include/asterisk/sched.h

   1 /*
   2  * Asterisk -- An open source telephony toolkit.
   3  *
   4  * Copyright (C) 1999 - 2005, Digium, Inc.
   5  *
   6  * Mark Spencer <markster@digium.com>
   7  *
   8  * See http://www.asterisk.org for more information about
   9  * the Asterisk project. Please do not directly contact
  10  * any of the maintainers of this project for assistance;
  11  * the project provides a web site, mailing lists and IRC
  12  * channels for your use.
  13  *
  14  * This program is free software, distributed under the terms of
  15  * the GNU General Public License Version 2. See the LICENSE file
  16  * at the top of the source tree.
  17  */
  18
  19 /*! \file
  20  * \brief Scheduler Routines (derived from cheops)
  21  */
  22
  23 #ifndef _ASTERISK_SCHED_H
  24 #define _ASTERISK_SCHED_H
  25
  26 #if defined(__cplusplus) || defined(c_plusplus)
  27 extern "C" {
  28 #endif
  29
  30 /*! \brief Max num of schedule structs
  31  * \note The max number of schedule structs to keep around
  32  * for use.  Undefine to disable schedule structure
  33  * caching. (Only disable this on very low memory
  34  * machines)
  35  */
  36 #define SCHED_MAX_CACHE 128
  37
  38 /*! \brief a loop construct to ensure that
  39  * the scheduled task get deleted. The idea is that
  40  * if we loop attempting to remove the scheduled task,
  41  * then whatever callback had been running will complete
  42  * and reinsert the task into the scheduler.
  43  *
  44  * Note that this is NOT always appropriate. This should
  45  * only be used for tasks whose callback may return non-zero
  46  * to indicate that the task needs to be rescheduled with the
  47  * SAME id as previously.
  48  *
  49  * Some scheduler callbacks instead may reschedule the task themselves,
  50  * thus removing the previous task id from the queue. If the task is rescheduled
  51  * in this manner, then the id for the task will be different than before
  52  * and so it makes no sense to use this macro. Note that if using the scheduler
  53  * in this manner, it is perfectly acceptable for ast_sched_del to fail, and this
  54  * macro should NOT be used.
  55  */
  56 #define AST_SCHED_DEL(sched, id) \
  57         ({ \
  58                 int _count = 0; \
  59                 int _sched_res = -1; \
  60                 while (id > -1 && (_sched_res = ast_sched_del(sched, id)) && ++_count < 10) \
  61                         usleep(1); \
  62                 if (_count == 10 && option_debug > 2) { \
  63                         ast_log(LOG_DEBUG, "Unable to cancel schedule ID %d.\n", id); \
  64                 } \
  65                 id = -1; \
  66                 (_sched_res); \
  67         })
  68
  69 struct sched_context;
  70
  71 /*! \brief New schedule context
  72  * \note Create a scheduling context
  73  * \return Returns a malloc'd sched_context structure, NULL on failure
  74  */
  75 struct sched_context *sched_context_create(void);
  76
  77 /*! \brief destroys a schedule context
  78  * Destroys (free's) the given sched_context structure
  79  * \param c Context to free
  80  * \return Returns 0 on success, -1 on failure
  81  */
  82 void sched_context_destroy(struct sched_context *c);
  83
  84 /*! \brief callback for a cheops scheduler
  85  * A cheops scheduler callback takes a pointer with callback data and
  86  * \return returns a 0 if it should not be run again, or non-zero if it should be
  87  * rescheduled to run again
  88  */
  89 typedef int (*ast_sched_cb)(const void *data);
  90 #define AST_SCHED_CB(a) ((ast_sched_cb)(a))
  91
  92 /*! \brief Adds a scheduled event
  93  * Schedule an event to take place at some point in the future.  callback
  94  * will be called with data as the argument, when milliseconds into the
  95  * future (approximately)
  96  * If callback returns 0, no further events will be re-scheduled
  97  * \param con Scheduler context to add
  98  * \param when how many milliseconds to wait for event to occur
  99  * \param callback function to call when the amount of time expires
 100  * \param data data to pass to the callback
 101  * \return Returns a schedule item ID on success, -1 on failure
 102  */
 103 int ast_sched_add(struct sched_context *con, int when, ast_sched_cb callback, const void *data);
 104
 105 /*!Adds a scheduled event with rescheduling support
 106  * \param con Scheduler context to add
 107  * \param when how many milliseconds to wait for event to occur
 108  * \param callback function to call when the amount of time expires
 109  * \param data data to pass to the callback
 110  * \param variable If true, the result value of callback function will be
 111  *       used for rescheduling
 112  * Schedule an event to take place at some point in the future.  Callback
 113  * will be called with data as the argument, when milliseconds into the
 114  * future (approximately)
 115  * If callback returns 0, no further events will be re-scheduled
 116  * \return Returns a schedule item ID on success, -1 on failure
 117  */
 118 int ast_sched_add_variable(struct sched_context *con, int when, ast_sched_cb callback, const void *data, int variable);
 119
 120 /*! \brief Deletes a scheduled event
 121  * Remove this event from being run.  A procedure should not remove its
 122  * own event, but return 0 instead.
 123  * \param con scheduling context to delete item from
 124  * \param id ID of the scheduled item to delete
 125  * \return Returns 0 on success, -1 on failure
 126  */
 127 int ast_sched_del(struct sched_context *con, int id);
 128
 129 /*! \brief Determines number of seconds until the next outstanding event to take place
 130  * Determine the number of seconds until the next outstanding event
 131  * should take place, and return the number of milliseconds until
 132  * it needs to be run.  This value is perfect for passing to the poll
 133  * call.
 134  * \param con context to act upon
 135  * \return Returns "-1" if there is nothing there are no scheduled events
 136  * (and thus the poll should not timeout)
 137  */
 138 int ast_sched_wait(struct sched_context *con);
 139
 140 /*! \brief Runs the queue
 141  * \param con Scheduling context to run
 142  * Run the queue, executing all callbacks which need to be performed
 143  * at this time.
 144  * \param con context to act upon
 145  * \return Returns the number of events processed.
 146  */
 147 int ast_sched_runq(struct sched_context *con);
 148
 149 /*! \brief Dumps the scheduler contents
 150  * Debugging: Dump the contents of the scheduler to stderr
 151  * \param con Context to dump
 152  */
 153 void ast_sched_dump(const struct sched_context *con);
 154
 155 /*! \brief Returns the number of seconds before an event takes place
 156  * \param con Context to use
 157  * \param id Id to dump
 158  */
 159 long ast_sched_when(struct sched_context *con,int id);
 160
 161 /*!
 162  * \brief Convenience macro for objects and reference (add)
 163  *
 164  */
 165 #define ast_sched_add_object(obj,con,when,callback) ast_sched_add((con),(when),(callback), ASTOBJ_REF((obj)))
 166
 167 /*!
 168  * \brief Convenience macro for objects and reference (del)
 169  *
 170  */
 171 #define ast_sched_del_object(obj,destructor,con,id) do { \
 172         if ((id) > -1) { \
 173                 ast_sched_del((con),(id)); \
 174                 (id) = -1; \
 175                 ASTOBJ_UNREF((obj),(destructor)); \
 176         } \
 177 } while(0)
 178
 179 #if defined(__cplusplus) || defined(c_plusplus)
 180 }
 181 #endif
 182
 183 #endif /* _ASTERISK_SCHED_H */