DragonOS/kernel/lib/bitree.c

#include <common/bitree.h>
#include <mm/slab.h>
#include <common/errno.h>
#include <common/kfifo.h>
#include <common/string.h>
#include <debug/bug.h>

#define smaller(root, a, b) (root->cmp((a)->value, (b)->value) == -1)
#define equal(root, a, b) (root->cmp((a)->value, (b)->value) == 0)
#define greater(root, a, b) (root->cmp((a)->value, (b)->value) == 1)

/**
 * @brief 创建二叉搜索树
 *
 * @param node 根节点
 * @param cmp 比较函数
 * @param release 用来释放结点的value的函数
 * @return struct bt_root_t* 树根结构体
 */
struct bt_root_t *bt_create_tree(struct bt_node_t *node, int (*cmp)(void *a, void *b), int (*release)(void *value))
{
    if (node == NULL || cmp == NULL)
        return (void*)-EINVAL;

    struct bt_root_t *root = (struct bt_root_t *)kmalloc(sizeof(struct bt_root_t), 0);
    memset((void *)root, 0, sizeof(struct bt_root_t));
    root->bt_node = node;
    root->cmp = cmp;
    root->release = release;
    root->size = (node == NULL) ? 0 : 1;

    return root;
}

/**
 * @brief 创建结点
 *
 * @param left 左子节点
 * @param right 右子节点
 * @param value 当前节点的值
 * @return struct bt_node_t*
 */
struct bt_node_t *bt_create_node(struct bt_node_t *left, struct bt_node_t *right, struct bt_node_t *parent, void *value)
{
    struct bt_node_t *node = (struct bt_node_t *)kmalloc(sizeof(struct bt_node_t), 0);
    FAIL_ON_TO(node == NULL, nomem);
    memset((void *)node, 0, sizeof(struct bt_node_t));

    node->left = left;
    node->right = right;
    node->value = value;
    node->parent = parent;

    return node;
nomem:;
    return (void*)-ENOMEM;
}
/**
 * @brief 插入结点
 *
 * @param root 树根结点
 * @param value 待插入结点的值
 * @return int 返回码
 */
int bt_insert(struct bt_root_t *root, void *value)
{
    if (root == NULL)
        return -EINVAL;

    struct bt_node_t *this_node = root->bt_node;
    struct bt_node_t *last_node = NULL;
    struct bt_node_t *insert_node = bt_create_node(NULL, NULL, NULL, value);
    FAIL_ON_TO((uint64_t)insert_node == (uint64_t)(-ENOMEM), failed);

    while (this_node != NULL)
    {
        last_node = this_node;
        if (smaller(root, insert_node, this_node))
            this_node = this_node->left;
        else
            this_node = this_node->right;
    }

    insert_node->parent = last_node;
    if (unlikely(last_node == NULL))
        root->bt_node = insert_node;
    else
    {
        if (smaller(root, insert_node, last_node))
            last_node->left = insert_node;
        else
            last_node->right = insert_node;
    }
    ++root->size;
    return 0;

failed:;
    return -ENOMEM;
}

/**
 * @brief 搜索值为value的结点
 *
 * @param value 值
 * @param ret_addr 返回的结点基地址
 * @return int 错误码
 */
int bt_query(struct bt_root_t *root, void *value, uint64_t *ret_addr)
{
    struct bt_node_t *this_node = root->bt_node;
    struct bt_node_t tmp_node = {0};
    tmp_node.value = value;

    // 如果返回地址为0
    if (ret_addr == NULL)
        return -EINVAL;

    while (this_node != NULL && !equal(root, this_node, &tmp_node))
    {
        if (smaller(root, &tmp_node, this_node))
            this_node = this_node->left;
        else
            this_node = this_node->right;
    }

    if (this_node != NULL && equal(root, this_node, &tmp_node))
    {
        *ret_addr = (uint64_t)this_node;
        return 0;
    }
    else
    {
        // 找不到则返回-1，且addr设为0
        *ret_addr = NULL;
        return -1;
    }
}

static struct bt_node_t *bt_get_minimum(struct bt_node_t *this_node)
{
    while (this_node->left != NULL)
        this_node = this_node->left;
    return this_node;
}

/**
 * @brief 删除结点
 *
 * @param root 树根
 * @param value 待删除结点的值
 * @return int 返回码
 */
int bt_delete(struct bt_root_t *root, void *value)
{
    uint64_t tmp_addr;
    int retval;

    // 寻找待删除结点
    retval = bt_query(root, value, &tmp_addr);
    if (retval != 0 || tmp_addr == NULL)
        return retval;

    struct bt_node_t *this_node = (struct bt_node_t *)tmp_addr;
    struct bt_node_t *to_delete = NULL, *to_delete_son = NULL;
    if (this_node->left == NULL || this_node->right == NULL)
        to_delete = this_node;
    else
    {
        to_delete = bt_get_minimum(this_node->right);
        // 释放要被删除的值，并把下一个结点的值替换上来
        root->release(this_node->value);
        this_node->value = to_delete->value;
    }

    if (to_delete->left != NULL)
        to_delete_son = to_delete->left;
    else
        to_delete_son = to_delete->right;

    if (to_delete_son != NULL)
        to_delete_son->parent = to_delete->parent;

    if (to_delete->parent == NULL)
        root->bt_node = to_delete_son;
    else
    {
        if (to_delete->parent->left == to_delete)
            to_delete->parent->left = to_delete_son;
        else
            to_delete->parent->right = to_delete_son;
    }

    --root->size;
    // 释放最终要删除的结点的对象
    kfree(to_delete);
}

/**
 * @brief 释放整个二叉搜索树
 *
 * @param root 树的根节点
 * @return int 错误码
 */
int bt_destroy_tree(struct bt_root_t *root)
{
    // 新建一个kfifo缓冲区，将指向结点的指针存入fifo队列
    // 注：为了将指针指向的地址存入队列，我们需要对指针取地址
    struct kfifo_t fifo;
    kfifo_alloc(&fifo, ((root->size + 1) / 2) * sizeof(struct bt_node_t *), 0);
    kfifo_in(&fifo, (void *)&(root->bt_node), sizeof(struct bt_node_t *));

    // bfs
    while (!kfifo_empty(&fifo))
    {
        // 取出队列头部的结点指针
        struct bt_node_t *nd;
        int count = kfifo_out(&fifo, &nd, sizeof(uint64_t));

        // 将子节点加入队列
        if (nd->left != NULL)
            kfifo_in(&fifo, (void *)&(nd->left), sizeof(struct bt_node_t *));

        if (nd->right != NULL)
            kfifo_in(&fifo, (void *)&(nd->right), sizeof(struct bt_node_t *));

        // 销毁当前节点
        root->release(nd->value);
        kfree(nd);
    }

    kfifo_free_alloc(&fifo);

    return 0;
}