using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

/// <summary>
/// MD5相关工具集
/// </summary>
public partial class Utils
{
    /// <summary>
    /// 计算内存数据MD5值
    /// </summary>
    /// <returns>MD5值</returns>
    /// <param name="buffer">内存数据</param>
    public static string Md5(byte[] buffer)
    {
        MD5 md5 = new MD5CryptoServiceProvider();
        byte[] retVal = md5.ComputeHash(buffer);

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < retVal.Length; i++)
        {
            sb.Append(retVal[i].ToString("x2"));
        }
        return sb.ToString();
    }

    /// <summary>
    /// 计算字符串的MD5值
    /// </summary>
    /// <param name="source">源串</param>
    /// <returns>换算后的字符串</returns>
    public static string Md5(string source)
    {
        MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
        byte[] data = Encoding.UTF8.GetBytes(source);
        byte[] md5Data = md5.ComputeHash(data, 0, data.Length);
        md5.Clear();

        string destString = "";
        for (int i = 0; i < md5Data.Length; i++)
        {
            destString += Convert.ToString(md5Data[i], 16).PadLeft(2, '0');
        }
        destString = destString.PadLeft(32, '0');
        return destString;
    }

    /// <summary>
    /// 计算文件的MD5值
    /// </summary>
    /// <param name="file">文件的绝对路径</param>
    /// <returns>md5值</returns>
    public static string Md5File(string file)
    {
        try
        {
            FileStream fs = new FileStream(file, FileMode.Open);
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] retVal = md5.ComputeHash(fs);
            fs.Close();

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < retVal.Length; i++)
            {
                sb.Append(retVal[i].ToString("x2"));
            }
            return sb.ToString();
        }
        catch (Exception ex)
        {
            throw new Exception("Md5File() fail, INFO:" + ex.Message);
        }
    }
}