Calculate list of child elements in DomReader only once. Closes #342.

x-stream · Sep 27, 2023 · 94cb267 · 94cb267
1 parent 165514e
commit 94cb267
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diff --git a/xstream-distribution/src/content/changes.html b/xstream-distribution/src/content/changes.html
@@ -38,6 +38,7 @@ <h2>Minor changes</h2>
 	<ul>
 		<li>GHPR:#331, GHI:#326: Fix handling of empty java.util.concurrent.atomic.AtomicReference (by Alex Blekhman of Atlassian).</li>
 		<li>GHPR:#334: Fix remaining buffer size calculation in QuickWriter (by Higuchi Yuta).</li>
+		<li>GHI:#342: Optimize internal handling of children in DomReader avoiding O(n²) access times for siblings (by Shiang-Yun Yang).</li>
 	</ul>
 
 	<h1 id="1.4.20">1.4.20</h1>

diff --git a/xstream/src/java/com/thoughtworks/xstream/io/xml/DomReader.java b/xstream/src/java/com/thoughtworks/xstream/io/xml/DomReader.java
@@ -1,16 +1,17 @@
 /*
  * Copyright (C) 2004, 2005, 2006 Joe Walnes.
- * Copyright (C) 2006, 2007, 2009, 2011 XStream Committers.
+ * Copyright (C) 2006, 2007, 2009, 2011, 2023 XStream Committers.
  * All rights reserved.
  *
  * The software in this package is published under the terms of the BSD
  * style license a copy of which has been included with this distribution in
  * the LICENSE.txt file.
- * 
+ *
  * Created on 07. March 2004 by Joe Walnes
  */
 package com.thoughtworks.xstream.io.xml;
 
+import com.thoughtworks.xstream.core.util.FastStack;
 import com.thoughtworks.xstream.io.naming.NameCoder;
 
 import org.w3c.dom.Attr;
@@ -23,11 +24,13 @@
 import java.util.ArrayList;
 import java.util.List;
 
+
 public class DomReader extends AbstractDocumentReader {
 
     private Element currentElement;
     private StringBuffer textBuffer;
     private List childElements;
+    private final FastStack childrenStack;
 
     public DomReader(Element rootElement) {
         this(rootElement, new XmlFriendlyNameCoder());
@@ -43,6 +46,8 @@ public DomReader(Document document) {
     public DomReader(Element rootElement, NameCoder nameCoder) {
         super(rootElement, nameCoder);
         textBuffer = new StringBuffer();
+        childrenStack = new FastStack(16);
+        collectChildElements();
     }
 
     /**
@@ -117,6 +122,9 @@ protected int getChildCount() {
 
     protected void reassignCurrentElement(Object current) {
         currentElement = (Element) current;
+    }
+
+    private void collectChildElements() {
         NodeList childNodes = currentElement.getChildNodes();
         childElements = new ArrayList();
         for (int i = 0; i < childNodes.getLength(); i++) {
@@ -127,6 +135,17 @@ protected void reassignCurrentElement(Object current) {
         }
     }
 
+    public void moveDown() {
+        super.moveDown();
+        childrenStack.push(childElements);
+        collectChildElements();
+    }
+
+    public void moveUp() {
+        childElements = (List) childrenStack.pop();
+        super.moveUp();
+    }
+
     public String peekNextChild() {
         NodeList childNodes = currentElement.getChildNodes();
         for (int i = 0; i < childNodes.getLength(); i++) {