Improve performance when there are many differences

Author: sdottaka

src/WinWebDiffLib/DOMUtils.hpp

@@ -7,6 +7,7 @@
 #include <rapidjson/prettywriter.h>
 #include <rapidjson/stringbuffer.h>
 #include <string>
+#include <unordered_map>
 
 using WDocument = rapidjson::GenericDocument<rapidjson::UTF16<>>;
 using WValue = rapidjson::GenericValue<rapidjson::UTF16<>>;
@@ -92,6 +93,32 @@ namespace domutils
 		}
 	}
 
+	void makeNodeIdToNodeMap(WValue& nodeTree, std::unordered_map<int, WValue*>& map)
+	{
+		map.insert_or_assign(nodeTree[L"nodeId"].GetInt(), &nodeTree);
+		if (nodeTree.HasMember(L"children") && nodeTree[L"children"].IsArray())
+		{
+			for (auto& child : nodeTree[L"children"].GetArray())
+			{
+				map.insert_or_assign(child[L"nodeId"].GetInt(), &child);
+				makeNodeIdToNodeMap(child, map);
+			}
+		}
+		if (nodeTree.HasMember(L"contentDocument"))
+		{
+			auto& contentDocument = nodeTree[L"contentDocument"];
+			map.insert_or_assign(contentDocument[L"nodeId"].GetInt(), &contentDocument);
+			makeNodeIdToNodeMap(contentDocument, map);
+		}
+	}
+
+	std::unordered_map<int, WValue*> makeNodeIdToNodeMap(WValue& nodeTree)
+	{
+		std::unordered_map<int, WValue*> map;
+		makeNodeIdToNodeMap(nodeTree, map);
+		return map;
+	}
+
 	std::pair<WValue*, WValue*> findNodeId(WValue& nodeTree, int nodeId)
 	{
 		if (nodeTree[L"nodeId"].GetInt() == nodeId)

src/WinWebDiffLib/DiffHighlighter.hpp

@@ -709,6 +709,9 @@ class Highlighter
 
 	void highlightNodes()
 	{
+		std::unordered_map<int, WValue*> map[3];
+		for (size_t pane = 0; pane < m_documents.size(); ++pane)
+			map[pane] = domutils::makeNodeIdToNodeMap(m_documents[pane][L"root"]);
 		for (size_t i = 0; i < m_diffInfoList.size(); ++i)
 		{
 			const auto& diffInfo = m_diffInfoList[i];
@@ -717,8 +720,7 @@ class Highlighter
 			std::vector<DiffInfo> wordDiffInfoList;
 			for (size_t pane = 0; pane < m_documents.size(); ++pane)
 			{
-				std::pair<WValue*, WValue*> pair = domutils::findNodeId(m_documents[pane][L"root"], diffInfo.nodeIds[pane]);
-				pvalues[pane] = pair.first;
+				pvalues[pane] = map[pane][diffInfo.nodeIds[pane]];
 				if (diffInfo.nodePos[pane] == 0 && pvalues[pane])
 					textSegments[pane].Make((*pvalues[pane])[L"nodeValue"].GetString(), m_diffOptions.ignoreNumbers);
 				else