3rdpartylibs/fastreports.wpf/FastReport.Base/Barcode/QRCode/Encoder.cs

/*
* 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.
*/
using System;
namespace FastReport.Barcode.QRCode
{

    /*  /// <author>  satorux@google.com (Satoru Takabayashi) - creator
      /// </author>
      /// <author>  dswitkin@google.com (Daniel Switkin) - ported from C++
      /// </author>
      /// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source 
      /// </author>*/
    internal sealed class Encoder
    {

        // The original table is defined in the table 5 of JISX0510:2004 (p.19).
        //UPGRADE_NOTE: Final was removed from the declaration of 'ALPHANUMERIC_TABLE'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
        private static readonly int[] ALPHANUMERIC_TABLE = new int[] { -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 System.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)
        {
            int penalty = 0;
            penalty += MaskUtil.applyMaskPenaltyRule1(matrix);
            penalty += MaskUtil.applyMaskPenaltyRule2(matrix);
            penalty += MaskUtil.applyMaskPenaltyRule3(matrix);
            penalty += MaskUtil.applyMaskPenaltyRule4(matrix);
            return penalty;
        }

        /*/// <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>*/
        public static void encode(System.String content, ErrorCorrectionLevel ecLevel, QRCode qrCode)
        {
            encode(content, ecLevel, null, qrCode);
        }

        public static void encode(System.String content, ErrorCorrectionLevel ecLevel, System.String encoding, QRCode qrCode)
        {
            if (encoding == null)
            {
                encoding = DEFAULT_BYTE_MODE_ENCODING;
            }

            // Step 1: Choose the mode (encoding).
            Mode mode = chooseMode(content, encoding);

            // Step 2: Append "bytes" into "dataBits" in appropriate encoding.
            BitVector dataBits = new BitVector();
            appendBytes(content, mode, dataBits, encoding);
            // Step 3: Initialize QR code that can contain "dataBits".
            int numInputBytes = dataBits.sizeInBytes();
            initQRCode(numInputBytes, ecLevel, mode, qrCode);

            // Step 4: Build another bit vector that contains header and data.
            BitVector headerAndDataBits = new BitVector();

            // tz - commented out to match zxing encoder online
            // Step 4.5: Append ECI message if applicable
            /*if (mode == Mode.BYTE && !DEFAULT_BYTE_MODE_ENCODING.Equals(encoding))
            {
              CharacterSetECI eci = CharacterSetECI.getCharacterSetECIByName(encoding);
              if (eci != null)
              {
                appendECI(eci, headerAndDataBits);
              }
            }*/

            appendModeInfo(mode, headerAndDataBits);

            int numLetters = mode.Equals(Mode.BYTE) ? dataBits.sizeInBytes() : content.Length;
            appendLengthInfo(numLetters, qrCode.Version, mode, headerAndDataBits);
            headerAndDataBits.appendBitVector(dataBits);

            // Step 5: Terminate the bits properly.
            terminateBits(qrCode.NumDataBytes, headerAndDataBits);

            // Step 6: Interleave data bits with error correction code.
            BitVector finalBits = new BitVector();
            interleaveWithECBytes(headerAndDataBits, qrCode.NumTotalBytes, qrCode.NumDataBytes, qrCode.NumRSBlocks, finalBits);

            // Step 7: Choose the mask pattern and set to "qrCode".
            ByteMatrix matrix = new ByteMatrix(qrCode.MatrixWidth, qrCode.MatrixWidth);
            qrCode.MaskPattern = chooseMaskPattern(finalBits, qrCode.ECLevel, qrCode.Version, matrix);

            // Step 8.  Build the matrix and set it to "qrCode".
            MatrixUtil.buildMatrix(finalBits, qrCode.ECLevel, qrCode.Version, qrCode.MaskPattern, matrix);
            qrCode.Matrix = matrix;
            // Step 9.  Make sure we have a valid QR Code.
            if (!qrCode.Valid)
            {
                throw new WriterException("Invalid QR code: " + qrCode.ToString());
            }
        }

        /*/// <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(System.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 {@link Mode#KANJI}.
        /// </summary>*/
        public static Mode chooseMode(System.String content, System.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;
            }
            else if (hasNumeric)
            {
                return Mode.NUMERIC;
            }
            return Mode.BYTE;
        }

        private static bool isOnlyDoubleByteKanji(System.String content)
        {
            sbyte[] bytes;
            try
            {
                //UPGRADE_TODO: Method 'java.lang.String.getBytes' was converted to 'System.Text.Encoding.GetEncoding(string).GetBytes(string)' which has a different behavior. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1073_javalangStringgetBytes_javalangString'"
                bytes = SupportClass.ToSByteArray(System.Text.Encoding.GetEncoding("Shift_JIS").GetBytes(content));
            }
            catch
            {
                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;
        }

        private static int chooseMaskPattern(BitVector bits, ErrorCorrectionLevel ecLevel, int version, ByteMatrix matrix)
        {

            int minPenalty = System.Int32.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;
        }

        /*/// <summary> Initialize "qrCode" according to "numInputBytes", "ecLevel", and "mode". On success,
        /// modify "qrCode".
        /// </summary>*/
        private static void initQRCode(int numInputBytes, ErrorCorrectionLevel ecLevel, Mode mode, QRCode qrCode)
        {
            qrCode.ECLevel = ecLevel;
            qrCode.Mode = mode;

            // 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;
                // getNumRSBlocks = 5
                int numRSBlocks = ecBlocks.NumBlocks;
                // getNumDataBytes = 196 - 130 = 66
                int numDataBytes = numBytes - numEcBytes;
                // We want to choose the smallest version which can contain data of "numInputBytes" + some
                // extra bits for the header (mode info and length info). The header can be three bytes
                // (precisely 4 + 16 bits) at most. Hence we do +3 here.
                if (numDataBytes >= numInputBytes + 3)
                {
                    // Yay, we found the proper rs block info!
                    qrCode.Version = versionNum;
                    qrCode.NumTotalBytes = numBytes;
                    qrCode.NumDataBytes = numDataBytes;
                    qrCode.NumRSBlocks = numRSBlocks;
                    // getNumECBytes = 196 - 66 = 130
                    qrCode.NumECBytes = numEcBytes;
                    // matrix width = 21 + 6 * 4 = 45
                    qrCode.MatrixWidth = version.DimensionForVersion;
                    return;
                }
            }
            throw new WriterException("Cannot find proper rs block info (input data too big?)");
        }

        /*/// <summary> Terminate bits as described in 8.4.8 and 8.4.9 of JISX0510:2004 (p.24).</summary>*/
        internal static void terminateBits(int numDataBytes, BitVector bits)
        {
            int capacity = numDataBytes << 3;
            if (bits.size() > capacity)
            {
                throw new WriterException("data bits cannot fit in the QR Code" + bits.size() + " > " + capacity);
            }
            // Append termination bits. See 8.4.8 of JISX0510:2004 (p.24) for details.
            // TODO: srowen says we can remove this for loop, since the 4 terminator bits are optional if
            // the last byte has less than 4 bits left. So it amounts to padding the last byte with zeroes
            // either way.
            for (int i = 0; i < 4 && bits.size() < capacity; ++i)
            {
                bits.appendBit(0);
            }
            int numBitsInLastByte = bits.size() % 8;
            // If the last byte isn't 8-bit aligned, we'll add padding bits.
            if (numBitsInLastByte > 0)
            {
                int numPaddingBits = 8 - numBitsInLastByte;
                for (int i = 0; i < numPaddingBits; ++i)
                {
                    bits.appendBit(0);
                }
            }
            // Should be 8-bit aligned here.
            if (bits.size() % 8 != 0)
            {
                throw new WriterException("Number of bits is not a multiple of 8");
            }
            // 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)
            {
                if (i % 2 == 0)
                {
                    bits.appendBits(0xec, 8);
                }
                else
                {
                    bits.appendBits(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>*/
        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>*/
        internal static void interleaveWithECBytes(BitVector bits, int numTotalBytes, int numDataBytes, int numRSBlocks, BitVector result)
        {

            // "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.
            System.Collections.ArrayList blocks = System.Collections.ArrayList.Synchronized(new System.Collections.ArrayList(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);

                ByteArray dataBytes = new ByteArray();
                dataBytes.set_Renamed(bits.Array, dataBytesOffset, numDataBytesInBlock[0]);
                ByteArray ecBytes = generateECBytes(dataBytes, numEcBytesInBlock[0]);
                blocks.Add(new BlockPair(dataBytes, ecBytes));

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

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

        internal static ByteArray generateECBytes(ByteArray dataBytes, int numEcBytesInBlock)
        {
            int numDataBytes = dataBytes.size();
            int[] toEncode = new int[numDataBytes + numEcBytesInBlock];
            for (int i = 0; i < numDataBytes; i++)
            {
                toEncode[i] = dataBytes.at(i);
            }
            new ReedSolomonEncoder(GF256.QR_CODE_FIELD).encode(toEncode, numEcBytesInBlock);

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

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


        /*/// <summary> Append length info. On success, store the result in "bits".</summary>*/
        internal static void appendLengthInfo(int numLetters, int version, Mode mode, BitVector bits)
        {
            int numBits = mode.getCharacterCountBits(Version.getVersionForNumber(version));
            if (numLetters > ((1 << numBits) - 1))
            {
                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>*/
        internal static void appendBytes(System.String content, Mode mode, BitVector bits, System.String encoding)
        {
            if (mode.Equals(Mode.NUMERIC))
            {
                appendNumericBytes(content, bits);
            }
            else if (mode.Equals(Mode.ALPHANUMERIC))
            {
                appendAlphanumericBytes(content, bits);
            }
            else if (mode.Equals(Mode.BYTE))
            {
                append8BitBytes(content, bits, encoding);
            }
            else if (mode.Equals(Mode.KANJI))
            {
                appendKanjiBytes(content, bits);
            }
            else
            {
                throw new WriterException("Invalid mode: " + mode);
            }
        }

        internal static void appendNumericBytes(System.String content, BitVector 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++;
                }
            }
        }

        internal static void appendAlphanumericBytes(System.String content, BitVector 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++;
                }
            }
        }

        internal static void append8BitBytes(System.String content, BitVector bits, System.String encoding)
        {
            sbyte[] bytes;
            try
            {
                //UPGRADE_TODO: Method 'java.lang.String.getBytes' was converted to 'System.Text.Encoding.GetEncoding(string).GetBytes(string)' which has a different behavior. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1073_javalangStringgetBytes_javalangString'"
                bytes = SupportClass.ToSByteArray(System.Text.Encoding.GetEncoding(encoding).GetBytes(content));
            }
            catch (System.IO.IOException uee)
            {
                //UPGRADE_TODO: The equivalent in .NET for method 'java.lang.Throwable.toString' may return a different value. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1043'"
                throw new WriterException(uee.ToString());
            }
            for (int i = 0; i < bytes.Length; ++i)
            {
                bits.appendBits(bytes[i], 8);
            }
        }

        internal static void appendKanjiBytes(System.String content, BitVector bits)
        {
            sbyte[] bytes;
            try
            {
                //UPGRADE_TODO: Method 'java.lang.String.getBytes' was converted to 'System.Text.Encoding.GetEncoding(string).GetBytes(string)' which has a different behavior. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1073_javalangStringgetBytes_javalangString'"
                bytes = SupportClass.ToSByteArray(System.Text.Encoding.GetEncoding("Shift_JIS").GetBytes(content));
            }
            catch (System.IO.IOException uee)
            {
                //UPGRADE_TODO: The equivalent in .NET for method 'java.lang.Throwable.toString' may return a different value. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1043'"
                throw new WriterException(uee.ToString());
            }
            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);
            }
        }
    }
}