shm_dlist.h

实 现 了 一 个 双 向 链 表. 挺 好 用 的.

/*=================================================================
** Copyright (c)2006
** All rights reserved.
**
** 文件名称：ipc_dlist.h
**
** 当前版本：1.1
** 作    者：Like
** 完成日期：2006-11-24
**
===================================================================*/

#ifndef SHM_DLIST_H
#define SHM_DLIST_H

#include <stdlib.h>
#include <stdio.h>
#include "shm_elem.h"

class ShmDList;

/******************************************************************************
** Author：       Like
** Class Name：   ShmDListIter
** Created Date:  2006-11-24
** Description:   Used to go through a ShmDList
**
** Usage:         See description of ShmDList below
******************************************************************************/

class ShmDListIter
{
    typedef ShmDListIter iterator;    
    friend class ShmDList;
    
public:
    ShmDListIter() 
        : _node(NULL)
    {
    }

    ShmDListIter(ShmElem* node)
        : _node(node)
    {
    }

    ShmDListIter(const iterator& it)
        : _node(it._node)
    {
    }

    ShmElem* operator *()
    { 
        return _node;
    }

    iterator& operator ++ ();
    
    iterator operator ++ (int)
    { 
        iterator    tmp = *this; 
        
        ++*this; 
        
        return tmp; 
    }

    bool operator == (const iterator& it) const
    { 
        return _node == it._node; 
    }
    
    bool operator != (const iterator& it) const
    { 
        return _node != it._node; 
    }

public:
    ShmElem*   _node;
};


/******************************************************************************
** Author：       Like
** Class Name：   ShmDList
** Created Date:  2006-11-24
** Description:   是一个基于共享内存的环状双向链表的实现。
** Note:          任何插入ShmDList的节点必须存放在共享内存上，并且和ShmDList
**                存放于同一个共享内存。使用ShmMgr可以实现这一目的. 
**                Please see shm_mgr.h for more details.           
**
** Usage:
**         
** Step 1: ShmMgr     shm_mgr;           创建一个共享内存管理器
**         ShmDList   dlist;             创建一个双向链表
**         char*      shared_mem = NULL;
**         ShmElem*   elem = NULL;
**      
** Step 2: shm_mgr.InitShmem(key, 1024); 初始化共享内存管理器
**         
**         // 为dlist分配一定的共享内存
** Step 3: shared_mem = shm_mgr.ShmAllocWithoutLock(ShmDList::BaseSpace());
**
**         // 初始化dlist
** Step 4: dlist.Attach(shared_mem, shm_mgr.IsCreated());  
**
**         // So far dlist can be used
** Step 5: elem = (ShmElem*) shm_mgr.ShmAllocWithoutLock(64); 
**         
**         // Insert an elem into list
** Step 6: dlish.push_back(elem); // or dlish.push_front(elem); 
**
**         // Scan a dlist
** Step 7: ShmDList::iterator it;   
** 
** Step 8: for (it = dlist.begin(); it != dlist.end(); it++)
**         {
**             elem = *it;
**
**             do something here
**         }
******************************************************************************/

typedef struct ShmDListHead
{
    int         _size;
    ShmElem     _listHead;
    
} ShmDListHead;

class ShmDList
{       
public:
    typedef ShmDListIter iterator; 
    
    ShmDList()
    {
        _location = NULL;
        _size     = NULL;
        _listHead = NULL;
    }
    
    ~ShmDList()
    {
    }

    static int BaseSpace();
    
    void Attach(char* mem_addr, int flag = 0);
    void Init();

    void push_back(ShmElem* node);
    void push_front(ShmElem* node);

    iterator erase(iterator&);
    void     clear();

    inline iterator begin()
    {                             
        return iterator((ShmElem*) MAKE_SHM_PTR(_listHead->_nextOffset)); 
    }
    
    inline iterator end()
    { 
        return iterator(_listHead); 
    }

    unsigned int size() const 
    { 
        return *_size; 
    }
           
    bool empty() const 
    { 
        return (*_size == 0); 
    }

private:
    /*************************************************************/
    // _size points to _size variable of ShmDListHead
    // which has been stored in a shared memory
    //
    // _listHead points to _listHead of ShmDListHead
    // which has been stored in a shared memory
    /*************************************************************/

    char*       _location;
    int*        _size;      
    ShmElem*    _listHead; 
};

#endif