package cn.Douzi.ReadWriter;

import java.util.Scanner;

public class ReadWrite {

    static public int count = 0;                //读者数量

    static public int wcnt = 0;                 //写者数量

    static public int REATIME = 1500;           //读者休眠时间

    static public int WRITIME = 1000;           //写者休眠时间

    static public boolean wFlag = false;        //写信号 - 用于实现写优先

    static public boolean rFlag = false;        //读信号

    static public Mutex mutex = new Mutex(1);   //用于保护更新count变量时的互斥

    static public Mutex rw = new Mutex(1);      //用于保证读者和写者互斥的访问文件

    static public StringBuilder file = new StringBuilder("空");

    public static void main(String[] args) {

        System.out.println("|-----------------------------------------------------------|");

        System.out.println("|                                                           |");

        System.out.println("|                   Welcome to My System !                  |");

        System.out.println("|                    ↖   By Douzi   2017 ↗                                                                        |");

        System.out.println("|                      读写程序开始进行                                                                               |");

        System.out.println("|                                                           |");

        System.out.println("|-----------------------------------------------------------|");

        Scanner scaner = new Scanner(System.in);

        System.out.println("设置读进程休眠时间: ");

        REATIME = scaner.nextInt();

        System.out.println("设置写进程休眠时间: ");

        WRITIME = scaner.nextInt();

        Writer w = new Writer();

        Reader r = new Reader();

        Thread t1 = new Thread(w);

        Thread t2 = new Thread(r);

        t1.start(); t2.start();

    }

}

class Writer implements Runnable {

    @Override

    public void run() {

        // TODO Auto-generated method stub

        while (true) {

            try {

                Thread.sleep(ReadWrite.WRITIME);

            } catch (InterruptedException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

            if (!ReadWrite.wFlag && !ReadWrite.rFlag) {      //在无写进程请求时进入

                synchronized (ReadWrite.rw)  {               //互斥访问共享文件

                    System.out.println("写文件...........");   //写入

                    System.out.println("文件:" + ReadWrite.wcnt + "\n");

                    ReadWrite.file.append("文件:" + ReadWrite.wcnt++ + " - ");

                    if (ReadWrite.wcnt % 5 == 0) {

                        ReadWrite.file.append("\n");

                    }

                }

            } else {

                break;

            }

        }

    }

}

class Reader implements Runnable {

    @Override

    public void run() {

        // TODO Auto-generated method stub

        while (true) {

            try {

                Thread.sleep(ReadWrite.REATIME);

            } catch (InterruptedException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

            if (!ReadWrite.wFlag) {                  //在无写进程请求时进入

                synchronized (ReadWrite.mutex) {     //互斥访问count变量

                    if (ReadWrite.count == 0) {      //当第一个读进程读共享文件时

                        ReadWrite.rFlag = true;

                    }

                    ReadWrite.count++;               //读者计数器

                    System.out.println("读者数:" + ReadWrite.count );

                }

            } else {

                System.out.println("已有写进程,暂不读文件............\n");

                break;

            }

            System.out.println("读文件: " + ReadWrite.file + "\n");

            synchronized (ReadWrite.mutex) {        //互斥访问count变量

                ReadWrite.count--;                  //读者计数器减1, 只有读者=0时候，才能继续写

                if (ReadWrite.count == 0) {         //当最后一个读进程读完共享文件

                    ReadWrite.rFlag = false;

                }

            }

        }

    }

}

class Data {

    private int data;

    public Data(int data) {

        super();

        this.data = data;

    }

    public int getData() {

        return data;

    }

}

class Mutex {

    private int mutex;

    public Mutex(int mutex) {

        super();

        this.mutex = mutex;

    }

}

class Buffer {

    private int full;

    private int empty;

    public Buffer(int full, int empty) {

        super();

        this.full = full;

        this.empty = empty;

    }

}