each_line

static VALUE
strio_each(int argc, VALUE *argv, VALUE self)
{
    struct StringIO *ptr = StringIO(self);
    VALUE line;

    RETURN_ENUMERATOR(self, argc, argv);

    while (!NIL_P(line = strio_getline(argc, argv, readable(ptr)))) {
        rb_yield(line);
    }
    return self;
}