// $Id: CachingWrapperFilter.java 15368 2008-10-22 10:12:17Z hardy.ferentschik $
package org.hibernate.search.filter;
import java.io.IOException;
import java.util.BitSet;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Filter;
import org.slf4j.Logger;
import org.hibernate.search.util.LoggerFactory;
import org.hibernate.util.SoftLimitMRUCache;
/**
* A slightly different version of Lucene's original <code>CachingWrapperFilter</code> which
* uses <code>SoftReferences</code> instead of <code>WeakReferences</code> in order to cache
* the filter <code>BitSet</code>.
*
* @author Hardy Ferentschik
* @see org.apache.lucene.search.CachingWrapperFilter
* @see <a href="http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-174">HSEARCH-174</a>
*/
@SuppressWarnings("serial")
public class CachingWrapperFilter extends Filter {
private static final Logger log = LoggerFactory.make();
public static final int DEFAULT_SIZE = 5;
private final int size;
/**
* The cache using soft references in order to store the filter bit sets.
*/
private transient SoftLimitMRUCache cache;
private final Filter filter;
/**
* @param filter
* Filter to cache results of
*/
public CachingWrapperFilter(Filter filter) {
this(filter, DEFAULT_SIZE);
}
/**
* @param filter
* Filter to cache results of
*/
public CachingWrapperFilter(Filter filter, int size) {
this.filter = filter;
this.size = size;
}
public BitSet bits(IndexReader reader) throws IOException {
if (cache == null) {
log.debug("Initialising SoftLimitMRUCache with hard ref size of {}", size);
cache = new SoftLimitMRUCache(size);
}
//memory barrier ensure cache == null will not always stay true on concurrent threads
synchronized (cache) { // check cache
BitSet cached = (BitSet) cache.get(reader);
if (cached != null) {
return cached;
}
}
final BitSet bits = filter.bits(reader);
synchronized (cache) { // update cache
cache.put(reader, bits);
}
return bits;
}
public String toString() {
return this.getClass().getName() + "(" + filter + ")";
}
public boolean equals(Object o) {
if (!(o instanceof CachingWrapperFilter))
return false;
return this.filter.equals(((CachingWrapperFilter) o).filter);
}
public int hashCode() {
return filter.hashCode() ^ 0x1117BF25;
}
}