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/*
* Copyright (C) 2013 Martin Willi
* Copyright (C) 2013 revosec AG
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*/
/**
* @defgroup watcher watcher
* @{ @ingroup processor
*/
#ifndef WATCHER_H_
#define WATCHER_H_
typedef struct watcher_t watcher_t;
typedef enum watcher_event_t watcher_event_t;
#include <library.h>
/**
* Callback function to register for file descriptor events.
*
* The callback is executed asynchronously using a thread from the pool.
* Monitoring of fd is temporarily suspended to avoid additional events while
* it is processed asynchronously. To allow concurrent events, one can quickly
* process it (using a read/write) and return from the callback. This will
* re-enable the event, while the data read can be processed in another
* asynchronous job.
*
* On Linux, even if select() marks an FD as "ready", a subsequent read/write
* can block. It is therefore highly recommended to use non-blocking I/O
* and handle EAGAIN/EWOULDBLOCK gracefully.
*
* @param data user data passed during registration
* @param fd file descriptor the event occurred on
* @param event type of event
* @return TRUE to keep watching event, FALSE to unregister fd for event
*/
typedef bool (*watcher_cb_t)(void *data, int fd, watcher_event_t event);
/**
* What events to watch for a file descriptor.
*/
enum watcher_event_t {
WATCHER_READ = (1<<0),
WATCHER_WRITE = (1<<1),
WATCHER_EXCEPT = (1<<2),
};
/**
* Watch multiple file descriptors using select().
*/
struct watcher_t {
/**
* Start watching a new file descriptor.
*
* Multiple callbacks can be registered for the same file descriptor, and
* all of them get notified. Such callbacks are executed concurrently.
*
* @param fd file descriptor to start watching
* @param events ORed set of events to watch
* @param cb callback function to invoke on events
* @param data data to pass to cb()
*/
void (*add)(watcher_t *this, int fd, watcher_event_t events,
watcher_cb_t cb, void *data);
/**
* Stop watching a previously registered file descriptor.
*
* This call blocks until any active callback for this FD returns. All
* callbacks registered for that FD get unregistered.
*
* @param fd file descriptor to stop watching
*/
void (*remove)(watcher_t *this, int fd);
/**
* Destroy a watcher_t.
*/
void (*destroy)(watcher_t *this);
};
/**
* Create a watcher instance.
*
* @return watcher
*/
watcher_t *watcher_create();
#endif /** WATCHER_H_ @}*/
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