Redis源码分析（二）--结构体分析(1)

           继上次的redis源码分析(一)之后，本人开始订制着一份非常伟大的计划-啃完redis源代码，也对他进行了切块划分，鉴于本人目前对他的整个运行流畅还不特别清楚的情况下，所以决定第一个要解决的就是与逻辑无关的代码，也就是一些基本模块，因为是相互独立的，所以不会影响整体的阅读，所以第一个开刀的就是结构体模块了。结构体模块我划分了差不多10个文件的样子，今天看的主要是adlist.c的文件，收获有如下

1.真心的帮我把数据结构的链表操作复习了一遍

2.还有给人感觉最深的就是函数编程的思想无处不在，并没有明确的数据类型，结构体里的各种函数指针的调用，函数作为参数存在的频率非常高

3.让我见识到了C语言中迭代器还能这么写，像用过高级语言的java，C#语言的同学肯定感觉迭代器Iterator嘛，不很简单嘛，一句话的事呗，但是C语言中没有现成的方法，怎么实现，adlist.c给我们提供了一种很简洁的写法.

下面给出我分析的2个文件，一个是.h头文件，一个是.c的具体文件(我上面提到的3点可以着重看看出现的地方):

/* 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. *//* listNode结点 */typedef struct listNode {//结点的前一结点    struct listNode *prev;    //结点的下一结点    struct listNode *next;    //Node的函数指针    void *value;} listNode;/* list迭代器，只能为单向 */typedef struct listIter {//当前迭代位置的下一结点    listNode *next;    //迭代器的方向    int direction;} listIter;/* listNode 列表 */typedef struct list {//列表头结点    listNode *head;    //列表尾结点    listNode *tail;        /* 下面3个方法为所有结点公用的方法，分别在相应情况下回调用 */    //复制函数指针    void *(*dup)(void *ptr);    //释放函数指针    void (*free)(void *ptr);   //匹配函数指针    int (*match)(void *ptr, void *key);    //列表长度    unsigned long len;} list;/* Functions implemented as macros *//* 宏定义了一些基本操作 */#define listLength(l) ((l)->len)   //获取list长度#define listFirst(l) ((l)->head)   //获取列表首部#define listLast(l) ((l)->tail)    //获取列表尾部#define listPrevNode(n) ((n)->prev)  //给定结点的上一结点#define listNextNode(n) ((n)->next)  //给定结点的下一节点#define listNodeValue(n) ((n)->value) //给点的结点的值，这个value不是一个数值类型，而是一个函数指针#define listSetDupMethod(l,m) ((l)->dup = (m))  //列表的复制方法的设置#define listSetFreeMethod(l,m) ((l)->free = (m)) //列表的释放方法的设置#define listSetMatchMethod(l,m) ((l)->match = (m)) //列表的匹配方法的设置#define listGetDupMethod(l) ((l)->dup) //列表的复制方法的获取#define listGetFree(l) ((l)->free)     //列表的释放方法的获取#define listGetMatchMethod(l) ((l)->match) //列表的匹配方法的获取/* Prototypes *//* 定义了方法的原型 */list *listCreate(void);   //创建list列表void listRelease(list *list);  //列表的释放list *listAddNodeHead(list *list, void *value);  //添加列表头结点list *listAddNodeTail(list *list, void *value);  //添加列表尾结点list *listInsertNode(list *list, listNode *old_node, void *value, int after);  //某位置上插入及结点void listDelNode(list *list, listNode *node);  //列表上删除给定的结点listIter *listGetIterator(list *list, int direction);  //获取列表给定方向上的迭代器listNode *listNext(listIter *iter);  //获取迭代器内的下一结点void listReleaseIterator(listIter *iter);  //释放列表迭代器 list *listDup(list *orig);  //列表的复制listNode *listSearchKey(list *list, void *key); //关键字搜索具体结点listNode *listIndex(list *list, long index);   //下标索引具体的结点void listRewind(list *list, listIter *li);    // 重置迭代器为方向从头开始 void listRewindTail(list *list, listIter *li); //重置迭代器为方向从尾部开始 void listRotate(list *list);  //列表旋转操作，方法名说的很玄乎，具体只能到实现里去看了/* Directions for iterators *//* 定义2个迭代方向，从头部开始往尾部，第二个从尾部开始向头部 */#define AL_START_HEAD 0#define AL_START_TAIL 1#endif /* __ADLIST_H__ */

adlist.c:

/* 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. */ /* 创建结点列表 */list *listCreate(void){    struct list *list;//申请空间，如果失败了就直接返回NULL    if ((list = zmalloc(sizeof(*list))) == NULL)        return NULL;    //初始化操作，头尾结点，，3个公共的函数指针全部赋值为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. *//* 释放整个列表 */void listRelease(list *list){    unsigned long len;    listNode *current, *next;//找到当前结点，也就是头结点    current = list->head;    len = list->len;    while(len--) {    //while循环依次释放结点        next = current->next;        //如果列表有free释放方法定义，每个结点都必须调用自己内部的value方法        if (list->free) list->free(current->value);        //采用redis新定义的在zfree方式释放结点，与zmalloc对应，不是free！！         zfree(current);        current = next;    }    //最后再次释放list同样是zfree    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. */ /* 列表添加头结点 */list *listAddNodeHead(list *list, void *value){    listNode *node;//定义新的listNode，并赋值函数指针    if ((node = zmalloc(sizeof(*node))) == NULL)        return NULL;    node->value = value;    if (list->len == 0) {    //当此时没有任何结点时，头尾结点是同一个结点，前后指针为NULL        list->head = list->tail = node;        node->prev = node->next = NULL;    } else {    //设置此结点next与前头结点的位置关系        node->prev = NULL;        node->next = list->head;        list->head->prev = node;        list->head = node;    }        //结点计数递增并返回    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. */ /* 列表添加尾结点，操作大体上与增加头结点一样，不加以描述了 */list *listAddNodeTail(list *list, void *value){    listNode *node;    if ((node = zmalloc(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 = list->tail;        node->next = NULL;        list->tail->next = node;        list->tail = node;    }    list->len++;    return list;}/* 在old_node结点的前面或后面插入新结点 */list *listInsertNode(list *list, listNode *old_node, void *value, int after) {    listNode *node;//新申请结点，并赋值好函数指针    if ((node = zmalloc(sizeof(*node))) == NULL)        return NULL;    node->value = value;        if (after) {    //如果是在目标结点的后面插入的情况，将新结点的next指针指向老结点的next        node->prev = old_node;        node->next = old_node->next;        if (list->tail == old_node) {        //如果老结点已经是最后一个结点了，则新的结点直接成为尾部结点            list->tail = node;        }    } else {    //如果是在目标结点的前面插入的情况，将新结点的preview指针指向老结点的preview        node->next = old_node;        node->prev = old_node->prev;        if (list->head == old_node) {        //如果老结点已经是头结点了，则新的结点直接成为头部结点            list->head = node;        }    }    //检查Node的前后结点还有没有未连接的操作    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. *//* 列表删除某结点 */void listDelNode(list *list, listNode *node){    if (node->prev)    //如果结点prev结点存在，prev的结点的下一及诶单指向Node的next结点        node->prev->next = node->next;    else    //如果不存在说明是被删除的是头结点，则重新赋值Node的next为新头结点        list->head = node->next;     //后半操作类似    if (node->next)        node->next->prev = node->prev;    else        list->tail = node->prev;    //同样要调用list的free函数    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. *//* 获取列表呢迭代器 */listIter *listGetIterator(list *list, int direction){    listIter *iter;//申请空间，失败了就直接返回NULL    if ((iter = zmalloc(sizeof(*iter))) == NULL) return NULL;    if (direction == AL_START_HEAD)    //如果方向定义的是从头开始，则迭代器的next指针指向列表头结点        iter->next = list->head;    else    //如果方向定义的是从尾开始，则迭代器的next指针指向列表尾结点        iter->next = list->tail;     //赋值好迭代器方向并返回    iter->direction = direction;    return iter;}/* Release the iterator memory *//* 释放迭代器内存 */void listReleaseIterator(listIter *iter) {    zfree(iter);}/* Create an iterator in the list private iterator structure *//* 相当于重置迭代器为方向从头开始 */void listRewind(list *list, listIter *li) {    li->next = list->head;    li->direction = AL_START_HEAD;}/* 重置迭代器为方向从尾部开始 */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)); * } * * */ /* 根据迭代器获取下一结点 */listNode *listNext(listIter *iter){//获取当前迭代器的当前结点    listNode *current = iter->next;    if (current != NULL) {        if (iter->direction == AL_START_HEAD)        //如果方向为从头部开始，则当前结点等于当前的结点的下一结点            iter->next = current->next;        else        //如果方向为从尾部开始，则当前结点等于当前的结点的上一结点            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. *//* 列表赋值方法，传入的参数为原始列表 */list *listDup(list *orig){    list *copy;    listIter *iter;    listNode *node;//如果创建列表失败则直接返回    if ((copy = listCreate()) == NULL)        return NULL;    //为新列表赋值好3个函数指针    copy->dup = orig->dup;    copy->free = orig->free;    copy->match = orig->match;    //获得从头方向开始的迭代器    iter = listGetIterator(orig, AL_START_HEAD);    while((node = listNext(iter)) != NULL) {    //从前往后遍历结点        void *value;        if (copy->dup) {        //如果定义了列表复制方法，则调用dup方法            value = copy->dup(node->value);            if (value == NULL) {            //如果发生OOM内存溢出问题，直接释放所有空间                listRelease(copy);                listReleaseIterator(iter);                return NULL;            }        } else        //没定义直接复制函数指针            value = node->value;        if (listAddNodeTail(copy, value) == NULL) {        //后面的结点都是从尾部逐一添加结点，如果内存溢出，同上操作            listRelease(copy);            listReleaseIterator(iter);            return NULL;        }    }    //最后释放迭代器    listReleaseIterator(iter);    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. *//* 关键字搜索Node结点此时用到了list的match方法了 */listNode *listSearchKey(list *list, void *key){    listIter *iter;    listNode *node;//获取迭代器    iter = listGetIterator(list, AL_START_HEAD);    while((node = listNext(iter)) != NULL) {    //遍历循环        if (list->match) {        //如果定义了list的match方法，则调用match方法            if (list->match(node->value, key)) {            //如果方法返回true，则代表找到结点，释放迭代器                listReleaseIterator(iter);                return node;            }        } else {        //如果没有定义list 的match方法，则直接比较函数指针            if (key == node->value) {            //如果相等，则代表找到结点，释放迭代器                listReleaseIterator(iter);                return node;            }        }    }    listReleaseIterator(iter);    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. *//* 根据下标值返回相应的结点*//*下标有2种表示形式，从头往后一次0， 1， 2，...从后往前是 ...-3， -2， -1.-1为最后一个结点*/listNode *listIndex(list *list, long index) {    listNode *n;    if (index < 0) {    //如果index为负数，则从后往前数        index = (-index)-1;        n = list->tail;        while(index-- && n) n = n->prev;    } else {    //如果index为正数，则从前往后数        n = list->head;        while(index-- && n) n = n->next;    }    return n;}/* Rotate the list removing the tail node and inserting it to the head. *//* rotate操作其实就是把尾部结点挪到头部，原本倒数第二个结点变为尾部结点 */void listRotate(list *list) {    listNode *tail = list->tail;//如果长度为不足，直接返回，之前宏定义的方法    if (listLength(list) <= 1) return;    /* Detach current tail */    //替换新的尾部结点，原结点后挪一个位置    list->tail = tail->prev;    list->tail->next = NULL;        /* Move it as head */   //设置新结点    list->head->prev = tail;    tail->prev = NULL;    tail->next = list->head;    list->head = tail;}

其实目前网上的各种的解析都有吧，每个人阅读带给自己的感受是不一样的，只有自己亲手体验过才叫真的体会过，阅读代码的确会给人很多启发，非常严谨吧，每行代码，抱着一种学习，欣赏的心态看待代码。不错，良好的开始，继续坚持。