osip2 代码分析

主要类型定义：

1、osip_t

/**
 * Structure for osip handling.
 * In order to use osip, you have to manage at least one global instance
 * of an osip_t element. Then, you'll register a set of required callbacks
 * and a set of optional ones.
 * @var osip_t
 */
    typedef struct osip osip_t;

/**
 * Structure for osip handling.
 * @struct osip
 */
    struct osip {

        void *application_context;
                                /**< User defined Pointer */

        /* list of transactions for ict, ist, nict, nist */
        osip_list_t osip_ict_transactions;
                                         /**< list of ict transactions */
        osip_list_t osip_ist_transactions;
                                         /**< list of ist transactions */
        osip_list_t osip_nict_transactions;
                                         /**< list of nict transactions */
        osip_list_t osip_nist_transactions;
                                         /**< list of nist transactions */

        osip_list_t ixt_retransmissions;/**< list of ixt elements */

        osip_message_cb_t msg_callbacks[OSIP_MESSAGE_CALLBACK_COUNT];     /**@internal */
        osip_kill_transaction_cb_t kill_callbacks[OSIP_KILL_CALLBACK_COUNT];
                                                                         /**@internal */
        osip_transport_error_cb_t
            tp_error_callbacks[OSIP_TRANSPORT_ERROR_CALLBACK_COUNT];
                                                                                        /**@internal */

        int (*cb_send_message) (osip_transaction_t *, osip_message_t *, char *,
                                int, int);
                                        /**@internal */

#if defined(HAVE_DICT_DICT_H)
        dict *osip_ict_hastable;          /**< htable of ict transactions */
        dict *osip_ist_hastable;          /**< htable of ist transactions */
        dict *osip_nict_hastable;          /**< htable of nict transactions */
        dict *osip_nist_hastable;          /**< htable of nist transactions */
#endif
    };

注意：
1、ict, ist, nict, nist是osip的四种状态机

2、osip_fsm_type_t

/**
 * Enumeration for transaction type.
 * A transaction can be either of:
 *  ICT,
 *  IST,
 *  NICT,
 *  NIST,
 */
    typedef enum osip_fsm_type_t {
        ICT,
         /**< Invite Client (outgoing) Transaction */
        IST,
         /**< Invite Server (incoming) Transaction */
        NICT,
         /**< Non-Invite Client (outgoing) Transaction */
        NIST
         /**< Non-Invite Server (incoming) Transaction */
    } osip_fsm_type_t;

主要函数定义：

1、osip 4中状态机ict, ist, nict, nist事务处理核心函数osip_*_execute：

/**
 * Consume ALL pending osip_event_t previously added in the fifos of ict transactions.
 * @param osip The element to work on.
 */
    int osip_ict_execute(osip_t * osip);
/**
 * Consume ALL pending osip_event_t previously added in the fifos of ist transactions.
 * @param osip The element to work on.
 */
    int osip_ist_execute(osip_t * osip);
/**
 * Consume ALL pending osip_event_t previously added in the fifos of nict transactions.
 * @param osip The element to work on.
 */
    int osip_nict_execute(osip_t * osip);
/**
 * Consume ALL pending osip_event_t previously added in the fifos of nist transactions.
 * @param osip The element to work on.
 */
    int osip_nist_execute(osip_t * osip);

2、osip_timers_gettimeout

/**
 * Retreive the minimum timer value to be used by an application
 * so that the osip_timer_*_execute method don't have to be called
 * often.
 * 
 * @param osip The element to work on.
 * @param lower_tv The minimum timer when the application should wake up.
 */
    void osip_timers_gettimeout(osip_t * osip, struct timeval *lower_tv);

3、osip_timers_*_execute

/**
 * Check if an ict transactions needs a timer event.
 * @param osip The element to work on.
 */
    void osip_timers_ict_execute(osip_t * osip);
/**
 * Check if an ist transactions needs a timer event.
 * @param osip The element to work on.
 */
    void osip_timers_ist_execute(osip_t * osip);
/**
 * Check if a nict transactions needs a timer event.
 * @param osip The element to work on.
 */
    void osip_timers_nict_execute(osip_t * osip);
/**
 * Check if a nist transactions needs a timer event.
 * @param osip The element to work on.
 */
    void osip_timers_nist_execute(osip_t * osip);

osip_fsm_type_t