open_source / mqtt-cpp

/* Copyright (C) 2019
 *
 * This file is part of the osdev components suite
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
 */
#ifndef OSDEV_COMPONENTS_MQTT_UTILS_H
#define OSDEV_COMPONENTS_MQTT_UTILS_H

// std
#include <algorithm>
#include <functional>
#include <memory>
#include <vector>

namespace osdev {
namespace components {
namespace mqtt {

/**
 * @brief Does nothing.
 * Utility template function to explicitly use parameters, that would otherwise be unused.
 * This helps to prevent the -Wunused-parameter warning.
 */
template <typename... Args>
void apply_unused_parameters(const Args&...)
{
}

/**
 * @brief Converts (dynamic_cast) a std::unique_ptr from TFrom to TTo.
 * @param from The std::unique_ptr to convert from TFrom to TTo.
 * @return The converted std::unique_ptr.
 */
template <typename TTo, typename TFrom>
std::unique_ptr<TTo> dynamic_unique_ptr_cast(std::unique_ptr<TFrom>&& from)
{
    auto to = dynamic_cast<TTo*>(from.get());
    if (nullptr == to) {
        return std::unique_ptr<TTo>(nullptr);
    }

    from.release();
    return std::unique_ptr<TTo>(to);
}

/**
 * @brief Converts (dynamic_cast) a std::unique_ptr from TFrom to TTo.
 * @param from The std::unique_ptr to convert from TFrom to TTo.
 * @return The converted std::unique_ptr.
 */
template <typename TTo, typename TFrom, typename TDeleter>
std::unique_ptr<TTo, TDeleter> dynamic_unique_ptr_cast(std::unique_ptr<TFrom, TDeleter>&& from)
{
    auto to = dynamic_cast<TTo*>(from.get());
    if (nullptr == to) {
        return std::unique_ptr<TTo, TDeleter>(nullptr, from.get_deleter());
    }

    from.release();
    return std::unique_ptr<TTo, TDeleter>(to, std::move(from.get_deleter()));
}

/**
 * @brief Helper class for iteration of keys of a map.
 */
template <typename TMap>
class KeyIterator : public TMap::iterator
{
public:
    typedef typename TMap::iterator MapIterator;
    typedef typename MapIterator::value_type::first_type KeyType;

    KeyIterator(const MapIterator& other)
        : TMap::iterator(other)
    {
    }

    KeyType& operator*()
    {
        return TMap::iterator::operator*().first;
    }
};

/**
 * @brief Helper function to get the begin KeyIterator from a map.
 */
template <typename MapType>
KeyIterator<MapType> KeyBegin(MapType& map)
{
    return KeyIterator<MapType>(map.begin());
}

/**
 * @brief Helper function to get the end KeyIterator from a map.
 */
template <typename MapType>
KeyIterator<MapType> KeyEnd(MapType& map)
{
    return KeyIterator<MapType>(map.end());
}

/**
 * @brief Helper class for iteration of keys of a const map.
 */
template <typename TMap>
class KeyConstIterator : public TMap::const_iterator
{
    typedef typename TMap::const_iterator TMapIterator;
    typedef typename TMapIterator::value_type::first_type TKeyType;

public:
    KeyConstIterator(const TMapIterator& other)
        : TMapIterator(other)
    {
    }

    const TKeyType& operator*()
    {
        return TMapIterator::operator*().first;
    }
};

/**
 * @brief Helper function to get the cbegin KeyConstIterator from a const map.
 */
template <typename TMap>
KeyConstIterator<TMap> KeyBegin(const TMap& map)
{
    return KeyConstIterator<TMap>(map.cbegin());
}

/**
 * @brief Helper function to get the cend KeyConstIterator from a const map.
 */
template <typename TMap>
KeyConstIterator<TMap> KeyEnd(const TMap& map)
{
    return KeyConstIterator<TMap>(map.cend());
}

/**
 * @brief Helper function to get the difference of the keys in two maps.
 * @param map1 The first map for which to examine the keys.
 * @param map2 The second map for which to examine the keys.
 * @return Collection of keys present in map1, but not in map2.
 * @note The types of the keys in the maps must be identical.
 */
template <typename TMap1, typename TMap2>
std::vector<typename TMap1::key_type> keyDifference(
    const TMap1& map1,
    const TMap2& map2,
    const std::function<bool(const typename TMap1::key_type& key1, const typename TMap1::key_type& key2)>& keyCompare = std::less<typename TMap1::key_type>())
{
    static_assert(std::is_same<
                      typename TMap1::key_type,
                      typename TMap2::key_type>::value,
        "Inconsistent key types.");

    typedef typename TMap1::key_type Key;
    std::vector<Key> onlyInMap1;
    std::set_difference(
        KeyBegin(map1),
        KeyEnd(map1),
        KeyBegin(map2),
        KeyEnd(map2),
        std::inserter(onlyInMap1, onlyInMap1.begin()),
        keyCompare);
    return onlyInMap1;
}

/**
 * @brief Helper function to get the intersection of the keys in two maps.
 * @param map1 The first map for which to examine the keys.
 * @param map2 The second map for which to examine the keys.
 * @return Collection of keys present in both maps.
 * @note The types of the keys in the maps must be identical.
 */
template <typename TMap1, typename TMap2>
std::vector<typename TMap1::key_type> keyIntersection(
    const TMap1& map1,
    const TMap2& map2,
    const std::function<bool(const typename TMap1::key_type& key1, const typename TMap1::key_type& key2)>& keyCompare = std::less<typename TMap1::key_type>())
{
    static_assert(std::is_same<
                      typename TMap1::key_type,
                      typename TMap2::key_type>::value,
        "Inconsistent key types.");

    typedef typename TMap1::key_type Key;
    std::vector<Key> inBothMaps;
    std::set_intersection(
        KeyBegin(map1),
        KeyEnd(map1),
        KeyBegin(map2),
        KeyEnd(map2),
        std::inserter(inBothMaps, inBothMaps.begin()),
        keyCompare);
    return inBothMaps;
}

/**
 * @brief Determine the absolute path of the binary that belongs to a process.
 * @param pid Process Id ifor which to determine the path to the binary. If pid equals -1 then the pid of the current process is used.
 * @return Absolute path to the binary.
 * @throw SystemException if call to readlink fails.
 * @throw PathException if path is to long.
 * @note Works only for processes owned by the user that is calling this function.
 */
std::string getPathToBinary(int pid = -1);

}       // End namespace mqtt
}       // End namespace components
}       // End namespace osdev

#endif  // OSDEV_COMPONENTS_MQTT_UTILS_H