redis源码分析(adlist)

typedef struct listNode {
struct listNode *prev;
struct listNode *next;
void *value;
} listNode;

首先定义了一个节点，包含前驱和后继以及对应的value

typedef struct listIter {
listNode *next;
int direction;
} listIter;
list的迭代器,next指针和迭代方向
typedef struct list {
listNode *head;
listNode *tail;
void *(*dup)(void *ptr);
void (*free)(void *ptr);
int (*match)(void *ptr, void *key);
unsigned long len;
} list;链表内容 head和tail指针分别指向收尾，另外三个函数指针代表在拷贝，删除，对比的时候，如果有函数可调用就调用当前次函数的逻辑，不然就调用自身的逻辑
/* Create a new list. The created list can be freed with
* AlFreeList(), but private value of every node need to be freed
* by the user before to call AlFreeList().
*
* On error, NULL is returned. Otherwise the pointer to the new list. */
list *listCreate(void)
{
struct list *list;

if ((list = zmalloc(sizeof(*list))) == NULL)
return NULL;
list->head = list->tail = NULL;
list->len = 0;
list->dup = NULL;
list->free = NULL;
list->match = NULL;
return list;
}

/* Free the whole list.
*
* This function can't fail. */
void listRelease(list *list)
{
unsigned long len;
listNode *current, *next;

current = list->head;
len = list->len;
while(len--) {
next = current->next;
if (list->free) list->free(current->value);
zfree(current);
current = next;
}
zfree(list);
}
创建和删除链表没什么说的

/* Add a new node to the list, to head, containing the specified 'value'
* pointer as value.
*
* On error, NULL is returned and no operation is performed (i.e. the
* list remains unaltered).
* On success the 'list' pointer you pass to the function is returned. */
list *listAddNodeHead(list *list, void *value)
{
listNode *node;

if ((node = zmalloc(sizeof(*node))) == NULL)
return NULL;
node->value = value;

//长度为0的，增加一个那么头尾指针都指向这个节点

//先让node的前驱指向null，node的后继指向头节点，然后让头节点的前驱指向node，最后在把头节点指向新的Node节点

if (list->len == 0) {
list->head = list->tail = node;
node->prev = node->next = NULL;
} else {
node->prev = NULL;
node->next = list->head;
list->head->prev = node;
list->head = node;
}
list->len++;
return list;
}

在头和尾部ADD道理一致

list *listInsertNode(list *list, listNode *old_node, void *value, int after) {
listNode *node;

if ((node = zmalloc(sizeof(*node))) == NULL)
return NULL;
node->value = value;

//在old_node前还是后insert
if (after) {
node->prev = old_node;
node->next = old_node->next;
if (list->tail == old_node) {
list->tail = node;
}
} else {
node->next = old_node;
node->prev = old_node->prev;
if (list->head == old_node) {
list->head = node;
}
}
if (node->prev != NULL) {
node->prev->next = node;
}
if (node->next != NULL) {
node->next->prev = node;
}
list->len++;
return list;
}