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  • Another dynamic memory allocation bug.

    - by m4design
    I'm trying to allocate memory for a multidimensional array (8 rows, 3 columns). Here's the code for the allocation (I'm sure the error is clear for you) char **ptr = (char **) malloc( sizeof(char) * 8); for (i = 0; i < 3; i++) ptr[i] = (char *) malloc( sizeof(char) * 3); The crash happens when I reference this: ptr[3][0]; Unhandled exception at 0x0135144d in xxxx.exe: 0xC0000005: Access violation writing location 0xabababab. Are there any recommended references/readings for this kind of subject? Thanks.

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  • c++ : list(vector) definition with array

    - by Meloun
    I have Class Email, there is parameter "bcc" in her construktor. Its actually list of emails for copies. There is no fixed number of these emails and later i have to have possibility to extend this list. //construktor prototype Email::Email(vector<string> bcc) So i want to use type vector or list for that and function push_back(). How can i make a new instance with bcc emails? I need actually declaration with definition for my list. I've found this definition with iterator for integer type: int myints[] = {16,2,77,29}; Email myEmail(vector<int> (myints, myints + sizeof(myints) / sizeof(int) )); , but its not very user friend and i need it with strings. Is there something like this? Email myEmail(vector<string> ("first","second","third"));

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  • What is the wrong of this converted code?

    - by Gum Slashy
    I'm developing shape identification project using javacv and I have found some opencv code to identify U shapes in particular image and I have try to convert it in to javacv but it doesn't provide same out put. Can you please help me to convert this opencv code into javacv? This is Opencv code import cv2 import numpy as np img = cv2.imread('sofud.jpg') gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) ret,thresh = cv2.threshold(gray,127,255,1) contours,hierarchy = cv2.findContours(thresh,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE) for cnt in contours: x,y,w,h = cv2.boundingRect(cnt) if 10 < w/float(h) or w/float(h) < 0.1: cv2.rectangle(img,(x,y),(x+w,y+h),(0,0,255),2) cv2.imshow('res',img) cv2.waitKey(0) cv2.destroyAllWindows() This is the expected output This is the code that I have converted import com.googlecode.javacpp.Loader; import com.googlecode.javacv.CanvasFrame; import static com.googlecode.javacpp.Loader.*; import static com.googlecode.javacv.cpp.opencv_core.*; import static com.googlecode.javacv.cpp.opencv_imgproc.*; import static com.googlecode.javacv.cpp.opencv_highgui.*; import java.io.File; import javax.swing.JFileChooser; public class TestBeam { public static void main(String[] args) { CvMemStorage storage=CvMemStorage.create(); CvSeq squares = new CvContour(); squares = cvCreateSeq(0, sizeof(CvContour.class), sizeof(CvSeq.class), storage); JFileChooser f=new JFileChooser(); int result=f.showOpenDialog(f);//show dialog box to choose files File myfile=null; String path=""; if(result==0){ myfile=f.getSelectedFile();//selected file taken to myfile path=myfile.getAbsolutePath();//get the path of the file } IplImage src = cvLoadImage(path);//hear path is actual path to image IplImage grayImage = IplImage.create(src.width(), src.height(), IPL_DEPTH_8U, 1); cvCvtColor(src, grayImage, CV_RGB2GRAY); cvThreshold(grayImage, grayImage, 127, 255, CV_THRESH_BINARY); CvSeq cvSeq=new CvSeq(); CvMemStorage memory=CvMemStorage.create(); cvFindContours(grayImage, memory, cvSeq, Loader.sizeof(CvContour.class), CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE); System.out.println(cvSeq.total()); for (int i = 0; i < cvSeq.total(); i++) { CvRect rect=cvBoundingRect(cvSeq, i); int x=rect.x(),y=rect.y(),h=rect.height(),w=rect.width(); if (10 < (w/h) || (w/h) < 0.1){ cvRectangle(src, cvPoint(x, y), cvPoint(x+w, y+h), CvScalar.RED, 1, CV_AA, 0); //cvSeqPush(squares, rect); } } CanvasFrame cnvs=new CanvasFrame("Beam"); cnvs.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE); cnvs.showImage(src); //cvShowImage("Final ", src); } } This is the out put that I got please can some one help me to solve this problem ?

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  • Why freed struct in C still has data?

    - by kliketa
    When I run this code: #include <stdio.h> typedef struct _Food { char name [128]; } Food; int main (int argc, char **argv) { Food *food; food = (Food*) malloc (sizeof (Food)); snprintf (food->name, 128, "%s", "Corn"); free (food); printf ("%d\n", sizeof *food); printf ("%s\n", food->name); } I still get 128 Corn although I have freed food. Why is this? Is memory really freed?

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  • setsockopt (sys/socket.h)

    - by lojin
    The prototype for setsockopt is: int setsockopt(int socket, int level, int option_name, const void *option_value, socklen_t option_len); Are the following all correct ? Which are not ? a.) int buffsize = 50000; setsockopt(s, SOL_SOCKET, SO_RCVBUF, (char *)&buffsize, sizeof(buffsize)); b.) int buffsize = 50000; setsockopt(s, SOL_SOCKET, SO_RCVBUF, (void *)&buffsize, sizeof(buffsize)); c.) char *buffsize = "50000"; setsockopt(s, SOL_SOCKET, SO_RCVBUF, buffsize, strlen(buffsize)); d.) setsockopt(s, SOL_SOCKET, SO_RCVBUF, "50000", 5);

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  • Question regarding two dimensional array

    - by Sherwood Hu
    I have some problems using two dimensional array in the code and need some help. static const int PATTERNS[20][4]; static void init_PATTERN() { // problem #1 int (&patterns)[20][4] = const_cast<int[20][4]>(PATTERNS); ... } extern void UsePattern(int a, const int** patterns, int patterns_size); // problem #2 UsePattern(10, PATTERNS, sizeof(PATTERNS)/sizeof(PATTERNS[0])); in the first statement, I need to cast the const off the two dimensional array PATTERNS. The reason for this is that the init function is called only once, and in the remaining code, PATTERNS is strictly read-only. In the second statement, I need to pass PATTERNS array to the int** argument. Direct passing resulted a compile error. Thanks!

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  • Should I use a global var or call the function every time? C++

    - by extintor
    Im using: bool GetOS(LPTSTR pszOS) { OSVERSIONINFOEX osve; BOOL bOsVersionInfoEx; ZeroMemory(&osve, sizeof(OSVERSIONINFOEX)); osve.dwOSVersionInfoSize = sizeof(OSVERSIONINFOEX); if( !(bOsVersionInfoEx = GetVersionEx ((OSVERSIONINFO *) &osve)) ) return false; TCHAR buf[80]; StringCchPrintf( buf, 80, TEXT("%u.%u.%u.%u"), osve.dwPlatformId, osve.dwMajorVersion, osve.dwMinorVersion, osve.dwBuildNumber); StringCchCat(pszOS, BUFSIZE, buf); return true; } to get the windows version, and I am planning to use pszOS every a few minutes, Should I use pszOS as a global var or call GetOS() every time? What's the best option from a performance point of view.

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  • Why does accessing a member of a malloced array of structs seg fault?

    - by WSkinner
    I am working through Learn C The Hard Way and am stumped on something. I've written a simplified version of the problem I am running into to make it easier to get down to it. Here is the code: #include <stdlib.h> #define GROUP_SIZE 10 #define DATA_SIZE 64 struct Dummy { char *name; }; struct Group { struct Dummy **dummies; }; int main() { struct Group *group1 = malloc(sizeof(struct Group)); group1->dummies = malloc(sizeof(struct Dummy) * GROUP_SIZE); struct Dummy *dummy1 = group1->dummies[3]; // Why does this seg fault? dummy1->name = (char *) malloc(DATA_SIZE); return 0; } when I try to set the name pointer on one of my dummies I get a seg fault. Using valgrind it tells me this is uninitialized space. Why is this?

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  • callin' c from lua crashs while reallocating

    - by mkind
    hi folks, i got a crazy error within that for-loop matr=realloc(matr, newmax*sizeof(matr*)); for (i=0; i<newmax; i++){ matr[i]=realloc(matr[i], newmax*sizeof(int)); } matr is a multi-dimension array: int **matr. i need to resize column and row. first line resizes column and the for-loop resizes every row. it worked fine in c. now im working on a library for lua and it crashs here. compilin' works fine as well. but calling from lua crashs with lua: malloc.c:3552: mremap_chunk: Assertion `((size + offset) & (mp_.pagesize-1)) == 0' failed. i have no damn idea since it's working fine using it in c.

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  • How to create a simple Proxy to access web servers in C

    - by jesusiniesta
    Hi. I’m trying to create an small Web Proxy in C. First, I’m trying to get a webpage, sending a GET frame to the server. I don’t know what I have missed, but I am not receiving any response. I would really appreciate if you can help me to find what is missing in this code. int main (int argc, char** argv) { int cache_size, //size of the cache in KiB port, port_google = 80, dir, mySocket, socket_google; char google[] = "www.google.es", ip[16]; struct sockaddr_in socketAddr; char buffer[10000000]; if (GetParameters(argc,argv,&cache_size,&port) != 0) return -1; GetIP (google, ip); printf("ip2 = %s\n",ip); dir = inet_addr (ip); printf("ip3 = %i\n",dir); /* Creation of a socket with Google */ socket_google = conectClient (port_google, dir, &socketAddr); if (socket_google < 0) return -1; else printf("Socket created\n"); sprintf(buffer,"GET /index.html HTTP/1.1\r\n\r\n"); if (write(socket_google, (void*)buffer, LONGITUD_MSJ+1) < 0 ) return 1; else printf("GET frame sent\n"); strcpy(buffer,"\n"); read(socket_google, buffer, sizeof(buffer)); // strcpy(message,buffer); printf("%s\n", buffer); return 0; } And this is the code I use to create the socket. I think this part is OK, but I copy it just in case. int conectClient (int puerto, int direccion, struct sockaddr_in *socketAddr) { int mySocket; char error[1000]; if ( (mySocket = socket(AF_INET, SOCK_STREAM, 0)) == -1) { printf("Error when creating the socket\n"); return -2; } socketAddr->sin_family = AF_INET; socketAddr->sin_addr.s_addr = direccion; socketAddr->sin_port = htons(puerto); if (connect (mySocket, (struct sockaddr *)socketAddr,sizeof (*socketAddr)) == -1) { snprintf(error, sizeof(error), "Error in %s:%d\n", __FILE__, __LINE__); perror(error); printf("%s\n",error); printf ("-- Error when stablishing a connection\n"); return -1; } return mySocket; } Thanks!

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  • reading a file that doesn't exist

    - by John
    Hi, I have got a small program that prints the contents of files using the system call - read. unsigned char buffer[8]; size_t offset=0; size_t bytes_read; int i; int fd = open(argv[1], O_RDONLY); do{ bytes_read = read(fd, buffer, sizeof(buffer)); printf("0x%06x : ", offset); for(i=0; i<bytes_read; ++i) { printf("%c ", buffer[i]); } printf("\n"); offset = offset + bytes_read; }while(bytes_read == sizeof(buffer)); Now while running I give a file name that doesn't exist. It prints some kind of data mixed with environment variables and a segmentation fault at the end. How is this possible? What is the program printing? Thanks, John

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  • Efficient bitshifting an array of int?

    - by nn
    Hi, To be on the same page, let's assume sizeof(int)=4 and sizeof(long)=8. Given an array of integers, what would be an efficient method to bitshift the array to either the left or right? I am contemplating an auxiliary variable such as a long, that will compute the bitshift for the first pair of elements (index 0 and 1) and set the first element (0). Continuing in this fashion the bitshift for elements (index 1 and 2) will be computer, and then index 1 will be set. I think this is actually a fairly efficient method, but there are drawbacks. I cannot bitshift greater than 32 bits. I think using multiple auxiliary variables would work, but I'm envisioning recursion somewhere along the line.

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  • problem in reading output of dd command using pipe

    - by Ummar
    I am developing an application, in which I want to redirect the output (progress information) of dd command to my C++ program, but it is not actually getting the output, here is the code FILE * progressInfo = popen("gzip -dc backup/backup.img.gz | pv -ptrbe -i 2 -s 2339876653 | dd of=/dev/sdb","r"); if(!progressInfo) { return -1; } char buf[1024]; while(fgets(buff, sizeof(buff),progressInfo)!=NULL) { std::cout << buff << endl; } but the problem is the progress information is not received in buff, and the output is continuously printed on terminal, and above program halts on while(fgets(buff, sizeof(buff),progressInfo)!=NULL), and as soon as the dd operation is completed, the very next line to loop block is executed. if anyone has any idea why the output is not returned to buff, and its continuously retuned on terminal?

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  • Write to a binary file?

    - by rick irby
    Here is data structure w/ variables: struct Part_record { char id_no[3]; int qoh; string desc; double price: }; --- (Using "cin" to input data) --- Part_record null_part = {" ", 0," ",0.0}; --- --- file.seekg( -(long)sizeof(Part_record), ios::cur); file.write( ( char *)&part, sizeof(Part_record) ); The three variables, qoh, Id_no & price, write out correctly, but the "desc" variable is not right. Do I need to initialize Part_record some other way? It should be 20 characters in length. If you have enough info here, pls share your advice,thanks.

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  • Syntax error while copying an multidimensional array to another in C

    - by mantuko
    We are programming a ST269 microcontroller which has two IR distance sensors. To calibrate these sensors we made one table for each sensor with the distance we measured and the corresponding value we get from the ADC. Now we want to use one function to approximate the values in between. So we defined two two-dimensional arrays (one for each sensor) as global variables. In our function we then want to copy the one array we want to work with to a working array and approximate our values. So here's the code: ... unsigned int ir_werte_re[][] = { {8,553}, ... {83,133} }; unsigned int ir_werte_li[][] = { {8,566}, ... {83,147} }; ... unsigned int geradenaproximation(unsigned int messwert, unsigned int seite) { unsigned int working_array[16][16]; unsigned int i = 0; if (seite == 0) { for (i = 0; i < sizeof(working_array); i++) { working_array[i][0] = ir_werte_li[i][0]; i++; } } else { for (i = 0; i < sizeof(working_array); i++) { working_array[i][0] = ir_werte_re[i][0]; i++; } } i = 0; unsigned int y1 = 0; unsigned int x1 = 0; ... } This code is in a file called sensor.c. We didn't write anything about our global arrays in the sensor.h should we? The sensor.h of course is included in our main.c and there the function is called. We also tried to copy the arrays via memcpy(working_array, ir_werte_li, sizeof(working_array)); And in every way we do this we get a syntax error near unsigned in the line where we're declaring unsigned int y1 = 0; and I'm pretty sure that there is no syntax error in this line : ) The last time I spend coding in C is a few years away so I'm not sure if the way we try to do this is good. Perhaps we can solve this by using a pointer instead of really copying the array or something. So please help me out I'll appreciate your bits on this.

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  • Initializing and accessing a pointer from an array of pointers

    - by idealistikz
    Suppose I have the following: void **Init(int numElems) { //What is the best way to intialize 'ptrElems' to store an array of void *'s? void **ptrElems = malloc(numElems * sizeof(void *)); return ptrElems; } //What is the best way to return a pointer pointing at the index passed as a parameter? void **GetPtr(void **ptrElems, int index) { void **elem = elems + (index * sizeof(void *)); return elem; } First, what is the best way to intialize 'ptrElems' to store an array of pointers? I use malloc because assigning it to an array will not persist after the end of the function. Second, what is the best way to point to the pointer at the specified index? I tried typecasting the first line of the 'GetPtr' function to ensure proper pointer arithmetic, but I receive the warning, 'initialization from incompatible pointer type'. Is it necessary to typecast?

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  • Is there a way to convert code to a string and vice versa in Python?

    - by Dragos Toader
    The original question was: Is there a way to declare macros in Python as they are declared in C: #define OBJWITHSIZE(_x) (sizeof _x)/(sizeof _x[0]) Here's what I'm trying to find out: Is there a way to avoid code duplication in Python? In one part of a program I'm writing, I have a function: def replaceProgramFilesPath(filenameBr): def getProgramFilesPath(): import os return os.environ.get("PROGRAMFILES") + chr(92) return filenameBr.replace("<ProgramFilesPath>",getProgramFilesPath() ) In another part, I've got this code embedded in a string that will later be output to a python file that will itself be run: """ def replaceProgramFilesPath(filenameBr): def getProgramFilesPath(): import os return os.environ.get("PROGRAMFILES") + chr(92) return filenameBr.replace("<ProgramFilesPath>",getProgramFilesPath() ) """ How can I build a "macro" that will avoid this duplication?

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  • In C, is it possible do free only an array first or last position?

    - by user354959
    Hi there! I've an array, but I don't need its first (or last) position. So I point a new variable to the rest of the array, but I should free the array first/last position. For instance: p = read_csv_file(); q = p + 1; // I don't need the first CSV file field // Here I'd like to free only the first position of p return q; Otherwise I've to memcpy the array to other variable, excluding the first position, and then free the original array. Like this: p = read_csv_file(); q = (int*) malloc(sizeof(int) * (SOME_SIZE - 1)); memcpy(q, p+1, sizeof(int) * (SOME_SIZE - 1)); free(p); return q; But then I'll have the overhead of copying all the array. Is this possible to only free a single position of an array?

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  • non blocking TCP-acceptor not reading from socket

    - by Abruzzo Forte e Gentile
    I have the code below implementing a NON-Blocking TCP acceptor. Clients are able to connect without any problem and the writing seems occurring as well, but the acceptor doesn't read anything from the socket and the call to read() blocks indefinitely. Am I using some wrong setting for the acceptor? Kind Regards AFG int main(){ create_programming_socket(); poll_programming_connect(); while(1){ poll_programming_read(); } } int create_programming_socket(){ int cnt = 0; p_listen_socket = socket( AF_INET, SOCK_STREAM, 0 ); if( p_listen_socket < 0 ){ return 1; } int flags = fcntl( p_listen_socket, F_GETFL, 0 ); if( fcntl( p_listen_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){ return 1; } bzero( (char*)&p_serv_addr, sizeof(p_serv_addr) ); p_serv_addr.sin_family = AF_INET; p_serv_addr.sin_addr.s_addr = INADDR_ANY; p_serv_addr.sin_port = htons( p_port ); if( bind( p_listen_socket, (struct sockaddr*)&p_serv_addr , sizeof(p_serv_addr) ) < 0 ) { return 1; } listen( p_listen_socket, 5 ); return 0; } int poll_programming_connect(){ int retval = 0; static socklen_t p_clilen = sizeof(p_cli_addr); int res = accept( p_listen_socket, (struct sockaddr*)&p_cli_addr, &p_clilen ); if( res > 0 ){ p_conn_socket = res; int flags = fcntl( p_conn_socket, F_GETFL, 0 ); if( fcntl( p_conn_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){ retval = 1; }else{ p_connected = true; } }else if( res == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) { //printf( "poll_sock(): accept(c_listen_socket) would block\n"); }else{ retval = 1; } return retval; } int poll_programming_read(){ int retval = 0; bzero( p_buffer, 256 ); int numbytes = read( p_conn_socket, p_buffer, 255 ); if( numbytes > 0 ) { fprintf( stderr, "poll_sock(): read() read %d bytes\n", numbytes ); pkt_struct2_t tx_buf; int fred; int i; } else if( numbytes == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) { //printf( "poll_sock(): read() would block\n"); } else { close( p_conn_socket ); p_connected = false; retval = 1; } return retval; }

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  • please help me to find Bug in my Code (segmentation fault)

    - by Vikramaditya Battina
    i am tring to solve this http://www.spoj.com/problems/LEXISORT/ question it working fine in visual studio compiler and IDEone also but when i running in SPOJ compiler it is getting SEGSIGV error Here my code goes #include<stdio.h> #include<stdlib.h> #include<string.h> char *getString(); void lexisort(char **str,int num); void countsort(char **str,int i,int num); int main() { int num_test; int num_strings; char **str; int i,j; scanf("%d",&num_test); for(i=0;i<num_test;i++) { scanf("%d",&num_strings); str=(char **)malloc(sizeof(char *)*num_strings); for(j=0;j<num_strings;j++) { str[j]=(char *)malloc(sizeof(char)*11); scanf("%s",str[j]); } lexisort(str,num_strings); for(j=0;j<num_strings;j++) { printf("%s\n",str[j]); free(str[j]); } free(str); } return 0; } void lexisort(char **str,int num) { int i; for(i=9;i>=0;i--) { countsort(str,i,num); } } void countsort(char **str,int i,int num) { int buff[52]={0,0},k,x; char **temp=(char **)malloc(sizeof(char *)*num); for(k=0;k<52;k++) { buff[k]=0; } for(k=0;k<num;k++) { if(str[k][i]>='A' && str[k][i]<='Z') { buff[(str[k][i]-'A')]++; } else { buff[26+(str[k][i]-'a')]++; } } for(k=1;k<52;k++) { buff[k]=buff[k]+buff[k-1]; } for(k=num-1;k>=0;k--) { if(str[k][i]>='A' && str[k][i]<='Z') { x=buff[(str[k][i]-'A')]; temp[x-1]=str[k]; buff[(str[k][i]-'A')]--; } else { x=buff[26+(str[k][i]-'a')]; temp[x-1]=str[k]; buff[26+(str[k][i]-'a')]--; } } for(k=0;k<num;k++) { str[k]=temp[k]; } free(temp); }

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  • When do I need to deallocate memory? C++

    - by extintor
    I am using this code inside a class to make a webbrowser control visit a website: void myClass::visitWeb(const char *url) { WCHAR buffer[MAX_LEN]; ZeroMemory(buffer, sizeof(buffer)); MultiByteToWideChar(CP_ACP, MB_ERR_INVALID_CHARS, url, strlen(url), buffer, sizeof(buffer)-1); VARIANT vURL; vURL.vt = VT_BSTR; vURL.bstrVal = SysAllocString(buffer); // webbrowser navigate code... VariantClear(&vURL); } Do I need to do some memory deallocation here?, I see vURL is being deallocated by VariantClear but should I deallocate memory for buffer? I've been told that in another bool I have in the same app I shouldn't deallocate anything because everything clear out when the bool return true/false, but what happens on this void?

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  • write 2d array to a file in C (Operating system)

    - by Bobj-C
    Hello All, I used to use the code below to Write an 1D array to a File: FILE *fp; float floatValue[5] = { 1.1F, 2.2F, 3.3F, 4.4F, 5.5F }; int i; if((fp=fopen("test", "wb"))==NULL) { printf("Cannot open file.\n"); } if(fwrite(floatValue, sizeof(float), 5, fp) != 5) printf("File read error."); fclose(fp); /* read the values */ if((fp=fopen("test", "rb"))==NULL) { printf("Cannot open file.\n"); } if(fread(floatValue, sizeof(float), 5, fp) != 5) { if(feof(fp)) printf("Premature end of file."); else printf("File read error."); } fclose(fp); for(i=0; i<5; i++) printf("%f ", floatValue[i]); My question is if i want to write and read 2D array ??

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  • assignment makes pointer from integer without a cast

    - by mrblippy
    hi, i am trying to make a linked list and create some methods. but i am getting the error assignment makes pointer from integer without a cast. #include <stdio.h> #include <stdlib.h> #include "students.h" node_ptr create(void) { node_ptr students = (node_ptr) malloc(sizeof(struct node)); students->ID = 0; students->name = NULL; students->next = NULL; return students; } void insert_in_order(int n, node_ptr list) { node_ptr before = list; node_ptr new_node = (node_ptr) malloc(sizeof(struct node)); new_node->ID = n;//error is here i think while(before->next && (before->next->ID < n)) { before = before->next; } new_node->next = before->next; before->next = new_node; }

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  • parsing Two-dimensional array in c

    - by gitter78
    I'm trying to parse an array that looks like the one below: char *arr[][2] = { { "1", "Purple" }, { "2", "Blue" }, { "22", "Red" }, ... }; I was thinking having a loop as: char *func(char *a){ for(i = 0; i<sizeof(arr)/sizeof(arr[0]);i++){ if(strstr(a,arr[i][0])!=NULL) return arr[i][1]; } } char *out; const char *hello = "this is my 2 string"; out = func(hello); In this case, I'm trying to get the second value based on the first one: Purple, Blue Red, etc.. The question is how would go in parsing this and instead of printing out the value, return the value. UPDATE/FIXED: It has been fixed above. Thanks

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  • Router Alert options on IGMPv2 packets

    - by Scakko
    I'm trying to forge an IGMPv2 Membership Request packet and send it on a RAW socket. The RFC 3376 states: IGMP messages are encapsulated in IPv4 datagrams, with an IP protocol number of 2. Every IGMP message described in this document is sent with an IP Time-to-Live of 1, IP Precedence of Internetwork Control (e.g., Type of Service 0xc0), and carries an IP Router Alert option [RFC-2113] in its IP header So the IP_ROUTER_ALERT flag must be set. I'm trying to forge the strict necessary of the packet (e.g. only the IGMP header & payload), so i'm using the setsockopt to edit the IP options. some useful variables: #define C_IP_MULTICAST_TTL 1 #define C_IP_ROUTER_ALERT 1 int sockfd = 0; int ecsockopt = 0; int bytes_num = 0; int ip_multicast_ttl = C_IP_MULTICAST_TTL; int ip_router_alert = C_IP_ROUTER_ALERT; Here's how I open the RAW socket: sock_domain = AF_INET; sock_type = SOCK_RAW; sock_proto = IPPROTO_IGMP; if ((ecsockopt = socket(sock_domain,sock_type,sock_proto)) < 0) { printf("Error %d: Can't open socket.\n", errno); return 1; } else { printf("** Socket opened.\n"); } sockfd = ecsockopt; Then I set the TTL and Router Alert option: // Set the sent packets TTL if((ecsockopt = setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &ip_multicast_ttl, sizeof(ip_multicast_ttl))) < 0) { printf("Error %d: Can't set TTL.\n", ecsockopt); return 1; } else { printf("** TTL set.\n"); } // Set the Router Alert if((ecsockopt = setsockopt(sockfd, IPPROTO_IP, IP_ROUTER_ALERT, &ip_router_alert, sizeof(ip_router_alert))) < 0) { printf("Error %d: Can't set Router Alert.\n", ecsockopt); return 1; } else { printf("** Router Alert set.\n"); } The setsockopt of IP_ROUTER_ALERT returns 0. After forging the packet, i send it with sendto in this way: // Send the packet if((bytes_num = sendto(sockfd, packet, packet_size, 0, (struct sockaddr*) &mgroup1_addr, sizeof(mgroup1_addr))) < 0) { printf("Error %d: Can't send Membership report message.\n", bytes_num); return 1; } else { printf("** Membership report message sent. (bytes=%d)\n",bytes_num); } The packet is sent, but the IP_ROUTER_ALERT option (checked with wireshark) is missing. Am i doing something wrong? is there some other methods to set the IP_ROUTER_ALERT option? Thanks in advance.

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