static public function get_all_coins() {
        static $data = null;
        if( $data ) {
            return $data;
        }
        $buf = self::get_raw_json();
        $data = @json_decode($buf, true);
        if( !$data ) {
            throw new \Exception("Unable to parse json: " . json_last_error_msg());
        }
        return $data;
    }