Question

I have been required to write a function that reads the BSDF data format defined by Zemax
An example of such file can be found at the following page: BSDF file example

I would like to use, if possible, only standard ifstream functions.

I have already prepared all the necessary datamembers inside a dedicated class.

I am now trying to write the function that reads the data from the file.

Problems:

• how do I exclude comment lines? as documented, they start with an hash # I was going for something like

  void ReadBSDFFile(myclass &object)
  {
  ifstream infile;
  
  infile.open(object.BRDFfilename);
  
  char c;
  infile.get(c);
  while (c == "#") // Problem, apparently I cannot compare in this way. How should I do it?
  {
     getline(infile, line);
     infile.get(c);
  }
  // at this point I would like to go back one character (because I do not want to lose the non-hash character that ended up in *c*)
  infile.seekg(-1, ios_base::cur);
  
  // Do all the rest
  
  infile.close();
  }
  

• in a similar way, I would like to verify that I am at the correct line later on (e.g. the “AngleOfIncidence” line). Could I do it in this way?

  string AngleInc;
  
  infile >> AngleInc;
  
  if (AngleInc != "AngleOfIncidence")
  {
     //error
  }
  

Thanks to anyone who will comment/help. Constructive criticism is welcomed.

Federico

EDIT:

Thanks to Joachim Pileborg below, I managed to proceed up to the data blocks part of the file.

Now I have the following problem. When reaching the datablocks, I wrote the following piece of code, but at the second iteration (i = 1) i receive the error message for the TIS line.
Could someone help me understand why this does not work?
Thanks

Note: blocks is the number on the AngleOfIncidence line, rows the one on the ScatterAzimuth line and columns the one on the ScatterRadial. I tested and verified that this part of the function works as desired.

// now reading the data blocks.

for (int i=0; i<blocks; i++)
{
    // TIS line
    getline(infile, line);
    if (line.find("TIS") == string::npos)
    {
        // if not, error message
    }

    // Data block
    for (int j=0; j<rows; j++)
    {
        for (int k=0; k<columns; k++)
        {
            infile >> object.BRDFData[i][j][k];
        }
    }
}

EDIT 2:

solved adding infile.seekg(+2, ios_base::cur); as a last line of the i loop.

Answer 1

The reading loop could be simplified like this:

std::string line;
while (getline(infile, line))
{
    if (line[0] != '#')
    {
        // Not a comment, do something with the line
        if (line.find("AngleOfIncidence") != std::string::npos)
        {
            // On the AngleOfIncidence line, do special things here
        }
    }
}

It’s might not be optimal, just something written at the top of my head, but should work.