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Redis源码分析(二)--结构体分析(1)

Androidlushangderen 2014-10-06

相关推荐:Redis源码分析(三)---dict哈希结构

昨天分析完adlist的Redis代码,今天马上马不停蹄的继续学习Redis代码中的哈希部分的结构学习,不过在这里他不叫什么hashMap,而是叫dict,

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;

}

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//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。

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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...

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