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• What's the performance penalty of weak_ptr?

  - by Kornel Kisielewicz

  I'm currently designing a object structure for a game, and the most natural organization in my case became a tree. Being a great fan of smart pointers I use shared_ptr's exclusively. However, in this case, the children in the tree will need access to it's parent (example -- beings on map need to be able to access map data -- ergo the data of their parents. The direction of owning is of course that a map owns it's beings, so holds shared pointers to them. To access the map data from within a being we however need a pointer to the parent -- the smart pointer way is to use a reference, ergo a weak_ptr. However, I once read that locking a weak_ptr is a expensive operation -- maybe that's not true anymore -- but considering that the weak_ptr will be locked very often, I'm concerned that this design is doomed with poor performance. Hence the question: What is the performance penalty of locking a weak_ptr? How significant is it?

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• How to implement best matching logic in TSQL (SQL Server 2000)

  - by sanjay-kumar1911

  I have two tables X and Y: Table X C1 C2 C3 1 A 13 2 B 16 3 C 8 Table Y C1 C2 C3 C4 1 A 2 N 2 A 8 N 3 A 12 N 4 A 5 N 5 B 7 N 6 B 16 N 7 B 9 N 8 B 5 N 9 C 8 N 10 C 2 N 11 C 8 N 12 C 6 N Records in Table Y can be n number CREATE TABLE X(C1 INT, C2 CHAR(1), C3 INT); CREATE TABLE Y(C1 INT, C2 CHAR(1), C3 INT, C4 CHAR(1)); with following data: INSERT INTO X VALUES (1 'A',13 ); INSERT INTO X VALUES (2 'B',16 ); INSERT INTO X VALUES (3 'C',8 ); INSERT INTO Y VALUES (1,'A', 2,'N'); INSERT INTO Y VALUES (2,'A', 8,'N'); INSERT INTO Y VALUES (3,'A', 12,'N'); INSERT INTO Y VALUES (4,'A', 5,'N'); INSERT INTO Y VALUES (5,'B', 7,'N'); INSERT INTO Y VALUES (6,'B', 16,'N'); INSERT INTO Y VALUES (7,'B', 9,'N'); INSERT INTO Y VALUES (8,'B', 5,'N'); INSERT INTO Y VALUES (9,'C', 8,'N'); INSERT INTO Y VALUES (10,'C', 2,'N'); INSERT INTO Y VALUES (11,'C', 8,'N'); INSERT INTO Y VALUES (12,'C', 6,'N'); EXPECTED RESULT Table Y C1 C2 C3 C4 1 A 2 N 2 A 8 Y 3 A 12 N 4 A 5 Y 5 B 7 N 6 B 16 Y 7 B 9 N 8 B 5 N 9 C 8 Y 10 C 2 N 11 C 8 N 12 C 6 N How do I compare value of column C3 in Table X with all possible matches of column C3 of Table Y and to mark records as matched and unmatched in column C4 of Table Y? Possible matches for A (i.e. value of column C2 in Table X) would be (where R is row number i.e. value of column C1 in Table Y): R1, R2, R3, R4, R1+R2, R1+R3, R1+R4, R2+R3, R2+R4, R3+R4, R4+R5, R1+R2+R3, R1+R2+R4, R2+R3+R4, R1+R2+R3+R4

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• Primary reasons why programming language runtimes use stacks?

  - by manuel aldana

  Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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• Simple question about C++ constant syntax

  - by WilliamLou

  Here is some code copied from Thinking in C++ Vol1 Chapter 10. #include <iostream> using namespace std; int x = 100; class WithStatic { static int x; static int y; public: void print() const { cout << "WithStatic::x = " << x << endl; cout << "WithStatic::y = " << y << endl; } }; what's the meaning of const for the function print()? Thanks!

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• In Python, how to use a C++ function which returns an allocated array of structs via a ** parameter?

  - by Jon-Eric

  I'd like to use some existing C++ code, NvTriStrip, in a Python tool. SWIG easily handles the functions with simple parameters, but the main function, GenerateStrips, is much more complicated. What do I need to put in the SWIG interface file to indicate that primGroups is really an output parameter and that it must be cleaned up with delete[]? /////////////////////////////////////////////////////////////////////////// // GenerateStrips() // // in_indices: input index list, the indices you would use to render // in_numIndices: number of entries in in_indices // primGroups: array of optimized/stripified PrimitiveGroups // numGroups: number of groups returned // // Be sure to call delete[] on the returned primGroups to avoid leaking mem // bool GenerateStrips( const unsigned short* in_indices, const unsigned int in_numIndices, PrimitiveGroup** primGroups, unsigned short* numGroups, bool validateEnabled = false ); FYI, here is the PrimitiveGroup declaration: enum PrimType { PT_LIST, PT_STRIP, PT_FAN }; struct PrimitiveGroup { PrimType type; unsigned int numIndices; unsigned short* indices; PrimitiveGroup() : type(PT_STRIP), numIndices(0), indices(NULL) {} ~PrimitiveGroup() { if(indices) delete[] indices; indices = NULL; } };

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• What am I encrypting wrong here?

  - by Katie Krueger

  So I have a wordplay project to do and I have to encrypt some characters. I am at the point where I am stuck, and when I run it and type 1 for encrypt it doesn't shift that many letters. It just prints the work over again. I am wondering what I could do to fix it where if I say "hello" it will print 1 character over and say "ifmmp" Thank you! import java.util.Scanner; public class WordPlayTester{ public static void main(String [] args){ String word, reverse=""; String original; int key= 0; String Menu= "1-Encrypt \n2-Decrypt \n3-Is Palindrome \n0-Quit \n-Select an option-"; Scanner in = new Scanner(System.in); System.out.println("-Type any word-"); word = in.nextLine(); System.out.println(Menu); int choice=in.nextInt(); if(choice==1) { System.out.println("Insert a Key number"); int select= in.nextInt(); for (int i=0; i < word.length(); i++) { char c = word.charAt(i); if (c >= 'A' && c <= 'Z') { c = (char)(c - 64); int n = c+1; n = n % 26; if (n < 0) { n = n + 26; } c = (char)(n + 65); } System.out.println(c); } } else if(choice==3) { int length = word.length(); for ( int i = length - 1 ; i >= 0 ; i-- ) reverse = reverse + word.charAt(i); if (word.equals(reverse)) System.out.println("Your word is a palindrome."); else System.out.println("Your word is not a palindrome."); } else if(choice==0) { System.exit(0); } else { System.out.println(Menu); } } }

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• While making an RSS reader which saves articles, how can I prevent duplicates?

  - by Koning Baard

  Lets say I have a RSS feed which lists the 3 newest questions on SO. At 1 o'clock, the feed looks like this: While making an RSS reader which saves articles, how can I prevent duplicates? Convert char array to UNICODE in MFC C++ How to deploy a Java Swing application with an embedded JavaDB database? At 2 o'clock, this feed looks like: django url from another template than the one associated with the view-function While making an RSS reader which saves articles, how can I prevent duplicates? Convert char array to UNICODE in MFC C++ (duplicate articles are bold) I want to download the RSS feed every 5 minutes, parse it and save the articles that aren't already saved, but I do not want duplicates (items that remain in the new, updated feed like the examples above). What can I use to determine if an article is already saved? Thanks

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• "Ambiguous template specialization" problem

  - by Setien

  I'm currently porting a heap of code that has previously only been compiled with Visual Studio 2008. In this code, there's an arrangement like this: template <typename T> T convert( const char * s ) { // slow catch-all std::istringstream is( s ); T ret; is >> ret; return ret; } template <> inline int convert<int>( const char * s ) { return (int)atoi( s ); } Generally, there are a lot of specializations of the templated function with different return types that are invoked like this: int i = convert<int>( szInt ); The problem is, that these template specializations result in "Ambiguous template specialization". If it was something besides the return type that differentiated these function specializations, I could obviously just use overloads, but that's not an option. How do I solve this without having to change all the places the convert functions are called?

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• Sorting array of structs

  - by mrblippy

  Hi, i am having trouble making a method to sort an array of structs. i am tring to sort them in ascending order based on classcode. any help you could give would be appreciated struct unit { char classcode[4]; char *classname; }; void insertion_sort(struct unit u[], int n) { int j, p; struct unit tmp[1]; for(p = 1; p < n; p++) { tmp[0] = u[p]; for(j = p; j > 0 && (strcmp(tmp[j-1].classcode, tmp[p].classcode) > 0); j--) u[j] = u[j-1]; u[j] = tmp[0]; } }

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• MFC: Reading entire file to buffer...

  - by deostroll

  I've meddled with some code but I am unable to read the entire file properly...a lot of junk gets appended to the output. How do I fix this? // wmfParser.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include "wmfParser.h" #include <cstring> #ifdef _DEBUG #define new DEBUG_NEW #endif // The one and only application object CWinApp theApp; using namespace std; int _tmain(int argc, TCHAR* argv[], TCHAR* envp[]) { int nRetCode = 0; // initialize MFC and print and error on failure if (!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0)) { // TODO: change error code to suit your needs _tprintf(_T("Fatal Error: MFC initialization failed\n")); nRetCode = 1; } else { // TODO: code your application's behavior here. CFile file; CFileException exp; if( !file.Open( _T("c:\\sample.txt"), CFile::modeRead, &exp ) ){ exp.ReportError(); cout<<'\n'; cout<<"Aborting..."; system("pause"); return 0; } ULONGLONG dwLength = file.GetLength(); cout<<"Length of file to read = " << dwLength << '\n'; /* BYTE* buffer; buffer=(BYTE*)calloc(dwLength, sizeof(BYTE)); file.Read(buffer, 25); char* str = (char*)buffer; cout<<"length of string : " << strlen(str) << '\n'; cout<<"string from file: " << str << '\n'; */ char str[100]; file.Read(str, sizeof(str)); cout << "Data : " << str <<'\n'; file.Close(); cout<<"File was closed\n"; //AfxMessageBox(_T("This is a test message box")); system("pause"); } return nRetCode; }

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• How to implement square root and exponentiation on arbitrary length numbers?

  - by tomp

  I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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• boost.asio error on read from socket.

  - by niXman

  The following code of the client: typedef boost::array<char, 10> header_packet; header_packet header; boost::system::error_code error; ... /** send header */ boost::asio::write( _socket, boost::asio::buffer(header, header.size()), boost::asio::transfer_all(), error ); /** send body */ boost::asio::write( _socket, boost::asio::buffer(buffer, buffer.length()), boost::asio::transfer_all(), error ); of the server: struct header { boost::uint32_t header_length; boost::uint32_t id; boost::uint32_t body_length; }; static header unpack_header(const header_packet& data) { header hdr; sscanf(data.data(), "%02d%04d%04d", &hdr.header_length, &hdr.id, &hdr.body_length); return hdr; } void connection::start() { boost::asio::async_read( _socket, boost::asio::buffer(_header, _header.size()), boost::bind( &connection::read_header_handler, shared_from_this(), boost::asio::placeholders::error ) ); } /***************************************************************************/ void connection::read_header_handler(const boost::system::error_code& e) { if ( !e ) { std::cout << "readed header: " << _header.c_array() << std::endl; std::cout << constants::unpack_header(_header); boost::asio::async_read( _socket, boost::asio::buffer(_body, constants::unpack_header(_header).body_length), boost::bind( &connection::read_body_handler, shared_from_this(), boost::asio::placeholders::error ) ); } else { /** report error */ std::cout << "read header finished with error: " << e.message() << std::endl; } } /***************************************************************************/ void connection::read_body_handler(const boost::system::error_code& e) { if ( !e ) { std::cout << "readed body: " << _body.c_array() << std::endl; start(); } else { /** report error */ std::cout << "read body finished with error: " << e.message() << std::endl; } } On the server side the method read_header_handler() is called, but the method read_body_handler() is never called. Though the client has written down the data in a socket. The header is readed and decoded successfully. What's the error?

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• How would you go about tackling this problem? [SOLVED in C++]

  - by incrediman

  Intro: EDIT: See solution at the bottom of this question (c++) I have a programming contest coming up in about half a week, and I've been prepping :) I found a bunch of questions from this canadian competition, they're great practice: http://cemc.math.uwaterloo.ca/contests/computing/2009/stage2/day1.pdf I'm looking at problem B ("Dinner"). Any idea where to start? I can't really think of anything besides the naive approach (ie. trying all permutations) which would take too long to be a valid answer. Btw, the language there says c++ and pascal I think, but i don't care what language you use - I mean really all I want is a hint as to the direction I should proceed in, and perhpas a short explanation to go along with it. It feels like I'm missing something obvious... Of course extended speculation is more than welcome, but I just wanted to clarify that I'm not looking for a full solution here :) Short version of the question: You have a binary string N of length 1-100 (in the question they use H's and G's instead of one's and 0's). You must remove all of the digits from it, in the least number of steps possible. In each step you may remove any number of adjacent digits so long as they are the same. That is, in each step you can remove any number of adjacent G's, or any number of adjacent H's, but you can't remove H's and G's in one step. Example: HHHGHHGHH Solution to the example: 1. HHGGHH (remove middle Hs) 2. HHHH (remove middle Gs) 3. Done (remove Hs) -->Would return '3' as the answer. Note that there can also be a limit placed on how large adjacent groups have to be when you remove them. For example it might say '2', and then you can't remove single digits (you'd have to remove pairs or larger groups at a time). Solution I took Mark Harrison's main algorithm, and Paradigm's grouping idea and used them to create the solution below. You can try it out on the official test cases if you want. //B.cpp //include debug messages? #define DEBUG false #include <iostream> #include <stdio.h> #include <vector> using namespace std; #define FOR(i,n) for (int i=0;i<n;i++) #define FROM(i,s,n) for (int i=s;i<n;i++) #define H 'H' #define G 'G' class String{ public: int num; char type; String(){ type=H; num=0; } String(char type){ this->type=type; num=1; } }; //n is the number of bits originally in the line //k is the minimum number of people you can remove at a time //moves is the counter used to determine how many moves we've made so far int n, k, moves; int main(){ /*Input from File*/ scanf("%d %d",&n,&k); char * buffer = new char[200]; scanf("%s",buffer); /*Process input into a vector*/ //the 'line' is a vector of 'String's (essentially contigious groups of identical 'bits') vector<String> line; line.push_back(String()); FOR(i,n){ //if the last String is of the correct type, simply increment its count if (line.back().type==buffer[i]) line.back().num++; //if the last String is of the wrong type but has a 0 count, correct its type and set its count to 1 else if (line.back().num==0){ line.back().type=buffer[i]; line.back().num=1; } //otherwise this is the beginning of a new group, so create the new group at the back with the correct type, and a count of 1 else{ line.push_back(String(buffer[i])); } } /*Geedily remove groups until there are at most two groups left*/ moves=0; int I;//the position of the best group to remove int bestNum;//the size of the newly connected group the removal of group I will create while (line.size()>2){ /*START DEBUG*/ if (DEBUG){ cout<<"\n"<<moves<<"\n----\n"; FOR(i,line.size()) printf("%d %c \n",line[i].num,line[i].type); cout<<"----\n"; } /*END DEBUG*/ I=1; bestNum=-1; FROM(i,1,line.size()-1){ if (line[i-1].num+line[i+1].num>bestNum && line[i].num>=k){ bestNum=line[i-1].num+line[i+1].num; I=i; } } //remove the chosen group, thus merging the two adjacent groups line[I-1].num+=line[I+1].num; line.erase(line.begin()+I);line.erase(line.begin()+I); moves++; } /*START DEBUG*/ if (DEBUG){ cout<<"\n"<<moves<<"\n----\n"; FOR(i,line.size()) printf("%d %c \n",line[i].num,line[i].type); cout<<"----\n"; cout<<"\n\nFinal Answer: "; } /*END DEBUG*/ /*Attempt the removal of the last two groups, and output the final result*/ if (line.size()==2 && line[0].num>=k && line[1].num>=k) cout<<moves+2;//success else if (line.size()==1 && line[0].num>=k) cout<<moves+1;//success else cout<<-1;//not everyone could dine. /*START DEBUG*/ if (DEBUG){ cout<<" moves."; } /*END DEBUG*/ }

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• Perfect Forwarding to async lambda

  - by Alexander Kondratskiy

  I have a function template, where I want to do perfect forwarding into a lambda that I run on another thread. Here is a minimal test case which you can directly compile: #include <thread> #include <future> #include <utility> #include <iostream> #include <vector> /** * Function template that does perfect forwarding to a lambda inside an * async call (or at least tries to). I want both instantiations of the * function to work (one for lvalue references T&, and rvalue reference T&&). * However, I cannot get the code to compile when calling it with an lvalue. * See main() below. */ template <typename T> std::string accessValueAsync(T&& obj) { std::future<std::string> fut = std::async(std::launch::async, [](T&& vec) mutable { return vec[0]; }, std::forward<T>(obj)); return fut.get(); } int main(int argc, char const *argv[]) { std::vector<std::string> lvalue{"Testing"}; // calling with what I assume is an lvalue reference does NOT compile std::cout << accessValueAsync(lvalue) << std::endl; // calling with rvalue reference compiles std::cout << accessValueAsync(std::move(lvalue)) << std::endl; // I want both to compile. return 0; } For the non-compiling case, here is the last line of the error message which is intelligible: main.cpp|13 col 29| note: no known conversion for argument 1 from ‘std::vector<std::basic_string<char> >’ to ‘std::vector<std::basic_string<char> >&’ I have a feeling it may have something to do with how T&& is deduced, but I can't pinpoint the exact point of failure and fix it. Any suggestions? Thank you! EDIT: I am using gcc 4.7.0 just in case this could be a compiler issue (probably not)

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• C++ Undeclared Identifier (but it is declared?)

  - by Joshua

  I'm pretty sure I've included the qanda class, but when I try to declare a vector that contains it or a class of that type I get an error saying that qanda is undefined. Any idea what the problem might be? bot_manager_item.h #pragma once #include "../bot_packet/bot_packet.h" #include <vector> class bot_manager_item; #include "qanda.h" #include "bot_manager.h" class bot_manager_item { public: bot_manager_item(bot_manager* mngr, const char* name, const char* work_dir); ~bot_manager_item(); bool startup(); void cleanup(); void on_push_event(bot_exchange_format f); bool disable; private: void apply_changes(); bot_manager *_mngr; std::string _name; std::string _work_dir; std::string _message; std::string _message_copy; std::vector<qanda> games; qanda test; char _config_full_path[2600]; }; qanda.h #ifndef Q_AND_A #define Q_AND_A #include "users.h" #include "..\bot_packet\bot_packet.h" #include "bot_manager.h" #include <string> #include <algorithm> #include <map> #include <vector> #include <fstream> class qanda { public: qanda(bot_manager * manager, std::string name, std::string directory); ~qanda(){}; void room_message(std::string username, std::string user_message); void timer_tick(); private: // data members std::string question; std::string answer; std::string directory; std::string command_prefix; std::string name; Users users; std::map <std::string, std::string> questions_and_answers; int time_per_question; // seconds int time_between_questions; // seconds int timer; // milliseconds bool is_delayed; bool is_playing; bot_manager * manager; // functions void new_question(); void send_message(std::string msg); void announce_question(); void load_questions(); }; #endif

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• C++ - Opening a file inside a function using fopen

  - by Josh

  I am using Visual Studio 2005 (C++). I am passing a string into a function as a char array. I want to open the file passed in as a parameter and use it. I know my code works to an extent, because if I hardcode the filename as the first parameter it works perfectly. I do notice if I look at the value as a watch, the value includes the address aside the string literal. I have tried passing in the filename as a pointer, but it then complains about type conversion with __w64. As I said before it works fine with "filename.txt" in place of fileName. I am stumped. void read(char fileName[50],int destArray[MAX_R][MAX_C],int demSize[2]) { int rows=0; int cols=0; int row=0; int col=0; FILE * f = fopen(fileName,"r"); ...

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• grdb not working variables

  - by stupid_idiot

  hi, i know this is kinda retarded but I just can't figure it out. I'm debugging this: xor eax,eax mov ah,[var1] mov al,[var2] call addition stop: jmp stop var1: db 5 var2: db 6 addition: add ah,al ret the numbers that I find on addresses var1 and var2 are 0x0E and 0x07. I know it's not segmented, but that ain't reason for it to do such escapades, because the addition call works just fine. Could you please explain to me where is my mistake? I see the problem, dunno how to fix it yet though. The thing is, for some reason the instruction pointer starts at 0x100 and all the segment registers at 0x1628. To address the instruction the used combination is i guess [cs:ip] (one of the segment registers and the instruction pointer for sure). The offset to var1 is 0x10 (probably because from the begining of the code it's the 0x10th byte in order), i tried to examine the memory and what i got was: 1628:100 8 bytes 1628:108 8 bytes 1628:110 <- wtf? (assume another 8 bytes) 1628:118 ... whatever tricks are there in the memory [cs:var1] points somewhere else than in my code, which is probably where the label .data would usually address ds.... probably.. i don't know what is supposed to be at 1628:10 ok, i found out what caused the assness and wasted me whole fuckin day. the behaviour described above is just correct, the code is fully functional. what i didn't know is that grdb debugger for some reason sets the begining address to 0x100... the sollution is to insert the directive ORG 0x100 on the first line and that's the whole thing. the code was working because instruction pointer has the right address to first instruction and goes one by one, but your assembler doesn't know what effective address will be your program stored at so it pretty much remains relative to first line of the code which means all the variables (if not using label for data section) will remain pointing as if it started at 0x0. which of course wouldn't work with DOS. and grdb apparently emulates some DOS features... sry for the language, thx everyone for effort, hope this will spare someone's time if having the same problem... heheh.. at least now i know the reason why to use .data section :))))

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• How to return a string literal from a function

  - by skydoor

  Hi I am always confused about return a string literal or a string from a function. I was told that there might be memory leak because you don't know when the memory will be deleted? For example, in the code below, how to implement foo() so that make the output of the code is "Hello World"? void foo ( ) // you can add parameters here. { } int main () { char *c; foo ( ); printf ("%s",c); return 0; } Also if the return type of foo() is not void, but you can return char*, what should it be.

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• C++ Beginner - Best way to read 3 consecutive values from the command line?

  - by Francisco P.

  Hello everyone, I am writing a text-based Scrabble implementation for a college project. The specification states that the user's position input must be read from single line, like this: Coordinates of the word's first letter and orientation (<A – P> <1 – 15> <H ou V>): G 5 H G 5 H is the user's input for that particular example. The order, as shown, must be char int char. What is the best way to read the user's input? cin >> row >> column >> orientation will cause crashes if the user screws up. A getline and a subsequent string parser are a valid solution, but represent a bit of work. Is there another, better, way to do this, that I am missing? Thanks for your time!

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• Console class in java Exception in reading password

  - by satheesh

  Hi, i am trying to use Console class in java. with this code import java.io.Console; public class ConsoleClass { public static void main(String[] args){ Console c=System.console(); char[] pw; pw=c.readPassword("%s","pw :"); for(char ch:pw){ c.format("%c",ch); } c.format("\n"); MyUtility mu =new MyUtility(); while(true){ String name=c.readLine("%s", "input?: "); c.format("output: %s \n",mu.doStuff(name)); } } } class MyUtility{ String doStuff(String arg1){ return "result is " +arg1; } } here i am getting NullPointerException when i tried to run in netbeans but i am not getting any Exception when tried to run in cmd with out netbeans IDE.Why?

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• error in encryption program

  - by Raja

  #include<iostream> #include<math.h> #include<string> using namespace std; int gcd(int n,int m) { if(m<=n && n%m ==0) return m; if(n<m) return gcd(m,n); else return gcd(m,n%m); } int REncryptText(char m) { int p = 11, q = 3; int e = 3; int n = p * q; int phi = (p - 1) * (q - 1); int check1 = gcd(e, p - 1); int check2 = gcd(e, q - 1); int check3 = gcd(e, phi); // // Compute d such that ed = 1 (mod phi) //i.e. compute d = e-1 mod phi = 3-1 mod 20 //i.e. find a value for d such that phi divides (ed-1) //i.e. find d such that 20 divides 3d-1. //Simple testing (d = 1, 2, ...) gives d = 7 // double d = Math.Pow(e, -1) % phi; int d = 7; // public key = (n,e) // (33,3) //private key = (n,d) //(33 ,7) double g = pow(m,e); int ciphertext = g %n; // Now say we want to encrypt the message m = 7, c = me mod n = 73 mod 33 = 343 mod 33 = 13. Hence the ciphertext c = 13. //double decrypt = Math.Pow(ciphertext, d) % n; return ciphertext; } int main() { char plaintext[80],str[80]; cout<<" enter the text you want to encrpt"; cin.get(plaintext,79); int l =strlen(plaintext); for ( int i =0 ; i<l ; i++) { char s = plaintext[i]; str[i]=REncryptText(s); } for ( int i =0 ; i<l ; i++) { cout<<"the encryption of string"<<endl; cout<<str[i]; } return 0; }

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• iPhone/Objective-C struct question my own CGRectZero

  - by Mark

  I am designing a Padding struct as follows: /* Padding. */ struct CGPadding { CGFloat left; CGFloat top; CGFloat right; CGFloat bottom; }; typedef struct CGPadding CGPadding; CG_INLINE CGPadding CGPaddingMake(CGFloat left, CGFloat top, CGFloat right, CGFloat bottom) { CGPadding p; p.left = left; p.top = top; p.right = right; p.bottom = bottom; return p; } This all works perfectly well, the problem is how can I create a const CGPadding CGPaddingZero? If I do like this: const CGPadding CGPaddingZero = (CGPadding){0.0, 0.0, 0.0, 0.0}; It doesnt work. So what am I doing wrong?

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• Should I call class destructor in this code?

  - by peterg

  I am using this sample to decode/encode some data I am retrieving/sending from/to a web server, and I want to use it like this: BOOL HandleMessage(UINT uMsg,WPARAM wParam,LPARAM lParam,LRESULT* r) { if(uMsg == WM_DESTROY) { PostQuitMessage(0); return TRUE; } else if(uMsg == WM_CREATE) { // Start timer StartTimer(); return TRUE; } else if(uMsg == WM_TIMER) { //get data from server char * test = "test data"; Base64 base64; char *temp = base64.decode(test); MessageBox(TEXT(temp), 0, 0); } } The timer is set every 5 minutes. Should I use delete base64 at the end? Does delete deallocates everything used by base64?

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• [c++] upload image to imageshack

  - 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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• Dynamic allocated array is not freed

  - by Stefano

  I'm using the code above to dynamically allocate an array, do some work inside the function, return an element of the array and free the memory outside of the function. But when I try to deallocate the array it doesn't free the memory and I have a memory leak. The debugger pointed to the myArray variable shows me the error CXX0030. Why? struct MYSTRUCT { char *myvariable1; int myvariable2; char *myvariable2; .... }; void MyClass::MyFunction1() { MYSTRUCT *myArray= NULL; MYSTRUCT *myElement = this->MyFunction2(myArray); ... delete [] myArray; } MYSTRUCT* MyClass::MyFunction2(MYSTRUCT *array) { array = (MYSTRUCT*)operator new(bytesLength); ... return array[X]; }

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