dom/serializers/nsXMLContentSerializer.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * nsIContentSerializer implementation that can be used with an
 * nsIDocumentEncoder to convert an XML DOM to an XML string that
 * could be parsed into more or less the original DOM.
 */

#include "nsXMLContentSerializer.h"

#include "nsGkAtoms.h"
#include "nsIContent.h"
#include "nsIContentInlines.h"
#include "mozilla/dom/Document.h"
#include "nsIDocumentEncoder.h"
#include "nsElementTable.h"
#include "nsNameSpaceManager.h"
#include "nsTextFragment.h"
#include "nsString.h"
#include "mozilla/Sprintf.h"
#include "nsUnicharUtils.h"
#include "nsCRT.h"
#include "nsContentUtils.h"
#include "nsAttrName.h"
#include "mozilla/dom/Comment.h"
#include "mozilla/dom/CustomElementRegistry.h"
#include "mozilla/dom/DocumentType.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/ProcessingInstruction.h"
#include "mozilla/intl/LineBreaker.h"
#include "nsParserConstants.h"
#include "mozilla/Encoding.h"

using namespace mozilla;
using namespace mozilla::dom;

#define kXMLNS "xmlns"

// to be readable, we assume that an indented line contains
// at least this number of characters (arbitrary value here).
// This is a limit for the indentation.
#define MIN_INDENTED_LINE_LENGTH 15

// the string used to indent.
#define INDENT_STRING "  "
#define INDENT_STRING_LENGTH 2

nsresult NS_NewXMLContentSerializer(nsIContentSerializer** aSerializer) {
  RefPtr<nsXMLContentSerializer> it = new nsXMLContentSerializer();
  it.forget(aSerializer);
  return NS_OK;
}

nsXMLContentSerializer::nsXMLContentSerializer()
    : mPrefixIndex(0),
      mColPos(0),
      mIndentOverflow(0),
      mIsIndentationAddedOnCurrentLine(false),
      mInAttribute(false),
      mAddNewlineForRootNode(false),
      mAddSpace(false),
      mMayIgnoreLineBreakSequence(false),
      mBodyOnly(false),
      mInBody(0) {}

nsXMLContentSerializer::~nsXMLContentSerializer() = default;

NS_IMPL_ISUPPORTS(nsXMLContentSerializer, nsIContentSerializer)

NS_IMETHODIMP
nsXMLContentSerializer::Init(uint32_t aFlags, uint32_t aWrapColumn,
                             const Encoding* aEncoding, bool aIsCopying,
                             bool aRewriteEncodingDeclaration,
                             bool* aNeedsPreformatScanning,
                             nsAString& aOutput) {
  *aNeedsPreformatScanning = false;
  mPrefixIndex = 0;
  mColPos = 0;
  mIndentOverflow = 0;
  mIsIndentationAddedOnCurrentLine = false;
  mInAttribute = false;
  mAddNewlineForRootNode = false;
  mAddSpace = false;
  mMayIgnoreLineBreakSequence = false;
  mBodyOnly = false;
  mInBody = 0;

  if (aEncoding) {
    aEncoding->Name(mCharset);
  }
  mFlags = aFlags;

  // Set the line break character:
  if ((mFlags & nsIDocumentEncoder::OutputCRLineBreak) &&
      (mFlags & nsIDocumentEncoder::OutputLFLineBreak)) {  // Windows
    mLineBreak.AssignLiteral("\r\n");
  } else if (mFlags & nsIDocumentEncoder::OutputCRLineBreak) {  // Mac
    mLineBreak.Assign('\r');
  } else if (mFlags & nsIDocumentEncoder::OutputLFLineBreak) {  // Unix/DOM
    mLineBreak.Assign('\n');
  } else {
    mLineBreak.AssignLiteral(NS_LINEBREAK);  // Platform/default
  }

  mDoRaw = !!(mFlags & nsIDocumentEncoder::OutputRaw);

  mDoFormat = (mFlags & nsIDocumentEncoder::OutputFormatted && !mDoRaw);

  mDoWrap = (mFlags & nsIDocumentEncoder::OutputWrap && !mDoRaw);

  mAllowLineBreaking =
      !(mFlags & nsIDocumentEncoder::OutputDisallowLineBreaking);

  if (!aWrapColumn) {
    mMaxColumn = 72;
  } else {
    mMaxColumn = aWrapColumn;
  }

  mOutput = &aOutput;
  mPreLevel = 0;
  mIsIndentationAddedOnCurrentLine = false;
  return NS_OK;
}

nsresult nsXMLContentSerializer::AppendTextData(nsIContent* aNode,
                                                int32_t aStartOffset,
                                                int32_t aEndOffset,
                                                nsAString& aStr,
                                                bool aTranslateEntities) {
  nsIContent* content = aNode;
  const nsTextFragment* frag;
  if (!content || !(frag = content->GetText())) {
    return NS_ERROR_FAILURE;
  }

  int32_t fragLength = frag->GetLength();
  int32_t endoffset =
      (aEndOffset == -1) ? fragLength : std::min(aEndOffset, fragLength);
  int32_t length = endoffset - aStartOffset;

  NS_ASSERTION(aStartOffset >= 0, "Negative start offset for text fragment!");
  NS_ASSERTION(aStartOffset <= endoffset,
               "A start offset is beyond the end of the text fragment!");

  if (length <= 0) {
    // XXX Zero is a legal value, maybe non-zero values should be an
    // error.
    return NS_OK;
  }

  if (frag->Is2b()) {
    const char16_t* strStart = frag->Get2b() + aStartOffset;
    if (aTranslateEntities) {
      NS_ENSURE_TRUE(AppendAndTranslateEntities(
                         Substring(strStart, strStart + length), aStr),
                     NS_ERROR_OUT_OF_MEMORY);
    } else {
      NS_ENSURE_TRUE(aStr.Append(Substring(strStart, strStart + length),
                                 mozilla::fallible),
                     NS_ERROR_OUT_OF_MEMORY);
    }
  } else {
    nsAutoString utf16;
    if (!CopyASCIItoUTF16(Span(frag->Get1b() + aStartOffset, length), utf16,
                          mozilla::fallible_t())) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
    if (aTranslateEntities) {
      NS_ENSURE_TRUE(AppendAndTranslateEntities(utf16, aStr),
                     NS_ERROR_OUT_OF_MEMORY);
    } else {
      NS_ENSURE_TRUE(aStr.Append(utf16, mozilla::fallible),
                     NS_ERROR_OUT_OF_MEMORY);
    }
  }

  return NS_OK;
}

NS_IMETHODIMP
nsXMLContentSerializer::AppendText(nsIContent* aText, int32_t aStartOffset,
                                   int32_t aEndOffset) {
  NS_ENSURE_ARG(aText);
  NS_ENSURE_STATE(mOutput);

  nsAutoString data;
  nsresult rv;

  rv = AppendTextData(aText, aStartOffset, aEndOffset, data, true);
  if (NS_FAILED(rv)) return NS_ERROR_FAILURE;

  if (mDoRaw || PreLevel() > 0) {
    NS_ENSURE_TRUE(AppendToStringConvertLF(data, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else if (mDoFormat) {
    NS_ENSURE_TRUE(AppendToStringFormatedWrapped(data, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else if (mDoWrap) {
    NS_ENSURE_TRUE(AppendToStringWrapped(data, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else {
    NS_ENSURE_TRUE(AppendToStringConvertLF(data, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  }

  return NS_OK;
}

NS_IMETHODIMP
nsXMLContentSerializer::AppendCDATASection(nsIContent* aCDATASection,
                                           int32_t aStartOffset,
                                           int32_t aEndOffset) {
  NS_ENSURE_ARG(aCDATASection);
  NS_ENSURE_STATE(mOutput);

  nsresult rv;

  constexpr auto cdata = u"<![CDATA["_ns;

  if (mDoRaw || PreLevel() > 0) {
    NS_ENSURE_TRUE(AppendToString(cdata, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  } else if (mDoFormat) {
    NS_ENSURE_TRUE(AppendToStringFormatedWrapped(cdata, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else if (mDoWrap) {
    NS_ENSURE_TRUE(AppendToStringWrapped(cdata, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else {
    NS_ENSURE_TRUE(AppendToString(cdata, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  }

  nsAutoString data;
  rv = AppendTextData(aCDATASection, aStartOffset, aEndOffset, data, false);
  if (NS_FAILED(rv)) return NS_ERROR_FAILURE;

  NS_ENSURE_TRUE(AppendToStringConvertLF(data, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);

  NS_ENSURE_TRUE(AppendToString(u"]]>"_ns, *mOutput), NS_ERROR_OUT_OF_MEMORY);

  return NS_OK;
}

NS_IMETHODIMP
nsXMLContentSerializer::AppendProcessingInstruction(ProcessingInstruction* aPI,
                                                    int32_t aStartOffset,
                                                    int32_t aEndOffset) {
  NS_ENSURE_STATE(mOutput);

  nsAutoString target, data, start;

  NS_ENSURE_TRUE(MaybeAddNewlineForRootNode(*mOutput), NS_ERROR_OUT_OF_MEMORY);

  aPI->GetTarget(target);

  aPI->GetData(data);

  NS_ENSURE_TRUE(start.AppendLiteral("<?", mozilla::fallible),
                 NS_ERROR_OUT_OF_MEMORY);
  NS_ENSURE_TRUE(start.Append(target, mozilla::fallible),
                 NS_ERROR_OUT_OF_MEMORY);

  if (mDoRaw || PreLevel() > 0) {
    NS_ENSURE_TRUE(AppendToString(start, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  } else if (mDoFormat) {
    if (mAddSpace) {
      NS_ENSURE_TRUE(AppendNewLineToString(*mOutput), NS_ERROR_OUT_OF_MEMORY);
    }
    NS_ENSURE_TRUE(AppendToStringFormatedWrapped(start, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else if (mDoWrap) {
    NS_ENSURE_TRUE(AppendToStringWrapped(start, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else {
    NS_ENSURE_TRUE(AppendToString(start, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  }

  if (!data.IsEmpty()) {
    NS_ENSURE_TRUE(AppendToString(char16_t(' '), *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
    NS_ENSURE_TRUE(AppendToStringConvertLF(data, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  }
  NS_ENSURE_TRUE(AppendToString(u"?>"_ns, *mOutput), NS_ERROR_OUT_OF_MEMORY);

  MaybeFlagNewlineForRootNode(aPI);

  return NS_OK;
}

NS_IMETHODIMP
nsXMLContentSerializer::AppendComment(Comment* aComment, int32_t aStartOffset,
                                      int32_t aEndOffset) {
  NS_ENSURE_STATE(mOutput);

  nsAutoString data;
  aComment->GetData(data);

  int32_t dataLength = data.Length();
  if (aStartOffset || (aEndOffset != -1 && aEndOffset < dataLength)) {
    int32_t length =
        (aEndOffset == -1) ? dataLength : std::min(aEndOffset, dataLength);
    length -= aStartOffset;

    nsAutoString frag;
    if (length > 0) {
      data.Mid(frag, aStartOffset, length);
    }
    data.Assign(frag);
  }

  NS_ENSURE_TRUE(MaybeAddNewlineForRootNode(*mOutput), NS_ERROR_OUT_OF_MEMORY);

  constexpr auto startComment = u"<!--"_ns;

  if (mDoRaw || PreLevel() > 0) {
    NS_ENSURE_TRUE(AppendToString(startComment, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else if (mDoFormat) {
    if (mAddSpace) {
      NS_ENSURE_TRUE(AppendNewLineToString(*mOutput), NS_ERROR_OUT_OF_MEMORY);
    }
    NS_ENSURE_TRUE(AppendToStringFormatedWrapped(startComment, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else if (mDoWrap) {
    NS_ENSURE_TRUE(AppendToStringWrapped(startComment, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  } else {
    NS_ENSURE_TRUE(AppendToString(startComment, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  }

  // Even if mDoformat, we don't format the content because it
  // could have been preformated by the author
  NS_ENSURE_TRUE(AppendToStringConvertLF(data, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);
  NS_ENSURE_TRUE(AppendToString(u"-->"_ns, *mOutput), NS_ERROR_OUT_OF_MEMORY);

  MaybeFlagNewlineForRootNode(aComment);

  return NS_OK;
}

NS_IMETHODIMP
nsXMLContentSerializer::AppendDoctype(DocumentType* aDocType) {
  NS_ENSURE_STATE(mOutput);

  nsAutoString name, publicId, systemId;
  aDocType->GetName(name);
  aDocType->GetPublicId(publicId);
  aDocType->GetSystemId(systemId);

  NS_ENSURE_TRUE(MaybeAddNewlineForRootNode(*mOutput), NS_ERROR_OUT_OF_MEMORY);

  NS_ENSURE_TRUE(AppendToString(u"<!DOCTYPE "_ns, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);
  NS_ENSURE_TRUE(AppendToString(name, *mOutput), NS_ERROR_OUT_OF_MEMORY);

  char16_t quote;
  if (!publicId.IsEmpty()) {
    NS_ENSURE_TRUE(AppendToString(u" PUBLIC "_ns, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
    if (publicId.FindChar(char16_t('"')) == -1) {
      quote = char16_t('"');
    } else {
      quote = char16_t('\'');
    }
    NS_ENSURE_TRUE(AppendToString(quote, *mOutput), NS_ERROR_OUT_OF_MEMORY);
    NS_ENSURE_TRUE(AppendToString(publicId, *mOutput), NS_ERROR_OUT_OF_MEMORY);
    NS_ENSURE_TRUE(AppendToString(quote, *mOutput), NS_ERROR_OUT_OF_MEMORY);

    if (!systemId.IsEmpty()) {
      NS_ENSURE_TRUE(AppendToString(char16_t(' '), *mOutput),
                     NS_ERROR_OUT_OF_MEMORY);
      if (systemId.FindChar(char16_t('"')) == -1) {
        quote = char16_t('"');
      } else {
        quote = char16_t('\'');
      }
      NS_ENSURE_TRUE(AppendToString(quote, *mOutput), NS_ERROR_OUT_OF_MEMORY);
      NS_ENSURE_TRUE(AppendToString(systemId, *mOutput),
                     NS_ERROR_OUT_OF_MEMORY);
      NS_ENSURE_TRUE(AppendToString(quote, *mOutput), NS_ERROR_OUT_OF_MEMORY);
    }
  } else if (!systemId.IsEmpty()) {
    if (systemId.FindChar(char16_t('"')) == -1) {
      quote = char16_t('"');
    } else {
      quote = char16_t('\'');
    }
    NS_ENSURE_TRUE(AppendToString(u" SYSTEM "_ns, *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
    NS_ENSURE_TRUE(AppendToString(quote, *mOutput), NS_ERROR_OUT_OF_MEMORY);
    NS_ENSURE_TRUE(AppendToString(systemId, *mOutput), NS_ERROR_OUT_OF_MEMORY);
    NS_ENSURE_TRUE(AppendToString(quote, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  }

  NS_ENSURE_TRUE(AppendToString(kGreaterThan, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);
  MaybeFlagNewlineForRootNode(aDocType);

  return NS_OK;
}

nsresult nsXMLContentSerializer::PushNameSpaceDecl(const nsAString& aPrefix,
                                                   const nsAString& aURI,
                                                   nsIContent* aOwner) {
  NameSpaceDecl* decl = mNameSpaceStack.AppendElement();
  if (!decl) return NS_ERROR_OUT_OF_MEMORY;

  decl->mPrefix.Assign(aPrefix);
  decl->mURI.Assign(aURI);
  // Don't addref - this weak reference will be removed when
  // we pop the stack
  decl->mOwner = aOwner;
  return NS_OK;
}

void nsXMLContentSerializer::PopNameSpaceDeclsFor(nsIContent* aOwner) {
  int32_t index, count;

  count = mNameSpaceStack.Length();
  for (index = count - 1; index >= 0; index--) {
    if (mNameSpaceStack[index].mOwner != aOwner) {
      break;
    }
    mNameSpaceStack.RemoveLastElement();
  }
}

bool nsXMLContentSerializer::ConfirmPrefix(nsAString& aPrefix,
                                           const nsAString& aURI,
                                           nsIContent* aElement,
                                           bool aIsAttribute) {
  if (aPrefix.EqualsLiteral(kXMLNS)) {
    return false;
  }

  if (aURI.EqualsLiteral("http://www.w3.org/XML/1998/namespace")) {
    // The prefix must be xml for this namespace. We don't need to declare it,
    // so always just set the prefix to xml.
    aPrefix.AssignLiteral("xml");

    return false;
  }

  bool mustHavePrefix;
  if (aIsAttribute) {
    if (aURI.IsEmpty()) {
      // Attribute in the null namespace.  This just shouldn't have a prefix.
      // And there's no need to push any namespace decls
      aPrefix.Truncate();
      return false;
    }

    // Attribute not in the null namespace -- must have a prefix
    mustHavePrefix = true;
  } else {
    // Not an attribute, so doesn't _have_ to have a prefix
    mustHavePrefix = false;
  }

  // Keep track of the closest prefix that's bound to aURI and whether we've
  // found such a thing.  closestURIMatch holds the prefix, and uriMatch
  // indicates whether we actually have one.
  nsAutoString closestURIMatch;
  bool uriMatch = false;

  // Also keep track of whether we've seen aPrefix already.  If we have, that
  // means that it's already bound to a URI different from aURI, so even if we
  // later (so in a more outer scope) see it bound to aURI we can't reuse it.
  bool haveSeenOurPrefix = false;

  int32_t count = mNameSpaceStack.Length();
  int32_t index = count - 1;
  while (index >= 0) {
    NameSpaceDecl& decl = mNameSpaceStack.ElementAt(index);
    // Check if we've found a prefix match
    if (aPrefix.Equals(decl.mPrefix)) {
      // If the URIs match and aPrefix is not bound to any other URI, we can
      // use aPrefix
      if (!haveSeenOurPrefix && aURI.Equals(decl.mURI)) {
        // Just use our uriMatch stuff.  That will deal with an empty aPrefix
        // the right way.  We can break out of the loop now, though.
        uriMatch = true;
        closestURIMatch = aPrefix;
        break;
      }

      haveSeenOurPrefix = true;

      // If they don't, and either:
      // 1) We have a prefix (so we'd be redeclaring this prefix to point to a
      //    different namespace) or
      // 2) We're looking at an existing default namespace decl on aElement (so
      //    we can't create a new default namespace decl for this URI)
      // then generate a new prefix.  Note that we do NOT generate new prefixes
      // if we happen to have aPrefix == decl->mPrefix == "" and mismatching
      // URIs when |decl| doesn't have aElement as its owner.  In that case we
      // can simply push the new namespace URI as the default namespace for
      // aElement.
      if (!aPrefix.IsEmpty() || decl.mOwner == aElement) {
        NS_ASSERTION(!aURI.IsEmpty(),
                     "Not allowed to add a xmlns attribute with an empty "
                     "namespace name unless it declares the default "
                     "namespace.");

        GenerateNewPrefix(aPrefix);
        // Now we need to validate our new prefix/uri combination; check it
        // against the full namespace stack again.  Note that just restarting
        // the while loop is ok, since we haven't changed aURI, so the
        // closestURIMatch and uriMatch state is not affected.
        index = count - 1;
        haveSeenOurPrefix = false;
        continue;
      }
    }

    // If we've found a URI match, then record the first one
    if (!uriMatch && aURI.Equals(decl.mURI)) {
      // Need to check that decl->mPrefix is not declared anywhere closer to
      // us.  If it is, we can't use it.
      bool prefixOK = true;
      int32_t index2;
      for (index2 = count - 1; index2 > index && prefixOK; --index2) {
        prefixOK = (mNameSpaceStack[index2].mPrefix != decl.mPrefix);
      }

      if (prefixOK) {
        uriMatch = true;
        closestURIMatch.Assign(decl.mPrefix);
      }
    }

    --index;
  }

  // At this point the following invariants hold:
  // 1) The prefix in closestURIMatch is mapped to aURI in our scope if
  //    uriMatch is set.
  // 2) There is nothing on the namespace stack that has aPrefix as the prefix
  //    and a _different_ URI, except for the case aPrefix.IsEmpty (and
  //    possible default namespaces on ancestors)

  // So if uriMatch is set it's OK to use the closestURIMatch prefix.  The one
  // exception is when closestURIMatch is actually empty (default namespace
  // decl) and we must have a prefix.
  if (uriMatch && (!mustHavePrefix || !closestURIMatch.IsEmpty())) {
    aPrefix.Assign(closestURIMatch);
    return false;
  }

  if (aPrefix.IsEmpty()) {
    // At this point, aPrefix is empty (which means we never had a prefix to
    // start with).  If we must have a prefix, just generate a new prefix and
    // then send it back through the namespace stack checks to make sure it's
    // OK.
    if (mustHavePrefix) {
      GenerateNewPrefix(aPrefix);
      return ConfirmPrefix(aPrefix, aURI, aElement, aIsAttribute);
    }

    // One final special case.  If aPrefix is empty and we never saw an empty
    // prefix (default namespace decl) on the namespace stack and we're in the
    // null namespace there is no reason to output an |xmlns=""| here.  It just
    // makes the output less readable.
    if (!haveSeenOurPrefix && aURI.IsEmpty()) {
      return false;
    }
  }

  // Now just set aURI as the new default namespace URI.  Indicate that we need
  // to create a namespace decl for the final prefix
  return true;
}

void nsXMLContentSerializer::GenerateNewPrefix(nsAString& aPrefix) {
  aPrefix.Assign('a');
  aPrefix.AppendInt(mPrefixIndex++);
}

bool nsXMLContentSerializer::SerializeAttr(const nsAString& aPrefix,
                                           const nsAString& aName,
                                           const nsAString& aValue,
                                           nsAString& aStr,
                                           bool aDoEscapeEntities) {
  nsAutoString attrString_;
  // For innerHTML we can do faster appending without
  // temporary strings.
  bool rawAppend = mDoRaw && aDoEscapeEntities;
  nsAString& attrString = (rawAppend) ? aStr : attrString_;

  NS_ENSURE_TRUE(attrString.Append(char16_t(' '), mozilla::fallible), false);
  if (!aPrefix.IsEmpty()) {
    NS_ENSURE_TRUE(attrString.Append(aPrefix, mozilla::fallible), false);
    NS_ENSURE_TRUE(attrString.Append(char16_t(':'), mozilla::fallible), false);
  }
  NS_ENSURE_TRUE(attrString.Append(aName, mozilla::fallible), false);

  if (aDoEscapeEntities) {
    // if problem characters are turned into character entity references
    // then there will be no problem with the value delimiter characters
    NS_ENSURE_TRUE(attrString.AppendLiteral("=\"", mozilla::fallible), false);

    mInAttribute = true;
    bool result = AppendAndTranslateEntities(aValue, attrString);
    mInAttribute = false;
    NS_ENSURE_TRUE(result, false);

    NS_ENSURE_TRUE(attrString.Append(char16_t('"'), mozilla::fallible), false);
    if (rawAppend) {
      return true;
    }
  } else {
    // Depending on whether the attribute value contains quotes or apostrophes
    // we need to select the delimiter character and escape characters using
    // character entity references, ignoring the value of aDoEscapeEntities.
    // See http://www.w3.org/TR/REC-html40/appendix/notes.html#h-B.3.2.2 for
    // the standard on character entity references in values.  We also have to
    // make sure to escape any '&' characters.

    bool bIncludesSingle = false;
    bool bIncludesDouble = false;
    nsAString::const_iterator iCurr, iEnd;
    aValue.BeginReading(iCurr);
    aValue.EndReading(iEnd);
    for (; iCurr != iEnd; ++iCurr) {
      if (*iCurr == char16_t('\'')) {
        bIncludesSingle = true;
        if (bIncludesDouble) {
          break;
        }
      } else if (*iCurr == char16_t('"')) {
        bIncludesDouble = true;
        if (bIncludesSingle) {
          break;
        }
      }
    }

    // Delimiter and escaping is according to the following table
    //    bIncludesDouble   bIncludesSingle   Delimiter    Escape Double Quote
    //    FALSE             FALSE             "            FALSE
    //    FALSE             TRUE              "            FALSE
    //    TRUE              FALSE             '            FALSE
    //    TRUE              TRUE              "            TRUE
    char16_t cDelimiter =
        (bIncludesDouble && !bIncludesSingle) ? char16_t('\'') : char16_t('"');
    NS_ENSURE_TRUE(attrString.Append(char16_t('='), mozilla::fallible), false);
    NS_ENSURE_TRUE(attrString.Append(cDelimiter, mozilla::fallible), false);
    nsAutoString sValue(aValue);
    NS_ENSURE_TRUE(
        sValue.ReplaceSubstring(u"&"_ns, u"&amp;"_ns, mozilla::fallible),
        false);
    if (bIncludesDouble && bIncludesSingle) {
      NS_ENSURE_TRUE(
          sValue.ReplaceSubstring(u"\""_ns, u"&quot;"_ns, mozilla::fallible),
          false);
    }
    NS_ENSURE_TRUE(attrString.Append(sValue, mozilla::fallible), false);
    NS_ENSURE_TRUE(attrString.Append(cDelimiter, mozilla::fallible), false);
  }
  if (mDoRaw || PreLevel() > 0) {
    NS_ENSURE_TRUE(AppendToStringConvertLF(attrString, aStr), false);
  } else if (mDoFormat) {
    NS_ENSURE_TRUE(AppendToStringFormatedWrapped(attrString, aStr), false);
  } else if (mDoWrap) {
    NS_ENSURE_TRUE(AppendToStringWrapped(attrString, aStr), false);
  } else {
    NS_ENSURE_TRUE(AppendToStringConvertLF(attrString, aStr), false);
  }

  return true;
}

uint32_t nsXMLContentSerializer::ScanNamespaceDeclarations(
    Element* aElement, Element* aOriginalElement,
    const nsAString& aTagNamespaceURI) {
  uint32_t index, count;
  nsAutoString uriStr, valueStr;

  count = aElement->GetAttrCount();

  // First scan for namespace declarations, pushing each on the stack
  uint32_t skipAttr = count;
  for (index = 0; index < count; index++) {
    const BorrowedAttrInfo info = aElement->GetAttrInfoAt(index);
    const nsAttrName* name = info.mName;

    int32_t namespaceID = name->NamespaceID();
    nsAtom* attrName = name->LocalName();

    if (namespaceID == kNameSpaceID_XMLNS ||
        // Also push on the stack attrs named "xmlns" in the null
        // namespace... because once we serialize those out they'll look like
        // namespace decls.  :(
        // XXXbz what if we have both "xmlns" in the null namespace and "xmlns"
        // in the xmlns namespace?
        (namespaceID == kNameSpaceID_None && attrName == nsGkAtoms::xmlns)) {
      info.mValue->ToString(uriStr);

      if (!name->GetPrefix()) {
        if (aTagNamespaceURI.IsEmpty() && !uriStr.IsEmpty()) {
          // If the element is in no namespace we need to add a xmlns
          // attribute to declare that. That xmlns attribute must not have a
          // prefix (see http://www.w3.org/TR/REC-xml-names/#dt-prefix), ie it
          // must declare the default namespace. We just found an xmlns
          // attribute that declares the default namespace to something
          // non-empty. We're going to ignore this attribute, for children we
          // will detect that we need to add it again and attributes aren't
          // affected by the default namespace.
          skipAttr = index;
        } else {
          // Default NS attribute does not have prefix (and the name is "xmlns")
          PushNameSpaceDecl(u""_ns, uriStr, aOriginalElement);
        }
      } else {
        PushNameSpaceDecl(nsDependentAtomString(attrName), uriStr,
                          aOriginalElement);
      }
    }
  }
  return skipAttr;
}

bool nsXMLContentSerializer::IsJavaScript(nsIContent* aContent,
                                          nsAtom* aAttrNameAtom,
                                          int32_t aAttrNamespaceID,
                                          const nsAString& aValueString) {
  bool isHtml = aContent->IsHTMLElement();
  bool isXul = aContent->IsXULElement();
  bool isSvg = aContent->IsSVGElement();

  if (aAttrNamespaceID == kNameSpaceID_None && (isHtml || isXul || isSvg) &&
      (aAttrNameAtom == nsGkAtoms::href || aAttrNameAtom == nsGkAtoms::src)) {
    static const char kJavaScript[] = "javascript";
    int32_t pos = aValueString.FindChar(':');
    if (pos < (int32_t)(sizeof kJavaScript - 1)) return false;
    nsAutoString scheme(Substring(aValueString, 0, pos));
    scheme.StripWhitespace();
    if ((scheme.Length() == (sizeof kJavaScript - 1)) &&
        scheme.EqualsIgnoreCase(kJavaScript))
      return true;
    else
      return false;
  }

  return aContent->IsEventAttributeName(aAttrNameAtom);
}

bool nsXMLContentSerializer::SerializeAttributes(
    Element* aElement, Element* aOriginalElement, nsAString& aTagPrefix,
    const nsAString& aTagNamespaceURI, nsAtom* aTagName, nsAString& aStr,
    uint32_t aSkipAttr, bool aAddNSAttr) {
  nsAutoString prefixStr, uriStr, valueStr;
  nsAutoString xmlnsStr;
  xmlnsStr.AssignLiteral(kXMLNS);
  uint32_t index, count;

  MaybeSerializeIsValue(aElement, aStr);

  // If we had to add a new namespace declaration, serialize
  // and push it on the namespace stack
  if (aAddNSAttr) {
    if (aTagPrefix.IsEmpty()) {
      // Serialize default namespace decl
      NS_ENSURE_TRUE(
          SerializeAttr(u""_ns, xmlnsStr, aTagNamespaceURI, aStr, true), false);
    } else {
      // Serialize namespace decl
      NS_ENSURE_TRUE(
          SerializeAttr(xmlnsStr, aTagPrefix, aTagNamespaceURI, aStr, true),
          false);
    }
    PushNameSpaceDecl(aTagPrefix, aTagNamespaceURI, aOriginalElement);
  }

  count = aElement->GetAttrCount();

  // Now serialize each of the attributes
  // XXX Unfortunately we need a namespace manager to get
  // attribute URIs.
  for (index = 0; index < count; index++) {
    if (aSkipAttr == index) {
      continue;
    }

    const nsAttrName* name = aElement->GetAttrNameAt(index);
    int32_t namespaceID = name->NamespaceID();
    nsAtom* attrName = name->LocalName();
    nsAtom* attrPrefix = name->GetPrefix();

    // Filter out any attribute starting with [-|_]moz
    nsDependentAtomString attrNameStr(attrName);
    if (StringBeginsWith(attrNameStr, u"_moz"_ns) ||
        StringBeginsWith(attrNameStr, u"-moz"_ns)) {
      continue;
    }

    if (attrPrefix) {
      attrPrefix->ToString(prefixStr);
    } else {
      prefixStr.Truncate();
    }

    bool addNSAttr = false;
    if (kNameSpaceID_XMLNS != namespaceID) {
      nsContentUtils::NameSpaceManager()->GetNameSpaceURI(namespaceID, uriStr);
      addNSAttr = ConfirmPrefix(prefixStr, uriStr, aOriginalElement, true);
    }

    aElement->GetAttr(namespaceID, attrName, valueStr);

    nsDependentAtomString nameStr(attrName);
    bool isJS = IsJavaScript(aElement, attrName, namespaceID, valueStr);

    NS_ENSURE_TRUE(SerializeAttr(prefixStr, nameStr, valueStr, aStr, !isJS),
                   false);

    if (addNSAttr) {
      NS_ASSERTION(!prefixStr.IsEmpty(),
                   "Namespaced attributes must have a prefix");
      NS_ENSURE_TRUE(SerializeAttr(xmlnsStr, prefixStr, uriStr, aStr, true),
                     false);
      PushNameSpaceDecl(prefixStr, uriStr, aOriginalElement);
    }
  }

  return true;
}

NS_IMETHODIMP
nsXMLContentSerializer::AppendElementStart(Element* aElement,
                                           Element* aOriginalElement) {
  NS_ENSURE_ARG(aElement);
  NS_ENSURE_STATE(mOutput);

  bool forceFormat = false;
  nsresult rv = NS_OK;
  if (!CheckElementStart(aElement, forceFormat, *mOutput, rv)) {
    // When we go to AppendElementEnd for this element, we're going to
    // MaybeLeaveFromPreContent().  So make sure to MaybeEnterInPreContent()
    // now, so our PreLevel() doesn't get confused.
    MaybeEnterInPreContent(aElement);
    return rv;
  }

  NS_ENSURE_SUCCESS(rv, rv);

  nsAutoString tagPrefix, tagLocalName, tagNamespaceURI;
  aElement->NodeInfo()->GetPrefix(tagPrefix);
  aElement->NodeInfo()->GetName(tagLocalName);
  aElement->NodeInfo()->GetNamespaceURI(tagNamespaceURI);

  uint32_t skipAttr =
      ScanNamespaceDeclarations(aElement, aOriginalElement, tagNamespaceURI);

  nsAtom* name = aElement->NodeInfo()->NameAtom();
  bool lineBreakBeforeOpen =
      LineBreakBeforeOpen(aElement->GetNameSpaceID(), name);

  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
    if (mColPos && lineBreakBeforeOpen) {
      NS_ENSURE_TRUE(AppendNewLineToString(*mOutput), NS_ERROR_OUT_OF_MEMORY);
    } else {
      NS_ENSURE_TRUE(MaybeAddNewlineForRootNode(*mOutput),
                     NS_ERROR_OUT_OF_MEMORY);
    }
    if (!mColPos) {
      NS_ENSURE_TRUE(AppendIndentation(*mOutput), NS_ERROR_OUT_OF_MEMORY);
    } else if (mAddSpace) {
      NS_ENSURE_TRUE(AppendToString(char16_t(' '), *mOutput),
                     NS_ERROR_OUT_OF_MEMORY);
      mAddSpace = false;
    }
  } else if (mAddSpace) {
    NS_ENSURE_TRUE(AppendToString(char16_t(' '), *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
    mAddSpace = false;
  } else {
    NS_ENSURE_TRUE(MaybeAddNewlineForRootNode(*mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
  }

  // Always reset to avoid false newlines in case MaybeAddNewlineForRootNode
  // wasn't called
  mAddNewlineForRootNode = false;

  bool addNSAttr;
  addNSAttr =
      ConfirmPrefix(tagPrefix, tagNamespaceURI, aOriginalElement, false);

  // Serialize the qualified name of the element
  NS_ENSURE_TRUE(AppendToString(kLessThan, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  if (!tagPrefix.IsEmpty()) {
    NS_ENSURE_TRUE(AppendToString(tagPrefix, *mOutput), NS_ERROR_OUT_OF_MEMORY);
    NS_ENSURE_TRUE(AppendToString(u":"_ns, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  }
  NS_ENSURE_TRUE(AppendToString(tagLocalName, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);

  MaybeEnterInPreContent(aElement);

  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
    NS_ENSURE_TRUE(IncrIndentation(name), NS_ERROR_OUT_OF_MEMORY);
  }

  NS_ENSURE_TRUE(
      SerializeAttributes(aElement, aOriginalElement, tagPrefix,
                          tagNamespaceURI, name, *mOutput, skipAttr, addNSAttr),
      NS_ERROR_OUT_OF_MEMORY);

  NS_ENSURE_TRUE(AppendEndOfElementStart(aElement, aOriginalElement, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);

  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel() &&
      LineBreakAfterOpen(aElement->GetNameSpaceID(), name)) {
    NS_ENSURE_TRUE(AppendNewLineToString(*mOutput), NS_ERROR_OUT_OF_MEMORY);
  }

  NS_ENSURE_TRUE(AfterElementStart(aElement, aOriginalElement, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);

  return NS_OK;
}

// aElement is the actual element we're outputting.  aOriginalElement is the one
// in the original DOM, which is the one we have to test for kids.
static bool ElementNeedsSeparateEndTag(Element* aElement,
                                       Element* aOriginalElement) {
  if (aOriginalElement->GetChildCount()) {
    // We have kids, so we need a separate end tag.  This needs to be checked on
    // aOriginalElement because that's the one that's actually in the DOM and
    // might have kids.
    return true;
  }

  if (!aElement->IsHTMLElement()) {
    // Empty non-HTML elements can just skip a separate end tag.
    return false;
  }

  // HTML container tags should have a separate end tag even if empty, per spec.
  // See
  // https://w3c.github.io/DOM-Parsing/#dfn-concept-xml-serialization-algorithm
  nsAtom* localName = aElement->NodeInfo()->NameAtom();
  bool isHTMLContainer = nsHTMLElement::IsContainer(
      nsHTMLTags::CaseSensitiveAtomTagToId(localName));
  return isHTMLContainer;
}

bool nsXMLContentSerializer::AppendEndOfElementStart(Element* aElement,
                                                     Element* aOriginalElement,
                                                     nsAString& aStr) {
  if (ElementNeedsSeparateEndTag(aElement, aOriginalElement)) {
    return AppendToString(kGreaterThan, aStr);
  }

  // We don't need a separate end tag.  For HTML elements (which at this point
  // must be non-containers), append a space before the '/', per spec.  See
  // https://w3c.github.io/DOM-Parsing/#dfn-concept-xml-serialization-algorithm
  if (aOriginalElement->IsHTMLElement()) {
    if (!AppendToString(kSpace, aStr)) {
      return false;
    }
  }

  return AppendToString(u"/>"_ns, aStr);
}

NS_IMETHODIMP
nsXMLContentSerializer::AppendElementEnd(Element* aElement,
                                         Element* aOriginalElement) {
  NS_ENSURE_ARG(aElement);
  NS_ENSURE_STATE(mOutput);

  nsIContent* content = aElement;

  bool forceFormat = false, outputElementEnd;
  outputElementEnd =
      CheckElementEnd(aElement, aOriginalElement, forceFormat, *mOutput);

  nsAtom* name = content->NodeInfo()->NameAtom();

  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
    DecrIndentation(name);
  }

  if (!outputElementEnd) {
    // Keep this in sync with the cleanup at the end of this method.
    PopNameSpaceDeclsFor(aElement);
    MaybeLeaveFromPreContent(content);
    MaybeFlagNewlineForRootNode(aElement);
    AfterElementEnd(content, *mOutput);
    return NS_OK;
  }

  nsAutoString tagPrefix, tagLocalName, tagNamespaceURI;

  aElement->NodeInfo()->GetPrefix(tagPrefix);
  aElement->NodeInfo()->GetName(tagLocalName);
  aElement->NodeInfo()->GetNamespaceURI(tagNamespaceURI);

#ifdef DEBUG
  bool debugNeedToPushNamespace =
#endif
      ConfirmPrefix(tagPrefix, tagNamespaceURI, aElement, false);
  NS_ASSERTION(!debugNeedToPushNamespace,
               "Can't push namespaces in closing tag!");

  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel()) {
    bool lineBreakBeforeClose =
        LineBreakBeforeClose(content->GetNameSpaceID(), name);

    if (mColPos && lineBreakBeforeClose) {
      NS_ENSURE_TRUE(AppendNewLineToString(*mOutput), NS_ERROR_OUT_OF_MEMORY);
    }
    if (!mColPos) {
      NS_ENSURE_TRUE(AppendIndentation(*mOutput), NS_ERROR_OUT_OF_MEMORY);
    } else if (mAddSpace) {
      NS_ENSURE_TRUE(AppendToString(char16_t(' '), *mOutput),
                     NS_ERROR_OUT_OF_MEMORY);
      mAddSpace = false;
    }
  } else if (mAddSpace) {
    NS_ENSURE_TRUE(AppendToString(char16_t(' '), *mOutput),
                   NS_ERROR_OUT_OF_MEMORY);
    mAddSpace = false;
  }

  NS_ENSURE_TRUE(AppendToString(kEndTag, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  if (!tagPrefix.IsEmpty()) {
    NS_ENSURE_TRUE(AppendToString(tagPrefix, *mOutput), NS_ERROR_OUT_OF_MEMORY);
    NS_ENSURE_TRUE(AppendToString(u":"_ns, *mOutput), NS_ERROR_OUT_OF_MEMORY);
  }
  NS_ENSURE_TRUE(AppendToString(tagLocalName, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);
  NS_ENSURE_TRUE(AppendToString(kGreaterThan, *mOutput),
                 NS_ERROR_OUT_OF_MEMORY);

  // Keep what follows in sync with the cleanup in the !outputElementEnd case.
  PopNameSpaceDeclsFor(aElement);

  MaybeLeaveFromPreContent(content);

  if ((mDoFormat || forceFormat) && !mDoRaw && !PreLevel() &&
      LineBreakAfterClose(content->GetNameSpaceID(), name)) {
    NS_ENSURE_TRUE(AppendNewLineToString(*mOutput), NS_ERROR_OUT_OF_MEMORY);
  } else {
    MaybeFlagNewlineForRootNode(aElement);
  }

  AfterElementEnd(content, *mOutput);

  return NS_OK;
}

NS_IMETHODIMP
nsXMLContentSerializer::Finish() {
  NS_ENSURE_STATE(mOutput);

  mOutput = nullptr;

  return NS_OK;
}

NS_IMETHODIMP
nsXMLContentSerializer::GetOutputLength(uint32_t& aLength) const {
  NS_ENSURE_STATE(mOutput);

  aLength = mOutput->Length();

  return NS_OK;
}

NS_IMETHODIMP
nsXMLContentSerializer::AppendDocumentStart(Document* aDocument) {
  NS_ENSURE_ARG_POINTER(aDocument);
  NS_ENSURE_STATE(mOutput);

  nsAutoString version, encoding, standalone;
  aDocument->GetXMLDeclaration(version, encoding, standalone);

  if (version.IsEmpty())
    return NS_OK;  // A declaration must have version, or there is no decl

  constexpr auto endQuote = u"\""_ns;

  *mOutput += u"<?xml version=\""_ns + version + endQuote;

  if (!mCharset.IsEmpty()) {
    *mOutput +=
        u" encoding=\""_ns + NS_ConvertASCIItoUTF16(mCharset) + endQuote;
  }
  // Otherwise just don't output an encoding attr.  Not that we expect
  // mCharset to ever be empty.
#ifdef DEBUG
  else {
    NS_WARNING("Empty mCharset?  How come?");
  }
#endif

  if (!standalone.IsEmpty()) {
    *mOutput += u" standalone=\""_ns + standalone + endQuote;
  }

  NS_ENSURE_TRUE(mOutput->AppendLiteral("?>", mozilla::fallible),
                 NS_ERROR_OUT_OF_MEMORY);
  mAddNewlineForRootNode = true;

  return NS_OK;
}

bool nsXMLContentSerializer::CheckElementStart(Element*, bool& aForceFormat,
                                               nsAString& aStr,
                                               nsresult& aResult) {
  aResult = NS_OK;
  aForceFormat = false;
  return true;
}

bool nsXMLContentSerializer::CheckElementEnd(Element* aElement,
                                             Element* aOriginalElement,
                                             bool& aForceFormat,
                                             nsAString& aStr) {
  // We don't output a separate end tag for empty element
  aForceFormat = false;
  return ElementNeedsSeparateEndTag(aElement, aOriginalElement);
}

bool nsXMLContentSerializer::AppendToString(const char16_t aChar,
                                            nsAString& aOutputStr) {
  if (mBodyOnly && !mInBody) {
    return true;
  }
  mColPos += 1;
  return aOutputStr.Append(aChar, mozilla::fallible);
}

bool nsXMLContentSerializer::AppendToString(const nsAString& aStr,
                                            nsAString& aOutputStr) {
  if (mBodyOnly && !mInBody) {
    return true;
  }
  mColPos += aStr.Length();
  return aOutputStr.Append(aStr, mozilla::fallible);
}

#define _ 0

// This table indexes into kEntityStrings[].
const uint8_t nsXMLContentSerializer::kEntities[] = {
    // clang-format off
  _, _, _, _, _, _, _, _, _, _,
  _, _, _, _, _, _, _, _, _, _,
  _, _, _, _, _, _, _, _, _, _,
  _, _, _, _, _, _, _, _, 2, _,
  _, _, _, _, _, _, _, _, _, _,
  _, _, _, _, _, _, _, _, _, _,
  3, _, 4
    // clang-format on
};

// This table indexes into kEntityStrings[].
const uint8_t nsXMLContentSerializer::kAttrEntities[] = {
    // clang-format off
  _, _, _, _, _, _, _, _, _, 5,
  6, _, _, 7, _, _, _, _, _, _,
  _, _, _, _, _, _, _, _, _, _,
  _, _, _, _, 1, _, _, _, 2, _,
  _, _, _, _, _, _, _, _, _, _,
  _, _, _, _, _, _, _, _, _, _,
  3, _, 4
    // clang-format on
};

#undef _

const char* const nsXMLContentSerializer::kEntityStrings[] = {
    /* 0 */ nullptr,
    /* 1 */ "&quot;",
    /* 2 */ "&amp;",
    /* 3 */ "&lt;",
    /* 4 */ "&gt;",
    /* 5 */ "&#9;",
    /* 6 */ "&#xA;",
    /* 7 */ "&#xD;",
};

bool nsXMLContentSerializer::AppendAndTranslateEntities(const nsAString& aStr,
                                                        nsAString& aOutputStr) {
  if (mInAttribute) {
    return AppendAndTranslateEntities<kGTVal>(aStr, aOutputStr, kAttrEntities,
                                              kEntityStrings);
  }

  return AppendAndTranslateEntities<kGTVal>(aStr, aOutputStr, kEntities,
                                            kEntityStrings);
}

/* static */
bool nsXMLContentSerializer::AppendAndTranslateEntities(
    const nsAString& aStr, nsAString& aOutputStr, const uint8_t aEntityTable[],
    uint16_t aMaxTableIndex, const char* const aStringTable[]) {
  nsReadingIterator<char16_t> done_reading;
  aStr.EndReading(done_reading);

  // for each chunk of |aString|...
  uint32_t advanceLength = 0;
  nsReadingIterator<char16_t> iter;

  for (aStr.BeginReading(iter); iter != done_reading;
       iter.advance(int32_t(advanceLength))) {
    uint32_t fragmentLength = done_reading - iter;
    const char16_t* c = iter.get();
    const char16_t* fragmentStart = c;
    const char16_t* fragmentEnd = c + fragmentLength;
    const char* entityText = nullptr;

    advanceLength = 0;
    // for each character in this chunk, check if it
    // needs to be replaced
    for (; c < fragmentEnd; c++, advanceLength++) {
      char16_t val = *c;
      if ((val <= aMaxTableIndex) && aEntityTable[val]) {
        entityText = aStringTable[aEntityTable[val]];
        break;
      }
    }

    NS_ENSURE_TRUE(
        aOutputStr.Append(fragmentStart, advanceLength, mozilla::fallible),
        false);
    if (entityText) {
      NS_ENSURE_TRUE(AppendASCIItoUTF16(mozilla::MakeStringSpan(entityText),
                                        aOutputStr, mozilla::fallible),
                     false);
      advanceLength++;
    }
  }

  return true;
}

bool nsXMLContentSerializer::MaybeAddNewlineForRootNode(nsAString& aStr) {
  if (mAddNewlineForRootNode) {
    return AppendNewLineToString(aStr);
  }

  return true;
}

void nsXMLContentSerializer::MaybeFlagNewlineForRootNode(nsINode* aNode) {
  nsINode* parent = aNode->GetParentNode();
  if (parent) {
    mAddNewlineForRootNode = parent->IsDocument();
  }
}

void nsXMLContentSerializer::MaybeEnterInPreContent(nsIContent* aNode) {
  // support of the xml:space attribute
  nsAutoString space;
  if (ShouldMaintainPreLevel() && aNode->IsElement() &&
      aNode->AsElement()->GetAttr(kNameSpaceID_XML, nsGkAtoms::space, space) &&
      space.EqualsLiteral("preserve")) {
    ++PreLevel();
  }
}

void nsXMLContentSerializer::MaybeLeaveFromPreContent(nsIContent* aNode) {
  // support of the xml:space attribute
  nsAutoString space;
  if (ShouldMaintainPreLevel() && aNode->IsElement() &&
      aNode->AsElement()->GetAttr(kNameSpaceID_XML, nsGkAtoms::space, space) &&
      space.EqualsLiteral("preserve")) {
    --PreLevel();
  }
}

bool nsXMLContentSerializer::AppendNewLineToString(nsAString& aStr) {
  bool result = AppendToString(mLineBreak, aStr);
  mMayIgnoreLineBreakSequence = true;
  mColPos = 0;
  mAddSpace = false;
  mIsIndentationAddedOnCurrentLine = false;
  return result;
}

bool nsXMLContentSerializer::AppendIndentation(nsAString& aStr) {
  mIsIndentationAddedOnCurrentLine = true;
  bool result = AppendToString(mIndent, aStr);
  mAddSpace = false;
  mMayIgnoreLineBreakSequence = false;
  return result;
}

bool nsXMLContentSerializer::IncrIndentation(nsAtom* aName) {
  // we want to keep the source readable
  if (mDoWrap &&
      mIndent.Length() >= uint32_t(mMaxColumn) - MIN_INDENTED_LINE_LENGTH) {
    ++mIndentOverflow;
  } else {
    return mIndent.AppendLiteral(INDENT_STRING, mozilla::fallible);
  }

  return true;
}

void nsXMLContentSerializer::DecrIndentation(nsAtom* aName) {
  if (mIndentOverflow)
    --mIndentOverflow;
  else
    mIndent.Cut(0, INDENT_STRING_LENGTH);
}

bool nsXMLContentSerializer::LineBreakBeforeOpen(int32_t aNamespaceID,
                                                 nsAtom* aName) {
  return mAddSpace;
}

bool nsXMLContentSerializer::LineBreakAfterOpen(int32_t aNamespaceID,
                                                nsAtom* aName) {
  return false;
}

bool nsXMLContentSerializer::LineBreakBeforeClose(int32_t aNamespaceID,
                                                  nsAtom* aName) {
  return mAddSpace;
}

bool nsXMLContentSerializer::LineBreakAfterClose(int32_t aNamespaceID,
                                                 nsAtom* aName) {
  return false;
}

bool nsXMLContentSerializer::AppendToStringConvertLF(const nsAString& aStr,
                                                     nsAString& aOutputStr) {
  if (mBodyOnly && !mInBody) {
    return true;
  }

  if (mDoRaw) {
    NS_ENSURE_TRUE(AppendToString(aStr, aOutputStr), false);
  } else {
    // Convert line-endings to mLineBreak
    uint32_t start = 0;
    uint32_t theLen = aStr.Length();
    while (start < theLen) {
      int32_t eol = aStr.FindChar('\n', start);
      if (eol == kNotFound) {
        nsDependentSubstring dataSubstring(aStr, start, theLen - start);
        NS_ENSURE_TRUE(AppendToString(dataSubstring, aOutputStr), false);
        start = theLen;
        // if there was a line break before this substring
        // AppendNewLineToString was called, so we should reverse
        // this flag
        mMayIgnoreLineBreakSequence = false;
      } else {
        nsDependentSubstring dataSubstring(aStr, start, eol - start);
        NS_ENSURE_TRUE(AppendToString(dataSubstring, aOutputStr), false);
        NS_ENSURE_TRUE(AppendNewLineToString(aOutputStr), false);
        start = eol + 1;
      }
    }
  }

  return true;
}

bool nsXMLContentSerializer::AppendFormatedWrapped_WhitespaceSequence(
    nsAString::const_char_iterator& aPos,
    const nsAString::const_char_iterator aEnd,
    const nsAString::const_char_iterator aSequenceStart,
    bool& aMayIgnoreStartOfLineWhitespaceSequence, nsAString& aOutputStr) {
  // Handle the complete sequence of whitespace.
  // Continue to iterate until we find the first non-whitespace char.
  // Updates "aPos" to point to the first unhandled char.
  // Also updates the aMayIgnoreStartOfLineWhitespaceSequence flag,
  // as well as the other "global" state flags.

  bool sawBlankOrTab = false;
  bool leaveLoop = false;

  do {
    switch (*aPos) {
      case ' ':
      case '\t':
        sawBlankOrTab = true;
        [[fallthrough]];
      case '\n':
        ++aPos;
        // do not increase mColPos,
        // because we will reduce the whitespace to a single char
        break;
      default:
        leaveLoop = true;
        break;
    }
  } while (!leaveLoop && aPos < aEnd);

  if (mAddSpace) {
    // if we had previously been asked to add space,
    // our situation has not changed
  } else if (!sawBlankOrTab && mMayIgnoreLineBreakSequence) {
    // nothing to do in the case where line breaks have already been added
    // before the call of AppendToStringWrapped
    // and only if we found line break in the sequence
    mMayIgnoreLineBreakSequence = false;
  } else if (aMayIgnoreStartOfLineWhitespaceSequence) {
    // nothing to do
    aMayIgnoreStartOfLineWhitespaceSequence = false;
  } else {
    if (sawBlankOrTab) {
      if (mDoWrap && mColPos + 1 >= mMaxColumn) {
        // no much sense in delaying, we only have one slot left,
        // let's write a break now
        bool result = aOutputStr.Append(mLineBreak, mozilla::fallible);
        mColPos = 0;
        mIsIndentationAddedOnCurrentLine = false;
        mMayIgnoreLineBreakSequence = true;
        NS_ENSURE_TRUE(result, false);
      } else {
        // do not write out yet, we may write out either a space or a linebreak
        // let's delay writing it out until we know more
        mAddSpace = true;
        ++mColPos;  // eat a slot of available space
      }
    } else {
      // Asian text usually does not contain spaces, therefore we should not
      // transform a linebreak into a space.
      // Since we only saw linebreaks, but no spaces or tabs,
      // let's write a linebreak now.
      NS_ENSURE_TRUE(AppendNewLineToString(aOutputStr), false);
    }
  }

  return true;
}

bool nsXMLContentSerializer::AppendWrapped_NonWhitespaceSequence(
    nsAString::const_char_iterator& aPos,
    const nsAString::const_char_iterator aEnd,
    const nsAString::const_char_iterator aSequenceStart,
    bool& aMayIgnoreStartOfLineWhitespaceSequence,
    bool& aSequenceStartAfterAWhiteSpace, nsAString& aOutputStr) {
  mMayIgnoreLineBreakSequence = false;
  aMayIgnoreStartOfLineWhitespaceSequence = false;

  // Handle the complete sequence of non-whitespace in this block
  // Iterate until we find the first whitespace char or an aEnd condition
  // Updates "aPos" to point to the first unhandled char.
  // Also updates the aMayIgnoreStartOfLineWhitespaceSequence flag,
  // as well as the other "global" state flags.

  bool thisSequenceStartsAtBeginningOfLine = !mColPos;
  bool onceAgainBecauseWeAddedBreakInFront = false;
  bool foundWhitespaceInLoop;
  uint32_t length, colPos;

  do {
    if (mColPos) {
      colPos = mColPos;
    } else {
      if (mDoFormat && !mDoRaw && !PreLevel() &&
          !onceAgainBecauseWeAddedBreakInFront) {
        colPos = mIndent.Length();
      } else
        colPos = 0;
    }
    foundWhitespaceInLoop = false;
    length = 0;
    // we iterate until the next whitespace character
    // or until we reach the maximum of character per line
    // or until the end of the string to add.
    do {
      if (*aPos == ' ' || *aPos == '\t' || *aPos == '\n') {
        foundWhitespaceInLoop = true;
        break;
      }

      ++aPos;
      ++length;
    } while ((!mDoWrap || colPos + length < mMaxColumn) && aPos < aEnd);

    // in the case we don't reached the end of the string, but we reached the
    // maxcolumn, we see if there is a whitespace after the maxcolumn if yes,
    // then we can append directly the string instead of appending a new line
    // etc.
    if (*aPos == ' ' || *aPos == '\t' || *aPos == '\n') {
      foundWhitespaceInLoop = true;
    }

    if (aPos == aEnd || foundWhitespaceInLoop) {
      // there is enough room for the complete block we found
      if (mDoFormat && !mColPos) {
        NS_ENSURE_TRUE(AppendIndentation(aOutputStr), false);
      } else if (mAddSpace) {
        bool result = aOutputStr.Append(char16_t(' '), mozilla::fallible);
        mAddSpace = false;
        NS_ENSURE_TRUE(result, false);
      }

      mColPos += length;
      NS_ENSURE_TRUE(aOutputStr.Append(aSequenceStart, aPos - aSequenceStart,
                                       mozilla::fallible),
                     false);

      // We have not yet reached the max column, we will continue to
      // fill the current line in the next outer loop iteration
      // (this one in AppendToStringWrapped)
      // make sure we return in this outer loop
      onceAgainBecauseWeAddedBreakInFront = false;
    } else {  // we reach the max column
      if (!thisSequenceStartsAtBeginningOfLine &&
          (mAddSpace || (!mDoFormat && aSequenceStartAfterAWhiteSpace))) {
        // when !mDoFormat, mAddSpace is not used, mAddSpace is always false
        // so, in the case where mDoWrap && !mDoFormat, if we want to enter in
        // this condition...

        // We can avoid to wrap. We try to add the whole block
        // in an empty new line

        NS_ENSURE_TRUE(AppendNewLineToString(aOutputStr), false);
        aPos = aSequenceStart;
        thisSequenceStartsAtBeginningOfLine = true;
        onceAgainBecauseWeAddedBreakInFront = true;
      } else {
        // we must wrap
        onceAgainBecauseWeAddedBreakInFront = false;
        bool foundWrapPosition = false;
        int32_t wrapPosition = 0;

        if (mAllowLineBreaking) {
          mozilla::intl::LineBreaker* lineBreaker =
              nsContentUtils::LineBreaker();

          wrapPosition =
              lineBreaker->Prev(aSequenceStart, (aEnd - aSequenceStart),
                                (aPos - aSequenceStart) + 1);
          if (wrapPosition != NS_LINEBREAKER_NEED_MORE_TEXT) {
            foundWrapPosition = true;
          } else {
            wrapPosition =
                lineBreaker->Next(aSequenceStart, (aEnd - aSequenceStart),
                                  (aPos - aSequenceStart));
            if (wrapPosition != NS_LINEBREAKER_NEED_MORE_TEXT) {
              foundWrapPosition = true;
            }
          }
        }

        if (foundWrapPosition) {
          if (!mColPos && mDoFormat) {
            NS_ENSURE_TRUE(AppendIndentation(aOutputStr), false);
          } else if (mAddSpace) {
            bool result = aOutputStr.Append(char16_t(' '), mozilla::fallible);
            mAddSpace = false;
            NS_ENSURE_TRUE(result, false);
          }
          NS_ENSURE_TRUE(aOutputStr.Append(aSequenceStart, wrapPosition,
                                           mozilla::fallible),
                         false);

          NS_ENSURE_TRUE(AppendNewLineToString(aOutputStr), false);
          aPos = aSequenceStart + wrapPosition;
          aMayIgnoreStartOfLineWhitespaceSequence = true;
        } else {
          // try some simple fallback logic
          // go forward up to the next whitespace position,
          // in the worst case this will be all the rest of the data

          // we update the mColPos variable with the length of
          // the part already parsed.
          mColPos += length;

          // now try to find the next whitespace
          do {
            if (*aPos == ' ' || *aPos == '\t' || *aPos == '\n') {
              break;
            }

            ++aPos;
            ++mColPos;
          } while (aPos < aEnd);

          if (mAddSpace) {
            bool result = aOutputStr.Append(char16_t(' '), mozilla::fallible);
            mAddSpace = false;
            NS_ENSURE_TRUE(result, false);
          }
          NS_ENSURE_TRUE(
              aOutputStr.Append(aSequenceStart, aPos - aSequenceStart,
                                mozilla::fallible),
              false);
        }
      }
      aSequenceStartAfterAWhiteSpace = false;
    }
  } while (onceAgainBecauseWeAddedBreakInFront);

  return true;
}

bool nsXMLContentSerializer::AppendToStringFormatedWrapped(
    const nsAString& aStr, nsAString& aOutputStr) {
  if (mBodyOnly && !mInBody) {
    return true;
  }

  nsAString::const_char_iterator pos, end, sequenceStart;

  aStr.BeginReading(pos);
  aStr.EndReading(end);

  bool sequenceStartAfterAWhitespace = false;
  if (pos < end) {
    nsAString::const_char_iterator end2;
    aOutputStr.EndReading(end2);
    --end2;
    if (*end2 == ' ' || *end2 == '\n' || *end2 == '\t') {
      sequenceStartAfterAWhitespace = true;
    }
  }

  // if the current line already has text on it, such as a tag,
  // leading whitespace is significant
  bool mayIgnoreStartOfLineWhitespaceSequence =
      (!mColPos ||
       (mIsIndentationAddedOnCurrentLine && sequenceStartAfterAWhitespace &&
        uint32_t(mColPos) == mIndent.Length()));

  while (pos < end) {
    sequenceStart = pos;

    // if beginning of a whitespace sequence
    if (*pos == ' ' || *pos == '\n' || *pos == '\t') {
      NS_ENSURE_TRUE(AppendFormatedWrapped_WhitespaceSequence(
                         pos, end, sequenceStart,
                         mayIgnoreStartOfLineWhitespaceSequence, aOutputStr),
                     false);
    } else {  // any other non-whitespace char
      NS_ENSURE_TRUE(
          AppendWrapped_NonWhitespaceSequence(
              pos, end, sequenceStart, mayIgnoreStartOfLineWhitespaceSequence,
              sequenceStartAfterAWhitespace, aOutputStr),
          false);
    }
  }

  return true;
}

bool nsXMLContentSerializer::AppendWrapped_WhitespaceSequence(
    nsAString::const_char_iterator& aPos,
    const nsAString::const_char_iterator aEnd,
    const nsAString::const_char_iterator aSequenceStart,
    nsAString& aOutputStr) {
  // Handle the complete sequence of whitespace.
  // Continue to iterate until we find the first non-whitespace char.
  // Updates "aPos" to point to the first unhandled char.
  mAddSpace = false;
  mIsIndentationAddedOnCurrentLine = false;

  bool leaveLoop = false;
  nsAString::const_char_iterator lastPos = aPos;

  do {
    switch (*aPos) {
      case ' ':
      case '\t':
        // if there are too many spaces on a line, we wrap
        if (mColPos >= mMaxColumn) {
          if (lastPos != aPos) {
            NS_ENSURE_TRUE(
                aOutputStr.Append(lastPos, aPos - lastPos, mozilla::fallible),
                false);
          }
          NS_ENSURE_TRUE(AppendToString(mLineBreak, aOutputStr), false);
          mColPos = 0;
          lastPos = aPos;
        }

        ++mColPos;
        ++aPos;
        break;
      case '\n':
        if (lastPos != aPos) {
          NS_ENSURE_TRUE(
              aOutputStr.Append(lastPos, aPos - lastPos, mozilla::fallible),
              false);
        }
        NS_ENSURE_TRUE(AppendToString(mLineBreak, aOutputStr), false);
        mColPos = 0;
        ++aPos;
        lastPos = aPos;
        break;
      default:
        leaveLoop = true;
        break;
    }
  } while (!leaveLoop && aPos < aEnd);

  if (lastPos != aPos) {
    NS_ENSURE_TRUE(
        aOutputStr.Append(lastPos, aPos - lastPos, mozilla::fallible), false);
  }

  return true;
}

bool nsXMLContentSerializer::AppendToStringWrapped(const nsAString& aStr,
                                                   nsAString& aOutputStr) {
  if (mBodyOnly && !mInBody) {
    return true;
  }

  nsAString::const_char_iterator pos, end, sequenceStart;

  aStr.BeginReading(pos);
  aStr.EndReading(end);

  // not used in this case, but needed by AppendWrapped_NonWhitespaceSequence
  bool mayIgnoreStartOfLineWhitespaceSequence = false;
  mMayIgnoreLineBreakSequence = false;

  bool sequenceStartAfterAWhitespace = false;
  if (pos < end && !aOutputStr.IsEmpty()) {
    nsAString::const_char_iterator end2;
    aOutputStr.EndReading(end2);
    --end2;
    if (*end2 == ' ' || *end2 == '\n' || *end2 == '\t') {
      sequenceStartAfterAWhitespace = true;
    }
  }

  while (pos < end) {
    sequenceStart = pos;

    // if beginning of a whitespace sequence
    if (*pos == ' ' || *pos == '\n' || *pos == '\t') {
      sequenceStartAfterAWhitespace = true;
      NS_ENSURE_TRUE(
          AppendWrapped_WhitespaceSequence(pos, end, sequenceStart, aOutputStr),
          false);
    } else {  // any other non-whitespace char
      NS_ENSURE_TRUE(
          AppendWrapped_NonWhitespaceSequence(
              pos, end, sequenceStart, mayIgnoreStartOfLineWhitespaceSequence,
              sequenceStartAfterAWhitespace, aOutputStr),
          false);
    }
  }

  return true;
}

bool nsXMLContentSerializer::ShouldMaintainPreLevel() const {
  // Only attempt to maintain the pre level for consumers who care about it.
  return !mDoRaw || (mFlags & nsIDocumentEncoder::OutputNoFormattingInPre);
}

bool nsXMLContentSerializer::MaybeSerializeIsValue(Element* aElement,
                                                   nsAString& aStr) {
  CustomElementData* ceData = aElement->GetCustomElementData();
  if (ceData) {
    nsAtom* isAttr = ceData->GetIs(aElement);
    if (isAttr && !aElement->HasAttr(kNameSpaceID_None, nsGkAtoms::is)) {
      NS_ENSURE_TRUE(aStr.AppendLiteral(" is=\"", mozilla::fallible), false);
      NS_ENSURE_TRUE(
          aStr.Append(nsDependentAtomString(isAttr), mozilla::fallible), false);
      NS_ENSURE_TRUE(aStr.AppendLiteral("\"", mozilla::fallible), false);
    }
  }

  return true;
}