org.htmlunit.html.HtmlDomTreeWalker Maven / Gradle / Ivy
/*
* Copyright (c) 2002-2024 Gargoyle Software Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.htmlunit.html;
import org.w3c.dom.DOMException;
import org.w3c.dom.Node;
import org.w3c.dom.traversal.NodeFilter;
/**
* In general this is an implementation of org.w3c.dom.traversal.TreeWalker.
* The class org.w3c.dom.traversal.TreeWalker is not available on Android
* therefore we have this impl as backend.
*
* @see
* DOM-Level-2-Traversal-Range
* @author Mike Dirolf
* @author Frank Danek
* @author Ahmed Ashour
* @author Ronald Brill
*/
public class HtmlDomTreeWalker {
private final DomNode root_;
private DomNode currentNode_;
private final int whatToShow_;
private final NodeFilter filter_;
private final boolean expandEntityReferences_;
/**
* Creates an instance.
*
* @param root The root node of the TreeWalker. Must not be
* {@code null}.
* @param whatToShow Flag specifying which types of nodes appear in the
* logical view of the TreeWalker. See {@link NodeFilter} for the
* set of possible Show_ values.
* @param filter The {@link NodeFilter} to be used with this TreeWalker,
* or {@code null} to indicate no filter.
* @param expandEntityReferences If false, the contents of
* EntityReference nodes are not present in the logical view.
* @throws DOMException on attempt to create a TreeWalker with a root that
* is {@code null}.
*/
public HtmlDomTreeWalker(final DomNode root, final int whatToShow, final NodeFilter filter,
final boolean expandEntityReferences) throws DOMException {
if (root == null) {
throw new IllegalArgumentException("root must not be null");
}
root_ = root;
whatToShow_ = whatToShow;
filter_ = filter;
expandEntityReferences_ = expandEntityReferences;
currentNode_ = root_;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#getRoot()
* @return the root node
*/
public DomNode getRoot() {
return root_;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#getWhatToShow()
* @return NodeFilter constant
*/
public int getWhatToShow() {
return whatToShow_;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#getFilter()
* @return the filter
*/
public NodeFilter getFilter() {
return filter_;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#getExpandEntityReferences()
* @return the ExpandEntityReferences setting
*/
public boolean getExpandEntityReferences() {
return expandEntityReferences_;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#getCurrentNode()
* @return the current node
*/
public DomNode getCurrentNode() {
return currentNode_;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#setCurrentNode(Node)
* @param currentNode the current node
*/
public void setCurrentNode(final Node currentNode) throws DOMException {
if (currentNode == null) {
throw new DOMException(DOMException.NOT_SUPPORTED_ERR,
"currentNode cannot be set to null");
}
currentNode_ = (DomNode) currentNode;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#nextNode()
* @return the next node
*/
public DomNode nextNode() {
final DomNode leftChild = getEquivalentLogical(currentNode_.getFirstChild(), false);
if (leftChild != null) {
currentNode_ = leftChild;
return leftChild;
}
final DomNode rightSibling = getEquivalentLogical(currentNode_.getNextSibling(), false);
if (rightSibling != null) {
currentNode_ = rightSibling;
return rightSibling;
}
final DomNode uncle = getFirstUncleNode(currentNode_);
if (uncle != null) {
currentNode_ = uncle;
return uncle;
}
return null;
}
/**
* Helper method to get the first uncle node in document order (preorder
* traversal) from the given node.
*/
private DomNode getFirstUncleNode(final DomNode n) {
if (n == root_ || n == null) {
return null;
}
final DomNode parent = n.getParentNode();
if (parent == null) {
return null;
}
final DomNode uncle = getEquivalentLogical(parent.getNextSibling(), false);
if (uncle != null) {
return uncle;
}
return getFirstUncleNode(parent);
}
/**
* Recursively find the logical node occupying the same position as this
* _actual_ node. It could be the same node, a different node, or null
* depending on filtering.
*
* @param n The actual node we are trying to find the "equivalent" of
* @param lookLeft If true, traverse the tree in the left direction. If
* false, traverse the tree to the right.
* @return the logical node in the same position as n
*/
private DomNode getEquivalentLogical(final DomNode n, final boolean lookLeft) {
// Base cases
if (n == null) {
return null;
}
if (isNodeVisible(n)) {
return n;
}
// If a node is skipped, try getting one of its descendants
if (isNodeSkipped(n)) {
final DomNode child;
if (lookLeft) {
child = getEquivalentLogical(n.getLastChild(), lookLeft);
}
else {
child = getEquivalentLogical(n.getFirstChild(), lookLeft);
}
if (child != null) {
return child;
}
}
// If this node is rejected or has no descendants that will work, go
// to its sibling.
return getSibling(n, lookLeft);
}
/**
* Returns whether the node is visible by the TreeWalker.
*/
private boolean isNodeVisible(final Node n) {
if (acceptNode(n) == NodeFilter.FILTER_ACCEPT) {
if (filter_ == null || filter_.acceptNode(n) == NodeFilter.FILTER_ACCEPT) {
return expandEntityReferences_ || n.getParentNode() == null
|| n.getParentNode().getNodeType() != Node.ENTITY_REFERENCE_NODE;
}
}
return false;
}
/**
* Test whether a specified node is visible in the logical view of a
* TreeWalker, based solely on the whatToShow constant.
*
* @param n The node to check to see if it should be shown or not
* @return a constant to determine whether the node is accepted, rejected,
* or skipped.
*/
private short acceptNode(final Node n) {
final int flag = getFlagForNode(n);
if ((whatToShow_ & flag) != 0) {
return NodeFilter.FILTER_ACCEPT;
}
// Skip, don't reject.
return NodeFilter.FILTER_SKIP;
}
/**
* INTERNAL API - SUBJECT TO CHANGE AT ANY TIME - USE AT YOUR OWN RISK.
*
* Given a {@link Node}, return the appropriate constant for whatToShow.
*
* @param node the node
* @return the whatToShow constant for the type of specified node
*/
public static int getFlagForNode(final Node node) {
switch (node.getNodeType()) {
case Node.ELEMENT_NODE:
return NodeFilter.SHOW_ELEMENT;
case Node.ATTRIBUTE_NODE:
return NodeFilter.SHOW_ATTRIBUTE;
case Node.TEXT_NODE:
return NodeFilter.SHOW_TEXT;
case Node.CDATA_SECTION_NODE:
return NodeFilter.SHOW_CDATA_SECTION;
case Node.ENTITY_REFERENCE_NODE:
return NodeFilter.SHOW_ENTITY_REFERENCE;
case Node.ENTITY_NODE:
return NodeFilter.SHOW_ENTITY;
case Node.PROCESSING_INSTRUCTION_NODE:
return NodeFilter.SHOW_PROCESSING_INSTRUCTION;
case Node.COMMENT_NODE:
return NodeFilter.SHOW_COMMENT;
case Node.DOCUMENT_NODE:
return NodeFilter.SHOW_DOCUMENT;
case Node.DOCUMENT_TYPE_NODE:
return NodeFilter.SHOW_DOCUMENT_TYPE;
case Node.DOCUMENT_FRAGMENT_NODE:
return NodeFilter.SHOW_DOCUMENT_FRAGMENT;
case Node.NOTATION_NODE:
return NodeFilter.SHOW_NOTATION;
default:
return 0;
}
}
/* Returns whether the node is skipped by the TreeWalker. */
private boolean isNodeSkipped(final Node n) {
return !isNodeVisible(n) && !isNodeRejected(n);
}
/* Returns whether the node is rejected by the TreeWalker. */
private boolean isNodeRejected(final Node n) {
if (acceptNode(n) == NodeFilter.FILTER_REJECT) {
return true;
}
if (filter_ != null && filter_.acceptNode(n) == NodeFilter.FILTER_REJECT) {
return true;
}
return !expandEntityReferences_ && n.getParentNode() != null
&& n.getParentNode().getNodeType() == Node.ENTITY_REFERENCE_NODE;
}
// Helper method for getEquivalentLogical
private DomNode getSibling(final DomNode n, final boolean lookLeft) {
if (n == null) {
return null;
}
if (isNodeVisible(n)) {
return null;
}
final DomNode sibling;
if (lookLeft) {
sibling = n.getPreviousSibling();
}
else {
sibling = n.getNextSibling();
}
if (sibling == null) {
// If this node has no logical siblings at or below it's "level", it might have one above
if (n == root_) {
return null;
}
return getSibling(n.getParentNode(), lookLeft);
}
return getEquivalentLogical(sibling, lookLeft);
}
/**
* @see org.w3c.dom.traversal.TreeWalker#nextSibling()
* @return the next sibling node
*/
public DomNode nextSibling() {
if (currentNode_ == root_) {
return null;
}
final DomNode newNode = getEquivalentLogical(currentNode_.getNextSibling(), false);
if (newNode != null) {
currentNode_ = newNode;
}
return newNode;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#parentNode()
* @return the parent node
*/
public DomNode parentNode() {
if (currentNode_ == root_) {
return null;
}
DomNode newNode = currentNode_;
do {
newNode = newNode.getParentNode();
}
while (newNode != null && !isNodeVisible(newNode) && newNode != root_);
if (newNode == null || !isNodeVisible(newNode)) {
return null;
}
currentNode_ = newNode;
return newNode;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#previousSibling()
* @return the previous sibling node
*/
public DomNode previousSibling() {
if (currentNode_ == root_) {
return null;
}
final DomNode newNode = getEquivalentLogical(currentNode_.getPreviousSibling(), true);
if (newNode != null) {
currentNode_ = newNode;
}
return newNode;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#lastChild()
* @return the last child node
*/
public DomNode lastChild() {
final DomNode newNode = getEquivalentLogical(currentNode_.getLastChild(), true);
if (newNode != null) {
currentNode_ = newNode;
}
return newNode;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#previousNode()
* @return the previous node
*/
public DomNode previousNode() {
final DomNode newNode = getPreviousNode(currentNode_);
if (newNode != null) {
currentNode_ = newNode;
}
return newNode;
}
/**
* Helper method to get the previous node in document order (preorder
* traversal) from the given node.
*/
private DomNode getPreviousNode(final DomNode n) {
if (n == root_) {
return null;
}
final DomNode left = getEquivalentLogical(n.getPreviousSibling(), true);
if (left == null) {
final DomNode parent = n.getParentNode();
if (parent == null) {
return null;
}
if (isNodeVisible(parent)) {
return parent;
}
}
DomNode follow = left;
if (follow != null) {
while (follow.hasChildNodes()) {
final DomNode toFollow = getEquivalentLogical(follow.getLastChild(), true);
if (toFollow == null) {
break;
}
follow = toFollow;
}
}
return follow;
}
/**
* @see org.w3c.dom.traversal.TreeWalker#firstChild()
* @return the first child node
*/
public DomNode firstChild() {
final DomNode newNode = getEquivalentLogical(currentNode_.getFirstChild(), false);
if (newNode != null) {
currentNode_ = newNode;
}
return newNode;
}
}
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