bimap.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2019, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */
#pragma once

#include <mrpt/core/exceptions.h>
#include <map>

namespace mrpt::containers
{
/** A bidirectional version of std::map, declared as bimap<KEY,VALUE> and which
 * actually contains two std::map's, one for keys and another for values.
 * To use this class, insert new pairs KEY<->VALUE with bimap::insert. Then,
 * you can access the KEY->VALUE map with bimap::direct(), and the VALUE->KEY
 * map with bimap::inverse(). The consistency of the two internal maps is
 * assured at any time.
 *
 * \note This class can be accessed through iterators to the map KEY->VALUE
 * only.
 * \note Both typenames KEY and VALUE must be suitable for being employed as
 * keys in a std::map, i.e. they must be comparable through a "< operator".
 * \note Defined in #include <mrpt/containers/bimap.h>
 * \ingroup mrpt_containers_grp
 */
template <typename KEY, typename VALUE>
class bimap
{
   private:
    std::map<KEY, VALUE> m_k2v;
    std::map<VALUE, KEY> m_v2k;

   public:
    using const_iterator = typename std::map<KEY, VALUE>::const_iterator;
    using iterator = typename std::map<KEY, VALUE>::iterator;
    using const_iterator_inverse =
        typename std::map<VALUE, KEY>::const_iterator;
    using iterator_inverse = typename std::map<VALUE, KEY>::iterator;

    /** Default constructor - does nothing */
    bimap() = default;
    inline const_iterator begin() const { return m_k2v.begin(); }
    inline iterator begin() { return m_k2v.begin(); }
    inline const_iterator end() const { return m_k2v.end(); }
    inline iterator end() { return m_k2v.end(); }
    inline const_iterator_inverse inverse_begin() const
    {
        return m_v2k.begin();
    }
    inline iterator_inverse inverse_begin() { return m_v2k.begin(); }
    inline const_iterator_inverse inverse_end() const { return m_v2k.end(); }
    inline iterator_inverse inverse_end() { return m_v2k.end(); }
    inline size_t size() const { return m_k2v.size(); }
    inline bool empty() const { return m_k2v.empty(); }
    /** Return a read-only reference to the internal map KEY->VALUES */
    const std::map<KEY, VALUE>& getDirectMap() const { return m_k2v; }
    /** Return a read-only reference to the internal map KEY->VALUES */
    const std::map<VALUE, KEY>& getInverseMap() const { return m_v2k; }
    /** Clear the contents of the bi-map. */
    void clear()
    {
        m_k2v.clear();
        m_v2k.clear();
    }

    /** Insert a new pair KEY<->VALUE in the bi-map */
    void insert(const KEY& k, const VALUE& v)
    {
        m_k2v[k] = v;
        m_v2k[v] = k;
    }

    /**  Get the value associated the given key, KEY->VALUE, returning false if
     * not present.
     *  \sa inverse, hasKey, hasValue
     * \return false on key not found.
     */
    bool direct(const KEY& k, VALUE& out_v) const
    {
        const_iterator i = m_k2v.find(k);
        if (i == m_k2v.end()) return false;
        out_v = i->second;
        return true;
    }

    /** Return true if the given key 'k' is in the bi-map  \sa hasValue, direct,
     * inverse */
    inline bool hasKey(const KEY& k) const
    {
        return m_k2v.find(k) != m_k2v.end();
    }
    /** Return true if the given value 'v' is in the bi-map \sa hasKey, direct,
     * inverse */
    inline bool hasValue(const VALUE& v) const
    {
        return m_v2k.find(v) != m_v2k.end();
    }

    /**  Get the value associated the given key, KEY->VALUE, raising an
     * exception if not present.
     *  \sa inverse, hasKey, hasValue
     * \exception std::exception On key not present in the bi-map.
     */
    VALUE direct(const KEY& k) const
    {
        auto i = m_k2v.find(k);
        if (i == m_k2v.end()) THROW_EXCEPTION("Key not found.");
        return i->second;
    }

    /**  Get the key associated the given value, VALUE->KEY, returning false if
     * not present.
     *  \sa direct, hasKey, hasValue
     * \return false on value not found.
     */
    bool inverse(const VALUE& v, KEY& out_k) const
    {
        const_iterator_inverse i = m_v2k.find(v);
        if (i == m_v2k.end()) return false;
        out_k = i->second;
        return true;
    }

    /**  Get the key associated the given value, VALUE->KEY, raising an
     * exception if not present.
     *  \sa direct, hasKey, hasValue
     * \return false on value not found.
     */
    KEY inverse(const VALUE& v) const
    {
        auto i = m_v2k.find(v);
        if (i == m_v2k.end()) THROW_EXCEPTION("Value not found.");
        return i->second;
    }

    inline const_iterator find_key(const KEY& k) const { return m_k2v.find(k); }
    inline iterator find_key(const KEY& k) { return m_k2v.find(k); }
    inline const_iterator_inverse find_value(const VALUE& v) const
    {
        return m_v2k.find(v);
    }
    inline iterator_inverse find_value(const VALUE& v) { return m_v2k.find(v); }
};  // end class bimap

}  // namespace mrpt::containers