Updates the digest using a given
string and returns self.
The update() method and the
left-shift operator are overridden by each implementation subclass. (One
should be an alias for the other)
static VALUE
rb_digest_instance_update(VALUE self, VALUE str)
{
rb_raise(rb_eRuntimeError, "%s does not implement update()", RSTRING_PTR(rb_inspect(self)));
}
