source: trunk/www.guidonia.net/wp/wp-includes/cron.php@ 44

<?php
/**
 * WordPress CRON API
 *
 * @package WordPress
 */

/**
 * Schedules a hook to run only once.
 *
 * Schedules a hook which will be executed once by the Wordpress actions core at
 * a time which you specify. The action will fire off when someone visits your
 * WordPress site, if the schedule time has passed.
 *
 * @since 2.1.0
 * @link http://codex.wordpress.org/Function_Reference/wp_schedule_single_event
 *
 * @param int $timestamp Timestamp for when to run the event.
 * @param string $hook Action hook to execute when cron is run.
 * @param array $args Optional. Arguments to pass to the hook's callback function.
 */
function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
        // don't schedule a duplicate if there's already an identical event due in the next 10 minutes
        $next = wp_next_scheduled($hook, $args);
        if ( $next && $next <= $timestamp + 600 )
                return;

        $crons = _get_cron_array();
        $key = md5(serialize($args));
        $crons[$timestamp][$hook][$key] = array( 'schedule' => false, 'args' => $args );
        uksort( $crons, "strnatcasecmp" );
        _set_cron_array( $crons );
}

/**
 * Schedule a periodic event.
 *
 * Schedules a hook which will be executed by the WordPress actions core on a
 * specific interval, specified by you. The action will trigger when someone
 * visits your WordPress site, if the scheduled time has passed.
 *
 * Valid values for the recurrence are hourly, daily and twicedaily.  These can
 * be extended using the cron_schedules filter in wp_get_schedules().
 *
 * @since 2.1.0
 *
 * @param int $timestamp Timestamp for when to run the event.
 * @param string $recurrence How often the event should recur.
 * @param string $hook Action hook to execute when cron is run.
 * @param array $args Optional. Arguments to pass to the hook's callback function.
 * @return bool|null False on failure, null when complete with scheduling event.
 */
function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array()) {
        $crons = _get_cron_array();
        $schedules = wp_get_schedules();
        $key = md5(serialize($args));
        if ( !isset( $schedules[$recurrence] ) )
                return false;
        $crons[$timestamp][$hook][$key] = array( 'schedule' => $recurrence, 'args' => $args, 'interval' => $schedules[$recurrence]['interval'] );
        uksort( $crons, "strnatcasecmp" );
        _set_cron_array( $crons );
}

/**
 * Reschedule a recurring event.
 *
 * @since 2.1.0
 *
 * @param int $timestamp Timestamp for when to run the event.
 * @param string $recurrence How often the event should recur.
 * @param string $hook Action hook to execute when cron is run.
 * @param array $args Optional. Arguments to pass to the hook's callback function.
 * @return bool|null False on failure. Null when event is rescheduled.
 */
function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array()) {
        $crons = _get_cron_array();
        $schedules = wp_get_schedules();
        $key = md5(serialize($args));
        $interval = 0;

        // First we try to get it from the schedule
        if ( 0 == $interval )
                $interval = $schedules[$recurrence]['interval'];
        // Now we try to get it from the saved interval in case the schedule disappears
        if ( 0 == $interval )
                $interval = $crons[$timestamp][$hook][$key]['interval'];
        // Now we assume something is wrong and fail to schedule
        if ( 0 == $interval )
                return false;

        $now = time();

    if ( $timestamp >= $now )
        $timestamp = $now + $interval;
    else
        $timestamp = $now + ($interval - (($now - $timestamp) % $interval));

        wp_schedule_event( $timestamp, $recurrence, $hook, $args );
}

/**
 * Unschedule a previously scheduled cron job.
 *
 * The $timestamp and $hook parameters are required, so that the event can be
 * identified.
 *
 * @since 2.1.0
 *
 * @param int $timestamp Timestamp for when to run the event.
 * @param string $hook Action hook, the execution of which will be unscheduled.
 * @param array $args Arguments to pass to the hook's callback function.
 * Although not passed to a callback function, these arguments are used
 * to uniquely identify the scheduled event, so they should be the same
 * as those used when originally scheduling the event.
 */
function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
        $crons = _get_cron_array();
        $key = md5(serialize($args));
        unset( $crons[$timestamp][$hook][$key] );
        if ( empty($crons[$timestamp][$hook]) )
                unset( $crons[$timestamp][$hook] );
        if ( empty($crons[$timestamp]) )
                unset( $crons[$timestamp] );
        _set_cron_array( $crons );
}

/**
 * Unschedule all cron jobs attached to a specific hook.
 *
 * @since 2.1.0
 *
 * @param string $hook Action hook, the execution of which will be unscheduled.
 * @param mixed $args,... Optional. Event arguments.
 */
function wp_clear_scheduled_hook( $hook ) {
        $args = array_slice( func_get_args(), 1 );

        while ( $timestamp = wp_next_scheduled( $hook, $args ) )
                wp_unschedule_event( $timestamp, $hook, $args );
}

/**
 * Retrieve the next timestamp for a cron event.
 *
 * @since 2.1.0
 *
 * @param string $hook Action hook to execute when cron is run.
 * @param array $args Optional. Arguments to pass to the hook's callback function.
 * @return bool|int The UNIX timestamp of the next time the scheduled event will occur.
 */
function wp_next_scheduled( $hook, $args = array() ) {
        $crons = _get_cron_array();
        $key = md5(serialize($args));
        if ( empty($crons) )
                return false;
        foreach ( $crons as $timestamp => $cron ) {
                if ( isset( $cron[$hook][$key] ) )
                        return $timestamp;
        }
        return false;
}

/**
 * Send request to run cron through HTTP request that doesn't halt page loading.
 *
 * @since 2.1.0
 *
 * @return null Cron could not be spawned, because it is not needed to run.
 */
function spawn_cron( $local_time = 0 ) {

        if ( !$local_time )
                $local_time = time();

        if ( defined('DOING_CRON') || isset($_GET['doing_wp_cron']) )
                return;

        /*
         * do not even start the cron if local server timer has drifted
         * such as due to power failure, or misconfiguration
         */
        $timer_accurate = check_server_timer( $local_time );
        if ( !$timer_accurate )
                return;

        /*
        * multiple processes on multiple web servers can run this code concurrently
        * try to make this as atomic as possible by setting doing_cron switch
        */
        $flag = get_transient('doing_cron');

        if ( $flag > $local_time + 10*60 )
                $flag = 0;

        // don't run if another process is currently running it or more than once every 60 sec.
        if ( $flag + 60 > $local_time )
                return;

        //sanity check
        $crons = _get_cron_array();
        if ( !is_array($crons) )
                return;

        $keys = array_keys( $crons );
        if ( isset($keys[0]) && $keys[0] > $local_time )
                return;

        if ( defined('ALTERNATE_WP_CRON') && ALTERNATE_WP_CRON ) {
                if ( !empty($_POST) || defined('DOING_AJAX') )
                        return;

                set_transient( 'doing_cron', $local_time );

                ob_start();
                wp_redirect( add_query_arg('doing_wp_cron', '', stripslashes($_SERVER['REQUEST_URI'])) );
                echo ' ';

                // flush any buffers and send the headers
                while ( @ob_end_flush() );
                flush();

                @include_once(ABSPATH . 'wp-cron.php');
                return;
        }

        set_transient( 'doing_cron', $local_time );

        $cron_url = get_option( 'siteurl' ) . '/wp-cron.php?doing_wp_cron';
        wp_remote_post( $cron_url, array('timeout' => 0.01, 'blocking' => false, 'sslverify' => apply_filters('https_local_ssl_verify', true)) );
}

/**
 * Run scheduled callbacks or spawn cron for all scheduled events.
 *
 * @since 2.1.0
 *
 * @return null When doesn't need to run Cron.
 */
function wp_cron() {

        // Prevent infinite loops caused by lack of wp-cron.php
        if ( strpos($_SERVER['REQUEST_URI'], '/wp-cron.php') !== false || ( defined('DISABLE_WP_CRON') && DISABLE_WP_CRON ) )
                return;

        if ( false === $crons = _get_cron_array() )
                return;

        $local_time = time();
        $keys = array_keys( $crons );
        if ( isset($keys[0]) && $keys[0] > $local_time )
                return;

        $schedules = wp_get_schedules();
        foreach ( $crons as $timestamp => $cronhooks ) {
                if ( $timestamp > $local_time ) break;
                foreach ( (array) $cronhooks as $hook => $args ) {
                        if ( isset($schedules[$hook]['callback']) && !call_user_func( $schedules[$hook]['callback'] ) )
                                continue;
                        spawn_cron( $local_time );
                        break 2;
                }
        }
}

/**
 * Retrieve supported and filtered Cron recurrences.
 *
 * The supported recurrences are 'hourly' and 'daily'. A plugin may add more by
 * hooking into the 'cron_schedules' filter. The filter accepts an array of
 * arrays. The outer array has a key that is the name of the schedule or for
 * example 'weekly'. The value is an array with two keys, one is 'interval' and
 * the other is 'display'.
 *
 * The 'interval' is a number in seconds of when the cron job should run. So for
 * 'hourly', the time is 3600 or 60*60. For weekly, the value would be
 * 60*60*24*7 or 604800. The value of 'interval' would then be 604800.
 *
 * The 'display' is the description. For the 'weekly' key, the 'display' would
 * be <code>__('Once Weekly')</code>.
 *
 * For your plugin, you will be passed an array. you can easily add your
 * schedule by doing the following.
 * <code>
 * // filter parameter variable name is 'array'
 *      $array['weekly'] = array(
 *              'interval' => 604800,
 *              'display' => __('Once Weekly')
 *      );
 * </code>
 *
 * @since 2.1.0
 *
 * @return array
 */
function wp_get_schedules() {
        $schedules = array(
                'hourly' => array( 'interval' => 3600, 'display' => __('Once Hourly') ),
                'twicedaily' => array( 'interval' => 43200, 'display' => __('Twice Daily') ),
                'daily' => array( 'interval' => 86400, 'display' => __('Once Daily') ),
        );
        return array_merge( apply_filters( 'cron_schedules', array() ), $schedules );
}

/**
 * Retrieve Cron schedule for hook with arguments.
 *
 * @since 2.1.0
 *
 * @param string $hook Action hook to execute when cron is run.
 * @param array $args Optional. Arguments to pass to the hook's callback function.
 * @return string|bool False, if no schedule. Schedule on success.
 */
function wp_get_schedule($hook, $args = array()) {
        $crons = _get_cron_array();
        $key = md5(serialize($args));
        if ( empty($crons) )
                return false;
        foreach ( $crons as $timestamp => $cron ) {
                if ( isset( $cron[$hook][$key] ) )
                        return $cron[$hook][$key]['schedule'];
        }
        return false;
}

//
// Private functions
//

/**
 * Retrieve cron info array option.
 *
 * @since 2.1.0
 * @access private
 *
 * @return array CRON info array.
 */
function _get_cron_array()  {
        $cron = get_option('cron');
        if ( ! is_array($cron) )
                return false;

        if ( !isset($cron['version']) )
                $cron = _upgrade_cron_array($cron);

        unset($cron['version']);

        return $cron;
}

/**
 * Updates the CRON option with the new CRON array.
 *
 * @since 2.1.0
 * @access private
 *
 * @param array $cron Cron info array from {@link _get_cron_array()}.
 */
function _set_cron_array($cron) {
        $cron['version'] = 2;
        update_option( 'cron', $cron );
}

/**
 * Upgrade a Cron info array.
 *
 * This function upgrades the Cron info array to version 2.
 *
 * @since 2.1.0
 * @access private
 *
 * @param array $cron Cron info array from {@link _get_cron_array()}.
 * @return array An upgraded Cron info array.
 */
function _upgrade_cron_array($cron) {
        if ( isset($cron['version']) && 2 == $cron['version'])
                return $cron;

        $new_cron = array();

        foreach ( (array) $cron as $timestamp => $hooks) {
                foreach ( (array) $hooks as $hook => $args ) {
                        $key = md5(serialize($args['args']));
                        $new_cron[$timestamp][$hook][$key] = $args;
                }
        }

        $new_cron['version'] = 2;
        update_option( 'cron', $new_cron );
        return $new_cron;
}

// stub for checking server timer accuracy, using outside standard time sources
function check_server_timer( $local_time ) {
        return true;
}

?>