pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / facet / src / java / org / apache / lucene / facet / search / PayloadIntDecodingIterator.java

diff --git a/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/facet/search/PayloadIntDecodingIterator.java b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/facet/search/PayloadIntDecodingIterator.java
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+package org.apache.lucene.facet.search;
+
+import java.io.IOException;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.Term;
+
+import org.apache.lucene.util.UnsafeByteArrayInputStream;
+import org.apache.lucene.util.encoding.IntDecoder;
+
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *     http://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.
+ */
+
+/**
+ * A payload deserializer comes with its own working space (buffer). One need to
+ * define the {@link IndexReader} and {@link Term} in which the payload resides.
+ * The iterator then consumes the payload information of each document and
+ * decodes it into categories. A typical use case of this class is:
+ * 
+ * <pre>
+ * IndexReader reader = [open your reader];
+ * Term t = new Term(&quot;field&quot;, &quot;where-payload-exists&quot;);
+ * CategoryListIterator cli = new PayloadIntDecodingIterator(reader, t);
+ * if (!cli.init()) {
+ *   // it means there are no payloads / documents associated with that term.
+ *   // Usually a sanity check. However, init() must be called.
+ * }
+ * DocIdSetIterator disi = [you usually iterate on something else, such as a Scorer];
+ * int doc;
+ * while ((doc = disi.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
+ *   cli.setdoc(doc);
+ *   long category;
+ *   while ((category = cli.nextCategory()) &lt; Integer.MAX_VALUE) {
+ *   }
+ * }
+ * </pre>
+ * 
+ * @lucene.experimental
+ */
+public class PayloadIntDecodingIterator implements CategoryListIterator {
+
+  private final UnsafeByteArrayInputStream ubais;
+  private final IntDecoder decoder;
+
+  private final IndexReader indexReader;
+  private final Term term;
+  private final PayloadIterator pi;
+  private final int hashCode;
+  
+  public PayloadIntDecodingIterator(IndexReader indexReader, Term term, IntDecoder decoder)
+      throws IOException {
+    this(indexReader, term, decoder, new byte[1024]);
+  }
+
+  public PayloadIntDecodingIterator(IndexReader indexReader, Term term, IntDecoder decoder,
+                                    byte[] buffer) throws IOException {
+    pi = new PayloadIterator(indexReader, term, buffer);
+    ubais = new UnsafeByteArrayInputStream();
+    this.decoder = decoder;
+    hashCode = indexReader.hashCode() ^ term.hashCode();
+    this.term = term;
+    this.indexReader = indexReader;
+  }
+
+  @Override
+  public boolean equals(Object other) {
+    if (!(other instanceof PayloadIntDecodingIterator)) {
+      return false;
+    }
+    PayloadIntDecodingIterator that = (PayloadIntDecodingIterator) other;
+    if (hashCode != that.hashCode) {
+      return false;
+    }
+    
+    // Hash codes are the same, check equals() to avoid cases of hash-collisions.
+    return indexReader.equals(that.indexReader) && term.equals(that.term);
+  }
+
+  @Override
+  public int hashCode() {
+    return hashCode;
+  }
+
+  public boolean init() throws IOException {
+    return pi.init();
+  }
+  
+  public long nextCategory() throws IOException {
+    return decoder.decode();
+  }
+
+  public boolean skipTo(int docId) throws IOException {
+    if (!pi.setdoc(docId)) {
+      return false;
+    }
+
+    // Initializing the decoding mechanism with the new payload data
+    ubais.reInit(pi.getBuffer(), 0, pi.getPayloadLength());
+    decoder.reInit(ubais);
+    return true;
+  }
+
+}