/*
 * call-seq:
 *     digest_obj.digest_length -> integer
 *
 * Returns the length of the hash value of the digest.
 *
 * This method should be overridden by each implementation subclass.
 * If not, digest_obj.digest().length() is returned.
 */
static VALUE
rb_digest_instance_digest_length(VALUE self)
{
    /* subclasses really should redefine this method */
    VALUE digest = rb_digest_instance_digest(0, 0, self);

    /* never blindly assume that #digest() returns a string */
    StringValue(digest);
    return INT2NUM(RSTRING_LEN(digest));
}