pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / search / MultiCollector.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/MultiCollector.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/MultiCollector.java
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+package org.apache.lucene.search;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.search.Collector;
+import org.apache.lucene.search.Scorer;
+
+/**
+ * A {@link Collector} which allows running a search with several
+ * {@link Collector}s. It offers a static {@link #wrap} method which accepts a
+ * list of collectors and wraps them with {@link MultiCollector}, while
+ * filtering out the <code>null</code> null ones.
+ */
+public class MultiCollector extends Collector {
+
+  /**
+   * Wraps a list of {@link Collector}s with a {@link MultiCollector}. This
+   * method works as follows:
+   * <ul>
+   * <li>Filters out the <code>null</code> collectors, so they are not used
+   * during search time.
+   * <li>If the input contains 1 real collector (i.e. non-<code>null</code> ),
+   * it is returned.
+   * <li>Otherwise the method returns a {@link MultiCollector} which wraps the
+   * non-<code>null</code> ones.
+   * </ul>
+   * 
+   * @throws IllegalArgumentException
+   *           if either 0 collectors were input, or all collectors are
+   *           <code>null</code>.
+   */
+  public static Collector wrap(Collector... collectors) {
+    // For the user's convenience, we allow null collectors to be passed.
+    // However, to improve performance, these null collectors are found
+    // and dropped from the array we save for actual collection time.
+    int n = 0;
+    for (Collector c : collectors) {
+      if (c != null) {
+        n++;
+      }
+    }
+
+    if (n == 0) {
+      throw new IllegalArgumentException("At least 1 collector must not be null");
+    } else if (n == 1) {
+      // only 1 Collector - return it.
+      Collector col = null;
+      for (Collector c : collectors) {
+        if (c != null) {
+          col = c;
+          break;
+        }
+      }
+      return col;
+    } else if (n == collectors.length) {
+      return new MultiCollector(collectors);
+    } else {
+      Collector[] colls = new Collector[n];
+      n = 0;
+      for (Collector c : collectors) {
+        if (c != null) {
+          colls[n++] = c;
+        }
+      }
+      return new MultiCollector(colls);
+    }
+  }
+  
+  private final Collector[] collectors;
+
+  private MultiCollector(Collector... collectors) {
+    this.collectors = collectors;
+  }
+
+  @Override
+  public boolean acceptsDocsOutOfOrder() {
+    for (Collector c : collectors) {
+      if (!c.acceptsDocsOutOfOrder()) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  @Override
+  public void collect(int doc) throws IOException {
+    for (Collector c : collectors) {
+      c.collect(doc);
+    }
+  }
+
+  @Override
+  public void setNextReader(IndexReader reader, int o) throws IOException {
+    for (Collector c : collectors) {
+      c.setNextReader(reader, o);
+    }
+  }
+
+  @Override
+  public void setScorer(Scorer s) throws IOException {
+    for (Collector c : collectors) {
+      c.setScorer(s);
+    }
+  }
+
+}