common method for developing

using System;
using System.Text;
using System.Collections.Generic;

namespace UcApi
{
/// <summary>
/// 一些公共函数和工具类
/// </summary>
public class Discuz
{

public enum DiscuzAuthcodeMode { Encode, Decode };
/// <summary>
/// 从字符串的指定位置截取指定长度的子字符串
/// </summary>
/// <param name="str">原字符串</param>
/// <param name="startIndex">子字符串的起始位置</param>
/// <param name="length">子字符串的长度</param>
/// <returns>子字符串</returns>
public static string CutString(string str, int startIndex, int length)
{
if (startIndex >= 0)
{
if (length < 0)
{
length = length * -1;
if (startIndex - length < 0)
{
length = startIndex;
startIndex = 0;
}
else
{
startIndex = startIndex - length;
}
}

if (startIndex > str.Length)
{
return "";
}

}
else
{
if (length < 0)
{
return "";
}
else
{
if (length + startIndex > 0)
{
length = length + startIndex;
startIndex = 0;
}
else
{
return "";
}
}
}

if (str.Length - startIndex < length)
{
length = str.Length - startIndex;
}

return str.Substring(startIndex, length);
}

/// <summary>
/// 从字符串的指定位置开始截取到字符串结尾的了符串
/// </summary>
/// <param name="str">原字符串</param>
/// <param name="startIndex">子字符串的起始位置</param>
/// <returns>子字符串</returns>
public static string CutString(string str, int startIndex)
{
return CutString(str, startIndex, str.Length);
}

/// <summary>
/// 解析一个类似URL地址
/// </summary>
/// <param name="strUrl">URL GET地址</param>
/// <returns></returns>
public static Dictionary<string, string> parse_str(string strUrl)
{
//StringBuilder sb=new StringBuilder();
Dictionary<string, string> GetUrl = new Dictionary<string, string>();
if (string.IsNullOrEmpty(strUrl))
{
return GetUrl;
}

string[] ss = strUrl.Split('&');
for (int i = 0; i < ss.Length; i++)
{
string[] s1=ss[i].Split('=');
if(s1.Length>0)
GetUrl.Add(s1[0],s1[1]);
}
return GetUrl;

}

/// <summary>
/// 返回文件是否存在
/// </summary>
/// <param name="filename">文件名</param>
/// <returns>是否存在</returns>
public static bool FileExists(string filename)
{
return System.IO.File.Exists(filename);
}

/// <summary>
/// MD5函数
/// </summary>
/// <param name="str">原始字符串</param>
/// <returns>MD5结果</returns>
public static string MD5(string str)
{
byte[] b = System.Text.Encoding.Default.GetBytes(str);
b = new System.Security.Cryptography.MD5CryptoServiceProvider().ComputeHash(b);
string ret = "";
for (int i = 0; i < b.Length; i++)
{
ret += b[i].ToString("x").PadLeft(2, '0');
}
return ret;
}

/// <summary>
/// 对字符串进行 base64 编码
/// </summary>
/// <param name="str">原始字串</param>
/// <returns>结果</returns>
public static string Base64Encode(string str)
{
try
{
byte[] bytes_1 = System.Text.Encoding.Default.GetBytes(str);
return System.Convert.ToBase64String(bytes_1);
}
catch
{
return "";
}

}

public static string Base64Decode(string str)
{
try
{
byte[] bytes_2 = Convert.FromBase64String(str);
return System.Text.Encoding.Default.GetString(bytes_2);
}
catch
{
return "";
}
}

/// <summary>
/// 字段串是否为Null或为""(空)
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
public static bool StrIsNullOrEmpty(string str)
{
//#if NET1
if (str == null || str.Trim() == "")
{
return true;
}

return false;
}

/// <summary>
/// 用于 RC4 处理密码
/// </summary>
/// <param name="pass">密码字串</param>
/// <param name="kLen">密钥长度，一般为 256</param>
/// <returns></returns>
static private Byte[] GetKey(Byte[] pass, Int32 kLen)
{
Byte[] mBox = new Byte[kLen];

for (Int64 i = 0; i < kLen; i++)
{
mBox[i] = (Byte)i;
}
Int64 j = 0;
for (Int64 i = 0; i < kLen; i++)
{
j = (j + mBox[i] + pass[i % pass.Length]) % kLen;
Byte temp = mBox[i];
mBox[i] = mBox[j];
mBox[j] = temp;
}
return mBox;
}

/// <summary>
/// 生成随机字符
/// </summary>
/// <param name="lens">随机字符长度</param>
/// <returns>随机字符</returns>
public static string RandomString(int lens)
{
char[] CharArray = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
int clens = CharArray.Length;
string sCode = "";
Random random = new Random();
for (int i = 0; i < lens; i++)
{
sCode += CharArray[random.Next(clens)];
}
return sCode;
}

/// <summary>
/// 使用 Discuz authcode 方法对字符串加密
/// </summary>
/// <param name="source">原始字符串</param>
/// <param name="key">密钥</param>
/// <param name="expiry">加密字串有效时间，单位是秒</param>
/// <returns>加密结果</returns>
public static string DiscuzAuthcodeEncode(string source, string key, int expiry)
{
return DiscuzAuthcode(source, key, DiscuzAuthcodeMode.Encode, expiry);

}

/// <summary>
/// 使用 Discuz authcode 方法对字符串加密
/// </summary>
/// <param name="source">原始字符串</param>
/// <param name="key">密钥</param>
/// <returns>加密结果</returns>
public static string DiscuzAuthcodeEncode(string source, string key)
{
return DiscuzAuthcode(source, key, DiscuzAuthcodeMode.Encode, 0);

}

/// <summary>
/// 使用 Discuz authcode 方法对字符串解密
/// </summary>
/// <param name="source">原始字符串</param>
/// <param name="key">密钥</param>
/// <returns>解密结果</returns>
public static string DiscuzAuthcodeDecode(string source, string key)
{
return DiscuzAuthcode(source, key, DiscuzAuthcodeMode.Decode, 0);

}

/// <summary>
/// 使用 变形的 rc4 编码方法对字符串进行加密或者解密
/// </summary>
/// <param name="source">原始字符串</param>
/// <param name="key">密钥</param>
/// <param name="operation">操作 加密还是解密</param>
/// <param name="expiry">加密字串过期时间</param>
/// <returns>加密或者解密后的字符串</returns>
private static string DiscuzAuthcode(string source, string key, DiscuzAuthcodeMode operation, int expiry)
{

if (source == null || key == null)
{
return "";
}

int ckey_length = 4;
string keya, keyb, keyc, cryptkey, result;
string timestamp = UnixTimestamp();

key = MD5(key);
keya = MD5(CutString(key, 0, 16));
keyb = MD5(CutString(key, 16, 16));
keyc = ckey_length > 0 ? (operation == DiscuzAuthcodeMode.Decode ? CutString(source, 0, ckey_length) : RandomString(ckey_length)) : "";

cryptkey = keya + MD5(keya + keyc);

if (operation == DiscuzAuthcodeMode.Decode)
{
byte[] temp;
try
{
temp = System.Convert.FromBase64String(CutString(source, ckey_length));
}
catch
{
try
{
temp = System.Convert.FromBase64String(CutString(source + "=", ckey_length));
}
catch
{
try
{
temp = System.Convert.FromBase64String(CutString(source + "==", ckey_length));
}
catch
{
return "";
}
}
}

result = System.Text.Encoding.Default.GetString(RC4(temp, cryptkey));
if (CutString(result, 10, 16) == CutString(MD5(CutString(result, 26) + keyb), 0, 16))
{
return CutString(result, 26);
}
else
{
return "";
}
}
else
{
source = "0000000000" + CutString(MD5(source + keyb), 0, 16) + source;
byte[] temp = RC4(System.Text.Encoding.Default.GetBytes(source), cryptkey);
return keyc + System.Convert.ToBase64String(temp);

}

}

/// <summary>
/// RC4 原始算法
/// </summary>
/// <param name="input">原始字串数组</param>
/// <param name="pass">密钥</param>
/// <returns>处理后的字串数组</returns>
private static Byte[] RC4(Byte[] input, String pass)
{
if (input == null || pass == null) return null;

Encoding enc_default = System.Text.Encoding.Default;

byte[] output = new Byte[input.Length];
byte[] mBox = GetKey(enc_default.GetBytes(pass), 256);

// 加密
Int64 i = 0;
Int64 j = 0;
for (Int64 offset = 0; offset < input.Length; offset++)
{
i = (i + 1) % mBox.Length;
j = (j + mBox[i]) % mBox.Length;
Byte temp = mBox[i];
mBox[i] = mBox[j];
mBox[j] = temp;
Byte a = input[offset];
//Byte b = mBox[(mBox[i] + mBox[j] % mBox.Length) % mBox.Length];
// mBox[j] 一定比 mBox.Length 小，不需要在取模
Byte b = mBox[(mBox[i] + mBox[j]) % mBox.Length];
output[offset] = (Byte)((Int32)a ^ (Int32)b);
}

return output;
}

public static string AscArr2Str(byte[] b)
{
return System.Text.UnicodeEncoding.Unicode.GetString(
System.Text.ASCIIEncoding.Convert(System.Text.Encoding.ASCII,
System.Text.Encoding.Unicode, b)
);
}

public static string UnixTimestamp()
{
DateTime dtStart = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970, 1, 1));
DateTime dtNow = DateTime.Parse(DateTime.Now.ToString());
TimeSpan toNow = dtNow.Subtract(dtStart);
string timeStamp = toNow.Ticks.ToString();
return timeStamp.Substring(0, timeStamp.Length - 7);
}

}
}