Monthly Archives: December 2016

C/C++: Get the size of a file in bytes

 in C / C++  tagged C/C++ / C++ by

The following function accepts the name of a file as a string and returns the size of the file in bytes. If for any reason it cannot get the file information, it will return the value -1.

[download id=”2417″]

In our header file, we used the following pre-processor directives around our declarations

#ifdef __cplusplus
extern "C" {
#endif
#ifdef __cplusplus
}
#endif

to allow c++ code to call our c function.

The usage example code makes three tests:

  1. Getting the size of the currently executing binary, as it will have a non-zero size
  2. Getting the size of a non-existing file, to check that it will properly return -1
  3. Getting the size of an empty file, to be sure it is empty we create it right before the test

[download id=”2417″]

Source file (file_helpers.c)

#include <sys/stat.h>
#include "file_helpers.h"

//It will return the size of the file in bytes OR -1 in case that it cannot get any status information for it
off_t get_file_size(const char *filename) {
  //Specialised struct that can hold status attributes of files.
  struct stat st;

  //Gets file attributes for filename and puts them in the stat buffer.
  // Upon successful completion, it returns 0, otherwise and errno will be set to indicate the error.
  if (stat(filename, &st) == 0) {
    //Size of file, in bytes.
    return st.st_size;
  }

  return -1;
}

Header file (file_helpers.h)


#ifndef GM_S_LITTLE_HELPERS_FILE_HELPERS_H
#define GM_S_LITTLE_HELPERS_FILE_HELPERS_H

#ifdef __cplusplus
extern "C" {
#endif

off_t get_file_size(const char *filename);

#ifdef __cplusplus
}
#endif

#endif //GM_S_LITTLE_HELPERS_FILE_HELPERS_H

Usage example (main.cpp)

#include <iostream>
#include "file_helpers.h"

void print_file_size(const char *filename) {
  const off_t size_of_file = get_file_size(filename);
  if (size_of_file > 0) {
    printf("The size of '%s' is %zd bytes\n", filename, size_of_file);
  }
  else if (size_of_file == 0) {
    printf("The file '%s' is empty\n", filename);
  }
  else {
    printf("Could not get the status information for file '%s'\n", filename);
  }
}

int main(int argc, char *argv[]) {

  //Testing a non-zero sized file
  print_file_size(argv[0]);
  //Testing for a non-existing file
  print_file_size("some file that does not exist...");
  const char * filename = "/tmp/some_empty_file";
  //Creating an empty file
  FILE * fout = fopen(filename, "w");
  fclose(fout);
  //Testing for an empty file
  print_file_size(filename);

  return 0;
}

[download id=”2417″]

C/C++: Perform safe sprintf 1

 in C / C++  tagged C/C++ / C++ / snprintf / vsnprintf by

The following function accepts the address of a char * buffer, the formatting string for printf along with all the parameters needed to fill the formatting string and updates the location of the buffer to point at the final formatted string.

[download id=”2418″]

This code does not require the user to perform malloc before filling in the buffer. Using vsnprintf (variation of snprintf for variable arguments) it will automatically find the correct size that the buffer should have, allocate the space, switch the pointer of the buffer and prepare the final string using the formatting arguments.

In our header file, we used the following pre-processor directives around our declarations

#ifdef __cplusplus
extern "C" {
#endif
#ifdef __cplusplus
}
#endif

to allow c++ code to call our function.

[download id=”2418″]

Source file (string_helpers.c)


#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include "string_helpers.h"

int safe_sprintf(char ** buffer, const char *format, ...) {

  va_list arguments;
  //The va_start(va_list arguments, last) macro initializes and must be called first.
  //The argument last is the name of the last argument before the variable argument list, that is, the last argument of which the calling function knows the type.
  va_start (arguments, format);

  //Upon successful return, vsnprintf returns the number of characters printed (excluding the null byte used to end output to strings).
  //For that reason we add one at the end of the length.
  const int length = vsnprintf(NULL, 0, format, arguments) + 1;

  //Each invocation of va_start() must be matched by a corresponding invocation of va_end() in the same function.
  // After the call va_end(arguments) the variable arguments is undefined.
  // Multiple traversals of the list, each bracketed by va_start() and va_end() are possible. va_end() may be a macro or a function.
  va_end (arguments);

  if (*buffer) {
    free(*buffer);
  }
  if (!(*buffer = malloc(length * sizeof(char)))) {
    return EXIT_FAILURE;
  }

  va_start(arguments, format);
  vsnprintf(*buffer, (size_t) length, format, arguments);
  va_end (arguments);

  return EXIT_SUCCESS;
}

Header file (string_helpers.h)


#ifndef GM_S_LITTLE_HELPERS_STRING_HELPERS_H
#define GM_S_LITTLE_HELPERS_STRING_HELPERS_H

#ifdef __cplusplus
extern "C" {
#endif

int safe_sprintf(char ** buffer, const char *format, ...);

#ifdef __cplusplus
}
#endif

#endif //GM_S_LITTLE_HELPERS_STRING_HELPERS_H

Usage example (main.cpp)


#include <iostream>
#include "string_helpers.h"

int main() {

  char * buffer;
  safe_sprintf(&buffer, "Hello, World!\nFrom Line %d in function %s of the file %s.", __LINE__, __func__, __FILE__);
  printf("%s", buffer);
  return 0;
}

[download id=”2418″]

IEEE Region 8 Stockholm 2017 1

 in IEEE  tagged ieee / IEEE Region 8 / Region 8 by

This application holds all the reports and basic information of the 108th IEEE Region 8 Committee Meeting held in Stockholm on 25-26 of March 2017.

You will find:

  • The Agenda Book
  • All available OpCom reports
  • All available Committee reports
  • All available Section reports
  • Meeting schedule
  • Order of the day
  • Travel information

Get it on Google Play

This slideshow requires JavaScript.

Google Hash Code 2017 Nicosia Cyprus – Call for participation

 in 2017 / Google / Hash Code  tagged 2017 / code / cyprus / google / hash / hash code by

We’ll be hosting a hub at the University of Cyprus for the Online Qualification Round of Hash Code, a team-based programming competition created by Google for university students and industry professionals. The Online Qualification Round takes place on the 23rd of February at 19:30 EET and registered teams from Cyprus are invited to participate from our hub, which will take place at the Computer Science Department. Top scoring teams from the Online Qualification Round will then be invited to Google’s Paris office to compete in the Final Round of the competition in April.

If you’re interested in joining our hub, find a team (two to four people) and register at g.co/hashcode. Make sure to select University of Cyprus from the list of hubs in the Judge System.

For more information about this and other hubs in Cyprus (including the twin event in Limassol) visit https://goo.gl/XSfUPv

Hash Code 2017 Nicosia Cyprus – Facebook Event

Thanks!

Address:

Rooms: 101, 102, 103
Department of Computer Science,
Pure and Applied Sciences (FST-01)
University of Cyprus
1 University Avenue
2109 Aglantzia, CYPRUS

Date and Time:

23 February 2017
From: 19:30 EET
To: 23:30 EET

Free Amenities Offered

High speed Internet access
Wi-Fi access to the Internet for your mobile devices (personal computers and smart phones)
Lab computers will be available for use by the participants
Food in the form of snacks and beverages will be available outside the labs

hash-code-2017-hub-organizer-poster-1-nicosia