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xom-interest - Re: [XOM-interest] QName flyweights

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Subject: XOM API for Processing XML with Java

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  • From: norwoods <norwoods AT gbronline.com>
  • Cc: xom-interest AT lists.ibiblio.org
  • Subject: Re: [XOM-interest] QName flyweights
  • Date: Mon, 13 Jun 2005 08:29:39 -0700

here is another attempt at a cache. this uses an arraylist with binary search for the matching entry. it can return a QName object with the methods qName=QName3.newQName(name, uri); or qName=QName3.newQName(QName3.qualifyName(prefix, localName), uri);

norwod sisson
****************************
package nu.xom;

import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.util.ArrayList;

final class QName2 {
static ArrayList cache = new ArrayList();

private static final int trimDelayCount = 3;

private static int trimDelayCounter = 0;

private String localName;

private String name;

private String prefix;

private String uri;

private WeakReference reference;

private QName2(String name, String uri) {
this.name = name.intern();
this.uri = uri.intern();
}

public static synchronized QName2 newQName(String name, String uri) {
if (name == null) {
throw new NullPointerException();
}
if (uri == null)
uri = "";
int high = cache.size(), low = -1, probe;
Reference reference;
QName2 value;
while (high - low > 1) {
probe = (high + low) / 2;
reference = (WeakReference) cache.get(probe);
value = (QName2) reference.get();
if (value == null) {
cache.remove(probe);
high--;
break;
}
if (value.getQualifiedName().compareTo(name) > 0
&& (value.getNamespaceURI().compareTo(uri)) > 0)
high = probe;
else
low = probe;
}
if (low > -1) {
reference = (WeakReference) cache.get(low);
value = (QName2) reference.get();
if ((value.getQualifiedName().compareTo(name) == 0)
&& (value.getNamespaceURI().compareTo(uri) == 0))
return value;
}
value = new QName2(name, uri);
value.reference = new WeakReference(value);
cache.add(high, value.reference);
return value;
}

private void splitQualifiedName() {
int i = name.indexOf(':');
if (i < 0) {
prefix = "".intern();
localName = name.intern();
} else {
prefix = name.substring(0, i).intern();
localName = name.substring(i + 1).intern();
}
}

public boolean equals(QName2 qName) {
if (this == qName)
return true;
return (name.equals(qName.getQualifiedName()) && (uri.equals(qName
.getNamespaceURI())));
}

protected synchronized void finalize() {
cache.remove(reference);
reference.clear();
reference = null;
if (++trimDelayCounter >= trimDelayCount) {
cache.trimToSize();
trimDelayCounter = 0;
}
}

public String getLocalName() {
if (localName == null)
splitQualifiedName();
return localName;
}

public String getNamespacePrefix() {
if (prefix == null)
splitQualifiedName();
return prefix;
}

public String getNamespaceURI() {
return uri;
}

public String getQualifiedName() {
return name;
}

public int hashCode() {
return uri.hashCode() ^ name.hashCode();
}

public static String qualifyName(String prefix, String localName) {
if (prefix == null || prefix == "")
return localName;
return prefix + ":" + localName;
}
}




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