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

    // this file should be included at the bottom of one of the thread kernel headers for a
    // specific platform.
    //#include "../threads.h"
    #include "auto_mutex_extension.h"
    #include "../binary_search_tree.h"
    #include "../member_function_pointer.h"
    #include "../memory_manager.h"
    #include "../queue.h"
    #include "../set.h"

    // The point of this block of code is to cause a link time error that will prevent a user
    // from compiling part of their application with DLIB_ASSERTs enabled and part with them
    // disabled since doing that would be a violation of C++'s one definition rule.
    extern "C"
    {
    #ifdef ENABLE_ASSERTS
        extern int USER_ERROR__violation_of_one_definition_rule_detected__inconsistent_use_of_DEBUG_or_ENABLE_ASSERTS_preprocessor_directives;
        inline int dlib_check_consistent_assert_usage() { USER_ERROR__violation_of_one_definition_rule_detected__inconsistent_use_of_DEBUG_or_ENABLE_ASSERTS_preprocessor_directives = 0; return 0; }
    #else
        extern int USER_ERROR__violation_of_one_definition_rule_detected__inconsistent_use_of_DEBUG_or_ENABLE_ASSERTS_preprocessor_directives_;
        inline int dlib_check_consistent_assert_usage() { USER_ERROR__violation_of_one_definition_rule_detected__inconsistent_use_of_DEBUG_or_ENABLE_ASSERTS_preprocessor_directives_ = 0; return 0; }
    #endif
        const int dlib_check_assert_helper_variable = dlib_check_consistent_assert_usage();
    }

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        namespace threads_kernel_shared
        {
            void thread_starter (
                void*
            );

            class threader
            {
                /*!
                    INITIAL VALUE
                        - pool_count == 0 and
                        - data_ready is associated with the mutex data_mutex
                        - data_empty is associated with the mutex data_mutex
                        - destructed is associated with the mutex data_mutex
                        - destruct == false
                        - total_count == 0
                        - function_pointer == 0
                        - do_not_ever_destruct == false

                    CONVENTION
                        - data_ready is associated with the mutex data_mutex
                        - data_empty is associated with the mutex data_mutex
                        - data_ready == a signaler used signal when there is new data waiting
                          to start a thread with.
                        - data_empty == a signaler used to signal when the data is now empty
                        - pool_count == the number of suspended threads in the thread pool
                        - total_count == the number of threads that are executing anywhere.  i.e.
                          pool_count + the ones that are currently running some user function.
                        - if (function_pointer != 0) then
                            - parameter == a void pointer pointing to the parameter which
                              should be used to start the next thread
                            - function_pointer == a pointer to the next function to make a
                              new thread with

                        - if (the destructor is running) then
                            - destruct == true
                        - else
                            - destruct == false

                        - thread_ids is locked by the data_mutex
                        - thread_ids == a set that contains the thread id for each thread spawned by this
                          object.
                !*/

            public:
                threader (
                );

                ~threader (
                );

                void destruct_if_ready (
                );
                /*!
                    ensures
                        - if (there are no threads currently running and we haven't set do_not_ever_destruct) then
                            - calls delete this
                        - else
                            - does nothing
                !*/

                bool create_new_thread (
                    void (*funct)(void*),
                    void* param
                );

                template <
                    typename T
                    >
                void unregister_thread_end_handler (
                    T& obj,
                    void (T::*handler)()
                )
                {
                    member_function_pointer<> mfp, junk_mfp;
                    mfp.set(obj,handler);

                    thread_id_type junk_id;

                    // find any member function pointers in the registry that point to the same
                    // thing as mfp and remove them
                    auto_mutex M(reg.m);
                    reg.reg.reset();
                    while (reg.reg.move_next())
                    {
                        while (reg.reg.current_element_valid() && reg.reg.element().value() == mfp)
                        {
                            reg.reg.remove_current_element(junk_id, junk_mfp);
                        }
                    }
                }

                template <
                    typename T
                    >
                void register_thread_end_handler (
                    T& obj,
                    void (T::*handler)()
                )
                {
                    thread_id_type id = get_thread_id();
                    member_function_pointer<> mfp;
                    mfp.set(obj,handler);

                    auto_mutex M(reg.m);
                    reg.reg.add(id,mfp);
                }

                bool is_dlib_thread (
                    thread_id_type id
                );

            private:

                friend void thread_starter (
                    void*
                );

                void call_end_handlers (
                );
                /*!
                    ensures
                        - calls the registered end handlers for the calling thread and
                          then removes them from reg.reg
                !*/

                // private data
                set<thread_id_type,memory_manager<char>::kernel_2b>::kernel_1b_c thread_ids;
                unsigned long total_count;
                void* parameter;
                void (*function_pointer)(void*);
                unsigned long pool_count;
                mutex data_mutex;           // mutex to protect the above data
                signaler data_ready;        // signaler to signal when there is new data
                signaler data_empty;        // signaler to signal when the data is empty
                bool destruct;
                signaler destructed;        // signaler to signal when a thread has ended
                bool do_not_ever_destruct;

                struct registry_type
                {
                    mutex m;
                    binary_search_tree<
                        thread_id_type,
                        member_function_pointer<>,
                        memory_manager<char>::kernel_2a
                        >::kernel_2a_c reg;
                };

                // stuff for the register_thread_end_handler
                registry_type reg;

                // restricted functions
                threader(threader&);        // copy constructor
                threader& operator=(threader&);    // assignement opertor

            };

        // ------------------------------------------------------------------------------------

            threader& thread_pool (
            );
            /*!
                ensures
                    - returns a reference to the global threader object
            !*/

        // ------------------------------------------------------------------------------------

            extern bool thread_pool_has_been_destroyed;
        }

        bool is_dlib_thread (
            thread_id_type id
        );

        bool is_dlib_thread (
        );

    // ----------------------------------------------------------------------------------------

        inline bool create_new_thread (
            void (*funct)(void*),
            void* param
        )
        {
            try
            {
                // now make this thread
                return threads_kernel_shared::thread_pool().create_new_thread(funct,param);
            }
            catch (std::bad_alloc&)
            {
                return false;
            }
        }

    // ----------------------------------------------------------------------------------------

        template <
            typename T
            >
        inline void register_thread_end_handler (
            T& obj,
            void (T::*handler)()
        )
        {
            DLIB_ASSERT(is_dlib_thread(),
                   "\tvoid register_thread_end_handler"
                << "\n\tYou can't register a thread end handler for a thread dlib didn't spawn."
                );

            threads_kernel_shared::thread_pool().register_thread_end_handler(obj,handler);
        }

    // ----------------------------------------------------------------------------------------

        template <
            typename T
            >
        inline void unregister_thread_end_handler (
            T& obj,
            void (T::*handler)()
        )
        {
            // Check if the thread pool has been destroyed and if it has then don't do anything.
            // This bool here is always true except when the program has started to terminate and
            // the thread pool object has been destroyed.  This if is here to catch other global
            // objects that have destructors that try to call unregister_thread_end_handler().
            // Without this check we get into trouble if the thread pool is destroyed before these
            // objects.
            if (threads_kernel_shared::thread_pool_has_been_destroyed == false)
                threads_kernel_shared::thread_pool().unregister_thread_end_handler(obj,handler);
        }

    // ----------------------------------------------------------------------------------------

    }

    #ifdef NO_MAKEFILE
    #include "threads_kernel_shared.cpp"
    #endif

    #endif // DLIB_THREADS_KERNEl_SHARED_