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• Boost shared_ptr use_count function

  - by photo_tom

  My application problem is the following - I have a large structure foo. Because these are large and for memory management reasons, we do not wish to delete them when processing on the data is complete. We are storing them in std::vector<boost::shared_ptr<foo>>. My question is related to knowing when all processing is complete. First decision is that we do not want any of the other application code to mark a complete flag in the structure because there are multiple execution paths in the program and we cannot predict which one is the last. So in our implementation, once processing is complete, we delete all copies of boost::shared_ptr<foo>> except for the one in the vector. This will drop the reference counter in the shared_ptr to 1. Is it practical to use shared_ptr.use_count() to see if it is equal to 1 to know when all other parts of my app are done with the data. One additional reason I'm asking the question is that the boost documentation on the shared pointer shared_ptr recommends not using "use_count" for production code.

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• What does the destructor do silently?

  - by zhanwu

  Considering the following code which looks like that the destructor doesn't do any real job, valgrind showed me clearly that it has memory leak without using the destructor. Any body can explain me what does the destructor do in this case? #include <iostream> using namespace std; class A { private: int value; A* follower; public: A(int); ~A(); void insert(int); }; A::A(int n) { value = n; follower = NULL; } A::~A() { if (follower != NULL) delete follower; cout << "do nothing!" << endl; } void A::insert(int n) { if (this->follower == NULL) { A* f = new A(n); this->follower = f; } else this->follower->insert(n); } int main(int argc, char* argv[]) { A* objectA = new A(1); int i; for (i = 0; i < 10; i++) objectA->insert(i); delete objectA; }

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• Creation of model in core data on the fly

  - by user1740045

  How can we create a model in core data on the fly? I.e getting the schema of database from somewhere and then creating a Core Data Object graph? *QuesTion:* Yes thats fine, agreed with all the advantages. But, can anybody can tell practically, what is the benefit of integrating Core Data into project instead of using SQL directly. 1.No need to write SQL boiler plate code [but need to learn Core Data Model (steep curve)] 2.WE can undo and redo changes [but practically who needs it] 3.we can migrate to another schema [that can be done by SQLite as well jus need to add another field into table] 4.For say aggregation on some field in table,in Core Data we need to loop through Core Data Objects whereas in SQLite we need to first write SQLite Boiler Plate Code and then the basic aggregation SQL query,which is easy to write,only length of code will increase...But in case of Core Data (need to learn a lot). So apart from reducing the length of Code,does it actually adds value to project? or in terms of Memory Efficiency,Performance,etc.. PS: If anybody has actualy worked on Core Data(Model Creation On the Fly) , if possible share and gve pointers..thanks!

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• How to optimize my game calendar in C#?

  - by MartyIX

  Hi, I've implemented a simple calendar (message system) for my game which consists from: 1) List<Event> calendar; 2) public class Event { /// <summary> /// When to process the event /// </summary> public Int64 when; /// <summary> /// Which object should process the event /// </summary> public GameObject who; /// <summary> /// Type of event /// </summary> public EventType what; public int posX; public int posY; public int EventID; } 3) calendar.Add(new Event(...)) The problem with this code is that even thought the number of messages is not excessise per second. It allocates still new memory and GC will once need to take care of that. The garbage collection may lead to a slight lag in my game and therefore I'd like to optimalize my code. My considerations: To change Event class in a structure - but the structure is not entirely small and it takes some time to copy it wherever I need it. Reuse Event object somehow (add queue with used events and when new event is needed I'll just take from this queue). Does anybody has other idea how to solve the problem? Thanks for suggestions!

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• Call 32-bit or 64-bit program from bootloader

  - by user1002358

  There seems to be quite a lot of identical information on the Internet about writing the following 3 bootloaders: Infinite loop jmp $ Print a single character Print "Hello World". This is fantastic, and I've gone through these 3 variations with very little trouble. I'd like to write some 32- or 64-bit code in C and compile it, and call that code from the bootloader... basically a bootloader that, for example, sets the computer up to run some simple numerical simulation. I'll start by listing primes, for example, and then maybe some input/output from the user to maybe compute a Fourier transform. I don't know. I haven't found any information on how to do this, but I can already foresee some problems before I even begin. First of all, compiling a C program compiles it into one of several different files, depending on the target. For Windows, it's a PE file. For Linux, it's a .out file. These files are both quite different. In my instance, the target isn't Windows or Linux, it's just whatever I have written in the bootloader. Secondly, where would the actual code reside? The bootloader is exactly 512 bytes, but the program I write in C will certainly compile to something much larger. It will need to sit on my (virtual) hard disk, probably in some sort of file system (which I haven't even defined!) and I will need to load the information from this file into memory before I can even think about executing it. But from my understanding, all this is many, many orders of magnitude more complex than a 12-line "Hello World" bootloader. So my question is: How do I call a large 32- or 64-bit program (written in C/C++) from my 16-bit bootloader.

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• Create table class as a singleton

  - by Mark

  I got a class that I use as a table. This class got an array of 16 row classes. These row classes all have 6 double variables. The values of these rows are set once and never change. Would it be a good practice to make this table a singleton? The advantage is that it cost less memory, but the table will be called from multiple threads so I have to synchronize my code which way cause a bit slower application. However lookups in this table are probably a very small portion of the total code that is executed. EDIT: This is my code, are there better ways to do this or is this a good practice? Removed synchronized keyword according to recommendations in this question. final class HalfTimeTable { private HalfTimeRow[] table = new HalfTimeRow[16]; private static final HalfTimeTable instance = new HalfTimeTable(); private HalfTimeTable() { if (instance != null) { throw new IllegalStateException("Already instantiated"); } table[0] = new HalfTimeRow(4.0, 1.2599, 0.5050, 1.5, 1.7435, 0.1911); table[1] = new HalfTimeRow(8.0, 1.0000, 0.6514, 3.0, 1.3838, 0.4295); //etc } @Override @Deprecated public Object clone() throws CloneNotSupportedException { throw new CloneNotSupportedException(); } public static HalfTimeTable getInstance() { return instance; } public HalfTimeRow getRow(int rownumber) { return table[rownumber]; } }

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• HTML5 Local Storage of audio element source - is it possible?

  - by andrewdotcom

  Hi stackoverflow experts I've been experimenting with the audio and local storage features of html5 of late and have run into something that has me stumped. I'd like to be able to cache or store the source of the audio element locally to enable speedier and offline playback. The problem is I can't see how this is possible with the current implementation. I have tried the following using webkit: Creating a manifest file to set up local caching but the audio file appears not to be a cacheable item maybe due to the way it is stream or something I have also attempted to use javascript to put an audio object into local storage but the size of the mp3 makes this impossible due to memory issues (i think). I have tried to use the data uri and base64 to use the html as a audio transport that can be cached but again the filesize makes this prohibitive. Also the audio element does not seem to like this in webkit (works fine in mozilla) I have tried several methods of putting the data into the local database store. Again suffering the same issues as the other cases. I'd love to hear any other ideas anyone may have as to how I could achieve my goal of offline playback using caching/local storage in webkit.

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• How to get results efficiently out of an Octree/Quadtree?

  - by Reveazure

  I am working on a piece of 3D software that has sometimes has to perform intersections between massive numbers of curves (sometimes ~100,000). The most natural way to do this is to do an N^2 bounding box check, and then those curves whose bounding boxes overlap get intersected. I heard good things about octrees, so I decided to try implementing one to see if I would get improved performance. Here's my design: Each octree node is implemented as a class with a list of subnodes and an ordered list of object indices. When an object is being added, it's added to the lowest node that entirely contains the object, or some of that node's children if the object doesn't fill all of the children. Now, what I want to do is retrieve all objects that share a tree node with a given object. To do this, I traverse all tree nodes, and if they contain the given index, I add all of their other indices to an ordered list. This is efficient because the indices within each node are already ordered, so finding out if each index is already in the list is fast. However, the list ends up having to be resized, and this takes up most of the time in the algorithm. So what I need is some kind of tree-like data structure that will allow me to efficiently add ordered data, and also be efficient in memory. Any suggestions?

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• How can I synchronize one set of data with another?

  - by RenderIn

  I have an old database and a new database. The old records were converted to the new database recently. All our old applications continue to point to the old database, but the new applications point to the new database. Currently the old database is the only one being updated, so throughout the day the new database becomes out of sync. It is acceptable for the new database to be out of sync for a day, so until all our applications are pointed to the new database I just need to write a nightly cron job that will bring it up to date. I do not want to purge the new database and run the complete conversion script each night, as that would reduce uptime and would create a mess in our auditing of that table. I'm thinking about selecting all the data from the old database, converting it to the new database structure in memory, and then checking for the existence of each record before inserting it in the new database. After that's done, I'd select everything from the new database and check if it exists in the old one, and if not delete it. Is this the simplest way to do this?

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• Linking Error Building 64bit Qt app on 32bit XP machine.

  - by photo_tom

  I'm trying to build a 64 bit version of my application (and yes I really do need the memory) on my 32bit xp dev box for production testing on our Vista64 server. Previously, I have built w/o any errors the Qt 4.6.2 DLL's in 64 bit mode. That step went vary smooth. Just to get started in building production, I'm trying to rebuild Qt's Star Delegate demo in 64bit mode. I converted the 32bit to 64bit app by changing the application configuration and adjusting the library's to the 64bit venisons. Now, when I go to link, I'm getting the following error when I link 1>------ Build started: Project: stardelegate, Configuration: Release x64 ------ 1>Linking... 1>MSVCRT.lib(crtexew.obj) : error LNK2001: unresolved external symbol WinMain 1>release64\stardelegate.exe : fatal error LNK1120: 1 unresolved externals Suggestions? edit - After some more searching, discovered if I link as a console app it will work and run. But not as a windows app. And I don't have this problem in 32 bit mode.

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• How can I use io.StringIO() with the csv module?

  - by Tim Pietzcker

  I tried to backport a Python 3 program to 2.7, and I'm stuck with a strange problem: >>> import io >>> import csv >>> output = io.StringIO() >>> output.write("Hello!") # Fail: io.StringIO expects Unicode Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unicode argument expected, got 'str' >>> output.write(u"Hello!") # This works as expected. 6L >>> writer = csv.writer(output) # Now let's try this with the csv module: >>> csvdata = [u"Hello", u"Goodbye"] # Look ma, all Unicode! (?) >>> writer.writerow(csvdata) # Sadly, no. Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unicode argument expected, got 'str' According to the docs, io.StringIO() returns an in-memory stream for Unicode text. It works correctly when I try and feed it a Unicode string manually. Why does it fail in conjunction with the csv module, even if all the strings being written are Unicode strings? Where does the str come from that causes the Exception? (I do know that I can use StringIO.StringIO() instead, but I'm wondering what's wrong with io.StringIO() in this scenario)

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• why doesnt this program print?

  - by Alex

  What I'm trying to do is to print my two-dimensional array but i'm lost. The first function is running perfect, the problem is the second or maybe the way I'm passing it to the "Print" function. #include <stdio.h> #include <stdlib.h> #define ROW 2 #define COL 2 //Memory allocation and values input void func(int **arr) { int i, j; arr = (int**)calloc(ROW,sizeof(int*)); for(i=0; i < ROW; i++) arr[i] = (int*)calloc(COL,sizeof(int)); printf("Input: \n"); for(i=0; i<ROW; i++) for(j=0; j<COL; j++) scanf_s("%d", &arr[i][j]); } //This is where the problem begins or maybe it's in the main void print(int **arr) { int i, j; for(i=0; i<ROW; i++) { for(j=0; j<COL; j++) printf("%5d", arr[i][j]); printf("\n"); } } void main() { int *arr; func(&arr); print(&arr); //maybe I'm not passing the arr right ? }

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• Python : How do you find the CPU consumption for a piece of code?

  - by Yugal Jindle

  Background: I have a django application, it works and responds pretty well on low load, but on high load like 100 users/sec, it consumes 100% CPU and then due to lack of CPU slows down. Problem : Profiling the application gives me time taken by functions. This time increases on high load. Time consumed may be due to complex calculation or for waiting for CPU. so, how to find the CPU cycles consumed by a piece of code ? Since, reducing the CPU consumption will increase the response time. I might have written extremely efficient code and need to add more CPU power OR I might have some stupid code taking the CPU and causing the slow down ? Any help is appreciated ! Update: I am using Jmeter to profile my webapp, it gives me a throughput of 2 requests/sec. [ 100 users] I get a average time of 36 seconds on 100 request vs 1.25 sec time on 1 request. More Info Configuration Nginx + Uwsgi with 4 workers No database used, using a responses from a REST API On 1st hit the response of REST API gets cached, therefore doesn't makes a difference. Using ujson for json parsing. Curious to Know: Python-Django is used by so many orgs for so many big sites, then there must be some high end Debug / Memory-CPU analysis tools. All those I found were casual snippets of code that perform profiling.

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• Still some questions about USB

  - by b-gen-jack-o-neill

  Hi, few days ago I asked here about implementing USB. Now, If I may, would like to ask few more questions, about thing I dind´t quite understood. So, first, If I am right, Windows has device driver for USB interface, for the physical device that sends and receives communication. But what this driver offers to system (user)? I mean, USB protocol is made so its devices are adressed. So you first adress device than send message to it. But how sophisticted is the device controller (HW) and its driver? Is it so sophisticated that it is a chip you just send device adress and data, and it writes the outcomming data out and incomming data to some internal register to be read, or thru DMA directly to memory? Or, how its drivers (SW) really work? Does its driver has some advanced functions like send _data to _device? Becouse I somewhat internally hope there is a way to directly send some data thru USB, maybe by calling USB drivers itself? Is there any good article, tutorial you know about to really explain how all this logic works? Thanks.

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• How to know the type of an object in a list?

  - by nacho4d

  Hi, I want to know the type of object (or type) I have in my list so I wrote this: void **list; //list of references list = new void * [2]; Foo foo = Foo(); const char *not_table [] = {"tf", "ft", 0 }; list[0] = &foo; list[1] = not_table; if (dynamic_cast<LogicProcessor*>(list[0])) { //ERROR here ;( printf("Foo was found\n"); } if (dynamic_cast<char*> (list[0])) { //ERROR here ;( printf("char was found\n"); } but I get : error: cannot dynamic_cast '* list' (of type 'void*') to type 'class Foo*' (source is not a pointer to class) error: cannot dynamic_cast '* list' (of type 'void*') to type 'char*' (target is not pointer or reference to class) Why is this? what I am doing wrong here? Is dynamic_cast what I should use here? Thanks in advance EDIT: I know above code is much like plain C and surely sucks from the C++ point of view but is just I have the following situation and I was trying something before really implementing it: I have two arrays of length n but both arrays will never have an object at the same index. Hence, or I have array1[i]!=NULL or array2[i]!=NULL. This is obviously a waste of memory so I thought everything would be solved if I could have both kind of objects in a single array of length n. I am looking something like Cocoa's (Objective-C) NSArray where you don't care about the type of the object to be put in. Not knowing the type of the object is not a problem since you can use other method to get the class of a certain later. Is there something like it in c++ (preferably not third party C++ libraries) ? Thanks in advance ;)

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• Strategy for animation a lot of LED's - thread?, UIView animations? NSOperation? (iPhone)

  - by RickiG

  Hi I have to do some different views containing 72 LED lights. I built an LED Class so I can loop through the LED's and set them to different colors (Green, Red, Orange, Blue None etc.). The LED then loads the appropriate .png. This works fine, I loop over the LED's and set them. Now I know that at some time they will need to not just turn on/off change color, but will have to turn on with a small delay. Like an equalizer. I have a 5-10 views containing the 72 LED's and I would like to achieve the above with the minimum amount of memory/CPU strain. for(LED *l in self.ledArray) { [l display:Green]; } I simply loop as shown above and inside the LED is a switch case that does the correct logic. If this were actual LED's and a microController I would use sleep(100) or similar in the loop, but I would really like to avoid stuff like that for obvious reasons. I was thinking that doing a performOnThread withDelay would really be consuming, so would UIView animation changing the alpha and NSOperation would also be a lot of lifting for a small feature. Is there a both efficient and clever way to go around this? Thanks for any inspiration given:)

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• What is the most efficient way to handle points / small vectors in JavaScript?

  - by Chris

  Currently I'm creating an web based (= JavaScript) application thata is using a lot of "points" (= small, fixed size vectors). There are basically two obvious ways of representing them: var pointA = [ xValue, yValue ]; and var pointB = { x: xValue, y: yValue }; So translating my point a bit would look like: var pointAtrans = [ pointA[0] + 3, pointA[1] + 4 ]; var pointBtrans = { x: pointB.x + 3, pointB.y + 4 }; Both are easy to handle from a programmer point of view (the object variant is a bit more readable, especially as I'm mostly dealing with 2D data, seldom with 3D and hardly with 4D - but never more. It'll allways fit into x,y,z and w) But my question is now: What is the most efficient way from the language perspective - theoretically and in real implementations? What are the memory requirements? What are the setup costs of an array vs. an object? ... My target browsers are FireFox and the Webkit based ones (Chromium, Safari), but it wouldn't hurt to have a great (= fast) experience under IE and Opera as well...

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• localhost yes but phpmyadmin blank

  - by Giskin Leow

  WAMP people having problem with both localhost and phpmyadmin loads blank which usually the port problem. Mine is only phpmyadmin blank. sqlbuddy and phpinfo no problem. tried uninstall reinstalled wamp. tried xampp, same problem, all works well, not phpmyadmin. mysql log: 120905 8:03:08 [Note] Plugin 'FEDERATED' is disabled. 120905 8:03:08 InnoDB: The InnoDB memory heap is disabled 120905 8:03:08 InnoDB: Mutexes and rw_locks use Windows interlocked functions 120905 8:03:08 InnoDB: Compressed tables use zlib 1.2.3 120905 8:03:09 InnoDB: Initializing buffer pool, size = 128.0M 120905 8:03:09 InnoDB: Completed initialization of buffer pool 120905 8:03:09 InnoDB: highest supported file format is Barracuda. 120905 8:03:09 InnoDB: Waiting for the background threads to start 120905 8:03:10 InnoDB: 1.1.8 started; log sequence number 1595675 120905 8:03:11 [Note] Server hostname (bind-address): '(null)'; port: 3306 120905 8:03:11 [Note] - '(null)' resolves to '::'; 120905 8:03:11 [Note] - '(null)' resolves to '0.0.0.0'; 120905 8:03:11 [Note] Server socket created on IP: '0.0.0.0'. 120905 8:03:13 [Note] Event Scheduler: Loaded 0 events 120905 8:03:13 [Note] wampmysqld: ready for connections. apache log [Wed Sep 05 08:03:09 2012] [notice] Apache/2.2.22 (Win32) PHP/5.4.3 configured -- resuming normal operations [Wed Sep 05 08:03:09 2012] [notice] Server built: May 13 2012 13:32:42 [Wed Sep 05 08:03:09 2012] [notice] Parent: Created child process 3812 [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Child process is running [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Acquired the start mutex. [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Starting 64 worker threads. [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Starting thread to listen on port 80. [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Starting thread to listen on port 80. [Wed Sep 05 08:04:14 2012] [error] [client 127.0.0.1] File does not exist: C:/wamp/www/favicon.ico [Wed Sep 05 08:09:50 2012] [error] [client 127.0.0.1] File does not exist: C:/wamp/www/favicon.ico [Wed Sep 05 08:41:03 2012] [error] [client 127.0.0.1] File does not exist: C:/wamp/www/phpMyAdmin

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• segmentation fault when using pointer to pointer

  - by user3697730

  I had been trying to use a pointer to pointer in a function,but is seems that I am not doing the memory allocation correctly... My code is: #include<stdio.h> #include<math.h> #include<ctype.h> #include<stdlib.h> #include<string.h> struct list{ int data; struct list *next; }; void abc (struct list **l,struct list **l2) { *l2=NULL; l2=(struct list**)malloc( sizeof(struct list*)); (*l)->data=12; printf("%d",(*l)->data); (*l2)->next=*l2; } int main() { struct list *l,*l2; abc(&l,&l2); system("pause"); return(0); } This code compiles,but I cannot run thw program..I get a segmentation fault..What should I do?Any help would be appreciated!

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• Vacancy Tracking Algorithm implementation in C++

  - by Dave

  I'm trying to use the vacancy tracking algorithm to perform transposition of multidimensional arrays in C++. The arrays come as void pointers so I'm using address manipulation to perform the copies. Basically, there is an algorithm that starts with an offset and works its way through the whole 1-d representation of the array like swiss cheese, knocking out other offsets until it gets back to the original one. Then, you have to start at the next, untouched offset and do it again. You repeat until all offsets have been touched. Right now, I'm using a std::set to just fill up all possible offsets (0 up to the multiplicative fold of the dimensions of the array). Then, as I go through the algorithm, I erase from the set. I figure this would be fastest because I need to randomly access offsets in the tree/set and delete them. Then I need to quickly find the next untouched/undeleted offset. First of all, filling up the set is very slow and it seems like there must be a better way. It's individually calling new[] for every insert. So if I have 5 million offsets, there's 5 million news, plus re-balancing the tree constantly which as you know is not fast for a pre-sorted list. Second, deleting is slow as well. Third, assuming 4-byte data types like int and float, I'm using up actually the same amount of memory as the array itself to store this list of untouched offsets. Fourth, determining if there are any untouched offsets and getting one of them is fast -- a good thing. Does anyone have suggestions for any of these issues?

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• Strange code behaviour?

  - by goldenmean

  Hi, I have a C code in which i have a structure declaration which has an array of int[576] declared in it. For some reason, i had to remove this array from the structure, So i replaced this array with a pointer as int *ptr; declared some global array of same type, somewhere else in the code, and initialized this pointer by assigning the global array to this pointer. So i did not have to change the way i was accessing this array, from other parts of my code. But it works fine/gives desired output when i have the array declared in the structure, but it gives junk output when i declare it as a pointer in the structure and assign a global array to this pointer, as a part of the pointer initialization. All this code is being run on MS-VC 6.0/Windows setup/Intel-x86. I tried below things: 1)Suspected structure padding/alignment but could not get any leads? If at all structure alignment could be a culprit how can i proceed to narrow it down and confirm it? 2) I have made sure that in both cases the array is initialized to some default values, say 0 before its first use, and its not being used before initialization. 3)I tried using global array as well as malloc based memory for this newly declared array. Same result, junk output. Am i missing something? How can i zero down the problem. Any pointers would be helpful. Thanks, -AD.

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• Problem with passing array of pointers to struct among functions in C

  - by karatemonkey

  The Code that follows segfaults on the call to strncpy and I can't see what I am doing wrong. I need another set of eyes to look it this. Essentially I am trying to alloc memory for a struct that is pointed to by an element in a array of pointers to struct. #include <stdio.h> #include <stdlib.h> #include <string.h> #define MAX_POLICY_NAME_SIZE 64 #define POLICY_FILES_TO_BE_PROCESSED "SPFPolicyFilesReceivedOffline\0" typedef struct TarPolicyPair { int AppearanceTime; char *IndividualFile; char *FullPolicyFile; } PolicyPair; enum { bwlist = 0, fzacts, atksig, rules, MaxNumberFileTypes }; void SPFCreateIndividualPolicyListing(PolicyPair *IndividualPolicyPairtoCreate ) { IndividualPolicyPairtoCreate = (PolicyPair *) malloc(sizeof(PolicyPair)); IndividualPolicyPairtoCreate->IndividualFile = (char *)malloc((MAX_POLICY_NAME_SIZE * sizeof(char))); IndividualPolicyPairtoCreate->FullPolicyFile = (char *)malloc((MAX_POLICY_NAME_SIZE * sizeof(char))); IndividualPolicyPairtoCreate->AppearanceTime = 0; memset(IndividualPolicyPairtoCreate->IndividualFile, '\0', (MAX_POLICY_NAME_SIZE * sizeof(char))); memset(IndividualPolicyPairtoCreate->FullPolicyFile, '\0', (MAX_POLICY_NAME_SIZE * sizeof(char))); } void SPFCreateFullPolicyListing(SPFPolicyPair **CurrentPolicyPair, char *PolicyName, char *PolicyRename) { int i; for(i = 0; i < MaxNumberFileTypes; i++) { CreateIndividualPolicyListing((CurrentPolicyPair[i])); // segfaults on this call strncpy((*CurrentPolicyPair)[i].IndividualFile, POLICY_FILES_TO_BE_PROCESSED, (SPF_POLICY_NAME_SIZE * sizeof(char))); } } int main() { SPFPolicyPair *CurrentPolicyPair[MaxNumberFileTypes] = {NULL, NULL, NULL, NULL}; int i; CreateFullPolicyListing(&CurrentPolicyPair, POLICY_FILES_TO_BE_PROCESSED, POLICY_FILES_TO_BE_PROCESSED); return 0; }

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• Variable Scoping in a method and its persistence in C++

  - by de costo

  Consider the following public method that adds an integer variable to a vector of ints(private member) in a class in C++. KoolMethod() { int x; x = 10; KoolList.Add(x); } Vector<int>KoolList; But is this a valid addition to a vector ??? Upon calling the method, it creates a local variable. The scope of this local variable ends the moment the execution control leaves the method. And since this local variable is allocated on a stack(on the method call), any member of KoolList points to an invalid memory location in deallocated stack which may or may not contain the expected value of x. Is this an accurate description of above mechanism ?? Is there a need for creating an int in heap storage using "new" operator everytime a value needs to be added to the vector like described below ????: KoolMethod() { int *x = new int(); *x = 10; KoolList.Add(x); } Vector<int*>KoolList;

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• Good C string libary

  - by chamakits

  Hello all. I recently got inspired to start up a project I've been wanting to code for a while. I want to do it in C, because memory handling is key this application. I was searching around for a good implementation of strings in C, since I know me doing it myself could lead to some messy buffer overflows, and I expect to be dealing with a fairly big amount of strings. I found this article which gives details on each, but they each seem like they have a good amount of cons going for them (don't get me wrong, this article is EXTREMELY helpful, but it still worries me that even if I were to choose one of those, I wouldn't be using the best I can get). I also don't know how up to date the article is, hence my current plea. What I'm looking for is something that may hold a large amount of characters, and simplifies the process of searching through the string. If it allows me to tokenize the string in any way, even better. Also, it should have some pretty good I/O performance. Printing, and formatted printing isn't quite a top priority. I know I shouldn't expect a library to do all the work for me, but was just wandering if there was a well documented string function out there that could save me some time and some work. Any help is greatly appreciated. Thanks in advance! EDIT: I was asked about the license I prefer. Any sort of open source license will do, but preferably GPL (v2 or v3). EDIt2: I found betterString (bstring) library and it looks pretty good. Good documentation, small yet versatile amount of functions, and easy to mix with c strings. Anyone have any good or bad stories about it? The only downside I've read about it is that it lacks Unicode (again, read about this, haven't seen it face to face just yet), but everything else seems pretty good. EDIT3: Also, preferable that its pure C.

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• Pointers to a typed variable in C#: Interfase, Generic, object or Class? (Boxing/Unboxing)

  - by PaulG

  First of all, I apologize if this has been asked a thousand times. I read my C# book, I googled it, but I can't seem to find the answer I am looking for, or I am missing the point big time. I am very confused with the whole boxing/unboxing issue. Say I have fields of different classes, all returning typed variables (e.g. 'double') and I would like to have a variable point to any of these fields. In plain old C I would do something like: double * newVar; newVar = &oldVar; newVar = &anotherVar; ... In C#, it seems I could do an interfase, but would require that all fields be properties and named the same. Breaks apart when one of the properties doesn't have the same name or is not a property. I could also create a generic class returning double, but seems a bit absurd to create a class to represent a 'double', when a 'double' class already exists. If I am not mistaken, it doesn't even need to be generic, could be a simple class returning double. I could create an object and box the typed variable to the newly created object, but then I would have to cast every time I use it. Of course, I always have the unsafe option... but afraid of getting to unknown memory space, divide by zero and bring an end to this world. None of these seem to be the same as the old simple 'double * variable'. Am I missing something here?

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