package cn.iautos.mall.utils;

import java.io.FileInputStream;
import java.io.InputStream;
import java.security.MessageDigest;

import org.springframework.util.StringUtils;

public class CheckHashUtils {
    
    
    public static String getHashByFile(String fileName) throws Exception{
        return getMD5Checksum(fileName,null);
    }
    public static String getHashByStream(InputStream fis) throws Exception{
        return getMD5Checksum(null,fis);
    }
    
    
    private static byte[] createChecksum(String filename,InputStream fis) throws Exception {
        if(!StringUtils.isEmpty(filename)){
            fis =  new FileInputStream(filename);
        }
        byte[] buffer = new byte[1024];
        MessageDigest complete = MessageDigest.getInstance("MD5");
        int numRead;

        do {
            numRead = fis.read(buffer);
            if (numRead > 0) {
                complete.update(buffer, 0, numRead);
            }
        } while (numRead != -1);

        fis.close();
        return complete.digest();
    }
 
    private static String getMD5Checksum(String filename,InputStream fis) throws Exception {
        byte[] b = createChecksum(filename,fis);
        String result = "";

        for (int i=0; i < b.length; i++) {
            result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring( 1 );
        }
        return result;
    }

}