Redis之2-双端链表（adlist.c,adlist.h）

adlist.c 、 adlist.h 双端链表数据结构的实现。
下面的注释来源于大牛博客，这里不重复造轮子，仅仅来说说我觉得比较不一样的地方以及设计的很棒的地方：

1.整个实现使用了函数式编程思想，使用了函数指针

2.将抽象的指针操作用宏定义封装重命名便于阅读

3.自己实现迭代器，可定义方向

4.设计了自己的内存分配和释放函数

5.在list内部留有了可用于自己实现复制和释放的函数通用式接口，但

暂时没想到为什么要留下这个接口

6.使用define条件编译选项，可避免重复包含**

/* adlist.h - A generic doubly linked list implementation * * Copyright (c) 2006-2012, Salvatore Sanfilippo <antirez at gmail dot com> * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * *   * Redistributions of source code must retain the above copyright notice, *     this list of conditions and the following disclaimer. *   * Redistributions in binary form must reproduce the above copyright *     notice, this list of conditions and the following disclaimer in the *     documentation and/or other materials provided with the distribution. *   * Neither the name of Redis nor the names of its contributors may be used *     to endorse or promote products derived from this software without *     specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */#ifndef __ADLIST_H__#define __ADLIST_H__/* Node, List, and Iterator are the only data structures used currently. *//* * 双端链表节点 */typedef struct listNode {    // 前置节点    struct listNode *prev;    // 后置节点    struct listNode *next;    // 节点的值    void *value;} listNode;/* * 双端链表迭代器 */typedef struct listIter {    // 当前迭代到的节点    listNode *next;    // 迭代的方向    int direction;} listIter;/* * 双端链表结构 */typedef struct list {    // 表头节点    listNode *head;    // 表尾节点    listNode *tail;    // 节点值复制函数    void *(*dup)(void *ptr);    // 节点值释放函数    void (*free)(void *ptr);    // 节点值对比函数    int (*match)(void *ptr, void *key);    // 链表所包含的节点数量    unsigned long len;} list;/* Functions implemented as macros */// 返回给定链表所包含的节点数量// T = O(1)#define listLength(l) ((l)->len)// 返回给定链表的表头节点// T = O(1)#define listFirst(l) ((l)->head)// 返回给定链表的表尾节点// T = O(1)#define listLast(l) ((l)->tail)// 返回给定节点的前置节点// T = O(1)#define listPrevNode(n) ((n)->prev)// 返回给定节点的后置节点// T = O(1)#define listNextNode(n) ((n)->next)// 返回给定节点的值// T = O(1)#define listNodeValue(n) ((n)->value)// 将链表 l 的值复制函数设置为 m// T = O(1)#define listSetDupMethod(l,m) ((l)->dup = (m))// 将链表 l 的值释放函数设置为 m// T = O(1)#define listSetFreeMethod(l,m) ((l)->free = (m))// 将链表的对比函数设置为 m// T = O(1)#define listSetMatchMethod(l,m) ((l)->match = (m))// 返回给定链表的值复制函数// T = O(1)#define listGetDupMethod(l) ((l)->dup)// 返回给定链表的值释放函数// T = O(1)#define listGetFree(l) ((l)->free)// 返回给定链表的值对比函数// T = O(1)#define listGetMatchMethod(l) ((l)->match)/* Prototypes */list *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  * * 迭代器进行迭代的方向 */// 从表头向表尾进行迭代#define AL_START_HEAD 0// 从表尾到表头进行迭代#define AL_START_TAIL 1#endif /* __ADLIST_H__ */

下面是实现文件

/* adlist.c - A generic doubly linked list implementation * * Copyright (c) 2006-2010, Salvatore Sanfilippo <antirez at gmail dot com> * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * *   * Redistributions of source code must retain the above copyright notice, *     this list of conditions and the following disclaimer. *   * Redistributions in binary form must reproduce the above copyright *     notice, this list of conditions and the following disclaimer in the *     documentation and/or other materials provided with the distribution. *   * Neither the name of Redis nor the names of its contributors may be used *     to endorse or promote products derived from this software without *     specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */#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. *//* * 创建一个新的链表 * * 创建成功返回链表，失败返回 NULL 。 * * T = O(1) */list *listCreate(void){    struct list *list;    // 分配内存    if ((list = zmalloc(sizeof(*list))) == NULL)        return NULL;    // 初始化属性    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. *//* * 释放整个链表，以及链表中所有节点 * * T = O(N) */void listRelease(list *list){    unsigned long len;    listNode *current, *next;    // 指向头指针    current = list->head;    // 遍历整个链表    len = list->len;    while(len--) {        next = current->next;        // 如果有设置值释放函数，那么调用它        if (list->free) list->free(current->value);        // 释放节点结构        zfree(current);        current = next;    }    // 释放链表结构    zfree(list);}/* Add a new node to the list, to head, contaning 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. *//* * 将一个包含有给定值指针 value 的新节点添加到链表的表头 * * 如果为新节点分配内存出错，那么不执行任何动作，仅返回 NULL * * 如果执行成功，返回传入的链表指针 * * T = O(1) */list *listAddNodeHead(list *list, void *value){    listNode *node;    // 为节点分配内存    if ((node = zmalloc(sizeof(*node))) == NULL)        return NULL;    // 保存值指针    node->value = value;    // 添加节点到空链表    if (list->len == 0) {        list->head = list->tail = node;        node->prev = node->next = NULL;    // 添加节点到非空链表    } else {        node->prev = NULL;        node->next = list->head;        list->head->prev = node;        list->head = node;    }    // 更新链表节点数    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. *//* * 将一个包含有给定值指针 value 的新节点添加到链表的表尾 * * 如果为新节点分配内存出错，那么不执行任何动作，仅返回 NULL * * 如果执行成功，返回传入的链表指针 * * T = O(1) */list *listAddNodeTail(list *list, void *value){    listNode *node;    // 为新节点分配内存    if ((node = zmalloc(sizeof(*node))) == NULL)        return NULL;    // 保存值指针    node->value = value;    // 目标链表为空    if (list->len == 0) {        list->head = list->tail = node;        node->prev = node->next = NULL;    // 目标链表非空    } else {        node->prev = list->tail;        node->next = NULL;        list->tail->next = node;        list->tail = node;    }    // 更新链表节点数    list->len++;    return list;}/* * 创建一个包含值 value 的新节点，并将它插入到 old_node 的之前或之后 * * 如果 after 为 0 ，将新节点插入到 old_node 之前。 * 如果 after 为 1 ，将新节点插入到 old_node 之后。 * * T = O(1) */list *listInsertNode(list *list, listNode *old_node, void *value, int after) {    listNode *node;    // 创建新节点    if ((node = zmalloc(sizeof(*node))) == NULL)        return NULL;    // 保存值    node->value = value;    // 将新节点添加到给定节点之后    if (after) {        node->prev = old_node;        node->next = old_node->next;        // 给定节点是原表尾节点        if (list->tail == old_node) {            list->tail = node;        }    // 将新节点添加到给定节点之前    } else {        node->next = old_node;        node->prev = old_node->prev;        // 给定节点是原表头节点        if (list->head == old_node) {            list->head = node;        }    }    // 更新新节点的前置指针    if (node->prev != NULL) {        node->prev->next = node;    }    // 更新新节点的后置指针    if (node->next != NULL) {        node->next->prev = node;    }    // 更新链表节点数    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. *//* * 从链表 list 中删除给定节点 node  *  * 对节点私有值(private value of the node)的释放工作由调用者进行。 * * T = O(1) */void listDelNode(list *list, listNode *node){    // 调整前置节点的指针    if (node->prev)        node->prev->next = node->next;    else        list->head = node->next;    // 调整后置节点的指针    if (node->next)        node->next->prev = node->prev;    else        list->tail = node->prev;    // 释放值    if (list->free) list->free(node->value);    // 释放节点    zfree(node);    // 链表数减一    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. *//* * 为给定链表创建一个迭代器， * 之后每次对这个迭代器调用 listNext 都返回被迭代到的链表节点 * * direction 参数决定了迭代器的迭代方向： *  AL_START_HEAD ：从表头向表尾迭代 *  AL_START_TAIL ：从表尾想表头迭代 * * T = O(1) */listIter *listGetIterator(list *list, int direction){    // 为迭代器分配内存    listIter *iter;    if ((iter = zmalloc(sizeof(*iter))) == NULL) return NULL;    // 根据迭代方向，设置迭代器的起始节点    if (direction == AL_START_HEAD)        iter->next = list->head;    else        iter->next = list->tail;    // 记录迭代方向    iter->direction = direction;    return iter;}/* Release the iterator memory *//* * 释放迭代器 * * T = O(1) */void listReleaseIterator(listIter *iter) {    zfree(iter);}/* Create an iterator in the list private iterator structure *//* * 将迭代器的方向设置为 AL_START_HEAD ， * 并将迭代指针重新指向表头节点。 * * T = O(1) */void listRewind(list *list, listIter *li) {    li->next = list->head;    li->direction = AL_START_HEAD;}/* * 将迭代器的方向设置为 AL_START_TAIL ， * 并将迭代指针重新指向表尾节点。 * * T = O(1) */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)); * } * * *//* * 返回迭代器当前所指向的节点。 * * 删除当前节点是允许的，但不能修改链表里的其他节点。 * * 函数要么返回一个节点，要么返回 NULL ，常见的用法是： * * iter = listGetIterator(list,<direction>); * while ((node = listNext(iter)) != NULL) { *     doSomethingWith(listNodeValue(node)); * } * * T = O(1) */listNode *listNext(listIter *iter){    listNode *current = iter->next;    if (current != NULL) {        // 根据方向选择下一个节点        if (iter->direction == AL_START_HEAD)            // 保存下一个节点，防止当前节点被删除而造成指针丢失            iter->next = current->next;        else            // 保存下一个节点，防止当前节点被删除而造成指针丢失            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. *//* * 复制整个链表。 * * 复制成功返回输入链表的副本， * 如果因为内存不足而造成复制失败，返回 NULL 。 * * 如果链表有设置值复制函数 dup ，那么对值的复制将使用复制函数进行， * 否则，新节点将和旧节点共享同一个指针。 * * 无论复制是成功还是失败，输入节点都不会修改。 * * T = O(N) */list *listDup(list *orig){    list *copy;    listIter *iter;    listNode *node;    // 创建新链表    if ((copy = listCreate()) == NULL)        return NULL;    // 设置节点值处理函数    copy->dup = orig->dup;    copy->free = orig->free;    copy->match = orig->match;    // 迭代整个输入链表    iter = listGetIterator(orig, AL_START_HEAD);    while((node = listNext(iter)) != NULL) {        void *value;        // 复制节点值到新节点        if (copy->dup) {            value = copy->dup(node->value);            if (value == NULL) {                listRelease(copy);                listReleaseIterator(iter);                return NULL;            }        } else            value = node->value;        // 将节点添加到链表        if (listAddNodeTail(copy, value) == NULL) {            listRelease(copy);            listReleaseIterator(iter);            return NULL;        }    }    // 释放迭代器    listReleaseIterator(iter);    // 返回副本    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. *//*  * 查找链表 list 中值和 key 匹配的节点。 *  * 对比操作由链表的 match 函数负责进行， * 如果没有设置 match 函数， * 那么直接通过对比值的指针来决定是否匹配。 * * 如果匹配成功，那么第一个匹配的节点会被返回。 * 如果没有匹配任何节点，那么返回 NULL 。 * * T = O(N) */listNode *listSearchKey(list *list, void *key){    listIter *iter;    listNode *node;    // 迭代整个链表    iter = listGetIterator(list, AL_START_HEAD);    while((node = listNext(iter)) != NULL) {        // 对比        if (list->match) {            if (list->match(node->value, key)) {                listReleaseIterator(iter);                // 找到                return node;            }        } else {            if (key == node->value) {                listReleaseIterator(iter);                // 找到                return node;            }        }    }    listReleaseIterator(iter);    // 未找到    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. *//* * 返回链表在给定索引上的值。 * * 索引以 0 为起始，也可以是负数， -1 表示链表最后一个节点，诸如此类。 * * 如果索引超出范围（out of range），返回 NULL 。 * * T = O(N) */listNode *listIndex(list *list, long index) {    listNode *n;    // 如果索引为负数，从表尾开始查找    if (index < 0) {        index = (-index)-1;        n = list->tail;        while(index-- && n) n = n->prev;    // 如果索引为正数，从表头开始查找    } 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. *//* * 取出链表的表尾节点，并将它移动到表头，成为新的表头节点。 * * T = O(1) */void listRotate(list *list) {    listNode *tail = list->tail;    if (listLength(list) <= 1) return;    /* Detach current tail */    // 取出表尾节点    list->tail = tail->prev;    list->tail->next = NULL;    /* Move it as head */    // 插入到表头    list->head->prev = tail;    tail->prev = NULL;    tail->next = list->head;    list->head = tail;}