I presume this is how I did it last time...

obj.c

typedef float f;typedef int i;
f t[2<<15];

void parse_obj() {
    f *l=t;i c;while((c=getchar())!=EOF)if((c=='v'||c=='f')&&scanf(" %f %f %f\n",l,l+1,l+2)==3)if(c=='v')l+=3;else{
        I k=(I){*l,*(l+1),*(l+2)};
        printf("FACE (%f, %f, %f), (%f, %f %f), (%f, %f, %f)\n",
            t[k.x*3],t[k.x*3+1],t[k.x*3+2],
            t[k.y*3],t[k.y*3+1],t[k.y*3+2],
            t[k.z*3],t[k.z*3+1],t[k.z*3+2]);
    }
}