namespace BaiRong.Core

{

public class Base64Decoder

{

// Fields

private int blockCount;

public static Base64Decoder Decoder = new Base64Decoder();

private int length;

private int length2;

private int length3;

private int paddingCount;

private char[] source;

// Methods

private byte char2sixbit(char c)

{

var lookupTable = 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', '+', '/'

};

if (c != '=')

{

for (var x = 0; x < 0x40; x++)

{

if (lookupTable[x] == c)

{

return (byte)x;

}

}

}

return 0;

}

public byte[] GetDecoded(string strInput)

{

int x;

init(strInput.ToCharArray());

var buffer = new byte[length];

var buffer2 = new byte[length2];

for (x = 0; x < length; x++)

{

buffer[x] = char2sixbit(source[x]);

}

for (x = 0; x < blockCount; x++)

{

var temp1 = buffer[x * 4];

var temp2 = buffer[(x * 4) + 1];

var temp3 = buffer[(x * 4) + 2];

var temp4 = buffer[(x * 4) + 3];

var b = (byte)(temp1 << 2);

var b1 = (byte)((temp2 & 0x30) >> 4);

b1 = (byte)(b1 + b);

b = (byte)((temp2 & 15) << 4);

var b2 = (byte)((temp3 & 60) >> 2);

b2 = (byte)(b2 + b);

b = (byte)((temp3 & 3) << 6);

var b3 = temp4;

b3 = (byte)(b3 + b);

buffer2[x * 3] = b1;

buffer2[(x * 3) + 1] = b2;

buffer2[(x * 3) + 2] = b3;

}

length3 = length2 - paddingCount;

var result = new byte[length3];

for (x = 0; x < length3; x++)

{

result[x] = buffer2[x];

}

return result;

}

private void init(char[] input)

{

var temp = 0;

source = input;

length = input.Length;

for (var x = 0; x < 2; x++)

{

if (input[(length - x) - 1] == '=')

{

temp++;

}

}

paddingCount = temp;

blockCount = length / 4;

length2 = blockCount * 3;

}

}

}