/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
//--------------------------------------
// XerialJ
//
// Base64.java
// Since: 2009/02/12 16:53:21
//
// $URL$
// $Author$
//--------------------------------------
package org.xerial.util.io;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;

import org.xerial.core.XerialErrorCode;
import org.xerial.core.XerialException;

/**
 * Provides Base64 encoding and decoding as defined by RFC 2045.
 * 
 * <p>
 * This class implements section <cite>6.8. Base64
 * Content-Transfer-Encoding</cite> from RFC 2045 <cite>Multipurpose Internet
 * Mail Extensions (MIME) Part One: Format of Internet Message Bodies</cite> by
 * Freed and Borenstein.
 * </p>
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045< /a>
 * @author Apache Software Foundation
 * @since 1.0-dev
 * @version $Id: Base64.java 674294 2008-07-06 13:04:05Z sebb $
 */
public class Base64
{
    /**
     * Chunk size per RFC 2045 section 6.8.
     * 
     * <p>
     * The {@value} character limit does not count the trailing CRLF, but counts
     * all other characters, including any equal signs.
     * </p>
     * 
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8<
     *      /a>
     */
    static final int CHUNK_SIZE = 76;

    /**
     * Chunk separator per RFC 2045 section 2.1.
     * 
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1<
     *      /a>
     */
    static final byte[] CHUNK_SEPARATOR = { '\r', '\n' };

    /**
     * This array is a lookup table that translates 6-bit positive integer index
     * values into their "Base64 Alphabet" equivalents as specified in Table 1
     * of RFC 2045.
     * 
     * Thanks to "commons" project in ws.apache.org for this code.
     * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     */
    private static final byte[] intToBase64 = { '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', '+', '/' };

    /**
     * Byte used to pad output.
     */
    private static final byte PAD = '=';

    /**
     * This array is a lookup table that translates unicode characters drawn
     * from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045) into
     * their 6-bit positive integer equivalents. Characters that are not in the
     * Base64 alphabet but fall within the bounds of the array are translated to
     * -1.
     * 
     * Thanks to "commons" project in ws.apache.org for this code.
     * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     */
    private static final byte[] base64ToInt = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1,
            -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
            9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29,
            30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };

    /** Mask used to extract 6 bits, used when encoding */
    private static final int MASK_6BITS = 0x3f;

    /** Mask used to extract 8 bits, used in decoding base64 bytes */
    private static final int MASK_8BITS = 0xff;

    // The static final fields above are used for the original static byte[] methods on Base64.
    // The private member fields below are used with the new streaming approach, which requires
    // some state be preserved between calls of encode() and decode().

    /**
     * Line length for encoding. Not used when decoding. A value of zero or less
     * implies no chunking of the base64 encoded data.
     */
    private final int lineLength;

    /**
     * Line separator for encoding. Not used when decoding. Only used if
     * lineLength > 0.
     */
    private final byte[] lineSeparator;

    /**
     * Convenience variable to help us determine when our buffer is going to run
     * out of room and needs resizing.
     * <code>decodeSize = 3 + lineSeparator.length;</code>
     */
    private final int decodeSize;

    /**
     * Convenience variable to help us determine when our buffer is going to run
     * out of room and needs resizing.
     * <code>encodeSize = 4 + lineSeparator.length;</code>
     */
    private final int encodeSize;

    /**
     * Buffer for streaming.
     */
    private byte[] buf;

    /**
     * Position where next character should be written in the buffer.
     */
    private int pos;

    /**
     * Position where next character should be read from the buffer.
     */
    private int readPos;

    /**
     * Variable tracks how many characters have been written to the current
     * line. Only used when encoding. We use it to make sure each encoded line
     * never goes beyond lineLength (if lineLength > 0).
     */
    private int currentLinePos;

    /**
     * Writes to the buffer only occur after every 3 reads when encoding, an
     * every 4 reads when decoding. This variable helps track that.
     */
    private int modulus;

    /**
     * Boolean flag to indicate the EOF has been reached. Once EOF has been
     * reached, this Base64 object becomes useless, and must be thrown away.
     */
    private boolean eof;

    /**
     * Place holder for the 3 bytes we're dealing with for our base64 logic.
     * Bitwise operations store and extract the base64 encoding or decoding from
     * this variable.
     */
    private int x;

    /**
     * Default constructor: lineLength is 76, and the lineSeparator is CRLF when
     * encoding, and all forms can be decoded.
     */
    public Base64()
    {
        this(CHUNK_SIZE, CHUNK_SEPARATOR);
    }

    /**
     * <p>
     * Consumer can use this constructor to choose a different lineLength when
     * encoding (lineSeparator is still CRLF). All forms of data can be decoded.
     * </p>
     * <p>
     * Note: lineLengths that aren't multiples of 4 will still essentially end
     * up being multiples of 4 in the encoded data.
     * </p>
     * 
     * @param lineLength
     *            each line of encoded data will be at most this long (rounded
     *            up to nearest multiple of 4). If lineLength <= 0, then the
     *            output will not be divided into lines (chunks). Ignored when
     *            decoding.
     */
    public Base64(int lineLength)
    {
        this(lineLength, CHUNK_SEPARATOR);
    }

    /**
     * <p>
     * Consumer can use this constructor to choose a different lineLength and
     * lineSeparator when encoding. All forms of data can be decoded.
     * </p>
     * <p>
     * Note: lineLengths that aren't multiples of 4 will still essentially end
     * up being multiples of 4 in the encoded data.
     * </p>
     * 
     * @param lineLength
     *            Each line of encoded data will be at most this long (rounded
     *            up to nearest multiple of 4). Ignored when decoding. If <= 0,
     *            then output will not be divided into lines (chunks).
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of
     *            bytes. If lineLength <= 0, then the lineSeparator is not used.
     * @throws IllegalArgumentException
     *             The provided lineSeparator included some base64 characters.
     *             That's not going to work!
     */
    public Base64(int lineLength, byte[] lineSeparator)
    {
        this.lineLength = lineLength;
        this.lineSeparator = new byte[lineSeparator.length];
        System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
        if (lineLength > 0)
        {
            this.encodeSize = 4 + lineSeparator.length;
        }
        else
        {
            this.encodeSize = 4;
        }
        this.decodeSize = encodeSize - 1;
        if (containsBase64Byte(lineSeparator))
        {
            String sep;
            try
            {
                sep = new String(lineSeparator, "UTF-8");
            }
            catch (UnsupportedEncodingException uee)
            {
                sep = new String(lineSeparator);
            }
            throw new IllegalArgumentException("lineSeperator must not contain base64 characters: [" + sep + "]");
        }
    }

    /**
     * Returns true if this Base64 object has buffered data for reading.
     * 
     * @return true if there is Base64 object still available for reading.
     */
    boolean hasData()
    {
        return buf != null;
    }

    /**
     * Returns the amount of buffered data available for reading.
     * 
     * @return The amount of buffered data available for reading.
     */
    int avail()
    {
        return buf != null ? pos - readPos : 0;
    }

    /** Doubles our buffer. */
    private void resizeBuf()
    {
        if (buf == null)
        {
            buf = new byte[8192];
            pos = 0;
            readPos = 0;
        }
        else
        {
            byte[] b = new byte[buf.length * 2];
            System.arraycopy(buf, 0, b, 0, buf.length);
            buf = b;
        }
    }

    /**
     * Extracts buffered data into the provided byte[] array, starting at
     * position bPos, up to a maximum of bAvail bytes. Returns how many bytes
     * were actually extracted.
     * 
     * @param b
     *            byte[] array to extract the buffered data into.
     * @param bPos
     *            position in byte[] array to start extraction at.
     * @param bAvail
     *            amount of bytes we're allowed to extract. We may extract fewer
     *            (if fewer are available).
     * @return The number of bytes successfully extracted into the provided
     *         byte[] array.
     */
    int readResults(byte[] b, int bPos, int bAvail)
    {
        if (buf != null)
        {
            int len = Math.min(avail(), bAvail);
            if (buf != b)
            {
                System.arraycopy(buf, readPos, b, bPos, len);
                readPos += len;
                if (readPos >= pos)
                {
                    buf = null;
                }
            }
            else
            {
                // Re-using the original consumer's output array is only
                // allowed for one round.
                buf = null;
            }
            return len;
        }
        else
        {
            return eof ? -1 : 0;
        }
    }

    /**
     * Small optimization where we try to buffer directly to the consumer's
     * output array for one round (if consumer calls this method first!) instead
     * of starting our own buffer.
     * 
     * @param out
     *            byte[] array to buffer directly to.
     * @param outPos
     *            Position to start buffering into.
     * @param outAvail
     *            Amount of bytes available for direct buffering.
     */
    void setInitialBuffer(byte[] out, int outPos, int outAvail)
    {
        // We can re-use consumer's original output array under
        // special circumstances, saving on some System.arraycopy().
        if (out != null && out.length == outAvail)
        {
            buf = out;
            pos = outPos;
            readPos = outPos;
        }
    }

    /**
     * <p>
     * Encodes all of the provided data, starting at inPos, for inAvail bytes.
     * Must be called at least twice: once with the data to encode, and once
     * with inAvail set to "-1" to alert encoder that EOF has been reached, so
     * flush last remaining bytes (if not multiple of 3).
     * </p>
     * <p>
     * Thanks to "commons" project in ws.apache.org for the bitwise operations,
     * and general approach.
     * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     * </p>
     * 
     * @param in
     *            byte[] array of binary data to base64 encode.
     * @param inPos
     *            Position to start reading data from.
     * @param inAvail
     *            Amount of bytes available from input for encoding.
     */
    void encode(byte[] in, int inPos, int inAvail)
    {
        if (eof)
        {
            return;
        }

        // inAvail < 0 is how we're informed of EOF in the underlying data we're
        // encoding.
        if (inAvail < 0)
        {
            eof = true;
            if (buf == null || buf.length - pos < encodeSize)
            {
                resizeBuf();
            }
            switch (modulus)
            {
            case 1:
                buf[pos++] = intToBase64[(x >> 2) & MASK_6BITS];
                buf[pos++] = intToBase64[(x << 4) & MASK_6BITS];
                buf[pos++] = PAD;
                buf[pos++] = PAD;
                break;

            case 2:
                buf[pos++] = intToBase64[(x >> 10) & MASK_6BITS];
                buf[pos++] = intToBase64[(x >> 4) & MASK_6BITS];
                buf[pos++] = intToBase64[(x << 2) & MASK_6BITS];
                buf[pos++] = PAD;
                break;
            }
            if (lineLength > 0)
            {
                System.arraycopy(lineSeparator, 0, buf, pos, lineSeparator.length);
                pos += lineSeparator.length;
            }
        }
        else
        {
            for (int i = 0; i < inAvail; i++)
            {
                if (buf == null || buf.length - pos < encodeSize)
                {
                    resizeBuf();
                }
                modulus = (++modulus) % 3;
                int b = in[inPos++];
                if (b < 0)
                {
                    b += 256;
                }
                x = (x << 8) + b;
                if (0 == modulus)
                {
                    buf[pos++] = intToBase64[(x >> 18) & MASK_6BITS];
                    buf[pos++] = intToBase64[(x >> 12) & MASK_6BITS];
                    buf[pos++] = intToBase64[(x >> 6) & MASK_6BITS];
                    buf[pos++] = intToBase64[x & MASK_6BITS];
                    currentLinePos += 4;
                    if (lineLength > 0 && lineLength <= currentLinePos)
                    {
                        System.arraycopy(lineSeparator, 0, buf, pos, lineSeparator.length);
                        pos += lineSeparator.length;
                        currentLinePos = 0;
                    }
                }
            }
        }
    }

    /**
     * <p>
     * Decodes all of the provided data, starting at inPos, for inAvail bytes.
     * Should be called at least twice: once with the data to decode, and once
     * with inAvail set to "-1" to alert decoder that EOF has been reached. The
     * "-1" call is not necessary when decoding, but it doesn't hurt, either.
     * </p>
     * <p>
     * Ignores all non-base64 characters. This is how chunked (e.g. 76
     * character) data is handled, since CR and LF are silently ignored, but has
     * implications for other bytes, too. This method subscribes to the
     * garbage-in, garbage-out philosophy: it will not check the provided data
     * for validity.
     * </p>
     * <p>
     * Thanks to "commons" project in ws.apache.org for the bitwise operations,
     * and general approach.
     * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
     * </p>
     * 
     * @param in
     *            byte[] array of ascii data to base64 decode.
     * @param inPos
     *            Position to start reading data from.
     * @param inAvail
     *            Amount of bytes available from input for encoding.
     */
    void decode(byte[] in, int inPos, int inAvail)
    {
        if (eof)
        {
            return;
        }
        if (inAvail < 0)
        {
            eof = true;
        }
        for (int i = 0; i < inAvail; i++)
        {
            if (buf == null || buf.length - pos < decodeSize)
            {
                resizeBuf();
            }
            byte b = in[inPos++];
            if (b == PAD)
            {
                x = x << 6;
                switch (modulus)
                {
                case 2:
                    x = x << 6;
                    buf[pos++] = (byte) ((x >> 16) & MASK_8BITS);
                    break;
                case 3:
                    buf[pos++] = (byte) ((x >> 16) & MASK_8BITS);
                    buf[pos++] = (byte) ((x >> 8) & MASK_8BITS);
                    break;
                }
                // WE'RE DONE!!!!
                eof = true;
                return;
            }
            else
            {
                if (b >= 0 && b < base64ToInt.length)
                {
                    int result = base64ToInt[b];
                    if (result >= 0)
                    {
                        modulus = (++modulus) % 4;
                        x = (x << 6) + result;
                        if (modulus == 0)
                        {
                            buf[pos++] = (byte) ((x >> 16) & MASK_8BITS);
                            buf[pos++] = (byte) ((x >> 8) & MASK_8BITS);
                            buf[pos++] = (byte) (x & MASK_8BITS);
                        }
                    }
                }
            }
        }
    }

    /**
     * Returns whether or not the <code>octet</code> is in the base 64 alphabet.
     * 
     * @param octet
     *            The value to test
     * @return <code>true</code> if the value is defined in the the base 64
     *         alphabet, <code>false</code> otherwise.
     */
    public static boolean isBase64(byte octet)
    {
        return octet == PAD || (octet >= 0 && octet < base64ToInt.length && base64ToInt[octet] != -1);
    }

    /**
     * Tests a given byte array to see if it contains only valid characters
     * within the Base64 alphabet. Currently the method treats whitespace as
     * valid.
     * 
     * @param arrayOctet
     *            byte array to test
     * @return <code>true</code> if all bytes are valid characters in the Base64
     *         alphabet or if the byte array is empty; false, otherwise
     */
    public static boolean isArrayByteBase64(byte[] arrayOctet)
    {
        for (int i = 0; i < arrayOctet.length; i++)
        {
            if (!isBase64(arrayOctet[i]) && !isWhiteSpace(arrayOctet[i]))
            {
                return false;
            }
        }
        return true;
    }

    /*
     * Tests a given byte array to see if it contains only valid characters within the Base64 alphabet.
     * 
     * @param arrayOctet
     *            byte array to test
     * @return <code>true</code> if any byte is a valid character in the Base64 alphabet; false herwise
     */
    private static boolean containsBase64Byte(byte[] arrayOctet)
    {
        for (int i = 0; i < arrayOctet.length; i++)
        {
            if (isBase64(arrayOctet[i]))
            {
                return true;
            }
        }
        return false;
    }

    /**
     * Encodes binary data using the base64 algorithm but does not chunk the
     * output.
     * 
     * @param binaryData
     *            binary data to encode
     * @return Base64 characters
     */
    public static byte[] encodeBase64(byte[] binaryData)
    {
        return encodeBase64(binaryData, false);
    }

    /**
     * Encodes binary data using the base64 algorithm and chunks the encoded
     * output into 76 character blocks
     * 
     * @param binaryData
     *            binary data to encode
     * @return Base64 characters chunked in 76 character blocks
     */
    public static byte[] encodeBase64Chunked(byte[] binaryData)
    {
        return encodeBase64(binaryData, true);
    }

    /**
     * Decodes an Object using the base64 algorithm. This method is provided in
     * order to satisfy the requirements of the Decoder interface, and will
     * throw a DecoderException if the supplied object is not of type byte[].
     * 
     * @param pObject
     *            Object to decode
     * @return An object (of type byte[]) containing the binary data which
     *         corresponds to the byte[] supplied.
     * @throws DecoderException
     *             if the parameter supplied is not of type byte[]
     */
    public Object decode(Object pObject) throws XerialException
    {
        if (!(pObject instanceof byte[]))
        {
            throw new XerialException(XerialErrorCode.DECODE_ERROR,
                    "Parameter supplied to Base64 decode is not a byte[]");
        }
        return decode((byte[]) pObject);
    }

    /**
     * Decodes a byte[] containing containing characters in the Base64 alphabet.
     * 
     * @param pArray
     *            A byte array containing Base64 character data
     * @return a byte array containing binary data
     */
    public byte[] decode(byte[] pArray)
    {
        return decodeBase64(pArray);
    }

    /**
     * Encodes binary data using the base64 algorithm, optionally chunking the
     * output into 76 character blocks.
     * 
     * @param binaryData
     *            Array containing binary data to encode.
     * @param isChunked
     *            if <code>true</code> this encoder will chunk the base64 output
     *            into 76 character blocks
     * @return Base64-encoded data.
     * @throws IllegalArgumentException
     *             Thrown when the input array needs an output array bigger than
     *             {@link Integer#MAX_VALUE}
     */
    public static byte[] encodeBase64(byte[] binaryData, boolean isChunked)
    {
        if (binaryData == null || binaryData.length == 0)
        {
            return binaryData;
        }
        Base64 b64 = isChunked ? new Base64() : new Base64(0);

        long len = (binaryData.length * 4) / 3;
        long mod = len % 4;
        if (mod != 0)
        {
            len += 4 - mod;
        }
        if (isChunked)
        {
            len += (1 + (len / CHUNK_SIZE)) * CHUNK_SEPARATOR.length;
        }

        if (len > Integer.MAX_VALUE)
        {
            throw new IllegalArgumentException(
                    "Input array too big, output array would be bigger than Integer.MAX_VALUE=" + Integer.MAX_VALUE);
        }
        byte[] buf = new byte[(int) len];
        b64.setInitialBuffer(buf, 0, buf.length);
        b64.encode(binaryData, 0, binaryData.length);
        b64.encode(binaryData, 0, -1); // Notify encoder of EOF.

        // Encoder might have resized, even though it was unnecessary.
        if (b64.buf != buf)
        {
            b64.readResults(buf, 0, buf.length);
        }
        return buf;
    }

    /**
     * Decodes Base64 data into octets
     * 
     * @param base64Data
     *            Byte array containing Base64 data
     * @return Array containing decoded data.
     */
    public static byte[] decodeBase64(byte[] base64Data)
    {
        if (base64Data == null || base64Data.length == 0)
        {
            return base64Data;
        }
        Base64 b64 = new Base64();

        long len = (base64Data.length * 3) / 4;
        byte[] buf = new byte[(int) len];
        b64.setInitialBuffer(buf, 0, buf.length);
        b64.decode(base64Data, 0, base64Data.length);
        b64.decode(base64Data, 0, -1); // Notify decoder of EOF.

        // We have no idea what the line-length was, so we
        // cannot know how much of our array wasn't used.
        byte[] result = new byte[b64.pos];
        b64.readResults(result, 0, result.length);
        return result;
    }

    /**
     * Discards any whitespace from a base-64 encoded block.
     * 
     * @param data
     *            The base-64 encoded data to discard the whitespace from.
     * @return The data, less whitespace (see RFC 2045).
     * @deprecated This method is no longer needed
     */
    static byte[] discardWhitespace(byte[] data)
    {
        byte groomedData[] = new byte[data.length];
        int bytesCopied = 0;

        for (int i = 0; i < data.length; i++)
        {
            switch (data[i])
            {
            case ' ':
            case '\n':
            case '\r':
            case '\t':
                break;
            default:
                groomedData[bytesCopied++] = data[i];
            }
        }

        byte packedData[] = new byte[bytesCopied];

        System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

        return packedData;
    }

    /**
     * Check if a byte value is whitespace or not.
     * 
     * @param byteToCheck
     *            the byte to check
     * @return true if byte is whitespace, false otherwise
     */
    private static boolean isWhiteSpace(byte byteToCheck)
    {
        switch (byteToCheck)
        {
        case ' ':
        case '\n':
        case '\r':
        case '\t':
            return true;
        default:
            return false;
        }
    }

    /**
     * Discards any characters outside of the base64 alphabet, per the
     * requirements on page 25 of RFC 2045 - "Any characters outside of the
     * base64 alphabet are to be ignored in base64 encoded data."
     * 
     * @param data
     *            The base-64 encoded data to groom
     * @return The data, less non-base64 characters (see RFC 2045).
     */
    static byte[] discardNonBase64(byte[] data)
    {
        byte groomedData[] = new byte[data.length];
        int bytesCopied = 0;

        for (int i = 0; i < data.length; i++)
        {
            if (isBase64(data[i]))
            {
                groomedData[bytesCopied++] = data[i];
            }
        }

        byte packedData[] = new byte[bytesCopied];

        System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

        return packedData;
    }

    // Implementation of the Encoder Interface

    /**
     * Encodes an Object using the base64 algorithm. This method is provided in
     * order to satisfy the requirements of the Encoder interface, and will
     * throw an EncoderException if the supplied object is not of type byte[].
     * 
     * @param pObject
     *            Object to encode
     * @return An object (of type byte[]) containing the base64 encoded data
     *         which corresponds to the byte[] supplied.
     * @throws EncoderException
     *             if the parameter supplied is not of type byte[]
     */
    public Object encode(Object pObject) throws XerialException
    {
        if (!(pObject instanceof byte[]))
        {
            throw new XerialException(XerialErrorCode.ENCODE_ERROR,
                    "Parameter supplied to Base64 encode is not a byte[]");
        }
        return encode((byte[]) pObject);
    }

    /**
     * Encodes a byte[] containing binary data, into a byte[] containing
     * characters in the Base64 alphabet.
     * 
     * @param pArray
     *            a byte array containing binary data
     * @return A byte array containing only Base64 character data
     */
    public byte[] encode(byte[] pArray)
    {
        return encodeBase64(pArray, false);
    }

    // Implementation of integer encoding used for crypto
    /**
     * Decode a byte64-encoded integer according to crypto standards such as
     * W3C's XML-Signature
     * 
     * @param pArray
     *            a byte array containing base64 character data
     * @return A BigInteger
     */
    public static BigInteger decodeInteger(byte[] pArray)
    {
        return new BigInteger(1, decodeBase64(pArray));
    }

    /**
     * Encode to a byte64-encoded integer according to crypto standards such as
     * W3C's XML-Signature
     * 
     * @param bigInt
     *            a BigInteger
     * @return A byte array containing base64 character data
     * @throws NullPointerException
     *             if null is passed in
     */
    public static byte[] encodeInteger(BigInteger bigInt)
    {
        if (bigInt == null)
        {
            throw new NullPointerException("encodeInteger called with null parameter");
        }

        return encodeBase64(toIntegerBytes(bigInt), false);
    }

    /**
     * Returns a byte-array representation of a <code>BigInteger</code> without
     * sign bit.
     * 
     * @param bigInt
     *            <code>BigInteger</code> to be converted
     * @return a byte array representation of the BigInteger parameter
     */
    static byte[] toIntegerBytes(BigInteger bigInt)
    {
        int bitlen = bigInt.bitLength();
        // round bitlen
        bitlen = ((bitlen + 7) >> 3) << 3;
        byte[] bigBytes = bigInt.toByteArray();

        if (((bigInt.bitLength() % 8) != 0) && (((bigInt.bitLength() / 8) + 1) == (bitlen / 8)))
        {
            return bigBytes;
        }

        // set up params for copying everything but sign bit
        int startSrc = 0;
        int len = bigBytes.length;

        // if bigInt is exactly byte-aligned, just skip signbit in copy
        if ((bigInt.bitLength() % 8) == 0)
        {
            startSrc = 1;
            len--;
        }

        int startDst = bitlen / 8 - len; // to pad w/ nulls as per spec
        byte[] resizedBytes = new byte[bitlen / 8];

        System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, len);

        return resizedBytes;
    }
}
