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• Does anyone else think instance variables are problematic in database-backed applications?

  - by Ben Aston

  It occurs to me that state control in languages like C# is not well supported. By this, I mean, it is left upto the programmer to manage the state of in-memory objects. A common use-case is that instance variables in the domain-model are copies of information residing in persistent storage (i.e. the database). Clearly this violates the single point of authority principle, and "synchronisation" has to be managed by the developer. I envisage a system where instead of instance variables, we have simple public access/mutator methods marked with attributes that link them to the database, and where reads and writes are mediated by a framework that decides whether to hit the database. Does such a system exist? Am I completely missing the point, or is there some truth to this idea?

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• How to check if a process is running or got segfaulted or terminated in linux from its pid in my mai

  - by rkbang

  Hello all, I am invoking several processes in my main and I can get the pid of that processes. Now I want to wait until all this processes have been finished and then clear the shared memory block from my parent process. Also if any of the process not finished and segfaulted I want to kill that process. So how to check from the pid of processes in my parent process code that a process is finished without any error or it gave broke down becoz of runtime error or any other cause, so that I can kill that process. Also what if I want to see the status of some other process which is not a child process but its pid is known. Code is appreciated( I am not looking for script but code ).

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• Reading a memorystream

  - by user1842828

  Using several examples here on StackOverflow I thought the following code would decompress a gzip file then read the memory-stream and write it's content to the console. No errors occur but I get no output. public static void Decompress(FileInfo fileToDecompress) { using (FileStream originalFileStream = fileToDecompress.OpenRead()) { string currentFileName = fileToDecompress.FullName; string newFileName = currentFileName.Remove(currentFileName.Length - fileToDecompress.Extension.Length); using (FileStream decompressedFileStream = File.Create(newFileName)) { using (GZipStream decompressionStream = new GZipStream(originalFileStream, CompressionMode.Decompress)) { MemoryStream memStream = new MemoryStream(); memStream.SetLength(decompressedFileStream.Length); decompressedFileStream.Read(memStream.GetBuffer(), 0, (int)decompressedFileStream.Length); memStream.Position = 0; var sr = new StreamReader(memStream); var myStr = sr.ReadToEnd(); Console.WriteLine("Stream Output: " + myStr); } } } }

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• small string optimization for vector?

  - by BuschnicK

  I know several (all?) STL implementations implement a "small string" optimization where instead of storing the usual 3 pointers for begin, end and capacity a string will store the actual character data in the memory used for the pointers if sizeof(characters) <= sizeof(pointers). I am in a situation where I have lots of small vectors with an element size <= sizeof(pointer). I cannot use fixed size arrays, since the vectors need to be able to resize dynamically and may potentially grow quite large. However, the median (not mean) size of the vectors will only be 4-12 bytes. So a "small string" optimization adapted to vectors would be quite useful to me. Does such a thing exist? I'm thinking about rolling my own by simply brute force converting a vector to a string, i.e. providing a vector interface to a string. Good idea?

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• reading specific lines from a file

  - by MacUsers

  What's the best way of reading only the specific lines (based on matching text) from a file? This is what I'm doing now: match_txt = "lhcb" for inFile in os.listdir('.'): readFile = open(inFile, 'r') lines = readFile.readlines() readFile.close() for line in lines: if line.find(match_txt)==0: #< do stuff here > i.e. I'm reading the lines, only with "lhcb" in it, from all the files in the present directory one by one. Is it the best way of doing that? Can it be done without loading the whole file in the memory in the first place?

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• Bitmap.Save problems

  - by user284026

  Hello, can anyone tell me if you know to be a problem with Bitmap and steganography for WM 6? I am working on a project and i have to hide a digital signature in a bitmap. The algorithm works perfect, as in untill i have the image on the memory the bitmap contains the modified bytes. But after i save the image (Bitmap.Save()) and I reopen the image, than those bytes are lost. When i say lost i mean they are the orriginal bytes from when the picture was taken. Thank you.

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• How do I bind a key to "the function represented by the following key sequence"?

  - by katrielalex

  I'm just starting to learn emacs (woohoo!) and I've been mucking around in my .emacs quite happily. Unfortunately, I don't know Lisp yet, so I'm having issues with the basics. I've already remapped a few keys until I fix my muscle memory: (global-set-key (kbd "<f9>") 'recompile) That's fine. But how can I tell a key to 'simulate pressing several keys'? For instance, I don't know, make <f1> do the same as C-u 2 C-x } (widen buffer by two chars). One way is to look up that C-x } calls shrink-window-horizontally, and do some sort of lambda thing. This is of course the neat and elegant way (how do you do this?). But surely there's a way to define <f1> to send the keystrokes C-u 2 C-x }?

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• How can I disable Java garbage collector ?

  - by Nelson

  Hi, we have a PHP webapp that calls a java binary to produce a pdf report (with jasperreport), the java binary outpus pdf to standart output and exits, the php then send the pdf to browser. This java command lasts about 3 to 6 seconds, I think when it lasts 6 second it's because the GC kicks in, so I would like to disable it because anyway when the command exits all memory is returned.. I would like to know how to disable it for Java 1.4.2 and for Java 1.6.0 because we are currently testing both JVM to see which performs faster.. Thanks

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• C++'s unordered_map / hash_map / Google's dense_hash - how to input binary data (buf+len) and insert

  - by shlomif

  Hi all, I have two questions about Google's dense_hash_map, which can be used instead of the more standard unordered_map or hash_map: How do I use an arbitrary binary data memory segment as a key: I want a buffer+length pair, which may still contain some NUL (\0) characters. I can see how I use a NUL-terminated char * string , but that's not what I want. How do I implement an operation where I look if a key exists, and if not - insert it and if it does return the pointer to the existing key and let me know what actually happened. I'd appreciate it if anyone can shed any light on this subject. Regards, -- Shlomi Fish

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• Problems opening large csv file

  - by John Tyler

  I have a csv file that is 100mb in size. I need to parse some data out of it into a new format. I tried PHP, but keep running into memory issues. After around the first 150 "rows" or so, the script poops out. This is even on the localhost, and doing everything I can to tune the PHP settings, including max_memory and script_execution_time. Now before I continue, I'd like to know if Python will poop out on me too. Or if I will have to use C++. Can someone name good csv libraries for for these programmin langueage? The file is quoted csv. I mean scheiza I can't even open this text file in OpenOffice without it dying on me. (then again, Java sux as bad as PHP)

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• Handler not yet determined error

  - by SourceC

  Hello, I don’t know anything about deploying a website, so I probably made some stupid mistake. Anyways, I opened IIS 7 manager, created new virtual directory ( via Add Application ) and pointed it to physical directory where Visual studio saved my Web project. But when I tried to request an .aspx page, browser reported the following error (I won’t post the whole error, but just the interesting bits): Handler: Not yet determined Config Error: Cannot read configuration file due to insufficient permissions Logon User: Not yet determined A) why is handler not yet determined? As far as I know, IIS7 does have Asp.Net handler registered?! B) Why wouldn’t IIS have sufficient permissions? Does that mean I should give IIS higher privileges? Or does Asp.Net runtime have insufficient permissions? C) Could the error also be due to the fact that perhaps it expected the user to authenticate itself? I’m assuming this due to Logon user not yet being determined? D) And finally, any ideas how to make it work? thanx

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• How do I write a Java text file viewer for big log files

  - by Hannes de Jager

  I am working on a software product with an integrated log file viewer. Problem is, its slow and unstable for really large files because it reads the whole file into memory when you view a log file. I'm wanting to write a new log file viewer that addresses this problem. What are the best practices for writing viewers for large text files? How does editors like notepad++ and VIM acomplish this? I was thinking of using a buffered Bi-directional text stream reader together with Java's TableModel. Am I thinking along the right lines and are such stream implementations available for Java?

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• delete & new in c++

  - by singh

  Hi This may be very simple question,But please help me. i wanted to know what exactly happens when i call new & delete , For example in below code char * ptr=new char [10]; delete [] ptr; call to new returns me memory address. Does it allocate exact 10 bytes on heap, Where information about size is stored.When i call delete on same pointer,i see in debugger that there are a lot of byte get changed before and after the 10 Bytes. Is there any header for each new which contain information about number of byte allocated by new. Thanks a lot

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• How do stream rows from a MSSQL table into a .NET app, in 10000 row chunks?

  - by Gravitas

  I have a table with 300 million rows in Microsoft SQL Server 2008 R2. There is a clustered index on the date column [DataDate] which means that the entire table is ordered by the date column. How do I stream out the data from this table, into my .NET application, in 10000 row chunks? Environment: Using C#. Have to be able to pause the data stream at any point, to allow the client to process the rows. Unfortunately, cannot use a select * from as this will select the entire table (its 50GB - it won't fit into memory).

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• c++ polymorphism and other function question

  - by aharont

  i have got this code: class father{ public: virtual void f() { cout<<1;} }; class son:public father{ public: void f() {cout<<2;} }; void test (father x){x.f();} int main(){ son s; test(s); } the question says: the output is '1', what is the rule about polymorphism that the programmer forgot and how can i fix it so the output would be '2'? there is another rule that the programmer forgot when he wrote the father class, and he need to add an empty function to avoid problems from other sons of the father class. what is the rule and what is the missing function? another question write the g function so the next code would run with no crashes int x=11; g(x)=22;

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• Is a full list returned first and then filtered when using linq to sql to filter data from a databas

  - by RJ

  This is probably a very simple question that I am working through in an MVC project. Here's an example of what I am talking about. I have an rdml file linked to a database with a table called Users that has 500,000 rows. But I only want to find the Users who were entered on 5/7/2010. So let's say I do this in my UserRepository: from u in db.GetUsers() where u.CreatedDate = "5/7/2010" select u (doing this from memory so don't kill me if my syntax is a little off, it's the concept I am looking for) Does this statement first return all 500,000 rows and then filter it or does it only bring back the filtered list?

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• Firefox: how to apply XSLT from plugin to opened XML document? (how to replace document with another

  - by aloispaulin

  Hi! I've developed a plug-in for Firefox, that can read and manipulate the content of the currently opened document. I would like to apply a XLST to the document in case it is XML. I have no problem to read the XML document and apply a XSLT to it in memory, however, I have no idea of how to replace the existing document with the newly created one. Thus, I see two possible scenarios: a) I replace the document with the result of the transformation b) I apply the XSLT directly to the XML All my attempts to realize one of both possible solutions have failed... Hoping the community can provide help! Many tnx in advance! Alois

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• Storing expression template functors

  - by UncaughtException

  Hello guys, at the moment I'm really interested in expression templates and want to code a library for writing and differentiating mathematical functions with a lambda-style syntax. At the moment, I'm able to write (_x * _x)(2); and get the correct result 4. But I would really like to do something like MathFunction f = _x * _x; f(2);, but I don't have any ideas on how to cope with the recursive expression templates on the right side. Is it possible to achieve this without using the 'auto'-Keyword instead of MathFunction or having to make the operator() virtual? Thanks for your help!

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• How to set -Xbootclasspath for a JRE with a custom launcher?

  - by Tom

  I have a Java application which is using a certain Java Runtime Environment. The application uses it's own launcher to startup the java virtual machine. No use of the java.exe, javaw.exe, javaws.exe binaries is being made -- as the application seems to have it's own launcher which is a different executable. This custom launcher is using the rest of the JRE files, such as bin/client/jvm.dll and rt.jar package etc. Now, the problem is that I want to set a boot class path for this custom launcher. The custom launcher does not support the -Xbootclasspath command line parameter, like the default java.exe does. Is there any way for me to set the boot class path now for this java runtime environment? Thanks in advance. Some things to keep in mind: I do not have the source of this application This is meant for self and personal debugging use only, not for distribution

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• How can one use multi threading in php applications

  - by Steve Obbayi

  Is there a realistic way of implementing a multi-threaded model in php whether truly or just simulating it. Some time back it was suggested that you can force the operating system to load another instance of the php executable and handle other simultaneous processes. The problem with this is that when the php code finished executing the php instance remains in memory because there is no way to kill it from within php. so if you are simulating several threads you can imagine whats going to happen. So am still looking for a way multi-threading can be done or simulated effectively from within php. Any ideas?

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• UITableView with contact image problems.

  - by prathumca

  As par my app requirement, I'm showing the contact images in a UITableView as shown below. ABRecordRef contact = [self getContact]; if(contact && ABPersonHasImageData(contact)) { UIImage *contactImage = [UIImage imageWithData:(NSData*)ABPersonCopyImageData(contact)]; callImage.image = contactImage; } I've two problems if I use the above code segment. Table Scrolling is too slow. If comment the above code, then UITable responds very fast. Memory Management. My app started using 25 - 30 MB of RAM. Is there any better way to avoid the above two problems?

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• Does C++ require a destructor call for each placement new?

  - by Josh Haberman

  I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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• Is it a good idea to define a variable in a local block for a case of a switch statement?

  - by Paperflyer

  I have a rather long switch-case statement. Some of the cases are really short and trivial. A few are longer and need some variables that are never used anywhere else, like this: switch (action) { case kSimpleAction: // Do something simple break; case kComplexAction: { int specialVariable = 5; // Do something complex with specialVariable } break; } The alternative would be to declare that variable before going into the switch like this: int specialVariable = 5; switch (action) { case kSimpleAction: // Do something simple break; case kComplexAction: // Do something complex with specialVariable break; } This can get rather confusing since it is not clear to which case the variable belongs and it uses some unnecessary memory. However, I have never seen this usage anywhere else. Do you think it is a good idea to declare variables locally in a block for a single case?

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• C++ Array of pointers: delete or delete []?

  - by Jasper

  Cosider the following code: class Foo { Monster* monsters[6]; Foo() { for (int i = 0; i < 6; i++) { monsters[i] = new Monster(); } } virtual ~Foo(); } What is the correct destructor? this: Foo::~Foo() { delete [] monsters; } or this: Foo::~Foo() { for (int i = 0; i < 6; i++) { delete monsters[i]; } } I currently have the uppermost constructor and everything is working okey, but of course I cannot see if it happens to be leaking... Personally, I think the second version is much more logical considering what I am doing. Anyway, what is the "proper" way to do this?

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• Is it a good practice to create a reference to application context and use it anywhere?

  - by kknight

  I have to use context in many places of my code such as database operations, preference operations, etc. I don't want to pass in context for every method. Is it a good practice to create a reference to application context at the main Activity and use it anywhere such as database operations? So, I don't need some many context in method parameters, and the code can avoid position memory leak due to use of Activity Context. public class MainActivity extends Activity { public static Context s_appContext; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); s_appContext = this.getApplicationContext();

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