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• No Parameterless Constructor defined for - ViewModel with UOW

  - by TheVillageIdiot

  I have a view model class which uses UnitOfWork to some database operations like fetching of items to create select lists and IPrincipal for some auditing (like modified by etc.). It cannot work without this UOW. I have configured my web site to use Ninject to inject UOW into Controllers. From controller I pass this UOW when creating view model. But when performing POST operation I am getting No parameterless constructor defined for this object. I have few SelectList type of properties which I have excluded with Bind attribute. How can I overcome this problem? Can I configure Ninject to create the objects of this type and make ModelBinder use it?

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• Appropriate data structure for a buffer of the packets

  - by psihodelia

  How to implement a buffer of the packets where each packet is of the form: typedef struct{ int32 IP; //4-byte IP-address int16 ID; //unique sequence id }t_Packet; What should be the most appropriate data structure which: (1) allows to collect at least 8000 such packets (fast Insert and Delete operations) (2) allows very fast filtering using IP address, so that only packets with given IP will be selected (3) allows very fast find operation using ID as a key (4) allows very fast (2), then (3) within filtered results ? RAM size does matter, e.g. no huge lookup table is possible to use.

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• Pattern for iPhone background loading during init?

  - by Rob S.

  Hi everyone, I'm currently kicking off a background thread to do some REST queries in my app delegate's didFinishLaunchingWithOptions. This thread creates some objects and populates the model as the rest of the app continues to load (because I don't block, and didFinishLaunchingWithOptions returns YES). I also put up a loading UIViewController 'on top' of the main view that I tear down after the background initialization is complete. My problem is that I need to notify the first view (call it the Home view) that the model is ready, and that it should populate itself. The trick is that the background download could have finished before Home.viewDidAppear is called, or any of the other Home.initX methods. I'm having difficulty synchronizing all of this and I've thought about it long enough that it feels like I'm barking up the wrong tree. Are there any patterns here for this sort of thing? I'm sure other apps start by performing lengthy operations with loading screens :) Thanks!

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• Compiler reordering around mutex boundaries?

  - by shojtsy

  Suppose I have my own non-inline functions LockMutex and UnlockMutex, which are using some proper mutex - such as boost - inside. How will the compiler know not to reorder other operations with regard to calls to the LockMutex and UnlockMutex? It can not possibly know how will I implement these functions in some other compilation unit. void SomeClass::store(int i) { LockMutex(_m); _field = i; // could the compiler move this around? UnlockMutex(_m); } ps: One is supposed to use instances of classes for holding locks to guarantee unlocking. I have left this out to simplify the example.

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• jQuery way to handle select lists, radio buttons and checkboxes

  - by Álvaro G. Vicario

  When I handle HTML form elements with jQuery, I always end up with an ugly mix of jQuery syntax and plain JavaScript like, e.g.: function doStuff($combo){ if( $combo.get(0).options[$combo.get(0).selectedIndex].value=="" ){ var txt = ""; }else{ var txt = $combo.get(0).options[$combo.get(0).selectedIndex].text; } var $description = $combo.closest("div.item").find("input[name$=\[description\]]"); $description.val(txt); } Are there standard jQuery methods to handle typical operations on elements like <select>, <input type="radio"> and <input type="checkbox">? With typical, I mean stuff like reading the value of the selected radio button in a group or replacing elements in a selection list. I haven't found them in the documentation but I admit that method overloading can make doc browser kind of tricky.

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• Best Ruby ORM for Wrapping around Legacy MSSQL Database?

  - by Technocrat

  Hi. I found this answer and it sounds like almost exactly what I'm doing. I have heard mixed answers about whether or not datamapper can support mssql through dataobjects. Basically, we have an app that uses a consistently structured database, consistently named tables, etc in MSSQL. We're making all kinds of tools and stuff that have to interact with it, some of them remotely and so I decided that we need to create some common, simple access point to do read/write operations on the MSSQL app since it's API is all C# and other things I despise. Now my question is if anyone has any examples or projects they know of where a ruby ORM can essentially create models for another application's legacy database by defining the conventions of each model's pkeys, fkeys, table names, etc. Sequel is the only ORM I've used with MSSQL but never to do anything quite like this. Any suggestions?

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• How should I think about perspectives and rotation in OpenGL ES?

  - by Omega

  As I start to write rendering code, how do I want to consider my drawing operations? Will they always be relative to a fixed coordinate system on the screen, or does this change based on the camera perspective? The best example I can try to come up with is say I'm at (0,0,0) and I draw a line to (3,3,3). If I change the perspective +1 on the X axis and conduct the same operation, does it happen at (4,3,3), or am I just getting a new view of the line still being made at (3,3,3)? When doing rotation, am I moving the point from which a frustum emanates, or am I moving the rendering underneath?

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• Counting bits set in a .Net BitArray Class

  - by Sam

  I am implementing a library where I am extensively using the .Net BitArray class and need an equivalent to the Java BitSet.Cardinality() method, i.e. a method which returns the number of bits set. I was thinking of implementing it as an extension method for the BitArray class. The trivial implementation is to iterate and count the bits set (like below), but I wanted a faster implementation as I would be performing thousands of set operations and counting the answer. Is there a faster way than the example below? count = 0; for (int i = 0; i < mybitarray.Length; i++) { if (mybitarray [i]) count++; }

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• Why is forwarding variadic parameters invalid?

  - by awesomeyi

  Consider the variadic function parameter: func foo(bar:Int...) -> () { } Here foo can accept multiple arguments, eg foo(5,4). I am curious about the type of Int... and its supported operations. For example, why is this invalid? func foo2(bar2:Int...) -> () { foo(bar2); } Gives a error: Could not find an overload for '_conversion' that accepts the supplied arguments Why is forwarding variadic parameters invalid? What is the "conversion" the compiler is complaining about?

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• Linq-to-SQL and Performance.

  - by jalpesh

  HI, I am developing asp.net mvc site with linq-to-sql we are having 1000 cocurrent users and we are having performance problems. I have found that stackovewflow is also build on linq-to-sql? So can anybody know how they improved performance. Without line performance was good each page are loaded in 3 seconds but after migrating to linq as per our client requirement page comes in 8 to 10 seconds which is not acceptable performance. Our HTML is very clear but we are having very complex database operations. Any tip or code will be best answer. Thanks in advance,

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• bitfield mask calculation macro

  - by Aidan Cully

  We have a set of C macros, here, for using the preprocessor to do bitfield operations, and we run into warnings when attempting to use these macros in visual studio. The problem can be demonstrated very easily: #define BITFIELD_WIDTHMASK(Width) \ ((Width) >= 32 ? ~0x0ul : (1ul << (Width)) - 1) unsigned long foo(void) { return BITFIELD_WIDTHMASK(32); } Compiling this with MSVC yields the warning: test.c(12) : warning C4293: '<<' : shift count negative or too big, undefined behavior This isn't a behavior problem - the << operator won't be used in this case, and that should be detected at compile time. But does anyone have any suggestions about how to rewrite the macro to avoid the warning? Or, failing that, how to redesign the macro interface for this? Thanks in advance

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• For improving the join of two wave files

  - by kaki

  i want to get the values of the last 30 frames of the first wav file and first thirty frames of the second wave file in integer format and stored in a list or array. i have written the code for joining but during this manupalation i am getting in byte format and tried to convert it to integer but couldn't. as told before i want to get the frame detail of 1st 30 and last 30 in integer format,and by performing other operations join can be more successful looking for your help in this,please... thanking you, import wave m=['C:/begpython/S0001_0002.wav', 'C:/begpython/S0001_0001.wav'] i=1 a=m[i] infiles = [a] outfile = "C:/begpython/S0001_00367.wav" data= [] data1=[] for infile in infiles: w = wave.open(infile, 'rb') data1=[w.getnframes] #print w.readframes(100) data.append( [w.getparams(), w.readframes(w.getnframes())] ) #print w.readframes(1) #data1 = [ord(character) for character in data1] #print data1 #data1 = ''.join(chr(character) for character in data1) w.close() print data output = wave.open(outfile, 'wb') output.setparams(data[0][0]) output.writeframes(data[0][1]) output.writeframes(data[1][1]) output.writeframes(data[2][1]) output.close()

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• Do mini-filter functions need APCs enabled?

  - by botismarius

  Hello, Many Zw* functions that work with files (such as ZwCreateFile) need to be called at PASSIVE_LEVEL with APCs enabled: http://msdn.microsoft.com/en-us/library/ff566424%28VS.85%29.aspx. This is because, internally, I/O operations are asynchronously and the completion of an operation is delivered through an APC (correct me if I'm wrong). However, the documentation for similar functions from a mini-filter (such as FltCreateFile, FltReadFile, etc) does not specify that APCs should be enabled. Is it safe to call FltCreateFile/FltReadFile with APCs disabled? Thanks!

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• Measure CPU performance via JS

  - by Nicholas Kyriakides

  A webapp has as a central component a relatively heavy algorithm that handles geometric operations. There are 2 solutions to make the whole thing accessible from both high-end machines and relatively slower mobile devices. I will use RPC's if i detect that the user machine is ''slow'' or else if i detect that the user machine can handle it OK, then i provide to the webapp the script to handle it client side. Now what would be a reliable way to detect the speed of the user machine? I was thinking of providing a sample script as a test when the page loads and detect the time it took to execute that. Any ideas?

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• How to use SQL trigger to record the affected column's row number

  - by Freeman

  I want to have an 'updateinfo' table in order to record every update/insert/delete operations on another table. In oracle I've written this: CREATE TABLE updateinfo ( rnumber NUMBER(10), tablename VARCHAR2(100 BYTE), action VARCHAR2(100 BYTE), UPDATE_DATE date ) DROP TRIGGER TRI_TABLE; CREATE OR REPLACE TRIGGER TRI_TABLE AFTER DELETE OR INSERT OR UPDATE ON demo REFERENCING NEW AS NEW OLD AS OLD FOR EACH ROW BEGIN if inserting then insert into updateinfo(rnumber,tablename,action,update_date ) values(rownum,'demo', 'insert',sysdate); elsif updating then insert into updateinfo(rnumber,tablename,action,update_date ) values(rownum,'demo', 'update',sysdate); elsif deleting then insert into updateinfo(rnumber,tablename,action,update_date ) values(rownum,'demo', 'delete',sysdate); end if; -- EXCEPTION -- WHEN OTHERS THEN -- Consider logging the error and then re-raise -- RAISE; END TRI_TABLE; but when checking updateinfo, all rnumber column is zero. is there anyway to retrieve the correct row number?

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• Hibernate Hql find result size for paginator

  - by KCore

  Hi, I need to add paginator for my Hibernate application. I applied it to some of my database operations which I perform using Criteria by setting Projection.count().This is working fine. But when I use hql to query, I can't seem to get and efficient method to get the result count. If I do query.list().size() it takes lot of time and I think hibernate does load all the objects in memory. Can anyone please suggest an efficient method to retrieve the result count when using hql?

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• write cache and write sequence order

  - by excanoe

  ok, here i have some weird question: let say we have some binary file (.log), and sequence of write operations, for example log1, log2, log3 and each has some block size n (raw data). question: can I be sure that log1,log2 and log3 sequences can be written in the correct order in ONE file, even if i have few cache levels (disk hardware and os level)? update very interested in what will be with records order (not with records) if we have software or hardware failure (reboot or another reason). update there can be some percent of write failures, but main question is: will write order stay correct?

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• Controlling read and write access width to memory mapped registers in C

  - by srking

  I'm using and x86 based core to manipulate a 32-bit memory mapped register. My hardware behaves correctly only if the CPU generates 32-bit wide reads and writes to this register. The register is aligned on a 32-bit address and is not addressable at byte granularity. What can I do to guarantee that my C (or C99) compiler will only generate full 32-bit wide reads and writes in all cases? For example, if I do a read-modify-write operation like this: volatile uint32_t* p_reg = 0xCAFE0000; *p_reg |= 0x01; I don't want the compiler to get smart about the fact that only the bottom byte changes and generate 8-bit wide read/writes. Since the machine code is often more dense for 8-bit operations on x86, I'm afraid of unwanted optimizations. Disabling optimizations in general is not an option.

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• Understanding c-pointers for rows in 2-dimensional array

  - by utdiscant

  I have the following code: int main() { int n = 3, m = 4, a[n][m], i, j, (* p)[m] = a; for (i = 0; i < n; i++) for (j = 0; j < m; j++) a[i][j] = 1; p++; (*p)[2] = 9; return 0; } I have a hard time understanding what p is here, and the consequences of the operations on p in the end. Can someone give me a brief explanation of what happens. I know c-pointers in their simple settings, but here it get slightly more complicated.

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• What is a simple C library for a set of integer sets?

  - by conradlee

  I've got to modify a C program and I need to include a set of unsigned integer sets. That is, I have millions of sets of integers (each of these integer sets contains between 3 and 100 integers), and I need to store these in some structure, lets call it the directory, that can in logarithmic time tell me whether a given integer set already exists in the directory. The only operations that need to be defined on the directory is lookup and insert. This would be easy in languages with built-in support for useful data structures, but I'm a foreigner to C and looking around on Google did (surprisingly) not answer my question satisfactorily. This project looks about right: http://uthash.sourceforge.net/ but I would need to come up with my own hash key generator. This is a standard, simple problem, so I hope there is a standard and simple solution.

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• Hibernate Unit tests - Reset schema

  - by Marco

  Hi, I'm testing the CRUD operations of my DAOs in JUnit tests. When i execute the single test, Hibernate always resets the schema and populates the DB in a known state. But when i execute multiple tests in a row, Hibernate resets the schema once, and then the data is accumulated during the execution of the tests. This is an unexpected behavior, so I'd like to add in the @Before method of the tests a function that explicitly resets the schema to avoid the pesistence of side data created by previous tests during the execution chain. Any tips? Thanks

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• boost.asio's socket's recieve/send functions are bad?

  - by the_drow

  Data may be read from or written to a connected TCP socket using the receive(), async_receive(), send() or async_send() member functions. However, as these could result in short writes or reads, an application will typically use the following operations instead: read(), async_read(), write() and async_write(). I don't really understand that remark as read(), async_read(), write() and async_write() can also end up in short writes or reads, right? Why are those functions not the same? Should I use them at all? Can someone clarify that remark for me?

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• Is it possible to compute the minimum of three numbers by using two comparisons at the same time?

  - by Milo Hou

  I've been trying to think up of some way that I could do two comparisons at the same time to find the greatest/least of three numbers. Arithmetic operations on them are considered "free" in this case. That is to say, the classical way of finding the greater of two, and then comparing it to the third number isn't valid in this case because one comparison depends on the result of the other. Is it possible to use two comparisons where this isn't the case? I was thinking maybe comparing the differences of the numbers somehow or their products or something, but came up with nothing. Just to reemphasize, two comparisons are still done, just that neither comparison relies on the result of the other comparison. EDIT: what about: boolA = A^2 + B^2 < C^2 boolB = A > B if boolA then max=C else if boolB then max=A else max=B

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• cleartool question

  - by chuanose

  Lets say I have a directory at \testfolder, and the latest is currently at /main/10. I know that the operation resulting in testfolder@@/main/6 is to remove a file named test.txt. What's a sequence of cleartool operations that can be done in a script that will take "testfolder@@/main/6" and "test.txt" as input, and will cat out the contents of test.txt as of that time? One way I can think of is to get the time of /main/6 operation, create a view with config spec -time set to that time, and then cat the test.txt at the directory. But I'm wondering if I can do this in a easier way that doesn't involve manipulating config specs, perhaps through "cleartool find" and extended path names

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• Even lighter than SQLite

  - by Richard Fabian

  I've been looking for a C++ SQL library implementation that is simple to hook in like SQLite, but faster and smaller. My projects are in games development and there's definitely a cutoff point between needing to pass the ACID test and wanting some extreme performance. I'm willing to move away from SQL string style queries, allowing it to be code driven, but I haven't found anything out there that provides SQL like flexibility while also preferring performance over the ACID test. I don't want to go reinventing the wheel, and the idea of implementing an SQL library on my own is quite daunting, even if it's only going to be simple subset of all the calls you could make. I need the basic commands (SELECT, MODIFY, DELETE, INSERT, with JOIN, and WHERE), not data operations (like sorting, min, max, count) and don't need the database to be atomic, or even enforce consistency (I can use a real SQL service while I'm testing and debugging).

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