c

dynamic memory allocation in C

int main() { int p; scanf("%d",&p); fun() { int arr[p]; //isn't this similar to dynamic memory allocation?? } } //if not then what other objective is achieved using malloc and calloc?? //Someone please throw some light :-) ...

Persisting a trie to a file - C

I have a trie which I am using to do some string processing. I have a simple compiler which generates trie from some data. Once generated, my trie won't change at run time. I am looking for an approach where I can persist the trie in a file and load it effectively. I have looked at sqllite to understand how they are persisting b-treebu...

Some general C questions.

Hello. I am trying to fully understand the process pro writing code in some language to execution by OS. In my case, the language would be C and the OS would be Windows. So far, I read many different articles, but I am not sure, whether I understand the process right, and I would like to ask you if you know some good articles on some sub...

How to copy a ram_base file to disk efficiently

I want to copy a large a ram-based file (located at /dev/shm direcotry) to local disk, is there some way for an efficient copy instead of read char one by one or create another piece memory? I can use only C language here. Is there anyway that I can put the memory file directly to disk? Thanks! ...

How to use /dev/random or urandom in C ?

I want to use /dev/random or /dev/urandom in C - how can i do it ? I don't know how can i handle them in C, if someone knows please tell me how. Thank you. ...

C system calls open / read / write / close problem.

Hello, given the following code (it's supposed to write "hellowolrd" in a "helloworld" file, and then read the text): #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #define FNAME "helloworld" int main(){ int filedes, nbytes; char buf[128]; /* Creates a file */ if((filedes=open(FNAME, O_CREAT | O_EXCL...

segfault during fclose()

fclose() is causing a segfault. I have : char buffer[L_tmpnam]; char *pipeName = tmpnam(buffer); FILE *pipeFD = fopen(pipeName, "w"); // open for writing ... ... ... fclose(pipeFD); I don't do any file related stuff in the ... yet so that doesn't affect it. However, my MAIN process communicates with another process through shared mem...

What can you do in C without "std" includes? Are they part of "C," or just libraries?

I apologize if this is a subjective or repeated question. It's sort of awkward to search for, so I wasn't sure what terms to include. What I'd like to know is what the basic foundation tools/functions are in C when you don't include standard libraries like stdio and stdlib. What could I do if there's no printf(), fopen(), etc? Also, a...

Problem implementing sorting algorithm in C with an array of structs

Well here is my little problem, first my code: struct alumn { char name[100]; char lastname[100]; int par; int nota; }; typedef struct alumn alumn; int bubble(alumn **arr, int length) { int i,j; alumn *temp; for (i=0; i<=length-2; i++) { for (j=i+1; j<=length-1;j++) { if ((*arr)[i].nota > (*arr)[j...

Question about "Link Map" output and "Assume" directive of MASM assembler.

I am new to MASM. So the questions may be quite basic. When I am using the MASM assembler, there's an output file called "Link Map". Its content is composed of the starting offset and length of various segments, such as Data segment, Code segment and Stack segment. I am wondering that, where are these information describing? Are they ta...

extracting string occurrence in c

I have a string that look something like this: long_str = "returns between paragraphs 20102/34.23\" - 9203 1232 \"test\" \"basic HTML\""; Note: Quotes are part of the string. int match(char *long_str){ char * str; if ((str = strchr(long_str, '"')) != NULL) str++; // last " ? else return 1; return 0; } Using strstr ...

Typecasting a floating value or using the math.h floor* functions?

Hi, I am coding up an implementation of Interpolation Search in C. The question is actually rather simple, I need to use the floating operations to do linear interpolation to find the correct index which will eventually be an integer result. In particular my probe index is: t = i + floor((((k-low)/(high-low)) * (j-i))); where, i,j,...

Custom Global Hotkey

I am trying to get the user defined global hot key for my application. Here is my application code, user.rc CONTROL "", IDC_MHOTKEY, HOTKEY_CLASS, WS_TABSTOP, 91, 86, 68, 14 function.cpp WORD wHotKey = SendDlgItemMessage(hwnd, IDC_MHOTKEY, HKM_GETHOTKEY, 0, 0); GLOBAL_HOTKEY= wHotKey; RegisterHotKey ( NULL, TURN...

C: lseek() related question.

I want to write some bogus text in a file ("helloworld" text in a file called helloworld), but not starting from the beginning. I was thinking to lseek() function. If I use the following code (edited): #include <unistd.h> #include <fcntl.h> #include <sys/stat.h> #include <sys/types.h> #include <stdlib.h> #include <stdio.h> #define fna...

C function prototype: void f(). Is it recommended?

Hi, I'm learning C and I saw in a book that a function prototype has the form void f() and in the function declaration or in the calling function, the f function takes arguments. Thus In the function declaration we have something like void f(long double y[], long double A) and in the calling function is f(y, A). The function is ...

C programming and TDD

Is Test Driven Development limited to OO? Or is it possible/useful to use it in conjunction with a procedural language? I have to start a greater project in C the next few weeks and I'm thinking of ways how to the developing. ...

Loading c libraries from php

Hi, in a recent project I've come really need the lib tre matching library. However the project is in php, and there are no php bindings for the library. I've tried to google how to create an interface for c libs, but all I found was the dl function which seams to load only php extensions. What am I missing? ...

malloc: error checking and freeing memory

Hi, I'm using malloc to make an error check of whether memory can be allocated or not for the particular array z1. ARRAY_SIZE is a predefined with a numerical value. I use casting as I've read it's safe to do so. long double *z1 = (long double *)malloc(sizeof (long double) * ARRAY_SIZE); if(z1 == NULL){ printf("Out of memory\n...

What does "void (* parse_arg_function)(const char*)" function argument mean in C?

What does the last function argument mean in C language? Please, point to documentation where I can read about it. void parse_options( int argc, char **argv, const OptionDef *options, void (* parse_arg_function)(const char*) ) Thanks. ...

Arrow operator (->) usage in C

I am currently learning C by reading a good beginner's book called "Teach Yourself C in 21 Days" (I have already learned Java and C# so I am moving at a much faster pace). I was reading the chapter on pointers and the -> (arrow) operator came up without explanation. I think that it is used to call members and functions (like the equivale...