Nginx的红黑树结构

        ngx_rbtree_t是使用红黑树实现的一种关联容器，Nginx的核心模块(如定时器模块、文件缓存模块等)在需要快速检索、查找的情况下都使用了ngx_rbtree_t结构。关于红黑树的代码实现点击：数据结构-红黑树。更多关于红黑树的介绍请点击：红黑树理解。

Nginx中ngx_rbtree_t相关源码

ngx_rbtree.h文件

#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;};#define ngx_rbtree_init(tree, s, i)                                           \    ngx_rbtree_sentinel_init(s);                                              \    (tree)->root = s;                                                         \    (tree)->sentinel = s;                                                     \    (tree)->insert = ivoid 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 /* _NGX_RBTREE_H_INCLUDED_ */

ngx_rbtree.c文件

#include <ngx_config.h>#include <ngx_core.h>/* * The red-black tree code is based on the algorithm described in * the "Introduction to Algorithms" by Cormen, Leiserson and Rivest. */static ngx_inline void ngx_rbtree_left_rotate(ngx_rbtree_node_t **root,    ngx_rbtree_node_t *sentinel, ngx_rbtree_node_t *node);static ngx_inline void ngx_rbtree_right_rotate(ngx_rbtree_node_t **root,    ngx_rbtree_node_t *sentinel, ngx_rbtree_node_t *node);// 插入函数，调用自定义的插入操作，然后在负责红黑树平衡操作voidngx_rbtree_insert(ngx_rbtree_t *tree, ngx_rbtree_node_t *node){    ngx_rbtree_node_t  **root, *temp, *sentinel;    /* a binary tree insert */    root = (ngx_rbtree_node_t **) &tree->root;    sentinel = tree->sentinel;    if (*root == sentinel) {        node->parent = NULL;        node->left = sentinel;        node->right = sentinel;        ngx_rbt_black(node);        *root = node;        return;    }// 调用自定义的插入函数，该插入函数只负责插入操作，不负责平衡操作    tree->insert(*root, node, sentinel);    /* re-balance tree */// node为新插入的节点，如果node的父节点为红色，则需要旋转操作    while (node != *root && ngx_rbt_is_red(node->parent)) {        if (node->parent == node->parent->parent->left) {            temp = node->parent->parent->right;            if (ngx_rbt_is_red(temp)) {// case 1: node的uncle节点是红色的                ngx_rbt_black(node->parent);                ngx_rbt_black(temp);                ngx_rbt_red(node->parent->parent);                node = node->parent->parent;            } else {                if (node == node->parent->right) {// case 2: node为右孩子，且uncle节点是黑色的，进行左旋操作                    node = node->parent;                    ngx_rbtree_left_rotate(root, sentinel, node);                }// case 3: node为左孩子，且uncle节点是黑色的，进行右旋操作                ngx_rbt_black(node->parent);                ngx_rbt_red(node->parent->parent);                ngx_rbtree_right_rotate(root, sentinel, node->parent->parent);            }        } else {            temp = node->parent->parent->left;            if (ngx_rbt_is_red(temp)) {                ngx_rbt_black(node->parent);                ngx_rbt_black(temp);                ngx_rbt_red(node->parent->parent);                node = node->parent->parent;            } else {                if (node == node->parent->left) {                    node = node->parent;                    ngx_rbtree_right_rotate(root, sentinel, node);                }                ngx_rbt_black(node->parent);                ngx_rbt_red(node->parent->parent);                ngx_rbtree_left_rotate(root, sentinel, node->parent->parent);            }        }    }    ngx_rbt_black(*root);}voidngx_rbtree_insert_value(ngx_rbtree_node_t *temp, ngx_rbtree_node_t *node,    ngx_rbtree_node_t *sentinel){    ngx_rbtree_node_t  **p;    for ( ;; ) {        p = (node->key < temp->key) ? &temp->left : &temp->right;        if (*p == sentinel) {            break;        }        temp = *p;    }    *p = node;    node->parent = temp;    node->left = sentinel;    node->right = sentinel;    ngx_rbt_red(node);}voidngx_rbtree_insert_timer_value(ngx_rbtree_node_t *temp, ngx_rbtree_node_t *node,    ngx_rbtree_node_t *sentinel){    ngx_rbtree_node_t  **p;    for ( ;; ) {        /*         * Timer values         * 1) are spread in small range, usually several minutes,         * 2) and overflow each 49 days, if milliseconds are stored in 32 bits.         * The comparison takes into account that overflow.         */        /*  node->key < temp->key */        p = ((ngx_rbtree_key_int_t) (node->key - temp->key) < 0)            ? &temp->left : &temp->right;        if (*p == sentinel) {            break;        }        temp = *p;    }    *p = node;    node->parent = temp;    node->left = sentinel;    node->right = sentinel;    ngx_rbt_red(node);}voidngx_rbtree_delete(ngx_rbtree_t *tree, ngx_rbtree_node_t *node){    ngx_uint_t           red;    ngx_rbtree_node_t  **root, *sentinel, *subst, *temp, *w;    /* a binary tree delete */    root = (ngx_rbtree_node_t **) &tree->root;    sentinel = tree->sentinel;    if (node->left == sentinel) {        temp = node->right;        subst = node;    } else if (node->right == sentinel) {        temp = node->left;        subst = node;    } else {        subst = ngx_rbtree_min(node->right, sentinel);        if (subst->left != sentinel) {            temp = subst->left;        } else {            temp = subst->right;        }    }    if (subst == *root) {        *root = temp;        ngx_rbt_black(temp);        /* DEBUG stuff */        node->left = NULL;        node->right = NULL;        node->parent = NULL;        node->key = 0;        return;    }    red = ngx_rbt_is_red(subst);    if (subst == subst->parent->left) {        subst->parent->left = temp;    } else {        subst->parent->right = temp;    }    if (subst == node) {        temp->parent = subst->parent;    } else {        if (subst->parent == node) {            temp->parent = subst;        } else {            temp->parent = subst->parent;        }        subst->left = node->left;        subst->right = node->right;        subst->parent = node->parent;        ngx_rbt_copy_color(subst, node);        if (node == *root) {            *root = subst;        } else {            if (node == node->parent->left) {                node->parent->left = subst;            } else {                node->parent->right = subst;            }        }        if (subst->left != sentinel) {            subst->left->parent = subst;        }        if (subst->right != sentinel) {            subst->right->parent = subst;        }    }    /* DEBUG stuff */    node->left = NULL;    node->right = NULL;    node->parent = NULL;    node->key = 0;    if (red) {        return;    }    /* a delete fixup */    while (temp != *root && ngx_rbt_is_black(temp)) {        if (temp == temp->parent->left) {            w = temp->parent->right;            if (ngx_rbt_is_red(w)) {                ngx_rbt_black(w);                ngx_rbt_red(temp->parent);                ngx_rbtree_left_rotate(root, sentinel, temp->parent);                w = temp->parent->right;            }            if (ngx_rbt_is_black(w->left) && ngx_rbt_is_black(w->right)) {                ngx_rbt_red(w);                temp = temp->parent;            } else {                if (ngx_rbt_is_black(w->right)) {                    ngx_rbt_black(w->left);                    ngx_rbt_red(w);                    ngx_rbtree_right_rotate(root, sentinel, w);                    w = temp->parent->right;                }                ngx_rbt_copy_color(w, temp->parent);                ngx_rbt_black(temp->parent);                ngx_rbt_black(w->right);                ngx_rbtree_left_rotate(root, sentinel, temp->parent);                temp = *root;            }        } else {            w = temp->parent->left;            if (ngx_rbt_is_red(w)) {                ngx_rbt_black(w);                ngx_rbt_red(temp->parent);                ngx_rbtree_right_rotate(root, sentinel, temp->parent);                w = temp->parent->left;            }            if (ngx_rbt_is_black(w->left) && ngx_rbt_is_black(w->right)) {                ngx_rbt_red(w);                temp = temp->parent;            } else {                if (ngx_rbt_is_black(w->left)) {                    ngx_rbt_black(w->right);                    ngx_rbt_red(w);                    ngx_rbtree_left_rotate(root, sentinel, w);                    w = temp->parent->left;                }                ngx_rbt_copy_color(w, temp->parent);                ngx_rbt_black(temp->parent);                ngx_rbt_black(w->left);                ngx_rbtree_right_rotate(root, sentinel, temp->parent);                temp = *root;            }        }    }    ngx_rbt_black(temp);}static ngx_inline voidngx_rbtree_left_rotate(ngx_rbtree_node_t **root, ngx_rbtree_node_t *sentinel,    ngx_rbtree_node_t *node){    ngx_rbtree_node_t  *temp;    temp = node->right;    node->right = temp->left;    if (temp->left != sentinel) {        temp->left->parent = node;    }    temp->parent = node->parent;    if (node == *root) {        *root = temp;    } else if (node == node->parent->left) {        node->parent->left = temp;    } else {        node->parent->right = temp;    }    temp->left = node;    node->parent = temp;}static ngx_inline voidngx_rbtree_right_rotate(ngx_rbtree_node_t **root, ngx_rbtree_node_t *sentinel,    ngx_rbtree_node_t *node){    ngx_rbtree_node_t  *temp;    temp = node->left;    node->left = temp->right;    if (temp->right != sentinel) {        temp->right->parent = node;    }    temp->parent = node->parent;    if (node == *root) {        *root = temp;    } else if (node == node->parent->right) {        node->parent->right = temp;    } else {        node->parent->left = temp;    }    temp->right = node;    node->parent = temp;}

参考资料

       https://github.com/luoxn28/algorithm_data_structure