// twheel.h — Tickless hierarchical timing wheel (adapted from timeout.h)
// Original: Copyright (c) 2013-2014 William Ahern, MIT license.

#ifndef TWHEEL_H
#define TWHEEL_H

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <sys/queue.h>

#define TWHEEL_VERSION 0x20160226

typedef uint64_t twheel_t;
#define TWHEEL_C(n)  UINT64_C(n)
#define TWHEEL_mHZ   TWHEEL_C(1000)
#define TWHEEL_MAX   ((TWHEEL_C(1) << 24) - 1)

enum twheel_flags {
    TWHEEL_INT = 0x01,
    TWHEEL_ABS = 0x02,
};

#define TWHEEL_INITIALIZER(flags) { (flags) }

struct twheel {
    int flags;
    twheel_t expires;
    struct twheel_list *pending;
    TAILQ_ENTRY(twheel) tqe;
    twheel_t interval;
};

TAILQ_HEAD(twheel_list, twheel);

struct twheels {
    struct twheel_list wheel[4][64], expired;
    uint64_t pending[4];
    twheel_t curtime;
    twheel_t hertz;
};

struct twheel *twheel_init(struct twheel *, int flags);
bool twheel_pending(struct twheel *);

struct twheels *twheels_open(twheel_t hz);
void twheels_close(struct twheels *);
twheel_t twheels_hz(struct twheels *);
void twheels_update(struct twheels *, twheel_t curtime);
twheel_t twheels_timeout(struct twheels *);
void twheels_add(struct twheels *, struct twheel *, twheel_t timeout);
void twheels_del(struct twheels *, struct twheel *);
struct twheel *twheels_get(struct twheels *);
bool twheels_pending(struct twheels *);
bool twheels_expired(struct twheels *);

#endif