Finding end of file while reading from it

Question

void graph::fillTable()
{
  ifstream fin;
  char X;
  int slot=0;

  fin.open(\"data.txt\");

  while(fin.good()){

  fin>>Gtable[slot].Name;
  fin>>Gtab         


        

Answer 1

*Edited in response to James' comment - the code now uses a good() check instead of a !eof() check, which will allow it to catch most errors. I also threw in an is_open() check to ensure the stream is associated with the file.*

Generally, you should try to structure your file reading in a loop as follows:

ifstream fin("file.txt");
char a = '\0';
int b = 0;
char c = '\0';

if (!fin.is_open())
    return 1; // Failed to open file.

// Do an initial read. You have to attempt at least one read before you can
// reliably check for EOF.
fin >> a;

// Read until EOF
while (fin.good())
{
    // Read the integer
    fin >> b;

    // Read the remaining characters (I'm just storing them in c in this example)
    for (int i = 0; i < b; i++)
        fin >> c;

    // Begin to read the next line. Note that this will be the point at which
    // fin will reach EOF. Since it is the last statement in the loop, the
    // file stream check is done straight after and the loop is exited.
    // Also note that if the file is empty, the loop will never be entered.
    fin >> a;
}

fin.close();

This solution is desirable (in my opinion) because it does not rely on adding random breaks inside the loop, and the loop condition is a simple good() check. This makes the code easier to understand.