nginx的資料結構2－自己動手重寫紅黑樹
node
parent
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費話不多說，上重寫代碼，這次姑且用英語寫的註釋當複習英語了。
rbtree.h：
/*
* Copyright (C) Bipedal Bit
* Verson 1.0.0.1
*/
#ifndef _RBTREE_H_INCLUDED_
#define _RBTREE_H_INCLUDED_
/* the node structure of the red-black tree */
typedef struct rbtree_node_s rbtree_node_t;
/* Using type int means its range is -0x7fffffff-1~0x7fffffff. */
typedef int rbtree_key_t;
/* Abstract type is complicated to achieve with C so I use char* instead. */
typedef char* rbtree_data_t;
struct rbtree_node_s
{
/* key of the node */
rbtree_key_t key;
/* pointer of the parent of the node */
rbtree_node_t* parent;
/* pointer of the left kid of the node */
rbtree_node_t* left;
/* pointer of the right kid of the node */
rbtree_node_t* right;
/* color of the node */
unsigned char color;
/* pointer of the value of the node corresponding to the key */
rbtree_data_t value;
};
/* the tree object stucture of the red-black tree */
typedef struct rbtree_s rbtree_t;
/* foundational insert function pointer*/
typedef void (*rbtree_insert_p) (rbtree_t* root, rbtree_node_t* node);
struct rbtree_s
{
/* the pointer of the root node of the tree */
rbtree_node_t* root;
/* black leaf nodes as sentinel */
rbtree_node_t* sentinel;
/* the polymorphic insert function pointer */
rbtree_insert_p insert;
};
/* macros */
#define rbtree_init(tree, s, i) \
rbtree_sentinel_init(s); \
(tree)->root = s; \
(tree)->sentinel = s; \
(tree)->insert = i
#define rbtree_red(node) ((node)->color = 1)
#define rbtree_black(node) ((node)->color = 0)
#define rbtree_is_red(node) ((node)->color)
#define rbtree_is_black(node) (!rbtree_is_red(node))
/* copy n2's color to n1 */
#define rbtree_copy_color(n1, n2) (n1->color = n2->color)
/* sentinel must be black cuz it's leaf node */
#define rbtree_sentinel_init(node) rbtree_black(node)
/* statements of public methods */
void rbtree_insert_value(rbtree_t* tree, rbtree_node_t* node);
void rbtree_insert(rbtree_t* tree, rbtree_node_t* node);
void rbtree_delete(rbtree_t* tree, rbtree_node_t* node);
rbtree_node_t* rbtree_find(rbtree_t* tree, rbtree_key_t key);
#endif /* _RBTREE_H_INCLUDED_ */登入後複製
看過nginx源碼的有心人會發現，我的頭檔相對於ngx_rbree.h改動不大，非常像。
關鍵的rbtree.c：
/*
* Copyright (C) Bipedal Bit
* Verson 1.0.0.1
*/
#include <stddef.h>
#include "rbtree.h"
/* inline methods */
/* get the node with the minimum key in a subtree of the red-black tree */
static inline rbtree_node_t*
rbtree_subtree_min(rbtree_node_t* node, rbtree_node_t* sentinel)
{
while(node->left != sentinel)
{
node = node->left;
}
return node;
}
/* replace the node "node" in the tree with node "tmp" */
static inline void rbtree_replace(rbtree_t* tree,
rbtree_node_t* node, rbtree_node_t* tmp)
{
/* upward: p[node] <- p[tmp] */
    tmp->parent = node->parent;
if (node == tree->root)
{
tree->root = tmp;
}
else if (node == node->parent->left)
{
/* downward: left[p[node]] <- tmp */
        node->parent->left = tmp;
}
else
{
/* downward: right[p[node]] <- tmp */
        node->parent->right = tmp;
}
node->parent = tmp;
}
/* change the topologic structure of the tree keeping the order of the nodes */
static inline void rbtree_left_rotate(rbtree_t* tree, rbtree_node_t* node)
{
/* node as the var x in CLRS while tmp as the var y */
rbtree_node_t* tmp = node->right;
/* replace y with left[y] */
/* downward: right[x] <- left[y] */
    node->right = tmp->left;
/* if left[[y] is not NIL it has a parent */
if (tmp->left != tree->sentinel)
{
/* upward: p[left[y]] <- x */
        tmp->left->parent = node;
}
/* replace x with y */
rbtree_replace(tree, node, tmp);
tmp->left = node;
}
static inline void rbtree_right_rotate(rbtree_t* tree, rbtree_node_t* node)
{
rbtree_node_t* tmp = node->left;
/* replace y with right[y] */
node->left = tmp->right;
if (tmp->right != tree->sentinel)
{
tmp->right->parent = node;
}
/* replace x with y */
rbtree_replace(tree, node, tmp);
tmp->right = node;
}
/* static methods */
/* fix the red-black tree after the new node inserted */
static void rbtree_insert_fixup(rbtree_t* tree, rbtree_node_t* node)
{
while(rbtree_is_red(node->parent))
{
if (node->parent == node->parent->parent->left)
{
/* case 1: node's uncle is red */
if (rbtree_is_red(node->parent->parent->right))
{
rbtree_black(node->parent);
rbtree_black(node->parent->parent->right);
rbtree_red(node->parent->parent);
node = node->parent->parent;
/* Then we can consider the whole subtree */
/* which is represented by the new "node" as the "node" before */
/* and keep looping till "node" become the root. */
}
/* case 2: node's uncle is black */
else
{
/* ensure node is the left kid of its parent */
if (node == node->parent->right)
{
node = node->parent;
rbtree_left_rotate(tree, node);
}
/* case 2 -> case 1 */
rbtree_black(node->parent);
rbtree_red(node->parent->parent);
rbtree_right_rotate(tree, node->parent->parent);
}
}
/* same as the "if" clause before with "left" and "right" exchanged */
else
{
if (rbtree_is_red(node->parent->parent->left))
{
rbtree_black(node->parent);
rbtree_black(node->parent->parent->left);
rbtree_red(node->parent->parent);
node = node->parent->parent;
}
else
{
if (node == node->parent->left)
{
node = node->parent;
rbtree_right_rotate(tree, node);
}
rbtree_black(node->parent);
rbtree_red(node->parent->parent);
rbtree_left_rotate(tree, node->parent->parent);
}
}
}
/* ensure the root node being black */
rbtree_black(tree->root);
}
static void rbtree_delete_fixup(rbtree_t* tree, rbtree_node_t* node)
{
rbtree_node_t* brother = NULL;
while(node != tree->root && rbtree_is_black(node))
{
if (node == node->parent->left)
{
brother = node->parent->right;
if (rbtree_is_red(brother))
{
rbtree_black(brother);
rbtree_red(node->parent);
rbtree_left_rotate(tree, node->parent);
/* update brother after topologic change of the tree */
brother = node->parent->right;
}
if (rbtree_is_black(brother->left) && rbtree_is_black(brother->right))
{
rbtree_red(brother);
/* go upward and keep on fixing color */
node = node->parent;
}
else
{
if (rbtree_is_black(brother->right))
{
rbtree_black(brother->left);
rbtree_red(brother);
rbtree_right_rotate(tree, brother);
/* update brother after topologic change of the tree */
brother = node->parent->right;
}
rbtree_copy_color(brother, node->parent);
rbtree_black(node->parent);
rbtree_black(brother->right);
rbtree_left_rotate(tree, node->parent);
/* end the loop and ensure root is black */
node = tree->root;
}
}
/* same as the "if" clause before with "left" and "right" exchanged */
else
{
brother = node->parent->left;
if (rbtree_is_red(brother))
{
rbtree_black(brother);
rbtree_red(node->parent);
rbtree_left_rotate(tree, node->parent);
brother = node->parent->left;
}
if (rbtree_is_black(brother->left) && rbtree_is_black(brother->right))
{
rbtree_red(brother);
node = node->parent;
}
else
{
if (rbtree_is_black(brother->left))
{
rbtree_black(brother->right);
rbtree_red(brother);
rbtree_right_rotate(tree, brother);
brother = node->parent->left;
}
rbtree_copy_color(brother, node->parent);
rbtree_black(node->parent);
rbtree_black(brother->left);
rbtree_left_rotate(tree, node->parent);
node = tree->root;
}
}
}
rbtree_black(node);
}
/* public methods */
void rbtree_insert_value(rbtree_t* tree, rbtree_node_t* node)
{
/* Using ** to know wether the new node will be a left kid */
/* or a right kid of its parent node. */
rbtree_node_t** tmp = &tree->root;
rbtree_node_t* parent;
while(*tmp != tree->sentinel)
{
parent = *tmp;
tmp = (node->key < parent->key) ? &parent->left : &parent->right;
}
/* The pointer knows wether the node should be on the left side */
/* or on the right one. */
*tmp = node;
node->parent = parent;
node->left = tree->sentinel;
node->right = tree->sentinel;
rbtree_red(node);
}
void rbtree_insert(rbtree_t* tree, rbtree_node_t* node)
{
rbtree_node_t* sentinel = tree->sentinel;
/* if the tree is empty */
if (tree->root == sentinel)
{
tree->root = node;
node->parent = sentinel;
node->left = sentinel;
node->right = sentinel;
rbtree_black(node);
return;
}
/* generally */
tree->insert(tree, node);
rbtree_insert_fixup(tree, node);
}
void rbtree_delete(rbtree_t* tree, rbtree_node_t* node)
{
rbtree_node_t* sentinel = tree->sentinel;
/* wether "node" is on the left side or the right one */
rbtree_node_t** ptr_to_node = NULL;
/* "cover" is the node which is going to cover "node" */
rbtree_node_t* cover = NULL;
/* wether we lossing a red node on the edge of the tree */
int loss_red = rbtree_is_red(node);
int is_root = (node == tree->root);
/* get "cover" & "loss_red" */
/* sentinel in "node"'s kids */
if (node->left == sentinel)
{
cover = node->right;
}
else if (node->right == sentinel)
{
cover = node->left;
}
/* "node"'s kids are both non-sentinel */
else
{
/* update "node" & "loss_red" & "is_root" & "cover" */
cover = rbtree_subtree_min(node->right, sentinel);
node->key = cover->key;
node->value = cover->value;
node = cover;
loss_red = rbtree_is_red(node);
is_root = 0;
/* move "cover"'s kids */
/* "cover" can only be a left kid */
/* and can only have a right non-sentinel kid */
/* because of function "rbtree_subtree_min" */
cover = node->right;
}
if (is_root)
{
/* update root */
tree->root = cover;
}
else
{
/* downward link */
if (node == node->parent->left)
{
node->parent->left = cover;
}
else
{
node->parent->right = cover;
}
}
/* upward link */
cover->parent = node->parent;
/* "cover" may be a sentinel */
if (cover != sentinel)
{
/* set "cover" */
cover->left = node->left;
cover->right = node->right;
rbtree_copy_color(cover, node);
}
/* clear "node" since it's useless */
node->key = -1;
node->parent = NULL;
node->left = NULL;
node->right = NULL;
node->value = NULL;
if (loss_red)
{
return;
}
/* When lossing a black node on edge */
/* the fifth rule of red-black tree will be broke. */
/* So the tree need to be fixed. */
rbtree_delete_fixup(tree, cover);
}
/* find the node in the tree corresponding to the given key value */
rbtree_node_t* rbtree_find(rbtree_t* tree, rbtree_key_t key)
{
rbtree_node_t* tmp = tree->root;
int step_cnt = 0;
/* search the binary tree */
while(tmp != tree->sentinel)
{
/* next line is just fot test */
// step_cnt++;
if(key == tmp->key)
{
/* next line is just for test */
// printf("step count: %d, color: %s, ", step_cnt, rbtree_is_red(tmp) ? "red" : "black");
return tmp;
}
tmp = (key < tmp->key) ? tmp->left : tmp->right;
}
return NULL;
}
登入後複製
雖然明白nginx源碼中100+行的長函數體也是一種避免太多函數呼叫增加時間空間開銷的優化，我還是把所有函數都分類成100行以下。增加可讀性是一方面，也可能有點強迫症。之後會擴展幾個統計方法，像max、min和mid，還會擴展一個遍歷方法。
以下是呼叫測試，test.c：
#include <stdio.h>
#include "rbtree.h"
int main(int argc, char const *argv[])
{
rbtree_t t = {};
rbtree_node_t s = {};
rbtree_init(&t, &s, rbtree_insert_value);
const int cnt = 10;
const int max_len = 15;
#define TEST_VALUES {"apple", "banana", "cherry", "grape", "lemon", "mango", "pear", "pineapple", "strawberry", "watermelon"}
/* for gcc */
char* v[] = TEST_VALUES;
/* for g++ */
// char v[][max_len] = TEST_VALUES;
rbtree_node_t n[cnt];
int i;
for (i = 0; i < cnt; i++)
    {
        n[i].key = i+1;
        n[i].value = v[i];
        rbtree_insert(&t, &n[i]);
    }
    rbtree_node_t* p[cnt];
    for (i = 1; i <= cnt; i++)
    {
        printf("key: %d\n", i);
        p[i] = rbtree_find(&t, i);
        printf("value: %s\n", (p[i] != NULL) ? p[i]->value : "?");
}
rbtree_delete(&t, &n[5]);
printf("\nafter delete 6->mango:\n\n");
for (i = 1; i <= cnt; i++)
    {
        printf("key: %d\n", i);
        p[i] = rbtree_find(&t, i);
        printf("value: %s\n", (p[i] != NULL) ? p[i]->value : "?");
}
return 0;
}
登入後複製
解開rbtree_find方法裡的測試行註釋，順利執行：
key: 1 step count: 3, color: black, value: apple key: 2 step count: 2, color: black, value: banana key: 3 step count: 3, color: black, value: cherry key: 4 step count: 1, color: black, value: grape key: 5 step count: 3, color: black, value: lemon key: 6 step count: 2, color: black, value: mango key: 7 step count: 4, color: black, value: pear key: 8 step count: 3, color: red, value: pineapple key: 9 step count: 4, color: black, value: strawberry key: 10 step count: 5, color: red, value: watermelon after delete 6->mango: key: 1 step count: 3, color: black, value: apple key: 2 step count: 2, color: black, value: banana key: 3 step count: 3, color: black, value: cherry key: 4 step count: 1, color: black, value: grape key: 5 step count: 3, color: black, value: lemon key: 6 value: ? key: 7 step count: 2, color: black, value: pear key: 8 step count: 4, color: black, value: pineapple key: 9 step count: 3, color: red, value: strawberry key: 10 step count: 4, color: black, value: watermelon
登入後複製
下面我們來做個大量資料的壓力測試，注意把rbtree_find方法裡的測試行註解掉，不然後果恐怕會比較嚇人：
ref#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "rbtree.h"
int main(int argc, char const *argv[])
{
double duration;
double room;
rbtree_t t = {};
rbtree_node_t s = {};
rbtree_init(&t, &s, rbtree_insert_value);
const int cnt = 1<<20;
const int max_len = 15;
#define TEST_VALUES {"apple", "banana", "cherry", "grape", "lemon", "mango", "pear", "pineapple", "strawberry", "watermelon"}
/* for gcc */
char* v[] = TEST_VALUES;
/* for g++ */
// char v[][max_len] = TEST_VALUES;
/* Default stack size in Ubuntu Kylin 14.04 is 8MB. */
/* It's not enough. So I use memory in heap which offers a lot larger room. */
rbtree_node_t* n = (rbtree_node_t*)calloc(cnt, sizeof(rbtree_node_t));
int i;
long time1 = clock();
for (i = 0; i < cnt; i++)
{
n[i].key = i+1;
n[i].value = v[i%10];
rbtree_insert(&t, &n[i]);
}
long time2 = clock();
room = 48.0*cnt/(1<<20);
duration = (double)(time2 - time1) / CLOCKS_PER_SEC;
printf("Inserting %d nodes costs %.2fMB and spends %f seconds.\n", cnt, room, duration);
const int search_cnt = 1<<10;
srand( (unsigned int)time(0) );
for( i = 0 ; i < search_cnt ; i++ )
{
rbtree_find(&t, (rand()%cnt)+1);
}
long time3 = clock();
duration = (double)(time3 - time2) / CLOCKS_PER_SEC;
printf("Searching %d nodes among %d spends %f seconds.\n", search_cnt, cnt, duration);
const int delete_cnt = 1<<10;
int nums[delete_cnt];
int num;
/* Let's hash! */
char* mark = (char*)calloc(cnt, sizeof(char));
memset(mark, 0, cnt*sizeof(char));
for(i = 0; i < delete_cnt; i++)
{
for(;;)
{
num = rand()%cnt;
if (mark[num] == 0)
{
mark[num] = 1;
nums[i] = num;
break;
}
}
}
long time4 = clock();
duration = (double)(time4 - time3) / CLOCKS_PER_SEC;
printf("Hash %d times spends %f seconds.\n", delete_cnt, duration);
for(i = 0; i < delete_cnt; i++)
{
rbtree_delete(&t, &n[nums[i]]);
}
long time5 = clock();
duration = (double)(time5 - time4) / CLOCKS_PER_SEC;
printf("Deleting %d nodes among %d spends %f seconds.\n", delete_cnt, cnt, duration);
free(mark);
free(n);
return 0;
}登入後複製
寫統計和遍歷方法去了。
版權聲明：本文為部落客原創文章，未經部落客允許不得轉載。
以上就介紹了nginx的資料結構2－自己動手重寫紅黑樹，包含了方面的內容，希望對PHP教學有興趣的朋友有所幫助。
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