topic_alias_recv.hpp

// Copyright Takatoshi Kondo 2020
//
// 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(ASYNC_MQTT_UTIL_TOPIC_ALIAS_RECV_HPP)
#define ASYNC_MQTT_UTIL_TOPIC_ALIAS_RECV_HPP
 
#include <string>
#include <string_view>
#include <unordered_map>
#include <array>
 
#include <boost/assert.hpp>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/key.hpp>
 
#include <async_mqtt/util/log.hpp>
#include <async_mqtt/util/move.hpp>
#include <async_mqtt/packet/property.hpp>
 
namespace async_mqtt {
 
namespace mi = boost::multi_index;
 
class topic_alias_recv {
public:
    explicit topic_alias_recv(topic_alias_type max)
        :max_{max} {}
 
    void insert_or_update(std::string_view topic, topic_alias_type alias) {
        ASYNC_MQTT_LOG("mqtt_impl", trace)
            << ASYNC_MQTT_ADD_VALUE(address, this)
            << "topic_alias_recv insert"
            << " topic:" << topic
            << " alias:" << alias;
        BOOST_ASSERT(!topic.empty() && alias >= min_ && alias <= max_);
        auto it = aliases_.lower_bound(alias);
        if (it == aliases_.end() || it->alias != alias) {
            aliases_.emplace_hint(it, std::string(topic), alias);
        }
        else {
            aliases_.modify(
                it,
                [&](entry& e) {
                    e.topic = std::string{topic};
                },
                [](auto&) { BOOST_ASSERT(false); }
            );
        }
    }
 
    std::string find(topic_alias_type alias) const {
        if (alias >= min_ && alias <= max_) {
            std::string topic;
            auto it = aliases_.find(alias);
            if (it != aliases_.end()) topic = it->topic;
 
            ASYNC_MQTT_LOG("mqtt_impl", info)
                << ASYNC_MQTT_ADD_VALUE(address, this)
                << "find_topic_by_alias"
                << " alias:" << alias
                << " topic:" << topic;
 
            return topic;
        }
        return std::string{};
    }
 
    void clear() {
        ASYNC_MQTT_LOG("mqtt_impl", info)
            << ASYNC_MQTT_ADD_VALUE(address, this)
            << "clear_topic_alias";
        aliases_.clear();
    }
 
    topic_alias_type max() const { return max_; }
 
private:
    static constexpr topic_alias_type min_ = 1;
    topic_alias_type max_;
 
    struct entry {
        entry(std::string topic, topic_alias_type alias)
            : topic{force_move(topic)}, alias{alias} {}
 
        std::string topic;
        topic_alias_type alias;
    };
    using mi_topic_alias = mi::multi_index_container<
        entry,
        mi::indexed_by<
            mi::ordered_unique<
                mi::key<&entry::alias>
            >
        >
    >;
 
    mi_topic_alias aliases_;
};
 
} // namespace async_mqtt
 
#endif // ASYNC_MQTT_UTIL_TOPIC_ALIAS_RECV_HPP