DOUBLE_NODE* DoubleLinkGetPrev(const DOUBLE_LINK* pDblLnk, const DOUBLE_NODE* pNode) { assert(IsValidDoubleLink(pDblLnk)); assert(IsValidDoubleNode(pDblLnk, pNode)); return pNode->pPrev; }什么意思

这是一个函数的定义，函数名为DoubleLinkGetPrev，它返回一个DOUBLE_NODE类型的指针。该函数的作用是获取双向链表中指定节点的前一个节点。

具体而言，该函数的第一个参数pDblLnk是一个指向DOUBLE_LINK类型的指针，表示要获取前一个节点的双向链表。函数首先使用assert函数检查pDblLnk指针所指向的对象是否为有效的双向链表。

该函数的第二个参数pNode是一个指向DOUBLE_NODE类型的指针，表示要获取前一个节点的节点。函数同样使用assert函数检查pNode指针所指向的对象是否为有效的双向链表节点。

最后，该函数直接返回pNode节点中的pPrev成员，即该节点的前一个节点的指针。需要注意的是，如果pNode指向的是双向链表的头节点，则返回的指针可能为空指针。

相关问题

请参考我给出的代码框架，实现对EMPLOYEE结构体为数据的双向链表的排序算法，要求按照按employeeId升序排列 typedef struct linkNode { void* data; //使用空指针使得NODE适配多种数据结构 struct linkNode* preNode; struct linkNode* nextNode; }LINKED_NODE; /*Define the struct of double linked list.*/ typedef struct { LINKED_NODE* head; LINKED_NODE* tail; size_t size; }DOUBLE_LINK_LIST; typedef struct { int employeeId; char name[20]; char ipAddress[30]; char seatNumber[20]; char group[10]; } EMPLOYEE; DOUBLE_LINK_LIST* createDoubleLinkedList() { DOUBLE_LINK_LIST* newList = (DOUBLE_LINK_LIST*)malloc(sizeof(DOUBLE_LINK_LIST)); newList->head = NULL; newList->tail = NULL; newList->size = 0; return newList; } void destroyDoubleLinkedList(DOUBLE_LINK_LIST* list) {} /*Add a new node before the head.*/ void insertHead(DOUBLE_LINK_LIST* list, void* data) // void执政适配其他data类型？ {} /*Add a new node after tail.*/ void insertTail(DOUBLE_LINK_LIST* list, void* data) // 如何适配其他data类型？ {} /*Insert a new node.*/ void insertNode(DOUBLE_LINK_LIST* list, void* data,int index) // 如何适配其他data类型？ {} void deleteHead(DOUBLE_LINK_LIST* list) {} void deleteTail(DOUBLE_LINK_LIST* list) {} void deleteNode(DOUBLE_LINK_LIST* list, int index) {} LINKED_NODE* getNode(DOUBLE_LINK_LIST* list, int index) {} /* 遍历链表，对每个节点执行指定操作*/ void traverseList(DOUBLE_LINK_LIST* list, void (*callback)(void*)) { LINKED_NODE* currentNode = list->head; while (currentNode != NULL) { callback(currentNode->data); currentNode = currentNode->nextNode; } } void printEmployee(void* data) {}

你可以使用以下代码来实现对EMPLOYEE结构体为数据的双向链表的排序算法，按照按employeeId升序排列：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct linkNode
{
	void* data; //使用空指针使得NODE适配多种数据结构
	struct linkNode* preNode;
	struct linkNode* nextNode;
} LINKED_NODE;

/*Define the struct of double linked list.*/
typedef struct
{
	LINKED_NODE* head;
	LINKED_NODE* tail;
	size_t size;
} DOUBLE_LINK_LIST;

typedef struct 
{
	int		employeeId;
	char	name[20];
	char	ipAddress[30];
	char	seatNumber[20];
	char	group[10];
} EMPLOYEE;

DOUBLE_LINK_LIST* createDoubleLinkedList()
{
	DOUBLE_LINK_LIST* newList = (DOUBLE_LINK_LIST*)malloc(sizeof(DOUBLE_LINK_LIST));
	newList->head = NULL;
	newList->tail = NULL;
	newList->size = 0;
	return newList;
}

void destroyDoubleLinkedList(DOUBLE_LINK_LIST* list)
{
	LINKED_NODE* currentNode = list->head;
	while (currentNode != NULL)
	{
		LINKED_NODE* nextNode = currentNode->nextNode;
		free(currentNode);
		currentNode = nextNode;
	}
	free(list);
}

/*Add a new node before the head.*/
void insertHead(DOUBLE_LINK_LIST* list, void* data)
{
	LINKED_NODE* newNode = (LINKED_NODE*)malloc(sizeof(LINKED_NODE));
	newNode->data = data;
	newNode->preNode = NULL;
	newNode->nextNode = list->head;

	if (list->head != NULL)
		list->head->preNode = newNode;

	list->head = newNode;

	if (list->tail == NULL)
		list->tail = newNode;

	list->size++;
}

/*Add a new node after tail.*/
void insertTail(DOUBLE_LINK_LIST* list, void* data)
{
	LINKED_NODE* newNode = (LINKED_NODE*)malloc(sizeof(LINKED_NODE));
	newNode->data = data;
	newNode->preNode = list->tail;
	newNode->nextNode = NULL;

	if (list->tail != NULL)
		list->tail->nextNode = newNode;

	list->tail = newNode;

	if (list->head == NULL)
		list->head = newNode;

	list->size++;
}

/*Insert a new node.*/
void insertNode(DOUBLE_LINK_LIST* list, void* data, int index)
{
	if (index < 0 || index > list->size)
	{
		printf("Invalid index\n");
		return;
	}

	if (index == 0)
	{
		insertHead(list, data);
		return;
	}

	if (index == list->size)
	{
		insertTail(list, data);
		return;
	}

	LINKED_NODE* currentNode = getNode(list, index);
	LINKED_NODE* newNode = (LINKED_NODE*)malloc(sizeof(LINKED_NODE));
	newNode->data = data;
	newNode->preNode = currentNode->preNode;
	newNode->nextNode = currentNode;

	currentNode->preNode->nextNode = newNode;
	currentNode->preNode = newNode;

	list->size++;
}

void deleteHead(DOUBLE_LINK_LIST* list)
{
	if (list->head == NULL)
		return;

	LINKED_NODE* oldHead = list->head;
	list->head = oldHead->nextNode;

	if (list->head != NULL)
		list->head->preNode = NULL;

	free(oldHead);
	list->size--;

	if (list->size == 0)
		list->tail = NULL;
}

void deleteTail(DOUBLE_LINK_LIST* list)
{
	if (list->tail == NULL)
		return;

	LINKED_NODE* oldTail = list->tail;
	list->tail = oldTail->preNode;

	if (list->tail != NULL)
		list->tail->nextNode = NULL;

	free(oldTail);
	list->size--;

	if (list->size == 0)
		list->head = NULL;
}

void deleteNode(DOUBLE_LINK_LIST* list, int index)
{
	if (index < 0 || index >= list->size)
	{
		printf("Invalid index\n");
		return;
	}

	if (index == 0)
	{
		deleteHead(list);
		return;
	}

	if (index == list->size - 1)
	{
		deleteTail(list);
		return;
	}

	LINKED_NODE* currentNode = getNode(list, index);
	currentNode->preNode->nextNode = currentNode->nextNode;
	currentNode->nextNode->preNode = currentNode->preNode;

	free(currentNode);
	list->size--;
}

LINKED_NODE* getNode(DOUBLE_LINK_LIST* list, int index)
{
	if (index < 0 || index >= list->size)
	{
		printf("Invalid index\n");
		return NULL;
	}

	LINKED_NODE* currentNode = list->head;
	int i = 0;

	while (i < index)
	{
		currentNode = currentNode->nextNode;
		i++;
	}

	return currentNode;
}

void traverseList(DOUBLE_LINK_LIST* list, void (*callback)(void*))
{
	LINKED_NODE* currentNode = list->head;
	while (currentNode != NULL)
	{
		callback(currentNode->data);
		currentNode = currentNode->nextNode;
	}
}

void printEmployee(void* data)
{
	EMPLOYEE* employee = (EMPLOYEE*)data;
	printf("Employee ID: %d, Name: %s\n", employee->employeeId, employee->name);
}

int compareEmployee(const void* a, const void* b)
{
	EMPLOYEE* employeeA = (EMPLOYEE*)a;
	EMPLOYEE* employeeB = (EMPLOYEE*)b;

	return employeeA->employeeId - employeeB->employeeId;
}

void sortList(DOUBLE_LINK_LIST* list)
{
	size_t dataSize = sizeof(EMPLOYEE);
	EMPLOYEE** employeeArray = (EMPLOYEE**)malloc(list->size * sizeof(EMPLOYEE*));

	LINKED_NODE* currentNode = list->head;
	size_t i = 0;

	while (currentNode != NULL)
	{
		employeeArray[i] = (EMPLOYEE*)currentNode->data;
		currentNode = currentNode->nextNode;
		i++;
	}

	qsort(employeeArray, list->size, dataSize, compareEmployee);

	currentNode = list->head;
	i = 0;

	while (currentNode != NULL)
	{
		currentNode->data = employeeArray[i];
		currentNode = currentNode->nextNode;
		i++;
	}

	free(employeeArray);
}

int main()
{
	DOUBLE_LINK_LIST* list = createDoubleLinkedList();

	EMPLOYEE* employee1 = (EMPLOYEE*)malloc(sizeof(EMPLOYEE));
	employee1->employeeId = 2;
	strcpy(employee1->name, "John");
	insertHead(list, employee1);

	EMPLOYEE* employee2 = (EMPLOYEE*)malloc(sizeof(EMPLOYEE));
	employee2->employeeId = 1;
	strcpy(employee2->name, "Alice");
	insertHead(list, employee2);

	EMPLOYEE* employee3 = (EMPLOYEE*)malloc(sizeof(EMPLOYEE));
	employee3->employeeId = 3;
	strcpy(employee3->name, "Bob");
	insertHead(list, employee3);

	printf("Before sorting:\n");
	traverseList(list, printEmployee);

	sortList(list);

	printf("\nAfter sorting:\n");
	traverseList(list, printEmployee);

	destroyDoubleLinkedList(list);

	return 0;
}

这段代码首先定义了双向链表的结构体和EMPLOYEE结构体，然后实现了双向链表的创建、销毁、插入、删除、遍历等操作。其中，`sortList`函数使用了快速排序算法对双向链表中的EMPLOYEE结构体按照employeeId升序进行排序。在`main`函数中，创建了一个双向链表并插入了三个EMPLOYEE结构体，然后调用`sortList`函数对链表进行排序并输出结果。

请注意，在代码中使用了动态内存分配（`malloc`）来分配内存，并在适当的时候使用了`free`来释放内存，以防止内存泄漏。

const void *of_get_property(const struct device_node *np, const char *propname, int *lenp);里面的lenp具体什么意思，可以举例说明吗

`lenp`是一个指针，用于返回属性值的长度。当调用`of_get_property()`函数来获取设备树上某个节点的属性值时，`lenp`指向的地址会被修改，以便返回属性值的长度。

以下是一个示例：

struct device_node *np = of_find_node_by_name(NULL, "my_device");
if (np) {
    const char *prop_val;
    int len;
    prop_val = of_get_property(np, "compatible", &len);
    if (prop_val) {
        pr_info("Compatible String: %s, length: %d\n", prop_val, len);
    }
    of_node_put(np);
}

在上面的示例中，我们使用`of_get_property()`函数来获取节点`my_device`的`compatible`属性的值，并将长度存储在`len`变量中。如果该属性存在，则打印出字符串和长度。