【glibc】glib库单向链表GSList介绍

glib库单向链表介绍

glib库里实现了一些基本的数据结构，比如单向链表，双向链表、队列、树、hash表和数组。这篇文章里我主要介绍在linux平台下使用glib库中的单向链表进行编程，以后的文章我会陆续介绍双向链表、队列和其它数据结构的用法。

单向链表（即GSList）是glib库里最简单的容具，它把一系列的节点链接在一起，可以从一个节点访问到下一个节点。glib库里对GSList结构的定义如下：

struct  GSList
{
  gpointer data;
  GSList *next;
} ;

data成员定义为gpointer（即void*），可以放任何类型的数据。下面举个例子来说明怎么使用GSList来创建、添加、插入、排序、反转和销毁单向链表。

#include  < glib.h >

void  display_list(GSList  * list)
{
    GSList  * iterator  =  NULL;

     for  (iterator  =  list; iterator; iterator  =  iterator -> next) {
        printf( " %s  " , ( char * )iterator -> data);
    }
    printf( " /n " );
}

int  my_str_cmp(gconstpointer str1, gconstpointer str2)
{
     return  strcmp(str1, str2);
}

int  main( int  argc,  char   * argv[])
{
    GSList  * list  =  NULL;

     /*
     * 这里没有调用创建链表的函数，只需要声明一个指向GSList结构体的指针，
     * g_slist_append函数返回指向链表首部的指针，所以一定要保存这个指针
      */
    printf( " Creat single list:/n " );
    list  =  g_slist_append(list,  " one " );
    list  =  g_slist_append(list,  " two " );
    list  =  g_slist_append(list,  " three " );
    display_list(list);

     /*
     * 在链表首部加入，复杂度是O(1)，记得要保存函数返回的指针
      */
    printf( " Add at head of list:/n " );
    list  =  g_slist_prepend(list,  " first " );
    list  =  g_slist_prepend(list,  " second " );
    list  =  g_slist_prepend(list,  " third " );
    display_list(list);

     /*
     * 在链表的指定位置插入一个节点
      */
    printf( " Insert at index 1, 2, 3:/n " );
    list  =  g_slist_insert(list,  " 1 " ,  1 );
    list  =  g_slist_insert(list,  " 2 " ,  2 );
    list  =  g_slist_insert(list,  " 3 " ,  3 );
    display_list(list);

     /*
     * 向链表中插入节点并排序，这里我传入了一个用于排序链表元素的比较函数，
     * 这个函数只是简单的调用了strcmp。这里可以直接到strcmp作为第三个参数
     * 传给g_slist_insert_sorted
      */
    printf( " Insert sorted:/n " );
    list  =  g_slist_insert_sorted(list,  " ONE " , my_str_cmp);
    list  =  g_slist_insert_sorted(list,  " TWO " , my_str_cmp);
    list  =  g_slist_insert_sorted(list,  " THREE " , my_str_cmp);
    display_list(list);

     /*
     * 反转链表
      */
    printf( " Reverse the list:/n " );
    list  =  g_slist_reverse(list);
    display_list(list);

     /*
     * 删除链表，如果list为NULL的话，g_slist_free函数会直接返回
      */
    g_slist_free(list);
     return   0 ;
}

程序的运行结果如下：

Creat single list:
one two three
Add at head of list:
third second first one two three
Insert at index 1, 2, 3:
third 1 2 3 second first one two three
Insert sorted:
ONE THREE TWO third 1 2 3 second first one two three
Reverse the list:
three two one first second 3 2 1 third TWO THREE ONE

从上面的例子里我们可以看到，使用一个单向链表前只需要声明一个指向GSList结构的指针就可以了，声明该指 针以后就可以用该指针来对链表进行操作，只需要记住每次对链表进行操作后，都要保存返回的链表头指针就可以了。

下面的一个例子用于演法对单链表的查找、删除与合并。

#include  < glib.h >

void  display_list(GSList  * list)
{
    GSList  * iterator  =  NULL;

     for  (iterator  =  list; iterator; iterator  =  iterator -> next) {
        printf( " %s  " , ( char * ) iterator -> data);
    }
    printf( " /n " );
}

int  main( int  argc,  char   * argv[])
{
    GSList  * list  =  NULL;

    printf( " Create single list:/n " );
    list  =  g_slist_append(list,  " one " );
    list  =  g_slist_append(list,  " two " );
    list  =  g_slist_append(list,  " three " );
    list  =  g_slist_append(list,  " four " );
    list  =  g_slist_append(list,  " five " );
    display_list(list);

    GSList  * it  =  NULL;

     /*
     * 查找内容为"three"的节点，返回指向找到的第一个节点的指针
      */
    printf( " Find data "three" in the list:/n " );
    it  =  g_slist_find(list,  " three " );
    printf( " %s " , ( char * ) it -> data);

     /*
     * 查找第三个节点，链表里节点的索引号为0,1,2...
     * 如果超出链表尾部（链表长度小于3）返回NULL
      */
    printf( " Data of the 3rd item:/n " );
    it  =  g_slist_nth(list,  2 );
     if  (it  !=  NULL) {
        printf( " %s " , ( char * ) it -> data);
    }

     /*
     * 取第5个节点的数据，如果超出链表尾部，返回NULL
      */
    printf( " Data of the 5th item:/n " );
    printf( " %s " , g_slist_nth_data(list,  4 ));

    list  =  g_slist_append(list,  " two " );
    display_list(list);
    
     /*
     * 删除数据为"two"的节点，这里只会删除找到的第一个节点，
     * 后面的节点不会被删除
      */
    printf( " Remove the first data "two" from the list:/n " );
    list  =  g_slist_remove(list,  " two " );
    display_list(list);

     /*
     * 另一种删除节点的方法，先把节点从链表里删除，再删除节点的数据
      */
    printf( " Remove the 3rd item from list:/n " );
    it  =  g_slist_nth(list,  2 );

     /*  执行完下面这一步it->next==NULL  */
    list  =  g_slist_remove_link(list, it);
    
     /*  删除节点及其数据  */
    g_slist_free_1(it);
    display_list(list);

    GSList  * list2  =  NULL;
    
    printf( " The second list:/n " );
    list2  =  g_slist_append(list2,  " six " );
    list2  =  g_slist_append(list2,  " seven " );
    list2  =  g_slist_append(list2,  " eight " );
    display_list(list2);

     /*
     * 合并两个链表
      */
    printf( " Concat two lists:/n " );
    list  =  g_slist_concat(list, list2);
    display_list(list);

    g_slist_free(list);
     return   0 ;
}

程序的运行结果如下：

Creat single list:
one two three
Add at head of list:
third second first one two three
Insert at index 1, 2, 3:
third 1 2 3 second first one two three
Insert sorted:
ONE THREE TWO third 1 2 3 second first one two three
Reverse the list:
three two one first second 3 2 1 third TWO THREE ONE

从上面的例子里我们可以看到，使用一个单向链表前只需要声明一个指向GSList结构的指针就可以了，声明该指 针以后就可以用该指针来对链表进行操作，只需要记住每次对链表进行操作后，都要保存返回的链表头指针就可以了。

下面的一个例子用于演法对单链表的查找、删除与合并。

#include  < glib.h >

void  display_list(GSList  * list)
{
    GSList  * iterator  =  NULL;

     for  (iterator  =  list; iterator; iterator  =  iterator -> next) {
        printf( " %s  " , ( char * ) iterator -> data);
    }
    printf( " /n " );
}

int  main( int  argc,  char   * argv[])
{
    GSList  * list  =  NULL;

    printf( " Create single list:/n " );
    list  =  g_slist_append(list,  " one " );
    list  =  g_slist_append(list,  " two " );
    list  =  g_slist_append(list,  " three " );
    list  =  g_slist_append(list,  " four " );
    list  =  g_slist_append(list,  " five " );
    display_list(list);

    GSList  * it  =  NULL;

     /*
     * 查找内容为"three"的节点，返回指向找到的第一个节点的指针
      */
    printf( " Find data "three" in the list:/n " );
    it  =  g_slist_find(list,  " three " );
    printf( " %s " , ( char * ) it -> data);

     /*
     * 查找第三个节点，链表里节点的索引号为0,1,2...
     * 如果超出链表尾部（链表长度小于3）返回NULL
      */
    printf( " Data of the 3rd item:/n " );
    it  =  g_slist_nth(list,  2 );
     if  (it  !=  NULL) {
        printf( " %s " , ( char * ) it -> data);
    }

     /*
     * 取第5个节点的数据，如果超出链表尾部，返回NULL
      */
    printf( " Data of the 5th item:/n " );
    printf( " %s " , g_slist_nth_data(list,  4 ));

    list  =  g_slist_append(list,  " two " );
    display_list(list);
    
     /*
     * 删除数据为"two"的节点，这里只会删除找到的第一个节点，
     * 后面的节点不会被删除
      */
    printf( " Remove the first data "two" from the list:/n " );
    list  =  g_slist_remove(list,  " two " );
    display_list(list);

     /*
     * 另一种删除节点的方法，先把节点从链表里删除，再删除节点的数据
      */
    printf( " Remove the 3rd item from list:/n " );
    it  =  g_slist_nth(list,  2 );

     /*  执行完下面这一步it->next==NULL  */
    list  =  g_slist_remove_link(list, it);
    
     /*  删除节点及其数据  */
    g_slist_free_1(it);
    display_list(list);

    GSList  * list2  =  NULL;
    
    printf( " The second list:/n " );
    list2  =  g_slist_append(list2,  " six " );
    list2  =  g_slist_append(list2,  " seven " );
    list2  =  g_slist_append(list2,  " eight " );
    display_list(list2);

     /*
     * 合并两个链表
      */
    printf( " Concat two lists:/n " );
    list  =  g_slist_concat(list, list2);
    display_list(list);

    g_slist_free(list);
     return   0 ;
}

程序的运行结果如下：

Create single list:
one two three four five
Find data "three" in the list:
three
Data of the 3rd item:
three
Data of the 5th item:
five
one two three four five two
Remove the first data "two" from the list:
one three four five two
Remove the 3rd item from list:
one three five two
The second list:
six seven eight
Concat two lists:
one three five two six seven eight

通过上面的两个子例我们可以看到，glib库中的单链表操作是很简单的。在这么多函数调用里，我们还可以发现glib库中操作数据结构的函数命名规则：g_容器名_函数名。对于我后面的文章将要讲到的双向链表、队列、树、hash表和数组，这一命名规则同样适用。

glib库的更多参考：
http://developer.gnome.org/doc/API/glib/index.html
http://developer.gnome.org/doc/API/2.0/glib/index.html