source: branches/samba-3.5.x/lib/tevent/tevent_timed.c

/* 
   Unix SMB/CIFS implementation.

   common events code for timed events

   Copyright (C) Andrew Tridgell        2003-2006
   Copyright (C) Stefan Metzmacher      2005-2009

     ** NOTE! The following LGPL license applies to the tevent
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/time.h"
#include "tevent.h"
#include "tevent_internal.h"
#include "tevent_util.h"

/**
  compare two timeval structures. 
  Return -1 if tv1 < tv2
  Return 0 if tv1 == tv2
  Return 1 if tv1 > tv2
*/
int tevent_timeval_compare(const struct timeval *tv1, const struct timeval *tv2)
{
        if (tv1->tv_sec  > tv2->tv_sec)  return 1;
        if (tv1->tv_sec  < tv2->tv_sec)  return -1;
        if (tv1->tv_usec > tv2->tv_usec) return 1;
        if (tv1->tv_usec < tv2->tv_usec) return -1;
        return 0;
}

/**
  return a zero timeval
*/
struct timeval tevent_timeval_zero(void)
{
        struct timeval tv;
        tv.tv_sec = 0;
        tv.tv_usec = 0;
        return tv;
}

/**
  return a timeval for the current time
*/
struct timeval tevent_timeval_current(void)
{
        struct timeval tv;
        gettimeofday(&tv, NULL);
        return tv;
}

/**
  return a timeval struct with the given elements
*/
struct timeval tevent_timeval_set(uint32_t secs, uint32_t usecs)
{
        struct timeval tv;
        tv.tv_sec = secs;
        tv.tv_usec = usecs;
        return tv;
}

/**
  return the difference between two timevals as a timeval
  if tv1 comes after tv2, then return a zero timeval
  (this is *tv2 - *tv1)
*/
struct timeval tevent_timeval_until(const struct timeval *tv1,
                                    const struct timeval *tv2)
{
        struct timeval t;
        if (tevent_timeval_compare(tv1, tv2) >= 0) {
                return tevent_timeval_zero();
        }
        t.tv_sec = tv2->tv_sec - tv1->tv_sec;
        if (tv1->tv_usec > tv2->tv_usec) {
                t.tv_sec--;
                t.tv_usec = 1000000 - (tv1->tv_usec - tv2->tv_usec);
        } else {
                t.tv_usec = tv2->tv_usec - tv1->tv_usec;
        }
        return t;
}

/**
  return true if a timeval is zero
*/
bool tevent_timeval_is_zero(const struct timeval *tv)
{
        return tv->tv_sec == 0 && tv->tv_usec == 0;
}

struct timeval tevent_timeval_add(const struct timeval *tv, uint32_t secs,
                                  uint32_t usecs)
{
        struct timeval tv2 = *tv;
        tv2.tv_sec += secs;
        tv2.tv_usec += usecs;
        tv2.tv_sec += tv2.tv_usec / 1000000;
        tv2.tv_usec = tv2.tv_usec % 1000000;

        return tv2;
}

/**
  return a timeval in the future with a specified offset
*/
struct timeval tevent_timeval_current_ofs(uint32_t secs, uint32_t usecs)
{
        struct timeval tv = tevent_timeval_current();
        return tevent_timeval_add(&tv, secs, usecs);
}

/*
  destroy a timed event
*/
static int tevent_common_timed_destructor(struct tevent_timer *te)
{
        tevent_debug(te->event_ctx, TEVENT_DEBUG_TRACE,
                     "Destroying timer event %p \"%s\"\n",
                     te, te->handler_name);

        if (te->event_ctx) {
                DLIST_REMOVE(te->event_ctx->timer_events, te);
        }

        return 0;
}

static int tevent_common_timed_deny_destructor(struct tevent_timer *te)
{
        return -1;
}

/*
  add a timed event
  return NULL on failure (memory allocation error)
*/
struct tevent_timer *tevent_common_add_timer(struct tevent_context *ev, TALLOC_CTX *mem_ctx,
                                             struct timeval next_event,
                                             tevent_timer_handler_t handler,
                                             void *private_data,
                                             const char *handler_name,
                                             const char *location)
{
        struct tevent_timer *te, *last_te, *cur_te;

        te = talloc(mem_ctx?mem_ctx:ev, struct tevent_timer);
        if (te == NULL) return NULL;

        te->event_ctx           = ev;
        te->next_event          = next_event;
        te->handler             = handler;
        te->private_data        = private_data;
        te->handler_name        = handler_name;
        te->location            = location;
        te->additional_data     = NULL;

        /* keep the list ordered */
        last_te = NULL;
        for (cur_te = ev->timer_events; cur_te; cur_te = cur_te->next) {
                /* if the new event comes before the current one break */
                if (tevent_timeval_compare(&te->next_event, &cur_te->next_event) < 0) {
                        break;
                }

                last_te = cur_te;
        }

        DLIST_ADD_AFTER(ev->timer_events, te, last_te);

        talloc_set_destructor(te, tevent_common_timed_destructor);

        tevent_debug(ev, TEVENT_DEBUG_TRACE,
                     "Added timed event \"%s\": %p\n",
                     handler_name, te);
        return te;
}

/*
  do a single event loop using the events defined in ev

  return the delay untill the next timed event,
  or zero if a timed event was triggered
*/
struct timeval tevent_common_loop_timer_delay(struct tevent_context *ev)
{
        struct timeval current_time = tevent_timeval_zero();
        struct tevent_timer *te = ev->timer_events;

        if (!te) {
                /* have a default tick time of 30 seconds. This guarantees
                   that code that uses its own timeout checking will be
                   able to proceeed eventually */
                return tevent_timeval_set(30, 0);
        }

        /*
         * work out the right timeout for the next timed event
         *
         * avoid the syscall to gettimeofday() if the timed event should
         * be triggered directly
         *
         * if there's a delay till the next timed event, we're done
         * with just returning the delay
         */
        if (!tevent_timeval_is_zero(&te->next_event)) {
                struct timeval delay;

                current_time = tevent_timeval_current();

                delay = tevent_timeval_until(&current_time, &te->next_event);
                if (!tevent_timeval_is_zero(&delay)) {
                        return delay;
                }
        }

        /*
         * ok, we have a timed event that we'll process ...
         */

        /* deny the handler to free the event */
        talloc_set_destructor(te, tevent_common_timed_deny_destructor);

        /* We need to remove the timer from the list before calling the
         * handler because in a semi-async inner event loop called from the
         * handler we don't want to come across this event again -- vl */
        DLIST_REMOVE(ev->timer_events, te);

        /*
         * If the timed event was registered for a zero current_time,
         * then we pass a zero timeval here too! To avoid the
         * overhead of gettimeofday() calls.
         *
         * otherwise we pass the current time
         */
        te->handler(ev, te, current_time, te->private_data);

        /* The destructor isn't necessary anymore, we've already removed the
         * event from the list. */
        talloc_set_destructor(te, NULL);

        tevent_debug(te->event_ctx, TEVENT_DEBUG_TRACE,
                     "Ending timer event %p \"%s\"\n",
                     te, te->handler_name);

        talloc_free(te);

        return tevent_timeval_zero();
}