Base64 Encoder

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//http://www.bouncycastle.org/
//MIT X11 License
using System;
using System.IO;

namespace Org.BouncyCastle.Utilities.Encoders
{
public class Base64Encoder

{
protected readonly byte[] encodingTable =
{
(byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',
(byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',
(byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U',
(byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',
(byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',
(byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',
(byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u',
(byte)'v',
(byte)'w', (byte)'x', (byte)'y', (byte)'z',
(byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6',
(byte)'7', (byte)'8', (byte)'9',
(byte)'+', (byte)'/'
};

protected byte padding = (byte)'=';

/*
* set up the decoding table.
*/
protected readonly byte[] decodingTable = new byte[128];

protected void InitialiseDecodingTable()
{
for (int i = 0; i < encodingTable.Length; i++) { decodingTable[encodingTable[i]] = (byte)i; } } public Base64Encoder() { InitialiseDecodingTable(); } /** * encode the input data producing a base 64 output stream. * * @return the number of bytes produced. */ public int Encode( byte[] data, int off, int length, Stream outStream) { int modulus = length % 3; int dataLength = (length - modulus); int a1, a2, a3; for (int i = off; i < off + dataLength; i += 3) { a1 = data[i] & 0xff; a2 = data[i + 1] & 0xff; a3 = data[i + 2] & 0xff; outStream.WriteByte(encodingTable[(int) ((uint) a1 >> 2) & 0x3f]);
outStream.WriteByte(encodingTable[((a1 << 4) | (int) ((uint) a2 >> 4)) & 0x3f]);
outStream.WriteByte(encodingTable[((a2 << 2) | (int) ((uint) a3 >> 6)) & 0x3f]);
outStream.WriteByte(encodingTable[a3 & 0x3f]);
}

/*
* process the tail end.
*/
int b1, b2, b3;
int d1, d2;

switch (modulus)
{
case 0: /* nothing left to do */
break;
case 1:
d1 = data[off + dataLength] & 0xff;
b1 = (d1 >> 2) & 0x3f;
b2 = (d1 << 4) & 0x3f; outStream.WriteByte(encodingTable[b1]); outStream.WriteByte(encodingTable[b2]); outStream.WriteByte(padding); outStream.WriteByte(padding); break; case 2: d1 = data[off + dataLength] & 0xff; d2 = data[off + dataLength + 1] & 0xff; b1 = (d1 >> 2) & 0x3f;
b2 = ((d1 << 4) | (d2 >> 4)) & 0x3f;
b3 = (d2 << 2) & 0x3f; outStream.WriteByte(encodingTable[b1]); outStream.WriteByte(encodingTable[b2]); outStream.WriteByte(encodingTable[b3]); outStream.WriteByte(padding); break; } return (dataLength / 3) * 4 + ((modulus == 0) ? 0 : 4); } private bool ignore( char c) { return (c == ' ' || c ==' ' || c == ' ' || c == ' '); } /** * decode the base 64 encoded byte data writing it to the given output stream, * whitespace characters will be ignored. * * @return the number of bytes produced. */ public int Decode( byte[] data, int off, int length, Stream outStream) { byte b1, b2, b3, b4; int outLen = 0; int end = off + length; while (end > off)
{
if (!ignore((char)data[end – 1]))
{
break;
}

end–;
}

int i = off;
int finish = end – 4;

i = nextI(data, i, finish);

while (i < finish) { b1 = decodingTable[data[i++]]; i = nextI(data, i, finish); b2 = decodingTable[data[i++]]; i = nextI(data, i, finish); b3 = decodingTable[data[i++]]; i = nextI(data, i, finish); b4 = decodingTable[data[i++]]; outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
outStream.WriteByte((byte)((b3 << 6) | b4)); outLen += 3; i = nextI(data, i, finish); } outLen += decodeLastBlock(outStream, (char)data[end - 4], (char)data[end - 3], (char)data[end - 2], (char)data[end - 1]); return outLen; } private int nextI( byte[] data, int i, int finish) { while ((i < finish) && ignore((char)data[i])) { i++; } return i; } /** * decode the base 64 encoded string data writing it to the given output stream, * whitespace characters will be ignored. * * @return the number of bytes produced. */ public int DecodeString( string data, Stream outStream) { // Platform Implementation // byte[] bytes = Convert.FromBase64String(data); // outStream.Write(bytes, 0, bytes.Length); // return bytes.Length; byte b1, b2, b3, b4; int length = 0; int end = data.Length; while (end > 0)
{
if (!ignore(data[end – 1]))
{
break;
}

end–;
}

int i = 0;
int finish = end – 4;

i = nextI(data, i, finish);

while (i < finish) { b1 = decodingTable[data[i++]]; i = nextI(data, i, finish); b2 = decodingTable[data[i++]]; i = nextI(data, i, finish); b3 = decodingTable[data[i++]]; i = nextI(data, i, finish); b4 = decodingTable[data[i++]]; outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
outStream.WriteByte((byte)((b3 << 6) | b4)); length += 3; i = nextI(data, i, finish); } length += decodeLastBlock(outStream, data[end - 4], data[end - 3], data[end - 2], data[end - 1]); return length; } private int decodeLastBlock( Stream outStream, char c1, char c2, char c3, char c4) { if (c3 == padding) { byte b1 = decodingTable[c1]; byte b2 = decodingTable[c2]; outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));

return 1;
}

if (c4 == padding)
{
byte b1 = decodingTable[c1];
byte b2 = decodingTable[c2];
byte b3 = decodingTable[c3];

outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));

return 2;
}

{
byte b1 = decodingTable[c1];
byte b2 = decodingTable[c2];
byte b3 = decodingTable[c3];
byte b4 = decodingTable[c4];

outStream.WriteByte((byte)((b1 << 2) | (b2 >> 4)));
outStream.WriteByte((byte)((b2 << 4) | (b3 >> 2)));
outStream.WriteByte((byte)((b3 << 6) | b4)); return 3; } } private int nextI(string data, int i, int finish) { while ((i < finish) && ignore(data[i])) { i++; } return i; } } } [/csharp]