zxing/csharp/qrcode/encoder/Encoder.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;

/*
 * Copyright 2008 ZXing authors
 *
 * Licensed 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.
 */

namespace com.google.zxing.qrcode.encoder
{

	using EncodeHintType = com.google.zxing.EncodeHintType;
	using WriterException = com.google.zxing.WriterException;
	using BitArray = com.google.zxing.common.BitArray;
	using CharacterSetECI = com.google.zxing.common.CharacterSetECI;
	using GenericGF = com.google.zxing.common.reedsolomon.GenericGF;
	using ReedSolomonEncoder = com.google.zxing.common.reedsolomon.ReedSolomonEncoder;
	using ErrorCorrectionLevel = com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
	using Mode = com.google.zxing.qrcode.decoder.Mode;
	using Version = com.google.zxing.qrcode.decoder.Version;
    using com.google.zxing.common;


	/// <summary>
	/// @author satorux@google.com (Satoru Takabayashi) - creator
	/// @author dswitkin@google.com (Daniel Switkin) - ported from C++
	/// </summary>
	public sealed class Encoder
	{

	  // The original table is defined in the table 5 of JISX0510:2004 (p.19).
	  private static readonly int[] ALPHANUMERIC_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, 36, -1, -1, -1, 37, 38, -1, -1, -1, -1, 39, 40, -1, 41, 42, 43, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 44, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, -1, -1};

	  internal const string DEFAULT_BYTE_MODE_ENCODING = "ISO-8859-1";

	  private Encoder()
	  {
	  }

	  // The mask penalty calculation is complicated.  See Table 21 of JISX0510:2004 (p.45) for details.
	  // Basically it applies four rules and summate all penalties.
	  private static int calculateMaskPenalty(ByteMatrix matrix)
	  {
		return MaskUtil.applyMaskPenaltyRule1(matrix) + MaskUtil.applyMaskPenaltyRule2(matrix) + MaskUtil.applyMaskPenaltyRule3(matrix) + MaskUtil.applyMaskPenaltyRule4(matrix);
	  }

	  /// <summary>
	  ///  Encode "bytes" with the error correction level "ecLevel". The encoding mode will be chosen
	  /// internally by chooseMode(). On success, store the result in "qrCode".
	  /// 
	  /// We recommend you to use QRCode.EC_LEVEL_L (the lowest level) for
	  /// "getECLevel" since our primary use is to show QR code on desktop screens. We don't need very
	  /// strong error correction for this purpose.
	  /// 
	  /// Note that there is no way to encode bytes in MODE_KANJI. We might want to add EncodeWithMode()
	  /// with which clients can specify the encoding mode. For now, we don't need the functionality.
	  /// </summary>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: public static QRCode encode(String content, com.google.zxing.qrcode.decoder.ErrorCorrectionLevel ecLevel) throws com.google.zxing.WriterException
	  public static QRCode encode(string content, ErrorCorrectionLevel ecLevel)
	  {
		return encode(content, ecLevel, null);
	  }

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: public static QRCode encode(String content, com.google.zxing.qrcode.decoder.ErrorCorrectionLevel ecLevel, java.util.Map<com.google.zxing.EncodeHintType,?> hints) throws com.google.zxing.WriterException
      public static QRCode encode(string content, ErrorCorrectionLevel ecLevel, IDictionary<EncodeHintType, object> hints)
	  {

		// Determine what character encoding has been specified by the caller, if any
        //string encoding = hints == null ? null : (string) hints[EncodeHintType.CHARACTER_SET];
        string encoding = null;
        if (hints != null && hints.ContainsKey(EncodeHintType.CHARACTER_SET))
        {
            encoding = (string) hints[EncodeHintType.CHARACTER_SET];
        }

		if (encoding == null)
		{
		  encoding = DEFAULT_BYTE_MODE_ENCODING;
		}

		// Pick an encoding mode appropriate for the content. Note that this will not attempt to use
		// multiple modes / segments even if that were more efficient. Twould be nice.
		Mode mode = chooseMode(content, encoding);

		// This will store the header information, like mode and
		// length, as well as "header" segments like an ECI segment.
		BitArray headerBits = new BitArray();

		// Append ECI segment if applicable
		if (mode == Mode.BYTE && !DEFAULT_BYTE_MODE_ENCODING.Equals(encoding))
		{
		  CharacterSetECI eci = CharacterSetECI.getCharacterSetECIByName(encoding);
		  if (eci != null)
		  {
			appendECI(eci, headerBits);
		  }
		}

		// (With ECI in place,) Write the mode marker
		appendModeInfo(mode, headerBits);

		// Collect data within the main segment, separately, to count its size if needed. Don't add it to
		// main payload yet.
		BitArray dataBits = new BitArray();
		appendBytes(content, mode, dataBits, encoding);

		// Hard part: need to know version to know how many bits length takes. But need to know how many
		// bits it takes to know version. First we take a guess at version by assuming version will be
		// the minimum, 1:

		int provisionalBitsNeeded = headerBits.Size + mode.getCharacterCountBits(Version.getVersionForNumber(1)) + dataBits.Size;
		Version provisionalVersion = chooseVersion(provisionalBitsNeeded, ecLevel);

		// Use that guess to calculate the right version. I am still not sure this works in 100% of cases.

		int bitsNeeded = headerBits.Size + mode.getCharacterCountBits(provisionalVersion) + dataBits.Size;
		Version version = chooseVersion(bitsNeeded, ecLevel);

		BitArray headerAndDataBits = new BitArray();
		headerAndDataBits.appendBitArray(headerBits);
		// Find "length" of main segment and write it
		int numLetters = mode == Mode.BYTE ? dataBits.SizeInBytes : content.Length;
		appendLengthInfo(numLetters, version, mode, headerAndDataBits);
		// Put data together into the overall payload
		headerAndDataBits.appendBitArray(dataBits);

		Version.ECBlocks ecBlocks = version.getECBlocksForLevel(ecLevel);
		int numDataBytes = version.TotalCodewords - ecBlocks.TotalECCodewords;

		// Terminate the bits properly.
		terminateBits(numDataBytes, headerAndDataBits);

		// Interleave data bits with error correction code.
		BitArray finalBits = interleaveWithECBytes(headerAndDataBits, version.TotalCodewords, numDataBytes, ecBlocks.NumBlocks);

		QRCode qrCode = new QRCode();

		qrCode.ECLevel = ecLevel;
		qrCode.Mode = mode;
		qrCode.Version = version;

		//  Choose the mask pattern and set to "qrCode".
		int dimension = version.DimensionForVersion;
		ByteMatrix matrix = new ByteMatrix(dimension, dimension);
		int maskPattern = chooseMaskPattern(finalBits, ecLevel, version, matrix);
		qrCode.MaskPattern = maskPattern;

		// Build the matrix and set it to "qrCode".
		MatrixUtil.buildMatrix(finalBits, ecLevel, version, maskPattern, matrix);
		qrCode.Matrix = matrix;

		return qrCode;
	  }

	  /// <returns> the code point of the table used in alphanumeric mode or
	  ///  -1 if there is no corresponding code in the table. </returns>
	  internal static int getAlphanumericCode(int code)
	  {
		if (code < ALPHANUMERIC_TABLE.Length)
		{
		  return ALPHANUMERIC_TABLE[code];
		}
		return -1;
	  }

	  public static Mode chooseMode(string content)
	  {
		return chooseMode(content, null);
	  }

	  /// <summary>
	  /// Choose the best mode by examining the content. Note that 'encoding' is used as a hint;
	  /// if it is Shift_JIS, and the input is only double-byte Kanji, then we return <seealso cref="Mode#KANJI"/>.
	  /// </summary>
	  private static Mode chooseMode(string content, string encoding)
	  {
		if ("Shift_JIS".Equals(encoding))
		{
		  // Choose Kanji mode if all input are double-byte characters
		  return isOnlyDoubleByteKanji(content) ? Mode.KANJI : Mode.BYTE;
		}
		bool hasNumeric = false;
		bool hasAlphanumeric = false;
		for (int i = 0; i < content.Length; ++i)
		{
		  char c = content[i];
		  if (c >= '0' && c <= '9')
		  {
			hasNumeric = true;
		  }
		  else if (getAlphanumericCode(c) != -1)
		  {
			hasAlphanumeric = true;
		  }
		  else
		  {
			return Mode.BYTE;
		  }
		}
		if (hasAlphanumeric)
		{
		  return Mode.ALPHANUMERIC;
		}
		if (hasNumeric)
		{
		  return Mode.NUMERIC;
		}
		return Mode.BYTE;
	  }

	  private static bool isOnlyDoubleByteKanji(string content)
	  {
		sbyte[] bytes;
		try
		{
          //bytes = content.getBytes("Shift_JIS");
		    Encoding en = Encoding.GetEncoding("Shift_JIS");
		    bytes = en.GetBytes(content).ToSBytes();
		}
        catch (System.IO.IOException)
		{
		  return false;
		}
		int length = bytes.Length;
		if (length % 2 != 0)
		{
		  return false;
		}
		for (int i = 0; i < length; i += 2)
		{
		  int byte1 = bytes[i] & 0xFF;
		  if ((byte1 < 0x81 || byte1 > 0x9F) && (byte1 < 0xE0 || byte1 > 0xEB))
		  {
			return false;
		  }
		}
		return true;
	  }

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: private static int chooseMaskPattern(com.google.zxing.common.BitArray bits, com.google.zxing.qrcode.decoder.ErrorCorrectionLevel ecLevel, com.google.zxing.qrcode.decoder.Version version, ByteMatrix matrix) throws com.google.zxing.WriterException
	  private static int chooseMaskPattern(BitArray bits, ErrorCorrectionLevel ecLevel, Version version, ByteMatrix matrix)
	  {

		int minPenalty = int.MaxValue; // Lower penalty is better.
		int bestMaskPattern = -1;
		// We try all mask patterns to choose the best one.
		for (int maskPattern = 0; maskPattern < QRCode.NUM_MASK_PATTERNS; maskPattern++)
		{
		  MatrixUtil.buildMatrix(bits, ecLevel, version, maskPattern, matrix);
		  int penalty = calculateMaskPenalty(matrix);
		  if (penalty < minPenalty)
		  {
			minPenalty = penalty;
			bestMaskPattern = maskPattern;
		  }
		}
		return bestMaskPattern;
	  }

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: private static com.google.zxing.qrcode.decoder.Version chooseVersion(int numInputBits, com.google.zxing.qrcode.decoder.ErrorCorrectionLevel ecLevel) throws com.google.zxing.WriterException
	  private static Version chooseVersion(int numInputBits, ErrorCorrectionLevel ecLevel)
	  {
		// In the following comments, we use numbers of Version 7-H.
		for (int versionNum = 1; versionNum <= 40; versionNum++)
		{
		  Version version = Version.getVersionForNumber(versionNum);
		  // numBytes = 196
		  int numBytes = version.TotalCodewords;
		  // getNumECBytes = 130
		  Version.ECBlocks ecBlocks = version.getECBlocksForLevel(ecLevel);
		  int numEcBytes = ecBlocks.TotalECCodewords;
		  // getNumDataBytes = 196 - 130 = 66
		  int numDataBytes = numBytes - numEcBytes;
		  int totalInputBytes = (numInputBits + 7) / 8;
		  if (numDataBytes >= totalInputBytes)
		  {
			return version;
		  }
		}
		throw new WriterException("Data too big");
	  }

	  /// <summary>
	  /// Terminate bits as described in 8.4.8 and 8.4.9 of JISX0510:2004 (p.24).
	  /// </summary>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static void terminateBits(int numDataBytes, com.google.zxing.common.BitArray bits) throws com.google.zxing.WriterException
	  internal static void terminateBits(int numDataBytes, BitArray bits)
	  {
		int capacity = numDataBytes << 3;
		if (bits.Size > capacity)
		{
		  throw new WriterException("data bits cannot fit in the QR Code" + bits.Size + " > " + capacity);
		}
		for (int i = 0; i < 4 && bits.Size < capacity; ++i)
		{
		  bits.appendBit(false);
		}
		// Append termination bits. See 8.4.8 of JISX0510:2004 (p.24) for details.
		// If the last byte isn't 8-bit aligned, we'll add padding bits.
		int numBitsInLastByte = bits.Size & 0x07;
		if (numBitsInLastByte > 0)
		{
		  for (int i = numBitsInLastByte; i < 8; i++)
		  {
			bits.appendBit(false);
		  }
		}
		// If we have more space, we'll fill the space with padding patterns defined in 8.4.9 (p.24).
		int numPaddingBytes = numDataBytes - bits.SizeInBytes;
		for (int i = 0; i < numPaddingBytes; ++i)
		{
		  bits.appendBits((i & 0x01) == 0 ? 0xEC : 0x11, 8);
		}
		if (bits.Size != capacity)
		{
		  throw new WriterException("Bits size does not equal capacity");
		}
	  }

	  /// <summary>
	  /// Get number of data bytes and number of error correction bytes for block id "blockID". Store
	  /// the result in "numDataBytesInBlock", and "numECBytesInBlock". See table 12 in 8.5.1 of
	  /// JISX0510:2004 (p.30)
	  /// </summary>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static void getNumDataBytesAndNumECBytesForBlockID(int numTotalBytes, int numDataBytes, int numRSBlocks, int blockID, int[] numDataBytesInBlock, int[] numECBytesInBlock) throws com.google.zxing.WriterException
	  internal static void getNumDataBytesAndNumECBytesForBlockID(int numTotalBytes, int numDataBytes, int numRSBlocks, int blockID, int[] numDataBytesInBlock, int[] numECBytesInBlock)
	  {
		if (blockID >= numRSBlocks)
		{
		  throw new WriterException("Block ID too large");
		}
		// numRsBlocksInGroup2 = 196 % 5 = 1
		int numRsBlocksInGroup2 = numTotalBytes % numRSBlocks;
		// numRsBlocksInGroup1 = 5 - 1 = 4
		int numRsBlocksInGroup1 = numRSBlocks - numRsBlocksInGroup2;
		// numTotalBytesInGroup1 = 196 / 5 = 39
		int numTotalBytesInGroup1 = numTotalBytes / numRSBlocks;
		// numTotalBytesInGroup2 = 39 + 1 = 40
		int numTotalBytesInGroup2 = numTotalBytesInGroup1 + 1;
		// numDataBytesInGroup1 = 66 / 5 = 13
		int numDataBytesInGroup1 = numDataBytes / numRSBlocks;
		// numDataBytesInGroup2 = 13 + 1 = 14
		int numDataBytesInGroup2 = numDataBytesInGroup1 + 1;
		// numEcBytesInGroup1 = 39 - 13 = 26
		int numEcBytesInGroup1 = numTotalBytesInGroup1 - numDataBytesInGroup1;
		// numEcBytesInGroup2 = 40 - 14 = 26
		int numEcBytesInGroup2 = numTotalBytesInGroup2 - numDataBytesInGroup2;
		// Sanity checks.
		// 26 = 26
		if (numEcBytesInGroup1 != numEcBytesInGroup2)
		{
		  throw new WriterException("EC bytes mismatch");
		}
		// 5 = 4 + 1.
		if (numRSBlocks != numRsBlocksInGroup1 + numRsBlocksInGroup2)
		{
		  throw new WriterException("RS blocks mismatch");
		}
		// 196 = (13 + 26) * 4 + (14 + 26) * 1
		if (numTotalBytes != ((numDataBytesInGroup1 + numEcBytesInGroup1) * numRsBlocksInGroup1) + ((numDataBytesInGroup2 + numEcBytesInGroup2) * numRsBlocksInGroup2))
		{
		  throw new WriterException("Total bytes mismatch");
		}

		if (blockID < numRsBlocksInGroup1)
		{
		  numDataBytesInBlock[0] = numDataBytesInGroup1;
		  numECBytesInBlock[0] = numEcBytesInGroup1;
		}
		else
		{
		  numDataBytesInBlock[0] = numDataBytesInGroup2;
		  numECBytesInBlock[0] = numEcBytesInGroup2;
		}
	  }

	  /// <summary>
	  /// Interleave "bits" with corresponding error correction bytes. On success, store the result in
	  /// "result". The interleave rule is complicated. See 8.6 of JISX0510:2004 (p.37) for details.
	  /// </summary>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static com.google.zxing.common.BitArray interleaveWithECBytes(com.google.zxing.common.BitArray bits, int numTotalBytes, int numDataBytes, int numRSBlocks) throws com.google.zxing.WriterException
	  internal static BitArray interleaveWithECBytes(BitArray bits, int numTotalBytes, int numDataBytes, int numRSBlocks)
	  {

		// "bits" must have "getNumDataBytes" bytes of data.
		if (bits.SizeInBytes != numDataBytes)
		{
		  throw new WriterException("Number of bits and data bytes does not match");
		}

		// Step 1.  Divide data bytes into blocks and generate error correction bytes for them. We'll
		// store the divided data bytes blocks and error correction bytes blocks into "blocks".
		int dataBytesOffset = 0;
		int maxNumDataBytes = 0;
		int maxNumEcBytes = 0;

		// Since, we know the number of reedsolmon blocks, we can initialize the vector with the number.
		ICollection<BlockPair> blocks = new List<BlockPair>(numRSBlocks);

		for (int i = 0; i < numRSBlocks; ++i)
		{
		  int[] numDataBytesInBlock = new int[1];
		  int[] numEcBytesInBlock = new int[1];
		  getNumDataBytesAndNumECBytesForBlockID(numTotalBytes, numDataBytes, numRSBlocks, i, numDataBytesInBlock, numEcBytesInBlock);

		  int size = numDataBytesInBlock[0];
		  sbyte[] dataBytes = new sbyte[size];
		  bits.toBytes(8 * dataBytesOffset, dataBytes, 0, size);
		  sbyte[] ecBytes = generateECBytes(dataBytes, numEcBytesInBlock[0]);
		  blocks.Add(new BlockPair(dataBytes, ecBytes));

		  maxNumDataBytes = Math.Max(maxNumDataBytes, size);
		  maxNumEcBytes = Math.Max(maxNumEcBytes, ecBytes.Length);
		  dataBytesOffset += numDataBytesInBlock[0];
		}
		if (numDataBytes != dataBytesOffset)
		{
		  throw new WriterException("Data bytes does not match offset");
		}

		BitArray result = new BitArray();

		// First, place data blocks.
		for (int i = 0; i < maxNumDataBytes; ++i)
		{
		  foreach (BlockPair block in blocks)
		  {
			sbyte[] dataBytes = block.DataBytes;
			if (i < dataBytes.Length)
			{
			  result.appendBits(dataBytes[i], 8);
			}
		  }
		}
		// Then, place error correction blocks.
		for (int i = 0; i < maxNumEcBytes; ++i)
		{
		  foreach (BlockPair block in blocks)
		  {
			sbyte[] ecBytes = block.ErrorCorrectionBytes;
			if (i < ecBytes.Length)
			{
			  result.appendBits(ecBytes[i], 8);
			}
		  }
		}
		if (numTotalBytes != result.SizeInBytes) // Should be same.
		{
		  throw new WriterException("Interleaving error: " + numTotalBytes + " and " + result.SizeInBytes + " differ.");
		}

		return result;
	  }

	  internal static sbyte[] generateECBytes(sbyte[] dataBytes, int numEcBytesInBlock)
	  {
		int numDataBytes = dataBytes.Length;
		int[] toEncode = new int[numDataBytes + numEcBytesInBlock];
		for (int i = 0; i < numDataBytes; i++)
		{
		  toEncode[i] = dataBytes[i] & 0xFF;
		}
		(new ReedSolomonEncoder(GenericGF.QR_CODE_FIELD_256)).encode(toEncode, numEcBytesInBlock);

		sbyte[] ecBytes = new sbyte[numEcBytesInBlock];
		for (int i = 0; i < numEcBytesInBlock; i++)
		{
		  ecBytes[i] = (sbyte) toEncode[numDataBytes + i];
		}
		return ecBytes;
	  }

	  /// <summary>
	  /// Append mode info. On success, store the result in "bits".
	  /// </summary>
	  internal static void appendModeInfo(Mode mode, BitArray bits)
	  {
		bits.appendBits(mode.Bits, 4);
	  }


	  /// <summary>
	  /// Append length info. On success, store the result in "bits".
	  /// </summary>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static void appendLengthInfo(int numLetters, com.google.zxing.qrcode.decoder.Version version, com.google.zxing.qrcode.decoder.Mode mode, com.google.zxing.common.BitArray bits) throws com.google.zxing.WriterException
	  internal static void appendLengthInfo(int numLetters, Version version, Mode mode, BitArray bits)
	  {
		int numBits = mode.getCharacterCountBits(version);
		if (numLetters >= (1 << numBits))
		{
		  throw new WriterException(numLetters + " is bigger than " + ((1 << numBits) - 1));
		}
		bits.appendBits(numLetters, numBits);
	  }

	  /// <summary>
	  /// Append "bytes" in "mode" mode (encoding) into "bits". On success, store the result in "bits".
	  /// </summary>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static void appendBytes(String content, com.google.zxing.qrcode.decoder.Mode mode, com.google.zxing.common.BitArray bits, String encoding) throws com.google.zxing.WriterException
	  internal static void appendBytes(string content, Mode mode, BitArray bits, string encoding)
	  {
          if (mode == Mode.NUMERIC)
          {
             			appendNumericBytes(content, bits);
 
          }
          else if (mode == Mode.ALPHANUMERIC)
          {
appendAlphanumericBytes(content, bits);
          }
          else if (mode == Mode.BYTE)
          {
append8BitBytes(content, bits, encoding);
          }
          else if (mode == Mode.KANJI)
          {
              appendKanjiBytes(content, bits);
          } else
          {
              throw new WriterException("Invalid mode: " + mode);
          }

        //switch (mode)
        //{
        //  case NUMERIC:
        //    appendNumericBytes(content, bits);
        //    break;
        //  case ALPHANUMERIC:
        //    appendAlphanumericBytes(content, bits);
        //    break;
        //  case BYTE:
        //    append8BitBytes(content, bits, encoding);
        //    break;
        //  case KANJI:
        //    appendKanjiBytes(content, bits);
        //    break;
        //  default:
        //    throw new WriterException("Invalid mode: " + mode);
        //}
	  }

	  internal static void appendNumericBytes(string content, BitArray bits)
	  {
		int length = content.Length;
		int i = 0;
		while (i < length)
		{
		  int num1 = content[i] - '0';
		  if (i + 2 < length)
		  {
			// Encode three numeric letters in ten bits.
			int num2 = content[i + 1] - '0';
			int num3 = content[i + 2] - '0';
			bits.appendBits(num1 * 100 + num2 * 10 + num3, 10);
			i += 3;
		  }
		  else if (i + 1 < length)
		  {
			// Encode two numeric letters in seven bits.
			int num2 = content[i + 1] - '0';
			bits.appendBits(num1 * 10 + num2, 7);
			i += 2;
		  }
		  else
		  {
			// Encode one numeric letter in four bits.
			bits.appendBits(num1, 4);
			i++;
		  }
		}
	  }

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static void appendAlphanumericBytes(CharSequence content, com.google.zxing.common.BitArray bits) throws com.google.zxing.WriterException
	  internal static void appendAlphanumericBytes(string content, BitArray bits)
	  {
		int length = content.Length;
		int i = 0;
		while (i < length)
		{
		  int code1 = getAlphanumericCode(content[i]);
		  if (code1 == -1)
		  {
			throw new WriterException();
		  }
		  if (i + 1 < length)
		  {
			int code2 = getAlphanumericCode(content[i + 1]);
			if (code2 == -1)
			{
			  throw new WriterException();
			}
			// Encode two alphanumeric letters in 11 bits.
			bits.appendBits(code1 * 45 + code2, 11);
			i += 2;
		  }
		  else
		  {
			// Encode one alphanumeric letter in six bits.
			bits.appendBits(code1, 6);
			i++;
		  }
		}
	  }

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static void append8BitBytes(String content, com.google.zxing.common.BitArray bits, String encoding) throws com.google.zxing.WriterException
	  internal static void append8BitBytes(string content, BitArray bits, string encoding)
	  {
		sbyte[] bytes;
		try
		{
          //bytes = content.getBytes(encoding);
		    Encoding en = Encoding.GetEncoding(encoding);
		    bytes = en.GetBytes(content).ToSBytes();

		}
        catch (System.IO.IOException uee)
		{
		  throw new WriterException(uee);
		}
		foreach (sbyte b in bytes)
		{
		  bits.appendBits(b, 8);
		}
	  }

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: static void appendKanjiBytes(String content, com.google.zxing.common.BitArray bits) throws com.google.zxing.WriterException
	  internal static void appendKanjiBytes(string content, BitArray bits)
	  {
		sbyte[] bytes;
		try
		{

          //bytes = content.getBytes("Shift_JIS");
          Encoding en = Encoding.GetEncoding("Shift_JIS");
          bytes = en.GetBytes(content).ToSBytes();

		}
        catch (System.IO.IOException uee)
		{
		  throw new WriterException(uee);
		}
		int length = bytes.Length;
		for (int i = 0; i < length; i += 2)
		{
		  int byte1 = bytes[i] & 0xFF;
		  int byte2 = bytes[i + 1] & 0xFF;
		  int code = (byte1 << 8) | byte2;
		  int subtracted = -1;
		  if (code >= 0x8140 && code <= 0x9ffc)
		  {
			subtracted = code - 0x8140;
		  }
		  else if (code >= 0xe040 && code <= 0xebbf)
		  {
			subtracted = code - 0xc140;
		  }
		  if (subtracted == -1)
		  {
			throw new WriterException("Invalid byte sequence");
		  }
		  int encoded = ((subtracted >> 8) * 0xc0) + (subtracted & 0xff);
		  bits.appendBits(encoded, 13);
		}
	  }

	  private static void appendECI(CharacterSetECI eci, BitArray bits)
	  {
		bits.appendBits(Mode.ECI.Bits, 4);
		// This is correct for values up to 127, which is all we need now.
		bits.appendBits(eci.Value, 8);
	  }

	}

}