videoalliance/.svn/pristine/22/221a53ebbfaa8dbb93427d21de7362427a2702a5.svn-base

package com.chinacreator.videoalliance.order.util;

import java.io.UnsupportedEncodingException;
import java.util.Arrays;

public class Base64 extends BaseNCodec { 

	/**
	 * BASE32 characters are 6 bits in length. They are formed by taking a block
	 * of 3 octets to form a 24-bit string, which is converted into 4 BASE64
	 * characters.
	 */
	private static final int BITS_PER_ENCODED_BYTE = 6;
	private static final int BYTES_PER_UNENCODED_BLOCK = 3;
	private static final int BYTES_PER_ENCODED_BLOCK = 4;

	/**
	 * Chunk separator per RFC 2045 section 2.1.
	 * 
	 * <p>
	 * N.B. The next major release may break compatibility and make this field
	 * private.
	 * </p>
	 */
	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.
	 */
	private static final byte[] STANDARD_ENCODE_TABLE = { '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', '+', '/' };

	/**
	 * This is a copy of the STANDARD_ENCODE_TABLE above, but with + and /
	 * changed to - and _ to make the encoded Base64 results more URL-SAFE. This
	 * table is only used when the Base64's mode is set to URL-SAFE.
	 */
	private static final byte[] URL_SAFE_ENCODE_TABLE = { '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', '-', '_' };

	/**
	 * 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.
	 * 
	 * Note: '+' and '-' both decode to 62. '/' and '_' both decode to 63. This
	 * means decoder seamlessly handles both URL_SAFE and STANDARD base64. (The
	 * encoder, on the other hand, needs to know ahead of time what to emit).
	 * 
	 */
	private static final byte[] DECODE_TABLE = { -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, 62, -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, 63, -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 };

	/**
	 * Base64 uses 6-bit fields.
	 */
	/** Mask used to extract 6 bits, used when encoding */
	private static final int MASK_6BITS = 0x3f;

	// 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().

	/**
	 * Encode table to use: either STANDARD or URL_SAFE. Note: the DECODE_TABLE
	 * above remains static because it is able to decode both STANDARD and
	 * URL_SAFE streams, but the encodeTable must be a member variable so we can
	 * switch between the two modes.
	 */
	private final byte[] encodeTable;

	// Only one decode table currently; keep for consistency with Base32 code
	private final byte[] decodeTable = DECODE_TABLE;

	/**
	 * 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;

	/**
	 * Creates a Base64 codec used for decoding (all modes) and encoding in
	 * URL-unsafe mode.
	 * <p>
	 * When encoding the line length is 0 (no chunking), and the encoding table
	 * is STANDARD_ENCODE_TABLE.
	 * </p>
	 * 
	 * <p>
	 * When decoding all variants are supported.
	 * </p>
	 */
	public Base64() {
		this(0);
	}

	/**
	 * Creates a Base64 codec used for decoding (all modes) and encoding in the
	 * given URL-safe mode.
	 * <p>
	 * When encoding the line length is 76, the line separator is CRLF, and the
	 * encoding table is STANDARD_ENCODE_TABLE.
	 * </p>
	 * 
	 * <p>
	 * When decoding all variants are supported.
	 * </p>
	 * 
	 * @param urlSafe
	 *            if {@code true}, URL-safe encoding is used. In most cases this
	 *            should be set to {@code false}.
	 * @since 1.4
	 */
	public Base64(final boolean urlSafe) {
		this(MIME_CHUNK_SIZE, CHUNK_SEPARATOR, urlSafe);
	}

	/**
	 * Creates a Base64 codec used for decoding (all modes) and encoding in
	 * URL-unsafe mode.
	 * <p>
	 * When encoding the line length is given in the constructor, the line
	 * separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.
	 * </p>
	 * <p>
	 * Line lengths that aren't multiples of 4 will still essentially end up
	 * being multiples of 4 in the encoded data.
	 * </p>
	 * <p>
	 * When decoding all variants are supported.
	 * </p>
	 * 
	 * @param lineLength
	 *            Each line of encoded data will be at most of the given length
	 *            (rounded down to nearest multiple of 4). If lineLength <= 0,
	 *            then the output will not be divided into lines (chunks).
	 *            Ignored when decoding.
	 */
	public Base64(final int lineLength) {
		this(lineLength, CHUNK_SEPARATOR);
	}

	/**
	 * Creates a Base64 codec used for decoding (all modes) and encoding in
	 * URL-unsafe mode.
	 * <p>
	 * When encoding the line length and line separator are given in the
	 * constructor, and the encoding table is STANDARD_ENCODE_TABLE.
	 * </p>
	 * <p>
	 * Line lengths that aren't multiples of 4 will still essentially end up
	 * being multiples of 4 in the encoded data.
	 * </p>
	 * <p>
	 * When decoding all variants are supported.
	 * </p>
	 * 
	 * @param lineLength
	 *            Each line of encoded data will be at most of the given length
	 *            (rounded down to nearest multiple of 4). If lineLength <= 0,
	 *            then the output will not be divided into lines (chunks).
	 *            Ignored when decoding.
	 * @param lineSeparator
	 *            Each line of encoded data will end with this sequence of
	 *            bytes.
	 * @throws IllegalArgumentException
	 *             Thrown when the provided lineSeparator included some base64
	 *             characters.
	 */
	public Base64(final int lineLength, final byte[] lineSeparator) {
		this(lineLength, lineSeparator, false);
	}

	/**
	 * Creates a Base64 codec used for decoding (all modes) and encoding in
	 * URL-unsafe mode.
	 * <p>
	 * When encoding the line length and line separator are given in the
	 * constructor, and the encoding table is STANDARD_ENCODE_TABLE.
	 * </p>
	 * <p>
	 * Line lengths that aren't multiples of 4 will still essentially end up
	 * being multiples of 4 in the encoded data.
	 * </p>
	 * <p>
	 * When decoding all variants are supported.
	 * </p>
	 * 
	 * @param lineLength
	 *            Each line of encoded data will be at most of the given length
	 *            (rounded down to nearest multiple of 4). If lineLength <= 0,
	 *            then the output will not be divided into lines (chunks).
	 *            Ignored when decoding.
	 * @param lineSeparator
	 *            Each line of encoded data will end with this sequence of
	 *            bytes.
	 * @param urlSafe
	 *            Instead of emitting '+' and '/' we emit '-' and '_'
	 *            respectively. urlSafe is only applied to encode operations.
	 *            Decoding seamlessly handles both modes. <b>Note: no padding is
	 *            added when using the URL-safe alphabet.</b>
	 * @throws IllegalArgumentException
	 *             The provided lineSeparator included some base64 characters.
	 *             That's not going to work!
	 */
	public Base64(final int lineLength, final byte[] lineSeparator, final boolean urlSafe) {
		super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK, lineLength, lineSeparator == null ? 0 : lineSeparator.length);
		// TODO could be simplified if there is no requirement to reject invalid
		// line sep when length <=0
		// @see test case Base64Test.testConstructors()
		if (lineSeparator != null) {
			if (containsAlphabetOrPad(lineSeparator)) {
				try {
					final String sep = new String(lineSeparator, "UTF-8");
					throw new IllegalArgumentException("lineSeparator must not contain base64 characters: [" + sep + "]");
				} catch (UnsupportedEncodingException e) {
					e.printStackTrace();
				}
			}
			if (lineLength > 0) { // null line-sep forces no chunking rather
									// than throwing IAE
				this.encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparator.length;
				this.lineSeparator = new byte[lineSeparator.length];
				System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
			} else {
				this.encodeSize = BYTES_PER_ENCODED_BLOCK;
				this.lineSeparator = null;
			}
		} else {
			this.encodeSize = BYTES_PER_ENCODED_BLOCK;
			this.lineSeparator = null;
		}
		this.decodeSize = this.encodeSize - 1;
		this.encodeTable = urlSafe ? URL_SAFE_ENCODE_TABLE : STANDARD_ENCODE_TABLE;
	}

	/**
	 * <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, to
	 * flush last remaining bytes (if not multiple of 3).
	 * </p>
	 * <p>
	 * <b>Note: no padding is added when encoding using the URL-safe
	 * alphabet.</b>
	 * </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.
	 * @param context
	 *            the context to be used
	 */
	@Override
	void encode(final byte[] in, int inPos, final int inAvail, final Context context) {
		if (context.eof) {
			return;
		}
		// inAvail < 0 is how we're informed of EOF in the underlying data we're
		// encoding.
		if (inAvail < 0) {
			context.eof = true;
			if (0 == context.modulus && lineLength == 0) {
				return; // no leftovers to process and not using chunking
			}
			final byte[] buffer = ensureBufferSize(encodeSize, context);
			final int savedPos = context.pos;
			switch (context.modulus) { // 0-2
			case 0: // nothing to do here
				break;
			case 1: // 8 bits = 6 + 2
				// top 6 bits:
				buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 2) & MASK_6BITS];
				// remaining 2:
				buffer[context.pos++] = encodeTable[(context.ibitWorkArea << 4) & MASK_6BITS];
				// URL-SAFE skips the padding to further reduce size.
				if (encodeTable == STANDARD_ENCODE_TABLE) {
					buffer[context.pos++] = PAD;
					buffer[context.pos++] = PAD;
				}
				break;

			case 2: // 16 bits = 6 + 6 + 4
				buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 10) & MASK_6BITS];
				buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 4) & MASK_6BITS];
				buffer[context.pos++] = encodeTable[(context.ibitWorkArea << 2) & MASK_6BITS];
				// URL-SAFE skips the padding to further reduce size.
				if (encodeTable == STANDARD_ENCODE_TABLE) {
					buffer[context.pos++] = PAD;
				}
				break;
			default:
				throw new IllegalStateException("Impossible modulus " + context.modulus);
			}
			context.currentLinePos += context.pos - savedPos; // keep track of
																// current line
																// position
			// if currentPos == 0 we are at the start of a line, so don't add
			// CRLF
			if (lineLength > 0 && context.currentLinePos > 0) {
				System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
				context.pos += lineSeparator.length;
			}
		} else {
			for (int i = 0; i < inAvail; i++) {
				final byte[] buffer = ensureBufferSize(encodeSize, context);
				context.modulus = (context.modulus + 1) % BYTES_PER_UNENCODED_BLOCK;
				int b = in[inPos++];
				if (b < 0) {
					b += 256;
				}
				context.ibitWorkArea = (context.ibitWorkArea << 8) + b; // BITS_PER_BYTE
				if (0 == context.modulus) { // 3 bytes = 24 bits = 4 * 6 bits to
											// extract
					buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 18) & MASK_6BITS];
					buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 12) & MASK_6BITS];
					buffer[context.pos++] = encodeTable[(context.ibitWorkArea >> 6) & MASK_6BITS];
					buffer[context.pos++] = encodeTable[context.ibitWorkArea & MASK_6BITS];
					context.currentLinePos += BYTES_PER_ENCODED_BLOCK;
					if (lineLength > 0 && lineLength <= context.currentLinePos) {
						System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
						context.pos += lineSeparator.length;
						context.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>
	 * 
	 * @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.
	 * @param context
	 *            the context to be used
	 */
	@Override
	void decode(final byte[] in, int inPos, final int inAvail, final Context context) {
		if (context.eof) {
			return;
		}
		if (inAvail < 0) {
			context.eof = true;
		}
		for (int i = 0; i < inAvail; i++) {
			final byte[] buffer = ensureBufferSize(decodeSize, context);
			final byte b = in[inPos++];
			if (b == PAD) {
				// We're done.
				context.eof = true;
				break;
			} else {
				if (b >= 0 && b < DECODE_TABLE.length) {
					final int result = DECODE_TABLE[b];
					if (result >= 0) {
						context.modulus = (context.modulus + 1) % BYTES_PER_ENCODED_BLOCK;
						context.ibitWorkArea = (context.ibitWorkArea << BITS_PER_ENCODED_BYTE) + result;
						if (context.modulus == 0) {
							buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 16) & MASK_8BITS);
							buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
							buffer[context.pos++] = (byte) (context.ibitWorkArea & MASK_8BITS);
						}
					}
				}
			}
		}

		// Two forms of EOF as far as base64 decoder is concerned: actual
		// EOF (-1) and first time '=' character is encountered in stream.
		// This approach makes the '=' padding characters completely optional.
		if (context.eof && context.modulus != 0) {
			final byte[] buffer = ensureBufferSize(decodeSize, context);

			// We have some spare bits remaining
			// Output all whole multiples of 8 bits and ignore the rest
			switch (context.modulus) {
			// case 0 : // impossible, as excluded above
			case 1: // 6 bits - ignore entirely
				// TODO not currently tested; perhaps it is impossible?
				break;
			case 2: // 12 bits = 8 + 4
				context.ibitWorkArea = context.ibitWorkArea >> 4; // dump the
																	// extra 4
																	// bits
				buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
				break;
			case 3: // 18 bits = 8 + 8 + 2
				context.ibitWorkArea = context.ibitWorkArea >> 2; // dump 2 bits
				buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
				buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
				break;
			default:
				throw new IllegalStateException("Impossible modulus " + context.modulus);
			}
		}
	}


	/**
	 * Encodes binary data using the base64 algorithm but does not chunk the
	 * output.
	 * 
	 * @param binaryData
	 *            binary data to encode
	 * @return byte[] containing Base64 characters in their UTF-8
	 *         representation.
	 */
	public static byte[] encodeBase64(final byte[] binaryData) {
		return encodeBase64(binaryData, false);
	}

	/**
	 * Encodes binary data using the base64 algorithm but does not chunk the
	 * output.
	 * 
	 * NOTE: We changed the behaviour of this method from multi-line chunking
	 * 
	 * @param binaryData
	 *            binary data to encode
	 * @return String containing Base64 characters.
	 * @throws UnsupportedEncodingException 
	 */
	public static String encodeBase64String(final byte[] binaryData) throws UnsupportedEncodingException {
		return new String(encodeBase64(binaryData, false), "UTF-8");
	}

	/**
	 * Encodes binary data using a URL-safe variation of the base64 algorithm
	 * but does not chunk the output. The url-safe variation emits - and _
	 * instead of + and / characters. <b>Note: no padding is added.</b>
	 * 
	 * @param binaryData
	 *            binary data to encode
	 * @return byte[] containing Base64 characters in their UTF-8
	 *         representation.
	 */
	public static byte[] encodeBase64URLSafe(final byte[] binaryData) {
		return encodeBase64(binaryData, false, true);
	}

	/**
	 * Encodes binary data using a URL-safe variation of the base64 algorithm
	 * but does not chunk the output. The url-safe variation emits - and _
	 * instead of + and / characters. <b>Note: no padding is added.</b>
	 * 
	 * @param binaryData
	 *            binary data to encode
	 * @return String containing Base64 characters
	 * @throws UnsupportedEncodingException 
	 */
	public static String encodeBase64URLSafeString(final byte[] binaryData) throws UnsupportedEncodingException {
		return new String(encodeBase64(binaryData, false, true), "UTF-8");
	}

	/**
	 * 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(final byte[] binaryData) {
		return encodeBase64(binaryData, true);
	}

	/**
	 * 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} 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(final byte[] binaryData, final boolean isChunked) {
		return encodeBase64(binaryData, isChunked, false);
	}

	/**
	 * 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} this encoder will chunk the base64 output into
	 *            76 character blocks
	 * @param urlSafe
	 *            if {@code true} this encoder will emit - and _ instead of the
	 *            usual + and / characters. <b>Note: no padding is added when
	 *            encoding using the URL-safe alphabet.</b>
	 * @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(final byte[] binaryData, final boolean isChunked, final boolean urlSafe) {
		return encodeBase64(binaryData, isChunked, urlSafe, Integer.MAX_VALUE);
	}

	/**
	 * 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} this encoder will chunk the base64 output into
	 *            76 character blocks
	 * @param urlSafe
	 *            if {@code true} this encoder will emit - and _ instead of the
	 *            usual + and / characters. <b>Note: no padding is added when
	 *            encoding using the URL-safe alphabet.</b>
	 * @param maxResultSize
	 *            The maximum result size to accept.
	 * @return Base64-encoded data.
	 * @throws IllegalArgumentException
	 *             Thrown when the input array needs an output array bigger than
	 *             maxResultSize
	 */
	public static byte[] encodeBase64(final byte[] binaryData, final boolean isChunked, final boolean urlSafe, final int maxResultSize) {
		if (binaryData == null || binaryData.length == 0) {
			return binaryData;
		}

		// Create this so can use the super-class method
		// Also ensures that the same roundings are performed by the ctor and
		// the code
		final Base64 b64 = isChunked ? new Base64(urlSafe) : new Base64(0, CHUNK_SEPARATOR, urlSafe);
		final long len = b64.getEncodedLength(binaryData);
		if (len > maxResultSize) {
			throw new IllegalArgumentException("Input array too big, the output array would be bigger (" + len + ") than the specified maximum size of " + maxResultSize);
		}

		return b64.encode(binaryData);
	}

	/**
	 * Decodes a Base64 String into octets
	 * 
	 * @param base64String
	 *            String containing Base64 data
	 * @return Array containing decoded data.
	 * @throws UnsupportedEncodingException
	 */
	public static byte[] decodeBase64(final String base64String) throws UnsupportedEncodingException {
		return new Base64().decode(base64String);
	}

	/**
	 * Decodes Base64 data into octets
	 * 
	 * @param base64Data
	 *            Byte array containing Base64 data
	 * @return Array containing decoded data.
	 */
	public static byte[] decodeBase64(final byte[] base64Data) {
		return new Base64().decode(base64Data);
	}


	/**
	 * Returns whether or not the <code>octet</code> is in the Base64 alphabet.
	 * 
	 * @param octet
	 *            The value to test
	 * @return {@code true} if the value is defined in the the Base64 alphabet
	 *         {@code false} otherwise.
	 */
	@Override
	protected boolean isInAlphabet(final byte octet) {
		return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
	}
}

abstract class BaseNCodec {
	
    static class Context {

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

        /**
         * Place holder for the bytes we're dealing with for our based logic.
         * Bitwise operations store and extract the encoding or decoding from this variable.
         */
        long lbitWorkArea;

        /**
         * Buffer for streaming.
         */
        byte[] buffer;

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

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

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

        /**
         * 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).
         */
        int currentLinePos;

        /**
         * Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding. This
         * variable helps track that.
         */
        int modulus;

        Context() {
        }

        /**
         * Returns a String useful for debugging (especially within a debugger.)
         *
         * @return a String useful for debugging.
         */
        @SuppressWarnings("boxing") // OK to ignore boxing here
        @Override
        public String toString() {
            return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " +
                    "modulus=%s, pos=%s, readPos=%s]", this.getClass().getSimpleName(), Arrays.toString(buffer),
                    currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
        }
    }

    /**
     * EOF
     */
    static final int EOF = -1;

    /**
     *  MIME chunk size per RFC 2045 section 6.8.
     */
    public static final int MIME_CHUNK_SIZE = 76;

    /**
     * PEM chunk size per RFC 1421 section 4.3.2.4.
     */
    public static final int PEM_CHUNK_SIZE = 64;

    private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;

    /**
     * Defines the default buffer size - currently {@value}
     * - must be large enough for at least one encoded block+separator
     */
    private static final int DEFAULT_BUFFER_SIZE = 8192;

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

    /**
     * Byte used to pad output.
     */
    protected static final byte PAD_DEFAULT = '='; // Allow static access to default

    protected final byte PAD = PAD_DEFAULT; // instance variable just in case it needs to vary later

    /** Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32 */
    private final int unencodedBlockSize;

    /** Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32 */
    private final int encodedBlockSize;

    /**
     * Chunksize for encoding. Not used when decoding.
     * A value of zero or less implies no chunking of the encoded data.
     * Rounded down to nearest multiple of encodedBlockSize.
     */
    protected final int lineLength;

    /**
     * Size of chunk separator. Not used unless {@link #lineLength} > 0.
     */
    private final int chunkSeparatorLength;

    /**
     * Note <code>lineLength</code> is rounded down to the nearest multiple of {@link #encodedBlockSize}
     * If <code>chunkSeparatorLength</code> is zero, then chunking is disabled.
     * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
     * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
     * @param lineLength if &gt; 0, use chunking with a length <code>lineLength</code>
     * @param chunkSeparatorLength the chunk separator length, if relevant
     */
    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize,
                         final int lineLength, final int chunkSeparatorLength) {
        this.unencodedBlockSize = unencodedBlockSize;
        this.encodedBlockSize = encodedBlockSize;
        final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
        this.lineLength = useChunking ? (lineLength / encodedBlockSize) * encodedBlockSize : 0;
        this.chunkSeparatorLength = chunkSeparatorLength;
    }

    /**
     * Returns true if this object has buffered data for reading.
     *
     * @param context the context to be used
     * @return true if there is data still available for reading.
     */
    boolean hasData(final Context context) {  // package protected for access from I/O streams
        return context.buffer != null;
    }

    /**
     * Returns the amount of buffered data available for reading.
     *
     * @param context the context to be used
     * @return The amount of buffered data available for reading.
     */
    int available(final Context context) {  // package protected for access from I/O streams
        return context.buffer != null ? context.pos - context.readPos : 0;
    }

    /**
     * Get the default buffer size. Can be overridden.
     *
     * @return {@link #DEFAULT_BUFFER_SIZE}
     */
    protected int getDefaultBufferSize() {
        return DEFAULT_BUFFER_SIZE;
    }

    /**
     * Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
     * @param context the context to be used
     */
    private byte[] resizeBuffer(final Context context) {
        if (context.buffer == null) {
            context.buffer = new byte[getDefaultBufferSize()];
            context.pos = 0;
            context.readPos = 0;
        } else {
            final byte[] b = new byte[context.buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
            System.arraycopy(context.buffer, 0, b, 0, context.buffer.length);
            context.buffer = b;
        }
        return context.buffer;
    }

    /**
     * Ensure that the buffer has room for <code>size</code> bytes
     *
     * @param size minimum spare space required
     * @param context the context to be used
     */
    protected byte[] ensureBufferSize(final int size, final Context context){
        if ((context.buffer == null) || (context.buffer.length < context.pos + size)){
            return resizeBuffer(context);
        }
        return context.buffer;
    }

    /**
     * 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.
     * <p>
     * Package protected for access from I/O streams.
     *
     * @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).
     * @param context
     *            the context to be used
     * @return The number of bytes successfully extracted into the provided byte[] array.
     */
    int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
        if (context.buffer != null) {
            final int len = Math.min(available(context), bAvail);
            System.arraycopy(context.buffer, context.readPos, b, bPos, len);
            context.readPos += len;
            if (context.readPos >= context.pos) {
                context.buffer = null; // so hasData() will return false, and this method can return -1
            }
            return len;
        }
        return context.eof ? EOF : 0;
    }

    /**
     * Checks if a byte value is whitespace or not.
     * Whitespace is taken to mean: space, tab, CR, LF
     * @param byteToCheck
     *            the byte to check
     * @return true if byte is whitespace, false otherwise
     */
    protected static boolean isWhiteSpace(final byte byteToCheck) {
        switch (byteToCheck) {
            case ' ' :
            case '\n' :
            case '\r' :
            case '\t' :
                return true;
            default :
                return false;
        }
    }

    /**
     * Encodes an Object using the Base-N 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 obj
     *            Object to encode
     * @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
     *             if the parameter supplied is not of type byte[]
     */
    public Object encode(final Object obj) throws Exception {
        if (!(obj instanceof byte[])) {
            throw new Exception("Parameter supplied to Base-N encode is not a byte[]");
        }
        return encode((byte[]) obj);
    }

    /**
     * Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet.
     * Uses UTF8 encoding.
     *
     * @param pArray
     *            a byte array containing binary data
     * @return A String containing only Base-N character data
     * @throws UnsupportedEncodingException 
     */
    public String encodeToString(final byte[] pArray) throws UnsupportedEncodingException {
        return new String(encode(pArray), "UTF-8");
    }

    /**
     * Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet.
     * Uses UTF8 encoding.
     *
     * @param pArray a byte array containing binary data
     * @return String containing only character data in the appropriate alphabet.
     * @throws UnsupportedEncodingException 
    */
    public String encodeAsString(final byte[] pArray) throws UnsupportedEncodingException{
        return new String(encode(pArray), "UTF-8");
    }

    /**
     * Decodes an Object using the Base-N 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[] or String.
     *
     * @param obj
     *            Object to decode
     * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String
     *         supplied.
     *             if the parameter supplied is not of type byte[]
     */
    public Object decode(final Object obj) throws Exception {
        if (obj instanceof byte[]) {
            return decode((byte[]) obj);
        } else if (obj instanceof String) {
            return decode((String) obj);
        } else {
            throw new Exception("Parameter supplied to Base-N decode is not a byte[] or a String");
        }
    }

    /**
     * Decodes a String containing characters in the Base-N alphabet.
     *
     * @param pArray
     *            A String containing Base-N character data
     * @return a byte array containing binary data
     * @throws UnsupportedEncodingException 
     */
    public byte[] decode(final String pArray) throws UnsupportedEncodingException {
        return decode(pArray.getBytes("UTF-8"));
    }

    /**
     * Decodes a byte[] containing characters in the Base-N alphabet.
     *
     * @param pArray
     *            A byte array containing Base-N character data
     * @return a byte array containing binary data
     */
    public byte[] decode(final byte[] pArray) {
        if (pArray == null || pArray.length == 0) {
            return pArray;
        }
        final Context context = new Context();
        decode(pArray, 0, pArray.length, context);
        decode(pArray, 0, EOF, context); // Notify decoder of EOF.
        final byte[] result = new byte[context.pos];
        readResults(result, 0, result.length, context);
        return result;
    }

    /**
     * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
     *
     * @param pArray
     *            a byte array containing binary data
     * @return A byte array containing only the basen alphabetic character data
     */
    public byte[] encode(final byte[] pArray) {
        if (pArray == null || pArray.length == 0) {
            return pArray;
        }
        final Context context = new Context();
        encode(pArray, 0, pArray.length, context);
        encode(pArray, 0, EOF, context); // Notify encoder of EOF.
        final byte[] buf = new byte[context.pos - context.readPos];
        readResults(buf, 0, buf.length, context);
        return buf;
    }

    // package protected for access from I/O streams
    abstract void encode(byte[] pArray, int i, int length, Context context);

    // package protected for access from I/O streams
    abstract void decode(byte[] pArray, int i, int length, Context context);

    /**
     * Returns whether or not the <code>octet</code> is in the current alphabet.
     * Does not allow whitespace or pad.
     *
     * @param value The value to test
     *
     * @return {@code true} if the value is defined in the current alphabet, {@code false} otherwise.
     */
    protected abstract boolean isInAlphabet(byte value);

    /**
     * Tests a given byte array to see if it contains only valid characters within the alphabet.
     * The method optionally treats whitespace and pad as valid.
     *
     * @param arrayOctet byte array to test
     * @param allowWSPad if {@code true}, then whitespace and PAD are also allowed
     *
     * @return {@code true} if all bytes are valid characters in the alphabet or if the byte array is empty;
     *         {@code false}, otherwise
     */
    public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
        for (int i = 0; i < arrayOctet.length; i++) {
            if (!isInAlphabet(arrayOctet[i]) &&
                    (!allowWSPad || (arrayOctet[i] != PAD) && !isWhiteSpace(arrayOctet[i]))) {
                return false;
            }
        }
        return true;
    }

    /**
     * Tests a given String to see if it contains only valid characters within the alphabet.
     * The method treats whitespace and PAD as valid.
     *
     * @param basen String to test
     * @return {@code true} if all characters in the String are valid characters in the alphabet or if
     *         the String is empty; {@code false}, otherwise
     * @throws UnsupportedEncodingException 
     * @see #isInAlphabet(byte[], boolean)
     */
    public boolean isInAlphabet(final String basen) throws UnsupportedEncodingException {
        return isInAlphabet(basen.getBytes("UTF-8"), true);
    }

    /**
     * Tests a given byte array to see if it contains any characters within the alphabet or PAD.
     *
     * Intended for use in checking line-ending arrays
     *
     * @param arrayOctet
     *            byte array to test
     * @return {@code true} if any byte is a valid character in the alphabet or PAD; {@code false} otherwise
     */
    protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
        if (arrayOctet == null) {
            return false;
        }
        for (final byte element : arrayOctet) {
            if (PAD == element || isInAlphabet(element)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Calculates the amount of space needed to encode the supplied array.
     *
     * @param pArray byte[] array which will later be encoded
     *
     * @return amount of space needed to encoded the supplied array.
     * Returns a long since a max-len array will require > Integer.MAX_VALUE
     */
    public long getEncodedLength(final byte[] pArray) {
        // Calculate non-chunked size - rounded up to allow for padding
        // cast to long is needed to avoid possibility of overflow
        long len = ((pArray.length + unencodedBlockSize-1)  / unencodedBlockSize) * (long) encodedBlockSize;
        if (lineLength > 0) { // We're using chunking
            // Round up to nearest multiple
            len += ((len + lineLength-1) / lineLength) * chunkSeparatorLength;
        }
        return len;
    }

}