Libevent中的timeout事件是使用最小堆来管理维护的.代码位于<minheap-internal.h>.
源码来源：https://github.com/libevent/libevent/blob/release-2.1.8-stable/minheap-internal.h
本篇把libevent 2.1.8源码的最小堆提取出来，自己封装成C++定时器类使用。本篇不涉及Linux网络编程。
1、CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
PROJECT(min_heap_libevent_timer)
AUX_SOURCE_DIRECTORY(. SRC_LIST)
ADD_EXECUTABLE(${PROJECT_NAME} ${SRC_LIST})
2、minheap-event-firecat.h
#ifndef MINHEAPEVENTFIRECAT_H
#define MINHEAPEVENTFIRECAT_H
#include <sys/time.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
//come from https://github.com/libevent/libevent/blob/release-2.1.8-stable/mm-internal.h
#define mm_malloc(sz) malloc(sz)
#define mm_calloc(n, sz) calloc((n), (sz))
#define mm_strdup(s) strdup(s)
#define mm_realloc(p, sz) realloc((p), (sz))
#define mm_free(p) free(p)
//come from https://github.com/libevent/libevent/blob/release-2.1.8-stable/include/event2/util.h
#define evutil_timercmp(tvp, uvp, cmp) \
(((tvp)->tv_sec == (uvp)->tv_sec) ? \
((tvp)->tv_usec cmp (uvp)->tv_usec) : \
((tvp)->tv_sec cmp (uvp)->tv_sec))
#define evutil_timersub(tvp, uvp, vvp) \
do { \
(vvp)->tv_sec = (tvp)->tv_sec - (uvp)->tv_sec; \
(vvp)->tv_usec = (tvp)->tv_usec - (uvp)->tv_usec; \
if ((vvp)->tv_usec < 0) { \
(vvp)->tv_sec--; \
(vvp)->tv_usec += 1000000; \
} \
} while (0)
#define evutil_timeradd(tvp, uvp, vvp) \
do { \
(vvp)->tv_sec = (tvp)->tv_sec + (uvp)->tv_sec; \
(vvp)->tv_usec = (tvp)->tv_usec + (uvp)->tv_usec; \
if ((vvp)->tv_usec >= 1000000) { \
(vvp)->tv_sec++; \
(vvp)->tv_usec -= 1000000; \
} \
} while (0)
//come from https://github.com/libevent/libevent/blob/release-2.1.8-stable/include/event2/event_struct.h
struct event
{
/* for managing timeouts */
union {
//TAILQ_ENTRY(event) ev_next_with_common_timeout;
int min_heap_idx;
} ev_timeout_pos;
unsigned int timer_id;
struct timeval ev_interval;
struct timeval ev_timeout;
int ev_exe_num;
void (*ev_callback)(void *arg);
void *ev_arg;
int ev_res; /* result passed to event callback */
int ev_flags;
};
static inline void gettime(struct timeval *tm);
void gettime(struct timeval *tm)
{
gettimeofday(tm, NULL);
}
#endif // MINHEAPEVENTFIRECAT_H
3、minheap-internal.h
/*
* Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
*
* Copyright (c) 2006 Maxim Yegorushkin <maxim.yegorushkin@gmail.com>
*
* 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. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
#ifndef MINHEAP_INTERNAL_H_INCLUDED_
#define MINHEAP_INTERNAL_H_INCLUDED_
//come from https://github.com/libevent/libevent/blob/release-2.1.8-stable/minheap-internal.h
/*firecat del
#include "event2/event-config.h"
#include "evconfig-private.h"
#include "event2/event.h"
#include "event2/event_struct.h"
#include "event2/util.h"
#include "util-internal.h"
#include "mm-internal.h"
*/
#include "minheap-event-firecat.h" //firecat add
typedef struct min_heap
{
struct event** p;
unsigned n, a;
} min_heap_t;
static inline void min_heap_ctor_(min_heap_t* s);
static inline void min_heap_dtor_(min_heap_t* s);
static inline void min_heap_elem_init_(struct event* e);
static inline int min_heap_elt_is_top_(const struct event *e);
static inline int min_heap_empty_(min_heap_t* s);
static inline unsigned min_heap_size_(min_heap_t* s);
static inline struct event* min_heap_top_(min_heap_t* s);
static inline int min_heap_reserve_(min_heap_t* s, unsigned n);
static inline int min_heap_push_(min_heap_t* s, struct event* e);
static inline struct event* min_heap_pop_(min_heap_t* s);
static inline int min_heap_adjust_(min_heap_t *s, struct event* e);
static inline int min_heap_erase_(min_heap_t* s, struct event* e);
static inline void min_heap_shift_up_(min_heap_t* s, unsigned hole_index, struct event* e);
static inline void min_heap_shift_up_unconditional_(min_heap_t* s, unsigned hole_index, struct event* e);
static inline void min_heap_shift_down_(min_heap_t* s, unsigned hole_index, struct event* e);
#define min_heap_elem_greater(a, b) \
(evutil_timercmp(&(a)->ev_timeout, &(b)->ev_timeout, >))
void min_heap_ctor_(min_heap_t* s) { s->p = 0; s->n = 0; s->a = 0; }
void min_heap_dtor_(min_heap_t* s) { if (s->p) mm_free(s->p); }
void min_heap_elem_init_(struct event* e) { e->ev_timeout_pos.min_heap_idx = -1; }
int min_heap_empty_(min_heap_t* s) { return 0u == s->n; }
unsigned min_heap_size_(min_heap_t* s) { return s->n; }
struct event* min_heap_top_(min_heap_t* s) { return s->n ? *s->p : 0; }
int min_heap_push_(min_heap_t* s, struct event* e)
{
if (min_heap_reserve_(s, s->n + 1))
return -1;
min_heap_shift_up_(s, s->n++, e);
return 0;
}
struct event* min_heap_pop_(min_heap_t* s)
{
if (s->n)
{
struct event* e = *s->p;
min_heap_shift_down_(s, 0u, s->p[--s->n]);
e->ev_timeout_pos.min_heap_idx = -1;
return e;
}
return 0;
}
int min_heap_elt_is_top_(const struct event *e)
{
return e->ev_timeout_pos.min_heap_idx == 0;
}
int min_heap_erase_(min_heap_t* s, struct event* e)
{
if (-1 != e->ev_timeout_pos.min_heap_idx)
{
struct event *last = s->p[--s->n];
unsigned parent = (e->ev_timeout_pos.min_heap_idx - 1) / 2;
/* we replace e with the last element in the heap. We might need to
shift it upward if it is less than its parent, or downward if it is
greater than one or both its children. Since the children are known
to be less than the parent, it can't need to shift both up and
down. */
if (e->ev_timeout_pos.min_heap_idx > 0 && min_heap_elem_greater(s->p[parent], last))
min_heap_shift_up_unconditional_(s, e->ev_timeout_pos.min_heap_idx, last);
else
min_heap_shift_down_(s, e->ev_timeout_pos.min_heap_idx, last);
e->ev_timeout_pos.min_heap_idx = -1;
return 0;
}
return -1;
}
int min_heap_adjust_(min_heap_t *s, struct event *e)
{
if (-1 == e->ev_timeout_pos.min_heap_idx) {
return min_heap_push_(s, e);
} else {
unsigned parent = (e->ev_timeout_pos.min_heap_idx - 1) / 2;
/* The position of e has changed; we shift it up or down
* as needed. We can't need to do both. */
if (e->ev_timeout_pos.min_heap_idx > 0 && min_heap_elem_greater(s->p[parent], e))
min_heap_shift_up_unconditional_(s, e->ev_timeout_pos.min_heap_idx, e);
else
min_heap_shift_down_(s, e->ev_timeout_pos.min_heap_idx, e);
return 0;
}
}
int min_heap_reserve_(min_heap_t* s, unsigned n)
{
if (s->a < n)
{
struct event** p;
unsigned a = s->a ? s->a * 2 : 8;
if (a < n)
a = n;
if (!(p = (struct event**)mm_realloc(s->p, a * sizeof *p)))
return -1;
s->p = p;
s->a = a;
}
return 0;
}
void min_heap_shift_up_unconditional_(min_heap_t* s, unsigned hole_index, struct event* e)
{
unsigned parent = (hole_index - 1) / 2;
do
{
(s->p[hole_index] = s->p[parent])->ev_timeout_pos.min_heap_idx = hole_index;
hole_index = parent;
parent = (hole_index - 1) / 2;
} while (hole_index && min_heap_elem_greater(s->p[parent], e));
(s->p[hole_index] = e)->ev_timeout_pos.min_heap_idx = hole_index;
}
void min_heap_shift_up_(min_heap_t* s, unsigned hole_index, struct event* e)
{
unsigned parent = (hole_index - 1) / 2;
while (hole_index && min_heap_elem_greater(s->p[parent], e))
{
(s->p[hole_index] = s->p[parent])->ev_timeout_pos.min_heap_idx = hole_index;
hole_index = parent;
parent = (hole_index - 1) / 2;
}
(s->p[hole_index] = e)->ev_timeout_pos.min_heap_idx = hole_index;
}
void min_heap_shift_down_(min_heap_t* s, unsigned hole_index, struct event* e)
{
unsigned min_child = 2 * (hole_index + 1);
while (min_child <= s->n)
{
min_child -= min_child == s->n || min_heap_elem_greater(s->p[min_child], s->p[min_child - 1]);
if (!(min_heap_elem_greater(e, s->p[min_child])))
break;
(s->p[hole_index] = s->p[min_child])->ev_timeout_pos.min_heap_idx = hole_index;
hole_index = min_child;
min_child = 2 * (hole_index + 1);
}
(s->p[hole_index] = e)->ev_timeout_pos.min_heap_idx = hole_index;
}
#endif /* MINHEAP_INTERNAL_H_INCLUDED_ */
4、my_timer.h
#ifndef MY_TIMER_H
#define MY_TIMER_H
#define LIMIT_TIMER 1 //有限次数定时器
#define CYCLE_TIMER 2 //循环定时器
extern "C"
{
#include "minheap-internal.h"
}
class Timer
{
public:
Timer();
virtual ~Timer();
/**************************************
* input: interval: 每次执行的时间隔间, 单位是毫秒。
* fun arg : 回调函数以及参数。
* flag : 循环定时器还是有限次数定时器，如果是相对定时器
* exe_num : 只有在有限次数定时器才有效，表示执行的次数。最少为1次
* return: 生成定时器的ID
**************************************/
unsigned int timer_add(int interval, void (*fun)(void*), void *arg, int flag = CYCLE_TIMER,
int exe_num = 0);
/***************************************
* description:
* 去掉已经加入的定时器，比如产生定时器的母体已经消亡了，在消亡之间要将其删除。
* 相对定时器在任务完成后会Timer会自己释放掉。
***************************************/
bool timer_remove(unsigned int timer_id);
/***************************************
* description: Timer属于被动对象，没有自己的执行线程，属于被调用者。这样主要是为了避免产生线程同步。
* 定时器的循环处理函数，由定时器的拥有者进行循环调用。它的最小时间间隔决定了定时器的精度。
***************************************/
int timer_process();
private:
struct min_heap _min_heap;
unsigned int _timer_id;
};
#endif // MY_TIMER_H
5、my_timer.cpp
#include "my_timer.h"
Timer::Timer() :
_timer_id(0)
{
min_heap_ctor_(&_min_heap);
}
Timer::~Timer()
{
for (int i = 0; i < _min_heap.n; i++)
{
free(_min_heap.p[i]);
}
min_heap_dtor_(&_min_heap);
}
unsigned int Timer::timer_add(int interval, void(*fun)(void*), void *arg,
int flag /* = CYCLE_TIMER */, int exe_num /* = 0 */)
{
struct event * ev = (struct event*) malloc(sizeof(struct event));
min_heap_elem_init_(ev);
if (NULL == ev)
return NULL;
struct timeval now;
gettime(&now);
ev->ev_interval.tv_sec = interval / 1000;
ev->ev_interval.tv_usec = (interval % 1000) * 1000;
evutil_timeradd(&now, &(ev->ev_interval), &(ev->ev_timeout));
ev->ev_flags = flag;
ev->ev_callback = fun;
ev->ev_arg = arg;
ev->ev_exe_num = exe_num;
ev->timer_id = _timer_id++;
min_heap_push_(&_min_heap, ev);
return ev->timer_id;
}
bool Timer::timer_remove(unsigned int timer_id)
{
for (int i = 0; i < _min_heap.n; i++)
{
if (timer_id == _min_heap.p[i]->timer_id)
{
struct event * e = _min_heap.p[i];
min_heap_erase_(&_min_heap, _min_heap.p[i]);
free(e);
return true;
}
}
return false;
}
int Timer::timer_process()
{
struct event *event;
struct timeval now;
while ((event = min_heap_top_(&_min_heap)) != NULL)
{
gettime(&now);
if (evutil_timercmp(&now, &(event->ev_timeout), < ))
break;
min_heap_pop_(&_min_heap);
event->ev_callback(event->ev_arg);
if (event->ev_flags == CYCLE_TIMER
|| (event->ev_flags == LIMIT_TIMER && --event->ev_exe_num > 0))
{
evutil_timeradd(&(event->ev_timeout), &(event->ev_interval), &(event->ev_timeout));
min_heap_push_(&_min_heap, event);
}
else
{
free(event);
}
}
return 0;
}
6、main.cpp
#include <iostream>
#include "my_timer.h"
#include <unistd.h>
using namespace std;
static void fun(void *arg)
{
int *id = (int *) arg;
cout << *id << endl;
}
int main()
{
cout << "Hello World!" << endl;
Timer t;
int id1 = 100;
t.timer_add(1000, fun, &id1);//ms
int id2 = 101;
t.timer_add(5000, fun, &id2);
int id3 = 102;
t.timer_add(3000, fun, &id3);
while (true)
{
t.timer_process();
sleep(1);
}
system("pause");
return 0;
}
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