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  • async_write/async_read problems while trying to implement question-answer logic

    - by Max
    Good day. I'm trying to implement a question - answer logic using boost::asio. On the Client I have: void Send_Message() { .... boost::asio::async_write(server_socket, boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Client::Handle_Write_Message, this, boost::asio::placeholders::error)); .... } void Handle_Write_Message(const boost::system::error_code& error) { .... std::cout << "Message was sent.\n"; .... boost::asio::async_read(server_socket_,boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Client::Handle_Read_Message, this, boost::asio::placeholders::error)); .... } void Handle_Read_Message(const boost::system::error_code& error) { .... std::cout << "I have a new message.\n"; .... } And on the Server i have the "same - logic" code: void Read_Message() { .... boost::asio::async_read(client_socket, boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Server::Handle_Read_Message, this, boost::asio::placeholders::error)); .... } void Handle_Read_Message(const boost::system::error_code& error) { .... std::cout << "I have a new message.\n"; .... boost::asio::async_write(client_socket_,boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Server::Handle_Write_Message, this, boost::asio::placeholders::error)); .... } void Handle_Write_Message(const boost::system::error_code& error) { .... std::cout << "Message was sent back.\n"; .... } Message it's just a structure. And the output on the Client is: Message was sent. Output on the Server is: I have a new message. And that's all. After this both programs are still working but nothing happens. I tried to implement code like: if (!error) { .... } else { // close sockets and etc. } But there are no errors in reading or writing. Both programs are just running normally, but doesn't interact with each other. This code is quite obvious but i can't understand why it's not working. Thanks in advance for any advice.

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  • Must parameter of assignment operator be reference?

    - by Tim
    When overloading assignment operator of a class in C++, must its parameter be reference? For example, class MyClass { public: ... MyClass & operator=(const MyClass &rhs); ... } Can it be class MyClass { public: ... MyClass & operator=(const MyClass rhs); ... } ? Thanks!

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  • c++ global operator not playing well with template class

    - by John
    ok, i found some similar posts on stackoverflow, but I couldn't find any that pertained to my exact situation and I was confused with some of the answers given. Ok, so here is my problem: I have a template matrix class as follows: template <typename T, size_t ROWS, size_t COLS> class Matrix { public: template<typename, size_t, size_t> friend class Matrix; Matrix( T init = T() ) : _matrix(ROWS, vector<T>(COLS, init)) { /*for( int i = 0; i < ROWS; i++ ) { _matrix[i] = new vector<T>( COLS, init ); }*/ } Matrix<T, ROWS, COLS> & operator+=( const T & value ) { for( vector<T>::size_type i = 0; i < this->_matrix.size(); i++ ) { for( vector<T>::size_type j = 0; j < this->_matrix[i].size(); j++ ) { this->_matrix[i][j] += value; } } return *this; } private: vector< vector<T> > _matrix; }; and I have the following global function template: template<typename T, size_t ROWS, size_t COLS> Matrix<T, ROWS, COLS> operator+( const Matrix<T, ROWS, COLS> & lhs, const Matrix<T, ROWS, COLS> & rhs ) { Matrix<T, ROWS, COLS> returnValue = lhs; return returnValue += lhs; } To me, this seems to be right. However, when I try to compile the code, I get the following error (thrown from the operator+ function): binary '+=' : no operator found which takes a right-hand operand of type 'const matrix::Matrix<T,ROWS,COLS>' (or there is no acceptable conversion) I can't figure out what to make of this. Any help if greatly appreciated!

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  • stxxl Assertion `it != root_node_.end()' failed

    - by Fabrizio Silvestri
    I am receiving this assertion failed error when trying to insert an element in a stxxl map. The entire assertion error is the following: resCache: /usr/include/stxxl/bits/containers/btree/btree.h:470: std::pair , bool stxxl::btree::btree::insert(const value_type&) [with KeyType = e_my_key, DataType = unsigned int, CompareType = comp_type, unsigned int RawNodeSize = 16384u, unsigned int RawLeafSize = 131072u, PDAllocStrategy = stxxl::SR, stxxl::btree::btree::value_type = std::pair]: Assertion `it != root_node_.end()' failed. Aborted Any idea? Edit: Here's the code fragment void request_handler::handle_request(my_key& query, reply& rep) { c_++; strip(query.content); std::cout << "Received query " << query.content << " by thread " << boost::this_thread::get_id() << ". It is number " << c_ << "\n"; strcpy(element.first.content, query.content); element.second = c_; testcache_.insert(element); STXXL_MSG("Records in map: " << testcache_.size()); } Edit2 here's more details (I omit constants, e.g. MAX_QUERY_LEN) struct comp_type : std::binary_function<my_key, my_key, bool> { bool operator () (const my_key & a, const my_key & b) const { return strncmp(a.content, b.content, MAX_QUERY_LEN) < 0; } static my_key max_value() { return max_key; } static my_key min_value() { return min_key; } }; typedef stxxl::map<my_key, my_data, comp_type> cacheType; cacheType testcache_; request_handler::request_handler() :testcache_(NODE_CACHE_SIZE, LEAF_CACHE_SIZE) { c_ = 0; memset(max_key.content, (std::numeric_limits<unsigned char>::max)(), MAX_QUERY_LEN); memset(min_key.content, (std::numeric_limits<unsigned char>::min)(), MAX_QUERY_LEN); testcache_.enable_prefetching(); STXXL_MSG("Records in map: " << testcache_.size()); }

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  • C++ segmentation error when first parameter is null in comparison operator overload

    - by user1774515
    I am writing a class called Word, that handles a c string and overloads the <, , <=, = operators. word.h: friend bool operator<(const Word &a, const Word &b); word.cc: bool operator<(const Word &a, const Word &b) { if(a == NULL && b == NULL) return false; if(a == NULL) return true; if(b == NULL) return false; return a.wd < b.wd; //wd is a valid c string } main: char* temp = NULL; //EDIT: i was mistaken, temp is a char pointer Word a("blah"); //a.wd = [b,l,a,h] cout << (temp<a); i get a segmentation error before the first line of the operator< method after the last line in the main. I can correct the problem by writing cout << (a>temp); where the operator> is similarly defined and i get no errors. but my assignment requires (temp < a) to work so this is where i ask for help. EDIT: i made a mistake the first time and i said temp was of type Word, but it is actually of type char*. so i assume that the compiler converts temp to a Word using one of my constructors. i dont know which one it would use and why this would work since the first parameter is not Word. here is the constructor i think is being used to make the Word using temp: Word::Word(char* c, char* delimeters=NULL) { char *temporary = "\0"; if(c == NULL) c = temporary; check(stoppers!=NULL, "(Word(char*,char*))NULL pointer"); //exits the program if the expression is false if(strlen(c) == 0) size = DEFAULT_SIZE; //10 else size = strlen(c) + 1 + DEFAULT_SIZE; wd = new char[size]; check(wd!=NULL, "Word(char*,char*))heap overflow"); delimiters = new char[strlen(stoppers) + 1]; //EDIT: changed to [] check(delimiters!=NULL,"Word(char*,char*))heap overflow"); strcpy(wd,c); strcpy(delimiters,stoppers); count = strlen(wd); } wd is of type char* thanks for looking at this big question and trying to help. let me know if you need more code to look at

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  • Can 'iterator' type just subclass 'const_iterator'?

    - by doublep
    After another question about iterators I'm having some doubts about custom containers. In my container, iterator is a subclass of const_iterator, so that I get conversion from non-const to const "for free". But is this allowed or are there any drawbacks or non-working scenarios for such a setup?

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  • How do I convert jstring to wchar_t *

    - by Obediah Stane
    Let's say that on the C++ side my function takes a variable of type jstring named myString. I can convert it to an ANSI string as follows: const char* ansiString = env-GetStringUTFChars(myString, 0); is there a way of getting const wchar_t* unicodeString = ...

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  • Problem with calculating floats

    - by iFloh
    strange situation, when performing the following lines of Code: const float a = 47.848711; const float b = 47.862952; float result = b - a; I get a (NSLog %.10f) result = 0.0142440796. I expected to get 0.0142410000. What's going on?

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  • C preprocessor: using #if inside #define?

    - by Wxy
    I want to write a macro that spits out code based on the boolean value of its parameter. So say DEF_CONST(true) should be expanded into "const", and DEF_CONST(false) should be expanded into nothing. Clearly the following doesn't work because we can't use another preprocessor inside #defines: #define DEF_CONST(b_const) \ #if (b_const) \ const \ #endif Any idea about how to do it?

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  • Can't insert a number into a C++ custom streambuf/ostream

    - by 0xbe5077ed
    I have written a custom std::basic_streambuf and std::basic_ostream because I want an output stream that I can get a JNI string from in a manner similar to how you can call std::ostringstream::str(). These classes are quite simple. namespace myns { class jni_utf16_streambuf : public std::basic_streambuf<char16_t> { JNIEnv * d_env; std::vector<char16_t> d_buf; virtual int_type overflow(int_type); public: jni_utf16_streambuf(JNIEnv *); jstring jstr() const; }; typedef std::basic_ostream<char16_t, std::char_traits<char16_t>> utf16_ostream; class jni_utf16_ostream : public utf16_ostream { jni_utf16_streambuf d_buf; public: jni_utf16_ostream(JNIEnv *); jstring jstr() const; }; // ... } // namespace myns In addition, I have made four overloads of operator<<, all in the same namespace: namespace myns { // ... utf16_ostream& operator<<(utf16_ostream&, jstring) throw(std::bad_cast); utf16_ostream& operator<<(utf16_ostream&, const char *); utf16_ostream& operator<<(utf16_ostream&, const jni_utf16_string_region&); jni_utf16_ostream& operator<<(jni_utf16_ostream&, jstring); // ... } // namespace myns The implementation of jni_utf16_streambuf::overflow(int_type) is trivial. It just doubles the buffer width, puts the requested character, and sets the base, put, and end pointers correctly. It is tested and I am quite sure it works. The jni_utf16_ostream works fine inserting unicode characters. For example, this works fine and results in the stream containing "hello, world": myns::jni_utf16_ostream o(env); o << u"hello, wor" << u'l' << u'd'; My problem is as soon as I try to insert an integer value, the stream's bad bit gets set, for example: myns::jni_utf16_ostream o(env); if (o.badbit()) throw "bad bit before"; // does not throw int32_t x(5); o << x; if (o.badbit()) throw "bad bit after"; // throws :( I don't understand why this is happening! Is there some other method on std::basic_streambuf I need to be implementing????

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  • String literals C++?

    - by Bad Man
    I need to do the following C# code in C++ (if possible). I have to const a long string with lots of freaking quotes and other stuff in it. const String _literal = @"I can use "quotes" inside here";

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  • Using operator+ without leaking memory?

    - by xokmzxoo
    So the code in question is this: const String String::operator+ (const String& rhs) { String tmp; tmp.Set(this->mString); tmp.Append(rhs.mString); return tmp; } This of course places the String on the stack and it gets removed and returns garbage. And placing it on the heap would leak memory. So how should I do this?

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  • duplicate symbol error C++

    - by iSight
    Hi, I have added some const character in my file as under. The error i get is duplicate symbol _xyz(say). What is the problem with it and how could i get out of this. const char* xyz = "xyz"; class Abc { public: Abc() { } };

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  • Return reference from class to this.

    - by Thomas
    Hi, I have the following member of class foo. foo &foo::bar() { return this; } But I am getting compiler errors. What stupid thing am I doing wrong? Compiler error (gcc): error: invalid initialization of non-const reference of type 'foo&' from a temporary of type 'foo* const'

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  • Generate set/get methods for a c++ class

    - by Narek
    Is there any tool that generates set and get methods for a class. Just I create classes very frequently and would like to have a tool which for each class-member wil generate following functions: Member_Type getMemberName() const; void setMemberName(const Member_Type & val);

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  • replacing a path with sed

    - by compie
    How can I use sed to replace this line char * path_list_[1] = { "/some/random/path" }; with this line char * path_list_[2] = { "lib/foo", "lib/bar" }; in a file named source.c Notes: * The path is really random. * Your solution should only change this line in source.c * I'm only interested in a sed oneliner. You can use this Python regex as a starting point: text = re.sub('static const char \* path_list_\[1\] = \{ "[^"]*" \};', 'static const char * path_list_[2] = { "lib/sun", "lib/matlab" };', text)

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  • How do I tell if the master volume is muted?

    - by John_Sheares
    I am using the following to mute/unmute the master audio on my computer. Now, I am looking for a way to determine the mute state. Is there a just as easy way to do this in C#? private const int APPCOMMAND_VOLUME_MUTE = 0x80000; private const int WM_APPCOMMAND = 0x319; [DllImport("user32.dll")] public static extern IntPtr SendMessageW(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);

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  • Move an object in the direction of a bezier curve?

    - by Sent1nel
    I have an object with which I would like to make follow a bezier curve and am a little lost right now as to how to make it do that based on time rather than the points that make up the curve. .::Current System::. Each object in my scene graph is made from position, rotation and scale vectors. These vectors are used to form their corresponding matrices: scale, rotation and translation. Which are then multiplied in that order to form the local transform matrix. A world transform (Usually the identity matrix) is then multiplied against the local matrix transform. class CObject { public: // Local transform functions Matrix4f GetLocalTransform() const; void SetPosition(const Vector3f& pos); void SetRotation(const Vector3f& rot); void SetScale(const Vector3f& scale); // Local transform Matrix4f m_local; Vector3f m_localPostion; Vector3f m_localRotation; // rotation in degrees (xrot, yrot, zrot) Vector3f m_localScale; } Matrix4f CObject::GetLocalTransform() { Matrix4f out(Matrix4f::IDENTITY); Matrix4f scale(), rotation(), translation(); scale.SetScale(m_localScale); rotation.SetRotationDegrees(m_localRotation); translation.SetTranslation(m_localTranslation); out = scale * rotation * translation; } The big question I have are 1) How do I orientate my object to face the tangent of the Bezier curve? 2) How do I move that object along the curve without just setting objects position to that of a point on the bezier cuve? Heres an overview of the function thus far void CNodeControllerPieceWise::AnimateNode(CObject* pSpatial, double deltaTime) { // Get object latest pos. Vector3f posDelta = pSpatial->GetWorldTransform().GetTranslation(); // Get postion on curve Vector3f pos = curve.GetPosition(m_t); // Get tangent of curve Vector3f tangent = curve.GetFirstDerivative(m_t); } Edit: sorry its not very clear. I've been working on this for ages and its making my brain turn to mush. I want the object to be attached to the curve and face the direction of the curve. As for movement, I want to object to follow the curve based on the time this way it creates smooth movement throughout the curve.

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  • Does the compiler optimize the function parameters passed by value?

    - by Naveen
    Lets say I have a function where the parameter is passed by value instead of const-reference. Further, lets assume that only the value is used inside the function i.e. the function doesn't try to modify it. In that case will the compiler will be able to figure out that it can pass the value by const-reference (for performance reasons) and generate the code accordingly? Is there any compiler which does that?

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  • Declare a Dictionary inside a static class

    - by Ngu Soon Hui
    How to declare a static dictionary object inside a static class? I tried public static class ErrorCode { public const IDictionary<string , string > ErrorCodeDic =new Dictionary<string, string>() { {"1","User name or password problem"} }; } But the compiler complains that "A const field of a reference type other than string can only be initialized with null".

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