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本章讲述一下nginx中红黑树的实现。关于具体实现原理，我们有其他的章节进行了详细的说明。这里不再细述。

1. 相关数据结构的定义

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_RBTREE_H_INCLUDED_
#define _NGX_RBTREE_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>


typedef ngx_uint_t  ngx_rbtree_key_t;
typedef ngx_int_t   ngx_rbtree_key_int_t;


typedef struct ngx_rbtree_node_s  ngx_rbtree_node_t;

struct ngx_rbtree_node_s {
    ngx_rbtree_key_t       key;
    ngx_rbtree_node_t     *left;
    ngx_rbtree_node_t     *right;
    ngx_rbtree_node_t     *parent;
    u_char                 color;
    u_char                 data;
};


typedef struct ngx_rbtree_s  ngx_rbtree_t;

typedef void (*ngx_rbtree_insert_pt) (ngx_rbtree_node_t *root,
    ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel);

struct ngx_rbtree_s {
    ngx_rbtree_node_t     *root;
    ngx_rbtree_node_t     *sentinel;
    ngx_rbtree_insert_pt   insert;
};

这里与我们以前讲述的红黑树唯一的一点不同就是多了一个sentinel变量，其实这里的sentinel就是叶节点,只不过我们以前将该节点设为NIL，称为nil叶子。

2. 相关函数声明

#define ngx_rbtree_init(tree, s, i)                                           \
    ngx_rbtree_sentinel_init(s);                                              \
    (tree)->root = s;                                                         \
    (tree)->sentinel = s;                                                     \
    (tree)->insert = i


void ngx_rbtree_insert(ngx_rbtree_t *tree, ngx_rbtree_node_t *node);
void ngx_rbtree_delete(ngx_rbtree_t *tree, ngx_rbtree_node_t *node);
void ngx_rbtree_insert_value(ngx_rbtree_node_t *root, ngx_rbtree_node_t *node,
    ngx_rbtree_node_t *sentinel);
void ngx_rbtree_insert_timer_value(ngx_rbtree_node_t *root,
    ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel);


#define ngx_rbt_red(node)               ((node)->color = 1)
#define ngx_rbt_black(node)             ((node)->color = 0)
#define ngx_rbt_is_red(node)            ((node)->color)
#define ngx_rbt_is_black(node)          (!ngx_rbt_is_red(node))
#define ngx_rbt_copy_color(n1, n2)      (n1->color = n2->color)


/* a sentinel must be black */

#define ngx_rbtree_sentinel_init(node)  ngx_rbt_black(node)


static ngx_inline ngx_rbtree_node_t *
ngx_rbtree_min(ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel)
{
    while (node->left != sentinel) {
        node = node->left;
    }

    return node;
}


#endif /

上面声明了一些操作红黑树的函数。我们注意到sentinel节点都是黑色的，即sentinel 叶节点都是黑色的。



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