private string Encode(string str)
{
byte[] buffer = Encoding.Default.GetBytes(str);
byte b1, b2, b3, c1, c2, c3, c4;
string mes = string.Empty;
int count = buffer.Length / 3;
int resst = buffer.Length % 3;
for (int i = 0; i < count; i++)
{
int j = i * 3;
b1 = buffer[j];
b2 = buffer[j + 1];
b3 = buffer[j + 2];
c1 = (byte)(b1 >> 2);
c2 = (byte)(((b1 & 3) << 4) + (b2 >> 4));
c3 = (byte)(((b2 & 15) << 2) + (b3 >> 6));
c4 = (byte)(b3 & 63);
mes += GetChar(c1, c2, c3, c4);
}
if (resst == 1)
{
b1 = buffer[buffer.Length - 1];
c1 = (byte)(b1 >> 2);
c2 = (byte)((b1 & 3) << 4);
c3 = 64;
c4 = 64;
mes += GetChar(c1, c2, c3, c4);
}
else if (resst == 2)
{
b1 = buffer[buffer.Length - 2];
b2 = buffer[buffer.Length - 1];
c1 = (byte)(b1 >> 2);
c2 = (byte)(((b1 & 3) << 4) + (b2 >> 4));
c3 = (byte)((b2 & 15) << 2);
c4 = 64;
mes += GetChar(c1, c2, c3, c4);
}
return mes;
}
private string Decode(string str)
{
byte[] buffer = Encoding.Default.GetBytes(str);
byte b1, b2, b3, c1, c2, c3, c4;
string mes = string.Empty;
int count = buffer.Length / 4;
int resst = buffer.Length % 4;
for (int i = 0; i < count; i++)
{
int j = i * 4;
c1 = GetIndex(buffer[j]);
c2 = GetIndex(buffer[j + 1]);
c3 = GetIndex(buffer[j + 2]);
c4 = GetIndex(buffer[j + 3]);
b1 = (byte)((c1 << 2) + (c2 >> 4));
if (c3 != 64 && c4 != 64)
{
b2 = (byte)(((c2 & 15) << 4) + (c3 >> 2));
b3 = (byte)(((c3 & 3) << 6) + c4);
mes += Convert.ToChar(b1);
mes += Convert.ToChar(b2);
mes += Convert.ToChar(b3);
}
else if (c3 != 64 && c4 == 64)
{
b2 = (byte)(((c2 & 15) << 4) + (c3 >> 2));
mes += Convert.ToChar(b1);
mes += Convert.ToChar(b2);
}
else
mes += Convert.ToChar(b1);
}
return mes;
}
private string GetChar(byte c1, byte c2, byte c3, byte c4)
{
return new string(new char[] { cs[c1], cs[c2], cs[c3], cs[c4] });
}
private byte GetIndex(byte c)
{
for (byte i = 0; i < cs.Length; i++)
{
if (c == cs[i])
return i;
}
return 0;
}
private char[] cs = new char[]
{
'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',
'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',
'+','/','='};
