Redis source code-data structure Adlist double-ended list

Redis's Adlist implements a double-ended list of data structures, such as the following:
Linked list node definition:

typedef struct LISTNODE {    struct listnode *prev;    struct ListNode *next;    void *value;} ListNode;

Linked List definition:

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

Of the three function pointers in the first without the tube, followed by the look at the details of what to do, also implemented an iterator, a little C + + taste in the inside

typedef struct LISTITER {    listnode *next;    int direction;} Listiter;

Linked list three elements. Create, insert, and delete

List *listcreate (void) {    struct list *list;    if (list = malloc (sizeof (*list)) = = null)        return null;    List->head = List->tail = NULL;    List->len = 0;    List->dup = NULL;    List->free = NULL;    List->match = NULL;    return list;}

Inserts are divided into from the head insert and the end insert, the source implementation of the head has a very clear gaze, tell the function of some details, the author is very attentively:

List *listaddnodehead (list *list, void *value) {    ListNode *node;    if (node = malloc (sizeof (*node)) = = null)        return null;    Node->value = value;    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;}

Freeing memory

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);        Free (current);        current = next;    }    Free (list);}

Iterators are created and can be emulated in the future, with the iterator in the direction of:

/* Returns A list iterator ' iter '. After the initialization every * call to Listnext () would return the next element of the list. * * This function can ' t fail. */listiter *listgetiterator (list *list, int direction) {    listiter *iter;    if (iter = malloc (sizeof (*iter)) = = null) return null;    if (direction = = Al_start_head)        iter->next = list->head;    else        Iter->next = list->tail;    Iter->direction = direction;    return ITER;}

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Redis source code-data structure Adlist double-ended list