• 数据结构开发(11):双向循环链表的实现


    0.目录

    1.双向循环链表的实现

    2.小结

    1.双向循环链表的实现

    本节目标:

    • 使用 Linux 内核链表实现 StLib 中的双向循环链表
    • template <typename T> class DualCircleList;

    StLib 中双向循环链表的设计思路:

    • 数据结点之间在逻辑上构成双向循环链表,头结点仅用于结点的定位。

    实现思路:

    • 通过模板定义 DualCircleList 类,继承自 DualLinkList
    • 在 DualCircleList 内部使用Linux内核链表进行实现
    • 使用 struct list_head 定义 DualCircleList 的头结点
    • 特殊处理:循环遍历时忽略头结点

    实现要点:

    • 通过 list_head 进行目标结点定位( position(i) )
    • 通过 list_entry 将 list_head 指针转换为目标结点指针
    • 通过 list_for_each 实现 int find(const T& e) 函数
    • 遍历函数中的 next()pre() 需要考虑跳过头结点

    双向循环链表的实现(DualLinkList.h):
    使用到的LinuxList.h头文件放在文字尾部:LinuxList.h
    DualLinkList.h

    #ifndef DUALCIRCLELIST_H
    #define DUALCIRCLELIST_H
    
    #include "LinuxList.h"
    #include "DualLinkList.h"
    
    namespace StLib
    {
    
    template <typename T>
    class DualCircleList : public DualLinkList<T>
    {
    protected:
        struct Node : public Object
        {
            list_head head;
            T value;
        };
    
        list_head m_header;
        list_head* m_current;
    
        list_head* position(int i) const
        {
            list_head* ret = const_cast<list_head*>(&m_header);
    
            for(int p=0; p<i; p++)
            {
                ret = ret->next;
            }
    
            return ret;
        }
    
        int mod(int i) const
        {
            return (this->m_length == 0) ? 0 : (i % this->m_length);
        }
    public:
        DualCircleList()
        {
            this->m_length = 0;
            this->m_step = 1;
    
            m_current = NULL;
    
            INIT_LIST_HEAD(&m_header);
        }
    
        bool insert(const T& e)
        {
            return insert(this->m_length, e);
        }
    
        bool insert(int i, const T& e)
        {
            bool ret = true;
            Node* node = new Node();
    
            i = i % (this->m_length + 1);
    
            if( node != NULL )
            {
                node->value = e;
    
                list_add_tail(&node->head, position(i)->next);
    
                this->m_length++;
            }
            else
            {
                THROW_EXCEPTION(NoEnoughMemoryException, "No memory to insert new element ...");
            }
    
            return ret;
        }
    
        bool remove(int i)
        {
            bool ret = true;
    
            i = mod(i);
    
            ret = ((0 <= i) && (i < this->m_length));
    
            if( ret )
            {
                list_head* toDel = position(i)->next;
    
                if( m_current == toDel )
                {
                    m_current = toDel->next;
                }
    
                list_del(toDel);
    
                this->m_length--;
    
                delete list_entry(toDel, Node, head);
            }
    
            return ret;
        }
    
        bool set(int i, const T& e)
        {
            bool ret = true;
    
            i = mod(i);
    
            ret = ((0 <= i) && (i < this->m_length));
    
            if( ret )
            {
                list_entry(position(i)->next, Node, head)->value = e;
            }
    
            return ret;
        }
    
        T get(int i) const
        {
            T ret;
    
            if( get(i, ret) )
            {
                return ret;
            }
            else
            {
                THROW_EXCEPTION(IndexOutOfBoundsException, "Invalid parameter i to get element ...");
            }
    
            return ret;
        }
    
        bool get(int i, T& e) const
        {
            bool ret = true;
    
            i = mod(i);
    
            ret = ((0 <= i) && (i < this->m_length));
    
            if( ret )
            {
                e = list_entry(position(i)->next, Node, head)->value;
            }
    
            return ret;
        }
    
        int find(const T& e) const
        {
            int ret = -1;
            int i = 0;
            list_head* slider = NULL;
    
            list_for_each(slider, &m_header)
            {
                if( list_entry(slider, Node, head)->value == e )
                {
                    ret = i;
                    break;
                }
    
                i++;
            }
    
            return ret;
        }
    
        int length() const
        {
            return this->m_length;
        }
    
        void clear()
        {
            while( this->m_length > 0 )
            {
                remove(0);
            }
        }
    
        bool move(int i, int step = 1)
        {
            bool ret = (step > 0);
    
            i = mod(i);
    
            ret = ret && ((0 <= i) && (i < this->m_length));
    
            if( ret )
            {
                m_current = position(i)->next;
    
                this->m_step = step;
            }
    
            return ret;
        }
    
        bool end()
        {
            return (m_current == NULL) || (this->m_length == 0);
        }
    
        virtual T current()
        {
            if( !end() )
            {
                return list_entry(m_current, Node, head)->value;
            }
            else
            {
                THROW_EXCEPTION(InvalidOperationException, "No value at current position ...");
            }
        }
    
        bool next()
        {
            int i = 0;
    
            while( (i < this->m_step) && !end() )
            {
                if( m_current != &m_header )
                {
                    m_current = m_current->next;
                    i++;
                }
                else
                {
                    m_current = m_current->next;
                }
            }
    
            if( m_current == &m_header )
            {
                m_current = m_current->next;
            }
    
            return (i == this->m_step);
        }
    
        bool pre()
        {
            int i = 0;
    
            while( (i < this->m_step) && !end() )
            {
                if( m_current != &m_header )
                {
                    m_current = m_current->prev;
                    i++;
                }
                else
                {
                    m_current = m_current->prev;
                }
            }
    
            if( m_current == &m_header )
            {
                m_current = m_current->prev;
            }
    
            return (i == this->m_step);
        }
    
        ~DualCircleList()
        {
            clear();
        }
    };
    
    }
    
    #endif // DUALCIRCLELIST_H
    

    main.cpp测试

    #include <iostream>
    #include "DualCircleList.h"
    
    using namespace std;
    using namespace StLib;
    
    int main()
    {
        DualCircleList<int> d1;
    
        for(int i=0; i<5; i++)
        {
            d1.insert(0, i);
            d1.insert(0, 5);
        }
    
        cout << "begin" << endl;
    
        d1.move(d1.length()-1);
    
        while( d1.find(5) != -1 )
        {
            if( d1.current() == 5 )
            {
                cout << d1.current() << endl;
    
                d1.remove(d1.find(d1.current()));
            }
            else
            {
                d1.pre();
            }
        }
    
        cout << "end" << endl;
    
    //    for(int i=0; i<d1.length(); i++)
    //    {
    //        cout << d1.get(i) << endl;
    //    }
        for(int i=0; i<10; i++)
        {
            cout << d1.get(i) << endl;
        }
    
        return 0;
    }
    

    运行结果为:

    begin
    5
    5
    5
    5
    5
    end
    4
    3
    2
    1
    0
    4
    3
    2
    1
    0
    

    思考题——下面代码中的 pn1 和 pn2 是否相等?为什么?

    2.小结

    • Linux内核链表是带头结点的双向循环链表
    • DualCircleList 使用Linux内核链表进行内部实现
    • DualCircleList 在循环遍历时需要跳过头结点
    • list_head 指针转换为目标结点指针时,使用 list_entry 宏

    LinuxList.h
    需要将LinuxList.h中的new改成node。

    #ifndef _LINUX_LIST_H
    #define _LINUX_LIST_H
    
    // #include <linux/types.h>
    // #include <linux/stddef.h>
    // #include <linux/poison.h>
    // #include <linux/prefetch.h>
    
    #ifndef offsetof
    #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
    #endif
    
    #ifndef container_of
    #define container_of(ptr, type, member) ((type *)((char *)ptr - offsetof(type,member)))
    #endif
    
    #define prefetch(x) ((void)x)
    
    #define LIST_POISON1  (NULL)
    #define LIST_POISON2  (NULL)
    
    struct list_head {
        struct list_head *next, *prev;
    };
    
    struct hlist_head {
        struct hlist_node *first;
    };
    
    struct hlist_node {
        struct hlist_node *next, **pprev;
    };
    
    /*
     * Simple doubly linked list implementation.
     *
     * Some of the internal functions ("__xxx") are useful when
     * manipulating whole lists rather than single entries, as
     * sometimes we already know the next/prev entries and we can
     * generate better code by using them directly rather than
     * using the generic single-entry routines.
     */
    
    #define LIST_HEAD_INIT(name) { &(name), &(name) }
    
    #define LIST_HEAD(name) 
        struct list_head name = LIST_HEAD_INIT(name)
    
    static void INIT_LIST_HEAD(struct list_head *list)
    {
        list->next = list;
        list->prev = list;
    }
    
    /*
     * Insert a new entry between two known consecutive entries.
     *
     * This is only for internal list manipulation where we know
     * the prev/next entries already!
     */
    #ifndef CONFIG_DEBUG_LIST
    static void __list_add(struct list_head *node,
                      struct list_head *prev,
                      struct list_head *next)
    {
        next->prev = node;
        node->next = next;
        node->prev = prev;
        prev->next = node;
    }
    #else
    extern void __list_add(struct list_head *node,
                      struct list_head *prev,
                      struct list_head *next);
    #endif
    
    /**
     * list_add - add a new entry
     * @new: new entry to be added
     * @head: list head to add it after
     *
     * Insert a new entry after the specified head.
     * This is good for implementing stacks.
     */
    static void list_add(struct list_head *node, struct list_head *head)
    {
        __list_add(node, head, head->next);
    }
    
    
    /**
     * list_add_tail - add a new entry
     * @new: new entry to be added
     * @head: list head to add it before
     *
     * Insert a new entry before the specified head.
     * This is useful for implementing queues.
     */
    static void list_add_tail(struct list_head *node, struct list_head *head)
    {
        __list_add(node, head->prev, head);
    }
    
    /*
     * Delete a list entry by making the prev/next entries
     * point to each other.
     *
     * This is only for internal list manipulation where we know
     * the prev/next entries already!
     */
    static void __list_del(struct list_head * prev, struct list_head * next)
    {
        next->prev = prev;
        prev->next = next;
    }
    
    /**
     * list_del - deletes entry from list.
     * @entry: the element to delete from the list.
     * Note: list_empty() on entry does not return true after this, the entry is
     * in an undefined state.
     */
    #ifndef CONFIG_DEBUG_LIST
    static void __list_del_entry(struct list_head *entry)
    {
        __list_del(entry->prev, entry->next);
    }
    
    static void list_del(struct list_head *entry)
    {
        __list_del(entry->prev, entry->next);
        entry->next = LIST_POISON1;
        entry->prev = LIST_POISON2;
    }
    #else
    extern void __list_del_entry(struct list_head *entry);
    extern void list_del(struct list_head *entry);
    #endif
    
    /**
     * list_replace - replace old entry by new one
     * @old : the element to be replaced
     * @new : the new element to insert
     *
     * If @old was empty, it will be overwritten.
     */
    static void list_replace(struct list_head *old,
                    struct list_head *node)
    {
        node->next = old->next;
        node->next->prev = node;
        node->prev = old->prev;
        node->prev->next = node;
    }
    
    static void list_replace_init(struct list_head *old,
                        struct list_head *node)
    {
        list_replace(old, node);
        INIT_LIST_HEAD(old);
    }
    
    /**
     * list_del_init - deletes entry from list and reinitialize it.
     * @entry: the element to delete from the list.
     */
    static void list_del_init(struct list_head *entry)
    {
        __list_del_entry(entry);
        INIT_LIST_HEAD(entry);
    }
    
    /**
     * list_move - delete from one list and add as another's head
     * @list: the entry to move
     * @head: the head that will precede our entry
     */
    static void list_move(struct list_head *list, struct list_head *head)
    {
        __list_del_entry(list);
        list_add(list, head);
    }
    
    /**
     * list_move_tail - delete from one list and add as another's tail
     * @list: the entry to move
     * @head: the head that will follow our entry
     */
    static void list_move_tail(struct list_head *list,
                      struct list_head *head)
    {
        __list_del_entry(list);
        list_add_tail(list, head);
    }
    
    /**
     * list_is_last - tests whether @list is the last entry in list @head
     * @list: the entry to test
     * @head: the head of the list
     */
    static int list_is_last(const struct list_head *list,
                    const struct list_head *head)
    {
        return list->next == head;
    }
    
    /**
     * list_empty - tests whether a list is empty
     * @head: the list to test.
     */
    static int list_empty(const struct list_head *head)
    {
        return head->next == head;
    }
    
    /**
     * list_empty_careful - tests whether a list is empty and not being modified
     * @head: the list to test
     *
     * Description:
     * tests whether a list is empty _and_ checks that no other CPU might be
     * in the process of modifying either member (next or prev)
     *
     * NOTE: using list_empty_careful() without synchronization
     * can only be safe if the only activity that can happen
     * to the list entry is list_del_init(). Eg. it cannot be used
     * if another CPU could re-list_add() it.
     */
    static int list_empty_careful(const struct list_head *head)
    {
        struct list_head *next = head->next;
        return (next == head) && (next == head->prev);
    }
    
    /**
     * list_rotate_left - rotate the list to the left
     * @head: the head of the list
     */
    static void list_rotate_left(struct list_head *head)
    {
        struct list_head *first;
    
        if (!list_empty(head)) {
            first = head->next;
            list_move_tail(first, head);
        }
    }
    
    /**
     * list_is_singular - tests whether a list has just one entry.
     * @head: the list to test.
     */
    static int list_is_singular(const struct list_head *head)
    {
        return !list_empty(head) && (head->next == head->prev);
    }
    
    static void __list_cut_position(struct list_head *list,
            struct list_head *head, struct list_head *entry)
    {
        struct list_head *new_first = entry->next;
        list->next = head->next;
        list->next->prev = list;
        list->prev = entry;
        entry->next = list;
        head->next = new_first;
        new_first->prev = head;
    }
    
    /**
     * list_cut_position - cut a list into two
     * @list: a new list to add all removed entries
     * @head: a list with entries
     * @entry: an entry within head, could be the head itself
     *	and if so we won't cut the list
     *
     * This helper moves the initial part of @head, up to and
     * including @entry, from @head to @list. You should
     * pass on @entry an element you know is on @head. @list
     * should be an empty list or a list you do not care about
     * losing its data.
     *
     */
    static void list_cut_position(struct list_head *list,
            struct list_head *head, struct list_head *entry)
    {
        if (list_empty(head))
            return;
        if (list_is_singular(head) &&
            (head->next != entry && head != entry))
            return;
        if (entry == head)
            INIT_LIST_HEAD(list);
        else
            __list_cut_position(list, head, entry);
    }
    
    static void __list_splice(const struct list_head *list,
                     struct list_head *prev,
                     struct list_head *next)
    {
        struct list_head *first = list->next;
        struct list_head *last = list->prev;
    
        first->prev = prev;
        prev->next = first;
    
        last->next = next;
        next->prev = last;
    }
    
    /**
     * list_splice - join two lists, this is designed for stacks
     * @list: the new list to add.
     * @head: the place to add it in the first list.
     */
    static void list_splice(const struct list_head *list,
                    struct list_head *head)
    {
        if (!list_empty(list))
            __list_splice(list, head, head->next);
    }
    
    /**
     * list_splice_tail - join two lists, each list being a queue
     * @list: the new list to add.
     * @head: the place to add it in the first list.
     */
    static void list_splice_tail(struct list_head *list,
                    struct list_head *head)
    {
        if (!list_empty(list))
            __list_splice(list, head->prev, head);
    }
    
    /**
     * list_splice_init - join two lists and reinitialise the emptied list.
     * @list: the new list to add.
     * @head: the place to add it in the first list.
     *
     * The list at @list is reinitialised
     */
    static void list_splice_init(struct list_head *list,
                        struct list_head *head)
    {
        if (!list_empty(list)) {
            __list_splice(list, head, head->next);
            INIT_LIST_HEAD(list);
        }
    }
    
    /**
     * list_splice_tail_init - join two lists and reinitialise the emptied list
     * @list: the new list to add.
     * @head: the place to add it in the first list.
     *
     * Each of the lists is a queue.
     * The list at @list is reinitialised
     */
    static void list_splice_tail_init(struct list_head *list,
                         struct list_head *head)
    {
        if (!list_empty(list)) {
            __list_splice(list, head->prev, head);
            INIT_LIST_HEAD(list);
        }
    }
    
    /**
     * list_entry - get the struct for this entry
     * @ptr:	the &struct list_head pointer.
     * @type:	the type of the struct this is embedded in.
     * @member:	the name of the list_struct within the struct.
     */
    #define list_entry(ptr, type, member) 
        container_of(ptr, type, member)
    
    /**
     * list_first_entry - get the first element from a list
     * @ptr:	the list head to take the element from.
     * @type:	the type of the struct this is embedded in.
     * @member:	the name of the list_struct within the struct.
     *
     * Note, that list is expected to be not empty.
     */
    #define list_first_entry(ptr, type, member) 
        list_entry((ptr)->next, type, member)
    
    /**
     * list_for_each	-	iterate over a list
     * @pos:	the &struct list_head to use as a loop cursor.
     * @head:	the head for your list.
     */
    #define list_for_each(pos, head) 
        for (pos = (head)->next; prefetch(pos->next), pos != (head); 
                pos = pos->next)
    
    /**
     * __list_for_each	-	iterate over a list
     * @pos:	the &struct list_head to use as a loop cursor.
     * @head:	the head for your list.
     *
     * This variant differs from list_for_each() in that it's the
     * simplest possible list iteration code, no prefetching is done.
     * Use this for code that knows the list to be very short (empty
     * or 1 entry) most of the time.
     */
    #define __list_for_each(pos, head) 
        for (pos = (head)->next; pos != (head); pos = pos->next)
    
    /**
     * list_for_each_prev	-	iterate over a list backwards
     * @pos:	the &struct list_head to use as a loop cursor.
     * @head:	the head for your list.
     */
    #define list_for_each_prev(pos, head) 
        for (pos = (head)->prev; prefetch(pos->prev), pos != (head); 
                pos = pos->prev)
    
    /**
     * list_for_each_safe - iterate over a list safe against removal of list entry
     * @pos:	the &struct list_head to use as a loop cursor.
     * @n:		another &struct list_head to use as temporary storage
     * @head:	the head for your list.
     */
    #define list_for_each_safe(pos, n, head) 
        for (pos = (head)->next, n = pos->next; pos != (head); 
            pos = n, n = pos->next)
    
    /**
     * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
     * @pos:	the &struct list_head to use as a loop cursor.
     * @n:		another &struct list_head to use as temporary storage
     * @head:	the head for your list.
     */
    #define list_for_each_prev_safe(pos, n, head) 
        for (pos = (head)->prev, n = pos->prev; 
             prefetch(pos->prev), pos != (head); 
             pos = n, n = pos->prev)
    
    /**
     * list_for_each_entry	-	iterate over list of given type
     * @pos:	the type * to use as a loop cursor.
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     */
    #define list_for_each_entry(pos, head, member)				
        for (pos = list_entry((head)->next, typeof(*pos), member);	
             prefetch(pos->member.next), &pos->member != (head); 	
             pos = list_entry(pos->member.next, typeof(*pos), member))
    
    /**
     * list_for_each_entry_reverse - iterate backwards over list of given type.
     * @pos:	the type * to use as a loop cursor.
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     */
    #define list_for_each_entry_reverse(pos, head, member)			
        for (pos = list_entry((head)->prev, typeof(*pos), member);	
             prefetch(pos->member.prev), &pos->member != (head); 	
             pos = list_entry(pos->member.prev, typeof(*pos), member))
    
    /**
     * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
     * @pos:	the type * to use as a start point
     * @head:	the head of the list
     * @member:	the name of the list_struct within the struct.
     *
     * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
     */
    #define list_prepare_entry(pos, head, member) 
        ((pos) ? : list_entry(head, typeof(*pos), member))
    
    /**
     * list_for_each_entry_continue - continue iteration over list of given type
     * @pos:	the type * to use as a loop cursor.
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     *
     * Continue to iterate over list of given type, continuing after
     * the current position.
     */
    #define list_for_each_entry_continue(pos, head, member) 		
        for (pos = list_entry(pos->member.next, typeof(*pos), member);	
             prefetch(pos->member.next), &pos->member != (head);	
             pos = list_entry(pos->member.next, typeof(*pos), member))
    
    /**
     * list_for_each_entry_continue_reverse - iterate backwards from the given point
     * @pos:	the type * to use as a loop cursor.
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     *
     * Start to iterate over list of given type backwards, continuing after
     * the current position.
     */
    #define list_for_each_entry_continue_reverse(pos, head, member)		
        for (pos = list_entry(pos->member.prev, typeof(*pos), member);	
             prefetch(pos->member.prev), &pos->member != (head);	
             pos = list_entry(pos->member.prev, typeof(*pos), member))
    
    /**
     * list_for_each_entry_from - iterate over list of given type from the current point
     * @pos:	the type * to use as a loop cursor.
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     *
     * Iterate over list of given type, continuing from current position.
     */
    #define list_for_each_entry_from(pos, head, member) 			
        for (; prefetch(pos->member.next), &pos->member != (head);	
             pos = list_entry(pos->member.next, typeof(*pos), member))
    
    /**
     * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
     * @pos:	the type * to use as a loop cursor.
     * @n:		another type * to use as temporary storage
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     */
    #define list_for_each_entry_safe(pos, n, head, member)			
        for (pos = list_entry((head)->next, typeof(*pos), member),	
            n = list_entry(pos->member.next, typeof(*pos), member);	
             &pos->member != (head); 					
             pos = n, n = list_entry(n->member.next, typeof(*n), member))
    
    /**
     * list_for_each_entry_safe_continue - continue list iteration safe against removal
     * @pos:	the type * to use as a loop cursor.
     * @n:		another type * to use as temporary storage
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     *
     * Iterate over list of given type, continuing after current point,
     * safe against removal of list entry.
     */
    #define list_for_each_entry_safe_continue(pos, n, head, member) 		
        for (pos = list_entry(pos->member.next, typeof(*pos), member), 		
            n = list_entry(pos->member.next, typeof(*pos), member);		
             &pos->member != (head);						
             pos = n, n = list_entry(n->member.next, typeof(*n), member))
    
    /**
     * list_for_each_entry_safe_from - iterate over list from current point safe against removal
     * @pos:	the type * to use as a loop cursor.
     * @n:		another type * to use as temporary storage
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     *
     * Iterate over list of given type from current point, safe against
     * removal of list entry.
     */
    #define list_for_each_entry_safe_from(pos, n, head, member) 			
        for (n = list_entry(pos->member.next, typeof(*pos), member);		
             &pos->member != (head);						
             pos = n, n = list_entry(n->member.next, typeof(*n), member))
    
    /**
     * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
     * @pos:	the type * to use as a loop cursor.
     * @n:		another type * to use as temporary storage
     * @head:	the head for your list.
     * @member:	the name of the list_struct within the struct.
     *
     * Iterate backwards over list of given type, safe against removal
     * of list entry.
     */
    #define list_for_each_entry_safe_reverse(pos, n, head, member)		
        for (pos = list_entry((head)->prev, typeof(*pos), member),	
            n = list_entry(pos->member.prev, typeof(*pos), member);	
             &pos->member != (head); 					
             pos = n, n = list_entry(n->member.prev, typeof(*n), member))
    
    /**
     * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
     * @pos:	the loop cursor used in the list_for_each_entry_safe loop
     * @n:		temporary storage used in list_for_each_entry_safe
     * @member:	the name of the list_struct within the struct.
     *
     * list_safe_reset_next is not safe to use in general if the list may be
     * modified concurrently (eg. the lock is dropped in the loop body). An
     * exception to this is if the cursor element (pos) is pinned in the list,
     * and list_safe_reset_next is called after re-taking the lock and before
     * completing the current iteration of the loop body.
     */
    #define list_safe_reset_next(pos, n, member)				
        n = list_entry(pos->member.next, typeof(*pos), member)
    
    /*
     * Double linked lists with a single pointer list head.
     * Mostly useful for hash tables where the two pointer list head is
     * too wasteful.
     * You lose the ability to access the tail in O(1).
     */
    
    #define HLIST_HEAD_INIT { .first = NULL }
    #define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
    #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
    static void INIT_HLIST_NODE(struct hlist_node *h)
    {
        h->next = NULL;
        h->pprev = NULL;
    }
    
    static int hlist_unhashed(const struct hlist_node *h)
    {
        return !h->pprev;
    }
    
    static int hlist_empty(const struct hlist_head *h)
    {
        return !h->first;
    }
    
    static void __hlist_del(struct hlist_node *n)
    {
        struct hlist_node *next = n->next;
        struct hlist_node **pprev = n->pprev;
        *pprev = next;
        if (next)
            next->pprev = pprev;
    }
    
    static void hlist_del(struct hlist_node *n)
    {
        __hlist_del(n);
        n->next = LIST_POISON1;
        n->pprev = LIST_POISON2;
    }
    
    static void hlist_del_init(struct hlist_node *n)
    {
        if (!hlist_unhashed(n)) {
            __hlist_del(n);
            INIT_HLIST_NODE(n);
        }
    }
    
    static void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
    {
        struct hlist_node *first = h->first;
        n->next = first;
        if (first)
            first->pprev = &n->next;
        h->first = n;
        n->pprev = &h->first;
    }
    
    /* next must be != NULL */
    static void hlist_add_before(struct hlist_node *n,
                        struct hlist_node *next)
    {
        n->pprev = next->pprev;
        n->next = next;
        next->pprev = &n->next;
        *(n->pprev) = n;
    }
    
    static void hlist_add_after(struct hlist_node *n,
                        struct hlist_node *next)
    {
        next->next = n->next;
        n->next = next;
        next->pprev = &n->next;
    
        if(next->next)
            next->next->pprev  = &next->next;
    }
    
    /* after that we'll appear to be on some hlist and hlist_del will work */
    static void hlist_add_fake(struct hlist_node *n)
    {
        n->pprev = &n->next;
    }
    
    /*
     * Move a list from one list head to another. Fixup the pprev
     * reference of the first entry if it exists.
     */
    static void hlist_move_list(struct hlist_head *old,
                       struct hlist_head *node)
    {
        node->first = old->first;
        if (node->first)
            node->first->pprev = &node->first;
        old->first = NULL;
    }
    
    #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
    
    #define hlist_for_each(pos, head) 
        for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); 
             pos = pos->next)
    
    #define hlist_for_each_safe(pos, n, head) 
        for (pos = (head)->first; pos && ({ n = pos->next; 1; }); 
             pos = n)
    
    /**
     * hlist_for_each_entry	- iterate over list of given type
     * @tpos:	the type * to use as a loop cursor.
     * @pos:	the &struct hlist_node to use as a loop cursor.
     * @head:	the head for your list.
     * @member:	the name of the hlist_node within the struct.
     */
    #define hlist_for_each_entry(tpos, pos, head, member)			 
        for (pos = (head)->first;					 
             pos && ({ prefetch(pos->next); 1;}) &&			 
            ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); 
             pos = pos->next)
    
    /**
     * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
     * @tpos:	the type * to use as a loop cursor.
     * @pos:	the &struct hlist_node to use as a loop cursor.
     * @member:	the name of the hlist_node within the struct.
     */
    #define hlist_for_each_entry_continue(tpos, pos, member)		 
        for (pos = (pos)->next;						 
             pos && ({ prefetch(pos->next); 1;}) &&			 
            ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); 
             pos = pos->next)
    
    /**
     * hlist_for_each_entry_from - iterate over a hlist continuing from current point
     * @tpos:	the type * to use as a loop cursor.
     * @pos:	the &struct hlist_node to use as a loop cursor.
     * @member:	the name of the hlist_node within the struct.
     */
    #define hlist_for_each_entry_from(tpos, pos, member)			 
        for (; pos && ({ prefetch(pos->next); 1;}) &&			 
            ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); 
             pos = pos->next)
    
    /**
     * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
     * @tpos:	the type * to use as a loop cursor.
     * @pos:	the &struct hlist_node to use as a loop cursor.
     * @n:		another &struct hlist_node to use as temporary storage
     * @head:	the head for your list.
     * @member:	the name of the hlist_node within the struct.
     */
    #define hlist_for_each_entry_safe(tpos, pos, n, head, member) 		 
        for (pos = (head)->first;					 
             pos && ({ n = pos->next; 1; }) && 				 
            ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); 
             pos = n)
    
    #endif
    
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  • 原文地址:https://www.cnblogs.com/PyLearn/p/10138644.html
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