ngx_queue.h:

#include <ngx_config.h>
#include <ngx_core.h>#ifndef _NGX_QUEUE_H_INCLUDED_
#define _NGX_QUEUE_H_INCLUDED_typedef struct ngx_queue_s  ngx_queue_t;
//队列的两个节点prev和next
struct ngx_queue_s {ngx_queue_t  *prev;ngx_queue_t  *next;
};//初始化循循环环队列
#define ngx_queue_init(q)                                                     \(q)->prev = q;                                                            \(q)->next = q//判断队列是否为空
#define ngx_queue_empty(h)                                                    \(h == (h)->prev)//向队列头插入一个节点
#define ngx_queue_insert_head(h, x)                                           \(x)->next = (h)->next;                                                    \(x)->next->prev = x;                                                      \(x)->prev = h;                                                            \(h)->next = x#define ngx_queue_insert_after   ngx_queue_insert_head//向队列尾加入节点
#define ngx_queue_insert_tail(h, x)                                           \(x)->prev = (h)->prev;                                                    \(x)->prev->next = x;                                                      \(x)->next = h;                                                            \(h)->prev = x//由于是循环队列，任一节点均可以当作头节点
#define ngx_queue_head(h)                                                     \(h)->next//返回队尾节点
#define ngx_queue_last(h)                                                     \(h)->prev#define ngx_queue_sentinel(h)                                                 \(h)//返回q节点next
#define ngx_queue_next(q)                                                     \(q)->next//返回q节点prev
#define ngx_queue_prev(q)                                                     \(q)->prev#if (NGX_DEBUG)#define ngx_queue_remove(x)                                                   \(x)->next->prev = (x)->prev;                                              \(x)->prev->next = (x)->next;                                              \(x)->prev = NULL;                                                         \(x)->next = NULL#else
//删除队列一个节点
#define ngx_queue_remove(x)                                                   \(x)->next->prev = (x)->prev;                                              \(x)->prev->next = (x)->next#endif//以q为分界点分离队列，h不包含q节点，n包含q节点
#define ngx_queue_split(h, q, n)                                              \(n)->prev = (h)->prev;                                                    \(n)->prev->next = n;                                                      \(n)->next = q;                                                            \(h)->prev = (q)->prev;                                                    \(h)->prev->next = h;                                                      \(q)->prev = n;//将n链表加入队列
#define ngx_queue_add(h, n)                                                   \(h)->prev->next = (n)->next;                                              \(n)->next->prev = (h)->prev;                                              \(h)->prev = (n)->prev;                                                    \(h)->prev->next = h;//offsetof计算结构体的成员偏移量
#define ngx_queue_data(q, type, link)                                         \(type *) ((u_char *) q - offsetof(type, link))ngx_queue_t *ngx_queue_middle(ngx_queue_t *queue);
void ngx_queue_sort(ngx_queue_t *queue,ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *));#endif /* _NGX_QUEUE_H_INCLUDED_ */

nginx.c:

/***奇数的是返回中位，偶数返回队列第二部分的第一个元素*这里用到的技巧是每次middle向后移动一步，next向后移动两步，这样next指到队尾*的时候，middle就指到了中间，时间复杂度就是O(N)**/
ngx_queue_t *
ngx_queue_middle(ngx_queue_t *queue)
{ngx_queue_t  *middle, *next;//寻找队列的头部middle = ngx_queue_head(queue);//若middle为队列的队尾则直接返回if (middle == ngx_queue_last(queue)) {return middle;}next = ngx_queue_head(queue);for ( ;; ) {middle = ngx_queue_next(middle);next = ngx_queue_next(next);if (next == ngx_queue_last(queue)) {return middle;}next = ngx_queue_next(next);if (next == ngx_queue_last(queue)) {return middle;}}
}

//插入排序算法，时间复杂度O(N^2)
void
ngx_queue_sort(ngx_queue_t *queue,ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *))
{ngx_queue_t  *q, *prev, *next;q = ngx_queue_head(queue);if (q == ngx_queue_last(queue)) {return;}for (q = ngx_queue_next(q); q != ngx_queue_sentinel(queue); q = next) {prev = ngx_queue_prev(q);next = ngx_queue_next(q);ngx_queue_remove(q);do {if (cmp(prev, q) <= 0) {break;}prev = ngx_queue_prev(prev);} while (prev != ngx_queue_sentinel(queue));ngx_queue_insert_after(prev, q);}
}