disk.java

来自「一个简单的操作系统模拟程序 java+swing 可进行一般的文件操作 进」· Java 代码 · 共 151 行

/*
 * Disk.java,ver 0.1.1
 *
 * Created on 2006年11月30日, 下午12:26
 * 
 *This Class is used to simulate the HardDisk for the system.
 *
 *History :2006年11月30日,ver 0.1.0 first release.
 *         2006年12月27日,ver 0.1.1 second release
 *                                  add the saveToFile method 
 *
 */

package ossimulation;

import java.io.*;

/**
 *
 * @author Decell.Zhou
 */
public class Disk {
    
    private char[][] disk;
    private int blockIndex;
    
    /** Creates a new instance of Disk */
    public Disk() {
        //creat a disk.this disk has 128 Block,each block has 64 Byte.
        disk = new char[128][64];
        //disk initialization,0 stands for unused block
        for(int i = 0;i <= 127 ;i++){
            for(int j = 0; j <= 63;j++){
                disk[i][j] = 0;
            }
        }
        //block one and block two is used for store the file allocation table.
        disk[0][0] = 1;
        disk[0][1] = 1;
    }
    
    /**Search for the free block in the disk ,return its index*/
    public int findNextFree(){
        
        //search for free block
       outer:
        for(int i = 0;i <= 1;i++){
            for(int j = 0;j <= 63;j++){
                if(disk[i][j] == 0){
                    blockIndex = j + i * 64;
                    break outer;
                }
            }
        }
        //return the index
        return blockIndex;
    }
    
    /**Read one block in the disk*/
    public char[] readBlock(int argIndex){
        return disk[argIndex];
    } 
    
    /**Write something to a bolck*/
    public void writeBlock(char[] argSource,int argIndex){
        //copy the content from the source to disk
        for(int i = 0;i <=63;i++){
            disk[argIndex][i] = argSource[i]; 
        }
        //set the corresponding Byte in FAT ,indicated that the block id in used
        if(argIndex >= 64){
            disk[1][argIndex - 64] = 1;
        } else {
            disk[0][argIndex] = 1;
        }
    }
    
    /**Read the file allocation table from the disk*/
    public char[] readFAT(){
        char[] fileAlocationTable = new char[128];
        
        for(int i = 0; i <= 1; i++){
            for(int j = 0; j <= 63; j++){
                fileAlocationTable[i * 64 + j] = disk[i][j];
            }
        }
        return fileAlocationTable;
    }
    
    /**Erase one block*/
    public void eraseBlock(int argIndex){
        //clear all the imformation in the target block
        for(int i = 0; i <= 63; i++){
            disk[argIndex][i] = 0;
        }
        //set the corresponding FAT Byte to unused
        if(argIndex >= 64){
            disk[1][argIndex - 64] = 0;
        } else {
            disk[0][argIndex] = 0;
        }        
    }
    
    /**save the contend of the disk to the file*/
    public void saveToFile() throws IOException{
        PrintWriter writer = new PrintWriter(new BufferedWriter(new FileWriter("./disk.out")));
        for(int i = 0;i <= 127;i ++){
            writer.println(disk[i]);
        } 
        writer.close();
    }
    
    /**Existed only for testing this class*/
    static public void main(String[] args){
        Disk diskEntity = new Disk();
        
        // test the findNextFree function
        System.out.println(diskEntity.findNextFree());
        
        //test the writeBlockfunction
        char[] content = new char[64];
        for(int i = 0;i <= 63;i++){
            content[i] = Integer.toString(i).charAt(0);
        }
        content[0] = 'A';
        for(int i = 2;i <= 65;i ++){
            diskEntity.writeBlock(content,i);
        }
        diskEntity.writeBlock(content,127);
        System.out.println(diskEntity.findNextFree());
        
         //test the erase block function
         diskEntity.eraseBlock(4);
         System.out.println(diskEntity.findNextFree());
         
        //test the readFAT function
         char[] FAT = new char[128];
         FAT = diskEntity.readFAT();
         for(int i = 0;i <= 127; i++){
            System.out.print(FAT[i]);
         }
         System.out.println();
         //test the readBlock funtcion
         content = diskEntity.readBlock(127);
         for(int i = 0;i <= 63;i++){
            System.out.print(content[i]);
         }
    }
    
}