pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / util / ReaderUtil.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/util/ReaderUtil.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/util/ReaderUtil.java
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+package org.apache.lucene.util;
+
+/**
+ * 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 java.util.ArrayList;
+import java.util.List;
+
+import org.apache.lucene.index.IndexReader;
+
+/**
+ * Common util methods for dealing with {@link IndexReader}s.
+ *
+ * @lucene.internal
+ */
+public final class ReaderUtil {
+
+  private ReaderUtil() {} // no instance
+
+  /**
+   * Gathers sub-readers from reader into a List.
+   * 
+   * @param allSubReaders
+   * @param reader
+   */
+  public static void gatherSubReaders(List<IndexReader> allSubReaders, IndexReader reader) {
+    IndexReader[] subReaders = reader.getSequentialSubReaders();
+    if (subReaders == null) {
+      // Add the reader itself, and do not recurse
+      allSubReaders.add(reader);
+    } else {
+      for (int i = 0; i < subReaders.length; i++) {
+        gatherSubReaders(allSubReaders, subReaders[i]);
+      }
+    }
+  }
+
+  /** Recursively visits all sub-readers of a reader.  You
+   *  should subclass this and override the add method to
+   *  gather what you need.
+   *
+   * @lucene.experimental */
+  public static abstract class Gather {
+    private final IndexReader topReader;
+
+    public Gather(IndexReader r) {
+      topReader = r;
+    }
+
+    public int run() throws IOException {
+      return run(0, topReader);
+    }
+
+    public int run(int docBase) throws IOException {
+      return run(docBase, topReader);
+    }
+
+    private int run(int base, IndexReader reader) throws IOException {
+      IndexReader[] subReaders = reader.getSequentialSubReaders();
+      if (subReaders == null) {
+        // atomic reader
+        add(base, reader);
+        base += reader.maxDoc();
+      } else {
+        // composite reader
+        for (int i = 0; i < subReaders.length; i++) {
+          base = run(base, subReaders[i]);
+        }
+      }
+
+      return base;
+    }
+
+    protected abstract void add(int base, IndexReader r) throws IOException;
+  }
+
+  /**
+   * Returns sub IndexReader that contains the given document id.
+   *    
+   * @param doc id of document
+   * @param reader parent reader
+   * @return sub reader of parent which contains the specified doc id
+   */
+  public static IndexReader subReader(int doc, IndexReader reader) {
+    List<IndexReader> subReadersList = new ArrayList<IndexReader>();
+    ReaderUtil.gatherSubReaders(subReadersList, reader);
+    IndexReader[] subReaders = subReadersList
+        .toArray(new IndexReader[subReadersList.size()]);
+    int[] docStarts = new int[subReaders.length];
+    int maxDoc = 0;
+    for (int i = 0; i < subReaders.length; i++) {
+      docStarts[i] = maxDoc;
+      maxDoc += subReaders[i].maxDoc();
+    }
+    return subReaders[ReaderUtil.subIndex(doc, docStarts)];
+  }
+  
+  /**
+   * Returns sub-reader subIndex from reader.
+   * 
+   * @param reader parent reader
+   * @param subIndex index of desired sub reader
+   * @return the subreader at subIndex
+   */
+  public static IndexReader subReader(IndexReader reader, int subIndex) {
+    List<IndexReader> subReadersList = new ArrayList<IndexReader>();
+    ReaderUtil.gatherSubReaders(subReadersList, reader);
+    IndexReader[] subReaders = subReadersList
+        .toArray(new IndexReader[subReadersList.size()]);
+    return subReaders[subIndex];
+  }
+
+
+  /**
+   * Returns index of the searcher/reader for document <code>n</code> in the
+   * array used to construct this searcher/reader.
+   */
+  public static int subIndex(int n, int[] docStarts) { // find
+    // searcher/reader for doc n:
+    int size = docStarts.length;
+    int lo = 0; // search starts array
+    int hi = size - 1; // for first element less than n, return its index
+    while (hi >= lo) {
+      int mid = (lo + hi) >>> 1;
+      int midValue = docStarts[mid];
+      if (n < midValue)
+        hi = mid - 1;
+      else if (n > midValue)
+        lo = mid + 1;
+      else { // found a match
+        while (mid + 1 < size && docStarts[mid + 1] == midValue) {
+          mid++; // scan to last match
+        }
+        return mid;
+      }
+    }
+    return hi;
+  }
+}