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  • Returning objects with dynamic memory

    - by Caulibrot
    I'm having trouble figuring out a way to return an object (declared locally within the function) which has dynamic memory attached to it. The problem is the destructor, which runs and deletes the dynamic memory when the object goes out of scope, i.e. when I return it and want to use the data in the memory that has been deleted! I'm doing this for an overloaded addition operator. I'm trying to do something like: MyObj operator+( const MyObj& x, const MyObj& y ) { MyObj z; // code to add x and y and store in dynamic memory of z return z; } My destructor is simply: MyObj::~MyObj() { delete [] ptr; } Any suggestions would be much appreciated!

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  • C# equivalent of recv?

    - by mlh
    Hello, I have a portion of C code that I am trying to port over to C#. In my C code, I create a socket and then issue a receive command. The receive command is void receive(mysocket, char * command_buffer) { recv(mysocket, command_buffer, COMMAND_BUFFER_SIZE, 0); } now, the command buffer is returned with new values including command_buffer[8] being a pointer to a string. I'm really confused as to how to do this in C# because C# Read() command specifically takes in bytes and not char. The important part is that I get the pointer to the string. Any ideas?

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  • Writing a C++ wrapper for a C library

    - by stripes
    I have a legacy C library, written in an OO type form. Typical functions are like: LIB *lib_new(); void lib_free(LIB *lib); int lib_add_option(LIB *lib, int flags); void lib_change_name(LIB *lib, char *name); I'd like to use this library in my C++ program, so I'm thinking a C++ wrapper is required. The above would all seem to map to something like: class LIB { public: LIB(); ~LIB(); int add_option(int flags); void change_name(char *name); ... }; I've never written a C++ wrapper round C before, and can't find much advice about it. Is this a good/typical/sensible approach to creating a C++/C wrapper?

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  • C++ Declaring an uninitialized variable without a null constructor

    - by xbonez
    Consider the DUPoint class, whose declaration appears below. Assume this code appears in a file named DUPoint.h: #include <string> class DUPoint { public: DUPoint (int x, int y); int getX () const; int getY () const; void setX (int x); void setY (int y); void print(); private: int x_; int y_; }; Is it true that you cannot declare an uninitialized DUPoint variable with a statement such as DUPoint P; using this class as currently configured because it has no null constructor?

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  • Sending a file from memory (rather than disk) over HTTP using libcurl

    - by cinek1lol
    Hi! I would like to send pictures via a program written in C + +. - OK WinExec("C:\\curl\\curl.exe -H Expect: -F \"fileupload=@C:\\curl\\ok.jpg\" -F \"xml=yes\" -# \"http://www.imageshack.us/index.php\" -o data.txt -A \"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1\" -e \"http://www.imageshack.us\"", NULL); It works, but I would like to send the pictures from pre-loaded carrier to a variable char (you know what I mean? First off, I load the pictures into a variable and then send the variable), cause now I have to specify the path of the picture on a disk. I wanted to write this program in c++ by using the curl library, not through exe. extension. I have also found such a program (which has been modified by me a bit) #include <stdio.h> #include <string.h> #include <iostream> #include <curl/curl.h> #include <curl/types.h> #include <curl/easy.h> int main(int argc, char *argv[]) { CURL *curl; CURLcode res; struct curl_httppost *formpost=NULL; struct curl_httppost *lastptr=NULL; struct curl_slist *headerlist=NULL; static const char buf[] = "Expect:"; curl_global_init(CURL_GLOBAL_ALL); /* Fill in the file upload field */ curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "send", CURLFORM_FILE, "nowy.jpg", CURLFORM_END); curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "nowy.jpg", CURLFORM_COPYCONTENTS, "nowy.jpg", CURLFORM_END); curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "submit", CURLFORM_COPYCONTENTS, "send", CURLFORM_END); curl = curl_easy_init(); headerlist = curl_slist_append(headerlist, buf); if(curl) { curl_easy_setopt(curl, CURLOPT_URL, "http://www.imageshack.us/index.php"); if ( (argc == 2) && (!strcmp(argv[1], "xml=yes")) ) curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist); curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost); res = curl_easy_perform(curl); curl_easy_cleanup(curl); curl_formfree(formpost); curl_slist_free_all (headerlist); } system("pause"); return 0; }

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  • What's the simplest way of defining lexicographic comparison for elements of a class?

    - by the_mandrill
    If I have a class that I want to be able to sort (ie support a less-than concept), and it has several data items such that I need to do lexicographic ordering then I need something like this: struct MyData { string surname; string forename; bool operator<(const MyData& other) const { return surname < other.surname || (surname==other.surname && forename < other.forename); } }; This becomes pretty unmanageable for anything with more than 2 data members. Are there any simpler ways of achieving it? The data members may be any Comparable class.

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  • Change Wallpaper in windows mobile

    - by niks86
    Hello Friends, Hey im devloping application in that i want to set images as the wallpaper for that i written below code.when i used remote registry in registry value get updated but the wallpaper of the windows mobile does not changed.Can u plz tel me what i need to do. Here is my code. [DllImport("coredll.dll")] private static extern int SendMessage(IntPtr hWnd, uint msg, int wParam, int lParam); public const int HWND_BROADCAST = 0xffff; public const int WM_WININICHANGE = 0x001A; File.Copy(@"\My Documents\My Pictures\Album Sample_05.jpg", @"\My Documents\My Pictures\Album Sample_09.jpg", true); Registry.SetValue(@"HKEY_CURRENT_USER\Software\Microsoft\Today", "Wall", @"\My Documents\My Pictures\Album Sample_05.jpg"); SendMessage((IntPtr)HWND_BROADCAST, WM_WININICHANGE, 0xF2, 0); plz help me. Thanks.

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  • how to create multiple tcp connections between server and client

    - by lowcosthighperformance
    I am new in Unix/Linux networking programming, so I have written server-client program in below.In this code there is one socket between client and server, client requests to server, then server responses from 1 to 100 numbers to client. So my question is how can we do this process with 3 socket( tcp connection) without using thread? ( e.g. First socket runs then second runs then third runs then first again .. ) Do you have any suggestion? Thank you client.c int main() { int sock; struct sockaddr_in sa; int ret; char buf[1024]; int x; sock = socket (AF_INET, SOCK_STREAM, 0); bzero (&sa, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_port = htons(SERVER_PORT); inet_pton (AF_INET, SERVER_IP, &sa.sin_addr); ret = connect (sock, (const struct sockaddr *) &sa,sizeof (sa)); if (ret != 0) { printf ("connect failed\n"); exit (0); } x = 0; while (x != -1) { read (sock, buf , sizeof(int)); x = ntohl(*((int *)buf)); if (x != -1) printf ("int rcvd = %d\n", x); } close (sock); exit (0); } server.c int main() { int list_sock; int conn_sock; struct sockaddr_in sa, ca; socklen_t ca_len; char buf[1024]; int i; char ipaddrstr[IPSTRLEN]; list_sock = socket (AF_INET, SOCK_STREAM, 0); bzero (&sa, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_addr.s_addr = htonl(INADDR_ANY); sa.sin_port = htons(SERVER_PORT); bind (list_sock,(struct sockaddr *) &sa,sizeof(sa)); listen (list_sock, 5); while (1){ bzero (&ca, sizeof(ca)); ca_len = sizeof(ca); // important to initialize conn_sock = accept (list_sock,(struct sockaddr *) &ca,&ca_len); printf ("connection from: ip=%s port=%d \n",inet_ntop(AF_INET, &(ca.sin_addr), ipaddrstr, IPSTRLEN),ntohs(ca.sin_port)); for (i=0; i<100; ++i){ *((int *)buf) = htonl(i+20); // we using converting to network byte order write (conn_sock, buf, sizeof(int)); } * ((int *)buf) = htonl(-1); write (conn_sock, buf, sizeof(int)); close (conn_sock); printf ("server closed connection to client\n"); } }

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  • Loading Unmanaged C++ in C#. Error Attempted to read or write protected memory

    - by Thatoneguy
    I have a C++ function that looks like this __declspec(dllexport) int ___stdcall RegisterPerson(char const * const szName) { std::string copyName( szName ); // Assign name to a google protocol buffer object // Psuedo code follows.. Protobuf::Person person; person->set_name(copyName); // Error Occurs here... std::cerr << person->DebugString() << std::endl; } The corresponding C# code looks like this... [DllImport(@"MyLibrary.dll", SetLastError = true)] public static unsafe extern int RegisterPerson([MarshalAs(UnmanagedType.LPTStr)]string szName) Not sure why this is not working. My C++ library is compiled as Multi Threaded DLL with MultiByte encoding. Any help would be appreciated. I saw this is a common problem online but no answers lead me to a solution for my problem.

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  • Linker Error : Statically Linking of Boost Serialization Library

    - by Manikanda raj S
    I'm trying to link the Boost Serialization Library to my Code. But it doesn't seem to be working. g++ serialize.cpp -L"/usr/local/lib/libboost_serialization.a" Error : /tmp/ccw7eX4A.o: In function boost::archive::text_oarchive::text_oarchive(std::basic_ostream<char, std::char_traits<char> >&, unsigned int)': serializep.cpp:(.text._ZN5boost7archive13text_oarchiveC2ERSoj[_ZN5boost7archive13text_oarchiveC5ERSoj]+0x25): undefined reference toboost::archive::text_oarchive_impl::text_oarchive_impl(std::basic_ostream &, unsigned int)' .......... collect2: ld returned 1 exit status But when i link as a shared library, g++ serialize.cpp -lboost_serialization , it works fine. What am i missing here P.S : Other StackOverflow posts with the same question has no answers that work for the above error

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  • Sqlite insertion problem

    - by Devi
    Hi, I had sqlite database for my application I am able to retrieve values from my sqlite table and inserting values with no sql error but unable to find in sqlite table....please do needful help for this problem. I just stucked up at this point plz help me here is my code NSMutableString *registrationquery=[NSMutableString stringWithFormat:@"insert into tbl_kicks values ('%@','%@','%@')",[totalkicks text],[sessionstart text],[sessionstart text],@"0"]; //NSString *sqlNSString = [NSString stringWithFormat:@"INSERT INTO 'tbl_kicks' VALUES('%d','%@','%@');", // 4,sessionstart.text, appDelegate.note]; const char *sqlString = [registrationquery UTF8String]; char *sqlError; sqlite3_exec( appDelegate.database, sqlString, NULL, NULL, &sqlError );

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  • What is wrong with my version of strchr?

    - by Eduard Saakashvili
    My assignment is to write my own version of strchr, yet it doesn't seem to work. Any advice would be much appreciated. Here it is: char *strchr (const char *s, int c) //we are looking for c on the string s { int dog; //This is the index on the string, initialized as 0 dog = 0; int point; //this is the pointer to the location given by the index point = &s[dog]; while ((s[dog] != c) && (s[dog] != '\0')) { //it keeps adding to dog until it stumbles upon either c or '\0' dog++; } if (s[dog]==c) { return point; //at this point, if this value is equal to c it returns the pointer to that location } else { return NULL; //if not, this means that c is not on the string } }

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  • C++ how to store integer into a binary file??

    - by blaxc
    i gt a struct with 2 integer, i want to store them in a binary file and read it again... here is my code... struct pw { int a; int b; }; void main(){ pw* p = new pw(); pw* q = new pw(); std::ofstream fout(ADMIN_FILE, ios_base::out | ios_base::binary | ios_base::trunc); std::ifstream fin(ADMIN_FILE, ios_base::in | ios_base::binary); p->a=123; p->b=321; fout.write((const char*)p, sizeof(pw)); fin.write((char*)q, sizeof(pw)); fin.close(); cout<< q->a << endl;} my output is 0. anyone can tell me what is the problem?

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  • Different sizes of same strings - Telnet programming

    - by tommyogp
    Hi all, I have been trying to create an iphone app sending telnet command. However what puzzling me is that the sizes of certain strings are so much different, particularly when they include \n or \r. I listed out a few examples. Please assist. const char *a = "play 25\n"; int sizeBitA1 = sizeof(a); // 8 units int sizeBitA2 = sizeof("play 25\n"); // 9 units const char *b = "\r\n"; int sizeBitB1 = sizeof(b); // 8 units int sizeBitB2 = sizeof("\r\n"); // 3 units

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  • Problem with Initializing Consts

    - by UdiM
    This code, when compiled in xlC 8.0 (on AIX 6.1), produces the wrong result. It should print 12345, but instead prints 804399880. Removing the const in front of result makes the code work correctly. Where is the bug? #include <stdio.h> #include <stdlib.h> #include <string> long int foo(std::string input) { return strtol(input.c_str(), NULL, 0); } void bar() { const long int result = foo("12345"); printf("%u\n", result); } int main() { bar(); return 0; } Compilation command: /usr/vacpp/bin/xlC example.cpp -g

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  • How to split the definition of template friend funtion within template class?

    - by ~joke
    The following example compiles fine but I can't figure out how to separate declaration and definition of operator<<() is this particular case. Every time I try to split the definition friend is causing trouble and gcc complains the operator<<() definition must take exactly one argument. #include <iostream> template <typename T> class Test { public: Test(const T& value) : value_(value) {} template <typename STREAM> friend STREAM& operator<<(STREAM& os, const Test<T>& rhs) { os << rhs.value_; return os; } private: T value_; }; int main() { std::cout << Test<int>(5) << std::endl; }

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  • Debugging metaprograms [C++]

    - by atch
    Hi, Is there any way to check step by step what's going on in let's say template? I mean how it is instantiated step by step and so on? In book I've mentioned here , I found (2 minutes ago) quite interesting example of how binary could be implemented as a metafunction. template <unsigned long N> struct binary { static unsigned const value = binary<N/10>::value << 1 // prepend higher bits | N%10; // to lowest bit }; template <> // specialization struct binary<0> // terminates recursion { static unsigned const value = 0; }; and I think it could be quite useful to be able to see step by step what's been done during the instantiation of this template. Thanks for your replies.

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  • Getting MATLAB variable (string) from C

    - by Hamming
    Hi! I'm writing a small C application that launchs a Matlab script (.m file). I need to exchange some variables and I don't know how to get an array of chars that exists in Matlab. I'm doing something like this: enter code here result = engGetVariable(ep,"X"); if (!result) { printf ("Error..."); exit -1; } int n = mxGetN(result); char *varx = NULL; memcpy(varx, mxGetData(result),n*sizeof(char)); It doesn't work. Does someone know how to get a Matlab string in C? I've read Matlab documentation about engGetVariable() and the provided example but any of this things clarify me.

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  • How to access constant defined in child class from parent class functions?

    - by kavoir.com
    I saw this example from php.net: <?php class MyClass { const MY_CONST = "yonder"; public function __construct() { $c = get_class( $this ); echo $c::MY_CONST; } } class ChildClass extends MyClass { const MY_CONST = "bar"; } $x = new ChildClass(); // prints 'bar' $y = new MyClass(); // prints 'yonder' ?> But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot. Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?

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  • comlen function in Java

    - by davit-datuashvili
    in c or c++ the function comlen is defined such int comlen(char *p,char *q){ int i=0; while *p && (*p++==*q++) i++; return i; } Is this code equivalent of this function? int comlen(String s,String m){ int i=0; while (i<s.length() && s.charAt(i)==m.charAt(i)){ i++; } return i; }

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  • array of objects of a class

    - by anurag18294
    #include class test{ int a; char b; public: test() { cout<<"\n\nDefault constructor being called"; } test(int i,char j) { a=i; b=j; cout<<"\n\nConstructor with arguments called"; } }; int main() { test tarray[5]; test newobj(31,'z'); }; In the above code snippet can we intialize values to tarray[5].

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  • Encryption By Certificate

    - by user1817240
    I am encrypting customer name in database at database level. While saving in database only first letter of customer name is saved and hence while decrypting only first letter is retrieved. The following code shows the test sp. ALTER PROCEDURE [dbo].[spc_test_insert] ( @sFIRST_NAME typ_encryptedtext, ) AS BEGIN DECLARE @sSENCRYPTION_KEY char(15) DECLARE @sCERTIFICATE char(22) SET @sSENCRYPTION_KEY='SymmetricKey1' SET @sCERTIFICATE='CustomerCertificate' OPEN SYMMETRIC KEY SymmetricKey1 DECRYPTION BY CERTIFICATE CustomerCertificate; INSERT INTO test_table ( FIRST_NAME, ) Values ( -- Add the Params to be Added... EncryptByKey(Key_GUID(@sSENCRYPTION_KEY),@sFIRST_NAME), ) CLOSE SYMMETRIC KEY SymmetricKey1 END encryption decryption working fine in normal insert but its not working in stored procedure.

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  • Why use C typedefs rather than #defines?

    - by me_and
    What advantage (if any) is there to using typedef in place of #define in C code? As an example, is there any advantage to using typedef unsigned char UBYTE over #define UBYTE unsigned char when both can be used as void func() { UBYTE byte_value = 0; /* Do some stuff */ return byte_value; } Obviously the pre-processor will try to expand a #define wherever it sees one, which wouldn't happen with a typedef, but that doesn't seem to me to be any particular advantage or disadvantage; I can't think of a situation where either use wouldn't result in a build error if there was a problem.

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  • Getting the fractional part of a float without using modf()

    - by knight666
    Hi, I'm developing for a platform without a math library, so I need to build my own tools. My current way of getting the fraction is to convert the float to fixed point (multiply with (float)0xFFFF, cast to int), get only the lower part (mask with 0xFFFF) and convert it back to a float again. However, the imprecision is killing me. I'm using my Frac() and InvFrac() functions to draw an anti-aliased line. Using modf I get a perfectly smooth line. With my own method pixels start jumping around due to precision loss. This is my code: const float fp_amount = (float)(0xFFFF); const float fp_amount_inv = 1.f / fp_amount; inline float Frac(float a_X) { return ((int)(a_X * fp_amount) & 0xFFFF) * fp_amount_inv; } inline float Frac(float a_X) { return (0xFFFF - (int)(a_X * fp_amount) & 0xFFFF) * fp_amount_inv; } Thanks in advance!

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  • Set intersection of two strings

    - by user1785712
    import java.util.*; class set { public static void main(String args[]) { TreeSet<Character> t1 = new TreeSet<Character>(); TreeSet<Character> t2 = new TreeSet<Character>(); String s1 = "Ambitab bachan"; String s2 = "Ranjikanth"; for(char c1:s1.toCharArray()) t1.add(c1); for(char c2:s2.toCharArray()) t2.add(c2); t2.retainAll(t1); System.out.println(t2); } } this program find the common character in two different string. in this program Treeset is used to store the value and retainAll() method is used to find the common characters. can anybody help me reduce the line of coding.thanks in advance

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