package org.bouncycastle.util.encoders;

public class Base64
{
        private static 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)'/'
                };

        /**
         * encode the input data producong a base 64 encoded byte array.
         *
         * @return a byte array containing the base 64 encoded data.
         */
        public static byte[] encode(
                byte[]  data)
        {
                byte[]  bytes;
                
                int modulus = data.length % 3;
                if (modulus == 0)
                {
                        bytes = new byte[4 * data.length / 3];
                }
                else
                {
                        bytes = new byte[4 * ((data.length / 3) + 1)];
                }

        int dataLength = (data.length - modulus);
                intintint2, a3;
                for (intint= 0, j = 0; i < dataLength; i += 3, j += 4)
                {
                        a1 = data[i] & 0xff;
                        a2 = data[i + 1] & 0xff;
                        a3 = data[i + 2] & 0xff;

                        bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
                        bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
                        bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
                        bytes[j + 3] = encodingTable[a3 & 0x3f];
                }

                /*
                 * process the tail end.
                 */
                intintint1, b2, b3;
                intint  d1, d2;

                switch (modulus)
                {
                case 0:         /* nothing left to do */
                        break;
                case 1:
                        d1 = data[data.length - 1] & 0xff;
                        b1 = (d1 >>> 2) & 0x3f;
                        b2 = (d1 << 4) & 0x3f;

                        bytes[bytes.length - 4] = encodingTable[b1];
                        bytes[bytes.length - 3] = encodingTable[b2];
                        bytes[bytes.length - 2] = (byte)'=';
                        bytes[bytes.length - 1] = (byte)'=';
                        break;
                case 2:
                        d1 = data[data.length - 2] & 0xff;
                        d2 = data[data.length - 1] & 0xff;

                        b1 = (d1 >>> 2) & 0x3f;
                        b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
                        b3 = (d2 << 2) & 0x3f;

                        bytes[bytes.length - 4] = encodingTable[b1];
                        bytes[bytes.length - 3] = encodingTable[b2];
                        bytes[bytes.length - 2] = encodingTable[b3];
                        bytes[bytes.length - 1] = (byte)'=';
                        break;
                }

                return bytes;
        }

        /*
         * set up the decoding table.
         */
        private static final byte[] decodingTable;

        static
        {
                decodingTable = new byte[128];

                for (int i = 'A'; i <= 'Z'; i++)
                {
                        decodingTable[i] = (byte)(i - 'A');
                }

                for (int i = 'a'; i <= 'z'; i++)
                {
                        decodingTable[i] = (byte)(i - 'a' + 26);
                }

                for (int i = '0'; i <= '9'; i++)
                {
                        decodingTable[i] = (byte)(i - '0' + 52);
                }

                decodingTable['+'] = 62;
                decodingTable['/'] = 63;
        }

        /**
         * decode the base 64 encoded input data.
         *
         * @return a byte array representing the decoded data.
         */
        public static byte[] decode(
                byte[]  data)
        {
                byte[]  bytes;
                bytebytebytebyteb3, b4;

                if (data[data.length - 2] == '=')
                {
                        bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
                }
                else if (data[data.length - 1] == '=')
                {
                        bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
                }
                else
                {
                        bytes = new byte[((data.length / 4) * 3)];
                }

                for (intint= 0, j = 0; i < data.length - 4; i += 4, j += 3)
                {
                        b1 = decodingTable[data[i]];
                        b2 = decodingTable[data[i + 1]];
                        b3 = decodingTable[data[i + 2]];
                        b4 = decodingTable[data[i + 3]];

                        bytes[j] = (byte)((b1 << 2) | (b2 >> 4));
                        bytes[j + 1] = (byte)((b2 << 4) | (b3 >> 2));
                        bytes[j + 2] = (byte)((b3 << 6) | b4);
                }

                if (data[data.length - 2] == '=')
                {
                        b1 = decodingTable[data[data.length - 4]];
                        b2 = decodingTable[data[data.length - 3]];

                        bytes[bytes.length - 1] = (byte)((b1 << 2) | (b2 >> 4));
                }
                else if (data[data.length - 1] == '=')
                {
                        b1 = decodingTable[data[data.length - 4]];
                        b2 = decodingTable[data[data.length - 3]];
                        b3 = decodingTable[data[data.length - 2]];

                        bytes[bytes.length - 2] = (byte)((b1 << 2) | (b2 >> 4));
                        bytes[bytes.length - 1] = (byte)((b2 << 4) | (b3 >> 2));
                }
                else
                {
                        b1 = decodingTable[data[data.length - 4]];
                        b2 = decodingTable[data[data.length - 3]];
                        b3 = decodingTable[data[data.length - 2]];
                        b4 = decodingTable[data[data.length - 1]];

                        bytes[bytes.length - 3] = (byte)((b1 << 2) | (b2 >> 4));
                        bytes[bytes.length - 2] = (byte)((b2 << 4) | (b3 >> 2));
                        bytes[bytes.length - 1] = (byte)((b3 << 6) | b4);
                }

                return bytes;
        }

        /**
         * decode the base 64 encoded String data.
         *
         * @return a byte array representing the decoded data.
         */
        public static byte[] decode(
                String  data)
        {
                byte[]  bytes;
                bytebytebytebyteb3, b4;

                if (data.charAt(data.length() - 2) == '=')
                {
                        bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
                }
                else if (data.charAt(data.length() - 1) == '=')
                {
                        bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
                }
                else
                {
                        bytes = new byte[((data.length() / 4) * 3)];
                }

                for (intint= 0, j = 0; i < data.length() - 4; i += 4, j += 3)
                {
                        b1 = decodingTable[data.charAt(i)];
                        b2 = decodingTable[data.charAt(i + 1)];
                        b3 = decodingTable[data.charAt(i + 2)];
                        b4 = decodingTable[data.charAt(i + 3)];

                        bytes[j] = (byte)((b1 << 2) | (b2 >> 4));
                        bytes[j + 1] = (byte)((b2 << 4) | (b3 >> 2));
                        bytes[j + 2] = (byte)((b3 << 6) | b4);
                }

                if (data.charAt(data.length() - 2) == '=')
                {
                        b1 = decodingTable[data.charAt(data.length() - 4)];
                        b2 = decodingTable[data.charAt(data.length() - 3)];

                        bytes[bytes.length - 1] = (byte)((b1 << 2) | (b2 >> 4));
                }
                else if (data.charAt(data.length() - 1) == '=')
                {
                        b1 = decodingTable[data.charAt(data.length() - 4)];
                        b2 = decodingTable[data.charAt(data.length() - 3)];
                        b3 = decodingTable[data.charAt(data.length() - 2)];

                        bytes[bytes.length - 2] = (byte)((b1 << 2) | (b2 >> 4));
                        bytes[bytes.length - 1] = (byte)((b2 << 4) | (b3 >> 2));
                }
                else
                {
                        b1 = decodingTable[data.charAt(data.length() - 4)];
                        b2 = decodingTable[data.charAt(data.length() - 3)];
                        b3 = decodingTable[data.charAt(data.length() - 2)];
                        b4 = decodingTable[data.charAt(data.length() - 1)];

                        bytes[bytes.length - 3] = (byte)((b1 << 2) | (b2 >> 4));
                        bytes[bytes.length - 2] = (byte)((b2 << 4) | (b3 >> 2));
                        bytes[bytes.length - 1] = (byte)((b3 << 6) | b4);
                }

                return bytes;
        }
}