lmdbal/src/serializer/serializer.hpp

/*
 * LMDB Abstraction Layer.
 * Copyright (C) 2023  Yury Gubich <blue@macaw.me>
 *
 * 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 3 of the License, 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, see <http://www.gnu.org/licenses/>.
 */

#ifndef LMDBAL_SERIALIZER_HPP
#define LMDBAL_SERIALIZER_HPP

#include "serializer.h"

/**
 * \class LMDBAL::Serializer
 * \brief A class handling serialization/deserialization
 *
 * A class that is constructed in every LMDBAL::Storage
 * to serialize or deserialize keys and values.
 *
 * It serializes to and deserializes from <a class="el" href="http://www.lmdb.tech/doc/group__mdb.html#structMDB__val">MDB_val</a>
 *
 * \tparam K type of the keys of the storage
 * \tparam V type of the values of the storage
 */

/**
 * \brief Creates an empty Serializer
 */
template<class T>
LMDBAL::Serializer<T>::Serializer() :
    bytes(),
    buffer(&bytes),
    stream(&buffer)
{
    buffer.open(QIODevice::ReadWrite);
}

/**
 * \brief Creates a Serializer with some data in it
 *
 * The data automatically gets serialized
 *
 * \param[in]   value   - a value that is assigned to the serializer
 */
template<class T>
LMDBAL::Serializer<T>::Serializer(const T& value) :
    bytes(),
    buffer(&bytes),
    stream(&buffer)
{
    buffer.open(QIODevice::ReadWrite);
    _setData(value);
}

/**
 * \brief Destoys the serializer
 */
template<class T>
LMDBAL::Serializer<T>::~Serializer() {
    buffer.close();
}

/**
 * \brief Sets the data to the seriazer
 *
 * This is a normal way to seriaze value
 *
 * \param[in]   value   - a value you want to serialize
 *
 * \returns serialized value
 */
template<class T>
MDB_val LMDBAL::Serializer<T>::setData(const T& value) {
    clear();
    _setData(value);
    return getData();
}

/**
 * \brief Deserializes value
 *
 * This is a normal way to deseriaze value
 *
 * \param[in]   value   - a value you want to deserialize
 *
 * \returns deserialized value
 */
template<class T>
T LMDBAL::Serializer<T>::deserialize(const MDB_val& value) {
    T result;
    deserialize(value, result);

    return result;
}

/**
 * \brief Deserializes value
 *
 * This is a normal way to deseriaze value
 *
 * \param[in]   value   - a value you want to deserialize
 * \param[out]  result  - deserialized value
 */
template<class T>
void LMDBAL::Serializer<T>::deserialize(const MDB_val& value, T& result) {
    clear();
    bytes.setRawData((char*)value.mv_data, value.mv_size);
    stream >> result;
}

/**
 * \brief Private function that handles serialization
 *
 * \param[in]   value   - a value you want to serialize
 */
template<class T>
void LMDBAL::Serializer<T>::_setData(const T& value) {
    stream << value;
}

/**
 * \brief Clears the state of serializer
 *
 * Normally you don't need to call this function
 */
template<class T>
void LMDBAL::Serializer<T>::clear() {
    if (buffer.pos() > 0) {
        buffer.seek(0);
    }
}

/**
 * \brief Returns the data if it already was serialized
 *
 * Normally you don't need to call this function
 *
 * This may be usefull if you called LMDBAL::Serilizer::setData() but lost the result
 *
 * \returns Serialized data
 */
template<class T>
MDB_val LMDBAL::Serializer<T>::getData() {
    MDB_val val;

    val.mv_size = buffer.pos();
    val.mv_data = (char*)bytes.data();

    return val;
}

#endif //LMDBAL_SERIALIZER_HPP