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  • Changing Value of Array Pointer When Passed to a Function

    - by ZAX
    I have a function which receives both the array, and a specific instance of the array. I try to change the specific instance of the array by accessing one of its members "color", but it does not actually change it, as can be seen by debugging (checking the value of color after function runs in the main program). I am hoping someone can help me to access this member and change it. Essentially I need the instance of the array I'm specifying to be passed by reference if nothing else, but I'm hoping there is an easier way to accomplish what I'm trying to do. Here's the structures: typedef struct adjEdge{ int vertex; struct adjEdge *next; } adjEdge; typedef struct vertex{ int sink; int source; int color; //0 will be white, 1 will be grey, 5 will be black int number; adjEdge *nextVertex; } vertex; And here is the function: void walk(vertex *vertexArray, vertex v, int source, maxPairing *head) { int i; adjEdge *traverse; int moveVertex; int sink; traverse = vertexArray[v.number-1].nextVertex; if(v.color != 5 && v.sink == 5) { sink = v.number; v.color = 5; addMaxPair(head, source, sink); } else { walk(vertexArray, vertexArray[traverse->vertex-1], source, head); } } In particular, v.color needs to be changed to a 5, that way later after recursion the if condition blocks it.

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  • sIFR encoding the non-breaking space char - %20

    - by Jay Carroll
    Gotta be something I'm doing wrong when converting the ttf with OpensIFRr, but I'm seeing %20 chars for non-breaking spaces in all sIFR'd text. I'm using the jQuery sIFR plugin (3.04) with the following: <div><h1>My Example Text</h1></div> ... <script type="text/javascript"> <!-- var $j = jQuery; $j(document).ready(function(){ $j('h1').sifr({ path: '/fonts/', font: 'fancy_script' }); }); //--> </script> Happens no matter which font I use, TIA... -Jay

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  • Isn't the C++ standard library backward-compatible?

    - by Chris Metzler
    Hi. I'm working on a 64-bit Linux system, trying to build some code that depends on third-party libraries for which I have binaries. During linking, I get a stream of undefined reference errors for one of the libraries, indicating that the linker couldn't resolve references to standard C++ functions/classes, e.g.: librxio.a(EphReader.o): In function `gpstk::EphReader::read_fic_data(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)': EphReader.cpp:(.text+0x27c): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)' EphReader.cpp:(.text+0x4e8): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)' I'm not really a C++ programmer, but this looks to me like it can't find the standard library. Doing some more research, I got the following when I looked at librxio's dependency for the standard library: $ ldd librxio.so.16.0 ./librxio.so.16.0: /usr/lib64/libstdc++.so.6: version `GLIBCXX_3.4.9' not found (required by ./librxio.so.16.0) libm.so.6 => /lib64/libm.so.6 (0x00002aaaaad45000) libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00002aaaaafc8000) libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00002aaaab2c8000) libc.so.6 => /lib64/libc.so.6 (0x00002aaaab4d7000) /lib64/ld-linux-x86-64.so.2 (0x0000555555554000) So I read that as saying that librxio (one of the third-party libraries) requires at least v3.4.9 of the standard library. But the version I have installed is 4.1.2: $ rpm -qa | grep libstdc compat-libstdc++-33-3.2.3-61.x86_64 libstdc++-devel-4.1.2-14.el5.i386 libstdc++-devel-4.1.2-14.el5.x86_64 libstdc++-4.1.2-14.el5.x86_64 libstdc++-4.1.2-14.el5.i386 Shouldn't this work? The shared object major number is 6, same as for v3.4.9. At this level, shouldn't this be backward compatible? It seems like the third-party library is looking for an earlier version of the standard library than what I have installed; but isn't there backward compatibility between versions with the same major number for the shared library? Again, I'm not really a C++ programmer; but I don't see what the problem is. Any advice greatly appreciated. Thanks.

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  • Is there performance to be gained by moving storage allocation local to a member function to its cla

    - by neuviemeporte
    Suppose I have the following C++ class: class Foo { double bar(double sth); }; double Foo::bar(double sth) { double a,b,c,d,e,f a = b = c = d = e = f = 0; /* do stuff with a..f and sth */ } The function bar() will be called millions of times in a loop. Obviously, each time it's called, the variables a..f have to be allocated. Will I gain any performance by making the variables a..f members of the Foo class and just initializing them at the function's point of entry? On the other hand, the values of a..f will be dereferenced through this-, so I'm wondering if it isn't actually a possible performance degradation. Is there any overhead to accessing a value through a pointer? Thanks!

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  • How to create C++ istringstream from a char array with null(0) characters?

    - by Morpheus
    I have a char array which contains null characters at random locations. I tried to create an iStringStream using this array (encodedData_arr) as below, I use this iStringStream to insert binary data(imagedata of Iplimage) to a MySQL database blob field(using MySQL Connector/C++'s setBlob(istream *is) ) it only stores the characters upto the first null character. Is there a way to create an iStringStream using a char array with null characters? unsigned char *encodedData_arr = new unsigned char[data_vector_uchar->size()]; // Assign the data of vector<unsigned char> to the encodedData_arr for (int i = 0; i < vec_size; ++i) { cout<< data_vector_uchar->at(i)<< " : "<< encodedData_arr[i]<<endl; } // Here the content of the encodedData_arr is same as the data_vector_uchar // So char array is initializing fine. istream *is = new istringstream((char*)encodedData_arr, istringstream::in || istringstream::binary); prepStmt_insertImage->setBlob(1, is); // Here only part of the data is stored in the database blob field (Upto the first null character)

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  • Cant free memory.

    - by atch
    In code: int a[3][4] = {1,2,3,4, 5,6,7,8, 9,10,11,12}; template<class T, int row, int col> void invert(T a[row][col]) { T* columns = new T[col]; T* const free_me = columns; for (int i = 0; i < col; ++i) { for (int j = 0; j < row; ++j) { *columns = a[j][i]; ++columns;//SOMETIMES VALUE IS 0 } } delete[] free_me;//I'M GETTING ERROR OF HEAP ABUSE IN THIS LINE } int main(int argc, char* argv[]) { invert<int,3,4>(a); } I've observed that while iterating, value of variable columns equals zero and I think thats the problem. Thanks for your help.

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  • C++ How do you set an array of pointers to null in an initialiser list like way?

    - by boredjoe
    I am aware you cannot use an initialiser list for an array. However I have heard of ways that you can set an array of pointers to NULL in a way that is similar to an initialiser list. I am not certain how this is done. I have heard that a pointer is set to NULL by default, though I do not know if this is guaranteed/ in the C++ standard. I am also not sure if initialising through the new operator compared to normal allocation can make a difference too.

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  • Cannot determine why pointer variable will not address elements in a string in this program?

    - by Smith Will Suffice
    I am attempting to utilize a pointer variable to access elements of a string and there are issues with my code generating a compilation error: #include <stdio.h> #define MAX 29 char arrayI[250]; char *ptr; int main(void) { ptr = arrayI; puts("Enter string to arrayI: up to 29 chars:\n"); fgets(arrayI, MAX, stdin); printf("\n Now printing array by pointer:\n"); printf("%s", *ptr); ptr = arrayI[1]; //(I set the pointer to the second array char element) printf("%c", *ptr); //Here is where I was wanting to use my pointer to //point to individual array elements. return 0; } My compiler crieth: [Warning] assignment makes pointer from integer without a cast [enabled by default] I do not see where my pointer was ever assigned to the integer data type? Could someone please explain why my attempt to implement a pointer variable is failing? Thanks all!

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  • Threading across multiple files

    - by Zach M.
    My program is reading in files and using thread to compute the highest prime number, when I put a print statement into the getNum() function my numbers are printing out. However, it seems to just lag no matter how many threads I input. Each file has 1 million integers in it. Does anyone see something apparently wrong with my code? Basically the code is giving each thread 1000 integers to check before assigning a new thread. I am still a C noobie and am just learning the ropes of threading. My code is a mess right now because I have been switching things around constantly. #include <stdio.h> #include <stdlib.h> #include <time.h> #include <string.h> #include <pthread.h> #include <math.h> #include <semaphore.h> //Global variable declaration char *file1 = "primes1.txt"; char *file2 = "primes2.txt"; char *file3 = "primes3.txt"; char *file4 = "primes4.txt"; char *file5 = "primes5.txt"; char *file6 = "primes6.txt"; char *file7 = "primes7.txt"; char *file8 = "primes8.txt"; char *file9 = "primes9.txt"; char *file10 = "primes10.txt"; char **fn; //file name variable int numberOfThreads; int *highestPrime = NULL; int fileArrayNum = 0; int loop = 0; int currentFile = 0; sem_t semAccess; sem_t semAssign; int prime(int n)//check for prime number, return 1 for prime 0 for nonprime { int i; for(i = 2; i <= sqrt(n); i++) if(n % i == 0) return(0); return(1); } int getNum(FILE* file) { int number; char* tempS = malloc(20 *sizeof(char)); fgets(tempS, 20, file); tempS[strlen(tempS)-1] = '\0'; number = atoi(tempS); free(tempS);//free memory for later call return(number); } void* findPrimality(void *threadnum) //main thread function to find primes { int tNum = (int)threadnum; int checkNum; char *inUseFile = NULL; int x=1; FILE* file; while(currentFile < 10){ if(inUseFile == NULL){//inUseFIle being used to check if a file is still being read sem_wait(&semAccess);//critical section inUseFile = fn[currentFile]; sem_post(&semAssign); file = fopen(inUseFile, "r"); while(!feof(file)){ if(x % 1000 == 0 && tNum !=1){ //go for 1000 integers and then wait sem_wait(&semAssign); } checkNum = getNum(file); /* * * * * I think the issue is here * * * */ if(checkNum > highestPrime[tNum]){ if(prime(checkNum)){ highestPrime[tNum] = checkNum; } } x++; } fclose(file); inUseFile = NULL; } currentFile++; } } int main(int argc, char* argv[]) { if(argc != 2){ //checks for number of arguements being passed printf("To many ARGS\n"); return(-1); } else{//Sets thread cound to user input checking for correct number of threads numberOfThreads = atoi(argv[1]); if(numberOfThreads < 1 || numberOfThreads > 10){ printf("To many threads entered\n"); return(-1); } time_t preTime, postTime; //creating time variables int i; fn = malloc(10 * sizeof(char*)); //create file array and initialize fn[0] = file1; fn[1] = file2; fn[2] = file3; fn[3] = file4; fn[4] = file5; fn[5] = file6; fn[6] = file7; fn[7] = file8; fn[8] = file9; fn[9] = file10; sem_init(&semAccess, 0, 1); //initialize semaphores sem_init(&semAssign, 0, numberOfThreads); highestPrime = malloc(numberOfThreads * sizeof(int)); //create an array to store each threads highest number for(loop = 0; loop < numberOfThreads; loop++){//set initial values to 0 highestPrime[loop] = 0; } pthread_t calculationThread[numberOfThreads]; //thread to do the work preTime = time(NULL); //start the clock for(i = 0; i < numberOfThreads; i++){ pthread_create(&calculationThread[i], NULL, findPrimality, (void *)i); } for(i = 0; i < numberOfThreads; i++){ pthread_join(calculationThread[i], NULL); } for(i = 0; i < numberOfThreads; i++){ printf("this is a prime number: %d \n", highestPrime[i]); } postTime= time(NULL); printf("Wall time: %ld seconds\n", (long)(postTime - preTime)); } } Yes I am trying to find the highest number over all. So I have made some head way the last few hours, rescucturing the program as spudd said, currently I am getting a segmentation fault due to my use of structures, I am trying to save the largest individual primes in the struct while giving them the right indices. This is the revised code. So in short what the first thread is doing is creating all the threads and giving them access points to a very large integer array which they will go through and find prime numbers, I want to implement semaphores around the while loop so that while they are executing every 2000 lines or the end they update a global prime number. #include <stdio.h> #include <stdlib.h> #include <time.h> #include <string.h> #include <pthread.h> #include <math.h> #include <semaphore.h> //Global variable declaration char *file1 = "primes1.txt"; char *file2 = "primes2.txt"; char *file3 = "primes3.txt"; char *file4 = "primes4.txt"; char *file5 = "primes5.txt"; char *file6 = "primes6.txt"; char *file7 = "primes7.txt"; char *file8 = "primes8.txt"; char *file9 = "primes9.txt"; char *file10 = "primes10.txt"; int numberOfThreads; int entries[10000000]; int entryIndex = 0; int fileCount = 0; char** fileName; int largestPrimeNumber = 0; //Register functions int prime(int n); int getNum(FILE* file); void* findPrimality(void *threadNum); void* assign(void *num); typedef struct package{ int largestPrime; int startingIndex; int numberCount; }pack; //Beging main code block int main(int argc, char* argv[]) { if(argc != 2){ //checks for number of arguements being passed printf("To many threads!!\n"); return(-1); } else{ //Sets thread cound to user input checking for correct number of threads numberOfThreads = atoi(argv[1]); if(numberOfThreads < 1 || numberOfThreads > 10){ printf("To many threads entered\n"); return(-1); } int threadPointer[numberOfThreads]; //Pointer array to point to entries time_t preTime, postTime; //creating time variables int i; fileName = malloc(10 * sizeof(char*)); //create file array and initialize fileName[0] = file1; fileName[1] = file2; fileName[2] = file3; fileName[3] = file4; fileName[4] = file5; fileName[5] = file6; fileName[6] = file7; fileName[7] = file8; fileName[8] = file9; fileName[9] = file10; FILE* filereader; int currentNum; for(i = 0; i < 10; i++){ filereader = fopen(fileName[i], "r"); while(!feof(filereader)){ char* tempString = malloc(20 *sizeof(char)); fgets(tempString, 20, filereader); tempString[strlen(tempString)-1] = '\0'; entries[entryIndex] = atoi(tempString); entryIndex++; free(tempString); } } //sem_init(&semAccess, 0, 1); //initialize semaphores //sem_init(&semAssign, 0, numberOfThreads); time_t tPre, tPost; pthread_t coordinate; tPre = time(NULL); pthread_create(&coordinate, NULL, assign, (void**)numberOfThreads); pthread_join(coordinate, NULL); tPost = time(NULL); } } void* findPrime(void* pack_array) { pack* currentPack= pack_array; int lp = currentPack->largestPrime; int si = currentPack->startingIndex; int nc = currentPack->numberCount; int i; int j = 0; for(i = si; i < nc; i++){ while(j < 2000 || i == (nc-1)){ if(prime(entries[i])){ if(entries[i] > lp) lp = entries[i]; } j++; } } return (void*)currentPack; } void* assign(void* num) { int y = (int)num; int i; int count = 10000000/y; int finalCount = count + (10000000%y); int sIndex = 0; pack pack_array[(int)num]; pthread_t workers[numberOfThreads]; //thread to do the workers for(i = 0; i < y; i++){ if(i == (y-1)){ pack_array[i].largestPrime = 0; pack_array[i].startingIndex = sIndex; pack_array[i].numberCount = finalCount; } pack_array[i].largestPrime = 0; pack_array[i].startingIndex = sIndex; pack_array[i].numberCount = count; pthread_create(&workers[i], NULL, findPrime, (void *)&pack_array[i]); sIndex += count; } for(i = 0; i< y; i++) pthread_join(workers[i], NULL); } //Functions int prime(int n)//check for prime number, return 1 for prime 0 for nonprime { int i; for(i = 2; i <= sqrt(n); i++) if(n % i == 0) return(0); return(1); }

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  • StAX - Setting the version and encoding using XMLStreamWriter

    - by Anurag
    Hi, I am using StAX for creating XML files and then validating the file with and XSD. I am getting an error while creating the XML file: javax.xml.stream.XMLStreamException: Underlying stream encoding 'Cp1252' and input paramter for writeStartDocument() method 'UTF-8' do not match. at com.sun.xml.internal.stream.writers.XMLStreamWriterImpl.writeStartDocument(XMLStreamWriterImpl.java:1182) Here is the code snippet: XMLOutputFactory xof = XMLOutputFactory.newInstance(); try{ XMLStreamWriter xtw = xof.createXMLStreamWriter(new FileWriter(fileName)); xtw.writeStartDocument("UTF-8","1.0");} catch(XMLStreamException e) { e.printStackTrace(); } catch(IOException ie) { ie.printStackTrace(); } I am running this code on unix. Does anybody know how to set the version and encoding style.

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  • Counting the number of characters in a file

    - by Kat
    I'm writing a program that for one part asks for the program to print how many characters (including whitespaces) are in a file. The code I have right now though returns 0 every time though and I'm not sure why it isn't counting the characters. public int getcharCount(Scanner textFile) { int count = 0; while(textFile.hasNext()) { String line = textFile.nextLine(); for(int i=0; i < line.length(); i++) count++; } return count; }

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  • Count max rectangles number, that can be placed inside character

    - by Nickolay
    Hi, I need a solution for quite complex problem. Exactly, I need to calculate the number of rectangles that can be placed inside letter/character with given size, considering that all rectangles are the same size, but it(the size) and the letter/character(of some regular specific font) itself can be changed by user(this will be used as webside calculator of signboard price). If describe this graphically, it looks like this. Any ideas or useful links will be much appreciated. Thanks in advance

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  • If-elseif-else Logic Question

    - by Changeling
    I have a set of three values, call them x, y, and z. If value A happens to match only one in the set x, y, and z, then that means we have a proper match and we stop searching for a match, even if it is at y. It can match any one in that set. These values x, y, and z are non-constant so I cannot use a switch-case statement. How do I do this with an if-elseif-else statements without having to use GOTO. I am using C++ (no boost or any of that other fancy stuff). Now, I am trying to do this in code and it is racking my brain this morning (not enough coffee?)

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  • Byte from string/int in C++

    - by Tim van Elsloo
    Hi, I'm a beginning user in C++ and I want to know how to do this: How can I 'create' a byte from a string/int. So for example I've: string some_byte = "202"; When I would save that byte to a file, I want that the file is 1 byte instead of 3 bytes. How is that possible? Thanks in advance, Tim

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  • how to generate a random String? in java

    - by chandra wibowo
    hi everyone, i have an object called Student, and it has studentName, studentId, studentAddress, etc. for the studentId, i have to generate random string consist of seven numeric charaters, eg. studentId = getRandomId(); studentId = "1234567" <-- from the random generator. and i have to make sure that there is no duplicate id. thanks in advance

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  • SVN 255 Character Problem

    - by Tom
    Hi Guys, I am using TortiseSVN and we have a problem when we exporting etc because subversion errors. The path has a character limit 255 - so I am not sure if this is the problem [I think it is in Win7 x-64 bit] How do I fix this ? i.e. allow paths for 255 characters ?

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  • How to Find and Replace the Enter character?

    - by karikari
    How to Find and Replace the 'Enter' characters in the text file? Here is my code: string searchString( "\r" ); // <------- how to look for ENTER chars? string replaceString( "XXXX" ); assert( searchString != replaceString ); string::size_type pos = 0, pos3 =0; while ( (pos = test.find(searchString, pos)) != string::npos ) { test.replace( pos, searchString.size(), replaceString ); pos++; }

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  • How do I use multiple precisions in printf()?

    - by Tommy
    Looking at the information under the heading "Precision can be omitted or be any of:". The example: printf("%.*s", 3, "abcdef"); works, outputting:abc (truncating the rest of the string.) Now, I would like to have a string with multiple parameters formatted (truncated): printf("%.*s, %.*s", 3, 3, "abcdef", "xyz123"); but the program crashes. What is the correct syntax? Thank You.

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  • How do I use multiple precisions in prinft()?

    - by Tommy
    Looking at the information under the heading "Precision can be omitted or be any of:". The example: printf("%.*s", 3, "abcdef"); works, outputting:abc (truncating the rest of the string.) Now, I would like to have a string with multiple parameters formatted (truncated): printf("%.*s", "%.*s", 3, 3, "abcdef", "xyz123"); but the program crashes. What is the correct syntax? Thank You.

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