil)))))) Since each label is only called once I was wondering if this is considered bad practice since the only reason to do it in this case is for aesthetic reasons. I would argue that the current version with labels is clearer but that may go against common wisdom that I'm not aware of, being new to Lisp.

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Can someone please explain this lazy evaluation code?

- by Tejs

So, this question was just asked on SO: http://stackoverflow.com/questions/2740001/how-to-handle-an-infinite-ienumerable My sample code: public static void Main(string[] args) { foreach (var item in Numbers().Take(10)) Console.WriteLine(item); Console.ReadKey(); } public static IEnumerable<int> Numbers() { int x = 0; while (true) yield return x++; } Can someone please explain why this is lazy evaluated? I've looked up this code in Reflector, and I'm more confused than when I began. Reflector outputs: public static IEnumerable<int> Numbers() { return new <Numbers>d__0(-2); } For the numbers method, and looks to have generated a new type for that expression: [DebuggerHidden] public <Numbers>d__0(int <>1__state) { this.<>1__state = <>1__state; this.<>l__initialThreadId = Thread.CurrentThread.ManagedThreadId; } This makes no sense to me. I would have assumed it was an infinite loop until I put that code together and executed it myself.

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C++/CLI managed thread cleanup

- by Guillermo Prandi

Hi. I'm writing a managed C++/CLI library wrapper for the MySQL embedded server. The mysql C library requires me to call mysql_thread_init() for every thread that will be using it, and mysql_thread_end() for each thread that exits after using it. Debugging any given VB.Net project I can see at least seven threads; I suppose my library will see only one thread if VB doesn't explicitly create worker threads itself (any confirmations on that?). However, I need clients to my library to be able to create worker threads if they need to, so my library must be thread-aware to some degree. The first option I could think of is to expose some "EnterThread()" and "LeaveThread()" methods in my class, so the client code will explicitly call them at the beginning and before exiting their DoWork() method. This should work if (1) .Net doesn't "magically" create threads the user isn't aware of and (2) the user is careful enough to have the methods called in a try/finally structure of some sort. However, I don't like it very much to have the user handle things manually like that, and I wonder if I could give her a hand on that matter. In a pure Win32 C/C++ DLL I do have the DllMain DLL_THREAD_ATTACH and DLL_THREAD_DETACH pseudo-events, and I could use them for calling mysql_thread_init() and mysql_thread_end() as needed, but there seem to be no such thing in C++/CLI managed code. At the expense of some performance (not much, I think) I can use TLS for detecting the "usage from a new thread" case, but I can imagine no mechanism for the thread exiting case. So, my questions are: (1) could .net create application threads without the user being aware of them? and (2) is there any mechanism I could use similar to DLL_THREAD_ATTACH / DLL_THREAD_DETACH from managed C++/CLI? Thanks in advance.

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How does one convert 16-bit RGB565 to 24-bit RGB888?

- by jleedev

I’ve got my hands on a 16-bit rgb565 image (specifically, an Android framebuffer dump), and I would like to convert it to 24-bit rgb888 for viewing on a normal monitor. The question is, how does one convert a 5- or 6-bit channel to 8 bits? The obvious answer is to shift it. I started out by writing this: uint16_t buf; while (read(0, &buf, sizeof buf)) { unsigned char red = (buf & 0xf800) >> 11; unsigned char green = (buf & 0x07c0) >> 5; unsigned char blue = buf & 0x003f; putchar(red << 3); putchar(green << 2); putchar(blue << 3); } However, this doesn’t have one property I would like, which is for 0xffff to map to 0xffffff, instead of 0xf8fcf8. I need to expand the value in some way, but I’m not sure how that should work. The Android SDK comes with a tool called ddms (Dalvik Debug Monitor) that takes screen captures. As far as I can tell from reading the code, it implements the same logic; yet its screenshots are coming out different, and white is mapping to white. Here’s the raw framebuffer, the smart conversion by ddms, and the dumb conversion by the above algorithm. (By the way, this conversion is implemented in ffmpeg, but it’s just performing the dumb conversion listed above, leaving the LSBs at all zero.) I guess I have two questions: What’s the most sensible way to convert rgb565 to rgb888? How is DDMS converting its screenshots?

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Need help using the DefaultModelBinder for a nested model.

- by Will

There are a few related questions, but I can't find an answer that works. Assuming I have the following models: public class EditorViewModel { public Account Account {get;set;} public string SomeSimpleStuff {get;set;} } public class Account { public string AccountName {get;set;} public int MorePrimitivesFollow {get;set;} } and a view that extends ViewPage<EditorViewModel> which does the following: <%= Html.TextBoxFor(model => model.Account.AccountName)%> <%= Html.ValidationMessageFor(model => model.Account.AccountName)%> <%= Html.TextBoxFor(model => model.SomeSimpleStuff )%> <%= Html.ValidationMessageFor(model => model.SomeSimpleStuff )%> and my controller looks like: [HttpPost] public virtual ActionResult Edit(EditorViewModel account) { /*...*/ } How can I get the DefaultModelBinder to properly bind my EditorViewModel? Without doing anything special, I get an empty instance of my EditorViewModel with everything null or default. The closest I've come is by calling UpdateModel manually: [HttpPost] public virtual ActionResult Edit(EditorViewModel account) { account.Account = new Account(); UpdateModel(account.Account, "Account"); // this kills me: UpdateModel(account); This successfully updates my Account property model, but when I call UpdateModel on account (to get the rest of the public properties of my EditorViewModel) I get the completely unhelpful "The model of type ... could not be updated." There is no inner exception, so I can't figure out what's going wrong. What should I do with this?

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Can I autogenerate/compile code on-the-fly, at runtime, based upon values (like key/value pairs) parsed out of a configuration file?

- by Kumba

This might be a doozy for some. I'm not sure if it's even 100% implementable, but I wanted to throw the idea out there to see if I'm really off of my rocker yet. I have a set of classes that mimics enums (see my other questions for specific details/examples). For 90% of my project, I can compile everything in at design time. But the remaining 10% is going to need to be editable w/o re-compiling the project in VS 2010. This remaining 10% will be based on a templated version of my Enums class, but will generate code at runtime, based upon data values sourced in from external configuration files. To keep this question small, see this SO question for an idea of what my Enums class looks like. The templated fields, per that question, will be the MaxEnums Int32, Names String() array, and Values array, plus each shared implementation of the Enums sub-class (which themselves, represent the Enums that I use elsewhere in my code). I'd ideally like to parse values from a simple text file (INI-style) of key/value pairs: [Section1] Enum1=enum_one Enum2=enum_two Enum3=enum_three So that the following code would be generated (and compiled) at runtime (comments/supporting code stripped to reduce question size): Friend Shared ReadOnly MaxEnums As Int32 = 3 Private Shared ReadOnly _Names As String() = New String() _ {"enum_one", "enum_two", "enum_three"} Friend Shared ReadOnly Enum1 As New Enums(_Names(0), 1) Friend Shared ReadOnly Enum2 As New Enums(_Names(1), 2) Friend Shared ReadOnly Enum3 As New Enums(_Names(2), 4) Friend Shared ReadOnly Values As Enums() = New Enums() _ {Enum1, Enum2, Enum3} I'm certain this would need to be generated in MSIL code, and I know from reading that the two components to look at are CodeDom and Reflection.Emit, but I was wondering if anyone had working examples (or pointers to working examples) versus really long articles. I'm a hands-on learner, so I have to have example code to play with. Thanks!

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How do you use asynchronous ORMs without huge callback chains?

- by hornairs

I'm using the relatively immature Joose Javascript ORM plugin (project page) to persist objects in an Appcelerator Titanium (company page) mobile project. Since it's client side storage, the application has to check to see if the database is initialized before starting up the ORM since it inspects the DB tables to construct the classes. My problem is that this sequence of operations (and if this one is like this, other things down the road) takes a lot of callbacks to complete. I have a lot of jumping around in the code that isn't apparent to a maintainer and results in some complex call graphs and whatnot. So, I ask these questions: How would you asynchronously initialize a database and populate it with seed data using an ORM that needs the schema to be correct to function? Do you have any general strategies or links for async/event driven programming and keeping the call graph simple and understandable? Do you have any suggestions for Javascript ORMs/meta object systems that work with HTML 5 as a storage engine and are hopefully framework agnostic? Am I just a big newb and should be able to work this out with ease? Thanks folks!

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Struggling with currency in Cocoa.

- by Meltemi

I'm trying to do something I'd think would be fairly simple: Let a user input a dollar amount, store that amount in an NSNumber (NSDecimalNumber?), then display that amount formatted as currency again at some later time. My trouble is not so much with the setNumberStyle:NSNumberFormatterCurrencyStyle and displaying floats as currency. The trouble is more with how said numberFormatter works with this UITextField. I can find few examples. This thread from November and this one give me some ideas but leaves me with more questions. I am using the UIKeyboardTypeNumberPad keyboard and understand that I should probably show $0.00 (or whatever local currency format is) in the field upon display then as a user enters numerals to shift the decimal place along: Begin with display $0.00 Tap 2 key: display $0.02 Tap 5 key: display $0.25 Tap 4 key: display $2.54 Tap 3 key: display $25.43 Then [numberFormatter numberFromString:textField.text] should give me a value I can store in my NSNumber variable. Sadly I'm still struggling: Is this really the best/easiest way? If so then maybe someone can help me with the implementation? I feel UITextField may need a delegate responding to every keypress but not sure what, where and how to implement it?! Any sample code? I'd greatly appreciate it! I've searched high and low... Edit1: So I'm looking into NSFormatter's stringForObjectValue: and the closest thing I can find to what benzado recommends: UITextViewTextDidChangeNotification. Having really tough time finding sample code on either of them...so let me know if you know where to look?

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Java Swingworker: Not as encapsulated class

- by Thomas Matthews

I'm having problems passing information, updating progress and indicating "done" with a SwingWorker class that is not an encapsulated class. I have a simple class that processes files and directories on a hard drive. The user clicks on the Start button and that launches an instance of the SwingWorker. I would like to print the names of the files that are processed on the JTextArea in the Event Driven Thread from the SwingWorker as update a progress bar. All the examples on the web are for an nested class, and the nested class accesses variables in the outer class (such as the done method). I would also like to signal the Event Driven Thread that the SwingWorker is finished so the EDT can perform actions such as enabling the Start button (and clearing fields). Here are my questions: 1. How does the SwingWorker class put text into the JTextArea of the Event Driven Thread and update a progress bar? How does the EDT determine when the {external} SwingWorker thread is finished? {I don't want the SwingWorker as a nested class because there is a lot of code (and processing) done.}

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TypeConverter prevents ApplyPropertyChanges in EntityFramework

- by Felix

I ran into an interesting problem (hopefully, interesting not just for me :) I am running Entity Framework 1 (.NET 3.5) and ASP.NET MVC 2. I have a Customer class that has many-to-one relationship with Country class (in other words, Country is a lookup table for customers - I described more in this post: http://stackoverflow.com/questions/2404801/explicit-casting-doesnt-work-in-default-model-binding ) I got TypeConverter to work; so I am getting a perfect object into controller's Post method. Create works fine; however, in Edit I am getting the following error when I call ApplyPropertyChanges: The existing object in the ObjectContext is in the Added state. Changes can only be applied when the existing object is in an unchanged or modified state. The controller code is fairly trivial: public ActionResult Edit(Customer customerToEdit) { if (ModelState.IsValid) { Customer cust = (Customer)context.GetObjectByKey( new EntityKey("BAEntities.Customers", "CustomerID", customerToEdit.CustomerID)); context.ApplyPropertyChanges(cust.EntityKey.EntitySetName, customerToEdit); context.SaveChanges(); } return View(...); } If I remove country from the form, it works fine; and if I assign dropdown value to EntityReference "manually" - it works as well. TypeConverter code is also fairly simple, but I've never used TypeConverter before, so I may be missing something here: public override object ConvertFrom(ITypeDescriptorContext typeContext, CultureInfo culture, object value) { if (value is string) { int countryID = Int16.Parse((string)value); Country country = (Country)context.GetObjectByKey( new EntityKey("BAEntities.Countries", "CountryID", countryID)); return country; } return base.ConvertFrom(typeContext, culture, value); }

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