我借鉴的是u-boot版本号为2012.04.01 这个可以在UBOOT的主Makefile中查到，kernel版本号为3.4.20 。两个都可以。以u-boot为例，打开u-boot目录下的lib目录，我们可以看到有crc7,16,32,md5等等，我们的目标是rbtree.c。我们把这个文件打开看看

/*
Red Black Trees
(C) 1999 Andrea Arcangeli <andrea@suse.de>
(C) 2002 David Woodhouse <dwmw2@infradead.org>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

linux/lib/rbtree.c
*/

#include <ubi_uboot.h>
#include <linux/rbtree.h>

static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
{
struct rb_node *right = node->rb_right;
struct rb_node *parent = rb_parent(node);

if ((node->rb_right = right->rb_left))
rb_set_parent(right->rb_left, node);
right->rb_left = node;

rb_set_parent(right, parent);

if (parent)
{
if (node == parent->rb_left)
parent->rb_left = right;
else
parent->rb_right = right;
}
else
root->rb_node = right;
rb_set_parent(node, right);
}

static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
{
struct rb_node *left = node->rb_left;
struct rb_node *parent = rb_parent(node);

if ((node->rb_left = left->rb_right))
rb_set_parent(left->rb_right, node);
left->rb_right = node;

rb_set_parent(left, parent);

if (parent)
{
if (node == parent->rb_right)
parent->rb_right = left;
else
parent->rb_left = left;
}
else
root->rb_node = left;
rb_set_parent(node, left);
}

void rb_insert_color(struct rb_node *node, struct rb_root *root)
{
struct rb_node *parent, *gparent;

while ((parent = rb_parent(node)) && rb_is_red(parent))
{
gparent = rb_parent(parent);

if (parent == gparent->rb_left)
{
{
register struct rb_node *uncle = gparent->rb_right;
if (uncle && rb_is_red(uncle))
{
rb_set_black(uncle);
rb_set_black(parent);
rb_set_red(gparent);
node = gparent;
continue;
}
}

if (parent->rb_right == node)
{
register struct rb_node *tmp;
__rb_rotate_left(parent, root);
tmp = parent;
parent = node;
node = tmp;
}

rb_set_black(parent);
rb_set_red(gparent);
__rb_rotate_right(gparent, root);
} else {
{
register struct rb_node *uncle = gparent->rb_left;
if (uncle && rb_is_red(uncle))
{
rb_set_black(uncle);
rb_set_black(parent);
rb_set_red(gparent);
node = gparent;
continue;
}
}

if (parent->rb_left == node)
{
register struct rb_node *tmp;
__rb_rotate_right(parent, root);
tmp = parent;
parent = node;
node = tmp;
}

rb_set_black(parent);
rb_set_red(gparent);
__rb_rotate_left(gparent, root);
}
}

rb_set_black(root->rb_node);
}

static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
struct rb_root *root)
{
struct rb_node *other;

while ((!node || rb_is_black(node)) && node != root->rb_node)
{
if (parent->rb_left == node)
{
other = parent->rb_right;
if (rb_is_red(other))
{
rb_set_black(other);
rb_set_red(parent);
__rb_rotate_left(parent, root);
other = parent->rb_right;
}
if ((!other->rb_left || rb_is_black(other->rb_left)) &&
(!other->rb_right || rb_is_black(other->rb_right)))
{
rb_set_red(other);
node = parent;
parent = rb_parent(node);
}
else
{
if (!other->rb_right || rb_is_black(other->rb_right))
{
struct rb_node *o_left;
if ((o_left = other->rb_left))
rb_set_black(o_left);
rb_set_red(other);
__rb_rotate_right(other, root);
other = parent->rb_right;
}
rb_set_color(other, rb_color(parent));
rb_set_black(parent);
if (other->rb_right)
rb_set_black(other->rb_right);
__rb_rotate_left(parent, root);
node = root->rb_node;
break;
}
}
else
{
other = parent->rb_left;
if (rb_is_red(other))
{
rb_set_black(other);
rb_set_red(parent);
__rb_rotate_right(parent, root);
other = parent->rb_left;
}
if ((!other->rb_left || rb_is_black(other->rb_left)) &&
(!other->rb_right || rb_is_black(other->rb_right)))
{
rb_set_red(other);
node = parent;
parent = rb_parent(node);
}
else
{
if (!other->rb_left || rb_is_black(other->rb_left))
{
register struct rb_node *o_right;
if ((o_right = other->rb_right))
rb_set_black(o_right);
rb_set_red(other);
__rb_rotate_left(other, root);
other = parent->rb_left;
}
rb_set_color(other, rb_color(parent));
rb_set_black(parent);
if (other->rb_left)
rb_set_black(other->rb_left);
__rb_rotate_right(parent, root);
node = root->rb_node;
break;
}
}
}
if (node)
rb_set_black(node);
}

void rb_erase(struct rb_node *node, struct rb_root *root)
{
struct rb_node *child, *parent;
int color;

if (!node->rb_left)
child = node->rb_right;
else if (!node->rb_right)
child = node->rb_left;
else
{
struct rb_node *old = node, *left;

node = node->rb_right;
while ((left = node->rb_left) != NULL)
node = left;
child = node->rb_right;
parent = rb_parent(node);
color = rb_color(node);

if (child)
rb_set_parent(child, parent);
if (parent == old) {
parent->rb_right = child;
parent = node;
} else
parent->rb_left = child;

node->rb_parent_color = old->rb_parent_color;
node->rb_right = old->rb_right;
node->rb_left = old->rb_left;

if (rb_parent(old))
{
if (rb_parent(old)->rb_left == old)
rb_parent(old)->rb_left = node;
else
rb_parent(old)->rb_right = node;
} else
root->rb_node = node;

rb_set_parent(old->rb_left, node);
if (old->rb_right)
rb_set_parent(old->rb_right, node);
goto color;
}

parent = rb_parent(node);
color = rb_color(node);

if (child)
rb_set_parent(child, parent);
if (parent)
{
if (parent->rb_left == node)
parent->rb_left = child;
else
parent->rb_right = child;
}
else
root->rb_node = child;

color:
if (color == RB_BLACK)
__rb_erase_color(child, parent, root);
}

/*
* This function returns the first node (in sort order) of the tree.
*/
struct rb_node *rb_first(struct rb_root *root)
{
struct rb_node *n;

n = root->rb_node;
if (!n)
return NULL;
while (n->rb_left)
n = n->rb_left;
return n;
}

struct rb_node *rb_last(struct rb_root *root)
{
struct rb_node *n;

n = root->rb_node;
if (!n)
return NULL;
while (n->rb_right)
n = n->rb_right;
return n;
}

struct rb_node *rb_next(struct rb_node *node)
{
struct rb_node *parent;

if (rb_parent(node) == node)
return NULL;

/* If we have a right-hand child, go down and then left as far
as we can. */
if (node->rb_right) {
node = node->rb_right;
while (node->rb_left)
node=node->rb_left;
return node;
}

/* No right-hand children. Everything down and left is
smaller than us, so any ‘next’ node must be in the general
direction of our parent. Go up the tree; any time the
ancestor is a right-hand child of its parent, keep going
up. First time it’s a left-hand child of its parent, said
parent is our ‘next’ node. */
while ((parent = rb_parent(node)) && node == parent->rb_right)
node = parent;

return parent;
}

struct rb_node *rb_prev(struct rb_node *node)
{
struct rb_node *parent;

if (rb_parent(node) == node)
return NULL;

/* If we have a left-hand child, go down and then right as far
as we can. */
if (node->rb_left) {
node = node->rb_left;
while (node->rb_right)
node=node->rb_right;
return node;
}

/* No left-hand children. Go up till we find an ancestor which
is a right-hand child of its parent */
while ((parent = rb_parent(node)) && node == parent->rb_left)
node = parent;

return parent;
}

void rb_replace_node(struct rb_node *victim, struct rb_node *new,
struct rb_root *root)
{
struct rb_node *parent = rb_parent(victim);

/* Set the surrounding nodes to point to the replacement */
if (parent) {
if (victim == parent->rb_left)
parent->rb_left = new;
else
parent->rb_right = new;
} else {
root->rb_node = new;
}
if (victim->rb_left)
rb_set_parent(victim->rb_left, new);
if (victim->rb_right)
rb_set_parent(victim->rb_right, new);

/* Copy the pointers/colour from the victim to the replacement */
*new = *victim;
}

代码量不多，接近400行，从函数名就不难看出，这里只是一些红黑树的左右旋，替换节点以及一些节点定位。那么具体怎么使用呢？我们再看看头文件 —— 找到u-boot/include/linux/rbtree.h

/*
Red Black Trees
(C) 1999 Andrea Arcangeli <andrea@suse.de>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

linux/include/linux/rbtree.h

To use rbtrees you’ll have to implement your own insert and search cores.
This will avoid us to use callbacks and to drop drammatically performances.
I know it’s not the cleaner way, but in C (not in C++) to get
performances and genericity…

Some example of insert and search follows here. The search is a plain
normal search over an ordered tree. The insert instead must be implemented
int two steps: as first thing the code must insert the element in
order as a red leaf in the tree, then the support library function
rb_insert_color() must be called. Such function will do the
not trivial work to rebalance the rbtree if necessary.

———————————————————————–
static inline struct page * rb_search_page_cache(struct inode * inode,
unsigned long offset)
{
struct rb_node * n = inode->i_rb_page_cache.rb_node;
struct page * page;

while (n)
{
page = rb_entry(n, struct page, rb_page_cache);

if (offset < page->offset)
n = n->rb_left;
else if (offset > page->offset)
n = n->rb_right;
else
return page;
}
return NULL;
}

static inline struct page * __rb_insert_page_cache(struct inode * inode,
unsigned long offset,
struct rb_node * node)
{
struct rb_node ** p = &inode->i_rb_page_cache.rb_node;
struct rb_node * parent = NULL;
struct page * page;

while (*p)
{
parent = *p;
page = rb_entry(parent, struct page, rb_page_cache);

if (offset < page->offset)
p = &(*p)->rb_left;
else if (offset > page->offset)
p = &(*p)->rb_right;
else
return page;
}

rb_link_node(node, parent, p);

return NULL;
}

static inline struct page * rb_insert_page_cache(struct inode * inode,
unsigned long offset,
struct rb_node * node)
{
struct page * ret;
if ((ret = __rb_insert_page_cache(inode, offset, node)))
goto out;
rb_insert_color(node, &inode->i_rb_page_cache);
out:
return ret;
}
———————————————————————–
*/

#ifndef _LINUX_RBTREE_H
#define _LINUX_RBTREE_H

#include <linux/stddef.h>

struct rb_node
{
unsigned long rb_parent_color;
#define RB_RED 0
#define RB_BLACK 1
struct rb_node *rb_right;
struct rb_node *rb_left;
} __attribute__((aligned(sizeof(long))));
/* The alignment might seem pointless, but allegedly CRIS needs it */

struct rb_root
{
struct rb_node *rb_node;
};

#define rb_parent(r) ((struct rb_node *)((r)->rb_parent_color & ~3))
#define rb_color(r) ((r)->rb_parent_color & 1)
#define rb_is_red(r) (!rb_color(r))
#define rb_is_black(r) rb_color(r)
#define rb_set_red(r) do { (r)->rb_parent_color &= ~1; } while (0)
#define rb_set_black(r) do { (r)->rb_parent_color |= 1; } while (0)

static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
rb->rb_parent_color = (rb->rb_parent_color & 3) | (unsigned long)p;
}
static inline void rb_set_color(struct rb_node *rb, int color)
{
rb->rb_parent_color = (rb->rb_parent_color & ~1) | color;
}

#define RB_ROOT (struct rb_root) { NULL, }
#define rb_entry(ptr, type, member) container_of(ptr, type, member)

#define RB_EMPTY_ROOT(root) ((root)->rb_node == NULL)
#define RB_EMPTY_NODE(node) (rb_parent(node) == node)
#define RB_CLEAR_NODE(node) (rb_set_parent(node, node))

extern void rb_insert_color(struct rb_node *, struct rb_root *);
extern void rb_erase(struct rb_node *, struct rb_root *);

/* Find logical next and previous nodes in a tree */
extern struct rb_node *rb_next(struct rb_node *);
extern struct rb_node *rb_prev(struct rb_node *);
extern struct rb_node *rb_first(struct rb_root *);
extern struct rb_node *rb_last(struct rb_root *);

/* Fast replacement of a single node without remove/rebalance/add/rebalance */
extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
struct rb_root *root);

static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
struct rb_node ** rb_link)
{
node->rb_parent_color = (unsigned long )parent;
node->rb_left = node->rb_right = NULL;

*rb_link = node;
}

#endif /* _LINUX_RBTREE_H */

通过头文件的注释，老外已经非常友好地给出了一些示例代码。。那么接下来就是移植到我们stm32中了。
首先打开我们用的工程，创建一个Mylib目录，然后简单粗暴地，直接把我们的rbtree.c和rbtree.h直接丢进去。如果这时候我们直接点击编译的话，毫无疑问会产生一大堆的报错信息，我们先简单处理一下。首先是头文件的包含问题，将rbtree.h中 #include <linux/stddef.h> 修改为 #include <stddef.h>。然后点击编译，那么就会发现有些宏，我们是没有实现的。 rb_entry(ptr , type , member) 他封装了container_of，我们再将container_of 从u-boot的 common.h 中拷贝过来

/**
* container_of – cast a member of a structure out to the containing structure
* @ptr: the pointer to the member.
* @type: the type of the container struct this is embedded in.
* @member: the name of the member within the struct.
*
*/
#define container_of(ptr, type, member) ({ \
const typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr – offsetof(type,member) );})

但是我们发现keil5中使用的是标准c关键字，typeof属于拓展关键字，是没有办法使用的。这里我们只能读懂这个宏是做什么用的，然后想个其他办法去代替他。
这里初步分析，他定义了一个*__mptr指针，他的类型是和member成员一样的，并指向了ptr。 紧接着使用了offsetof宏对member成员在type中的位置求得偏移量，再使用__mptr减去这个偏移量。那么这里的重点实际上并不在前面的typeof，而是在第三行的偏移。这样我们也可以通过一样的手段对他进行偏移，我们修改如下

#define container_of(ptr, type, member) ((type*)( ((int)ptr) – (int)(& (((type*)0)->member) )))
1
后段使用stm32 stddef.h中offsetof也是没有问题的

/* EDG uses __INTADDR__ to avoid errors when strict */
#define offsetof(t, memb) ((__CLIBNS size_t)__INTADDR__(&(((t *)0)->memb)))
1
2
大部分工作实际上基本做完了，这里还是把代码贴出来

#ifndef _RBTREES_H_
#define _RBTREES_H_
//#include “project.h”
#include <stddef.h>

/**
* list_entry – get the struct for this entry
* @ptr: the &struct list_head pointer.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*/
#define list_entry(ptr, type, member) \
((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

/**
* container_of – cast a member of a structure out to the containing structure
* @ptr: the pointer to the member.
* @type: the type of the container struct this is embedded in.
* @member: the name of the member within the struct.
*
*/
#undef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)

//#define container_of(ptr, type, member) ({\
// const typeof( ((type *)0)->member ) *__mptr = (ptr);\
// (type *)( (char *)__mptr – offsetof(type,member) );})

// Keil5 not used GUN C . The typeof keyword not support. so make the following modifications ¡ý
#define container_of(ptr, type, member) ((type*)( ((int)ptr) – (int)(& (((type*)0)->member) )))

#define rb_entry(ptr, type, member) container_of(ptr, type, member)

struct rb_node
{
unsigned long rb_parent_color;
#define RB_RED 0
#define RB_BLACK 1
struct rb_node *rb_right;
struct rb_node *rb_left;
} __attribute__((aligned(sizeof(long))));
/* The alignment might seem pointless, but allegedly CRIS needs it */

struct rb_root
{
struct rb_node *rb_node;
};

#define rb_parent(r) ((struct rb_node *)((r)->rb_parent_color & ~3))
#define rb_color(r) ((r)->rb_parent_color & 1)
#define rb_is_red(r) (!rb_color(r))
#define rb_is_black(r) rb_color(r)
#define rb_set_red(r) do { (r)->rb_parent_color &= ~1; } while (0)
#define rb_set_black(r) do { (r)->rb_parent_color |= 1; } while (0)

static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
rb->rb_parent_color = (rb->rb_parent_color & 3) | (unsigned long)p;
}
static inline void rb_set_color(struct rb_node *rb, int color)
{
rb->rb_parent_color = (rb->rb_parent_color & ~1) | color;
}

#define RB_ROOT (struct rb_root) { NULL, }
#define rb_entry(ptr, type, member) container_of(ptr, type, member)

#define RB_EMPTY_ROOT(root) ((root)->rb_node == NULL)
#define RB_EMPTY_NODE(node) (rb_parent(node) == node)
#define RB_CLEAR_NODE(node) (rb_set_parent(node, node))

extern void rb_insert_color(struct rb_node *, struct rb_root *);
extern void rb_erase(struct rb_node *, struct rb_root *);

/* Find logical next and previous nodes in a tree */
extern struct rb_node *rb_next(struct rb_node *);
extern struct rb_node *rb_prev(struct rb_node *);
extern struct rb_node *rb_first(struct rb_root *);
extern struct rb_node *rb_last(struct rb_root *);

/* Fast replacement of a single node without remove/rebalance/add/rebalance */
extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
struct rb_root *root);

static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
struct rb_node ** rb_link)
{
node->rb_parent_color = (unsigned long )parent;
node->rb_left = node->rb_right = NULL;

*rb_link = node;
}
#endif
/******************* (C) COPYRIGHT 2019 Doon****************END OF FILE****/

好了…那么库就基本算移植完了，接下来就是怎么生成这个棵树↓

struct dev_info{
int addr;
};

typedef struct user_rb_s
{
struct rb_node user_node;
struct dev_info dev_info;
}user_rb_t;

/**
*@des: create a user node of rbtrees
*/
user_rb_t *create_user_node(struct dev_info *dev_info ){
user_rb_t *node;
node = (user_rb_t *)malloc(sizeof(user_rb_t));
if(node == NULL)
return node;

memset(node, 0, sizeof(user_rb_t));
memcpy((char *)&node->dev_info,dev_info,sizeof(struct dev_info));
return node;
}

/**
*@des: insert a user node.
*/
int user_rb_insert( struct rb_root *root , struct dev_info *dev_info ){
struct rb_node **new = &(root->rb_node);
struct rb_node *parent = NULL;
user_rb_t *goal_node = NULL;
int res=0;

find_addr = dev_info->mac
while(*new){
parent = *new;
goal_node = rb_entry( *new , user_rb_t , user_node );
res = dev_info->addr – goal_node->addr

if( res < 0 ){
new = &(( *new )->rb_left);
}else if( res > 0 ){
new = &(( *new )->rb_right);
}else{
return 0;
}
}

goal_node = create_user_node( dev_info );
if( goal_node == NULL ){
return -1;
}

//add new node
rb_link_node( &goal_node->user_node , parent , new );
//rebalance rbtree
rb_insert_color( &goal_node->user_node , root );

return 0;
}

/**
*@des: find the user node.
*/
struct dev_info *user_rb_find( struct rb_root *root ,int addr ){
struct rb_node *node = root->rb_node;
user_rb_t *goal_node = NULL;
int res=0;

while(node){
goal_node = rb_entry( node , user_rb_t , user_node );
res = ( addr – goal_node->addr );
if( res < 0 )
node = node->rb_left;
else if( res > 0 )
node = node->rb_right;
else
return &goal_node->dev_info;
}
return NULL;
}

int user_rb_delete( struct rb_root *root , int addr ){
user_rb_t *goal_node;
// Here changed the return of rb find . so we should offset the struct
goal_node = rb_entry( user_rb_find( root , addr ) , user_rb_t , user_node );
if( goal_node != NULL ){
rb_erase( &goal_node->user_node , root );
myfree( SRAMIN , goal_node );
return 0;
}else{
return -1;
}
}

基本就可以使用了，因为没有带上硬件，这里没有办法给大家看仿真和程序是怎么走的，很久没有写博客，有点不知道怎么写了，前面感觉写得很啰嗦，后面就直接贴上代码了。这类树状结构在查询的时候效率还是相当高的，比起每次遍历，最大查询次数大大缩减了。
————————————————
版权声明：本文为CSDN博主「_Doon。」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/weixin_40952498/article/details/103213089