package org.bouncycastle.util.encoders;import java.io.IOException;import java.io.OutputStream;public class Base64Encoder    implements Encoder{    protected final 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 final 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,        OutputStream    out)         throws IOException    {        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;            out.write(encodingTable[(a1 >>> 2) & 0x3f]);            out.write(encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f]);            out.write(encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f]);            out.write(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;            out.write(encodingTable[b1]);            out.write(encodingTable[b2]);            out.write(padding);            out.write(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;            out.write(encodingTable[b1]);            out.write(encodingTable[b2]);            out.write(encodingTable[b3]);            out.write(padding);            break;        }        return (dataLength / 3) * 4 + ((modulus == 0) ? 0 : 4);    }    private boolean ignore(        char    c)    {        return (c == '\n' || c =='\r' || c == '\t' || 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,        OutputStream    out)        throws IOException    {        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++]];            out.write((b1 << 2) | (b2 >> 4));            out.write((b2 << 4) | (b3 >> 2));            out.write((b3 << 6) | b4);                        outLen += 3;                        i = nextI(data, i, finish);        }        outLen += decodeLastBlock(out, (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 decode(        String          data,        OutputStream    out)        throws IOException    {        byte    b1, b2, b3, b4;        int     length = 0;                int     end = data.length();                while (end > 0)        {            if (!ignore(data.charAt(end - 1)))            {                break;            }                        end--;        }                int  i = 0;        int  finish = end - 4;                i = nextI(data, i, finish);                while (i < finish)        {            b1 = decodingTable[data.charAt(i++)];                        i = nextI(data, i, finish);                        b2 = decodingTable[data.charAt(i++)];                        i = nextI(data, i, finish);                        b3 = decodingTable[data.charAt(i++)];                        i = nextI(data, i, finish);                        b4 = decodingTable[data.charAt(i++)];            out.write((b1 << 2) | (b2 >> 4));            out.write((b2 << 4) | (b3 >> 2));            out.write((b3 << 6) | b4);                        length += 3;                        i = nextI(data, i, finish);        }        length += decodeLastBlock(out, data.charAt(end - 4), data.charAt(end - 3), data.charAt(end - 2), data.charAt(end - 1));        return length;    }    private int decodeLastBlock(OutputStream out, char c1, char c2, char c3, char c4)         throws IOException    {        byte    b1, b2, b3, b4;                if (c3 == padding)        {            b1 = decodingTable[c1];            b2 = decodingTable[c2];            out.write((b1 << 2) | (b2 >> 4));                        return 1;        }        else if (c4 == padding)        {            b1 = decodingTable[c1];            b2 = decodingTable[c2];            b3 = decodingTable[c3];            out.write((b1 << 2) | (b2 >> 4));            out.write((b2 << 4) | (b3 >> 2));                        return 2;        }        else        {            b1 = decodingTable[c1];            b2 = decodingTable[c2];            b3 = decodingTable[c3];            b4 = decodingTable[c4];            out.write((b1 << 2) | (b2 >> 4));            out.write((b2 << 4) | (b3 >> 2));            out.write((b3 << 6) | b4);                        return 3;        }     }    private int nextI(String data, int i, int finish)    {        while ((i < finish) && ignore(data.charAt(i)))        {            i++;        }        return i;    }}