com.topologi.diffx.event.impl.XMLBranchEvent Maven / Gradle / Ivy
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/*
* This file is part of the DiffX library.
*
* For licensing information please see the file license.txt included in the release.
* A copy of this licence can also be found at
* http://www.opensource.org/licenses/artistic-license-2.0.php
*/
package com.topologi.diffx.event.impl;
import java.io.IOException;
import com.topologi.diffx.event.DiffXEvent;
import com.topologi.diffx.xml.XMLWriter;
/**
* A branch of XML data.
*
* A branch of XML data must start and end with the same element.
*
*
Implementation note: this class wraps an array of DiffX events and does not give
* access to this array, so it can be considered immutable.
*
* @author Christophe Lauret
* @version 27 March 2010
*/
public final class XMLBranchEvent extends DiffXEventBase implements DiffXEvent {
/**
* The array of Diff-X events that make up the branch.
*/
private final DiffXEvent[] branch;
/**
* Pre-calculated hashcode to speed up equal comparison.
*/
private final int hashCode;
/**
* Creates a new XML branch.
*
* @param events The array of events that make up the branch.
*/
public XMLBranchEvent(DiffXEvent[] events) {
this.branch = events;
this.hashCode = toHashCode(events);
}
@Override
public int hashCode() {
return this.hashCode;
}
/**
* Returns true if the diffX events in the branch are all equal.
*
* {@inheritDoc}
*/
@Override
public boolean equals(DiffXEvent e) {
if (e.getClass() != this.getClass()) return false;
if (e.hashCode() != this.hashCode) return false;
XMLBranchEvent be = (XMLBranchEvent)e;
// branch must have the same length
if (this.branch.length != be.branch.length) return false;
// every single event must be equal
for (int i = 0; i < this.branch.length; i++) {
if (!be.branch[i].equals(this.branch[i]))
return false;
}
// if we arrive here they are equal
return true;
}
/**
* Write the DiffX events in order.
*
* {@inheritDoc}
*/
@Override
public void toXML(XMLWriter xml) throws IOException {
for (DiffXEvent element : this.branch) {
element.toXML(xml);
}
}
@Override
public StringBuffer toXML(StringBuffer xml) throws NullPointerException {
for (DiffXEvent element : this.branch) {
element.toXML(xml);
}
return xml;
}
/**
* Calculates the hashcode for this event.
*
* @param events Events to calculate the value from.
* @return a number suitable as a hashcode.
*/
private static int toHashCode(DiffXEvent[] events) {
int hash = 17;
for (DiffXEvent e : events) {
hash = hash * 13 + (e != null? e.hashCode() : 0);
}
return hash;
}
}