/**
 * Copyright &copy; 2012-2014 <a href="https://github.com/thinkgem/jeesite">JeeSite</a> All rights reserved.
 */
package com.nis.util;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.apache.commons.codec.digest.DigestUtils;

/**
 * 字符串工具类, 继承org.apache.commons.lang3.StringUtils类
 * @author ThinkGem
 * @version 2013-05-22
 */
public class MD5Utils {

	/**
	 * 字符串转为MD532位小写
	 * @param plain
	 * @return
	 */
	public static String md5LowerCase(String plain) throws Exception {
		String re_md5 = new String();
		MessageDigest md = MessageDigest.getInstance("MD5");
		md.update(plain.getBytes());
		byte b[] = md.digest();

		int i;

		StringBuffer buf = new StringBuffer("");
		for (int offset = 0; offset < b.length; offset++) {
			i = b[offset];
			if (i < 0)
				i += 256;
			if (i < 16)
				buf.append("0");
			buf.append(Integer.toHexString(i));
		}

		re_md5 = buf.toString();
		return re_md5;
	}

	public static byte[] createChecksum(String filename) throws IOException, NoSuchAlgorithmException {
		InputStream 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();
	}

	public static String getMD5Checksum(String filename) throws NoSuchAlgorithmException, IOException {
		byte[] b = createChecksum(filename);
		StringBuffer result = new StringBuffer();
		for (int i = 0; i < b.length; i++) {
			result.append(Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1));
		}
		return result.toString();
	}

	public static void main(String[] args) throws NoSuchAlgorithmException, IOException {
		long start1 = System.currentTimeMillis();
		String md5Checksum = getMd5ByIS(new FileInputStream("f:\\1.iso"));
		System.out.println(md5Checksum);
		long start2 = System.currentTimeMillis();
		System.out.println("第一次用时" + (start2 - start1));
		String md5Checksum1 = getMD5Checksum("f:\\1.iso");
		long start3 = System.currentTimeMillis();
		System.out.println(md5Checksum1);
		System.out.println("第二次用时" + (start3 - start2));

	}

	/**
	 * 这种方式计算大文件时更快一些
	 * @param fis
	 * @return
	 * @throws IOException
	 * @throws NoSuchAlgorithmException
	 */
	public static String getMd5ByIS(InputStream is) throws IOException, NoSuchAlgorithmException {
		return DigestUtils.md5Hex(is);
	}
}