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adlist.c
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/* 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. */
// 初始化一个空的list结构体
list *listCreate(void)
{
struct list *list;
if ((list = zmalloc(sizeof(*list))) == NULL)
return NULL;
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. */
// 释放list中的所有元素,但保留list本身
void listEmpty(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);
zfree(current);
current = next;
}
list->head = list->tail = NULL;
list->len = 0;
}
/* Free the whole list.
*
* This function can't fail. */
// 释放list中的元素,并释放list本身
void listRelease(list *list)
{
listEmpty(list);
zfree(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. */
// 从list的头部添加新的节点
list *listAddNodeHead(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 = 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list的尾部添加新的节点
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;
}
// 如果after !=0,则在old_node之后添加新的节点;否则在old_node前面添加新的节点
list *listInsertNode(list *list, listNode *old_node, void *value, int after) {
listNode *node;
if ((node = zmalloc(sizeof(*node))) == NULL)
return NULL;
node->value = value;
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. */
// 删除执行的node节点
void 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. */
// 获取迭代器,作为listNext()函数的入参,通过listNext()可以获取下一个节点。迭代顺序按照direction的值,可以选择从链首或链尾开始迭代
listIter *listGetIterator(list *list, int direction)
{
listIter *iter;
if ((iter = zmalloc(sizeof(*iter))) == NULL) return NULL;
// 如果选择从链首开始迭代,则迭代器执向的下一个节点为链首
if (direction == AL_START_HEAD)
iter->next = list->head;
else
iter->next = list->tail;
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 */
// 复用一个迭代器,从list的链首开始迭代
void listRewind(list *list, listIter *li) {
li->next = list->head;
li->direction = AL_START_HEAD;
}
// 复用一个迭代器,从list的链尾开始迭代
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));
* }
*
* */
// 参见注释中的例子,用于每迭代一次获取一个节点
listNode *listNext(listIter *iter)
{
listNode *current = iter->next;
if (current != NULL) {
// 如果从链首开始迭代,则使用next节点进行迭代
if (iter->direction == AL_START_HEAD)
iter->next = current->next;
// 如果从链尾巴开始迭代,则使用prev节点进行迭代se
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. */
// 从list orig复制一个新的list。如果实现了orig->dup函数,则复制的list中会也会复制一份node的value,否则复制的node会指向原始node中的value的地址
list *listDup(list *orig)
{
list *copy;
listIter iter;
listNode *node;
if ((copy = listCreate()) == NULL)
return NULL;
copy->dup = orig->dup;
copy->free = orig->free;
copy->match = orig->match;
listRewind(orig, &iter);
while((node = listNext(&iter)) != NULL) {
void *value;
if (copy->dup) {
value = copy->dup(node->value);
if (value == NULL) {
listRelease(copy);
return NULL;
}
} else
value = node->value;
if (listAddNodeTail(copy, value) == NULL) {
listRelease(copy);
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. */
// 使用key在list中查找并返回符合要求的node。如果实现了list->match接口,则采用该接口进行比较;否则返回的node的value等于key
listNode *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)) {
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list上的第index个节点。如果index为负数,则从链尾开始遍历查找;否则从链首开始遍历查找 index为-1表示链尾,为1表示链首。
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tail节点插入到head前面,并更新head指针,移除tail指针
void listRotateTailToHead(list *list) {
if (listLength(list) <= 1) return;
/* Detach current tail */
listNode *tail = list->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;
}
/* Rotate the list removing the head node and inserting it to the tail. */
void listRotateHeadToTail(list *list) {
if (listLength(list) <= 1) return;
listNode *head = list->head;
/* Detach current head */
list->head = head->next;
list->head->prev = NULL;
/* Move it as tail */
list->tail->next = head;
head->next = NULL;
head->prev = list->tail;
list->tail = head;
}
/* Add all the elements of the list 'o' at the end of the
* list 'l'. The list 'other' remains empty but otherwise valid. */
// 将list o中的元素添加到list l之后
void listJoin(list *l, list *o) {
if (o->head)
o->head->prev = l->tail;
if (l->tail)
l->tail->next = o->head;
else
l->head = o->head;
if (o->tail) l->tail = o->tail;
l->len += o->len;
/* Setup other as an empty list. */
o->head = o->tail = NULL;
o->len = 0;
}