pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/facet/search/PayloadIterator.java b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/facet/search/PayloadIterator.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.index.TermPositions;
+
+/**
+ * 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 utility class for iterating through a posting list of a given term and
+ * retrieving the payload of the first occurrence in every document. Comes with
+ * its own working space (buffer).
+ * 
+ * @lucene.experimental
+ */
+public class PayloadIterator {
+
+  protected byte[] buffer;
+  protected int payloadLength;
+
+  TermPositions tp;
+
+  private boolean hasMore;
+
+  public PayloadIterator(IndexReader indexReader, Term term)
+      throws IOException {
+    this(indexReader, term, new byte[1024]);
+  }
+
+  public PayloadIterator(IndexReader indexReader, Term term, byte[] buffer)
+      throws IOException {
+    this.buffer = buffer;
+    this.tp = indexReader.termPositions(term);
+  }
+
+  /**
+   * (re)initialize the iterator. Should be done before the first call to
+   * {@link #setdoc(int)}. Returns false if there is no category list found
+   * (no setdoc() will never return true).
+   */
+  public boolean init() throws IOException {
+    hasMore = tp.next();
+    return hasMore;
+  }
+
+  /**
+   * Skip forward to document docId. Return true if this document exists and
+   * has any payload.
+   * <P>
+   * Users should call this method with increasing docIds, and implementations
+   * can assume that this is the case.
+   */
+  public boolean setdoc(int docId) throws IOException {
+    if (!hasMore) {
+      return false;
+    }
+    
+    if (tp.doc() > docId) {
+      return false;
+    }
+
+    // making sure we have the requested document
+    if (tp.doc() < docId) {
+      // Skipping to requested document
+      if (!tp.skipTo(docId)) {
+        this.hasMore = false;
+        return false;
+      }
+
+      // If document not found (skipped to much)
+      if (tp.doc() != docId) {
+        return false;
+      }
+    }
+
+    // Prepare for payload extraction
+    tp.nextPosition();
+
+    this.payloadLength = tp.getPayloadLength();
+    if (this.payloadLength == 0) {
+      return false;
+    }
+
+    if (this.payloadLength > this.buffer.length) {
+      // Growing if necessary.
+      this.buffer = new byte[this.payloadLength * 2 + 1];
+    }
+    // Loading the payload
+    tp.getPayload(this.buffer, 0);
+
+    return true;
+  }
+
+  /**
+   * Get the buffer with the content of the last read payload.
+   */
+  public byte[] getBuffer() {
+    return buffer;
+  }
+
+  /**
+   * Get the length of the last read payload.
+   */
+  public int getPayloadLength() {
+    return payloadLength;
+  }
+
+}