package com.vci.server.volume.uitls;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Arrays;
import java.util.zip.CRC32;

import org.apache.axis.utils.StringUtils;

public class EncryFileUtil {
	public static int ENCRYHEADERSIZE = 13;
	
	public static boolean isEncryFile(String fileName) {
		File file = new File(fileName);
		if (!file.exists())
			return false;
		
		if (file.length() < ENCRYHEADERSIZE)
			return false;
		
		try {
			FileInputStream in = new FileInputStream(file);
			byte[] data = new byte[ENCRYHEADERSIZE];
			in.read(data, 0, ENCRYHEADERSIZE);
			in.close();
			
			byte[] header = getEncryHeader(fileName);
			return Arrays.equals(data, header);
			
		} catch (IOException e) {
			return false;
		}
	}

	public static boolean isEncryFile(File file) {
		if (!file.exists())
			return false;
		
		if (file.length() < ENCRYHEADERSIZE)
			return false;
		
		try {
			FileInputStream in = new FileInputStream(file);
			byte[] data = new byte[ENCRYHEADERSIZE];
			in.read(data, 0, ENCRYHEADERSIZE);
			in.close();
			
			
			byte[] header = getEncryHeader(file.getPath());
			return Arrays.equals(data, header);
			
		} catch (IOException e) {
			return false;
		}
	}

	public static byte[] getEncryHeader(String fileName) {
		if (StringUtils.isEmpty(fileName))
			return null;
		
		long crc = 0;
		File file = new File(fileName);
		String name = file.getName().toLowerCase();
		crc = getCRC(name);
		
		// 先写入“VEH1#”标识
        byte[] data = new byte[ENCRYHEADERSIZE];
        data[0] = (byte)'V';
        data[1] = (byte)'E';
        data[2] = (byte)'H';
        data[3] = (byte)'1';
        data[4] = (byte)'#';
        
		long temp = crc;
        for (int i = 0; i < 8; i++) { 
        	data[i + 5] = new Long(temp & 0xff).byteValue();// 
            temp = temp >> 8; // 向右移8位 
        }
        
		
	    return data;
	}
	
    /**
     * 计算CRC16校验码
     *
     * @param bytes
     * @return
     */
    private static long getCRC(String text) {
    	byte[] b = text.getBytes();
    	CRC32 c = new CRC32();
    	c.reset();//Resets CRC-32 to initial value.
    	c.update(b, 0, b.length);//将数据丢入CRC32解码器
    	long value = (int) c.getValue();//获取CRC32 的值  默认返回值类型为long 用于保证返回值是一个正数
    	
    	return value;
    }
}