Search Results

Search found 1848 results on 74 pages for 'printf'.

Page 40/74 | < Previous Page | 36 37 38 39 40 41 42 43 44 45 46 47  | Next Page >

• Help me sort programing languages a bit

  - by b-gen-jack-o-neill

  Hi, so I asked here few days ago about C# and its principles. Now, if I may, I have some additional general questions about some languages, becouse for novice like me, it seems a bit confusing. To be exact I want to ask more about language functions capabilities than syntax and so. To be honest, its just these special functions that bothers me and make me so confused. For exmaple, C has its printf(), Pascal has writeln() and so. I know in basic the output in assembler of these funtions would be similiar, every language has more or less its special functions. For console output, for file manipulation, etc. But all these functions are de-facto part of its OS API, so why is for example in C distinguished between C standard library functions and (on Windows) WinAPI functions when even printf() has to use some Windows feature, call some of its function to actually show desired text on console window, becouse the actuall "showing" is done by OS. Where is the line between language functions and system API? Now languages I dont quite understand - Python, Ruby and similiar. To be more specific, I know they are similiar to java and C# in term they are compiled into bytecode. But, I do not unerstand what are its capabilities in term of building GUI applications. I saw tutorial for using Ruby to program GUI applications on Linux and Windows. But isn´t that just some kind of upgrade? I mean fram other tutorials It seemed like these languages was first intended for small scripts than building big applications. I hope you understand why I am confused. If you do, please help me sort it out a bit, I have no one to ask.

  Read the article

• Static member function pointer to hold non static member function

  - by user1425406

  This has defeated me. I want to have a static class variable which is a pointer to a (non-static) member function. I've tried all sorts of ways, but with no luck (including using typedefs, which just seemed to give me a different set of errors). In the code below I have the static class function pointer funcptr, and I can call it successfully from outside the class, but not from within the member function CallFuncptr - which is what I want to do. Any suggestions? #include <stdio.h> class A { public: static int (A::*funcptr)(); int Four() { return 4;}; int CallFuncptr() { return (this->*funcptr)(); } // doesn't link - undefined reference to `A::funcptr' }; int (A::*funcptr)() = &A::Four; int main() { A fred; printf("four? %d\n", (fred.*funcptr)()); // This works printf("four? %d\n", fred.CallFuncptr()); // But this is the way I want to call it }

  Read the article

• what is the relation between SIGTSTP and SIGCHLD

  - by Rawhi

  I have tow handlers for each one of them (SIGTSTP, SIGCHLD), the thing is that when I pause a process using SIGTSTP the handler function of SIGCHLD run too. what should I do to prevent this . void ExeExternal(char *args[MAX_ARG], char* cmdString, LIST_ELEMENT** pList, int *Susp_Bg_Pid, int *susp) { int pID, status, w; switch (pID = fork()) { case -1: perror("smash error: >"); break; case 0: // Child Process setpgrp(); execv(args[0], args); execvp(args[0], args); perror("error"); exit(EXIT_FAILURE); break; default: if (cmdString[strlen(cmdString) - 1] != '&') { *Susp_Bg_Pid = pID; *susp = 1; while(*susp); } else { InsertElem(pList, args[0], getpid(), pID, 0); } break; } } signal handlers : void signalHandler(int signal) { int pid, cstatus; if (signal == SIGCHLD) { susp = 0; pid = waitpid(-1, &cstatus, WNOHANG); printf("[[child %d terminated]]\n", pid); DelPID(&JobsList, pid); } } void ctrlZsignal(int signal){ kill(Susp_Bg_Pid, SIGTSTP); susp = 0; printf("\nchild %d suspended\n", Susp_Bg_Pid); } Susp_Bg_Pid used to save the paused process id. susp indicates the state of the "smash" the parent process if it is suspended or not .

  Read the article

• how to write binary copy of structure array to file

  - by cerr

  I would like to write a binary image of a structure array to a binary file. I have tried this so far: #include <stdio.h> #include <string.h> #define NUM 256 const char *fname="binary.bin"; typedef struct foo_s { int intA; int intB; char string[20]; }foo_t; void main (void) { foo_t bar[NUM]; bar[0].intA = 10; bar[0].intB = 999; strcpy(bar[0].string,"Hello World!"); Save(bar); printf("%s written succesfully!\n",fname); } int Save(foo_t* pData) { FILE *pFile; int ptr = 0; int itr = 0; pFile = fopen(fname, "w"); if (pFile == NULL) { printf("couldn't open %s\n", fname); return; } for (itr = 0; itr<NUM; itr++) { for (ptr=0; ptr<sizeof(foo_t); ptr++) { fputc((unsigned char)*((&pData[itr])+ptr), pFile); } fclose(pFile); } } but the compiler is saying aggregate value used where an integer was expected fputc((unsigned char)*((&pData[itr])+ptr), pFile); and I don't quite understand why, what am I doing wrong? Thanks!

  Read the article

• Externally disabling signals for a Linux program.

  - by Harry

  Hello, On Linux, is it possible to somehow disable signaling for programs externally... that is, without modifying their source code? Context: I'm calling a C (and also a Java) program from within a bash script on Linux. I don't want any interruptions for my bash script, and for the other programs that the script launches (as foreground processes). While I can use a... trap '' INT ... in my bash script to disable the Ctrl C signal, this works only when the program control happens to be in the bash code. That is, if I press Ctrl C while the C program is running, the C program gets interrupted and it exits! This C program is doing some critical operation because of which I don't want it be interrupted. I don't have access to the source code of this C program, so signal handling inside the C program is out of question. #!/bin/bash trap 'echo You pressed Ctrl C' INT # A C program to emulate a real-world, long-running program, # which I don't want to be interrupted, and for which I # don't have the source code! # # File: y.c # To build: gcc -o y y.c # # #include <stdio.h> # int main(int argc, char *argv[]) { # printf("Performing a critical operation...\n"); # for(;;); // Do nothing forever. # printf("Performing a critical operation... done.\n"); # } ./y Regards, /HS

  Read the article

• Store a signed long int (32bit) as 4 octets?

  - by Doori Bar

  I managed to get a unsigned long int octets-representation (BE) by reading IPv4 methods, and I managed to read about how signed integers are using the MSB as the sign indicator, which makes 00 00 00 00 to be 0, while 7F FF FF FF is 2147483647. But I can't manage how to do the same for signed long integers? #include <stdio.h> #include <string.h> int main (void) { unsigned long int intu32; unsigned char octets[4]; intu32 = 255; octets[3] = (intu32) & 255; octets[2] = (intu32 >> 8) & 255; octets[1] = (intu32 >> 16) & 255; octets[0] = (intu32 >> 24) & 255; printf("(%d)(%d)(%d)(%d)\n", octets[0], octets[1], octets[2], octets[3]); intu32 = (octets[0] << 24) | (octets[1] << 16) | (octets[2] << 8) | octets[3]; printf("intu32:%lu\n", intu32); return 0; } Thanks in advance, Doori bar

  Read the article

• C: writing the following code into functions

  - by donok

  Dear respected programmers. Please could you help me (again) on how to put the following code into functions for my program. I have read on-line and understand how functions work but when I do it myself it all goes pear shaped/wrong(I am such a noob). Please could you help with how to for example to write the code below into functions.(like opening the input file). My attempt: void outputFile(int argc, char **argv) { /* Check that the output file doesnt exist */ if (stat(argv[argc-1], &inode) != -1) { printf("Warning: The file %s already exists. Not going to overwrite\n", argv[argc-1]); return -1; } /*Opening ouput files*/ file_desc_out = open(argv[i],O_CREAT | O_WRONLY | O_EXCL , S_IRUSR|S_IWUSR); if(file_desc_out == -1) { printf("Error: %s cannot be opened. \n",argv[i]); //insted of argv[2] have pointer i. return -1; } } Any help on how I would now reference to this in my program is appreciated thank you. I tried: ouputfile(but I cant figure out what goes here and why either).

  Read the article

• Assigning a value to an integer in a C linked list

  - by Drunk On Java

  Hello all. I have a question regarding linked lists. I have the following structs and function for example. struct node { int value; struct node *next; }; struct entrynode { struct node *first; struct node *last; int length; }; void addnode(struct entrynode *entry) { struct node *nextnode = (struct node *)malloc(sizeof(struct node)); int temp; if(entry->first == NULL) { printf("Please enter an integer.\n"); scanf("%d", &temp); nextnode->value = temp; nextnode->next = NULL; entry->first = nextnode; entry->last = nextnode; entry->length++; } else { entry->last->next = nextnode; printf("Please enter an integer.\n"); scanf("%d", nextnode->value); nextnode->next = NULL; entry->last = nextnode; entry->length++; } } In the first part of the if statement, I store input into a temp variable and then assign that to a field in the struct. The else branch, I tried to assign it directly which did not work. How would I go about assigning it directly? Thanks for your time.

  Read the article

• SFINAE and detecting if a C++ function object returns void.

  - by Tom Swirly

  I've read the various authorities on this, include Dewhurst and yet haven't managed to get anywhere with this seemingly simple question. What I want to do is to call a C++ function object, (basically, anything you can call, a pure function or a class with ()), and return its value, if that is not void, or "true" otherwise. #include <stdio.h> struct Foo { void operator()() {} }; struct Bar { bool operator()() { return false; } }; Foo foo; Bar bar; bool baz() { return false; } void bang() {} const char* print(bool b) { printf(b ? "true, " : "false, "); } template <typename Functor> bool magicCallFunction(Functor f) { return true; // lots of template magic occurs here... } int main(int argc, char** argv) { print(magicCallFunction(foo)); print(magicCallFunction(bar)); print(magicCallFunction(baz)); print(magicCallFunction(bang)); printf("\n"); }

  Read the article

• Sparc Assembly Call currupts data

  - by Sigge

  I am at the moment working with some assembler code for the Sparc processor family, and i am having some truble with a piece of code.. I think the code and output explains more, but in the short.. When i do a call to the function println my varaibels that i have written to the %fp - 8 memory location is destoryed.. here is my assembler code that i am trying to run !PROCEDURE main .section ".text" .global main .align 4 main: save %sp, -96, %sp L1: set 96, %l0 mov %l0, %o0 call initObject ; nop mov %o0, %l0 mov %l0, %o0 call Test$go ; nop mov %o0, %l0 mov %l0, %o0 call println ; nop L0: ret restore !END main !PROCEDURE Test$go .section ".text" .global Test$go .align 4 Test$go: save %sp, -96, %sp L3: mov %i0, %l0 set 0, %l0 set -8, %l1 add %fp,%l1, %l1 st %l0, [%l1] set 1, %l0 mov %l0, %o0 call println ; nop set -8, %l0 add %fp,%l0, %l0 ld [%l0], %l0 mov %l0, %o0 call println ; nop set 1, %l0 mov %l0, %i0 L2: ret restore !END Test$go Here is the assembler code for the println code .global println .type println,#function println: save %sp,-96,%sp ! block 1 .L193: ! File runtime.c: ! 42 } ! 43 ! 45 /** ! 46 Prints an integer to the standard output stream. ! 47 ! 48 @param i The integer to be printed. ! 49 */ ! 50 void println(int i) { ! 51 printf("%d\n", i); sethi %hi(.L195),%o0 or %o0,%lo(.L195),%o0 call printf mov %i0,%o1 jmp %i7+8 restore This is the out put i get when i run this piece of assembler code 1 67584 1 As u can see, the data that is located at %fp - 8 has been destroyed.. please all feedback is apritiated

  Read the article

• How do I read hex numbers into an unsigned int in C [Solved]

  - by sil3nt

  I'm wanting to read hex numbers from a text file into an unsigned integer so that I can execute Machine instructions. It's just a simulation type thing that looks inside the text file and according to the values and its corresponding instruction outputs the new values in the registers. For example, the instructions would be: 1RXY - Save register R with value in memory address XY 2RXY - Save register R with value XY BRXY - Jump to register R if xy is this and that etc.. ARXY - AND register R with value at memory address XY The text file contains something like this each in a new line. (in hexidecimal) 120F B007 290B My problem is copying each individual instruction into an unsigned integer...how do I do this? #include <stdio.h> int main(){ FILE *f; unsigned int num[80]; f=fopen("values.txt","r"); if (f==NULL){ printf("file doesnt exist?!"); } int i=0; while (fscanf(f,"%x",num[i]) != EOF){ fscanf(f,"%x",num[i]); i++; } fclose(f); printf("%x",num[0]); }

  Read the article

• Beginner error in CUDA

  - by Dimitri

  Hi folks, first all i want to wish you a merry christmas. I am writing a small program in CUDA and i have the following errors : contraste.cu(167): error: calling a host function from a __device__/__global__ function is not allowed I don't understand why. Can you please help me and show me my errors. It seems that my program is correct. Here is a the bunch of code causing the problems : __global__ void kernel_contraste(float power, unsigned char tab_in[], unsigned char tab_out[], int nbl, int nbc) { int x = threadIdx.x; printf("I am the thread %d\n", x); } Part of my main program : unsigned char *dimg, *dimg_res; ..... cudaMalloc((void **)dimg, h * w * sizeof(char)); cudaMemcpy(dimg, r.data, h*w*sizeof(char), cudaMemcpyHostToDevice); cudaMalloc((void **)dimg_res, h*w*sizeof(char)); dim3 nbThreadparBloc(256); dim3 numblocs(1); kernel_contraste<<<numblocs, nbThreadparBloc >>>(puissance, dimg, dimg_res, h, w); cudaThreadSynchronize(); ..... cudaFree(dimg); cudaFree(dimg_res); The line 167 is the line where i call the printf in function kernel_contraste. For information, this program takes an image as an input( a sun Rasterfile ) and a power then it calculates the contraste of that image. Thanks !!

  Read the article

• Sparc Assembly Call corrupts data

  - by Sigge

  I am at the moment working with some assembler code for the Sparc processor family, and i am having some truble with a piece of code.. I think the code and output explains more, but in the short.. When i do a call to the function println my varaibels that i have written to the %fp - 8 memory location is destoryed.. here is my assembler code that i am trying to run !PROCEDURE main .section ".text" .global main .align 4 main: save %sp, -96, %sp L1: set 96, %l0 mov %l0, %o0 call initObject ; nop mov %o0, %l0 mov %l0, %o0 call Test$go ; nop mov %o0, %l0 mov %l0, %o0 call println ; nop L0: ret restore !END main !PROCEDURE Test$go .section ".text" .global Test$go .align 4 Test$go: save %sp, -96, %sp L3: mov %i0, %l0 set 0, %l0 set -8, %l1 add %fp,%l1, %l1 st %l0, [%l1] set 1, %l0 mov %l0, %o0 call println ; nop set -8, %l0 add %fp,%l0, %l0 ld [%l0], %l0 mov %l0, %o0 call println ; nop set 1, %l0 mov %l0, %i0 L2: ret restore !END Test$go Here is the assembler code for the println code .global println .type println,#function println: save %sp,-96,%sp ! block 1 .L193: ! File runtime.c: ! 42 } ! 43 ! 45 /** ! 46 Prints an integer to the standard output stream. ! 47 ! 48 @param i The integer to be printed. ! 49 */ ! 50 void println(int i) { ! 51 printf("%d\n", i); sethi %hi(.L195),%o0 or %o0,%lo(.L195),%o0 call printf mov %i0,%o1 jmp %i7+8 restore This is the out put i get when i run this piece of assembler code 1 67584 1 As u can see, the data that is located at %fp - 8 has been destroyed.. please all feedback is apritiated

  Read the article

• Can a member struct be zero-init from the constructor initializer list without calling memset?

  - by selbie

  Let's say I have the following structure declaration (simple struct with no constructor). struct Foo { int x; int y; int z; char szData[DATA_SIZE]; }; Now let's say this struct is a member of a C++ class as follows: class CFoobar { Foo _foo; public: CFoobar(); }; If I declare CFoobar's constructor as follows: CFoobar::CFoobar() { printf("_foo = {%d, %d, %d}\n", _foo.x, _foo.y,_foo.z); for (int x = 0; x < 100; x++) printf("%d\n", _foo.szData[x]); } As you would expect, when CFoobar's constructor runs, garbage data gets printed out Obviously, the easy fix is to memset or ZeroMemory &_foo. It's what I've always done... However, I did notice that if add _foo to the constructor's initialization list with no parameters as follows: CFoobar::CFoobar() : _foo() { That this appears to zero-out the member variables of _foo. At least that was the case with g++ on linux. Now here's my question: Is this standard C++, or is this compiler specific behavior? If it's standard behavior, can someone quote me a reference from an official source? Any "gotchas" in regards to implicit zero-init behavior with more complicated structs and classes?

  Read the article

• How to know the type of an object in a list?

  - by nacho4d

  Hi, I want to know the type of object (or type) I have in my list so I wrote this: void **list; //list of references list = new void * [2]; Foo foo = Foo(); const char *not_table [] = {"tf", "ft", 0 }; list[0] = &foo; list[1] = not_table; if (dynamic_cast<LogicProcessor*>(list[0])) { //ERROR here ;( printf("Foo was found\n"); } if (dynamic_cast<char*> (list[0])) { //ERROR here ;( printf("char was found\n"); } but I get : error: cannot dynamic_cast '* list' (of type 'void*') to type 'class Foo*' (source is not a pointer to class) error: cannot dynamic_cast '* list' (of type 'void*') to type 'char*' (target is not pointer or reference to class) Why is this? what I am doing wrong here? Is dynamic_cast what I should use here? Thanks in advance EDIT: I know above code is much like plain C and surely sucks from the C++ point of view but is just I have the following situation and I was trying something before really implementing it: I have two arrays of length n but both arrays will never have an object at the same index. Hence, or I have array1[i]!=NULL or array2[i]!=NULL. This is obviously a waste of memory so I thought everything would be solved if I could have both kind of objects in a single array of length n. I am looking something like Cocoa's (Objective-C) NSArray where you don't care about the type of the object to be put in. Not knowing the type of the object is not a problem since you can use other method to get the class of a certain later. Is there something like it in c++ (preferably not third party C++ libraries) ? Thanks in advance ;)

  Read the article

• C read X bytes from a file, padding if needed

  - by Hunter McMillen

  I am trying to read in an input file 64 bits at a time, then do some calculations on those 64 bits, the problem is I need to convert the ascii text to hexadecimal characters. I have searched around but none of the answers posted seem to work for my situation. Here is what I have: int main(int argc, int * argv) { char buffer[9]; FILE *f; unsigned long long test; if(f = fopen("input2.txt", "r")) { while( fread(buffer, 8, 1, f) != 0) //while not EOF read 8 bytes at a time { buffer[8] = '\0'; test = strtoull(buffer, NULL, 16); //interpret as hex printf("%llu\n", test); printf("%s\n", buffer); } fclose(f); } } For an input like this: "testing string to hex conversion" I get results like this: 0 testing 0 string t 0 o hex co 0 nversion Where I would expect: 74 65 73 74 69 6e 67 20 <- "testing" in hex testing 73 74 72 69 6e 67 20 74 <- "string t" in hex string t 6f 20 68 65 78 20 63 6f <- "o hex co" in hex o hex co 6e 76 65 72 73 69 6f 6e <- "nversion" in hex nversion Can anyone see where I misstepped?

  Read the article

• Receiving "expected expression before" Error When Using A Struct

  - by Zach Dziura

  I'm in the process of creating a simple 2D game engine in C with a group of friends at school. I'd like to write this engine in an Object-Oriented way, using structs as classes, function pointers as methods, etc. To emulate standard OOP syntax, I created a create() function which allocates space in memory for the object. I'm in the process of testing it out, and I'm receiving an error. Here is my code for two files that I'm using to test: test.c: #include <stdio.h> int main() { typedef struct { int i; } Class; Class *test = (Class*) create(Class); test->i = 1; printf("The value of \"test\" is: %i\n", test->i); return 0; } utils.c: #include <stdio.h> #include <stdlib.h> #include "utils.h" void* create(const void* class) { void *obj = (void*) malloc(sizeof(class)); if (obj == 0) { printf("Error allocating memory.\n"); return (int*) -1; } else { return obj; } } void destroy(void* object) { free(object); } The utils.h file simply holds prototypes for the create() and destroy() functions. When I execute gcc test.c utils.c -o test, I'm receiving this error message: test.c: In function 'main': test.c:10:32: error: expected expression before 'Class' I know it has something to do with my typedef at the beginning, and how I'm probably not using proper syntax. But I have no idea what that proper syntax is. Can anyone help?

  Read the article

• expected identifier or '(' before '{' token in Flex

  - by user1829177

  I am trying to use Flex to parse 'C' source code. Unfortunately I am getting the error "expected identifier or '(' before '{' token" on lines 1,12,13,14... . Any ideas why? %{ %} digit [0-9] letter [a-zA-Z] number (digit)+ id (letter|_)(letter|digit|_)* integer (int) character (char) comma [,] %% {integer} {return INT;} {character} {return CHAR;} {number} {return NUM;} {id} {return IDENTIFIER;} {comma} {return ',';} [-+*/] {return *yytext;} . {} %% main() { yylex(); } The corresponding flex file is as shown below: %{ #include <ctype.h> #include <stdio.h> #include "myhead.h" #include "mini.l" #define YYSTYPE double # undef fprintf %} %token INT %token CHAR %token IDENTIFIER %token NUM %token ',' %left '+' '-' %left '*' '/' %right UMINUS %% lines:lines expr '\n' {printf("%g\n",$2);} |lines '\n' |D | ; expr :expr '*' expr {$$=$1*$3;} |expr '/' expr {$$=$1/$3;} |expr '+' expr {$$=$1+$3;} |expr '-' expr {$$=$1+$3;} |'(' expr ')' {$$=$2;} |'-' expr %prec UMINUS {$$=-$2;} |IDENTIFIER {} |NUM {} ; T :INT {} |CHAR {} ; L :L ',' IDENTIFIER {} |IDENTIFIER {} ; D :T L {printf("T is %g, L is %g",$1,$2);} ; %% /*void yyerror (char *s) { fprintf (stderr, "%s\n", s); } */ I am compiling the generated code using the command: gcc my_file.c -ly

  Read the article

• int array doesnt get char values

  - by user1780004

  I am absolutely brand new at programming and im not sure how to explain what im doing here. The whole purpose of this piece is to enter values and then print them out in the same order. Now I wanna quit from entering values when pressing 'q' and so I have to scanf for chars but when I assign them back to the int array the values are not the same. Hope that makes any sense to you but in any case heres my code: #include <stdio.h> #include <stdlib.h> #define SIZE 5000 define flush fflush(stdin) main() { int input[SIZE] = {0},i = 0; int counter = 0; char inputs, quit; do { system("cls"); printf("Input number ('q' to quit and display numbers entered): "); flush; scanf("%c",&inputs); flush; if (inputs == 'q') quit = 'q'; else { input[i] = inputs; counter++; i++; } } while (i < SIZE && quit != 'q'); for(i = 0; i < counter; i++){ printf("%i.%i\n", i + 1, input[i]); } system("pause"); } Ive been trying to do this on my own btw and also researched some information online regarding chars but couldnt find anything that would help me. Thanks a lot in advance.

  Read the article

• 3x3 array = 10 numbers

  - by user1708505

  i have this code #include <math.h> #include <stdio.h> const int n = 3; const int s = 3; int getm(int mat[n][s]); int printm(int mat[n][s]); int main() { int m[n][s]; getm(m); printm(m); return 0; } int getm(int mat[n][s]) { for(int x = 0;x < n;x++) { for (int y = 0;y<s;y++) { scanf("%i ", &mat[x][y]); } } return 0; } int printm(int mat[n][s]) { for(int x = 0;x<n;x++) { for(int y = 0;y<s;y++) { printf("%i ", mat[x][y]); if(y==(s-1)) { printf("\n"); } } } } which shoud ask for 9 numbers to make a 3x3 matrix array, but it actually asks for 10 numbers, printm is working well - printing only 9 numbers. Where is error?

  Read the article

• Template specialization to use default type if class member typedef does not exist

  - by Frank

  Hi Everyone, I'm trying to write code that uses a member typedef of a template argument, but want to supply a default type if the template argument does not have that typedef. A simplified example I've tried is this: struct DefaultType { DefaultType() { printf("Default "); } }; struct NonDefaultType { NonDefaultType() { printf("NonDefault "); } }; struct A {}; struct B { typedef NonDefaultType Type; }; template<typename T, typename Enable = void> struct Get_Type { typedef DefaultType Type; }; template<typename T> struct Get_Type< T, typename T::Type > { typedef typename T::Type Type; }; int main() { Get_Type::Type test1; Get_Type::Type test2; } I would expect this to print "Default NonDefault", but instead it prints "Default Default". My expectation is that the second line in main() should match the specialized version of Get_Type, because B::Type exists. However, this does not happen. Can anyone explain what's going on here and how to fix it, or another way to accomplish the same goal? Thank you.

  Read the article

• C++ unrestricted union workaround

  - by Chris

  #include <stdio.h> struct B { int x,y; }; struct A : public B { // This whines about "copy assignment operator not allowed in union" //A& operator =(const A& a) { printf("A=A should do the exact same thing as A=B\n"); } A& operator =(const B& b) { printf("A = B\n"); } }; union U { A a; B b; }; int main(int argc, const char* argv[]) { U u1, u2; u1.a = u2.b; // You can do this and it calls the operator = u1.a = (B)u2.a; // This works too u1.a = u2.a; // This calls the default assignment operator >:@ } Is there any workaround to be able to do that last line u1.a = u2.a with the exact same syntax, but have it call the operator = (don't care if it's =(B&) or =(A&)) instead of just copying data? Or are unrestricted unions (not supported even in Visual Studio 2010) the only option?

  Read the article

• C related, store a signed long int (32bit) as 4 octets?

  - by Doori Bar

  I managed to get a unsigned long int octets-representation (BE) by reading IPv4 methods, and I managed to read about how signed integers are using the MSB as the sign indicator, which makes 00 00 00 00 to be 0, while 7F FF FF FF is 2147483647. But I can't manage how to do the same for signed long integers? #include <stdio.h> #include <string.h> int main (void) { unsigned long int intu32; unsigned char octets[4]; intu32 = 255; octets[3] = (intu32) & 255; octets[2] = (intu32 >> 8) & 255; octets[1] = (intu32 >> 16) & 255; octets[0] = (intu32 >> 24) & 255; printf("(%d)(%d)(%d)(%d)\n", octets[0], octets[1], octets[2], octets[3]); intu32 = (octets[0] << 24) | (octets[1] << 16) | (octets[2] << 8) | octets[3]; printf("intu32:%lu\n", intu32); return 0; } Thanks in advance, Doori bar

  Read the article

• C socket and openssl (RSA)

  - by giozh

  there's something strange in my client/server socket using RSA. If i test it on localhost, everithing goes fine, but if i put client on a pc and server on othe pc, something gone wrong. Client after call connect, call a method for public keys exchange with server. This part of code works fine. After this, client send a request to server: strcpy(send_pack->op, "help\n"); RSA_public_encrypt(strlen(send_pack->op), send_pack->op, encrypted_send->op, rsa_server, padding); rw_value = write(server, encrypted_send, sizeof (encrypted_pack)); if (rw_value == -1) { stampa_errore(write_error); close(server); exit(1); } if (rw_value == 0) { stampa_errore(no_response); close(server); exit(1); } printf("---Help send, waiting for response\n"); set_alarm(); rw_value = read(server, encrypted_receive, sizeof (encrypted_pack)); alarm(0); if (rw_value == -1) { stampa_errore(read_error); exit(1); } if (rw_value == 0) { stampa_errore(no_response); close(server); exit(1); } RSA_private_decrypt(RSA_size(rsa), encrypted_receive->message, receive_pack->message, rsa, padding); printf("%s\n", receive_pack->message); return; } but when server try to decrypt the receive message on server side, the "help" string doesn't appear. This happen only on the net, on localhost the same code works fine... EDIT: typedef struct pack1 { unsigned char user[encrypted_size]; unsigned char password[encrypted_size]; unsigned char op[encrypted_size]; unsigned char obj[encrypted_size]; unsigned char message[encrypted_size]; int id; }encrypted_pack; encrypted_size is 512, and padding used is RSA_PKCS1_PADDING

  Read the article

• Reading/Writing/Modifying a struct in C

  - by user1016401

  I am taking some information from a user (name, address, contact number) and store it in a struct. I then store this in a file which is opened in "r+" mode. I try reading it line by line and see if the entry I am trying to enter already exists, in which case I exit. Otherwise I append this entry at the end of the file. The problem is that when I open the file in "r+" mode, it gives me Segmentation fault! Here is the code: struct cust{ char *frstnam; char *lastnam; char *cntact; char *add; }; Now consider this function. I am passing a struct of information in this function. Its job is to check if this struct already exists else append it to end of file. void check(struct cust c) { struct cust cpy; FILE *f; f=fopen("Customer.txt","r+"); int num=0; if (f!= NULL){ while (!feof(f)) { num++; fread(&cpy,sizeof(struct cust),1,f); if ((cpy.frstnam==c.frstnam)&(cpy.lastnam==c.lastnam)&(cpy.cntact==c.cntact)&(cpy.add==c.add)) { printf("Hi %s %s. Nice to meet you again. You live at %s and your contact number is %s\n", cpy.frstnam,cpy.lastnam,cpy.add,cpy.cntact); return; } } fwrite(&c,sizeof(struct cust),1,f); fclose (f); } printf("number of lines read is %d\n",num); }

  Read the article

< Previous Page | 36 37 38 39 40 41 42 43 44 45 46 47  | Next Page >