fscanf/Pointing to a file in MATLAB Coder?

Hello, I am new to MATLAB coder and I am having some trouble translating the way I translate fscanf using coder.ceval. I know codegen supports fopen but not fscanf. Here's what I have:

        coder.cinclude("<stdio.h>");
        f = fopen(z,'r');
        f = coder.opaque('FILE*','NULL');
        coder.ceval('fscanf',f,formatSpec, A); %should read in values into 2-by-x double array
        fclose(f);

z is a string and the name of the file, formatSpec is '%d %d' and A is the appropriate size. How do I get the pointer to the file to be z? Any suggestions would be appreciated.

Answer 1

[Ryan Livingston]

Check out the example:

https://www.mathworks.com/help/coder/examples/read-a-text-file.html?searchHighlight=coderdemo_readfile&s_tid=doc_srchtitle

which shows using fread via coder.ceval. You should be able to switch:

f = coder.opaque('FILE*','NULL');
f = fopen(z,'r');

Also don't forget to NULL-terminate your strings before passing to C. That example uses a helper function:

% Create a NUL terminated C string given a MATLAB string
function y = c_string(s)
y = [s 0];

like so:

f = fopen(c_string(z),c_string('r'));

You'll need to preallocate A before reading into it and call coder.ceval('fclose',f) like the documentation example shows.