Timer-Library/src/WheelTimer.c

#include <stdlib.h>
#include <stdio.h>
#include <memory.h>
#include <unistd.h>
#include <time.h>
#include <assert.h>
#include <timerlib.h>
#include <WheelTimer.h>

int
insert_wt_elem_in_slot(void* data1, void* data2) {

    wheel_timer_elem_t* wt_elem1 = (wheel_timer_elem_t*)data1;
    wheel_timer_elem_t* wt_elem2 = (wheel_timer_elem_t*)data2;

    if (wt_elem1->execute_cycle_no < wt_elem2->execute_cycle_no)
        return -1;

    if (wt_elem1->execute_cycle_no > wt_elem2->execute_cycle_no)
        return 1;

    return 0;
}

static void
process_wt_reschedule_slotlist(wheel_timer_t* wt) {

    glthread_t* curr;
    wheel_timer_elem_t* wt_elem;

    WT_LOCK_SLOT_LIST(WT_GET_RESCHD_SLOTLIST(wt));
    if (WT_IS_SLOTLIST_EMPTY(WT_GET_RESCHD_SLOTLIST(wt))) {
        WT_UNLOCK_SLOT_LIST(WT_GET_RESCHD_SLOTLIST(wt));
        return;
    }

    ITERATE_GLTHREAD_BEGIN(WT_GET_RESCHD_SLOTLIST_HEAD(wt), curr) {

        wt_elem = glthread_reschedule_glue_to_wt_elem(curr);
        remove_glthread(&wt_elem->glue);
        wt_elem->slotlist_head = NULL;

        switch (wt_elem->opcode) {
        case WTELEM_CREATE:
        case WTELEM_RESCHED:
        {
            assert(wt_elem->app_callback);
            wt_elem->time_interval = wt_elem->new_time_interval;
            int absolute_slot_no = GET_WT_CURRENT_ABS_SLOT_NO(wt);
            int next_abs_slot_no = absolute_slot_no +
                (wt_elem->time_interval / wt->clock_tic_interval);
            int next_cycle_no = next_abs_slot_no / wt->wheel_size;
            int next_slot_no = next_abs_slot_no % wt->wheel_size;
            wt_elem->execute_cycle_no = next_cycle_no;
            wt_elem->slot_no = next_slot_no;
            glthread_priority_insert(WT_SLOTLIST_HEAD(wt, wt_elem->slot_no),
                &wt_elem->glue,
                insert_wt_elem_in_slot,
                (unsigned long)&((wheel_timer_elem_t*)0)->glue);
            wt_elem->slotlist_head = WT_SLOTLIST(wt, wt_elem->slot_no);
            remove_glthread(&wt_elem->reschedule_glue);
            wt_elem->N_scheduled++;
            if (wt_elem->opcode == WTELEM_CREATE) {
                wt->no_of_wt_elem++;
            }
            wt_elem->opcode = WTELEM_SCHEDULED;
        }
        break;
        case WTELEM_DELETE:
            remove_glthread(&wt_elem->reschedule_glue);
            free_wheel_timer_element(wt_elem);
            wt->no_of_wt_elem--;
            break;
        default:
            assert(0);
        }
    }ITERATE_GLTHREAD_END(WT_GET_RESCHD_SLOTLIST_HEAD(wt), curr)
        WT_UNLOCK_SLOT_LIST(WT_GET_RESCHD_SLOTLIST(wt));
}

static void
wheel_fn(Timer_t* timer, void* arg) {

    wheel_timer_t* wt = (wheel_timer_t*)arg;
    wheel_timer_elem_t* wt_elem = NULL;
    int absolute_slot_no = 0, i = 0;
    slotlist_t* slot_list = NULL;
    glthread_t* curr;

    wt->current_clock_tic++;
    if (wt->current_clock_tic == wt->wheel_size) {
        wt->current_clock_tic = 0;
        wt->current_cycle_no++;
    }

    slot_list = WT_SLOTLIST(wt, wt->current_clock_tic);
    absolute_slot_no = GET_WT_CURRENT_ABS_SLOT_NO(wt);

    ITERATE_GLTHREAD_BEGIN(&slot_list->slots, curr) {

        wt_elem = glthread_to_wt_elem(curr);

        /*Check if R == r*/
        if (wt->current_cycle_no == wt_elem->execute_cycle_no) {
            /*Invoke the application event through fn pointer as below*/
            wt_elem->app_callback(wt_elem->arg, wt_elem->arg_size);

            /* After invocation, check if the event needs to be rescheduled again
             * in future*/
            if (wt_elem->is_recurrence) {

                /*relocate Or reschedule to the next slot*/
                int next_abs_slot_no = absolute_slot_no +
                    (wt_elem->time_interval / wt->clock_tic_interval);
                int next_cycle_no = next_abs_slot_no / wt->wheel_size;
                int next_slot_no = next_abs_slot_no % wt->wheel_size;
                wt_elem->execute_cycle_no = next_cycle_no;
                remove_glthread(&wt_elem->glue);
                glthread_priority_insert(WT_SLOTLIST_HEAD(wt, next_slot_no), &wt_elem->glue,
                    insert_wt_elem_in_slot,
                    (unsigned long)&((wheel_timer_elem_t*)0)->glue);
                wt_elem->slotlist_head = WT_SLOTLIST(wt, next_slot_no);
                wt_elem->slot_no = next_slot_no;
                wt_elem->N_scheduled++;
            }
        }
        else
            break;
    } ITERATE_GLTHREAD_END(slot_list, curr)
        process_wt_reschedule_slotlist(wt);
}

wheel_timer_t*
init_wheel_timer(int wheel_size, int clock_tic_interval) {

    /*@@@@@@@@@@@@@@@@@@@*/
    wheel_timer_t* wt = calloc(1, sizeof(wheel_timer_t) +
        (wheel_size * sizeof(slotlist_t)));
    /*@@@@@@@@@@@@@@@@@@@*/

    wt->clock_tic_interval = clock_tic_interval;
    wt->wheel_size = wheel_size;

    wt->wheel_thread = setup_timer(wheel_fn,
        wt->clock_tic_interval * 1000,
        wt->clock_tic_interval * 1000,
        0,
        (void*)wt,
        false);

    int i = 0;

    for (; i < wheel_size; i++) {
        init_glthread(WT_SLOTLIST_HEAD(wt, i));
        pthread_mutex_init(WT_SLOTLIST_MUTEX(wt, i), NULL);
    }

    wt->no_of_wt_elem = 0;
    return wt;
}


static void
_wt_elem_reschedule(wheel_timer_t* wt,
    wheel_timer_elem_t* wt_elem,
    int new_time_interval,
    wt_opcode_t opcode) {

    if (wt_elem->opcode == WTELEM_DELETE &&
        (opcode == WTELEM_CREATE ||
            opcode == WTELEM_RESCHED)) {
        /* This is a Valid Scenario. A Race condition may arise When WT itself
         * invoked a timer expiry callback for a wt_elem, and at the same time
         * hello packet also arrived to refresh the same wt_elem.*/
         //assert(0);
    }
    switch (opcode) {
    case WTELEM_CREATE:
    case WTELEM_RESCHED:
    case WTELEM_DELETE:

        wt_elem->new_time_interval = new_time_interval;
        pause_timer(wt->wheel_thread);
        WT_LOCK_SLOT_LIST(WT_GET_RESCHD_SLOTLIST(wt));
        wt_elem->opcode = opcode;
        remove_glthread(&wt_elem->reschedule_glue);
        glthread_add_next(WT_GET_RESCHD_SLOTLIST_HEAD(wt),
            &wt_elem->reschedule_glue);
        WT_UNLOCK_SLOT_LIST(WT_GET_RESCHD_SLOTLIST(wt));
        resume_timer(wt->wheel_thread);
        break;
    default:
        assert(0);
    }
}


wheel_timer_elem_t*
register_app_event(wheel_timer_t* wt,
    app_call_back call_back,
    void* arg,
    int arg_size,
    int time_interval,
    char is_recursive) {

    if (!wt || !call_back) return NULL;
    wheel_timer_elem_t* wt_elem = calloc(1, sizeof(wheel_timer_elem_t));
    wt_elem->app_callback = call_back;
    if (arg && arg_size) {
        wt_elem->arg = calloc(1, arg_size);
        memcpy(wt_elem->arg, arg, arg_size);
        wt_elem->arg_size = arg_size;
    }
    wt_elem->is_recurrence = is_recursive;
    init_glthread(&wt_elem->glue);
    init_glthread(&wt_elem->reschedule_glue);
    wt_elem->N_scheduled = 0;
    _wt_elem_reschedule(wt, wt_elem, time_interval, WTELEM_CREATE);
    return wt_elem;
}

void
de_register_app_event(wheel_timer_t* wt, wheel_timer_elem_t* wt_elem) {

    _wt_elem_reschedule(wt, wt_elem, 0, WTELEM_DELETE);
}

void
wt_elem_reschedule(wheel_timer_t* wt,
    wheel_timer_elem_t* wt_elem,
    int new_time_interval) {

    _wt_elem_reschedule(wt, wt_elem, new_time_interval, WTELEM_RESCHED);
}

int
wt_get_remaining_time(wheel_timer_t* wt,
    wheel_timer_elem_t* wt_elem) {

    if (wt_elem->opcode == WTELEM_CREATE ||
        wt_elem->opcode == WTELEM_RESCHED) {
        /* Means : the wt_elem has not been assigned a slot in WT,
         * just return the time interval for which it has been scheduled
         * in this case*/
        return wt_elem->new_time_interval;
    }
    int wt_elem_absolute_slot = (wt_elem->execute_cycle_no * wt->wheel_size) +
        wt_elem->slot_no;
    int diff = wt_elem_absolute_slot - GET_WT_CURRENT_ABS_SLOT_NO(wt);
    return (diff * wt->clock_tic_interval);
}

void
free_wheel_timer_element(wheel_timer_elem_t* wt_elem) {

    wt_elem->slotlist_head = NULL;
    free(wt_elem->arg);
    free(wt_elem);
}


void
print_wheel_timer(wheel_timer_t* wt) {

    int i = 0, j = 0;
    glthread_t* curr;
    glthread_t* slot_list_head = NULL;
    wheel_timer_elem_t* wt_elem = NULL;

    printf("Printing Wheel Timer DS\n");
    printf("wt->current_clock_tic  = %d\n", wt->current_clock_tic);
    printf("wt->clock_tic_interval = %d\n", wt->clock_tic_interval);
    printf("wt abs slot no         = %d\n", GET_WT_CURRENT_ABS_SLOT_NO(wt));
    printf("wt->wheel_size         = %d\n", wt->wheel_size);
    printf("wt->current_cycle_no   = %d\n", wt->current_cycle_no);
    printf("wt->wheel_thread       = %p\n", &wt->wheel_thread);
    printf("WT uptime              = %s\n", hrs_min_sec_format(WT_UPTIME(wt)));
    printf("wt->no_of_wt_elem      = %u\n", wt->no_of_wt_elem);
    printf("printing slots : \n");

    for (; i < wt->wheel_size; i++) {
        slot_list_head = WT_SLOTLIST_HEAD(wt, i);
        ITERATE_GLTHREAD_BEGIN(slot_list_head, curr) {
            wt_elem = glthread_to_wt_elem(curr);
            printf("                wt_elem->opcode             = %d\n", wt_elem->opcode);
            printf("                wt_elem                     = %p\n", wt_elem);
            printf("                wt_elem->time_interval		= %d\n", wt_elem->time_interval);
            printf("                wt_elem->execute_cycle_no	= %d\n", wt_elem->execute_cycle_no);
            printf("                wt_elem->slot_no            = %d\n", wt_elem->slot_no);
            printf("                wt_elem abs slot no         = %d\n",
                (wt_elem->execute_cycle_no * wt->wheel_size) + wt_elem->slot_no);
            printf("                wt_elem->app_callback		= %p\n", wt_elem->app_callback);
            printf("                wt_elem->arg    			= %p\n", wt_elem->arg);
            printf("                wt_elem->is_recurrence		= %d\n", wt_elem->is_recurrence);
            printf("                wt_elem->N_scheduled        = %u\n", wt_elem->N_scheduled);
            printf("                Remaining Time to Fire      = %d\n",
                wt_get_remaining_time(wt, wt_elem));
            printf("\n");
        } ITERATE_GLTHREAD_END(slot_list_head, curr)
    }
}

void
start_wheel_timer(wheel_timer_t* wt) {

    start_timer(wt->wheel_thread);
}

void
reset_wheel_timer(wheel_timer_t* wt) {
    wt->current_clock_tic = 0;
    wt->current_cycle_no = 0;
}


char*
hrs_min_sec_format(unsigned int seconds) {

    static char time_f[16];
    unsigned int hrs = 0,
        min = 0, sec = 0;

    if (seconds > 3600) {
        min = seconds / 60;
        sec = seconds % 60;
        hrs = min / 60;
        min = min % 60;
    }
    else {
        min = seconds / 60;
        sec = seconds % 60;
    }
    memset(time_f, 0, sizeof(time_f));
    sprintf(time_f, "%u::%u::%u", hrs, min, sec);
    return time_f;
}

void
cancel_wheel_timer(wheel_timer_t* wt) {

    if (wt->wheel_thread) {
        cancel_timer(wt->wheel_thread);
    }
}