这是对adlist结构体的定义,与其他代码关联不大。
#ifndef __ADLIST_H__
#define __ADLIST_H__
/* Node, List, and Iterator are the only data structures used currently. */
/*节点*/
typedef struct listNode {
struct listNode *prev;//前一节点
struct listNode *next;//后一节点
void *value;//当前节点的值
} listNode;
/*迭代器,只能向某一个方向迭代*/
typedef struct listIter {
listNode *next;//下一节点
int direction;//迭代方向
} listIter;
/*列表*/
typedef struct list {
listNode *head;//头结点
listNode *tail;//尾节点
//函数指针
void *(*dup)(void *ptr);//复制一个节点的值
void (*free)(void *ptr);//释放一个节点的值的空间
int (*match)(void *ptr, void *key);//根据key和值,匹配一个节点
unsigned long len;//列表长度
} list;
/* Functions implemented as macros */
/* 常用操作的宏定义 */
#define listLength(l) ((l)->len)//得到list长度
#define listFirst(l) ((l)->head)//得到头结点
#define listLast(l) ((l)->tail)//得到尾节点
#define listPrevNode(n) ((n)->prev)//得到前一个节点
#define listNextNode(n) ((n)->next)//得到下一个节点
#define listNodeValue(n) ((n)->value)//得到当前节点的值
#define listSetDupMethod(l,m) ((l)->dup = (m))//设置复制节点函数
#define listSetFreeMethod(l,m) ((l)->free = (m))//设置释放节点函数
#define listSetMatchMethod(l,m) ((l)->match = (m))//设置匹配节点函数
#define listGetDupMethod(l) ((l)->dup)//获取复制节点函数
#define listGetFree(l) ((l)->free)//获取释放节点函数
#define listGetMatchMethod(l) ((l)->match)//获取匹配节点函数
/* Prototypes */
list *listCreate(void);//生成list
void listRelease(list *list);//释放整个list
void listEmpty(list *list);//清空list
list *listAddNodeHead(list *list, void *value);//添加头结点
list *listAddNodeTail(list *list, void *value);//添加尾节点
list *listInsertNode(list *list, listNode *old_node, void *value, int after);//在某个位置上插入节点
void listDelNode(list *list, listNode *node);//删除节点
listIter *listGetIterator(list *list, int direction);//获取迭代器
listNode *listNext(listIter *iter);//获取迭代器中的下一节点
void listReleaseIterator(listIter *iter);//释放迭代器
list *listDup(list *orig);//列表复制
listNode *listSearchKey(list *list, void *key);//根据key得到相应节点
listNode *listIndex(list *list, long index);//得到给定下标的节点
void listRewind(list *list, listIter *li);//重置迭代器,从头开始
void listRewindTail(list *list, listIter *li);//重置迭代器,从尾开始
void listRotate(list *list);//反转列表,把尾节点插入到头部
void listJoin(list *l, list *o);//插入一个列表
/* Directions for iterators */
/*迭代器的方向*/
#define AL_START_HEAD 0//从头向尾
#define AL_START_TAIL 1//从尾向头
#endif /* __ADLIST_H__ */
#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. */
/* 创建新列表。
可以使用 AlFreeList () 释放创建的列表, 但在调用 AlFreeList () 之前, 用户需要释放每个节点的私有值。
出现错误时, 将返回 NULL。否则, 指向新列表的指针。
*/
list *listCreate(void)
{
struct list *list;
//zmalloc 可以理解为malloc,用于申请空间,
//redis对malloc做了封装,产生了zmalloc,具体信息在zmalloc.c和zmalloc.h中。
if ((list = zmalloc(sizeof(*list))) == NULL)
return NULL;//申请空间失败,则返回null
//初始化list
list->head = list->tail = NULL;
list->len = 0;
list->dup = NULL;
list->free = NULL;
list->match = NULL;
return list;
}
/* Remove all the elements from the list without destroying the list itself. */
/*删除所有元素,但不销毁list*/
void listEmpty(list *list)
{
unsigned long len;
listNode *current, *next;//当前节点和下一节点
current = list->head;//从头结点开始
len = list->len;
while(len--) {
next = current->next;
if (list->free) list->free(current->value);
zfree(current);//释放每一个节点
current = next;
}
list->head = list->tail = NULL;//设置头结点,尾节点为null
list->len = 0;//设置长度为0
}
/* Free the whole list.
* This function can't fail. */
/*释放整个列表,此操作不会失败*/
void listRelease(list *list)
{
listEmpty(list);//清空list
zfree(list);//释放list
}
/* 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. */
/*在list的头部插入一个新节点,参数value作为其中的值
成功返回list指针,失败返回null,且不执行任何操作*/
list *listAddNodeHead(list *list, void *value)
{
listNode *node;
//构造一个新节点,申请空间,设置值
if ((node = zmalloc(sizeof(*node))) == NULL)
return NULL;
node->value = value;
//把节点插入头部
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;
}
/* 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. */
/*在尾部插入,与在头部插入类似*/
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;
}
/*在指定位置插入
list:指定list;
value:新节点的值
old_node:插入在节点附近
after:为1时,插入到旧节点的后面,否则插入到旧节点的前面*/
list *listInsertNode(list *list, listNode *old_node, void *value, int after) {
listNode *node;
//构造一个新节点
if ((node = zmalloc(sizeof(*node))) == NULL)
return NULL;
node->value = value;
//插入节点
if (after) {
node->prev = old_node;
node->next = old_node->next;
if (list->tail == old_node) {
list->tail = node;
}
} else {
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. */
/*删除指定列表中的指定节点,并释放节点空间,此操作不会失败*/
void listDelNode(list *list, listNode *node)
{
if (node->prev)//前一个节点不是null
node->prev->next = node->next;
else//如果是,则当前节点为头结点
list->head = node->next;
if (node->next)
node->next->prev = node->prev;
else//尾节点
list->tail = node->prev;
if (list->free) list->free(node->value);//释放节点值的空间
zfree(node);//释放节点
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. */
/*
返回列表迭代器 "iter"。初始化后, 对 listNext () 的每次调用都将返回列表中的下一个元素。
此操作不会失败。*/
listIter *listGetIterator(list *list, int direction)
{
listIter *iter;
//申请空间失败
if ((iter = zmalloc(sizeof(*iter))) == NULL) return NULL;
//获取指定方向的下一个节点
if (direction == AL_START_HEAD)
iter->next = list->head;
else
iter->next = list->tail;
//设置指定方向
iter->direction = direction;
return iter;
}
/* Release the iterator memory */
/*释放迭代器*/
void listReleaseIterator(listIter *iter) {
zfree(iter);
}
/* Create an iterator in the list private iterator structure */
/*重置迭代器:从头开始*/
void listRewind(list *list, listIter *li) {
li->next = list->head;
li->direction = AL_START_HEAD;
}
/*重置迭代器:从尾开始*/
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));
* }
*
* */
/*
返回迭代器的下一个元素。
使用 listDelNode () 删除当前返回的元素是有效的, 但不能删除其他元素。
该函数返回指向列表的下一个元素的指针, 如果没有其他元素, 则返回 NULL。
经典的应用场景有:*/
listNode *listNext(listIter *iter)
{
listNode *current = iter->next;
//current是迭代器中的下一个元素,则返回的是迭代器的下一个元素的下一个元素
if (current != NULL) {
//根据迭代方向得到下一个元素
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. */
/*
复制整个列表。在内存不足时返回 null。
成功时, 将返回原始列表的副本。
使用 Listsetdupfal () 函数设置的 "Dup" 方法复制节点值。
否则, 原始节点的相同的指针值将被用作复制节点的值。原始列表永远不会被修改无论成功还是失败。*/
list *listDup(list *orig)
{
list *copy;
listIter iter;
listNode *node;
//生成一个list
if ((copy = listCreate()) == NULL)
return NULL;
//设置list信息
copy->dup = orig->dup;
copy->free = orig->free;
copy->match = orig->match;
listRewind(orig, &iter);
//遍历节点,复制
while((node = listNext(&iter)) != NULL) {
void *value;
//如果有dup函数
if (copy->dup) {
value = copy->dup(node->value);
//值为null,释放copyList
if (value == NULL) {
listRelease(copy);
return NULL;
}
} else
value = node->value;
//添加失败,释放copyList
if (listAddNodeTail(copy, value) == NULL) {
listRelease(copy);
return NULL;
}
}
//全部复制成功
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. */
/*
在列表中搜索与给定键匹配的节点。
匹配是使用 Listsetmatchmetf () 设置的 "匹配" 方法。
如果未设置 "匹配" 方法, 则拿每个节点的value和key比较(搜索从头部开始)。
成功时返回第一个匹配的节点指针。如果不存在匹配节点,返回 null。*/
listNode *listSearchKey(list *list, void *key)
{
listIter iter;
listNode *node;
//遍历全部节点
listRewind(list, &iter);
while((node = listNext(&iter)) != NULL) {
//有匹配函数
if (list->match) {
if (list->match(node->value, key)) {
return node;
}
} else {
//比较key和value
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. */
/*
返回指定的下标的元素:0是头节点, 1 是下一个节点, 依此类推。
负整数用于从尾部开始计数,-1 是尾节点,-2 倒数第二个节点, 依此类推。
如果索引超出范围, 则返回 NULL。*/
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. */
/*旋转列表, 把尾节点移到头部。*/
void listRotate(list *list) {
//得到尾节点
listNode *tail = list->tail;
if (listLength(list) <= 1) return;
/* Detach current tail */
//设置倒数第二个节点为尾节点
list->tail = tail->prev;
list->tail->next = NULL;
/* Move it as head */
//把尾节点设为头结点
list->head->prev = tail;
tail->prev = NULL;
tail->next = list->head;
list->head = tail;
}
/* Add all the elements of the list 'o' at the end of the
* list 'l'. The list 'other' remains empty but otherwise valid. */
/*把列表o的所有元素插入到列表l的尾部。列表o设为空, 但在其他方面有效。 */
void listJoin(list *l, list *o) {
if (o->head)
o->head->prev = l->tail;
if (l->tail)
l->tail->next = o->head;
else//l->tail为null,l列表为空
l->head = o->head;
if (o->tail) l->tail = o->tail;
l->len += o->len;
/* Setup other as an empty list. */
//把o设为空,其他的都不动
o->head = o->tail = NULL;
o->len = 0;
}
体会:这一部分比较简单,定义了adlist结构体和一些基本操作。跟链表差不多,不难,基本上看了就都能懂。
1.到处都是指针,很方便;
2.代码很干净,看了很舒服;
3.有很多注释;