#ifndef __ADLIST_H__#define __ADLIST_H__/* Node, List, and Iterator are the only data structures used currently. */// redis的链表为双端链表// 节点的值为void*类型，从而可以保存不同类型的值// 结合dup,free,match函数实现链表的多态// 双端链表的节点typedef struct listNode {    struct listNode *prev; // 指向上一个节点    struct listNode *next; // 指向下一个节点    void *value; // 指向节点的值, void*类型，使得节点可以保存不同类型的值} listNode;// c语言实现c++中的迭代器！！！// 双端链表的迭代器，方便了遍历链表的操作// 根据direction，可设置为前向/反向迭代器typedef struct listIter {    listNode *next;    // 指向迭代器方向上下一个链表结点    int direction; // AL_START_HEAD=0：从头部往尾部方向移动；AL_START_TAIL=1：往尾部往头部方向移动} listIter;// 双端链表typedef struct list {    listNode *head; // 指向链表头节点    listNode *tail; // 指向链表尾节点    void *(*dup)(void *ptr); // 复制链表节点所保存的值    void (*free)(void *ptr); // 释放链表节点所保存的值    int (*match)(void *ptr, void *key); // 节点值比较函数    unsigned long len; // 链表的节点数目} list;/* Functions implemented as macros */// 通过宏来实现一些O(1)时间复杂度的函数#define listLength(l) ((l)->len)#define listFirst(l) ((l)->head)#define listLast(l) ((l)->tail)#define listPrevNode(n) ((n)->prev)#define listNextNode(n) ((n)->next)#define listNodeValue(n) ((n)->value)#define listSetDupMethod(l,m) ((l)->dup = (m))#define listSetFreeMethod(l,m) ((l)->free = (m))#define listSetMatchMethod(l,m) ((l)->match = (m))#define listGetDupMethod(l) ((l)->dup)#define listGetFree(l) ((l)->free)#define listGetMatchMethod(l) ((l)->match)/* Prototypes */// list数据结构相关的函数// 具体含义见adlist.clist *listCreate(void);void listRelease(list *list);list *listAddNodeHead(list *list, void *value);list *listAddNodeTail(list *list, void *value);list *listInsertNode(list *list, listNode *old_node, void *value, int after);void listDelNode(list *list, listNode *node);listIter *listGetIterator(list *list, int direction);listNode *listNext(listIter *iter);void listReleaseIterator(listIter *iter);list *listDup(list *orig);listNode *listSearchKey(list *list, void *key);listNode *listIndex(list *list, long index);void listRewind(list *list, listIter *li);void listRewindTail(list *list, listIter *li);void listRotate(list *list);/* Directions for iterators */// 迭代器方向的宏定义#define AL_START_HEAD 0#define AL_START_TAIL 1#endif /* __ADLIST_H__ */

/* adlist.c - A generic doubly linked list implementation */#include <stdlib.h>#include "adlist.h"#include "zmalloc.h"/* 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. */ // 创建一个链表// 返回值：list/NULLlist *listCreate(void){    struct list *list;    if ((list = zmalloc(sizeof(*list))) == NULL) // 为链表分配内存        return NULL;    // 初始化链表结构体的成员    list->head = list->tail = NULL;    list->len = 0;    list->dup = NULL;    list->free = NULL;    list->match = NULL;    return list; // 返回为新链表分配的内存的起始地址}/* Free the whole list. * * This function can‘t fail. */ // 释放链表及链表节点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); // 释放链表节点的值        zfree(current); // 释放链表节点        current = next;    }    zfree(list); // 释放链表}/* 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. */ // 从双端链表的头部插入新节点// 返回值：list/NULLlist *listAddNodeHead(list *list, void *value){    listNode *node;    if ((node = zmalloc(sizeof(*node))) == NULL)        return NULL;    node->value =http://www.mamicode.com/ value;    if (list->len == 0) { // 原链表为一空链表        list->head = list->tail = node;        node->prev = node->next = NULL;    } else {        // 插入到双端链表的头结点之前        node->prev = NULL;        node->next = list->head;        list->head->prev = node;        list->head = node;    }    list->len++;    return list;}/* Add a new node to the list, to tail, 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. */// 从双端链表的尾部插入新节点// 返回值：list/NULL list *listAddNodeTail(list *list, void *value){    listNode *node;    if ((node = zmalloc(sizeof(*node))) == NULL)        return NULL;    node->value =http://www.mamicode.com/ value;    if (list->len == 0) {        list->head = list->tail = node;        node->prev = node->next = NULL;    } else {        node->prev = list->tail;        node->next = NULL;        list->tail->next = node;        list->tail = node;    }    list->len++;    return list;}// 在链表list的节点old_node的前或后插入新节点// after为0，则在old_node之前插入；否则，在old_node之后插入// 返回值：list/NULLlist *listInsertNode(list *list, listNode *old_node, void *value, int after) {    listNode *node;    if ((node = zmalloc(sizeof(*node))) == NULL)        return NULL;    node->value =http://www.mamicode.com/ value;    if (after) { // old_node之后插入        node->prev = old_node;        node->next = old_node->next;        if (list->tail == old_node) {            list->tail = node;        }    } else { // old_node之前插入        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;}/* Remove the specified node from the specified list. * It‘s up to the caller to free the private value of the node. * * This function can‘t fail. */// 删除链表list中节点nodevoid listDelNode(list *list, listNode *node){    if (node->prev)        node->prev->next = node->next;    else        list->head = node->next;    if (node->next)        node->next->prev = node->prev;    else        list->tail = node->prev;    if (list->free) list->free(node->value);    zfree(node);    list->len--;}/* Returns a list iterator ‘iter‘. After the initialization every * call to listNext() will return the next element of the list. * * This function can‘t fail. */  // 返回链表的迭代器 // 返回值：list/NULLlistIter *listGetIterator(list *list, int direction){    listIter *iter;    if ((iter = zmalloc(sizeof(*iter))) == NULL) return NULL;    if (direction == AL_START_HEAD)        iter->next = list->head; // 设置为前向迭代器    else        iter->next = list->tail; // 设置为反向迭代器    iter->direction = direction;    return iter;}/* Release the iterator memory */// 释放迭代器的内存void listReleaseIterator(listIter *iter) {    zfree(iter);}/* Create an iterator in the list private iterator structure */// 回绕迭代器到链表头部void listRewind(list *list, listIter *li) {    li->next = list->head;    li->direction = AL_START_HEAD;}// 回绕迭代器到链表尾部void listRewindTail(list *list, listIter *li) {    li->next = list->tail;    li->direction = AL_START_TAIL;}/* Return the next element of an iterator. * It‘s valid to remove the currently returned element using * listDelNode(), but not to remove other elements. * * The function returns a pointer to the next element of the list, * or NULL if there are no more elements, so the classical usage patter * is: * * iter = listGetIterator(list,<direction>); * while ((node = listNext(iter)) != NULL) { *     doSomethingWith(listNodeValue(node)); * } * * */  // 返回迭代器所指向的元素，并将迭代器往其方向上移动一步 // 返回值：指向当前节点的指针/NULLlistNode *listNext(listIter *iter){    listNode *current = iter->next;    if (current != NULL) {        if (iter->direction == AL_START_HEAD)            iter->next = current->next;        else            iter->next = current->prev;    }    return current;}/* Duplicate the whole list. On out of memory NULL is returned. * On success a copy of the original list is returned. * * The ‘Dup‘ method set with listSetDupMethod() function is used * to copy the node value. Otherwise the same pointer value of * the original node is used as value of the copied node. * * The original list both on success or error is never modified. */  // 复制输入链表 // list*/NULLlist *listDup(list *orig){    list *copy;    listIter iter;    listNode *node;    if ((copy = listCreate()) == NULL) // 创建新链表        return NULL;    copy->dup = orig->dup;    copy->free = orig->free;    copy->match = orig->match;    listRewind(orig, &iter); // 回绕迭代器到链表头部    while((node = listNext(&iter)) != NULL) { // 遍历原链表，顺序取出节点        void *value;        if (copy->dup) {            value = copy->dup(node->value); // 通过list.dup函数复制节点值            if (value =http://www.mamicode.com/= NULL) {                listRelease(copy); // 出错释放链表                return NULL;            }        } else            value = node->value;        if (listAddNodeTail(copy, value) == NULL) { // 从新链表尾部插入值            listRelease(copy); // 出错释放链表            return NULL;        }    }    return copy;}/* Search the list for a node matching a given key. * The match is performed using the ‘match‘ method * set with listSetMatchMethod(). If no ‘match‘ method * is set, the ‘value‘ pointer of every node is directly * compared with the ‘key‘ pointer. * * On success the first matching node pointer is returned * (search starts from head). If no matching node exists * NULL is returned. */  // 返回链表中节点值与key相匹配的节点 // listNode*/NULLlistNode *listSearchKey(list *list, void *key){    listIter iter;    listNode *node;    listRewind(list, &iter);    while((node = listNext(&iter)) != NULL) {        if (list->match) {            if (list->match(node->value, key)) { // 调用list.match函数对节点值进行比较                return node;            }        } else {            if (key == node->value) {                return node;            }        }    }    return NULL;}/* Return the element at the specified zero-based index * where 0 is the head, 1 is the element next to head * and so on. Negative integers are used in order to count * from the tail, -1 is the last element, -2 the penultimate * and so on. If the index is out of range NULL is returned. */  // 返回给定索引位置的节点 // index=0，返回头结点 // index < 0，则从尾部开始返回，index = -1，返回尾部节点listNode *listIndex(list *list, long index) {    listNode *n;    if (index < 0) {        index = (-index)-1;        n = list->tail;        while(index-- && n) n = n->prev;    } else {        n = list->head;        while(index-- && n) n = n->next;    }    return n;}/* Rotate the list removing the tail node and inserting it to the head. */// 将尾部节点弹出，插入到链表头节点之前，成为新的表头节点void listRotate(list *list) {    listNode *tail = list->tail;    if (listLength(list) <= 1) return;    /* Detach current tail */    list->tail = tail->prev;    list->tail->next = NULL;    /* Move it as head */    list->head->prev = tail;    tail->prev = NULL;    tail->next = list->head;    list->head = tail;}