1 using System;  2 using System.Collections.Generic;  3 using System.Linq;  4 using System.Text;  5 using System.Threading.Tasks;  6   7 namespace Libraries  8 {  9     public class Base64Crypt 10     { 11         PRivate string S; 12         private string K; 13         private List<char> T; 14         public Base64Crypt() 15         { 16             T = new List<char>(); 17             K = "あいうえおかきくけこさしすせそたちつてとなにぬねのはひふへほまみむめもやよらりるれろわをぐげござじずぞだぢづでばびぶべぱぴぷぺぽ"; 18             //K = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";//標準碼表 19         } 20         public string Token 21         { 22             get 23             { 24                 return S == null ? K : S; 25             } 26             set 27             { 28                 T.Clear(); 29                 S = value; 30                 if (S == null) 31                 { 32                     foreach (var item in K) 33                     { 34                         T.Add(item); 35                     } 36                 }else if (S.Length < 64) 37                 { 38                     foreach (var item in S) 39                     { 40                         T.Add(item); 41                     } 42                     for (int i = 0; i < 64-S.Length; i++) 43                     { 44                         T.Add(K[i]); 45                     } 46                 } 47                 else 48                 { 49                     for (int i = 0; i < 64; i++) 50                     { 51                         T.Add(S[i]); 52                     } 53                 } 54             } 55         } 56  57         public string Encode(string x) 58         { 59             return string.IsNullOrEmpty(x) ? x : InternalEncode(Encoding.UTF8.GetBytes(x)); 60         } 61         public string Decode(string x) 62         { 63             return string.IsNullOrEmpty(x) ? x : Encoding.UTF8.GetString(InternalDecode(x)); 64         } 65  66         public byte[] Encode(byte[] x) 67         { 68             return x == null ? null : Encoding.UTF8.GetBytes(InternalEncode(x)); 69         } 70         public byte[] Decode(byte[] x) 71         { 72             return x == null ? null : InternalDecode(Encoding.UTF8.GetString(x)); 73         } 74         private void CheckToken() 75         { 76             if (T.Count != 64) 77             { 78                 Token = K; 79             } 80         } 81         private byte[] InternalDecode(string x) 82         { 83             CheckToken(); 84             byte[] r; 85             string t; 86             int p = 0; 87             int m = x.Length / 4; 88             int n = x.Length % 4; 89             if (n == 0) 90             { 91                 r = new byte[3 * m]; 92             } 93             else 94             { 95                 r = new byte[3 * m + n-1]; 96                 t = string.Empty; 97  98                 for (int i = n; i > 0; i--) 99                 {100                     t += ByteToBin((byte)T.IndexOf(x[x.Length - i])).Substring(2);101                 }102 103                 for (int i = 0; i < n-1 ; i++)104                 {105                     r[3 * m + i] = BinToByte(t.Substring(8 * i, 8));106                 }107             }108             for (int i = 0; i < m; i++)109             {110                 t = string.Empty;111                 for (int j = 0; j < 4; j++)112                 {113                     t += ByteToBin((byte)T.IndexOf(x[4*i+j])).Substring(2);114                 }115                 for (int j = 0; j < t.Length/8; j++)116                 {117                     r[p++] = BinToByte(t.Substring(8*j,8));118                 }119             }120             return r;121         }122         private string InternalEncode(byte[] x)123         {124             CheckToken();125             string r = string.Empty;126             string t;127             int m = x.Length / 3;128             int n = x.Length % 3;129             for (int i = 0; i < m; i++)130             {131                 t = string.Empty;132                 for (int j = 0; j < 3; j++)133                 {134                     t += ByteToBin(x[3 * i + j]);135                 }136                 r += base64Encode(t);137             }138 139             if (n == 1)140             {141                 t = ByteToBin(x[x.Length-1]).PadRight(12,'0');142                 r += base64Encode(t);143             }144             else if (n == 2)145             {146                 t = string.Empty;147                 for (int i = n; i > 0; i--)148                 {149                     t += ByteToBin(x[x.Length - i]);150                 }151                 t = t.PadRight(18,'0');152                 r += base64Encode(t);153             }154             return r;155         }156         private string base64Encode(string x)157         {158             string r = string.Empty;159             for (int i = 0; i < x.Length / 6; i++)160             {161                 r += T[BinToByte(x.Substring(6 * i, 6))];162             }163             return r;164         }165         166         private string ByteToBin(byte x)167         {168             return Convert.ToString(x,2).PadLeft(8,'0');169         }170         private byte BinToByte(string x)171         {172             return Convert.ToByte(x,2);173         }174 175     }176 }177