分页存储方式管理模拟 C++实现

分页存储方式管理模拟 C++实现

1.任务要求

目的：了解分页存储管理方式的原理和实现的基本过程。
设计要求：设计一个简单分页存储管理系统，要求实现以下功能。
（1） 定义分页的地址结构和页表结构。
（2） 对进程的逻辑地址空间、页表起址、给定的逻辑地址进行初始化。
（3） 实现从逻辑地址到物理地址的变换。
（4） 实现“主存空间的共享和保护”功能。
（5） 实现“主存扩充”虚拟功能。

2.代码实现

C++源码如下(编译环境:Mingw-w64/gcc 8.1.0):

 //物理块：4KB; 物理块数：256；共享状态：1共享，0不共享；访问状态：1访问过，0未访问过
 #include 
 #include 
 #include 
 #include 
 #include 
 
 using namespace std;

 int init();                //初始化
 int show_Share_Page();     //展示共享页表

 int t = 1;
 int p = -1;  //clock算法指针
 int q = 0;
 int c = 0;

 int ram_block_state[256];               //物理块分配状态

 struct Pages_item {                       //页表项
     int pages_num;
     int ram_block_num;
     int share_state; //1共享，0不共享
     int position_state;//1在内存，0不在内存
     int visit;//1最近被访问；0最近未被访问
 };

 struct share_page_item                     //共享页表项
 {
     int pro_id;
     int pages_num;
     int share_state;
 };

 vector<share_page_item> Share_Page;    //共享页表

class PCB
{
    int id;
    int page_item_sum;
    int ram_block[5];
    vector<Pages_item> Page;
public:
    PCB();
    int show();        //展示页表
    int inquiry();     //输入逻辑地址，并转化为物理地址
    int clock();       //置换算法；    
};

PCB::PCB()
{
     id = t++;
     int r = 0;
     srand(time(0));

    //分配进程物理块
     for (int i = 0; i < 5; i++)
     {
        while (1)
        {
            int a = 0;
            ram_block[i] = rand() % 0xff + 1;
            if (ram_block_state[ram_block[i]] == 0)
            {
                ram_block_state[ram_block[i]] = 1;
                break;
            }
            else 
                a++;
            if (a == 256)
            {
                cout << "物理内存不足，无法分配\n";
                system("pause");
                exit(0);
            }
        }

        for (int j = 0; j < i; j++)
        {
            if (ram_block[i] == ram_block[j])
            {
                r = 1;
                break;
            }
        }
        if (r == 1)
        {
            r = 0;
            i--;
        }
     }

    //分配进程页数
     page_item_sum = rand() % 10 + 3;
     for (int i = 0; i < page_item_sum; i++)
     {
            Pages_item a;
            a.pages_num = i + 1;

            if (i < 5)
                a.ram_block_num = i;
            else
                a.ram_block_num = 10000;//为分配物理块

            a.share_state = rand() % 2;

            if (a.ram_block_num == 10000)
                a.position_state = 0;
            else
                a.position_state = 1;
            
            a.visit = 0;

            Page.push_back(a);

            share_page_item b;

            //将共享页加入共享页表
            if (a.share_state == 1)
            {
                b.pro_id = id;
                b.pages_num = a.pages_num;
                b.share_state = a.share_state;
                Share_Page.push_back(b);
            }
     }

 }

int PCB::show()
{
    cout << id << "进程的页表为：\n";
    cout << "页号\t" << "物理块号\t" << "共享状态\t" << "存储状态\t" << "访问位\n";
    for (int i = 0; i < page_item_sum; i++)
        if (Page[i].position_state == 1)
            cout << setiosflags(ios::uppercase) << hex << Page[i].pages_num 
                 << "\t" << ram_block[Page[i].ram_block_num] << "\t\t" << Page[i].share_state
                 << "\t\t" << Page[i].position_state << "\t\t" << Page[i].visit << endl;
        else
        {
            cout << setiosflags(ios::uppercase) << hex << Page[i].pages_num 
                 << "\t\t\t" << Page[i].share_state << "\t\t" << Page[i].position_state << "\t\t" 
                 << Page[i].visit << endl;
        }
    cout << endl; 
    return 0;
}

int PCB::inquiry()
{
    cout << "请输入逻辑地址(5位十六进制地址): ";
    int a, page_num, pagein_address, ram_block_, b = 0, physics_address;
    while (!(cin >> hex >> a) || a < 0x1000)
    {
        cin.clear();
        cin.sync();
        cout << "地址格式输入错误，请重新输入！\n" 
             << "请输入逻辑地址(5位十六进制地址): ";
    }
    page_num = a / 0x1000;
    pagein_address = a % 0x1000;

    for (int i = 0; i < page_item_sum; i++)
        if (Page[i].pages_num == page_num)
        {
            b = 1;

            if (Page[i].position_state == 0)
            {
                int a = clock(); //选择出要置换的页面
                int t = Page[a].ram_block_num;
                Page[a].ram_block_num = Page[i].ram_block_num;
                Page[i].ram_block_num = t;
                Page[i].position_state = 1;
                Page[a].position_state = 0;
            }

            ram_block_ = ram_block[Page[i].ram_block_num];
            Page[i].visit = 1;
            break;
        }
    if (b == 0)
    {
        cout << "输入错误，地址越界！\n";
        system("pause");
        exit(0);
    }

    physics_address = ram_block_ * 0x1000 + pagein_address;

    cout << "物理地址为：" << setiosflags(ios::uppercase) << hex << physics_address << endl << endl;

    return 0;
}

int PCB::clock()
{
    p = ++p % page_item_sum;
    for (; p < page_item_sum; p++)
        if (Page[p].visit == 1)
            Page[p].visit = 0;
        else
            break;
    return p;
}

int init()
{
    for (int i = 0; i < 256; i++)
        ram_block_state[i] = 0;
    return 0;
}

int show_Share_Page()
{
    cout << "\n共享页表:\n";
    cout << "进程号\t" << "页号\t" << "共享状态\n";
    int a = Share_Page.size();
    for (int i = 0; i < a; i++)
        cout << Share_Page[i].pro_id << "\t" << Share_Page[i].pages_num
             << "\t" << Share_Page[i].share_state << endl;
    cout << endl;
    return 0;
}

int main()
{
    init();
    PCB one;
    PCB two;
    int b = 0;
    int c = 0;
    while (1)
    {
        if (b == 0)
        {
            one.show();
            two.show();
        }
        if (c == 0)
        {
            cout << "程序有如下功能：\n"
                 << "1.输入1进程的逻辑地址\n"
                 << "2.输入2进程的逻辑地址\n"
                 << "3.显示共享页表\n"
                 << "4.结束程序\n\n"
                 << "请选择一个功能选项：";
        }
        int a;
        cin >> a;
        if (a == 1)
        {
            one.inquiry();
            b = 0;
            c = 0;
        }
        else if (a == 2)
        {
            two.inquiry();
            b = 0;
            c = 0;
        }
        else if (a == 3)
        {
            show_Share_Page();
            b = 1;
            c = 0;
        }
        else if (a == 4)
            break;
        else
        {
            cout << "输入错误，请重新输入！";
            b = 1;
            c = 1;
            continue;
        }
    }
    system("pause");
    return 0;
}