Source/WebCore/inspector/DOMPatchSupport.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following disclaimer
  * in the documentation and/or other materials provided with the
  * distribution.
  *     * Neither the name of Google Inc. nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "DOMPatchSupport.h"

 #include "Attribute.h"
 #include "DOMEditor.h"
 #include "Document.h"
 #include "DocumentFragment.h"
 #include "ElementInlines.h"
 #include "HTMLDocument.h"
 #include "HTMLDocumentParser.h"
 #include "HTMLElement.h"
 #include "HTMLHeadElement.h"
 #include "HTMLNames.h"
 #include "InspectorHistory.h"
 #include "Node.h"
 #include "XMLDocument.h"
 #include "XMLDocumentParser.h"
 #include <wtf/Deque.h>
 #include <wtf/HashTraits.h>
 #include <wtf/RefPtr.h>
 #include <wtf/SHA1.h>
 #include <wtf/text/Base64.h>
 #include <wtf/text/CString.h>

 namespace WebCore {

 using HTMLNames::bodyTag;
 using HTMLNames::headTag;
 using HTMLNames::htmlTag;

 struct DOMPatchSupport::Digest {
     WTF_MAKE_STRUCT_FAST_ALLOCATED;

     String sha1;
     String attrsSHA1;
     Node* node;
     Vector<std::unique_ptr<Digest>> children;
 };

 DOMPatchSupport::DOMPatchSupport(DOMEditor& domEditor, Document& document)
     : m_domEditor(domEditor)
     , m_document(document)
 {
 }

 void DOMPatchSupport::patchDocument(const String& markup)
 {
     RefPtr<Document> newDocument;
     if (m_document.isHTMLDocument())
         newDocument = HTMLDocument::create(nullptr, m_document.settings(), URL(), { });
     else if (m_document.isXHTMLDocument())
         newDocument = XMLDocument::createXHTML(nullptr, m_document.settings(), URL());
     else if (m_document.isSVGDocument())
         newDocument = XMLDocument::create(nullptr, m_document.settings(), URL());

     ASSERT(newDocument);
     RefPtr<DocumentParser> parser;
     if (newDocument->isHTMLDocument())
         parser = HTMLDocumentParser::create(static_cast<HTMLDocument&>(*newDocument));
     else
         parser = XMLDocumentParser::create(*newDocument, nullptr);
     parser->insert(markup); // Use insert() so that the parser will not yield.
     parser->finish();
     parser->detach();

     if (!m_document.documentElement())
         return;
     if (!newDocument->documentElement())
         return;

     std::unique_ptr<Digest> oldInfo = createDigest(*m_document.documentElement(), nullptr);
     std::unique_ptr<Digest> newInfo = createDigest(*newDocument->documentElement(), &m_unusedNodesMap);

     if (innerPatchNode(*oldInfo, *newInfo).hasException()) {
         Ref document { m_document };
         // Fall back to rewrite.
         document->write(nullptr, markup);
         document->close();
     }
 }

 ExceptionOr<Node*> DOMPatchSupport::patchNode(Node& node, const String& markup)
 {
     // Don't parse <html> as a fragment.
     if (node.isDocumentNode() || (node.parentNode() && node.parentNode()->isDocumentNode())) {
         patchDocument(markup);
         return nullptr;
     }

     Node* previousSibling = node.previousSibling();
     // FIXME: This code should use one of createFragment* in markup.h
     auto fragment = DocumentFragment::create(m_document);
     if (m_document.isHTMLDocument())
         fragment->parseHTML(markup, node.parentElement() ? node.parentElement() : m_document.documentElement());
     else
         fragment->parseXML(markup, node.parentElement() ? node.parentElement() : m_document.documentElement());

     // Compose the old list.
     auto* parentNode = node.parentNode();
     Vector<std::unique_ptr<Digest>> oldList;
     for (Node* child = parentNode->firstChild(); child; child = child->nextSibling())
         oldList.append(createDigest(*child, nullptr));

     // Compose the new list.
     Vector<std::unique_ptr<Digest>> newList;
     for (Node* child = parentNode->firstChild(); child != &node; child = child->nextSibling())
         newList.append(createDigest(*child, nullptr));
     for (Node* child = fragment->firstChild(); child; child = child->nextSibling()) {
         if (child->hasTagName(headTag) && !child->firstChild() && !markup.containsIgnoringASCIICase("</head>"_s))
             continue; // HTML5 parser inserts empty <head> tag whenever it parses <body>
         if (child->hasTagName(bodyTag) && !child->firstChild() && !markup.containsIgnoringASCIICase("</body>"_s))
             continue; // HTML5 parser inserts empty <body> tag whenever it parses </head>
         newList.append(createDigest(*child, &m_unusedNodesMap));
     }
     for (Node* child = node.nextSibling(); child; child = child->nextSibling())
         newList.append(createDigest(*child, nullptr));

     if (innerPatchChildren(*parentNode, oldList, newList).hasException()) {
         // Fall back to total replace.
         auto result = m_domEditor.replaceChild(*parentNode, fragment.get(), node);
         if (result.hasException())
             return result.releaseException();
     }
     return previousSibling ? previousSibling->nextSibling() : parentNode->firstChild();
 }

 ExceptionOr<void> DOMPatchSupport::innerPatchNode(Digest& oldDigest, Digest& newDigest)
 {
     if (oldDigest.sha1 == newDigest.sha1)
         return { };

     auto& oldNode = *oldDigest.node;
     auto& newNode = *newDigest.node;

     if (newNode.nodeType() != oldNode.nodeType() || newNode.nodeName() != oldNode.nodeName())
         return m_domEditor.replaceChild(*oldNode.parentNode(), newNode, oldNode);

     if (oldNode.nodeValue() != newNode.nodeValue()) {
         auto result = m_domEditor.setNodeValue(oldNode, newNode.nodeValue());
         if (result.hasException())
             return result.releaseException();
     }

     if (!is<Element>(oldNode))
         return { };

     // Patch attributes
     auto& oldElement = downcast<Element>(oldNode);
     auto& newElement = downcast<Element>(newNode);
     if (oldDigest.attrsSHA1 != newDigest.attrsSHA1) {
         // FIXME: Create a function in Element for removing all properties. Take in account whether did/willModifyAttribute are important.
         if (oldElement.hasAttributesWithoutUpdate()) {
             while (oldElement.attributeCount()) {
                 auto result = m_domEditor.removeAttribute(oldElement, oldElement.attributeAt(0).localName());
                 if (result.hasException())
                     return result.releaseException();
             }
         }

         // FIXME: Create a function in Element for copying properties. cloneDataFromElement() is close but not enough for this case.
         if (newElement.hasAttributesWithoutUpdate()) {
             for (auto& attribute : newElement.attributesIterator()) {
                 auto result = m_domEditor.setAttribute(oldElement, attribute.name().localName(), attribute.value());
                 if (result.hasException())
                     return result.releaseException();
             }
         }
     }

     auto result = innerPatchChildren(oldElement, oldDigest.children, newDigest.children);
     m_unusedNodesMap.remove(newDigest.sha1);
     return result;
 }

 std::pair<DOMPatchSupport::ResultMap, DOMPatchSupport::ResultMap>
 DOMPatchSupport::diff(const Vector<std::unique_ptr<Digest>>& oldList, const Vector<std::unique_ptr<Digest>>& newList)
 {
     ResultMap newMap(newList.size());
     ResultMap oldMap(oldList.size());

     for (auto& result : oldMap) {
         result.first = nullptr;
         result.second = 0;
     }

     for (auto& result : newMap) {
         result.first = nullptr;
         result.second = 0;
     }

     // Trim head and tail.
     for (size_t i = 0; i < oldList.size() && i < newList.size() && oldList[i]->sha1 == newList[i]->sha1; ++i) {
         oldMap[i].first = oldList[i].get();
         oldMap[i].second = i;
         newMap[i].first = newList[i].get();
         newMap[i].second = i;
     }
     for (size_t i = 0; i < oldList.size() && i < newList.size() && oldList[oldList.size() - i - 1]->sha1 == newList[newList.size() - i - 1]->sha1; ++i) {
         size_t oldIndex = oldList.size() - i - 1;
         size_t newIndex = newList.size() - i - 1;
         oldMap[oldIndex].first = oldList[oldIndex].get();
         oldMap[oldIndex].second = newIndex;
         newMap[newIndex].first = newList[newIndex].get();
         newMap[newIndex].second = oldIndex;
     }

     typedef HashMap<String, Vector<size_t>> DiffTable;
     DiffTable newTable;
     DiffTable oldTable;

     for (size_t i = 0; i < newList.size(); ++i)
         newTable.add(newList[i]->sha1, Vector<size_t>()).iterator->value.append(i);

     for (size_t i = 0; i < oldList.size(); ++i)
         oldTable.add(oldList[i]->sha1, Vector<size_t>()).iterator->value.append(i);

     for (auto& newEntry : newTable) {
         if (newEntry.value.size() != 1)
             continue;

         auto oldIt = oldTable.find(newEntry.key);
         if (oldIt == oldTable.end() || oldIt->value.size() != 1)
             continue;

         newMap[newEntry.value[0]] = std::make_pair(newList[newEntry.value[0]].get(), oldIt->value[0]);
         oldMap[oldIt->value[0]] = std::make_pair(oldList[oldIt->value[0]].get(), newEntry.value[0]);
     }

     for (size_t i = 0; newList.size() > 0 && i < newList.size() - 1; ++i) {
         if (!newMap[i].first || newMap[i + 1].first)
             continue;

         size_t j = newMap[i].second + 1;
         if (j < oldMap.size() && !oldMap[j].first && newList[i + 1]->sha1 == oldList[j]->sha1) {
             newMap[i + 1] = std::make_pair(newList[i + 1].get(), j);
             oldMap[j] = std::make_pair(oldList[j].get(), i + 1);
         }
     }

     for (size_t i = newList.size() - 1; newList.size() > 0 && i > 0; --i) {
         if (!newMap[i].first || newMap[i - 1].first || newMap[i].second <= 0)
             continue;

         size_t j = newMap[i].second - 1;
         if (!oldMap[j].first && newList[i - 1]->sha1 == oldList[j]->sha1) {
             newMap[i - 1] = std::make_pair(newList[i - 1].get(), j);
             oldMap[j] = std::make_pair(oldList[j].get(), i - 1);
         }
     }

 #ifdef DEBUG_DOM_PATCH_SUPPORT
     dumpMap(oldMap, "OLD");
     dumpMap(newMap, "NEW");
 #endif

     return std::make_pair(oldMap, newMap);
 }

 ExceptionOr<void> DOMPatchSupport::innerPatchChildren(ContainerNode& parentNode, const Vector<std::unique_ptr<Digest>>& oldList, const Vector<std::unique_ptr<Digest>>& newList)
 {
     auto resultMaps = diff(oldList, newList);
     ResultMap& oldMap = resultMaps.first;
     ResultMap& newMap = resultMaps.second;

     Digest* oldHead = nullptr;
     Digest* oldBody = nullptr;

     // 1. First strip everything except for the nodes that retain. Collect pending merges.
     HashMap<Digest*, Digest*> merges;
     HashSet<size_t, IntHash<size_t>, WTF::UnsignedWithZeroKeyHashTraits<size_t>> usedNewOrdinals;
     for (size_t i = 0; i < oldList.size(); ++i) {
         if (oldMap[i].first) {
             if (!usedNewOrdinals.contains(oldMap[i].second)) {
                 usedNewOrdinals.add(oldMap[i].second);
                 continue;
             }
             oldMap[i].first = nullptr;
             oldMap[i].second = 0;
         }

         // Always match <head> and <body> tags with each other - we can't remove them from the DOM
         // upon patching.
         if (oldList[i]->node->hasTagName(headTag)) {
             oldHead = oldList[i].get();
             continue;
         }
         if (oldList[i]->node->hasTagName(bodyTag)) {
             oldBody = oldList[i].get();
             continue;
         }

         // Check if this change is between stable nodes. If it is, consider it as "modified".
         if (!m_unusedNodesMap.contains(oldList[i]->sha1) && (!i || oldMap[i - 1].first) && (i == oldMap.size() - 1 || oldMap[i + 1].first)) {
             size_t anchorCandidate = i ? oldMap[i - 1].second + 1 : 0;
             size_t anchorAfter = i == oldMap.size() - 1 ? anchorCandidate + 1 : oldMap[i + 1].second;
             if (anchorAfter - anchorCandidate == 1 && anchorCandidate < newList.size())
                 merges.set(newList[anchorCandidate].get(), oldList[i].get());
             else {
                 auto result = removeChildAndMoveToNew(*oldList[i]);
                 if (result.hasException())
                     return result.releaseException();
             }
         } else {
             auto result = removeChildAndMoveToNew(*oldList[i]);
             if (result.hasException())
                 return result.releaseException();
         }
     }

     // Mark retained nodes as used, do not reuse node more than once.
     HashSet<size_t, IntHash<size_t>, WTF::UnsignedWithZeroKeyHashTraits<size_t>> usedOldOrdinals;
     for (size_t i = 0; i < newList.size(); ++i) {
         if (!newMap[i].first)
             continue;
         size_t oldOrdinal = newMap[i].second;
         if (usedOldOrdinals.contains(oldOrdinal)) {
             // Do not map node more than once
             newMap[i].first = nullptr;
             newMap[i].second = 0;
             continue;
         }
         usedOldOrdinals.add(oldOrdinal);
         markNodeAsUsed(*newMap[i].first);
     }

     // Mark <head> and <body> nodes for merge.
     if (oldHead || oldBody) {
         for (size_t i = 0; i < newList.size(); ++i) {
             if (oldHead && newList[i]->node->hasTagName(headTag))
                 merges.set(newList[i].get(), oldHead);
             if (oldBody && newList[i]->node->hasTagName(bodyTag))
                 merges.set(newList[i].get(), oldBody);
         }
     }

     // 2. Patch nodes marked for merge.
     for (auto& merge : merges) {
         auto result = innerPatchNode(*merge.value, *merge.key);
         if (result.hasException())
             return result.releaseException();
     }

     // 3. Insert missing nodes.
     for (size_t i = 0; i < newMap.size(); ++i) {
         if (newMap[i].first || merges.contains(newList[i].get()))
             continue;
         auto result = insertBeforeAndMarkAsUsed(parentNode, *newList[i], parentNode.traverseToChildAt(i));
         if (result.hasException())
             return result.releaseException();
     }

     // 4. Then put all nodes that retained into their slots (sort by new index).
     for (size_t i = 0; i < oldMap.size(); ++i) {
         if (!oldMap[i].first)
             continue;
         RefPtr<Node> node = oldMap[i].first->node;
         auto* anchorNode = parentNode.traverseToChildAt(oldMap[i].second);
         if (node == anchorNode)
             continue;
         if (node->hasTagName(bodyTag) || node->hasTagName(headTag))
             continue; // Never move head or body, move the rest of the nodes around them.
         auto result = m_domEditor.insertBefore(parentNode, node.releaseNonNull(), anchorNode);
         if (result.hasException())
             return result.releaseException();
     }
     return { };
 }

 static void addStringToSHA1(SHA1& sha1, const String& string)
 {
     CString cString = string.utf8();
     sha1.addBytes(cString.dataAsUInt8Ptr(), cString.length());
 }

 std::unique_ptr<DOMPatchSupport::Digest> DOMPatchSupport::createDigest(Node& node, UnusedNodesMap* unusedNodesMap)
 {
     auto digest = makeUnique<Digest>();
     digest->node = &node;
     SHA1 sha1;

     auto nodeType = node.nodeType();
     sha1.addBytes(reinterpret_cast<const uint8_t*>(&nodeType), sizeof(nodeType));
     addStringToSHA1(sha1, node.nodeName());
     addStringToSHA1(sha1, node.nodeValue());

     if (node.nodeType() == Node::ELEMENT_NODE) {
         Node* child = node.firstChild();
         while (child) {
             std::unique_ptr<Digest> childInfo = createDigest(*child, unusedNodesMap);
             addStringToSHA1(sha1, childInfo->sha1);
             child = child->nextSibling();
             digest->children.append(WTFMove(childInfo));
         }
         auto& element = downcast<Element>(node);

         if (element.hasAttributesWithoutUpdate()) {
             SHA1 attrsSHA1;
             for (auto& attribute : element.attributesIterator()) {
                 addStringToSHA1(attrsSHA1, attribute.name().toString());
                 addStringToSHA1(attrsSHA1, attribute.value());
             }
             SHA1::Digest attrsHash;
             attrsSHA1.computeHash(attrsHash);
             digest->attrsSHA1 = base64EncodeToString(attrsHash.data(), 10);
             addStringToSHA1(sha1, digest->attrsSHA1);
         }
     }

     SHA1::Digest hash;
     sha1.computeHash(hash);
     digest->sha1 = base64EncodeToString(hash.data(), 10);
     if (unusedNodesMap)
         unusedNodesMap->add(digest->sha1, digest.get());

     return digest;
 }

 ExceptionOr<void> DOMPatchSupport::insertBeforeAndMarkAsUsed(ContainerNode& parentNode, Digest& digest, Node* anchor)
 {
     ASSERT(digest.node);
     auto result = m_domEditor.insertBefore(parentNode, *digest.node, anchor);
     markNodeAsUsed(digest);
     return result;
 }

 ExceptionOr<void> DOMPatchSupport::removeChildAndMoveToNew(Digest& oldDigest)
 {
     Ref<Node> oldNode = *oldDigest.node;
     ASSERT(oldNode->parentNode());
     auto result = m_domEditor.removeChild(*oldNode->parentNode(), oldNode);
     if (result.hasException())
         return result.releaseException();

     // Diff works within levels. In order not to lose the node identity when user
     // prepends his HTML with "<div>" (i.e. all nodes are shifted to the next nested level),
     // prior to dropping the original node on the floor, check whether new DOM has a digest
     // with matching sha1. If it does, replace it with the original DOM chunk. Chances are
     // high that it will get merged back into the original DOM during the further patching.
     auto it = m_unusedNodesMap.find(oldDigest.sha1);
     if (it != m_unusedNodesMap.end()) {
         auto& newDigest = *it->value;
         auto& newNode = *newDigest.node;
         auto result = m_domEditor.replaceChild(*newNode.parentNode(), oldNode.get(), newNode);
         if (result.hasException())
             return result.releaseException();
         newDigest.node = oldNode.ptr();
         markNodeAsUsed(newDigest);
         return { };
     }

     for (auto& child : oldDigest.children) {
         auto result = removeChildAndMoveToNew(*child);
         if (result.hasException())
             return result.releaseException();
     }
     return { };
 }

 void DOMPatchSupport::markNodeAsUsed(Digest& digest)
 {
     Deque<Digest*> queue;
     queue.append(&digest);
     while (!queue.isEmpty()) {
         auto& first = *queue.takeFirst();
         m_unusedNodesMap.remove(first.sha1);
         for (auto& child : first.children)
             queue.append(child.get());
     }
 }

 #ifdef DEBUG_DOM_PATCH_SUPPORT

 static String nodeName(Node* node)
 {
     if (node->document().isXHTMLDocument())
          return node->nodeName();
     return node->nodeName().convertToASCIILowercase();
 }

 void DOMPatchSupport::dumpMap(const ResultMap& map, const String& name)
 {
     fprintf(stderr, "\n\n");
     for (size_t i = 0; i < map.size(); ++i)
         fprintf(stderr, "%s[%lu]: %s (%p) - [%lu]\n", name.utf8().data(), i, map[i].first ? nodeName(map[i].first->m_node).utf8().data() : "", map[i].first, map[i].second);
 }

 #endif

 } // namespace WebCore
	/*
	* Copyright (C) 2012 Google Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met:
	*
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following disclaimer
	* in the documentation and/or other materials provided with the
	* distribution.
	* * Neither the name of Google Inc. nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "DOMPatchSupport.h"

	#include "Attribute.h"
	#include "DOMEditor.h"
	#include "Document.h"
	#include "DocumentFragment.h"
	#include "ElementInlines.h"
	#include "HTMLDocument.h"
	#include "HTMLDocumentParser.h"
	#include "HTMLElement.h"
	#include "HTMLHeadElement.h"
	#include "HTMLNames.h"
	#include "InspectorHistory.h"
	#include "Node.h"
	#include "XMLDocument.h"
	#include "XMLDocumentParser.h"
	#include <wtf/Deque.h>
	#include <wtf/HashTraits.h>
	#include <wtf/RefPtr.h>
	#include <wtf/SHA1.h>
	#include <wtf/text/Base64.h>
	#include <wtf/text/CString.h>

	namespace WebCore {

	using HTMLNames::bodyTag;
	using HTMLNames::headTag;
	using HTMLNames::htmlTag;

	struct DOMPatchSupport::Digest {
	WTF_MAKE_STRUCT_FAST_ALLOCATED;

	String sha1;
	String attrsSHA1;
	Node* node;
	Vector<std::unique_ptr<Digest>> children;
	};

	DOMPatchSupport::DOMPatchSupport(DOMEditor& domEditor, Document& document)
	: m_domEditor(domEditor)
	, m_document(document)
	{
	}

	void DOMPatchSupport::patchDocument(const String& markup)
	{
	RefPtr<Document> newDocument;
	if (m_document.isHTMLDocument())
	newDocument = HTMLDocument::create(nullptr, m_document.settings(), URL(), { });
	else if (m_document.isXHTMLDocument())
	newDocument = XMLDocument::createXHTML(nullptr, m_document.settings(), URL());
	else if (m_document.isSVGDocument())
	newDocument = XMLDocument::create(nullptr, m_document.settings(), URL());

	ASSERT(newDocument);
	RefPtr<DocumentParser> parser;
	if (newDocument->isHTMLDocument())
	parser = HTMLDocumentParser::create(static_cast<HTMLDocument&>(*newDocument));
	else
	parser = XMLDocumentParser::create(*newDocument, nullptr);
	parser->insert(markup); // Use insert() so that the parser will not yield.
	parser->finish();
	parser->detach();

	if (!m_document.documentElement())
	return;
	if (!newDocument->documentElement())
	return;

	std::unique_ptr<Digest> oldInfo = createDigest(*m_document.documentElement(), nullptr);
	std::unique_ptr<Digest> newInfo = createDigest(*newDocument->documentElement(), &m_unusedNodesMap);

	if (innerPatchNode(oldInfo, newInfo).hasException()) {
	Ref document { m_document };
	// Fall back to rewrite.
	document->write(nullptr, markup);
	document->close();
	}
	}

	ExceptionOr<Node*> DOMPatchSupport::patchNode(Node& node, const String& markup)
	{
	// Don't parse <html> as a fragment.
	if (node.isDocumentNode() \|\| (node.parentNode() && node.parentNode()->isDocumentNode())) {
	patchDocument(markup);
	return nullptr;
	}

	Node* previousSibling = node.previousSibling();
	// FIXME: This code should use one of createFragment* in markup.h
	auto fragment = DocumentFragment::create(m_document);
	if (m_document.isHTMLDocument())
	fragment->parseHTML(markup, node.parentElement() ? node.parentElement() : m_document.documentElement());
	else
	fragment->parseXML(markup, node.parentElement() ? node.parentElement() : m_document.documentElement());

	// Compose the old list.
	auto* parentNode = node.parentNode();
	Vector<std::unique_ptr<Digest>> oldList;
	for (Node* child = parentNode->firstChild(); child; child = child->nextSibling())
	oldList.append(createDigest(*child, nullptr));

	// Compose the new list.
	Vector<std::unique_ptr<Digest>> newList;
	for (Node* child = parentNode->firstChild(); child != &node; child = child->nextSibling())
	newList.append(createDigest(*child, nullptr));
	for (Node* child = fragment->firstChild(); child; child = child->nextSibling()) {
	if (child->hasTagName(headTag) && !child->firstChild() && !markup.containsIgnoringASCIICase("</head>"_s))
	continue; // HTML5 parser inserts empty <head> tag whenever it parses <body>
	if (child->hasTagName(bodyTag) && !child->firstChild() && !markup.containsIgnoringASCIICase("</body>"_s))
	continue; // HTML5 parser inserts empty <body> tag whenever it parses </head>
	newList.append(createDigest(*child, &m_unusedNodesMap));
	}
	for (Node* child = node.nextSibling(); child; child = child->nextSibling())
	newList.append(createDigest(*child, nullptr));

	if (innerPatchChildren(*parentNode, oldList, newList).hasException()) {
	// Fall back to total replace.
	auto result = m_domEditor.replaceChild(*parentNode, fragment.get(), node);
	if (result.hasException())
	return result.releaseException();
	}
	return previousSibling ? previousSibling->nextSibling() : parentNode->firstChild();
	}

	ExceptionOr<void> DOMPatchSupport::innerPatchNode(Digest& oldDigest, Digest& newDigest)
	{
	if (oldDigest.sha1 == newDigest.sha1)
	return { };

	auto& oldNode = *oldDigest.node;
	auto& newNode = *newDigest.node;

	if (newNode.nodeType() != oldNode.nodeType() \|\| newNode.nodeName() != oldNode.nodeName())
	return m_domEditor.replaceChild(*oldNode.parentNode(), newNode, oldNode);

	if (oldNode.nodeValue() != newNode.nodeValue()) {
	auto result = m_domEditor.setNodeValue(oldNode, newNode.nodeValue());
	if (result.hasException())
	return result.releaseException();
	}

	if (!is<Element>(oldNode))
	return { };

	// Patch attributes
	auto& oldElement = downcast<Element>(oldNode);
	auto& newElement = downcast<Element>(newNode);
	if (oldDigest.attrsSHA1 != newDigest.attrsSHA1) {
	// FIXME: Create a function in Element for removing all properties. Take in account whether did/willModifyAttribute are important.
	if (oldElement.hasAttributesWithoutUpdate()) {
	while (oldElement.attributeCount()) {
	auto result = m_domEditor.removeAttribute(oldElement, oldElement.attributeAt(0).localName());
	if (result.hasException())
	return result.releaseException();
	}
	}

	// FIXME: Create a function in Element for copying properties. cloneDataFromElement() is close but not enough for this case.
	if (newElement.hasAttributesWithoutUpdate()) {
	for (auto& attribute : newElement.attributesIterator()) {
	auto result = m_domEditor.setAttribute(oldElement, attribute.name().localName(), attribute.value());
	if (result.hasException())
	return result.releaseException();
	}
	}
	}

	auto result = innerPatchChildren(oldElement, oldDigest.children, newDigest.children);
	m_unusedNodesMap.remove(newDigest.sha1);
	return result;
	}

	std::pair<DOMPatchSupport::ResultMap, DOMPatchSupport::ResultMap>
	DOMPatchSupport::diff(const Vector<std::unique_ptr<Digest>>& oldList, const Vector<std::unique_ptr<Digest>>& newList)
	{
	ResultMap newMap(newList.size());
	ResultMap oldMap(oldList.size());

	for (auto& result : oldMap) {
	result.first = nullptr;
	result.second = 0;
	}

	for (auto& result : newMap) {
	result.first = nullptr;
	result.second = 0;
	}

	// Trim head and tail.
	for (size_t i = 0; i < oldList.size() && i < newList.size() && oldList[i]->sha1 == newList[i]->sha1; ++i) {
	oldMap[i].first = oldList[i].get();
	oldMap[i].second = i;
	newMap[i].first = newList[i].get();
	newMap[i].second = i;
	}
	for (size_t i = 0; i < oldList.size() && i < newList.size() && oldList[oldList.size() - i - 1]->sha1 == newList[newList.size() - i - 1]->sha1; ++i) {
	size_t oldIndex = oldList.size() - i - 1;
	size_t newIndex = newList.size() - i - 1;
	oldMap[oldIndex].first = oldList[oldIndex].get();
	oldMap[oldIndex].second = newIndex;
	newMap[newIndex].first = newList[newIndex].get();
	newMap[newIndex].second = oldIndex;
	}

	typedef HashMap<String, Vector<size_t>> DiffTable;
	DiffTable newTable;
	DiffTable oldTable;

	for (size_t i = 0; i < newList.size(); ++i)
	newTable.add(newList[i]->sha1, Vector<size_t>()).iterator->value.append(i);

	for (size_t i = 0; i < oldList.size(); ++i)
	oldTable.add(oldList[i]->sha1, Vector<size_t>()).iterator->value.append(i);

	for (auto& newEntry : newTable) {
	if (newEntry.value.size() != 1)
	continue;

	auto oldIt = oldTable.find(newEntry.key);
	if (oldIt == oldTable.end() \|\| oldIt->value.size() != 1)
	continue;

	newMap[newEntry.value[0]] = std::make_pair(newList[newEntry.value[0]].get(), oldIt->value[0]);
	oldMap[oldIt->value[0]] = std::make_pair(oldList[oldIt->value[0]].get(), newEntry.value[0]);
	}

	for (size_t i = 0; newList.size() > 0 && i < newList.size() - 1; ++i) {
	if (!newMap[i].first \|\| newMap[i + 1].first)
	continue;

	size_t j = newMap[i].second + 1;
	if (j < oldMap.size() && !oldMap[j].first && newList[i + 1]->sha1 == oldList[j]->sha1) {
	newMap[i + 1] = std::make_pair(newList[i + 1].get(), j);
	oldMap[j] = std::make_pair(oldList[j].get(), i + 1);
	}
	}

	for (size_t i = newList.size() - 1; newList.size() > 0 && i > 0; --i) {
	if (!newMap[i].first \|\| newMap[i - 1].first \|\| newMap[i].second <= 0)
	continue;

	size_t j = newMap[i].second - 1;
	if (!oldMap[j].first && newList[i - 1]->sha1 == oldList[j]->sha1) {
	newMap[i - 1] = std::make_pair(newList[i - 1].get(), j);
	oldMap[j] = std::make_pair(oldList[j].get(), i - 1);
	}
	}

	#ifdef DEBUG_DOM_PATCH_SUPPORT
	dumpMap(oldMap, "OLD");
	dumpMap(newMap, "NEW");
	#endif

	return std::make_pair(oldMap, newMap);
	}

	ExceptionOr<void> DOMPatchSupport::innerPatchChildren(ContainerNode& parentNode, const Vector<std::unique_ptr<Digest>>& oldList, const Vector<std::unique_ptr<Digest>>& newList)
	{
	auto resultMaps = diff(oldList, newList);
	ResultMap& oldMap = resultMaps.first;
	ResultMap& newMap = resultMaps.second;

	Digest* oldHead = nullptr;
	Digest* oldBody = nullptr;

	// 1. First strip everything except for the nodes that retain. Collect pending merges.
	HashMap<Digest, Digest> merges;
	HashSet<size_t, IntHash<size_t>, WTF::UnsignedWithZeroKeyHashTraits<size_t>> usedNewOrdinals;
	for (size_t i = 0; i < oldList.size(); ++i) {
	if (oldMap[i].first) {
	if (!usedNewOrdinals.contains(oldMap[i].second)) {
	usedNewOrdinals.add(oldMap[i].second);
	continue;
	}
	oldMap[i].first = nullptr;
	oldMap[i].second = 0;
	}

	// Always match <head> and <body> tags with each other - we can't remove them from the DOM
	// upon patching.
	if (oldList[i]->node->hasTagName(headTag)) {
	oldHead = oldList[i].get();
	continue;
	}
	if (oldList[i]->node->hasTagName(bodyTag)) {
	oldBody = oldList[i].get();
	continue;
	}

	// Check if this change is between stable nodes. If it is, consider it as "modified".
	if (!m_unusedNodesMap.contains(oldList[i]->sha1) && (!i \|\| oldMap[i - 1].first) && (i == oldMap.size() - 1 \|\| oldMap[i + 1].first)) {
	size_t anchorCandidate = i ? oldMap[i - 1].second + 1 : 0;
	size_t anchorAfter = i == oldMap.size() - 1 ? anchorCandidate + 1 : oldMap[i + 1].second;
	if (anchorAfter - anchorCandidate == 1 && anchorCandidate < newList.size())
	merges.set(newList[anchorCandidate].get(), oldList[i].get());
	else {
	auto result = removeChildAndMoveToNew(*oldList[i]);
	if (result.hasException())
	return result.releaseException();
	}
	} else {
	auto result = removeChildAndMoveToNew(*oldList[i]);
	if (result.hasException())
	return result.releaseException();
	}
	}

	// Mark retained nodes as used, do not reuse node more than once.
	HashSet<size_t, IntHash<size_t>, WTF::UnsignedWithZeroKeyHashTraits<size_t>> usedOldOrdinals;
	for (size_t i = 0; i < newList.size(); ++i) {
	if (!newMap[i].first)
	continue;
	size_t oldOrdinal = newMap[i].second;
	if (usedOldOrdinals.contains(oldOrdinal)) {
	// Do not map node more than once
	newMap[i].first = nullptr;
	newMap[i].second = 0;
	continue;
	}
	usedOldOrdinals.add(oldOrdinal);
	markNodeAsUsed(*newMap[i].first);
	}

	// Mark <head> and <body> nodes for merge.
	if (oldHead \|\| oldBody) {
	for (size_t i = 0; i < newList.size(); ++i) {
	if (oldHead && newList[i]->node->hasTagName(headTag))
	merges.set(newList[i].get(), oldHead);
	if (oldBody && newList[i]->node->hasTagName(bodyTag))
	merges.set(newList[i].get(), oldBody);
	}
	}

	// 2. Patch nodes marked for merge.
	for (auto& merge : merges) {
	auto result = innerPatchNode(merge.value, merge.key);
	if (result.hasException())
	return result.releaseException();
	}

	// 3. Insert missing nodes.
	for (size_t i = 0; i < newMap.size(); ++i) {
	if (newMap[i].first \|\| merges.contains(newList[i].get()))
	continue;
	auto result = insertBeforeAndMarkAsUsed(parentNode, *newList[i], parentNode.traverseToChildAt(i));
	if (result.hasException())
	return result.releaseException();
	}

	// 4. Then put all nodes that retained into their slots (sort by new index).
	for (size_t i = 0; i < oldMap.size(); ++i) {
	if (!oldMap[i].first)
	continue;
	RefPtr<Node> node = oldMap[i].first->node;
	auto* anchorNode = parentNode.traverseToChildAt(oldMap[i].second);
	if (node == anchorNode)
	continue;
	if (node->hasTagName(bodyTag) \|\| node->hasTagName(headTag))
	continue; // Never move head or body, move the rest of the nodes around them.
	auto result = m_domEditor.insertBefore(parentNode, node.releaseNonNull(), anchorNode);
	if (result.hasException())
	return result.releaseException();
	}
	return { };
	}

	static void addStringToSHA1(SHA1& sha1, const String& string)
	{
	CString cString = string.utf8();
	sha1.addBytes(cString.dataAsUInt8Ptr(), cString.length());
	}

	std::unique_ptr<DOMPatchSupport::Digest> DOMPatchSupport::createDigest(Node& node, UnusedNodesMap* unusedNodesMap)
	{
	auto digest = makeUnique<Digest>();
	digest->node = &node;
	SHA1 sha1;

	auto nodeType = node.nodeType();
	sha1.addBytes(reinterpret_cast<const uint8_t*>(&nodeType), sizeof(nodeType));
	addStringToSHA1(sha1, node.nodeName());
	addStringToSHA1(sha1, node.nodeValue());

	if (node.nodeType() == Node::ELEMENT_NODE) {
	Node* child = node.firstChild();
	while (child) {
	std::unique_ptr<Digest> childInfo = createDigest(*child, unusedNodesMap);
	addStringToSHA1(sha1, childInfo->sha1);
	child = child->nextSibling();
	digest->children.append(WTFMove(childInfo));
	}
	auto& element = downcast<Element>(node);

	if (element.hasAttributesWithoutUpdate()) {
	SHA1 attrsSHA1;
	for (auto& attribute : element.attributesIterator()) {
	addStringToSHA1(attrsSHA1, attribute.name().toString());
	addStringToSHA1(attrsSHA1, attribute.value());
	}
	SHA1::Digest attrsHash;
	attrsSHA1.computeHash(attrsHash);
	digest->attrsSHA1 = base64EncodeToString(attrsHash.data(), 10);
	addStringToSHA1(sha1, digest->attrsSHA1);
	}
	}

	SHA1::Digest hash;
	sha1.computeHash(hash);
	digest->sha1 = base64EncodeToString(hash.data(), 10);
	if (unusedNodesMap)
	unusedNodesMap->add(digest->sha1, digest.get());

	return digest;
	}

	ExceptionOr<void> DOMPatchSupport::insertBeforeAndMarkAsUsed(ContainerNode& parentNode, Digest& digest, Node* anchor)
	{
	ASSERT(digest.node);
	auto result = m_domEditor.insertBefore(parentNode, *digest.node, anchor);
	markNodeAsUsed(digest);
	return result;
	}

	ExceptionOr<void> DOMPatchSupport::removeChildAndMoveToNew(Digest& oldDigest)
	{
	Ref<Node> oldNode = *oldDigest.node;
	ASSERT(oldNode->parentNode());
	auto result = m_domEditor.removeChild(*oldNode->parentNode(), oldNode);
	if (result.hasException())
	return result.releaseException();

	// Diff works within levels. In order not to lose the node identity when user
	// prepends his HTML with "<div>" (i.e. all nodes are shifted to the next nested level),
	// prior to dropping the original node on the floor, check whether new DOM has a digest
	// with matching sha1. If it does, replace it with the original DOM chunk. Chances are
	// high that it will get merged back into the original DOM during the further patching.
	auto it = m_unusedNodesMap.find(oldDigest.sha1);
	if (it != m_unusedNodesMap.end()) {
	auto& newDigest = *it->value;
	auto& newNode = *newDigest.node;
	auto result = m_domEditor.replaceChild(*newNode.parentNode(), oldNode.get(), newNode);
	if (result.hasException())
	return result.releaseException();
	newDigest.node = oldNode.ptr();
	markNodeAsUsed(newDigest);
	return { };
	}

	for (auto& child : oldDigest.children) {
	auto result = removeChildAndMoveToNew(*child);
	if (result.hasException())
	return result.releaseException();
	}
	return { };
	}

	void DOMPatchSupport::markNodeAsUsed(Digest& digest)
	{
	Deque<Digest*> queue;
	queue.append(&digest);
	while (!queue.isEmpty()) {
	auto& first = *queue.takeFirst();
	m_unusedNodesMap.remove(first.sha1);
	for (auto& child : first.children)
	queue.append(child.get());
	}
	}

	#ifdef DEBUG_DOM_PATCH_SUPPORT

	static String nodeName(Node* node)
	{
	if (node->document().isXHTMLDocument())
	return node->nodeName();
	return node->nodeName().convertToASCIILowercase();
	}

	void DOMPatchSupport::dumpMap(const ResultMap& map, const String& name)
	{
	fprintf(stderr, "\n\n");
	for (size_t i = 0; i < map.size(); ++i)
	fprintf(stderr, "%s[%lu]: %s (%p) - [%lu]\n", name.utf8().data(), i, map[i].first ? nodeName(map[i].first->m_node).utf8().data() : "", map[i].first, map[i].second);
	}

	#endif

	} // namespace WebCore