Chapter 25. Amanda Event API
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Chapter 25. Amanda Event API


Mike Grupenhoff

Original text
AMANDA Core Team
<kashmir@munge.com>

Stefan G. Weichinger

XML-conversion;Updates
AMANDA Core Team
<sgw@amanda.org>
Table of Contents


  Introduction

  The_API


        event_register

        event_release

        event_loop

        event_wait

        event_wakeup


  Data_types


        event_handle_t

        event_id_t

        event_type_t

        event_fn_t


  Event_Types


        EV_READFD

        EV_WRITEFD

        EV_SIG

        EV_TIME

        EV_WAIT



 Introduction

This is a document of the API for the event handler. The purpose of the event
handler is to allow scheduling and serialization of multiple different types of
events.

 The API


 event_register

event_handle_t *event_register(event_id_t data, event_type_t type, event_fn_t
callback, void *arg);
Sets up an event of the given type to call the given function with the given
argument.
The 'data' argument is type specific.
EV_READFD, EV_WRITEFD - the file descriptor to monitor EV_SIG - the signal
number to monitor EV_TIME - the number of seconds between each pulse EV_WAIT -
the wait identifier used with event_wakeup() EV_DEAD - internal use only

 event_release

void event_release(event_handle_t *handle);
Remove an event from the queue. This can happen at any time, even while the
event is firing.

 event_loop

void event_loop(int dontblock);
Process all pending events. If the argument is zero, this will keep running
until all events have been released. If the argument is nonzero, this will do
one pass over all pending events, and fire the ones that are immediately ready,
and then return.

 event_wait

void event_wait(event_id_t id);
Like event_loop(0), except that it will stop as soon as the event id is
serviced.

 event_wakeup

int event_wakeup(event_id_t id);
Fire all EV_WAIT events registered with an argument value of 'id' immediately.
Returns the number of events that were fired.

 Data types


 event_handle_t

This is an opaque structure that describes a registered event. It is only
useful to keep if you need to unregister the event later.

 event_id_t

This is type-specific data. The contents and format depend on on the type of
the event. This is an unsigned integral type.

 event_type_t

This is an enumerated type describing the different events we handle.

 event_fn_t

typedef void (*event_fn_t)(void *arg);
This is a function signature for the type of function that needs to get passed
to event_register. The argument to the function is a pointer of the caller's
choosing.

 Event Types


 EV_READFD

This type of event will fire when the file descriptor passed to event_register
has data waiting to be read.

 EV_WRITEFD

This type of event will fire when the file descriptor passed to event_register
can have data written to it without blocking.

 EV_SIG

This type of event will fire when the signal number passed to event_register
has been caught. Note that if a signal is caught while processing is not in
event_loop(), the event will be delayed until processing returns to event_loop
().

 EV_TIME

This type of event will fire repeatedly with a delay of the number of seconds
passed to event_register between each interval.

 EV_WAIT

This type of event will fire when someone calls event_wakeup() with the numeric
argument equal to the argument this event was registered with.

Note

Refer to http://www.amanda.org/docs/eventapi.html for the current version of
this document.
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