asterisk/include/asterisk/timing.h

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008, Digium, Inc.
 *
 * Kevin P. Fleming <kpfleming@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*!
  \file timing.h
  \brief Timing source management
  \author Kevin P. Fleming <kpfleming@digium.com>

  Portions of Asterisk require a timing source, a periodic trigger
  for media handling activities. The functions in this file allow
  a loadable module to provide a timing source for Asterisk and its
  modules, so that those modules can request a 'timing handle' when
  they require one. These handles are file descriptors, which can be
  used with select() or poll().

  The timing source used by Asterisk must provide the following
  features:

  1) Periodic triggers, with a configurable interval (specified as
     number of triggers per second).

  2) Multiple outstanding triggers, each of which must be 'acked'
     to clear it. Triggers must also be 'ackable' in quantity.

  3) Continuous trigger mode, which when enabled causes every call
     to poll() on the timer handle to immediately return.

  4) Multiple 'event types', so that the code using the timer can
     know whether the wakeup it received was due to a periodic trigger
     or a continuous trigger.

  \todo Create an implementation of this API for Linux based on the
   following API: http://www.kernel.org/doc/man-pages/online/pages/man2/timerfd_create.2.html
 */

#ifndef _ASTERISK_TIMING_H
#define _ASTERISK_TIMING_H

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

enum ast_timing_event {
	AST_TIMING_EVENT_EXPIRED = 1,
	AST_TIMING_EVENT_CONTINUOUS = 2,
};

/*!
 * \brief Timing module interface
 *
 * The public API calls for the timing API directly map to this interface.
 * So, the behavior of these calls should match the documentation of the
 * public API calls.
 */
struct ast_timing_functions {
	int (*timer_open)(void);
	void (*timer_close)(int handle);
	int (*timer_set_rate)(int handle, unsigned int rate);
	void (*timer_ack)(int handle, unsigned int quantity);
	int (*timer_enable_continuous)(int handle);
	int (*timer_disable_continuous)(int handle);
	enum ast_timing_event (*timer_get_event)(int handle);
	unsigned int (*timer_get_max_rate)(int handle);
};

/*!
 * \brief Install a set of timing functions.
 *
 * \param funcs An instance of the \c ast_timing_functions structure with pointers
 *        to the functions provided by the timing implementation.
 *
 * \retval NULL failure 
 * \retval non-Null handle to be passed to ast_uninstall_timing_functions() on success
 */
void *ast_install_timing_functions(struct ast_timing_functions *funcs);

/*!
 * \brief Uninstall a previously-installed set of timing functions.
 *
 * \param handle The handle returned from a prior successful call to
 *        ast_install_timing_functions().
 *
 * \return nothing
 */
void ast_uninstall_timing_functions(void *handle);

/*!
 * \brief Open a timing fd
 *
 * \retval -1 error, with errno set
 * \retval >=0 success
 */
int ast_timer_open(void);

/*!
 * \brief Close an opened timing handle
 *
 * \param handle timing fd returned from timer_open()
 *
 * \return nothing
 */
void ast_timer_close(int handle);

/*!
 * \brief Set the timing tick rate
 *
 * \param handle timing fd returned from timer_open()
 * \param rate ticks per second, 0 turns the ticks off if needed
 *
 * Use this function if you want the timing fd to show input at a certain
 * rate.  The other alternative use of a timing fd, is using the continuous
 * mode.
 *
 * \retval -1 error, with errno set
 * \retval 0 success
 */
int ast_timer_set_rate(int handle, unsigned int rate);

/*!
 * \brief Acknowledge a timer event
 *
 * \param handle timing fd returned from timer_open()
 * \param quantity number of timer events to acknowledge
 *
 * \note This function should only be called if timer_get_event()
 *       returned AST_TIMING_EVENT_EXPIRED.
 *
 * \return nothing
 */
void ast_timer_ack(int handle, unsigned int quantity);

/*!
 * \brief Enable continuous mode
 *
 * \param handle timing fd returned from timer_open()
 *
 * Continuous mode causes poll() on the timing fd to immediately return
 * always until continuous mode is disabled.
 *
 * \retval -1 failure, with errno set
 * \retval 0 success
 */
int ast_timer_enable_continuous(int handle);

/*!
 * \brief Disable continuous mode
 *
 * \param handle timing fd returned from timer_close()
 *
 * \retval -1 failure, with errno set
 * \retval 0 success
 */
int ast_timer_disable_continuous(int handle);

/*!
 * \brief Determine timing event
 *
 * \param handle timing fd returned by timer_open()
 *
 * After poll() indicates that there is input on the timing fd, this will
 * be called to find out what triggered it.
 *
 * \return which event triggered the timing fd
 */
enum ast_timing_event ast_timer_get_event(int handle);

/*!
 * \brief Get maximum rate supported for a timing handle
 *
 * \param handle timing fd returned by timer_open()
 *
 * \return maximum rate supported for timing handle
 */
unsigned int ast_timer_get_max_rate(int handle);

#if defined(__cplusplus) || defined(c_plusplus)
}
#endif

#endif /* _ASTERISK_TIMING_H */