Which face data are you after? All three? (and by that I mean vertex, texture and normal).
Funnily enough, I've already done this; I wrote a parser that converts .obj files into a smaller proprietary project for my university project.
The reason I'm asking about the face data is that I'm guessing that you might be drawing models using indexed data, which is similar to what I did. I only used the vertex faces. I didn't need texture faces and calculated the normals myself.