mdlflA20

sphr "red sphere" 
   lmbrtn rgb 0.8 0.2 0.2 end end
   0.0 0.0 0.0 1.0  % center,radius
end

You could read this file with the following code:

FILE *fp = fopen("red_sphere.mdla");
mdlInput inp(fp);

mdlKey k;
char *s;
float r, g, b;
float rgb[3];

k = inp.BeginChunk();    // k == "sphr"
s = inp.ReadString();
k = inp.BeginChunk();    // k == "lmbrtn"
k = inp.BeginChunk();    // k == "rgb"
r = inp.ReadFloat();
g = inp.ReadFloat();
b = inp.ReadFloat();
inp.EndChunk();
inp.EndChunk();
inp.ReadFloats(xyz, 3);
inp.EndChunk();          // You don't always have to read everything

Of course, any real code would use the keywords returned to decide what to read next. Usually one would have a switch statement that looks like this:

// Read a geometric object
mdlKey k = inp.BeginChunk();
if (k == mdlKey("sphr")) {
   // Read a string, a material chunk, and four floats
   }
else if (k == mdlKey("msh")) {
   // Read a string and a material, then do a lot of work
   }
...
else {
   cerr << "I'm ignoring a chunk with the unrecognized keyword '" << k << "'." << endl;
   }
inp.EndChunk();

When possible, it is preferable to have a function table whose use looks something like this:

// Read a color chunk
mdlKey k = inp.BeginChunk();
(colorChunkReaders[k])(inp);
inp.EndChunk();

It is recommended that the function which begins a chunk ends the chunk, since mismatching the BeginChunks and EndChunks can lead to a lot of confusion.