pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / analysis / CachingTokenFilter.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/analysis/CachingTokenFilter.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/analysis/CachingTokenFilter.java
new file mode 100644 (file)
index 0000000..9885ace
--- /dev/null
+++ b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/analysis/CachingTokenFilter.java
@@ -0,0 +1,86 @@
+package org.apache.lucene.analysis;
+
+/**
+ * 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.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+
+import org.apache.lucene.util.AttributeSource;
+
+/**
+ * This class can be used if the token attributes of a TokenStream
+ * are intended to be consumed more than once. It caches
+ * all token attribute states locally in a List.
+ * 
+ * <P>CachingTokenFilter implements the optional method
+ * {@link TokenStream#reset()}, which repositions the
+ * stream to the first Token. 
+ */
+public final class CachingTokenFilter extends TokenFilter {
+  private List<AttributeSource.State> cache = null;
+  private Iterator<AttributeSource.State> iterator = null; 
+  private AttributeSource.State finalState;
+  
+  public CachingTokenFilter(TokenStream input) {
+    super(input);
+  }
+  
+  @Override
+  public final boolean incrementToken() throws IOException {
+    if (cache == null) {
+      // fill cache lazily
+      cache = new LinkedList<AttributeSource.State>();
+      fillCache();
+      iterator = cache.iterator();
+    }
+    
+    if (!iterator.hasNext()) {
+      // the cache is exhausted, return false
+      return false;
+    }
+    // Since the TokenFilter can be reset, the tokens need to be preserved as immutable.
+    restoreState(iterator.next());
+    return true;
+  }
+  
+  @Override
+  public final void end() throws IOException {
+    if (finalState != null) {
+      restoreState(finalState);
+    }
+  }
+
+  @Override
+  public void reset() throws IOException {
+    if(cache != null) {
+      iterator = cache.iterator();
+    }
+  }
+  
+  private void fillCache() throws IOException {
+    while(input.incrementToken()) {
+      cache.add(captureState());
+    }
+    // capture final state
+    input.end();
+    finalState = captureState();
+  }
+
+}