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NAME

       globus_callback_api - Globus Callback API.

SYNOPSIS

   Convenience Macros
       #define globus_callback_poll(a)
           Poll the global callback space.
       #define globus_poll_blocking()
           Blocking poll of the global callback space.
       #define globus_poll_nonblocking()
           Nonblocking poll of the global callback space.
       #define globus_poll()
           Nonblocking poll of the global callback space.
       #define globus_signal_poll()
           Wake up callback polling thread.
       #define globus_callback_register_oneshot( callback_handle,  delay_time,  callback_func,
           callback_user_arg)
           Register a oneshot function in the global callback space.
       #define globus_callback_register_periodic( callback_handle,  delay_time,  period,
           callback_func,  callback_user_arg)
           Register a periodic function in the global callback space.
       #define globus_callback_register_signal_handler( signum,  persist,  callback_func,
           callback_user_arg)
           Register a signal handler in the global callback space.

   Callback Prototypes
       typedef void(* globus_callback_func_t) (void *user_arg)
           Globus callback prototype.

   Oneshot Callbacks
       globus_result_t globus_callback_space_register_oneshot (globus_callback_handle_t
           *callback_handle, const globus_reltime_t *delay_time, globus_callback_func_t
           callback_func, void *callback_user_arg, globus_callback_space_t space)
           Register a oneshot some delay from now.

   Periodic Callbacks
       globus_result_t globus_callback_space_register_periodic (globus_callback_handle_t
           *callback_handle, const globus_reltime_t *delay_time, const globus_reltime_t *period,
           globus_callback_func_t callback_func, void *callback_user_arg, globus_callback_space_t
           space)
           Register a periodic callback.
       globus_result_t globus_callback_unregister (globus_callback_handle_t callback_handle,
           globus_callback_func_t unregister_callback, void *unreg_arg, globus_bool_t *active)
           Unregister a callback.
       globus_result_t globus_callback_adjust_oneshot (globus_callback_handle_t callback_handle,
           const globus_reltime_t *new_delay)
           Adjust the delay of a oneshot callback.
       globus_result_t globus_callback_adjust_period (globus_callback_handle_t callback_handle,
           const globus_reltime_t *new_period)
           Adjust the period of a periodic callback.

   Callback Polling
       void globus_callback_space_poll (const globus_abstime_t *timestop, globus_callback_space_t
           space)
           Poll for ready callbacks.
       void globus_callback_signal_poll ()
           Signal the poll.

   Miscellaneous
       globus_bool_t globus_callback_get_timeout (globus_reltime_t *time_left)
           Get the amount of time left in a callback.
       globus_bool_t globus_callback_has_time_expired ()
           See if there is remaining time in a callback.
       globus_bool_t globus_callback_was_restarted ()
           See if a callback has been restarted.

Detailed Description

       Globus Callback API.

Macro Definition Documentation

   #define globus_callback_poll(a)
       Poll the global callback space. Specifies the global space for
       globus_callback_space_poll(). argument is the timeout

       See also:
           globus_callback_space_poll()

   #define globus_callback_register_oneshot(callback_handle, delay_time, callback_func,
       callback_user_arg)
       Register a oneshot function in the global callback space. Specifies the global space for
       globus_callback_space_register_oneshot() all other arguments are the same as specified
       there.

       See also:
           globus_callback_space_register_oneshot()

   #define globus_callback_register_periodic(callback_handle, delay_time, period, callback_func,
       callback_user_arg)
       Register a periodic function in the global callback space. Specifies the global space for
       globus_callback_space_register_periodic() all other arguments are the same as specified
       there.

       See also:
           globus_callback_space_register_periodic()

   #define globus_callback_register_signal_handler(signum, persist, callback_func,
       callback_user_arg)
       Register a signal handler in the global callback space. Specifies the global space for
       globus_callback_space_register_signal_handler() all other arguments are the same as
       specified there.

       See also:
           globus_callback_space_register_signal_handler()

   #define globus_poll()
       Nonblocking poll of the global callback space. Specifies that globus_callback_space_poll()
       should poll on the global space with an immediate timeout

       See also:
           globus_callback_space_poll()

   #define globus_poll_blocking()
       Blocking poll of the global callback space. Specifies that globus_callback_space_poll()
       should poll on the global space with an infinite timeout

       See also:
           globus_callback_space_poll()

   #define globus_poll_nonblocking()
       Nonblocking poll of the global callback space. Specifies that globus_callback_space_poll()
       should poll on the global space with an immediate timeout

       See also:
           globus_callback_space_poll()

   #define globus_signal_poll()
       Wake up callback polling thread. Counterpart to globus_poll().

       See also:
           globus_callback_signal_poll()

Typedef Documentation

   typedef void(* globus_callback_func_t) (void *user_arg)
       Globus callback prototype. This is the signature of the function registered with the
       globus_callback_register_* calls.

       If this is a periodic callback, it is guaranteed that the call canNOT be reentered unless
       globus_thread_blocking_space_will_block() is called (explicitly, or implicitly via
       globus_cond_wait()). Also, if globus_callback_unregister() is called to cancel this
       periodic from within this callback, it is guaranteed that the callback will NOT be
       requeued again

       If the function will block at all, the user should call globus_callback_get_timeout() to
       see how long this function can safely block or call
       globus_thread_blocking_space_will_block()

       Parameters:
           user_arg The user argument registered with this callback

       Returns:

           · void

       See also:
           globus_callback_space_register_oneshot()

           globus_callback_space_register_periodic()

           globus_thread_blocking_space_will_block()

           globus_callback_get_timeout()

Function Documentation

   globus_result_t globus_callback_adjust_oneshot (globus_callback_handle_t callback_handle,
       const globus_reltime_t * new_delay)
       Adjust the delay of a oneshot callback. This function allows a user to adjust the delay of
       a previously registered callback. It is safe to call this within or outside of the
       callback that is being modified.

       Note if the oneshot has already been fired, this function will still return
       GLOBUS_SUCCESS, but won't affect anything.

       Parameters:
           callback_handle the handle received from a globus_callback_space_register_oneshot()
           call
           new_delay The new delay from now. If NULL, then callback will be fired as soon as
           possible.

       Returns:

           · GLOBUS_CALLBACK_ERROR_INVALID_CALLBACK_HANDLE

           · GLOBUS_CALLBACK_ERROR_ALREADY_CANCELED

           · GLOBUS_SUCCESS

       See also:
           globus_callback_space_register_periodic()

   globus_result_t globus_callback_adjust_period (globus_callback_handle_t callback_handle, const
       globus_reltime_t * new_period)
       Adjust the period of a periodic callback. This function allows a user to adjust the period
       of a previously registered callback. It is safe to call this within or outside of the
       callback that is being modified.

       This func also allows a user to effectively 'suspend' a periodic callback until another
       time by passing a period of NULL. The callback can later be resumed by passing in a new
       period.

       Note that the callback will not be fired sooner than 'new_period' from now. A 'suspended'
       callback must still be unregistered to free its resources.

       Parameters:
           callback_handle the handle received from a globus_callback_space_register_periodic()
           call
           new_period The new period. If NULL or globus_i_reltime_infinity, then callback will be
           'suspended' as soon as the last running instance of it returns.

       Returns:

           · GLOBUS_CALLBACK_ERROR_INVALID_CALLBACK_HANDLE

           · GLOBUS_CALLBACK_ERROR_ALREADY_CANCELED

           · GLOBUS_SUCCESS

       See also:
           globus_callback_space_register_periodic()

   globus_bool_t globus_callback_get_timeout (globus_reltime_t * time_left)
       Get the amount of time left in a callback. This function retrieves the remaining time a
       callback is allowed to run. If a callback has already timed out, time_left will be set to
       zero and GLOBUS_TRUE returned. This function is intended to be called within a callback's
       stack, but is harmless to call anywhere (will return GLOBUS_FALSE and an infinite
       time_left)

       Parameters:
           time_left storage for the remaining time.

       Returns:

           · GLOBUS_FALSE if time remaining

           · GLOBUS_TRUE if already timed out

   globus_bool_t globus_callback_has_time_expired ()
       See if there is remaining time in a callback. This function returns GLOBUS_TRUE if the
       running time of a callback has already expired. This function is intended to be called
       within a callback's stack, but is harmless to call anywhere (will return GLOBUS_FALSE)

       Returns:

           · GLOBUS_FALSE if time remaining

           · GLOBUS_TRUE if already timed out

   void globus_callback_signal_poll ()
       Signal the poll. This function signals globus_callback_space_poll() that something has
       changed and it should return to its caller as soon as possible.

       In general, you never need to call this function directly. It is called (when necessary)
       by globus_cond_signal() or globus_cond_broadcast. The only case in which a user may wish
       to call this explicitly is if the application has no aspirations of ever being built
       threaded.

       Returns:

           · void

       See also:
           globus_callback_space_poll()

   void globus_callback_space_poll (const globus_abstime_t * timestop, globus_callback_space_t
       space)
       Poll for ready callbacks. This function is used to poll for registered callbacks.

       For non-threaded builds, callbacks are not/can not be delivered unless this is called. Any
       call to this can cause callbacks registered with the 'global' space to be fired. Whereas
       callbacks registered with a user's space will only be delivered when this is called with
       that space.

       For threaded builds, this only needs to be called to poll user spaces with behavior ==
       GLOBUS_CALLBACK_SPACE_BEHAVIOR_SINGLE. The 'global' space and other user spaces are
       constantly polled in a separate thread. (If it is called in a threaded build for these
       spaces, it will just yield its thread)

       In general, you never need to call this function directly. It is called (when necessary)
       by globus_cond_wait(). The only case in which a user may wish to call this explicitly is
       if the application has no aspirations of ever being built threaded.

       This function (when not yielding) will block up to timestop or until
       globus_callback_signal_poll() is called by one of the fired callbacks. It will always try
       and kick out ready callbacks, regardless of the timestop.

       Parameters:
           timestop The time to block until. If this is NULL or less than the cuurent time, an
           attempt to fire only ready callbacks is made (no blocking).
           space The callback space to poll. Note: regardless of what space is passed here, the
           'global' space is also always polled.

       Returns:

           · void

       See also:
           Globus Callback Spaces

           globus_condattr_setspace()

   globus_result_t globus_callback_space_register_oneshot (globus_callback_handle_t *
       callback_handle, const globus_reltime_t * delay_time, globus_callback_func_t
       callback_func, void * callback_user_arg, globus_callback_space_t space)
       Register a oneshot some delay from now. This function registers the callback_func to start
       some delay_time from now.

       Parameters:
           callback_handle Storage for a handle. This may be NULL. If it is NOT NULL, you must
           unregister the callback to reclaim resources.
           delay_time The relative time from now to fire this callback. If NULL, will fire as
           soon as possible
           callback_func the user func to call
           callback_user_arg user arg that will be passed to callback
           space The space with which to register this callback

       Returns:

           · GLOBUS_CALLBACK_ERROR_INVALID_ARGUMENT

           · GLOBUS_CALLBACK_ERROR_MEMORY_ALLOC

           · GLOBUS_SUCCESS

       See also:
           globus_callback_func_t

           Globus Callback Spaces

   globus_result_t globus_callback_space_register_periodic (globus_callback_handle_t *
       callback_handle, const globus_reltime_t * delay_time, const globus_reltime_t * period,
       globus_callback_func_t callback_func, void * callback_user_arg, globus_callback_space_t
       space)
       Register a periodic callback. This function registers a periodic callback_func to start
       some delay_time and run every period from then.

       Parameters:
           callback_handle Storage for a handle. This may be NULL. If it is NOT NULL, you must
           cancel the periodic to reclaim resources.
           delay_time The relative time from now to fire this callback. If NULL, will fire the
           first callback as soon as possible
           period The relative period of this callback
           callback_func the user func to call
           callback_user_arg user arg that will be passed to callback
           space The space with which to register this callback

       Returns:

           · GLOBUS_CALLBACK_ERROR_INVALID_ARGUMENT

           · GLOBUS_CALLBACK_ERROR_MEMORY_ALLOC

           · GLOBUS_SUCCESS

       See also:
           globus_callback_unregister()

           globus_callback_func_t

           globus_callback_spaces

   globus_result_t globus_callback_unregister (globus_callback_handle_t callback_handle,
       globus_callback_func_t unregister_callback, void * unreg_arg, globus_bool_t * active)
       Unregister a callback. This function will cancel a callback and free the resources
       associcated with the callback handle. If the callback was able to be canceled immediately
       (or if it has already run), GLOBUS_SUCCESS is returned and it is guaranteed that there are
       no running instances of the callback.

       If the callback is currently running (or unstoppably about to be run), then the callback
       is prevented from being requeued, but, the 'official' cancel is deferred until the last
       running instance of the callback returns. If you need to know when the callback is
       guaranteed to have been canceled, pass an unregister callback.

       If you would like to know if you unregistered a callback before it ran, pass storage for a
       boolean 'active'. This will be GLOBUS_TRUE if callback was running. GLOBUS_FALSE
       otherwise.

       Parameters:
           callback_handle the handle received from a globus_callback_space_register_*() call
           unregister_callback the function to call when the callback has been canceled and there
           are no running instances of it. This will be delivered to the same space used in the
           register call.
           unreg_arg user arg that will be passed to the unregister callback
           active storage for an indication of whether the callback was running when this call
           was made

       Returns:

           · GLOBUS_CALLBACK_ERROR_INVALID_CALLBACK_HANDLE

           · GLOBUS_CALLBACK_ERROR_ALREADY_CANCELED

           · GLOBUS_SUCCESS

       See also:
           globus_callback_space_register_periodic()

           globus_callback_func_t

   globus_bool_t globus_callback_was_restarted ()
       See if a callback has been restarted. If the callback is a oneshot, this merely means the
       callback called globus_thread_blocking_space_will_block (or globus_cond_wait() at some
       point.

       For a periodic, it signifies the same and also that the periodic has been requeued. This
       means that the callback function may be reentered if the period is short enough (on a
       threaded build)

       Returns:

           · GLOBUS_FALSE if not restarted

           · GLOBUS_TRUE if restarted

Author

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