| 1234567891011121314151617181920212223242526272829303132333435363738394041 | // Copyright Takatoshi Kondo 2019//// Distributed under the Boost Software License, Version 1.0.// (See accompanying file LICENSE_1_0.txt or copy at// http://www.boost.org/LICENSE_1_0.txt)#if !defined(MQTT_PROTOCOL_VERSION_HPP)#define MQTT_PROTOCOL_VERSION_HPP#include <cstdint>#include <ostream>#include <mqtt/namespace.hpp>namespace MQTT_NS {enum class protocol_version {    undetermined  = 0,    v3_1_1        = 4,    v5            = 5,};constexpr char const* protocol_version_to_str(protocol_version v) {    switch(v) {    case protocol_version::undetermined: return "undetermined";    case protocol_version::v3_1_1: return "v3_1_1";    case protocol_version::v5: return "v5";    default: return "unknown_protocol_version";    }}inlinestd::ostream& operator<<(std::ostream& os, protocol_version val){    os << protocol_version_to_str(val);    return os;}} // namespace MQTT_NS#endif // MQTT_PROTOCOL_VERSION_HPP
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