    // Copyright (C) 2003  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #undef DLIB_HASH_TABLE_KERNEl_ABSTRACT_
    #ifdef DLIB_HASH_TABLE_KERNEl_ABSTRACT_

    #include "../interfaces/map_pair.h"
    #include "../general_hash/general_hash.h"
    #include "../interfaces/enumerable.h"
    #include "../interfaces/remover.h"
    #include "../serialize.h"
    #include "../algs.h"
    #include <functional>

    namespace dlib
    {

        template <
            typename domain,
            typename range,
            typename mem_manager = default_memory_manager,
            typename compare = std::less<domain>
            >
        class hash_table : public enumerable<map_pair<domain,range> >,
                           public pair_remover<domain,range>
        {

            /*!
                REQUIREMENTS ON domain
                    domain must be comparable by compare where compare is a functor compatible with std::less and
                    domain must be hashable by general_hash
                    (general_hash is defined in dlib/general_hash) and
                    domain must be swappable by a global swap() and
                    domain must have a default constructor

                REQUIREMENTS ON range
                    range must be swappable by a global swap() and
                    range must have a default constructor

                REQUIREMENTS ON mem_manager
                    must be an implementation of memory_manager/memory_manager_kernel_abstract.h or
                    must be an implementation of memory_manager_global/memory_manager_global_kernel_abstract.h or
                    must be an implementation of memory_manager_stateless/memory_manager_stateless_kernel_abstract.h
                    mem_manager::type can be set to anything.

                POINTERS AND REFERENCES TO INTERNAL DATA
                    swap(), count(), and operator[] functions do
                    not invalidate pointers or references to internal data.
                    All other functions have no such guarantee.

                INITIAL VALUE
                    size() == 0

                ENUMERATION ORDER
                    No order is specified.  Only that each element will be visited once
                    and only once.

                WHAT THIS OBJECT REPRESENTS
                    hash_table contains items of type T

                    This object represents a data dictionary that is built on top of some
                    kind of hash table.  The number of buckets in the hash table is
                    defined by the constructor argument and is some power of 2.

                    Also note that unless specified otherwise, no member functions
                    of this object throw exceptions.

                    NOTE:
                        definition of equivalent:
                        a is equivalent to b if
                        a < b == false and
                        b < a == false
            !*/

            public:

                typedef domain domain_type;
                typedef range range_type;
                typedef compare compare_type;
                typedef mem_manager mem_manager_type;

                explicit hash_table(
                    unsigned long expnum
                );
                /*!
                    requires
                        - expnum < 32
                    ensures
                        - #*this is properly initialized
                        - #*this will use 2^expnum as a suggestion for the initial number
                          of buckets.
                    throws
                        - std::bad_alloc or any exception thrown by domain's or range's
                          constructor.
                !*/

                virtual ~hash_table(
                );
                /*!
                    ensures
                        - all memory associated with *this has been released
                !*/

                void clear(
                );
                /*!
                    ensures
                        - #*this has its initial value
                    throws
                        - std::bad_alloc or any exception thrown by domain's or range's
                          constructor.
                            if this exception is thrown then *this is unusable
                            until clear() is called and succeeds
                !*/

                unsigned long count (
                    const domain& d
                ) const;
                /*!
                    ensures
                        - returns the number of elements in the domain of *this that are
                          equivalent to d
                !*/

                void add (
                    domain& d,
                    range& r
                );
                /*!
                    requires
                        - &d != &r (i.e. d and r cannot be the same variable)
                    ensures
                        - adds a mapping between d and r to *this
                        - if (count(d) == 0) then
                            - #*(*this)[d] == r
                        - else
                            - #(*this)[d] != 0
                        - #d and #r have initial values for their types
                        - #count(d) == count(d) + 1
                        - #at_start() == true
                        - #size() == size() + 1
                    throws
                        - std::bad_alloc or any exception thrown by domain's or range's
                          constructor.
                            if add() throws then it has no effect
                !*/

                void remove (
                    const domain& d,
                    domain& d_copy,
                    range& r
                );
                /*!
                    requires
                        - (*this)[d] != 0
                        - &d != &r (i.e. d and r cannot be the same variable)
                        - &d != &d_copy (i.e. d and d_copy cannot be the same variable)
                        - &r != &d_copy (i.e. r and d_copy cannot be the same variable)
                    ensures
                        - some element in the domain of *this that is equivalent to d has
                          been removed and swapped into #d_copy.  Additionally, its
                          associated range element has been removed and swapped into #r.
                        - #count(d) = count(d) - 1
                        - #size() == size() - 1
                        - #at_start() == true
                !*/

                void destroy (
                    const domain& d
                );
                /*!
                    requires
                        - (*this)[d] != 0
                    ensures
                        - an element in the domain of *this equivalent to d has been removed.
                          The element in the range of *this associated with d has also been
                          removed.
                        - #count(d) == count(d) - 1
                        - #size() == size() - 1
                        - #at_start() == true
                !*/

                const range* operator[] (
                    const domain& d
                ) const;
                /*!
                    ensures
                        - if (there is an element in the domain equivalent to d) then
                            - returns a pointer to an element in the range of *this that
                              is associated with an element in the domain of *this
                              equivalent to d.
                        - else
                            - returns 0
                !*/

                range* operator[] (
                    const domain& d
                );
                /*!
                    ensures
                        - if (there is an element in the domain equivalent to d) then
                            - returns a pointer to an element in the range of *this that
                              is associated with an element in the domain of *this
                              equivalent to d.
                        - else
                            - returns 0
                !*/

                void swap (
                    hash_table& item
                );
                /*!
                    ensures
                        - swaps *this and item
                !*/

            private:

                // restricted functions
                hash_table(hash_table&);
                hash_table& operator=(hash_table&);

        };

        template <
            typename domain,
            typename range,
            typename mem_manager
            >
        inline void swap (
            hash_table<domain,range,mem_manager>& a,
            hash_table<domain,range,mem_manager>& b
        ) { a.swap(b); }
        /*!
            provides a global swap function
        !*/

        template <
            typename domain,
            typename range,
            typename mem_manager
            >
        void deserialize (
            hash_table<domain,range,mem_manager>& item,
            std::istream& in
        );
        /*!
            provides deserialization support
        !*/
    }

    #endif // DLIB_HASH_TABLE_KERNEl_ABSTRACT_