| /* |
| * 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. |
| */ |
| package org.apache.lucene.index; |
| |
| |
| import java.util.List; |
| |
| /** |
| * A struct like class that represents a hierarchical relationship between |
| * {@link IndexReader} instances. |
| */ |
| public abstract class IndexReaderContext { |
| /** The reader context for this reader's immediate parent, or null if none */ |
| public final CompositeReaderContext parent; |
| /** <code>true</code> if this context struct represents the top level reader within the hierarchical context */ |
| public final boolean isTopLevel; |
| /** the doc base for this reader in the parent, <tt>0</tt> if parent is null */ |
| public final int docBaseInParent; |
| /** the ord for this reader in the parent, <tt>0</tt> if parent is null */ |
| public final int ordInParent; |
| |
| // An object that uniquely identifies this context without referencing |
| // segments. The goal is to make it fine to have references to this |
| // identity object, even after the index reader has been closed |
| final Object identity = new Object(); |
| |
| IndexReaderContext(CompositeReaderContext parent, int ordInParent, int docBaseInParent) { |
| if (!(this instanceof CompositeReaderContext || this instanceof LeafReaderContext)) |
| throw new Error("This class should never be extended by custom code!"); |
| this.parent = parent; |
| this.docBaseInParent = docBaseInParent; |
| this.ordInParent = ordInParent; |
| this.isTopLevel = parent==null; |
| } |
| |
| /** Expert: Return an {@link Object} that uniquely identifies this context. |
| * The returned object does neither reference this {@link IndexReaderContext} |
| * nor the wrapped {@link IndexReader}. |
| * @lucene.experimental */ |
| public Object id() { |
| return identity; |
| } |
| |
| /** Returns the {@link IndexReader}, this context represents. */ |
| public abstract IndexReader reader(); |
| |
| /** |
| * Returns the context's leaves if this context is a top-level context. |
| * For convenience, if this is an {@link LeafReaderContext} this |
| * returns itself as the only leaf. |
| * <p>Note: this is convenience method since leaves can always be obtained by |
| * walking the context tree using {@link #children()}. |
| * @throws UnsupportedOperationException if this is not a top-level context. |
| * @see #children() |
| */ |
| public abstract List<LeafReaderContext> leaves() throws UnsupportedOperationException; |
| |
| /** |
| * Returns the context's children iff this context is a composite context |
| * otherwise <code>null</code>. |
| */ |
| public abstract List<IndexReaderContext> children(); |
| } |