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  • Char * reallocation in C++

    - by JTom
    Hi, I need to store a certain amount of data in the "char *" in C++, because I want to avoid std::string to run out of memory, when exceeding max_size(). But the data comes in data blocks from the network so I need to use reallocation every time I get the data block. Is there any elegant solution for char * reallocation and concatenation in C++?

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  • [java] run 2 threads simultaneously

    - by lamsaitat
    hi all, in the case of an IM client. i have made 2 separate threads to handle sending packets (by std io) and receiving packets. the question is how to make these 2 threads run simultaneously so that i can keep prompting for input while at the same time be ready to receive packets at any time? i have already tried setting a timer but the data is always lost receiving.

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  • pointer to preallocated memory as an input parameter and have the function fill it

    - by djones2010
    test code: void modify_it(char * mystuff) { char test[7] = "123456"; //last element is null i presume for c style strings here. //static char test[] = "123123"; //when i do this i thought i should be able to gain access to this bit of memory when the function is destroyed but that does not seem to be the case. //char * test = new char[7]; //this is also creating memory on stack and not the heap i reckon and gets destroyed once the function is done with. strcpy_s(mystuff,7,test); //this does the job as long as memory for mystuff has been allocated outside the function. mystuff = test; //this does not work. I know with c style strings you can't just do string assignments they have to be actually copied. in this case I was using this in conjunction with static char test thinking by having it as static the memory would not get destroyed and i can then simply point mystuff to test and be done with it. i would later have address the memory cleanup in the main function. but anyway this never worked. } int main(void) { char * mystuff = new char [7]; //allocate memory on heap where the pointer will point cool(mystuff); std::string test_case(mystuff); std::cout<<test_case.c_str(); //this is the only way i know how to use cout by making it into a string c++ string. delete [] mystuff; return 0; } in the case, of a static array in the function why would it not work. in the case, when i allocated memory using new in the function does it get created on the stack or heap? in the case, i have string which needs to be copied into a char * form. everything i see usually requires const char* instead of just char*. I know i could use reference to take care of this easy. Or char ** to send in the pointer and do it that way. But i just wanted to know if I could do it with just char *. Anyway your thoughts and comments plus any examples would be very helpful.

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  • Best way to render Tesselated Objects (OpenGL)

    - by user146780
    I'm using the GLUTesselator for Polygons. Right now the vertex callback does glvertex2f and gltex2f. Would it be better simply to collect the verticies from the vertex callback in a std::vector then use gldrawarrays()? Or would this actually be less efficient since it has to put the verts and texture coordinates in a vector? Thanks

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  • C++ UTF-8 lightweight & permissive code?

    - by xenthral
    Anyone know of a more permissive license (MIT / public domain) version of this: http://library.gnome.org/devel/glibmm/unstable/classGlib_1_1ustring.html ('drop-in' replacement for std::string thats UTF-8 aware) Lightweight, does everything I need and even more (doubt I'll use the UTF-XX conversions even) I really don't want to be carrying ICU around with me.

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  • c++ Function pointer inlining

    - by wb
    I know I can pass a function pointer as a template parameter and get a call to it inlined but I wondered if any compilers these days can inline an 'obvious' inline-able function like: inline static void Print() { std::cout << "Hello\n"; } .... void (*func)() = Print; func(); Under Visual Studio 2008 its clever enough to get it down to a direct call instruction so it seems a shame it can't take it a step further?

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  • Why can't I reserve 1,000,000,000 in my vector ?

    - by vipersnake005
    When I type in the foll. code, I get the output as 1073741823. #include <iostream> #include <vector> using namespace std; int main() { vector <int> v; cout<<v.max_size(); return 0; } However when I try to resize the vector to 1,000,000,000, by v.resize(1000000000); the program stops executing. How can I enable the program to allocate the required memory, when it seems that it should be able to? I am using MinGW in Windows 7. I have 2 GB RAM. Should it not be possible? In case it is not possible, can't I declare it as an array of integers and get away? BUt even that doesn't work. Another thing is that, suppose I would use a file(which can easily handle so much data ). How can I let it read and write and the same time. Using fstream file("file.txt', ios::out | ios::in ); doesn't create a file, in the first place. But supposing the file exists, I am unable to use to do reading and writing simultaneously. WHat I mean is this : Let the contents of the file be 111111 Then if I run : - #include <fstream> #include <iostream> using namespace std; int main() { fstream file("file.txt",ios:in|ios::out); char x; while( file>>x) { file<<'0'; } return 0; } Shouldn't the file's contents now be 101010 ? Read one character and then overwrite the next one with 0 ? Or incase the entire contents were read at once into some buffer, should there not be atleast one 0 in the file ? 1111110 ? But the contents remain unaltered. Please explain. Thank you.

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  • Running 2 threads simultaneously

    - by lamsaitat
    In the case of an IM client. I have made 2 separate threads to handle sending packets (by std io) and receiving packets. The question is how to make these 2 threads run simultaneously so that I can keep prompting for input while at the same time be ready to receive packets at any time? I have already tried setting a timer but the data is always lost receiving.

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  • Is `std::string(strerror(errno))` dangerous?

    - by StackedCrooked
    At some places in my code, I print debug messages like this: int ret = getLinkSpeed(device.getSysName(), linkSpeed); if (ret < 0) { logDebug("Failed to obtain port speed for this device. Error: " + std::string(strerror(errno))); } From the documentation it is not entirely clear if strerror will return 0 under certain conditions (which would cause my code to crash). Does anyone know if it's safe?

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  • how a thread can signal when it's finished?

    - by Kyle
    #include <iostream> #include <boost/thread.hpp> using std::endl; using std::cout; using namespace boost; mutex running_mutex; struct dostuff { volatile bool running; dostuff() : running(true) {} void operator()(int x) { cout << "dostuff beginning " << x << endl; this_thread::sleep(posix_time::seconds(2)); cout << "dostuff is done doing stuff" << endl; mutex::scoped_lock running_lock(running_mutex); running = false; } }; bool is_running(dostuff& doer) { mutex::scoped_lock running_lock(running_mutex); return doer.running; } int main() { cout << "Begin.." << endl; dostuff doer; thread t(doer, 4); if (is_running(doer)) cout << "Cool, it's running.\n"; this_thread::sleep(posix_time::seconds(3)); if (!is_running(doer)) cout << "Cool, it's done now.\n"; else cout << "still running? why\n"; // This happens! :( return 0; } Why is the output of the above program: Begin.. Cool, it's running. dostuff beginning 4 dostuff is done doing stuff still running? why How can dostuff correctly flag when it is done? I do not want to sit around waiting for it, I just want to be notified when it's done.

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  • Why doesn't this inner class compile?

    - by Vincenzo
    This is my code: #include <algorithm> class A { void f() { struct CompareMe { bool operator() (int i, int j) { return i < j; } } comp; int a[] = {1, 2, 3, 4}; int found = std::min_element(a[0], a[3], comp); } } Error message: no matching function for call to ‘min_element(int&, int&, A::f()::CompareMe&) What am I doing wrong?

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  • Is it safe to read global data from multiple threads?

    - by user362515
    The scenario is as follows: Create an instance of a class (std::map) and sore it as global variable. Spawn threads. Threads read and use the same global instance of the class All spawned threads quit Global class instance is destroyed No mutex, no thread modifies the global class instance. Is this OK? Thank You

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  • Array help in C++

    - by user267237
    I am writing a program that is declaring an array of 100 integer numbers and filling the array with random numbers using rand(). All I have so far is: #include <iostream> using namespace std; int main() { int random_integer = rand();

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  • Is it save to read global data from multiple threads?

    - by user362515
    The scenario is as follows: Create an instance of a class (std::map) and sore it as global variable. Spawn threads. Threads read and use the same global instance of the class All spawned threads quit Global class instance is destroyed No mutex, no thread modifies the global class instance. Is it ok? Thank You

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  • Read All Files in Directory?

    - by cam
    How would I go about reading all files in a directory? In C# I would get a DirectoryInfo object, and get all files into a FileInfo[] object. Is there similar functionality in the STD namespace in C++?

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  • something about C++ unnamed namespace.

    - by Javran
    #include <iostream> namespace { int a=1; } int a=2,b=3; int main(void) { std::cout<<::a<<::b; return 0; } I complie it with my g++,but the output is 23, who can explain it? is that a way to get access to the <unnamed> namespace ::a?

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  • Custom InputIterator for Boost graph (BGL)

    - by Shadow
    Hi, I have a graph with custom properties to the vertices and edges. I now want to create a copy of this graph, but I don't want the vertices to be as complex as in the original. By this I mean that it would suffice that the vertices have the same indices (vertex_index_t) as they do in the original graph. Instead of doing the copying by hand I wanted to use the copy-functionality of boost::adjacency_list (s. http://www.boost.org/doc/libs/1_37_0/libs/graph/doc/adjacency_list.html): template <class EdgeIterator> adjacency_list(EdgeIterator first, EdgeIterator last, vertices_size_type n, edges_size_type m = 0, const GraphProperty& p = GraphProperty()) The description there says: The EdgeIterator must be a model of InputIterator. The value type of the EdgeIterator must be a std::pair, where the type in the pair is an integer type. The integers will correspond to vertices, and they must all fall in the range of [0, n). Unfortunately I have to admit that I don't quite get it how to define an EdgeIterator that is a model of InputIterator. Here's what I've succeded so far: template< class EdgeIterator, class Edge > class MyEdgeIterator// : public input_iterator< std::pair<int, int> > { public: MyEdgeIterator() {}; MyEdgeIterator(EdgeIterator& rhs) : actual_edge_it_(rhs) {}; MyEdgeIterator(const MyEdgeIterator& to_copy) {}; bool operator==(const MyEdgeIterator& to_compare) { return actual_edge_it_ == to_compare.actual_edge_it_; } bool operator!=(const MyEdgeIterator& to_compare) { return !(*this == to_compare); } Edge operator*() const { return *actual_edge_it_; } const MyEdgeIterator* operator->() const; MyEdgeIterator& operator ++() { ++actual_edge_it_; return *this; } MyEdgeIterator operator ++(int) { MyEdgeIterator<EdgeIterator, Edge> tmp = *this; ++*this; return tmp; } private: EdgeIterator& actual_edge_it_; } However, this doesn't work as it is supposed to and I ran out of clues. So, how do I define the appropriate InputIterator?

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  • Exchange Server 2007 Setup

    - by AlamedaDad
    Hi, I'm working on a upgrade to Exchange 2007 and I wanted to get some advise on hardware choices. We currently have an Exchange 2003 STD server with 400 users split between 6 AD Sites, that is housed on a single server. We need to move to a redundant, fault tolerant system to support our users. I'm planning on installing 2 Dell 1950 servers with W2k8-std to act as CAS and Hub servers, with NLB to allow abstraction of the actual server name to the users. There won't be an edge system since we have a Barracuda box already that will handle in/out spam/virus filtering. Backend I'm planning on 2 mailbox servers which will be Dell 2950s with 16GB RAM, 2 either dual-core or quad-core CPUs and 6 300GB SAS drives in some RAID config. These systems will be clustered using W2k8 Ent clustering and running CCR in Exchange. My questions are as follows: Is 16GB enough RAM for serving that many mailboxes along with the windows clustering and ccr? I'm trying to figure out disk layouts and I'm unsure of whether to use all local disk or some local and some SAN, via an OpenFiler iSCSI server. The SAN would be a Dell 2850 with 6 - 300GB SCSI drives and a PERC controller to slice as I want, with 8GB RAM. Option 1: 2 drives, RAID 1 - OS 2 drives, RAID 1 - Logs 2 drives, RAID 1 - Mail stores Option 2: 2 drives, RAID 1 - OS and logs 4 drives, RAID 5 - Mail Stores and scratch space for eseutil. Option 3: 2 drives, RAID 1 - OS 2 drives, RAID 1 - Logs 2 drives, RAID 0 - scratch space ~300GB iSCSI volume for mail stores Option 4: 2 drives, RAID 1 - OS 4 drives, RAID 5 - scratch space ~300GB iSCSI volume for mail stores ~300GB iSCSI volume for logs I have 2 sockets for CPUs and need to chose between dual and quad cores. The dual core have faster clocks but less cache and I'm thinking older architecture. Am I better off with more cores and cache while sacraficing clock speed? I am planning on adding the new E2K7 cluster to the E2K3 server and then move each mailbox over, all at once, then remove the old server. This seems more complicated than simply getting rid of the 2003 server and then adding the 2007 cluster and restoring the mailboxes using PowerControls or exmerge. The migration option lets me do this on my time, where a cutover means it all needs to work at once. If I go with the cutover method, how can I prebuild the servers and add them to the domain right after removing the 2003 server, or can't I? I think the answer is no and the migration is my only real option if I want to prebuild. I need to also migrate about 30GB of Public Folders. Is there anything special about this, other than specifying in the E2K7 install that I want older Outlook clients and PF's setup? I guess I could even keep the E2K3 server to host just the PFs? Lastly, if I have a mix of Outlook 200, 2003 and 2007 what do I need to do to make sure they all have access to the GAL and OAB? At time of cutover, we'll be at like 90% 2007, but we will have some older stuff around. My plan is to use Outlook Anywhere on laptops that are used outside the physical network. Are there any gotchas involved in that? I'm even thinking about using is for all Outlook clients, does anyone do that? The reason I'm considering it is that our WAN is really VPN tunnels over internet connections, so not a fully messhed, stable WAN. Thank you all very much for the assistance in advance and I look forward to discussion of these points! Regards...Michael

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