src/core/common/timer.cpp

/*
 *  Copyright (c) 2016, The OpenThread Authors.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. Neither the name of the copyright holder nor the
 *     names of its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file
 *   This file implements a multiplexed timer service on top of the alarm abstraction.
 */

#include "timer.hpp"

#include "common/code_utils.hpp"
#include "common/debug.hpp"
#include "common/instance.hpp"
#include "common/locator-getters.hpp"
#include "common/logging.hpp"

namespace ot {

const TimerScheduler::AlarmApi TimerMilliScheduler::sAlarmMilliApi = {&otPlatAlarmMilliStartAt, &otPlatAlarmMilliStop,
                                                                      &otPlatAlarmMilliGetNow};

bool Timer::DoesFireBefore(const Timer &aSecondTimer, Time aNow)
{
    bool retval;
    bool isBeforeNow = (GetFireTime() < aNow);

    // Check if one timer is before `now` and the other one is not.
    if ((aSecondTimer.GetFireTime() < aNow) != isBeforeNow)
    {
        // One timer is before `now` and the other one is not, so if this timer's fire time is before `now` then
        // the second fire time would be after `now` and this timer would fire before the second timer.

        retval = isBeforeNow;
    }
    else
    {
        // Both timers are before `now` or both are after `now`. Either way the difference is guaranteed to be less
        // than `kMaxDt` so we can safely compare the fire times directly.

        retval = GetFireTime() < aSecondTimer.GetFireTime();
    }

    return retval;
}

void TimerMilli::Start(uint32_t aDelay)
{
    StartAt(GetNow(), aDelay);
}

void TimerMilli::StartAt(TimeMilli aStartTime, uint32_t aDelay)
{
    assert(aDelay <= kMaxDelay);
    FireAt(aStartTime + aDelay);
}

void TimerMilli::FireAt(TimeMilli aFireTime)
{
    mFireTime = aFireTime;
    Get<TimerMilliScheduler>().Add(*this);
}

void TimerMilli::FireAtIfEarlier(TimeMilli aFireTime)
{
    if (!IsRunning() || (mFireTime > aFireTime))
    {
        FireAt(aFireTime);
    }
}

void TimerMilli::Stop(void)
{
    Get<TimerMilliScheduler>().Remove(*this);
}

void TimerScheduler::Add(Timer &aTimer, const AlarmApi &aAlarmApi)
{
    Timer *prev = NULL;
    Time   now(aAlarmApi.AlarmGetNow());

    Remove(aTimer, aAlarmApi);

    for (Timer *cur = mTimerList.GetHead(); cur; prev = cur, cur = cur->GetNext())
    {
        if (aTimer.DoesFireBefore(*cur, now))
        {
            break;
        }
    }

    if (prev == NULL)
    {
        mTimerList.Push(aTimer);
        SetAlarm(aAlarmApi);
    }
    else
    {
        mTimerList.PushAfter(aTimer, *prev);
    }
}

void TimerScheduler::Remove(Timer &aTimer, const AlarmApi &aAlarmApi)
{
    VerifyOrExit(aTimer.IsRunning());

    if (mTimerList.GetHead() == &aTimer)
    {
        mTimerList.Pop();
        SetAlarm(aAlarmApi);
    }
    else
    {
        mTimerList.Remove(aTimer);
    }

    aTimer.SetNext(&aTimer);

exit:
    return;
}

void TimerScheduler::SetAlarm(const AlarmApi &aAlarmApi)
{
    if (mTimerList.IsEmpty())
    {
        aAlarmApi.AlarmStop(&GetInstance());
    }
    else
    {
        Timer *  timer = mTimerList.GetHead();
        Time     now(aAlarmApi.AlarmGetNow());
        uint32_t remaining;

        remaining = (now < timer->mFireTime) ? (timer->mFireTime - now) : 0;

        aAlarmApi.AlarmStartAt(&GetInstance(), now.GetValue(), remaining);
    }
}

void TimerScheduler::ProcessTimers(const AlarmApi &aAlarmApi)
{
    Timer *timer = mTimerList.GetHead();

    if (timer)
    {
        Time now(aAlarmApi.AlarmGetNow());

        if (now >= timer->mFireTime)
        {
            Remove(*timer, aAlarmApi); // `Remove()` will `SetAlarm` for next timer if there is any.
            timer->Fired();
            ExitNow();
        }
    }

    SetAlarm(aAlarmApi);

exit:
    return;
}

extern "C" void otPlatAlarmMilliFired(otInstance *aInstance)
{
    Instance *instance = static_cast<Instance *>(aInstance);

    VerifyOrExit(otInstanceIsInitialized(aInstance));
    instance->Get<TimerMilliScheduler>().ProcessTimers();

exit:
    return;
}

#if OPENTHREAD_CONFIG_PLATFORM_USEC_TIMER_ENABLE
const TimerScheduler::AlarmApi TimerMicroScheduler::sAlarmMicroApi = {&otPlatAlarmMicroStartAt, &otPlatAlarmMicroStop,
                                                                      &otPlatAlarmMicroGetNow};
void                           TimerMicro::Start(uint32_t aDelay)
{
    StartAt(GetNow(), aDelay);
}

void TimerMicro::StartAt(TimeMicro aStartTime, uint32_t aDelay)
{
    assert(aDelay <= kMaxDelay);
    FireAt(aStartTime + aDelay);
}

void TimerMicro::FireAt(TimeMicro aFireTime)
{
    mFireTime = aFireTime;
    Get<TimerMicroScheduler>().Add(*this);
}

void TimerMicro::Stop(void)
{
    Get<TimerMicroScheduler>().Remove(*this);
}

extern "C" void otPlatAlarmMicroFired(otInstance *aInstance)
{
    Instance *instance = static_cast<Instance *>(aInstance);

    VerifyOrExit(otInstanceIsInitialized(aInstance));
    instance->Get<TimerMicroScheduler>().ProcessTimers();

exit:
    return;
}
#endif // OPENTHREAD_CONFIG_PLATFORM_USEC_TIMER_ENABLE

} // namespace ot