Exemplo n.º 1
0
        /// <summary>
        /// Convert a Base62 string to byte array
        /// </summary>
        /// <param name="base62">Base62 string</param>
        /// <returns>Byte array</returns>
        public static byte[] FromBase62(string base62)
        {
            // Character count
            int count = 0;

            // Set up the BitStream
            BitStream stream = new BitStream(base62.Length * 6 / 8);

            foreach (char c in base62)
            {
                // Look up coding table
                int index = Base62CodingSpace.IndexOf(c);

                // If end is reached
                if (count == base62.Length - 1)
                {
                    // Check if the ending is good
                    int mod = (int)(stream.Position % 8);
                    if (mod == 0)
                        throw new InvalidDataException("an extra character was found");

                    if ((index >> (8 - mod)) > 0)
                        throw new InvalidDataException("invalid ending character was found");

                    stream.Write(new byte[] { (byte)(index << mod) }, 0, 8 - mod);
                }
                else
                {
                    // If 60 or 61 then only write 5 bits to the stream, otherwise 6 bits.
                    if (index == 60)
                    {
                        stream.Write(new byte[] { 0xf0 }, 0, 5);
                    }
                    else if (index == 61)
                    {
                        stream.Write(new byte[] { 0xf8 }, 0, 5);
                    }
                    else
                    {
                        stream.Write(new byte[] { (byte)index }, 2, 6);
                    }
                }
                count++;
            }

            // Dump out the bytes
            byte[] result = new byte[stream.Position / 8];
            stream.Seek(0, SeekOrigin.Begin);
            stream.Read(result, 0, result.Length * 8);
            return result;
        }
Exemplo n.º 2
0
 /// <summary>
 /// Convert a byte array
 /// </summary>
 /// <param name="original">Byte array</param>
 /// <returns>Base62 string</returns>
 public static string ToBase62(byte[] original)
 {
     StringBuilder sb = new StringBuilder();
     BitStream stream = new BitStream(original);         // Set up the BitStream
     byte[] read = new byte[1];                          // Only read 6-bit at a time
     while (true)
     {
         read[0] = 0;
         int length = stream.Read(read, 0, 6);           // Try to read 6 bits
         if (length == 6)                                // Not reaching the end
         {
             if ((int)(read[0] >> 3) == 0x1f)            // First 5-bit is 11111
             {
                 sb.Append(Base62CodingSpace[61]);
                 stream.Seek(-1, SeekOrigin.Current);    // Leave the 6th bit to next group
             }
             else if ((int)(read[0] >> 3) == 0x1e)       // First 5-bit is 11110
             {
                 sb.Append(Base62CodingSpace[60]);
                 stream.Seek(-1, SeekOrigin.Current);
             }
             else                                        // Encode 6-bit
             {
                 sb.Append(Base62CodingSpace[(int)(read[0] >> 2)]);
             }
         }
         else if (length == 0)                           // Reached the end completely
         {
             break;
         }
         else                                            // Reached the end with some bits left
         {
             // Padding 0s to make the last bits to 6 bit
             sb.Append(Base62CodingSpace[(int)(read[0] >> (int)(8 - length))]);
             break;
         }
     }
     return sb.ToString();
 }