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  • How can I load a SQLITE database from a buffer with the C API ?

    - by rockeye
    Hello, I am trying to load a database from the memory instead of opening a .sqlite file. I have read the C/C++ API reference but I can not find the proper method. The buffer I am trying to load is simply an sqlite file loaded in memory. I just want to use this buffer (a const char* array) without using the filesystem (I could have saved this buffer in a file, then load the file, but no). First, I create a memory DB : mErrorCode = sqlite3_open_v2(":memory:", &mSqlDatabase, lMode, NULL); This returns SQLITE_OK, then I tried to use the buffer as a statement and call preparev2(MyDB, MyBufferData, MyBufferLength, MyStatement, NULL) but it's not really a statement, and it returns an error. Same result if I call directly exec(MyDB, MyBufferData, NULL, NULL, NULL); I guess there is an appropriate method to achieve this as it might be common to load a DB from a stream or from decrypted data... Thanks.

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  • Using Boost statechart, how can I transition to a state unconditionally?

    - by nickb
    I have a state A that I would like to transition to its next state B unconditionally, once the constructor of A has completed. Is this possible? I tried posting an event from the constructor, which does not work, even though it compiles. Thanks. Edit: Here is what I've tried so far: struct A : sc::simple_state< A, Active > { public: typedef sc::custom_reaction< EventDoneA > reactions; A() { std::cout << "Inside of A()" << std::endl; post_event( EventDoneA() ); } sc::result react( const EventDoneA & ) { return transit< B >(); } }; This yields the following runtime assertion failure: Assertion failed: get_pointer( pContext_ ) != 0, file /includ e/boost/statechart/simple_state.hpp, line 459

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  • Is call to function object inlined?

    - by dehmann
    In the following code, Foo::add calls a function via a function object: struct Plus { inline int operator()(int x, int y) const { return x + y; } }; template<class Fct> struct Foo { Fct fct; Foo(Fct f) : fct(f) {} inline int add(int x, int y) { return fct(x,y); // same efficiency adding directly? } }; Is this the same efficiency as calling x+y directly in Foo::add? In other words, does the compiler typically directly replace fct(x,y) with the actual call, inlining the code, when compiling with optimizations enabled?

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  • Possible to convert list of #defines into strings (C++)

    - by brandonC
    Suppose I have a list of #defines in a header file for an external library. These #defines represent error codes returned from functions. I want to write a conversion function that can take as an input an error code and return as an output a string literal representing the actual #define name. As an example, if I have #define NO_ERROR 0 #define ONE_KIND_OF_ERROR 1 #define ANOTHER_KIND_OF_ERROR 2 I would like a function to be able to called like int errorCode = doSomeLibraryFunction(); if (errorCode) writeToLog(convertToString(errorCode)); And have convertToString() be able to auto-convert that error code without being a giant switch-case looking like const char* convertToString(int errorCode) { switch (errorCode) { case NO_ERROR: return "NO_ERROR"; case ONE_KIND_OF_ERROR: return "ONE_KIND_OF_ERROR"; ... ... ... I have a feeling that if this is possible, it would be possible using templates and metaprogramming, but that would only work the error codes were actually a type and not a bunch of processor macros. Thanks

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  • sysklogd ignores my log facilities

    - by Synther Lawrence
    I'm using sysklogd 1.5.5. All I want is to get local0 entries in /var/log/vr file. My conf: *.*;local0.none /var/log/messages local0.* /var/log/vr When I do logger -p local0.info "local0 test from logger" the message appear in /var/log/vr file. That's ok. But the following sends message to /var/log/messages instead of /var/log/vr: #include <stdlib.h> #include <syslog.h> int main(int argc, char const* argv[]) { openlog(NULL, LOG_PID, LOG_LOCAL0); syslog(LOG_INFO, "local0 test from app\n"); closelog(); return 0; } Where am I wrong?

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  • How to return a 'read-only' copy of a vector

    - by michael
    Hi, I have a class which has a private attribute vector rectVec; class A { private: vector<Rect> rectVec; }; My question is how can I return a 'read-only' copy of my Vector? I am thinking of doing this: class A { public: const vect<Rect>& getRectVec() { return rectVect; } } Is that the right way? I am thinking this can guard against the callee modify the vector(add/delete Rect in vector), what about the Rect inside the vector?

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  • using arrays to get best memory alignment and cache use, is it necessary?

    - by Alberto Toglia
    I'm all about performance these days cause I'm developing my first game engine. I'm no c++ expert but after some research I discovered the importance of the cache and the memory alignment. Basically what I found is that it is recommended to have memory well aligned specially if you need to access them together, for example in a loop. Now, In my project I'm doing my Game Object Manager, and I was thinking to have an array of GameObjects references. meaning I would have the actual memory of my objects one after the other. static const size_t MaxNumberGameObjects = 20; GameObject mGameObjects[MaxNumberGameObjects]; But, as I will be having a list of components per object -Component based design- (Mesh, RigidBody, Transformation, etc), will I be gaining something with the array at all? Anyway, I have seen some people just using a simple std::map for storing game objects. So what do you guys think? Am I better off using a pure component model?

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  • boost scoped_lock mutex crashes

    - by JahSumbar
    hello, I have protected a std::queue's access functions, push, pop, size, with boost::mutexes and boost::mutex::scoped_lock in these functions from time to time it crashes in a scoped lock the call stack is this: 0 0x0040f005 boost::detail::win32::interlocked_bit_test_and_set include/boost/thread/win32/thread_primitives.hpp 361 1 0x0040e879 boost::detail::basic_timed_mutex::timed_lock include/boost/thread/win32/basic_timed_mutex.hpp 68 2 0x0040e9d3 boost::detail::basic_timed_mutex::lock include/boost/thread/win32/basic_timed_mutex.hpp 64 3 0x0040b96b boost::unique_lock<boost::mutex>::lock include/boost/thread/locks.hpp 349 4 0x0040b998 unique_lock include/boost/thread/locks.hpp 227 5 0x00403837 MyClass::inboxSize - this is my inboxSize function that uses this code: MyClass::inboxSize () { boost::mutex::scoped_lock scoped_lock(m_inboxMutex); return m_inbox.size(); } and the mutex is declared like this: boost::mutex m_inboxMutex; it crashes at the last pasted line in this function: inline bool interlocked_bit_test_and_set(long* x,long bit) { long const value=1<<bit; long old=*x; and x has this value: 0xababac17 Thanks for the help

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  • how to use static function in header and compare with float array

    - by ed k
    I wrote this function: static bool colorIsEmpty(const Color col) { return (col[0] == 0 && col[1] == 0 && col[2] == 0 ); } where Color is simply a float[3]; the function doesn't work if col[3] are all 0; but this works: if(col[0] == col[1] == col[2] == 0) { //gets called } however gcc gives me warning: cColorTest.c:212:5: warning: suggest parentheses around comparison in operand of ‘==’ [-Wparentheses] so it would be nice if that function works,why it doesn't work?

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  • Passing a pointer to an array to glGenBuffers

    - by Josh Elsasser
    I'm currently passing an array to a function, then attempting to use glGenBuffers with the array that is passed to the function. I can't figure out a way to get glGenBuffers to work with the array that I've passed. I have a decent grasp of the basics of pointers, but this is beyond me. This is basically how the render code works. It's a bit more complex, (colours using the same array idea, also not working) but the basic idea is as follows: void drawFoo(const GLfloat *renderArray, GLuint verticeBuffer) { glBindBuffer(GL_ARRAY_BUFFER, verticeBuffer); glBufferData(GL_ARRAY_BUFFER, sizeof(verticeBuffer)*sizeof(GLfloat), verticeBuffer, GL_STATIC_DRAW); glVertexPointer(2, GL_FLOAT, 0, 0); glEnableClientState(GL_VERTEX_BUFFER); glDrawArrays(GL_TRIANGLE_FAN, 0, 45); glDisableClientState(GL_VERTEX_BUFFEr); } Thanks in advance for the help

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  • Delphi 2010 - Why can't I declare an abstract method with a generic type parameter?

    - by James
    I am trying to do the following in Delphi 2010: TDataConverter = class abstract public function Convert<T>(const AData: T): string; virtual; abstract; end; However, I keep getting the following compiler error: E2533 Virtual, dynamic and message methods cannot have type parameters I don't quite understand the reason why I can't do this. I can do this in C# e.g. public abstract class DataConverter { public abstract string Convert<T>(T data); } Anyone know the reasoning behind this?

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  • How to pass and set a CGFloat by reference?

    - by mystify
    I want to make an method which takes an CGFloat by reference. Could I do something like this? - (void)doStuff:(CGFloat*)floatPointer I guess this must look different than other object pointers which have two of those stars. Also I'm not sure if I must do something like: - (void)doStuff:(const CGFloat*)floatPointer And of course, no idea how to assign an CGFloat value to that floatPointer. Maybe &floatPointer = 5.0f; ? Could someone give some examples and explain these? Would be great!

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  • EXC_BAD_ACCESS from AudioBuffer

    - by jfalexvijay
    I am trying to do the record using AudioUnit for iPhone app. Changes: (start) I have added the following code bufferList = (AudioBufferList *)malloc(sizeof(AudioBuffer)); bufferList-mNumberBuffers = 1; bufferList-mBuffers[0].mNumberChannels = 2; bufferList-mBuffers[0].mDataByteSize = 1024; bufferList-mBuffers[0].mData = calloc(256, sizeof(uint32_t)); Changes: (end) static OSStatus recordingCallback(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData) { OSStatus status; status = AudioUnitRender(appdelegate-audioUnit, ioActionFlags, inTimeStamp, inBusNumber, inNumberFrames, appdelegate-bufferList); if(status != 0) NSLog(@"AudioUnitRender status is %d", status); SInt16* samples = (SInt16*)(ioData-mBuffers[0].mData); ..... } fixed: (I am getting OSStatus -50 error code)- Because I didn't initialize the bufferList. I am EXC_BAD_ACCESS from AudioBuffer (ioData-mBuffers[0].mData). I am not sure with this error. Please help me to resolve it.

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  • Solving C++ 'target of assignment not really an lvalue' errors

    - by Jason
    Given this code: void FrMemCopy(void *to, const void *from, size_t sz) { size_t sz8 = sz >> 3; size_t sz1 = sz - (sz8 << 3); while (sz8-- != 0) { *((double *)to)++ = *((double *)from)++; } while (sz1-- != 0) { *((char *)to)++ = *((char *)from)++; } } I am receiving target of assignment not really an lvalue warnings on the 2 lines inside the while loops. Can anyone break down those lines? a cast then an increment? What is a simplier way to write that? What does the error mean?

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  • GCC fatal error: stdio.h: No such file or directory

    - by user2615799
    I'm trying to compile a program in C on OS X 10.9 with GCC 4.9 (experimental). For some reason, I'm getting the following error at compile time: gcc: fatal error: stdio.h: No such file or directory I then tried a simple Hello World program: #include <stdio.h> int main(int *argc, const char *argv[]) { printf("Hello, world!"); return 0; } Again, upon running gcc -o ~/hello ~/hello.c, I got the same error. I'm using an experimental version of gcc, but it seems implausible that there would be a release which generated errors upon importing stdio. What could be causing this issue, and how can it be fixed?

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  • How to insert into std::map.

    - by Knowing me knowing you
    In code below: map<string,vector<int>> create(ifstream& in, const vector<string>& vec) { /*holds string and line numbers into which each string appears*/ typedef map<string,vector<int>> myMap; typedef vector<string>::const_iterator const_iter; myMap result; string tmp; unsigned int lineCounter = 0; while(std::getline(in,tmp)) { const_iter beg = vec.begin(); const_iter end = vec.end(); while (beg < end) { if ( tmp.find(*beg) != string::npos) { result[*beg].push_back(lineCounter);//THIS IS THE LINE I'M ASKING FOR } ++beg; } ++lineCounter; } return result; } How should I do it (check line commented in code) if I want to use insert method of map instead of using operator[]? Thank you.

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  • Large amount of constants in Java

    - by Lars D
    I need to include about 1 MByte of data in a Java application, for very fast and easy access in the rest of the source code. My main background is not Java, so my initial idea was to convert the data directly to Java source code, defining 1MByte of constant arrays, classes (instead of C++ struct) etc., something like this: public final/immutable/const MyClass MyList[] = { { 23012, 22, "Hamburger"} , { 28375, 123, "Kieler"} }; However, it seems that Java does not support such constructs. Is this correct? If yes, what is the best solution to this problem?

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  • Does a c/c++ compiler optimize constant divisions by power-of-two value into shifts?

    - by porgarmingduod
    Question says it all. Does anyone know if the following... size_t div(size_t value) { const size_t x = 64; return value / x; } ...is optimized into? size_t div(size_t value) { return value >> 6; } Do compilers do this? (My interest lies in GCC). Are there situations where it does and others where it doesn't? I would really like to know, because every time I write a division that could be optimized like this I spend some mental energy wondering about whether precious nothings of a second is wasted doing a division where a shift would suffice.

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  • How to retrieve all keys (or values) from a std::map?

    - by Owen
    This is one of the possible ways I come out: struct RetrieveKey { template <typename T> typename T::first_type operator()(T keyValuePair) const { return keyValuePair.first; } }; map<int, int> m; vector<int> keys; // Retrieve all keys transform(m.begin(), m.end(), back_inserter(keys), RetrieveKey()); // Dump all keys copy(keys.begin(), keys.end(), ostream_iterator<int>(cout, "\n")); Of course, we can also retrieve all values from the map by defining another functor RetrieveValues. Is there any other way to achieve this easily? (I'm always wondering why std::map does not include a member function for us to do so.)

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  • Printing escape character

    - by danutenshu
    When I am given "d""\"/""b", I need to print out the statement character for character. (d, b, a slash, a backslash, and 5 quotes) in C++. The only errors that show now are the lines if(i.at(j)="\\") and else if(i.at(j)="\""). Also, how should the outside double apostrophes be excluded? #include <iostream> #include <cstdlib> using namespace std; int main (int argc, const char* argv[] ) { string i= argv[1]; for (int j=0; j>=sizeof(i)-1; j++) { if(i.at(j)="\\") { cout << "\\"; } else if(i.at(j)="\"") { cout << "\""; } else { cout << i.at(j); } } return 0; }

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  • .NET's double.NaN - how does this counterintuitive feature work?

    - by GeReV
    I stumbled upon the definition of double.NaN in code: public const double NaN = (double)0.0 / (double)0.0; This is done similarly in PositiveInfinity and NegativeInfinity. double.IsNaN (with removing a few #pragmas and comments) is defined as: [Pure] [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] public static bool IsNaN(double d) { if (d != d) { return true; } else { return false; } } This is, by far, the most counterintuitive thing I have ever seen in the .NET framework. How is 0.0 / 0.0 represented "behind the scenes"? How can division by 0 be possible in double, and why does NaN != NaN?

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  • Issues with dynamically allocating a string array

    - by Jason Block
    Brand new to C. I am trying to dynamically allocate the array frags2 of size numberOfFrags and copy over the contents of the original array to it. I have tried numerous approaches and searching and do not understand what is going wrong here. Sizeof on the new array returns 0 instead of what I thought I malloc'd. Any help would be much appreciated! int main(int argc, const char* argv[]) { char* frags[MAX_FRAG_COUNT]; FILE* fp = fopen(argv[1], "r"); int numberOfFrags = ReadAllFragments(fp, frags, MAX_FRAG_COUNT); fclose(fp); char** frags2 = (char**)malloc(numberOfFrags * sizeof(char*)); for (int i = 0; i < numberOfFrags; i++) { frags2[i] = frags[i]; } qsort(frags2, sizeof(frags2) / sizeof(char *), sizeof(char*), cstring_cmp);

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  • Where should we manage session objects in an ASP.NET application?

    - by Kumar
    I am developing a 3-tired ASP.NET C# web application and was wondering where should the sessions be managed. I have a SessionManager class as follows: public sealed class SessionManager { private const string USER = "User"; private SessionManager() { } public static SessionManager Instance { get { return _instance; } } public User User { get { return HttpContext.Current.Session[USER] as User; } set { HttpContext.Current.Session[USER] = value; } } } Now should the session information be managed in the Business Logic Layer or should it be managed in the Presentation Layer?

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  • How can I declare constant strings for use in both an unmanaged C++ dll and in a C# application?

    - by Surfbutler
    Curently I'm passing my const string values up from my C++ into my C# at startup via a callback, but I'm wondering if there's a way of defining them in a C++ header file that I can then also refer to in C#. I already do this with enums as they are easy. I include a file in both my C++ library project (via a .h file with a pragma once at the top), and my C# application (as a link): #if _NET public #endif enum ETestData { First, Second }; I know it sounds messy, but it works :) But...how can I do the same with string constants - I'm initially thinking the syntax is too different between the platforms, but maybe there's a way? Using clever syntax involving #if _NET, #defines etc? Using resource files? Using a C++/CLI library? Any ideas?

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