package com.vci.server.volume.delegate;

import java.util.Hashtable;

/**
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2009</p>
 * <p>Company: VCI</p>
 * @author eddie
 * @time 2009-8-17
 * @version 1.0
 */
public class FileControl {

	private static Hashtable<String, FileStruct> array = new Hashtable<String, FileStruct>();
	
	public FileControl() {
	}

	public synchronized boolean lockRead(String fileName){
		FileStruct fileStruct = (FileStruct)array.get(fileName);
		
	    if(fileStruct == null){
	        fileStruct= new FileStruct();
	        fileStruct.setRead(true);
	        fileStruct.addReader();
	        array.put(fileName,fileStruct);
	        return true;
	    } else if(!fileStruct.isWrite()){
	        fileStruct.addReader();
	        array.put(fileName,fileStruct);
	        return true;
	    } else {
	    	return false;
	    }
	}

    public synchronized boolean lockWrite(String fileName){
    	FileStruct fileStruct = (FileStruct)array.get(fileName);
	    
    	if(fileStruct == null){
	        fileStruct= new FileStruct();
	        fileStruct.setWrite(true);
	        array.put(fileName,fileStruct);
	        return true;
	    } else {
	    	return false;
	    }
    }

    public synchronized void unlockRead(String fileName){
	    FileStruct fileStruct = (FileStruct)array.get(fileName);
	    
	    if(fileStruct != null){
	        fileStruct.subReader();
	        array.put(fileName,fileStruct);
	        if(fileStruct.getReadNum() == 0){
	            array.remove(fileName);
	        }
	    }
    }

    public synchronized void unlockWrite(String fileName){
	    FileStruct fileStruct = (FileStruct)array.get(fileName);
	    if(fileStruct != null){
	        array.remove(fileName);
	    }
    }
}