pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / facet / src / java / org / apache / lucene / util / encoding / UniqueValuesIntEncoder.java

diff --git a/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/UniqueValuesIntEncoder.java b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/UniqueValuesIntEncoder.java
new file mode 100644 (file)
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+++ b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/UniqueValuesIntEncoder.java
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+package org.apache.lucene.util.encoding;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * 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.
+ */
+
+/**
+ * An {@link IntEncoderFilter} which ensures only unique values are encoded. The
+ * implementation assumes the values given to {@link #encode(int)} are sorted.
+ * If this is not the case, you can chain this encoder with
+ * {@link SortingIntEncoder}.
+ * 
+ * @lucene.experimental
+ */
+public final class UniqueValuesIntEncoder extends IntEncoderFilter {
+
+  /**
+   * Denotes an illegal value which we can use to init 'prev' to. Since all
+   * encoded values are integers, this value is init to MAX_INT+1 and is of type
+   * long. Therefore we are guaranteed not to get this value in encode.
+   */
+  private static final long ILLEGAL_VALUE = Integer.MAX_VALUE + 1;
+
+  private long prev = ILLEGAL_VALUE;
+  
+  /** Constructs a new instance with the given encoder. */
+  public UniqueValuesIntEncoder(IntEncoder encoder) {
+    super(encoder);
+  }
+
+  @Override
+  public void encode(int value) throws IOException {
+    if (prev != value) {
+      encoder.encode(value);
+      prev = value;
+    }
+  }
+
+  @Override
+  public IntDecoder createMatchingDecoder() {
+    return encoder.createMatchingDecoder();
+  }
+  
+  @Override
+  public void reInit(OutputStream out) {
+    super.reInit(out);
+    prev = ILLEGAL_VALUE;
+  }
+
+  @Override
+  public String toString() {
+    return "Unique (" + encoder.toString() + ")";
+  }
+  
+}