把libevent 2.1.8源碼的最小堆提取出來，自己封裝成定時器使用（1）（★firecat推薦★）

Libevent中的timeout事件是使用最小堆來管理維護的.代碼位于<minheap-internal.h>.

源碼來源：

https://github.com/libevent/libevent/blob/release-2.1.8-stable/minheap-internal.h

本篇把libevent 2.1.8源碼的最小堆提取出來，自己封裝成C++定時器類使用。本篇不涉及Linux網絡程式設計。

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 <[email protected]>
 *
 * 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_ */