#ifndef FUTEXMGR
#define FUTEXMGR

/**
 * @file futexmgr.H
 * @brief Declaration for kernel side futex management
 */

#include <stdint.h>
#include <util/locked/list.H>
#include <kernel/spinlock.H>

struct task_t;


/**
 * @class FutexManager
 * Kernel internal management of fuxtexs
 */
class FutexManager
{
    public:

        /**
         * Put the current processes on a wait queue
         * @param[in] i_task  pointer to the current task structure
         * @param[in] i_addr  Futex address 
         * @param[in] i_val   Value that *i_addr should contain
         * @returns [0 | error code]  if *i_addr != i_val returns EWOULDBLOCK
         */
        static uint64_t wait(task_t * i_task, uint64_t * i_addr, uint64_t i_val);

        /**
         * Wakeup threads
         * @param[in] i_addr pointer to a futex
         * @param[in] i_count The max number of threads to wake
         * @returns The number of threads awoken
         */
        static uint64_t wake(uint64_t * i_addr, uint64_t i_count);

    protected:

        /**
         * Ctor
         */
        FutexManager() {};

        /**
         * Dtor
         */
        ~FutexManager() {};

    private: // functions

        /**
         * Put the current processes on a wait queue
         * @param[in] i_task  pointer to the current task structure
         * @param[in] i_addr  Futex address 
         * @param[in] i_val   Value that *i_addr should contain
         * @returns [0 | error code]  if *i_addr != i_val returns EWOULDBLOCK
         */
        uint64_t _wait(task_t * i_task, uint64_t * i_addr, uint64_t i_val);

        /**
         * Wakeup threads
         * @param[in] i_addr pointer to a futex
         * @param[in] i_count The max number of threads to wake
         * @returns The number of threads awoken
         */
        uint64_t _wake(uint64_t * i_addr, uint64_t i_count);

    private: // data

        struct _FutexWait_t
        {
            _FutexWait_t * next;    ///< next _FutexWait_t in list
            _FutexWait_t * prev;    ///< prev _FutexWait_t in list
            uint64_t * key;         ///< search key is futex address
            task_t* task;           ///< task on wait list
        };

        typedef Util::Locked::List<_FutexWait_t, uint64_t *> FutexList_t;

        Spinlock iv_lock;       ///< lock
        FutexList_t iv_list;    ///< List of waiting tasks for all futexes
};

#endif