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• Applying transformations to NSBitmapImageRep

  - by Adam

  So ... I have an image loaded into an NSBitmapImageRep object, so I am able to examine the contents of specific pixels via a two dimensional array. Now I want to apply a couple of "transformations" to the image, in preparation for some additional processing. If I was manipulating the image manually, in Photoshop, I would: Rotate the image Crop a portion of it and discard the rest Apply a "threshold" transformation (which essentially converts the image to black and white, based on the threshold value I provide) Resample the image to shrink it down a bit (which, although losing some image quality, will speed up the subsequent processing) (not necessarily in that order) Are there objective C methods available to facilitate these specific image manipulations, with the data in the NSBitmapImageRep object? If so, can someone point me to some good examples?

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• What is the logic behind defining macros inside a struct?

  - by systemsfault

  As apparent in the title, I'm questioning the reason behind defining the macros inside a struct. I frequently see this approach in network programming for instance following snippet: struct sniff_tcp { u_short th_sport; /* source port */ u_short th_dport; /* destination port */ tcp_seq th_seq; /* sequence number */ tcp_seq th_ack; /* acknowledgement number */ u_char th_offx2; /* data offset, rsvd */ #define TH_OFF(th) (((th)->th_offx2 & 0xf0) >> 4) u_char th_flags; #define TH_FIN 0x01 #define TH_SYN 0x02 #define TH_RST 0x04 #define TH_PUSH 0x08 #define TH_ACK 0x10 #define TH_URG 0x20 #define TH_ECE 0x40 #define TH_CWR 0x80 #define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG|TH_ECE|TH_CWR) u_short th_win; /* window */ u_short th_sum; /* checksum */ u_short th_urp; /* urgent pointer */ }; This example is from sniffex.c code in tcpdump's web site. Is this for enhancing readability and making code clearer.

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• What is the best way to expose a callback API - C++

  - by rursw1

  Hi, I have a C++ library that should expose some system\ resource calls as callbacks from the linked application. For example: the interfacing application (which uses this library) can send socket management callback functions - send, receive, open, close etc., and the library will use this implementation in stead of the library's implementation. (This way enables the application to manage the sockets by itself, can be useful). This library has to expose also more callbacks, like, for example, a password validation, so I wonder if there is a preferred method to expose the callback sending option in one API. Something like: int AddCallbackFunc (int functionCallbackType, <generic function prototype>, <generic way to pass some additional arguments>) Then within my library I will assign the callback to the appropriate function pointer according to the functionCallbackType parameter. Is there any way to implement it in a generic way which will fit ANY function prototype and ANY additional arguments? Your help will be more than appreciated... Thanks!

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• MS DOS function like ipconfig to get system performance specs?

  - by JustADude

  I am aware of MSINFO32, but I'm wondering if there is a MS DOS command similar to ipconfig in order to get system specifications? I would like for the system specifications to be displayed in the MS DOS prompt. I would like to see at least: CPU RAM BUS speed Thanks for any insights. Edit: I am unable to install any other software, so just have to use existing DOS programming commands to extract this information. Thank you again. 2nd Edit: Whoops. Using Windows XP and Windows Vista.

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• Getting mediafire directlink without using WebBrowser .NET control ?

  - by NVA

  I'm looking for the way to get the direct link from mediafire. By default, when a user visits a download link, he will be presented with a download page where he has to wait for the download to be processed and then a link will appear. I googled and found a VB.NET 2008 solution to this using WebBrowser WB http://www.vbforums.com/showthread.php?t=556681 It works pretty well but I'm tired of pop-up windows and the loading speed. So, I wonder if there is a solution to this problem? (a non WB solution ^^) Any help is greatly appreciated.

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• Simple C++ container class that is thread-safe for writing

  - by conradlee

  I am writing a multi-threaded program using OpenMP in C++. At one point my program forks into many threads, each of which need to add "jobs" to some container that keeps track of all added jobs. Each job can just be a pointer to some object. Basically, I just need the add pointers to some container from several threads at the same time. Is there a simple solution that performs well? After some googling, I found that STL containers are not thread-safe. Some stackoverflow threads address this question, but none that forms a consensus on a simple solution.

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• Store data in Ruby on Rails without Database

  - by snowmaninthesun

  I have a few data values that I need to store on my rails app and wanted to know if there are any alternatives to creating a database table just to do this simple task. Background: I'm writing some analytics and dashboard tools for my ruby on rails app and i'm hoping to speed up the dashboard by caching results that will never change. Right now I pull all users for the last 30 days, and re arange them so I can see the number of new users per day. It works great but takes quite a long time, in reality I should only need to calculate the most recent day and just store the rest of the array somewhere else. Where is the best way to store this array? Creating a database table seems a bit overkill, and i'm not sure that global variables are the correct answer. Is there a best practice for persisting data like this? If anyone has done anything like this before let me know what you did and how it turned out.

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• Looking at the C++ new[] cookie. How portable is this code?

  - by carleeto

  I came up with this as a quick solution to a debugging problem - I have the pointer variable and its type, I know it points to an array of objects allocated on the heap, but I don't know how many. So I wrote this function to look at the cookie that stores the number of bytes when memory is allocated on the heap. template< typename T > int num_allocated_items( T *p ) { return *((int*)p-4)/sizeof(T); } //test #include <iostream> int main( int argc, char *argv[] ) { using std::cout; using std::endl; typedef long double testtype; testtype *p = new testtype[ 45 ]; //prints 45 std::cout<<"num allocated = "<<num_allocated_items<testtype>(p)<<std::endl; delete[] p; return 0; } I'd like to know just how portable this code is.

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• How would I go about implementing a stopwatch with different speeds?

  - by James

  Ideally I would like to have something similar to the Stopwatch class but with an extra property called Speed which would determine how quickly the timer changes minutes. I am not quite sure how I would go about implementing this. Edit Since people don't quite seem to understand why I want to do this. Consider playing a soccer game, or any sport game. The halfs are measured in minutes, but the time-frame in which the game is played is significantly lower i.e. a 45 minute half is played in about 2.5 minutes.

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• Swap byte 2 and 4 from integer

  - by czar x

  I had this interview question - Swap byte 2 and byte4 within an integer sequence. Integer is a 4byte wide i.e. 32 bits My approach was to use char *pointer and a temp char to swap the bytes. For clarity i have broken the steps otherwise an character array can be considered. unsigned char *b2, *b4, tmpc; int n = 0xABCD; b2 = &n; b2++; b4 = &n; b4 +=3; ///swap the values; tmpc = *b2; *b2 = *b4; *b4 = tmpc; Any other methods?

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• Event handling C# / Registering a callback

  - by Jeff Dahmer

  Events can only return void and recieve object sender/eventargs right? If so then craptastic.... how can I pass a function pointer to another obj, like: public bool ACallBackFunc(int n) { return n > 0; } public void RegisterCallback(Something s) { s.GiveCallBack(this.ACallBackFunc); } Something::GiveCallBack(Action? funcPtr) I tried using Action, but I need it to return some value and Actions can only return void. Also, we do not know what kind of a callback we will be recieving; it could return anything and have any params! Reflection will have to be used somehow I reckon.

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• Access static constant variable from multiple threads in C

  - by user325519

  I have some experience with multithread programming under Linux (C/C++ & POSIX threads), however most obvious cases are sometimes very complicated. I have several static constant variables (global and function local) in my code, can I access them simultaneously from multiple threads without using mutexes? Because I don't modify them it should be ok, but it's always better to ask. I have to do heavy speed optimization, so even as fast operations as mutex lock/unlock are quite expensive for me, especially because my application is going to access these variables form long loops.

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• C++ inheritance question

  - by user233973

  Hi guys, I have a C++ inheritance related question. I have a set of classes like this (I have not given the complete class structure coz I am lazy :) ). I want to access chiComponent class public methods using com pointer. How should I go about it? Note that I am having to change the object which "com" is pointing to in a lot of places. So I do not think I can have another chiComponent *ccom = <some_cast> com; ccom.chiComponentMethod() How should I go about it? class Component{ }; class chiComponent : public Component { public: void chiComponentMethod() { cout << "Hi! Chi component function called!!"; } } class parent { protected: Component *com; }; class child : public parent{ public: child() { com = new chiComponent(); } } Regards Arun

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• std::out_of_range error?

  - by vette982

  I'm dealing with a file with a linked list of lines with each node looking like this: struct TextLine{ //The actual text string text; //The line number of the document int line_num; //A pointer to the next line TextLine * next; }; and I'm writing a function that adds spaces at the beginning of the lines found in the variable text, by calling functions like linelist_ptr->text.insert(0,1,'\t'); The program compiles, but when I run it I get this error: terminate called after throwing an instance of 'std::out_of_range' what(): basic_string::at Aborted Any ideas?

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• Is JPA + EJB to much slow (or heavy) for over Internet transactions?

  - by Xavier Callejas

  Hi, I am developing a stand-alone java client application that connects to a Glassfish v3 application for JPA/EJB facade style transactions. In other words, my client application do not connect directly to the database to CRUD, but it transfers JPA objets using EJB stateless sessions. I have scenarios where this client application will be used in an external network connected with a VPN over Internet with a client connection of 512kbp/DSL, and a simple query takes so much time, I'm seeing the traffic graph and when I merge a entity in the client application I see megabytes of traffic (I couldn't believe how a purchase order entity could weight more than 1 mb). I have LAZY fetch in almost every many-to-many relationship, but I have a lot of many-to-one relationships between entities (but this is the great advantage of JPA!). Could I do something to accelerate the the speed of transactions between JPA/EJB server and the remote java client? Thank you in advance.

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• The Wheel Invention - Beneficial For Learning?

  - by Sarfraz

  Hello, Chris Coyier of css-tricks.com has written a good article titled Regarding Wheel Invention. In a paragraph he says: On the “reinventing” side, you benefit from complete control and learning from the process. And on the very next line he says: On the other side, you benefit from speed, reliability, and familiarity. Also often at odds are time spent and cost. He is right in both statements I think. I really like his first statement. I do actually sometimes re-invent the wheel to learn more and gain complete control over what I am inventing. I wonder why people are so much against that or rather biased. Isn't there the benefit of learning and getting complete control or probably some other benefits too. I would love to see what you have to say about this.

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• Using a single PHP script for an entire site

  - by briggins5

  I had an idea today (that millions of others have probably already had) of putting all the sites script into a single file, instead of having multiple, seperate ones. When submitting a form, there would also be a hidden field called something like 'action' which would represent which function in the file would handle it. I know that things like Code Igniter and CakePHP exist which help seperate/organise the code. Is this a good or bad idea in terms of security, speed and maintenance? Do things like this already exist that i am not aware of?

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• memset on array of structures in C++

  - by garry

  I have another memset question. It appears as if the code I am editing may have some issues (or it's not done the same way in different files) A::LRM las[9]; //A and LRM are both structures with BOOLS and INTS memset(&las, 0, sizeof(las)); typedef Sec SecArray[16]; SecArray rad_array; memset(rad_array, 0, sizeof(SecArray)); The second example appears to be correct because rad_array is the same as the first position in the array. Then the sizeof(SecArray)) would make sense. The first one doesn't seem correct to me. All structs are just BOOLs and INTS nothing dynamic in them. My understanding from my other post about memset was that it followed this format. memset("pointer to object", "what to set it to", "size of object") Can anyone tell me what exactly is going on here if I am incorrect with my theory.

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• C++ iterators & loop optimization

  - by Quantum7

  I see a lot of c++ code that looks like this: for( const_iterator it = list.begin(), const_iterator ite = list.end(); it != ite; ++it) As opposed to the more concise version: for( const_iterator it = list.begin(); it != list.end(); ++it) Will there be any difference in speed between these two conventions? Naively the first will be slightly faster since list.end() is only called once. But since the iterator is const, it seems like the compiler will pull this test out of the loop, generating equivalent assembly for both.

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• Memory leak in chrome.extension.sendRequest()

  - by jprim

  Chrome Version : 9.0.597.19 (Build 68937) beta & current stable I have simplified my code as far as possible. I ended up with the attached extension: content.js (content script run on every site): setInterval(function() { chrome.extension.sendRequest({ }, function(response) { //Do nothing }); }, 1); background.js (background page script): chrome.extension.onRequest.addListener(function(request, sender, sendResponse) { sendResponse({ }); }); When you install this extension, you can observe it eating up memory extremely fast (I got 90MB in 1 min with 9 tabs opened). You can speed up the process by opening more tabs. Of course, the extension I am actually developing does not send requests every millisecond, but only every 3 seconds. This just slows it down, though. A user who has run it in the background for a long time with many tabs opened has reported 100MB of memory usage, and I can reproduce it to a less extreme extent, too.

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• How to get "printer ready bytes" from a source in c#?

  - by luis_villase

  Hey everyone! I'm in a bit of trouble here, hoping you can help a fellow programmer out. I have an application that receives a pointer to raw bytes (plus length and stuff) and sends said raw data to a printer. This is important, I have no choice but to use this method to get any printing done. If I send a raw string, it will print with no problem. However, I need to be able to print formatted text, images, etc. So the thing is... I would like to be able to get printer ready bytes from a given source (maybe a pdf, or html, does not matter as long as it contains formatted text and/or images). It would be like "splitting" the print command like so: a) Open file and read data b) Load printer data into memory c) Send bytes to printer Obviously, I've got a) and c) covered, it's b) the one that's breaking my head. Any thoughts? Thanks in advance for your help.

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• const ready only local copies

  - by robUK

  Hello gcc 4.4.4 c89 I am just wondering is it worth passing a const into a function. i.e. void do_something(const char *dest, const int size) The size is a ready-only so I don't want to change it. However, some developers never have this as const has it is a local copy that is being used. The pointer is const as you can change the value in the calling routine. I always have a const on ready-only local copies, as it confirms to anyone reading my code that it is a ready-only variable. And also, when coding I don't make the mistake of changing it without realizing. Many thanks for any suggestions,

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• Why do virtual memory addresses for linux binaries start at 0x8048000?

  - by muteW

  Disassembling an ELF binary on a Ubuntu x86 system I couldn't help but notice that the code(.text) section starts from the virtual address 0x8048000 and all lower memory addresses seem to be unused. This seems to be rather wasteful and all Google turns up is either folklore involving STACK_TOP or protection against null-pointer dereferences. The latter case looks like it can be fixed by using a single page instead of leaving a 128MB gap. So my question is this - is there a definitive answer to why the layout has been fixed to these values or is it just an arbitrary choice?

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• Official definition of CSCI (Computer Software Configuration Item)

  - by Andreas_D

  I'm looking for the most official definition of CSCI / Configuration Item - not just what it is but what we have to deliver / can expect when a contract defines subsystems which shall be developed as configuration items. I spend some time with my famous search tool and found a lot of explanations for CSCI (wikipedia, acronym directories, ...) but I haven't found a standard or a pointer to a standard (like ISO-xxx) yet which tells (1) what it is and (2) what has to be done from a QM/CM point of view. I just ask, because a contractors QM representative stated during an acceptance test, that CI only requires to not forget the CI in the configuration plan and to assign a serial number ... I expected to see some SRS, SDD, ICD, SVD, SIP, ... documents and acceptance test documentation for those subsystems...

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• SQL Server, fetching data from multiple joined tables. Why is slow?

  - by user562192

  I have problem with performance when retrieving data from SQL Server. My sql query looks something like this: SELECT table_1.id, table_1.value, table_2.id, table_2.value,..., table_20.id, table_20.value From table_1 INNER JOIN table_2 ON table_1.id = table_2.table_1_id INNER JOIN table_3 ON table_2.id = table_3.table_2_id... WHERE table_1.row_number BETWEEN 1 AND 20 So, I am fetching 20 results. This query takes about 5 seconds to execute. When I select only table_1.id, it returns results instantly. Because of that, I guess that problem is not in JOINs, it is in retrieving data from multiple tables. Any suggestions how I would speed up this query?

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