/// <summary>
/// 获取Url别名
/// </summary>
/// <param name="url">需要处理的Url</param>
/// <param name="urlExists">Url是否已存在</param>
/// <returns>返回Url别名</returns>
public string GetUrlAlias(string url, out bool urlExists)
{
ShortUrlSettings settings = shortUrlSettingsManager.Get();
//生成别名的个数
int generateCount = 4;
//要使用生成URL的字符
string[] chars = new string[] {
"a", "b", "c", "d", "e", "f", "g", "h",
"i", "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", "A", "B", "C", "D",
"E", "F", "G", "H", "I", "J", "K", "L",
"M", "N", "O", "P", "Q", "R", "S", "T",
"U", "V", "W", "X", "Y", "Z"
};
//对传入网址进行MD5加密
string urlSalt = EncryptionUtility.MD5(url);
string[] aliases = new string[generateCount];
for (int i = 0; i < generateCount; i++)
{
//把加密字符按照8位一组16进制与0x3FFFFFFF进行位与运算
int hexint = 0x3FFFFFFF & Convert.ToInt32("0x" + urlSalt.Substring(i * 8, 8), 16);
for (int j = 0; j < 6; j++)
{
//把得到的值与0x0000003D进行位与运算，取得字符数组chars索引
int index = 0x0000003D & hexint;
//把取得的字符相加
aliases[i] += chars[index];
//每次循环按位右移5位
hexint = hexint >> 5;
}
}
return(shortUrlRepository.GetUnusedAlias(aliases, url, out urlExists));
}
