1.2.0.267

Committed 05 Oct 2025 03:17PM UTC coverage: 99.241% (-0.2%) from 99.412%

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Oops, disable net9.0 in the build

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99.1

/HtmlKit/HtmlTokenizer.cs

﻿//
// HtmlTokenizer.cs
//
// Author: Jeffrey Stedfast <jestedfa@microsoft.com>
//
// Copyright (c) 2015-2025 Jeffrey Stedfast <jestedfa@microsoft.com>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

using System;
using System.IO;
using System.Text;
using System.Runtime.CompilerServices;
using System.Diagnostics.CodeAnalysis;

namespace HtmlKit {
        /// <summary>
        /// An HTML tokenizer.
        /// </summary>
        /// <remarks>
        /// Tokenizes HTML text, emitting an <see cref="HtmlToken"/> for each token it encounters.
        /// </remarks>
        public class HtmlTokenizer
        {
                // Specification: https://dev.w3.org/html5/spec-LC/tokenization.html
                const string DocType = "doctype";
                const string CData = "[CDATA[";

                const int MinimumBufferSize = 1024;

                readonly HtmlEntityDecoder entity = new HtmlEntityDecoder ();
                readonly CharBuffer data = new CharBuffer (2048);
                readonly CharBuffer name = new CharBuffer (32);

                readonly TextReader? textReader;
                readonly Stream? stream;
                Encoding? encoding;
                Decoder? decoder;

                readonly byte[] input;
                int inputEnd;

                readonly char[] buffer;
                int bufferIndex, bufferEnd;

                readonly char[] cdata = new char[3];
                int cdataIndex;

                string activeTagName = string.Empty;
                HtmlDocTypeToken? doctype;
                HtmlAttribute? attribute;
                HtmlTagToken? tag;
                char quote;

                bool decodeCharacterReferences = true;
                int linePosition = 1;
                int lineNumber = 1;

                bool detectByteOrderMark;
                bool isEndTag;
                bool bang;
                bool eof;

                /// <summary>
                /// Initialize a new instance of the <see cref="HtmlTokenizer"/> class.
                /// </summary>
                /// <remarks>
                /// <para>Creates a new <see cref="HtmlTokenizer"/>.</para>
                /// <para>This constructor will attempt to auto-detect the appropriate encoding to use by examining the first four bytes of the stream
                /// and, if a unicode byte-order-mark is detected, use the appropriate unicode encoding. If no byte order mark is detected, then it will
                /// default to UTF-8.</para>
                /// </remarks>
                /// <param name="stream">The input stream.</param>
                public HtmlTokenizer (Stream stream) : this (stream, Encoding.UTF8)
                {
                }

                /// <summary>
                /// Initialize a new instance of the <see cref="HtmlTokenizer"/> class.
                /// </summary>
                /// <remarks>
                /// <para>Creates a new <see cref="HtmlTokenizer"/>.</para>
                /// <para>This constructor will attempt to auto-detect the appropriate encoding to use by examining the first four bytes of the stream
                /// and, if a unicode byte-order-mark is detected, use the appropriate unicode encoding. If no byte order mark is detected, then it will
                /// default to the user-supplied encoding.</para>
                /// </remarks>
                /// <param name="stream">The input stream.</param>
                /// <param name="encoding">The charset encoding of the stream.</param>
                public HtmlTokenizer (Stream stream, Encoding encoding) : this (stream, encoding, true)
                {
                }

                /// <summary>
                /// Initialize a new instance of the <see cref="HtmlTokenizer"/> class.
                /// </summary>
                /// <remarks>
                /// <para>Creates a new <see cref="HtmlTokenizer"/>.</para>
                /// <para>This constructor allows you to change the encoding the first time you read from the <see cref="HtmlTokenizer"/>. The
                /// <paramref name="detectEncodingFromByteOrderMarks"/> parameter detects the encoding by looking at the first four bytes of the stream.
                /// It will automatically recognize UTF-8, little-endian UTF-16, big-endian UTF-16, little-endian UTF-32, and big-endian UTF-32 text if
                /// the stream starts with the appropriate byte order marks. Otherwise, the user-provided encoding is used.</para>
                /// </remarks>
                /// <param name="stream">The input stream.</param>
                /// <param name="encoding">The charset encoding of the stream.</param>
                /// <param name="detectEncodingFromByteOrderMarks"><see langword="true" /> if byte order marks should be detected and used to override the <paramref name="encoding"/>; otherwise, <see langword="false" />.</param>
                /// <param name="bufferSize">The minimum buffer size to use for reading.</param>
                public HtmlTokenizer (Stream stream, Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize = 4096)
                {
                        if (stream == null)
                                throw new ArgumentNullException (nameof (stream));

                        if (encoding == null)
                                throw new ArgumentNullException (nameof (encoding));

                        input = new byte[Math.Max (MinimumBufferSize, bufferSize)];
                        buffer = new char[input.Length];

                        if (!detectEncodingFromByteOrderMarks)
                                decoder = encoding.GetDecoder ();

                        this.detectByteOrderMark = !detectEncodingFromByteOrderMarks;
                        this.encoding = encoding;
                        this.stream = stream;
                }

                /// <summary>
                /// Initialize a new instance of the <see cref="HtmlTokenizer"/> class.
                /// </summary>
                /// <remarks>
                /// Creates a new <see cref="HtmlTokenizer"/>.
                /// </remarks>
                /// <param name="reader">The <see cref="TextReader"/>.</param>
                public HtmlTokenizer (TextReader reader)
                {
                        if (reader == null)
                                throw new ArgumentNullException (nameof (reader));

                        input = Array.Empty<byte> ();
                        buffer = new char[2048];
                        textReader = reader;
                }

                /// <summary>
                /// Get or set whether the tokenizer should decode character references.
                /// </summary>
                /// <remarks>
                /// <para>Gets or sets whether the tokenizer should decode character references.</para>
                /// <note type="warning">Character references in attribute values will still be decoded
                /// even if this value is set to <see langword="false" />.</note>
                /// </remarks>
                /// <value><see langword="true" /> if character references should be decoded; otherwise, <see langword="false" />.</value>
                public bool DecodeCharacterReferences {
                        get { return decodeCharacterReferences; }
                        set { decodeCharacterReferences = value; }
                }

                /// <summary>
                /// Get the current HTML namespace detected by the tokenizer.
                /// </summary>
                /// <remarks>
                /// Gets the current HTML namespace detected by the tokenizer.
                /// </remarks>
                /// <value>The html namespace.</value>
                public HtmlNamespace HtmlNamespace {
                        get; private set;
                }

                /// <summary>
                /// Get or set whether the tokenizer should ignore truncated tags.
                /// </summary>
                /// <remarks>
                /// <para>Gets or sets whether the tokenizer should ignore truncated tags.</para>
                /// <para>If <see langword="false" /> and the stream abruptly ends in the middle of an HTML tag, it will be
                /// treated as an <see cref="HtmlDataToken"/> instead.</para>
                /// </remarks>
                /// <value><see langword="true" /> if truncated tags should be ignored; otherwise, <see langword="false" />.</value>
                public bool IgnoreTruncatedTags {
                        get; set;
                }

                /// <summary>
                /// Get the current line number.
                /// </summary>
                /// <remarks>
                /// <para>This property is most commonly used for error reporting, but can be called
                /// at any time. The starting value for this property is <c>1</c>.</para>
                /// <para>Combined with <see cref="LinePosition"/>, a value of <c>1,1</c> indicates
                /// the start of the document.</para>
                /// </remarks>
                /// <value>The current line number.</value>
                public int LineNumber {
                        get { return lineNumber; }
                }

                /// <summary>
                /// Get the current line position.
                /// </summary>
                /// <remarks>
                /// <para>This property is most commonly used for error reporting, but can be called
                /// at any time. The starting value for this property is <c>1</c>.</para>
                /// <para>Combined with <see cref="LineNumber"/>, a value of <c>1,1</c> indicates
                /// the start of the document.</para>
                /// </remarks>
                /// <value>The column position of the current line.</value>
                public int LinePosition {
                        get { return linePosition; }
                }

                /// <summary>
                /// Get the current state of the tokenizer.
                /// </summary>
                /// <remarks>
                /// Gets the current state of the tokenizer.
                /// </remarks>
                /// <value>The current state of the tokenizer.</value>
                public HtmlTokenizerState TokenizerState {
                        get; private set;
                }

                /// <summary>
                /// Create a DOCTYPE token.
                /// </summary>
                /// <remarks>
                /// Creates a DOCTYPE token.
                /// </remarks>
                /// <returns>The DOCTYPE token.</returns>
                protected virtual HtmlDocTypeToken CreateDocType ()
                {
                        return new HtmlDocTypeToken ();
                }

                HtmlDocTypeToken CreateDocTypeToken (string rawTagName)
                {
                        var token = CreateDocType ();
                        token.RawTagName = rawTagName;
                        return token;
                }

                /// <summary>
                /// Create an HTML comment token.
                /// </summary>
                /// <remarks>
                /// Creates an HTML comment token.
                /// </remarks>
                /// <returns>The HTML comment token.</returns>
                /// <param name="comment">The comment.</param>
                /// <param name="bogus"><see langword="true" /> if the comment is bogus; otherwise, <see langword="false" />.</param>
                protected virtual HtmlCommentToken CreateCommentToken (string comment, bool bogus = false)
                {
                        return new HtmlCommentToken (comment, bogus);
                }

                /// <summary>
                /// Create an HTML character data token.
                /// </summary>
                /// <remarks>
                /// Creates an HTML character data token.
                /// </remarks>
                /// <returns>The HTML character data token.</returns>
                /// <param name="data">The character data.</param>
                protected virtual HtmlDataToken CreateDataToken (string data)
                {
                        return new HtmlDataToken (data);
                }

                /// <summary>
                /// Create an HTML character data token.
                /// </summary>
                /// <remarks>
                /// Creates an HTML character data token.
                /// </remarks>
                /// <returns>The HTML character data token.</returns>
                /// <param name="data">The character data.</param>
                protected virtual HtmlCDataToken CreateCDataToken (string data)
                {
                        return new HtmlCDataToken (data);
                }

                /// <summary>
                /// Create an HTML script data token.
                /// </summary>
                /// <remarks>
                /// Creates an HTML script data token.
                /// </remarks>
                /// <returns>The HTML script data token.</returns>
                /// <param name="data">The script data.</param>
                protected virtual HtmlScriptDataToken CreateScriptDataToken (string data)
                {
                        return new HtmlScriptDataToken (data);
                }

                /// <summary>
                /// Create an HTML tag token.
                /// </summary>
                /// <remarks>
                /// Creates an HTML tag token.
                /// </remarks>
                /// <returns>The HTML tag token.</returns>
                /// <param name="name">The tag name.</param>
                /// <param name="isEndTag"><see langword="true" /> if the tag is an end tag; otherwise, <see langword="false" />.</param>
                protected virtual HtmlTagToken CreateTagToken (string name, bool isEndTag = false)
                {
                        return new HtmlTagToken (name, isEndTag);
                }

                /// <summary>
                /// Create an attribute.
                /// </summary>
                /// <remarks>
                /// Creates an attribute.
                /// </remarks>
                /// <returns>The attribute.</returns>
                /// <param name="name">The attribute name.</param>
                protected virtual HtmlAttribute CreateAttribute (string name)
                {
                        return new HtmlAttribute (name);
                }

                [MethodImpl (MethodImplOptions.AggressiveInlining)]
                static bool IsAlphaNumeric (int c)
                {
                        return ((uint) (c - 'A') <= 'Z' - 'A') || ((uint) (c - 'a') <= 'z' - 'a') || ((uint) (c - '0') <= '9' - '0');
                }

                [MethodImpl (MethodImplOptions.AggressiveInlining)]
                static bool IsAsciiLetter (int c)
                {
                        return ((uint) (c - 'A') <= 'Z' - 'A') || ((uint) (c - 'a') <= 'z' - 'a');
                }

                [MethodImpl (MethodImplOptions.AggressiveInlining)]
                static char ToLower (int c)
                {
                        // check if the char is within the uppercase range
                        if ((uint) (c - 'A') <= 'Z' - 'A')
                                return (char) (c + 0x20);

                        return (char) c;
                }

                static int SkipByteOrderMark (byte[] input, ReadOnlySpan<byte> preamble)
                {
                        for (int i = 0; i < preamble.Length; i++) {
                                if (input[i] != preamble[i])
                                        return 0;
                        }

                        return preamble.Length;
                }

                int DetectByteOrderMark ()
                {
#if NET6_0_OR_GREATER
                        var preamble = encoding!.Preamble;
#else
                        var preamble = encoding!.GetPreamble ();
#endif

                        if (preamble.Length == 0)
                                return 0;

                        do {
                                int nread = stream!.Read (input, inputEnd, input.Length - inputEnd);

                                if (nread == 0)
                                        break;

                                inputEnd += nread;
                        } while (inputEnd < preamble.Length);

                        return SkipByteOrderMark (input, preamble);
                }

                [MemberNotNull (nameof (decoder))]
                int DetectEncodingFromByteOrderMarks ()
                {
                        do {
                                int nread = stream!.Read (input!, inputEnd, input!.Length - inputEnd);

                                if (nread == 0)
                                        break;

                                inputEnd += nread;
                        } while (inputEnd < 4);

                        int first2Bytes = inputEnd >= 2 ? input[0] << 8 | input[1] : 0;
                        int next2Bytes = inputEnd >= 4 ? (input[2] << 8 |input[3]) : 0;
                        const int UTF32BE = 12001;

                        switch (first2Bytes) {
                        case 0x0000:
                                if (next2Bytes == 0xFEFF)
                                        encoding = Encoding.GetEncoding (UTF32BE);
                                break;
                        case 0xFEFF:
                                encoding = Encoding.BigEndianUnicode;
                                break;
                        case 0xFFFE:
                                if (next2Bytes == 0x0000)
                                        encoding = Encoding.UTF32;
                                else
                                        encoding = Encoding.Unicode;
                                break;
                        case 0xEFBB:
                                if ((next2Bytes & 0xFF00) == 0xBF00)
                                        encoding = new UTF8Encoding (true, true);
                                break;
                        }

                        decoder = encoding!.GetDecoder ();

#if NET6_0_OR_GREATER
                        var preamble = encoding.Preamble;
#else
                        var preamble = encoding.GetPreamble ();
#endif

                        return SkipByteOrderMark (input, preamble);
                }

                [MethodImpl (MethodImplOptions.AggressiveInlining)]
                void FillBuffer ()
                {
                        if (bufferIndex == bufferEnd && !eof) {
                                if (stream != null) {
                                        int inputIndex;

                                        if (decoder == null) {
                                                inputIndex = DetectEncodingFromByteOrderMarks ();
                                        } else {
                                                if (detectByteOrderMark) {
                                                        inputIndex = DetectByteOrderMark ();
                                                        detectByteOrderMark = false;
                                                } else {
                                                        inputIndex = 0;
                                                }
                                        }

                                        bufferIndex = 0;
                                        bufferEnd = 0;

                                        do {
                                                if (inputIndex == inputEnd) {
                                                        inputEnd = stream.Read (input, 0, input.Length);
                                                        inputIndex = 0;
                                                }

                                                bufferEnd = decoder.GetChars (input, inputIndex, inputEnd - inputIndex, buffer, 0, inputEnd == 0);
                                                inputIndex = inputEnd;
                                        } while (bufferEnd == 0 && inputEnd > 0);

                                        inputEnd = 0;
                                } else if (textReader != null) {
                                        bufferEnd = textReader.Read (buffer, 0, buffer.Length);
                                        bufferIndex = 0;
                                } else {
                                        throw new InvalidOperationException ("No input stream or text reader has been provided.");
                                }

                                eof = bufferEnd == 0;
                        }
                }

                [MethodImpl (MethodImplOptions.AggressiveInlining)]
                bool TryPeek (out char c)
                {
                        FillBuffer ();

                        if (bufferIndex < bufferEnd) {
                                c = buffer[bufferIndex];
                                return true;
                        }

                        c = '\0';

                        return false;
                }

                [MethodImpl (MethodImplOptions.AggressiveInlining)]
                void IncrementLineNumber ()
                {
                        linePosition = 1;
                        lineNumber++;
                }

                [MethodImpl (MethodImplOptions.AggressiveInlining)]
                void ConsumeCharacter (char c)
                {
                        if (c == '\n') {
                                IncrementLineNumber ();
                        } else {
                                linePosition++;
                        }

                        bufferIndex++;
                }

                [MethodImpl (MethodImplOptions.AggressiveInlining)]
                bool TryRead (out char c)
                {
                        FillBuffer ();

                        if (bufferIndex < bufferEnd) {
                                c = buffer[bufferIndex++];

                                if (c == '\n') {
                                        IncrementLineNumber ();
                                } else {
                                        linePosition++;
                                }

                                return true;
                        }

                        c = '\0';

                        return false;
                }

                bool NameIs (string value)
                {
                        if (name.Length != value.Length)
                                return false;

                        for (int i = 0; i < name.Length; i++) {
                                if (ToLower (name[i]) != ToLower (value[i]))
                                        return false;
                        }

                        return true;
                }

                void EmitTagAttribute ()
                {
                        attribute = CreateAttribute (name.ToString ());
                        tag!.Attributes.Add (attribute);
                        name.Length = 0;
                }

                HtmlToken EmitCommentToken (string comment, bool bogus = false)
                {
                        var token = CreateCommentToken (comment, bogus);
                        token.IsBangComment = bang;
                        data.Length = 0;
                        name.Length = 0;
                        bang = false;
                        return token;
                }

                HtmlToken EmitCommentToken (CharBuffer comment, bool bogus = false)
                {
                        return EmitCommentToken (comment.ToString (), bogus);
                }

                HtmlToken? EmitDocType ()
                {
                        var token = doctype;
                        data.Length = 0;
                        doctype = null;
                        return token;
                }

                HtmlToken? EmitDataToken (bool encodeEntities, bool truncated)
                {
                        if (data.Length == 0)
                                return null;

                        if (truncated && IgnoreTruncatedTags) {
                                data.Length = 0;
                                return null;
                        }

                        var token = CreateDataToken (data.ToString ());
                        token.EncodeEntities = encodeEntities;
                        data.Length = 0;

                        return token;
                }

                HtmlToken? EmitCDataToken ()
                {
                        if (data.Length == 0)
                                return null;

                        var token = CreateCDataToken (data.ToString ());
                        data.Length = 0;

                        return token;
                }

                HtmlToken? EmitScriptDataToken ()
                {
                        if (data.Length == 0)
                                return null;

                        var token = CreateScriptDataToken (data.ToString ());
                        data.Length = 0;

                        return token;
                }

                HtmlToken EmitTagToken ()
                {
                        if (!tag!.IsEndTag && !tag.IsEmptyElement) {
                                switch (tag.Id) {
                                case HtmlTagId.Style: case HtmlTagId.Xmp: case HtmlTagId.IFrame: case HtmlTagId.NoEmbed: case HtmlTagId.NoFrames:
                                        TokenizerState = HtmlTokenizerState.RawText;
                                        activeTagName = tag.Name;
                                        break;
                                case HtmlTagId.Title: case HtmlTagId.TextArea:
                                        TokenizerState = HtmlTokenizerState.RcData;
                                        activeTagName = tag.Name;
                                        break;
                                case HtmlTagId.PlainText:
                                        TokenizerState = HtmlTokenizerState.PlainText;
                                        break;
                                case HtmlTagId.Script:
                                        TokenizerState = HtmlTokenizerState.ScriptData;
                                        break;
                                case HtmlTagId.NoScript:
                                        // TODO: only switch into the RawText state if scripting is enabled
                                        TokenizerState = HtmlTokenizerState.RawText;
                                        activeTagName = tag.Name;
                                        break;
                                case HtmlTagId.Html:
                                        TokenizerState = HtmlTokenizerState.Data;

                                        for (int i = tag.Attributes.Count; i > 0; i--) {
                                                var attr = tag.Attributes[i - 1];

                                                if (attr.Id == HtmlAttributeId.XmlNS && attr.Value != null) {
                                                        HtmlNamespace = attr.Value.ToHtmlNamespace ();
                                                        break;
                                                }
                                        }
                                        break;
                                default:
                                        TokenizerState = HtmlTokenizerState.Data;
                                        break;
                                }
                        } else {
                                TokenizerState = HtmlTokenizerState.Data;
                        }

                        var token = tag;
                        data.Length = 0;
                        tag = null;

                        return token;
                }

                // 8.2.4.69 Tokenizing character references
                HtmlToken? ReadCharacterReference (HtmlTokenizerState next)
                {
                        if (!TryPeek (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                data.Append ('&');

                                return EmitDataToken (true, false);
                        }

                        switch (c) {
                        case '\t': case '\r': case '\n': case '\f': case ' ': case '<': case '&':
                                // no character is consumed, emit '&'
                                TokenizerState = next;
                                data.Append ('&');
                                return null;
                        }

                        entity.Push ('&');

                        while (entity.Push (c)) {
                                ConsumeCharacter (c);

                                if (c == ';')
                                        break;

                                if (!TryPeek (out c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        data.Append (entity.GetPushedInput ());
                                        entity.Reset ();

                                        return EmitDataToken (true, false);
                                }
                        }

                        TokenizerState = next;

                        data.Append (entity.GetValue ());
                        entity.Reset ();

                        return null;
                }

                HtmlToken? ReadGenericRawTextLessThan (HtmlTokenizerState rawText, HtmlTokenizerState rawTextEndTagOpen)
                {
                        data.Append ('<');

                        if (TryPeek (out char c) && c == '/') {
                                TokenizerState = rawTextEndTagOpen;
                                ConsumeCharacter (c);
                                data.Append ('/');
                                name.Length = 0;
                        } else {
                                TokenizerState = rawText;
                        }

                        return null;
                }

                HtmlToken? ReadGenericRawTextEndTagOpen (bool decoded, HtmlTokenizerState rawText, HtmlTokenizerState rawTextEndTagName)
                {
                        if (!TryPeek (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitDataToken (decoded, true);
                        }

                        if (IsAsciiLetter (c)) {
                                TokenizerState = rawTextEndTagName;
                                ConsumeCharacter (c);
                                name.Append (c);
                                data.Append (c);
                        } else {
                                TokenizerState = rawText;
                        }

                        return null;
                }

                HtmlToken? ReadGenericRawTextEndTagName (bool decoded, HtmlTokenizerState rawText)
                {
                        var current = TokenizerState;

                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        name.Length = 0;

                                        return EmitDataToken (decoded, true);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        if (NameIs (activeTagName)) {
                                                TokenizerState = HtmlTokenizerState.BeforeAttributeName;
                                                break;
                                        }

                                        goto default;
                                case '/':
                                        if (NameIs (activeTagName)) {
                                                TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                                break;
                                        }
                                        goto default;
                                case '>':
                                        if (NameIs (activeTagName)) {
                                                var token = CreateTagToken (name.ToString (), true);
                                                TokenizerState = HtmlTokenizerState.Data;
                                                data.Length = 0;
                                                name.Length = 0;
                                                return token;
                                        }
                                        goto default;
                                default:
                                        if (!IsAsciiLetter (c)) {
                                                TokenizerState = rawText;
                                                return null;
                                        }

                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == current);

                        tag = CreateTagToken (name.ToString (), true);
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.1 Data state
                HtmlToken? ReadData ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        break;
                                }

                                switch (c) {
                                case '&':
                                        if (DecodeCharacterReferences) {
                                                TokenizerState = HtmlTokenizerState.CharacterReferenceInData;
                                                return null;
                                        }

                                        goto default;
                                case '<':
                                        TokenizerState = HtmlTokenizerState.TagOpen;
                                        break;
                                //case 0: // parse error, but emit it anyway
                                default:
                                        data.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.Data);

                        return EmitDataToken (DecodeCharacterReferences, false);
                }

                // 8.2.4.2 Character reference in data state
                HtmlToken? ReadCharacterReferenceInData ()
                {
                        return ReadCharacterReference (HtmlTokenizerState.Data);
                }

                // 8.2.4.3 RCDATA state
                HtmlToken? ReadRcData ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        break;
                                }

                                switch (c) {
                                case '&':
                                        if (DecodeCharacterReferences) {
                                                TokenizerState = HtmlTokenizerState.CharacterReferenceInRcData;
                                                return null;
                                        }

                                        goto default;
                                case '<':
                                        TokenizerState = HtmlTokenizerState.RcDataLessThan;
                                        return EmitDataToken (DecodeCharacterReferences, false);
                                default:
                                        data.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.RcData);

                        return EmitDataToken (DecodeCharacterReferences, false);
                }

                // 8.2.4.4 Character reference in RCDATA state
                HtmlToken? ReadCharacterReferenceInRcData ()
                {
                        return ReadCharacterReference (HtmlTokenizerState.RcData);
                }

                // 8.2.4.5 RAWTEXT state
                HtmlToken? ReadRawText ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        break;
                                }

                                switch (c) {
                                case '<':
                                        TokenizerState = HtmlTokenizerState.RawTextLessThan;
                                        return EmitDataToken (false, false);
                                default:
                                        data.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.RawText);

                        return EmitDataToken (false, false);
                }

                // 8.2.4.6 Script data state
                HtmlToken? ReadScriptData ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        break;
                                }

                                switch (c) {
                                case '<':
                                        TokenizerState = HtmlTokenizerState.ScriptDataLessThan;
                                        break;
                                default:
                                        data.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptData);

                        return EmitScriptDataToken ();
                }

                // 8.2.4.7 PLAINTEXT state
                HtmlToken? ReadPlainText ()
                {
                        do {
                                while (bufferIndex < bufferEnd) {
                                        char c = buffer[bufferIndex++];

                                        linePosition++;

                                        switch (c) {
                                        case '\0':
                                                data.Append ('\uFFFD');
                                                break;
                                        case '\n':
                                                IncrementLineNumber ();
                                                goto default;
                                        default:
                                                data.Append (c);
                                                break;
                                        }
                                }

                                FillBuffer ();
                        } while (!eof);

                        TokenizerState = HtmlTokenizerState.EndOfFile;

                        return EmitDataToken (false, false);
                }

                // 8.2.4.8 Tag open state
                HtmlToken? ReadTagOpen ()
                {
                        if (!TryRead (out char c)) {
                                var token = IgnoreTruncatedTags ? null : CreateDataToken ("<");
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return token;
                        }

                        // Note: we save the data in case we hit a parse error and have to emit a data token
                        data.Append ('<');
                        data.Append (c);

                        switch (c) {
                        case '!':
                                TokenizerState = HtmlTokenizerState.MarkupDeclarationOpen;
                                break;
                        case '?':
                                TokenizerState = HtmlTokenizerState.BogusComment;
                                data.Length = 1;
                                data[0] = c;
                                break;
                        case '/':
                                TokenizerState = HtmlTokenizerState.EndTagOpen;
                                break;
                        default:
                                if (IsAsciiLetter (c)) {
                                        TokenizerState = HtmlTokenizerState.TagName;
                                        isEndTag = false;
                                        name.Append (c);
                                } else {
                                        TokenizerState = HtmlTokenizerState.Data;
                                }
                                break;
                        }

                        return null;
                }

                // 8.2.4.9 End tag open state
                HtmlToken? ReadEndTagOpen ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitDataToken (false, true);
                        }

                        // Note: we save the data in case we hit a parse error and have to emit a data token
                        data.Append (c);

                        switch (c) {
                        case '>': // parse error
                                TokenizerState = HtmlTokenizerState.Data;
                                data.Length = 0; // FIXME: this is probably wrong
                                break;
                        default:
                                if (IsAsciiLetter (c)) {
                                        TokenizerState = HtmlTokenizerState.TagName;
                                        isEndTag = true;
                                        name.Append (c);
                                } else {
                                        TokenizerState = HtmlTokenizerState.BogusComment;
                                        data.Length = 1;
                                        data[0] = c;
                                }
                                break;
                        }

                        return null;
                }

                // 8.2.4.10 Tag name state
                HtmlToken? ReadTagName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        name.Length = 0;

                                        return EmitDataToken (false, true);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        TokenizerState = HtmlTokenizerState.BeforeAttributeName;
                                        break;
                                case '/':
                                        TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                        break;
                                case '>':
                                        tag = CreateTagToken (name.ToString (), isEndTag);
                                        data.Length = 0;
                                        name.Length = 0;

                                        return EmitTagToken ();
                                default:
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.TagName);

                        tag = CreateTagToken (name.ToString (), isEndTag);
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.11 RCDATA less-than sign state
                HtmlToken? ReadRcDataLessThan ()
                {
                        return ReadGenericRawTextLessThan (HtmlTokenizerState.RcData, HtmlTokenizerState.RcDataEndTagOpen);
                }

                // 8.2.4.12 RCDATA end tag open state
                HtmlToken? ReadRcDataEndTagOpen ()
                {
                        return ReadGenericRawTextEndTagOpen (DecodeCharacterReferences, HtmlTokenizerState.RcData, HtmlTokenizerState.RcDataEndTagName);
                }

                // 8.2.4.13 RCDATA end tag name state
                HtmlToken? ReadRcDataEndTagName ()
                {
                        return ReadGenericRawTextEndTagName (DecodeCharacterReferences, HtmlTokenizerState.RcData);
                }

                // 8.2.4.14 RAWTEXT less-than sign state
                HtmlToken? ReadRawTextLessThan ()
                {
                        return ReadGenericRawTextLessThan (HtmlTokenizerState.RawText, HtmlTokenizerState.RawTextEndTagOpen);
                }

                // 8.2.4.15 RAWTEXT end tag open state
                HtmlToken? ReadRawTextEndTagOpen ()
                {
                        return ReadGenericRawTextEndTagOpen (false, HtmlTokenizerState.RawText, HtmlTokenizerState.RawTextEndTagName);
                }

                // 8.2.4.16 RAWTEXT end tag name state
                HtmlToken? ReadRawTextEndTagName ()
                {
                        return ReadGenericRawTextEndTagName (false, HtmlTokenizerState.RawText);
                }

                // 8.2.4.17 Script data less-than sign state
                HtmlToken? ReadScriptDataLessThan ()
                {
                        data.Append ('<');

                        if (TryPeek (out char c) && c == '/') {
                                TokenizerState = HtmlTokenizerState.ScriptDataEndTagOpen;
                                ConsumeCharacter (c);
                                data.Append ('/');
                                name.Length = 0;
                        } else if (c == '!') {
                                TokenizerState = HtmlTokenizerState.ScriptDataEscapeStart;
                                ConsumeCharacter (c);
                                data.Append ('!');
                        } else {
                                TokenizerState = HtmlTokenizerState.ScriptData;
                        }

                        return null;
                }

                // 8.2.4.18 Script data end tag open state
                HtmlToken? ReadScriptDataEndTagOpen ()
                {
                        if (!TryPeek (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitScriptDataToken ();
                        }

                        if (c == 'S' || c == 's') {
                                TokenizerState = HtmlTokenizerState.ScriptDataEndTagName;
                                ConsumeCharacter (c);
                                name.Append ('s');
                                data.Append (c);
                        } else {
                                TokenizerState = HtmlTokenizerState.ScriptData;
                        }

                        return null;
                }

                // 8.2.4.19 Script data end tag name state
                HtmlToken? ReadScriptDataEndTagName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        name.Length = 0;

                                        return EmitScriptDataToken ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        if (NameIs ("script")) {
                                                TokenizerState = HtmlTokenizerState.BeforeAttributeName;
                                                break;
                                        }
                                        goto default;
                                case '/':
                                        if (NameIs ("script")) {
                                                TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                                break;
                                        }
                                        goto default;
                                case '>':
                                        if (NameIs ("script")) {
                                                var token = CreateTagToken (name.ToString (), true);
                                                TokenizerState = HtmlTokenizerState.Data;
                                                data.Length = 0;
                                                name.Length = 0;
                                                return token;
                                        }
                                        goto default;
                                default:
                                        if (!IsAsciiLetter (c)) {
                                                TokenizerState = HtmlTokenizerState.ScriptData;
                                                name.Length = 0;
                                                return null;
                                        }

                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptDataEndTagName);

                        tag = CreateTagToken (name.ToString (), true);
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.20 Script data escape start state
                HtmlToken? ReadScriptDataEscapeStart ()
                {
                        if (TryPeek (out char c) && c == '-') {
                                TokenizerState = HtmlTokenizerState.ScriptDataEscapeStartDash;
                                ConsumeCharacter (c);
                                data.Append ('-');
                        } else {
                                TokenizerState = HtmlTokenizerState.ScriptData;
                        }

                        return null;
                }

                // 8.2.4.21 Script data escape start dash state
                HtmlToken? ReadScriptDataEscapeStartDash ()
                {
                        if (TryPeek (out char c) && c == '-') {
                                TokenizerState = HtmlTokenizerState.ScriptDataEscapedDashDash;
                                ConsumeCharacter (c);
                                data.Append ('-');
                        } else {
                                TokenizerState = HtmlTokenizerState.ScriptData;
                        }

                        return null;
                }

                // 8.2.4.22 Script data escaped state
                HtmlToken? ReadScriptDataEscaped ()
                {
                        HtmlToken? token = null;

                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        return EmitScriptDataToken ();
                                }

                                switch (c) {
                                case '-':
                                        TokenizerState = HtmlTokenizerState.ScriptDataEscapedDash;
                                        data.Append ('-');
                                        break;
                                case '<':
                                        TokenizerState = HtmlTokenizerState.ScriptDataEscapedLessThan;
                                        token = EmitScriptDataToken ();
                                        data.Append ('<');
                                        break;
                                default:
                                        data.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptDataEscaped);

                        return token;
                }

                // 8.2.4.23 Script data escaped dash state
                HtmlToken? ReadScriptDataEscapedDash ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitScriptDataToken ();
                        }

                        HtmlToken? token = null;

                        switch (c) {
                        case '-':
                                TokenizerState = HtmlTokenizerState.ScriptDataEscapedDashDash;
                                data.Append ('-');
                                break;
                        case '<':
                                TokenizerState = HtmlTokenizerState.ScriptDataEscapedLessThan;
                                token = EmitScriptDataToken ();
                                data.Append ('<');
                                break;
                        default:
                                TokenizerState = HtmlTokenizerState.ScriptDataEscaped;
                                data.Append (c == '\0' ? '\uFFFD' : c);
                                break;
                        }

                        return token;
                }

                // 8.2.4.24 Script data escaped dash dash state
                HtmlToken? ReadScriptDataEscapedDashDash ()
                {
                        HtmlToken? token = null;

                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        return EmitScriptDataToken ();
                                }

                                switch (c) {
                                case '-':
                                        data.Append ('-');
                                        break;
                                case '<':
                                        TokenizerState = HtmlTokenizerState.ScriptDataEscapedLessThan;
                                        token = EmitScriptDataToken ();
                                        data.Append ('<');
                                        break;
                                case '>':
                                        TokenizerState = HtmlTokenizerState.ScriptData;
                                        data.Append ('>');
                                        break;
                                default:
                                        TokenizerState = HtmlTokenizerState.ScriptDataEscaped;
                                        data.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptDataEscapedDashDash);

                        return token;
                }

                // 8.2.4.25 Script data escaped less-than sign state
                HtmlToken? ReadScriptDataEscapedLessThan ()
                {
                        if (!TryPeek (out char c)) {
                                TokenizerState = HtmlTokenizerState.ScriptDataEscaped;
                                return null;
                        }

                        if (c == '/') {
                                TokenizerState = HtmlTokenizerState.ScriptDataEscapedEndTagOpen;
                                ConsumeCharacter (c);
                                data.Append (c);
                                name.Length = 0;
                        } else if (IsAsciiLetter (c)) {
                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscapeStart;
                                ConsumeCharacter (c);
                                data.Append (c);
                                name.Append (c);
                        } else {
                                TokenizerState = HtmlTokenizerState.ScriptDataEscaped;
                        }

                        return null;
                }

                // 8.2.4.26 Script data escaped end tag open state
                HtmlToken? ReadScriptDataEscapedEndTagOpen ()
                {
                        if (!TryPeek (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitScriptDataToken ();
                        }

                        if (IsAsciiLetter (c)) {
                                TokenizerState = HtmlTokenizerState.ScriptDataEscapedEndTagName;
                                ConsumeCharacter (c);
                                data.Append (c);
                                name.Append (c);
                        } else {
                                TokenizerState = HtmlTokenizerState.ScriptDataEscaped;
                        }

                        return null;
                }

                // 8.2.4.27 Script data escaped end tag name state
                HtmlToken? ReadScriptDataEscapedEndTagName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        name.Length = 0;

                                        return EmitScriptDataToken ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        if (NameIs ("script")) {
                                                TokenizerState = HtmlTokenizerState.BeforeAttributeName;
                                                break;
                                        }

                                        goto default;
                                case '/':
                                        if (NameIs ("script")) {
                                                TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                                break;
                                        }
                                        goto default;
                                case '>':
                                        if (NameIs ("script")) {
                                                var token = CreateTagToken (name.ToString (), true);
                                                TokenizerState = HtmlTokenizerState.Data;
                                                data.Length = 0;
                                                name.Length = 0;
                                                return token;
                                        }
                                        goto default;
                                default:
                                        if (!IsAsciiLetter (c)) {
                                                TokenizerState = HtmlTokenizerState.ScriptData;
                                                return null;
                                        }

                                        name.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptDataEscapedEndTagName);

                        tag = CreateTagToken (name.ToString (), true);
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.28 Script data double escape start state
                HtmlToken? ReadScriptDataDoubleEscapeStart ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        name.Length = 0;

                                        return EmitScriptDataToken ();
                                }

                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ': case '/': case '>':
                                        if (NameIs ("script"))
                                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscaped;
                                        else
                                                TokenizerState = HtmlTokenizerState.ScriptDataEscaped;
                                        name.Length = 0;
                                        break;
                                default:
                                        if (!IsAsciiLetter (c))
                                                TokenizerState = HtmlTokenizerState.ScriptDataEscaped;
                                        else
                                                name.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptDataDoubleEscapeStart);

                        return null;
                }

                // 8.2.4.29 Script data double escaped state
                HtmlToken? ReadScriptDataDoubleEscaped ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        return EmitScriptDataToken ();
                                }

                                switch (c) {
                                case '-':
                                        TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscapedDash;
                                        data.Append ('-');
                                        break;
                                case '<':
                                        TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscapedLessThan;
                                        data.Append ('<');
                                        break;
                                default:
                                        data.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptDataEscaped);

                        return null;
                }

                // 8.2.4.30 Script data double escaped dash state
                HtmlToken? ReadScriptDataDoubleEscapedDash ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitScriptDataToken ();
                        }

                        switch (c) {
                        case '-':
                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscapedDashDash;
                                data.Append ('-');
                                break;
                        case '<':
                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscapedLessThan;
                                data.Append ('<');
                                break;
                        default:
                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscaped;
                                data.Append (c == '\0' ? '\uFFFD' : c);
                                break;
                        }

                        return null;
                }

                // 8.2.4.31 Script data double escaped dash dash state
                HtmlToken? ReadScriptDataDoubleEscapedDashDash ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        return EmitScriptDataToken ();
                                }

                                switch (c) {
                                case '-':
                                        data.Append ('-');
                                        break;
                                case '<':
                                        TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscapedLessThan;
                                        data.Append ('<');
                                        break;
                                case '>':
                                        TokenizerState = HtmlTokenizerState.ScriptData;
                                        data.Append ('>');
                                        break;
                                default:
                                        TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscaped;
                                        data.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptDataEscapedDashDash);

                        return null;
                }

                // 8.2.4.32 Script data double escaped less-than sign state
                HtmlToken? ReadScriptDataDoubleEscapedLessThan ()
                {
                        if (TryPeek (out char c) && c == '/') {
                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscapeEnd;
                                ConsumeCharacter (c);
                                data.Append ('/');
                        } else {
                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscaped;
                        }

                        return null;
                }

                // 8.2.4.33 Script data double escape end state
                HtmlToken? ReadScriptDataDoubleEscapeEnd ()
                {
                        do {
                                TryPeek (out char c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ': case '/': case '>':
                                        if (NameIs ("script"))
                                                TokenizerState = HtmlTokenizerState.ScriptDataEscaped;
                                        else
                                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscaped;
                                        ConsumeCharacter (c);
                                        data.Append (c);
                                        break;
                                default:
                                        if (!IsAsciiLetter (c)) {
                                                // Note: EOF also hits this case.
                                                TokenizerState = HtmlTokenizerState.ScriptDataDoubleEscaped;
                                        } else {
                                                ConsumeCharacter (c);
                                                name.Append (c);
                                                data.Append (c);
                                        }
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.ScriptDataDoubleEscapeEnd);

                        return null;
                }

                // 8.2.4.34 Before attribute name state
                HtmlToken? ReadBeforeAttributeName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        tag = null;

                                        return EmitDataToken (false, true);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '/':
                                        TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                        return null;
                                case '>':
                                        return EmitTagToken ();
                                case '"': case '\'': case '<': case '=':
                                        // parse error
                                        goto default;
                                default:
                                        TokenizerState = HtmlTokenizerState.AttributeName;
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.35 Attribute name state
                HtmlToken? ReadAttributeName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        name.Length = 0;
                                        tag = null;

                                        return EmitDataToken (false, true);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        TokenizerState = HtmlTokenizerState.AfterAttributeName;
                                        break;
                                case '/':
                                        TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                        break;
                                case '=':
                                        TokenizerState = HtmlTokenizerState.BeforeAttributeValue;
                                        break;
                                case '>':
                                        EmitTagAttribute ();

                                        return EmitTagToken ();
                                default:
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.AttributeName);

                        EmitTagAttribute ();

                        return null;
                }

                // 8.2.4.36 After attribute name state
                HtmlToken? ReadAfterAttributeName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        tag = null;

                                        return EmitDataToken (false, true);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '/':
                                        TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                        return null;
                                case '=':
                                        TokenizerState = HtmlTokenizerState.BeforeAttributeValue;
                                        return null;
                                case '>':
                                        return EmitTagToken ();
                                case '"': case '\'': case '<':
                                        // parse error
                                        goto default;
                                default:
                                        TokenizerState = HtmlTokenizerState.AttributeName;
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.37 Before attribute value state
                HtmlToken? ReadBeforeAttributeValue ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        tag = null;

                                        return EmitDataToken (false, true);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '"': case '\'':
                                        TokenizerState = HtmlTokenizerState.AttributeValueQuoted;
                                        quote = c;
                                        return null;
                                case '&':
                                        TokenizerState = HtmlTokenizerState.CharacterReferenceInAttributeValue;
                                        return null;
                                case '/':
                                        TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                        return null;
                                case '>':
                                        return EmitTagToken ();
                                case '<': case '=': case '`':
                                        // parse error
                                        goto default;
                                default:
                                        TokenizerState = HtmlTokenizerState.AttributeValueUnquoted;
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.38 Attribute value (double-quoted) state
                HtmlToken? ReadAttributeValueQuoted ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        name.Length = 0;

                                        return EmitDataToken (false, true);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '&':
                                        TokenizerState = HtmlTokenizerState.CharacterReferenceInAttributeValue;
                                        return null;
                                case '\0':
                                        name.Append ('\uFFFD');
                                        break;
                                default:
                                        if (c == quote) {
                                                TokenizerState = HtmlTokenizerState.AfterAttributeValueQuoted;
                                                quote = '\0';
                                                break;
                                        }

                                        name.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.AttributeValueQuoted);

                        attribute!.Value = name.ToString ();
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.40 Attribute value (unquoted) state
                HtmlToken? ReadAttributeValueUnquoted ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        name.Length = 0;

                                        return EmitDataToken (false, true);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        TokenizerState = HtmlTokenizerState.BeforeAttributeName;
                                        break;
                                case '&':
                                        TokenizerState = HtmlTokenizerState.CharacterReferenceInAttributeValue;
                                        return null;
                                case '>':
                                        attribute!.Value = name.ToString ();
                                        name.Length = 0;

                                        return EmitTagToken ();
                                case '\'': case '<': case '=': case '`':
                                        // parse error
                                        goto default;
                                default:
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.AttributeValueUnquoted);

                        attribute!.Value = name.ToString ();
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.41 Character reference in attribute value state
                HtmlToken? ReadCharacterReferenceInAttributeValue ()
                {
                        char additionalAllowedCharacter = quote == '\0' ? '>' : quote;

                        if (!TryPeek (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                name.Length = 0;

                                return EmitDataToken (false, true);
                        }

                        switch (c) {
                        case '\t': case '\r': case '\n': case '\f': case ' ': case '<': case '&':
                                // no character is consumed, emit '&'
                                name.Append ('&');
                                break;
                        default:
                                if (c == additionalAllowedCharacter) {
                                        // this is not a character reference, nothing is consumed
                                        name.Append ('&');
                                        break;
                                }

                                entity.Push ('&');

                                while (entity.Push (c)) {
                                        ConsumeCharacter (c);

                                        if (c == ';')
                                                break;

                                        if (!TryPeek (out c)) {
                                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                                data.Length--;
                                                data.Append (entity.GetPushedInput ());
                                                entity.Reset ();

                                                return EmitDataToken (false, true);
                                        }
                                }

                                var pushed = entity.GetPushedInput ();
                                string value;

                                if (c == '=' || IsAlphaNumeric (c))
                                        value = pushed;
                                else
                                        value = entity.GetValue ();

                                data.Length--;
                                data.Append (pushed);
                                name.Append (value);
                                entity.Reset ();
                                break;
                        }

                        if (quote == '\0')
                                TokenizerState = HtmlTokenizerState.AttributeValueUnquoted;
                        else
                                TokenizerState = HtmlTokenizerState.AttributeValueQuoted;

                        return null;
                }

                // 8.2.4.42 After attribute value (quoted) state
                HtmlToken? ReadAfterAttributeValueQuoted ()
                {
                        HtmlToken? token = null;

                        if (!TryPeek (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitDataToken (false, true);
                        }

                        switch (c) {
                        case '\t': case '\r': case '\n': case '\f': case ' ':
                                TokenizerState = HtmlTokenizerState.BeforeAttributeName;
                                ConsumeCharacter (c);
                                data.Append (c);
                                break;
                        case '/':
                                TokenizerState = HtmlTokenizerState.SelfClosingStartTag;
                                ConsumeCharacter (c);
                                data.Append (c);
                                break;
                        case '>':
                                ConsumeCharacter (c);
                                token = EmitTagToken ();
                                break;
                        default:
                                TokenizerState = HtmlTokenizerState.BeforeAttributeName;
                                break;
                        }

                        return token;
                }

                // 8.2.4.43 Self-closing start tag state
                HtmlToken? ReadSelfClosingStartTag ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitDataToken (false, true);
                        }

                        if (c == '>') {
                                tag!.IsEmptyElement = true;

                                return EmitTagToken ();
                        }

                        // parse error
                        TokenizerState = HtmlTokenizerState.BeforeAttributeName;

                        // Note: we save the data in case we hit a parse error and have to emit a data token
                        data.Append (c);

                        return null;
                }

                // 8.2.4.44 Bogus comment state
                HtmlToken ReadBogusComment ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        break;
                                }

                                if (c == '>')
                                        break;

                                data.Append (c == '\0' ? '\uFFFD' : c);
                        } while (true);

                        TokenizerState = HtmlTokenizerState.Data;

                        return EmitCommentToken (data, true);
                }

                // 8.2.4.45 Markup declaration open state
                HtmlToken? ReadMarkupDeclarationOpen ()
                {
                        int count = 0;
                        char c = '\0';

                        while (count < 2) {
                                if (!TryPeek (out c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        return EmitDataToken (false, true);
                                }

                                if (c != '-')
                                        break;

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                ConsumeCharacter (c);
                                data.Append (c);
                                count++;
                        }

                        if (count == 2) {
                                // "<!--"
                                TokenizerState = HtmlTokenizerState.CommentStart;
                                name.Length = 0;
                                return null;
                        }

                        if (count == 0) {
                                // Check for "<!DOCTYPE " or "<![CDATA["
                                if (c == 'D' || c == 'd') {
                                        // Note: we save the data in case we hit a parse error and have to emit a data token
                                        ConsumeCharacter (c);
                                        data.Append (c);
                                        name.Append (c);
                                        count = 1;

                                        while (count < 7) {
                                                if (!TryRead (out c)) {
                                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                                        return EmitDataToken (false, true);
                                                }

                                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                                data.Append (c);
                                                name.Append (c);

                                                if (ToLower (c) != DocType[count])
                                                        break;

                                                count++;
                                        }

                                        if (count == 7) {
                                                doctype = CreateDocTypeToken (name.ToString ());
                                                TokenizerState = HtmlTokenizerState.DocType;
                                                name.Length = 0;
                                                return null;
                                        }

                                        name.Length = 0;
                                } else if (c == '[') {
                                        // Note: we save the data in case we hit a parse error and have to emit a data token
                                        ConsumeCharacter (c);
                                        data.Append (c);
                                        count = 1;

                                        while (count < 7) {
                                                if (!TryRead (out c)) {
                                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                                        return EmitDataToken (false, true);
                                                }

                                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                                data.Append (c);

                                                if (c != CData[count])
                                                        break;

                                                count++;
                                        }

                                        if (count == 7) {
                                                TokenizerState = HtmlTokenizerState.CDataSection;
                                                data.Length = 0;
                                                return null;
                                        }
                                }
                        }

                        // parse error
                        TokenizerState = HtmlTokenizerState.BogusComment;

                        // trim the leading "<!"
                        for (int i = 0; i < data.Length - 2; i++)
                                data[i] = data[i + 2];
                        data.Length -= 2;
                        bang = true;

                        return null;
                }

                // 8.2.4.46 Comment start state
                HtmlToken? ReadCommentStart ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.Data;

                                return EmitCommentToken (string.Empty);
                        }

                        data.Append (c);

                        switch (c) {
                        case '-':
                                TokenizerState = HtmlTokenizerState.CommentStartDash;
                                break;
                        case '>': // parse error
                                TokenizerState = HtmlTokenizerState.Data;
                                return EmitCommentToken (string.Empty);
                        default:
                                TokenizerState = HtmlTokenizerState.Comment;
                                name.Append (c == '\0' ? '\uFFFD' : c);
                                break;
                        }

                        return null;
                }

                // 8.2.4.47 Comment start dash state
                HtmlToken? ReadCommentStartDash ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.Data;
                                return EmitCommentToken (name);
                        }

                        data.Append (c);

                        switch (c) {
                        case '-':
                                TokenizerState = HtmlTokenizerState.CommentEnd;
                                break;
                        case '>': // parse error
                                TokenizerState = HtmlTokenizerState.Data;
                                return EmitCommentToken (name);
                        default:
                                TokenizerState = HtmlTokenizerState.Comment;
                                name.Append ('-');
                                name.Append (c == '\0' ? '\uFFFD' : c);
                                break;
                        }

                        return null;
                }

                // 8.2.4.48 Comment state
                HtmlToken? ReadComment ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        return EmitCommentToken (name);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '-':
                                        TokenizerState = HtmlTokenizerState.CommentEndDash;
                                        return null;
                                default:
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        break;
                                }
                        } while (true);
                }

                // 8.2.4.49 Comment end dash state
                HtmlToken? ReadCommentEndDash ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.Data;
                                return EmitCommentToken (name);
                        }

                        data.Append (c);

                        switch (c) {
                        case '-':
                                TokenizerState = HtmlTokenizerState.CommentEnd;
                                break;
                        default:
                                TokenizerState = HtmlTokenizerState.Comment;
                                name.Append ('-');
                                name.Append (c == '\0' ? '\uFFFD' : c);
                                break;
                        }

                        return null;
                }

                // 8.2.4.50 Comment end state
                HtmlToken? ReadCommentEnd ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        return EmitCommentToken (name);
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '>':
                                        TokenizerState = HtmlTokenizerState.Data;
                                        return EmitCommentToken (name);
                                case '!': // parse error
                                        TokenizerState = HtmlTokenizerState.CommentEndBang;
                                        return null;
                                case '-':
                                        name.Append ('-');
                                        break;
                                default:
                                        TokenizerState = HtmlTokenizerState.Comment;
                                        name.Append ("--");
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.51 Comment end bang state
                HtmlToken? ReadCommentEndBang ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                return EmitCommentToken (name);
                        }

                        data.Append (c);

                        switch (c) {
                        case '-':
                                TokenizerState = HtmlTokenizerState.CommentEndDash;
                                name.Append ("--!");
                                break;
                        case '>':
                                TokenizerState = HtmlTokenizerState.Data;
                                return EmitCommentToken (name);
                        default: // parse error
                                TokenizerState = HtmlTokenizerState.Comment;
                                name.Append ("--!");
                                name.Append (c == '\0' ? '\uFFFD' : c);
                                break;
                        }

                        return null;
                }

                // 8.2.4.52 DOCTYPE state
                HtmlToken? ReadDocType ()
                {
                        if (!TryPeek (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                doctype!.ForceQuirksMode = true;
                                name.Length = 0;

                                return EmitDocType ();
                        }

                        TokenizerState = HtmlTokenizerState.BeforeDocTypeName;

                        switch (c) {
                        case '\t': case '\r': case '\n': case '\f': case ' ':
                                ConsumeCharacter (c);
                                data.Append (c);
                                break;
                        }

                        return null;
                }

                // 8.2.4.53 Before DOCTYPE name state
                HtmlToken? ReadBeforeDocTypeName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '>':
                                        TokenizerState = HtmlTokenizerState.Data;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                default:
                                        TokenizerState = HtmlTokenizerState.DocTypeName;
                                        name.Append (c == '\0' ? '\uFFFD' : c);
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.54 DOCTYPE name state
                HtmlToken? ReadDocTypeName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.Name = name.ToString ();
                                        doctype.ForceQuirksMode = true;
                                        name.Length = 0;

                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        TokenizerState = HtmlTokenizerState.AfterDocTypeName;
                                        break;
                                case '>':
                                        TokenizerState = HtmlTokenizerState.Data;
                                        doctype!.Name = name.ToString ();
                                        name.Length = 0;

                                        return EmitDocType ();
                                case '\0':
                                        name.Append ('\uFFFD');
                                        break;
                                default:
                                        name.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.DocTypeName);

                        doctype!.Name = name.ToString ();
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.55 After DOCTYPE name state
                HtmlToken? ReadAfterDocTypeName ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '>':
                                        TokenizerState = HtmlTokenizerState.Data;
                                        return EmitDocType ();
                                default:
                                        name.Append (c);
                                        if (name.Length < 6)
                                                break;

                                        if (NameIs ("public")) {
                                                TokenizerState = HtmlTokenizerState.AfterDocTypePublicKeyword;
                                                doctype!.PublicKeyword = name.ToString ();
                                        } else if (NameIs ("system")) {
                                                TokenizerState = HtmlTokenizerState.AfterDocTypeSystemKeyword;
                                                doctype!.SystemKeyword = name.ToString ();
                                        } else {
                                                TokenizerState = HtmlTokenizerState.BogusDocType;
                                        }

                                        name.Length = 0;
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.56 After DOCTYPE public keyword state
                HtmlToken? ReadAfterDocTypePublicKeyword ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                doctype!.ForceQuirksMode = true;
                                return EmitDocType ();
                        }

                        // Note: we save the data in case we hit a parse error and have to emit a data token
                        data.Append (c);

                        switch (c) {
                        case '\t': case '\r': case '\n': case '\f': case ' ':
                                TokenizerState = HtmlTokenizerState.BeforeDocTypePublicIdentifier;
                                break;
                        case '"': case '\'': // parse error
                                TokenizerState = HtmlTokenizerState.DocTypePublicIdentifierQuoted;
                                doctype!.PublicIdentifier = string.Empty;
                                quote = c;
                                break;
                        case '>': // parse error
                                TokenizerState = HtmlTokenizerState.Data;
                                doctype!.ForceQuirksMode = true;
                                return EmitDocType ();
                        default: // parse error
                                TokenizerState = HtmlTokenizerState.BogusDocType;
                                doctype!.ForceQuirksMode = true;
                                break;
                        }

                        return null;
                }

                // 8.2.4.57 Before DOCTYPE public identifier state
                HtmlToken? ReadBeforeDocTypePublicIdentifier ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '"': case '\'':
                                        TokenizerState = HtmlTokenizerState.DocTypePublicIdentifierQuoted;
                                        doctype!.PublicIdentifier = string.Empty;
                                        quote = c;
                                        return null;
                                case '>': // parse error
                                        TokenizerState = HtmlTokenizerState.Data;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                default: // parse error
                                        TokenizerState = HtmlTokenizerState.BogusDocType;
                                        doctype!.ForceQuirksMode = true;
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.58 DOCTYPE public identifier (double-quoted) state
                HtmlToken? ReadDocTypePublicIdentifierQuoted ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.PublicIdentifier = name.ToString ();
                                        doctype.ForceQuirksMode = true;
                                        name.Length = 0;

                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\0': // parse error
                                        name.Append ('\uFFFD');
                                        break;
                                case '>': // parse error
                                        TokenizerState = HtmlTokenizerState.Data;
                                        doctype!.PublicIdentifier = name.ToString ();
                                        doctype.ForceQuirksMode = true;
                                        name.Length = 0;

                                        return EmitDocType ();
                                default:
                                        if (c == quote) {
                                                TokenizerState = HtmlTokenizerState.AfterDocTypePublicIdentifier;
                                                quote = '\0';
                                                break;
                                        }

                                        name.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.DocTypePublicIdentifierQuoted);

                        doctype!.PublicIdentifier = name.ToString ();
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.60 After DOCTYPE public identifier state
                HtmlToken? ReadAfterDocTypePublicIdentifier ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                doctype!.ForceQuirksMode = true;
                                return EmitDocType ();
                        }

                        // Note: we save the data in case we hit a parse error and have to emit a data token
                        data.Append (c);

                        switch (c) {
                        case '\t': case '\r': case '\n': case '\f': case ' ':
                                TokenizerState = HtmlTokenizerState.BetweenDocTypePublicAndSystemIdentifiers;
                                break;
                        case '>':
                                TokenizerState = HtmlTokenizerState.Data;
                                return EmitDocType ();
                        case '"': case '\'': // parse error
                                TokenizerState = HtmlTokenizerState.DocTypeSystemIdentifierQuoted;
                                doctype!.SystemIdentifier = string.Empty;
                                quote = c;
                                break;
                        default: // parse error
                                TokenizerState = HtmlTokenizerState.BogusDocType;
                                doctype!.ForceQuirksMode = true;
                                break;
                        }

                        return null;
                }

                // 8.2.4.61 Between DOCTYPE public and system identifiers state
                HtmlToken? ReadBetweenDocTypePublicAndSystemIdentifiers ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '>':
                                        TokenizerState = HtmlTokenizerState.Data;
                                        return EmitDocType ();
                                case '"': case '\'':
                                        TokenizerState = HtmlTokenizerState.DocTypeSystemIdentifierQuoted;
                                        doctype!.SystemIdentifier = string.Empty;
                                        quote = c;
                                        return null;
                                default: // parse error
                                        TokenizerState = HtmlTokenizerState.BogusDocType;
                                        doctype!.ForceQuirksMode = true;
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.62 After DOCTYPE system keyword state
                HtmlToken? ReadAfterDocTypeSystemKeyword ()
                {
                        if (!TryRead (out char c)) {
                                TokenizerState = HtmlTokenizerState.EndOfFile;
                                doctype!.ForceQuirksMode = true;
                                return EmitDocType ();
                        }

                        // Note: we save the data in case we hit a parse error and have to emit a data token
                        data.Append (c);

                        switch (c) {
                        case '\t': case '\r': case '\n': case '\f': case ' ':
                                TokenizerState = HtmlTokenizerState.BeforeDocTypeSystemIdentifier;
                                break;
                        case '"': case '\'': // parse error
                                TokenizerState = HtmlTokenizerState.DocTypeSystemIdentifierQuoted;
                                doctype!.SystemIdentifier = string.Empty;
                                quote = c;
                                break;
                        case '>': // parse error
                                TokenizerState = HtmlTokenizerState.Data;
                                doctype!.ForceQuirksMode = true;
                                return EmitDocType ();
                        default: // parse error
                                TokenizerState = HtmlTokenizerState.BogusDocType;
                                doctype!.ForceQuirksMode = true;
                                break;
                        }

                        return null;
                }

                // 8.2.4.63 Before DOCTYPE system identifier state
                HtmlToken? ReadBeforeDocTypeSystemIdentifier ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '"': case '\'':
                                        TokenizerState = HtmlTokenizerState.DocTypeSystemIdentifierQuoted;
                                        doctype!.SystemIdentifier = string.Empty;
                                        quote = c;
                                        return null;
                                case '>': // parse error
                                        TokenizerState = HtmlTokenizerState.Data;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                default: // parse error
                                        TokenizerState = HtmlTokenizerState.BogusDocType;
                                        doctype!.ForceQuirksMode = true;
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.64 DOCTYPE system identifier (double-quoted) state
                HtmlToken? ReadDocTypeSystemIdentifierQuoted ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.SystemIdentifier = name.ToString ();
                                        doctype.ForceQuirksMode = true;
                                        name.Length = 0;

                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\0': // parse error
                                        name.Append ('\uFFFD');
                                        break;
                                case '>': // parse error
                                        TokenizerState = HtmlTokenizerState.Data;
                                        doctype!.SystemIdentifier = name.ToString ();
                                        doctype.ForceQuirksMode = true;
                                        name.Length = 0;

                                        return EmitDocType ();
                                default:
                                        if (c == quote) {
                                                TokenizerState = HtmlTokenizerState.AfterDocTypeSystemIdentifier;
                                                quote = '\0';
                                                break;
                                        }

                                        name.Append (c);
                                        break;
                                }
                        } while (TokenizerState == HtmlTokenizerState.DocTypeSystemIdentifierQuoted);

                        doctype!.SystemIdentifier = name.ToString ();
                        name.Length = 0;

                        return null;
                }

                // 8.2.4.66 After DOCTYPE system identifier state
                HtmlToken? ReadAfterDocTypeSystemIdentifier ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                switch (c) {
                                case '\t': case '\r': case '\n': case '\f': case ' ':
                                        break;
                                case '>':
                                        TokenizerState = HtmlTokenizerState.Data;
                                        return EmitDocType ();
                                default: // parse error
                                        TokenizerState = HtmlTokenizerState.BogusDocType;
                                        return null;
                                }
                        } while (true);
                }

                // 8.2.4.67 Bogus DOCTYPE state
                HtmlToken? ReadBogusDocType ()
                {
                        do {
                                if (!TryRead (out char c)) {
                                        TokenizerState = HtmlTokenizerState.EndOfFile;
                                        doctype!.ForceQuirksMode = true;
                                        return EmitDocType ();
                                }

                                // Note: we save the data in case we hit a parse error and have to emit a data token
                                data.Append (c);

                                if (c == '>') {
                                        TokenizerState = HtmlTokenizerState.Data;
                                        return EmitDocType ();
                                }
                        } while (true);
                }

                // 8.2.4.68 CDATA section state
                HtmlToken? ReadCDataSection ()
                {
                        do {
                                while (bufferIndex < bufferEnd) {
                                        char c = buffer[bufferIndex++];

                                        if (c == '\n') {
                                                IncrementLineNumber ();
                                        } else {
                                                linePosition++;
                                        }

                                        if (cdataIndex >= 3) {
                                                data.Append (cdata[0]);
                                                cdata[0] = cdata[1];
                                                cdata[1] = cdata[2];
                                                cdata[2] = c;

                                                if (cdata[0] == ']' && cdata[1] == ']' && cdata[2] == '>') {
                                                        TokenizerState = HtmlTokenizerState.Data;
                                                        cdataIndex = 0;

                                                        return EmitCDataToken ();
                                                }
                                        } else {
                                                cdata[cdataIndex++] = c;
                                        }
                                }

                                FillBuffer ();
                        } while (!eof);

                        TokenizerState = HtmlTokenizerState.EndOfFile;

                        for (int i = 0; i < cdataIndex; i++)
                                data.Append (cdata[i]);

                        cdataIndex = 0;

                        return EmitCDataToken ();
                }

                /// <summary>
                /// Read the next token.
                /// </summary>
                /// <remarks>
                /// Reads the next token.
                /// </remarks>
                /// <returns><see langword="true" /> if the next token was read; otherwise, <see langword="false" />.</returns>
                /// <param name="token">The token that was read.</param>
                public bool ReadNextToken ([NotNullWhen (true)] out HtmlToken? token)
                {
                        do {
                                switch (TokenizerState) {
                                case HtmlTokenizerState.Data:
                                        token = ReadData ();
                                        break;
                                case HtmlTokenizerState.CharacterReferenceInData:
                                        token = ReadCharacterReferenceInData ();
                                        break;
                                case HtmlTokenizerState.RcData:
                                        token = ReadRcData ();
                                        break;
                                case HtmlTokenizerState.CharacterReferenceInRcData:
                                        token = ReadCharacterReferenceInRcData ();
                                        break;
                                case HtmlTokenizerState.RawText:
                                        token = ReadRawText ();
                                        break;
                                case HtmlTokenizerState.ScriptData:
                                        token = ReadScriptData ();
                                        break;
                                case HtmlTokenizerState.PlainText:
                                        token = ReadPlainText ();
                                        break;
                                case HtmlTokenizerState.TagOpen:
                                        token = ReadTagOpen ();
                                        break;
                                case HtmlTokenizerState.EndTagOpen:
                                        token = ReadEndTagOpen ();
                                        break;
                                case HtmlTokenizerState.TagName:
                                        token = ReadTagName ();
                                        break;
                                case HtmlTokenizerState.RcDataLessThan:
                                        token = ReadRcDataLessThan ();
                                        break;
                                case HtmlTokenizerState.RcDataEndTagOpen:
                                        token = ReadRcDataEndTagOpen ();
                                        break;
                                case HtmlTokenizerState.RcDataEndTagName:
                                        token = ReadRcDataEndTagName ();
                                        break;
                                case HtmlTokenizerState.RawTextLessThan:
                                        token = ReadRawTextLessThan ();
                                        break;
                                case HtmlTokenizerState.RawTextEndTagOpen:
                                        token = ReadRawTextEndTagOpen ();
                                        break;
                                case HtmlTokenizerState.RawTextEndTagName:
                                        token = ReadRawTextEndTagName ();
                                        break;
                                case HtmlTokenizerState.ScriptDataLessThan:
                                        token = ReadScriptDataLessThan ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEndTagOpen:
                                        token = ReadScriptDataEndTagOpen ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEndTagName:
                                        token = ReadScriptDataEndTagName ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEscapeStart:
                                        token = ReadScriptDataEscapeStart ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEscapeStartDash:
                                        token = ReadScriptDataEscapeStartDash ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEscaped:
                                        token = ReadScriptDataEscaped ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEscapedDash:
                                        token = ReadScriptDataEscapedDash ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEscapedDashDash:
                                        token = ReadScriptDataEscapedDashDash ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEscapedLessThan:
                                        token = ReadScriptDataEscapedLessThan ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEscapedEndTagOpen:
                                        token = ReadScriptDataEscapedEndTagOpen ();
                                        break;
                                case HtmlTokenizerState.ScriptDataEscapedEndTagName:
                                        token = ReadScriptDataEscapedEndTagName ();
                                        break;
                                case HtmlTokenizerState.ScriptDataDoubleEscapeStart:
                                        token = ReadScriptDataDoubleEscapeStart ();
                                        break;
                                case HtmlTokenizerState.ScriptDataDoubleEscaped:
                                        token = ReadScriptDataDoubleEscaped ();
                                        break;
                                case HtmlTokenizerState.ScriptDataDoubleEscapedDash:
                                        token = ReadScriptDataDoubleEscapedDash ();
                                        break;
                                case HtmlTokenizerState.ScriptDataDoubleEscapedDashDash:
                                        token = ReadScriptDataDoubleEscapedDashDash ();
                                        break;
                                case HtmlTokenizerState.ScriptDataDoubleEscapedLessThan:
                                        token = ReadScriptDataDoubleEscapedLessThan ();
                                        break;
                                case HtmlTokenizerState.ScriptDataDoubleEscapeEnd:
                                        token = ReadScriptDataDoubleEscapeEnd ();
                                        break;
                                case HtmlTokenizerState.BeforeAttributeName:
                                        token = ReadBeforeAttributeName ();
                                        break;
                                case HtmlTokenizerState.AttributeName:
                                        token = ReadAttributeName ();
                                        break;
                                case HtmlTokenizerState.AfterAttributeName:
                                        token = ReadAfterAttributeName ();
                                        break;
                                case HtmlTokenizerState.BeforeAttributeValue:
                                        token = ReadBeforeAttributeValue ();
                                        break;
                                case HtmlTokenizerState.AttributeValueQuoted:
                                        token = ReadAttributeValueQuoted ();
                                        break;
                                case HtmlTokenizerState.AttributeValueUnquoted:
                                        token = ReadAttributeValueUnquoted ();
                                        break;
                                case HtmlTokenizerState.CharacterReferenceInAttributeValue:
                                        token = ReadCharacterReferenceInAttributeValue ();
                                        break;
                                case HtmlTokenizerState.AfterAttributeValueQuoted:
                                        token = ReadAfterAttributeValueQuoted ();
                                        break;
                                case HtmlTokenizerState.SelfClosingStartTag:
                                        token = ReadSelfClosingStartTag ();
                                        break;
                                case HtmlTokenizerState.BogusComment:
                                        token = ReadBogusComment ();
                                        break;
                                case HtmlTokenizerState.MarkupDeclarationOpen:
                                        token = ReadMarkupDeclarationOpen ();
                                        break;
                                case HtmlTokenizerState.CommentStart:
                                        token = ReadCommentStart ();
                                        break;
                                case HtmlTokenizerState.CommentStartDash:
                                        token = ReadCommentStartDash ();
                                        break;
                                case HtmlTokenizerState.Comment:
                                        token = ReadComment ();
                                        break;
                                case HtmlTokenizerState.CommentEndDash:
                                        token = ReadCommentEndDash ();
                                        break;
                                case HtmlTokenizerState.CommentEnd:
                                        token = ReadCommentEnd ();
                                        break;
                                case HtmlTokenizerState.CommentEndBang:
                                        token = ReadCommentEndBang ();
                                        break;
                                case HtmlTokenizerState.DocType:
                                        token = ReadDocType ();
                                        break;
                                case HtmlTokenizerState.BeforeDocTypeName:
                                        token = ReadBeforeDocTypeName ();
                                        break;
                                case HtmlTokenizerState.DocTypeName:
                                        token = ReadDocTypeName ();
                                        break;
                                case HtmlTokenizerState.AfterDocTypeName:
                                        token = ReadAfterDocTypeName ();
                                        break;
                                case HtmlTokenizerState.AfterDocTypePublicKeyword:
                                        token = ReadAfterDocTypePublicKeyword ();
                                        break;
                                case HtmlTokenizerState.BeforeDocTypePublicIdentifier:
                                        token = ReadBeforeDocTypePublicIdentifier ();
                                        break;
                                case HtmlTokenizerState.DocTypePublicIdentifierQuoted:
                                        token = ReadDocTypePublicIdentifierQuoted ();
                                        break;
                                case HtmlTokenizerState.AfterDocTypePublicIdentifier:
                                        token = ReadAfterDocTypePublicIdentifier ();
                                        break;
                                case HtmlTokenizerState.BetweenDocTypePublicAndSystemIdentifiers:
                                        token = ReadBetweenDocTypePublicAndSystemIdentifiers ();
                                        break;
                                case HtmlTokenizerState.AfterDocTypeSystemKeyword:
                                        token = ReadAfterDocTypeSystemKeyword ();
                                        break;
                                case HtmlTokenizerState.BeforeDocTypeSystemIdentifier:
                                        token = ReadBeforeDocTypeSystemIdentifier ();
                                        break;
                                case HtmlTokenizerState.DocTypeSystemIdentifierQuoted:
                                        token = ReadDocTypeSystemIdentifierQuoted ();
                                        break;
                                case HtmlTokenizerState.AfterDocTypeSystemIdentifier:
                                        token = ReadAfterDocTypeSystemIdentifier ();
                                        break;
                                case HtmlTokenizerState.BogusDocType:
                                        token = ReadBogusDocType ();
                                        break;
                                case HtmlTokenizerState.CDataSection:
                                        token = ReadCDataSection ();
                                        break;
                                case HtmlTokenizerState.EndOfFile:
                                default:
                                        token = null;
                                        return false;
                                }
                        } while (token is null);

                        return true;
                }
        }
}

jstedfast / HtmlKit / 1.2.0.267

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