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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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• 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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• delete,copy,rename files and directories in WINAPI ..?

  - by Kristian

  hi I made a code that search in a givin path for a certain file name or folder and print the value BUT now how can i modify it to instead of printing its name perform on of the operations ( delete,copy,rename ) I searched on google and found nothin. #include "stdafx.h" #include <windows.h> int _tmain(int argc, _TCHAR* argv[]) { TCHAR *fn; fn=L"d:\\*"; HANDLE f; WIN32_FIND_DATA data; f=FindFirstFile(fn,&data); if(f==INVALID_HANDLE_VALUE){ printf("not found\n"); return 0; } else{ _tprintf(L"found this file: %s\n",data.cFileName); } while(FindNextFile(f,&data)){ { _tprintf(L"found this file: %s\n",data.cFileName); } } } FindClose(f); return 0; }

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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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• 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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• 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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• 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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• 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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• SQlite/Firebird: Does any of them support multiple concurrent write access ?

  - by Quandary

  Question: I currently store ASP.net application data in XML files. Now the problem is I have asynchronous operations, which means I ran into the problem of simultanous write access on a XML file... Now, I'm considering moving to an embedded database to solve the issue. I'm currently considering SQlite and embeddable Firebird. I'm not sure however if SQlite or Firebird can handle multiple concurrent write access. And I certainly don't want the same problem again. Anybody knows ? SQlite certainly is better known, but which one is better - SQlite or Firebird ? I tend to say Firebird, but I don't really know. No MS-Access or MS-SQL-express recommodations please, I'm a sane person.

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• Connect Android application to remote data

  - by tadywankenobi

  Sheesh talk about limited information! I'm trying to get my Android application to connect to an online database to access information. There's quite a bit of info including geotags and these are going to be mapped on my app. The developer site has the very informative piece of information: You can use the network (when it's available) to store and retrieve data on your own web-based services. To do network operations, use classes in the following packages: java.net.* android.net.* Like I said in my previous question, I'm still very much an android newbie, and trying to remember my java oop from college is slow. Does anyone have an example of how this might work, or how I could implement it? I wouldn't mind even connecting to a local xml file, if I could find a good example of how to do that!? Am I just looking in all the wrong places?! Help. Please! T

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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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• 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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• 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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• The ** idiom in C++ for object construction

  - by bobobobo

  In a lot of C++ API'S (COM-based ones spring to mind) that make something for you, the pointer to the object that is constructed is usually required as a ** pointer (and the function will construct and init it for you) You usually see signatures like: HRESULT createAnObject( int howbig, Object **objectYouWantMeToInitialize ) ; -- but you seldom see the new object being passed as a return value. Besides people wanting to see error codes, what is the reason for this? Is it better to use the ** pattern rather than a returned pointer for simpler operations such as: wchar_t* getUnicode( const char* src ) ; Or would this better be written as: void getUnicode( const char* src, wchar_t** dst ) ; The most important thing I can think of is to remember to free it, and the ** way, for some reason, tends to remind me that I have to deallocate it as well.

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• how to protect an imported win32 dll into a .net application from memory issues

  - by Eric

  I have a c# application that needs to use a legacy win32 dll. The dll is almost its own app, it has dialogs, operations with hardware, etc. When this dll is imported and used, there are a couple of problems that occur: Dragging a dialog (not a windows system dialog, but one created by the dll) across the managed code app causes the UI to not repaint. Further it generates a system out of memory exception from various ui controls. The performance is incredibly slow. There seems to be no way to unload the dll so the memory never gets cleaned up. When we close our managed app, we get another memory exception. At the moment we import each method call as such: [DllImport("dllname.dll", EntryPoint = "MethodName", SetLastError = true, CharSet = CharSet.Auto, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]

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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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• 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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• Strange behaviour of Android debugger in Eclipse when using Camera for preview.

  - by Buzzy

  Hi, I have an Android application that uses a SurfaceView subclass and Camera object to preview images before capture. Once I capture an image, I stop the preview and release the camera. Execution stops at any breakpoint after this. However, apart from the "Suspend" and "Terminate" icons, the rest are disabled. This is strange because the "Debug Current Instruction Pointer" is clearly at the said breakpoint and execution is already suspended. I can't perform any debugging operations and have no option but to terminate the session. Sometimes (very rarely), the session terminates by itself. I can confirm that this odd behavior takes place only after I preview the camera capture. I am fairly new to Android development. Is there some obvious mistake I am making? Any help would be highly appreciated.

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• Apache and Rewrite Module

  - by Yvon Blais

  I created a file .htaccess in the /var/www directory., The rights are root root --wxrwxrwxr The content of the file is : Options +FollowSymlinks RewriteEngine on RewriteLogLevel 3 RewriteLog "/var/log/apache2/rewrite.log" RewriteRule ^(.*?)$ testphp.php When I call the page phpinfo.php, I've got: Loaded Modules ... mod_rewrite ... Therefore, the modules is loaded Afer each modification,I restared the server manually with sudo /etc/init.d/apache2 restart The error.log gives Apache/2.2.14 (Ubuntu) PHP/5.3.2-1ubuntu4.2 with Suhosin-Patch configured -- resuming normal operations When I call a page anyone.htm or anyone.php, the rewrite.log does contain nothing and the real page is called. If I understand, the page anyone.php should be replaced by testphp.php Did I make siomething wrong ? Thanks

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• Using generics in dotnet for functions with any number of arguments?

  - by Zarigani

  I would like to have a function that can "wrap" any other function call. In this particular case, it would allow me to write some more generic transaction handling around some specific operations. I can write this for any particular number of arguments, e.g. for one argument: Public Shared Sub WrapFunc(Of T)(ByVal f As Action(Of T), ByVal arg As T) ' Test some stuff, start transaction f(arg) ' Test some stuff, end transaction End Sub ... but I was hoping to have this handle any number of arguments without having to have duplicate code for 0 args, 1 arg, 2 args, etc. Is there a way of doing this?

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• JavaScript pack("d") - binary strings

  - by Tim Whitlock

  I'm trying to replicate the Perl and PHP style pack and unpack functions in JavaScript. Unsigned integers were easy enough, so my pack('n') and pack('N') are ok. But my lack of a computer science background is a hurdle now and I don't know where to start with pack('d') for packing JavaScript's standard floating point. Is there a JavaScript library for this out there? If not, is there a good resource where I can learn how to do this? I am fine with bitwise and binary level operations in JS, I just don't know where to start with the logic. Thanks.

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• PHP: Simulate multiple MySQL connections to same database

  - by Varun

  An insert query is constantly getting logged in my MySQL slow query log. I want to see how much time the INSERT query is taking with 100 simultaneous insert operations(to the same table). So I need to simulate the follwoing. 500 different simultaneous connections from PHP to the same database on a mysql server, all of which are inserting a row(simultaneously) to the same table. DO I need to use any load testing tool? Or Can I simply write a PHP script to do this? Any thoughts?

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• Representing a very large array of bits in little memory

  - by user614624

  Hello, I would like to represent a structure containing 250 M states(1 bit each) somehow into as less memory as possible (100 k maximum). The operations on it are set/get. I cold not say that it's dense or sparse, it may vary. The language I want to use is C. I looked at other threads here to find something suitable also. A probabilistic structure like Bloom filter for example would not fit because of the possible false answers. Any suggestions please?

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• Identify a non-computer network device?

  - by Avilan

  I'm current working on a program that scans my network and discoveres computers and devices on the network. I use various operations to find data on the devices I discover, but want to distinguish the network devices from computers. And I'm wondering if anyone knows how I could do this? I looked a bit at SNMP, and tried connecting to my network printer, router and modem. But I seem to only be able to connect to the printer, neither the router or modem responds. Is there another way to identify what kind of a device an IP address belongs to?

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• How to optimize indexing of large number of DB records using Zend_Lucene and Zend_Paginator

  - by jdichev

  So I have this cron script that is deployed and ran using Cron on a host and indexes all the records in a database table - the index is later used both for the front end of the site and the backed operations as well. After the operation, the index is about 3-4 MB. The problem is it takes a lot of resources (CPU: 30+ and a good chunk of memory) and slows the machine down. My question is about how to optimize the operation described below: First there is a select query built using the Zend Framework API, this query is then passed to a Paginator factory that returns a paginator which I am using to balance the current number of items being indexed and not iterate over too much items. The script is iterating over the current items in the paginator object using a foreach loop until reaching the end and then it starts from the beginning after getting items for the next page. I am suspecting this overhead is caused by the Zend_Lucene but no idea how this could be improved.

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