pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/NOnesIntEncoder.java b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/NOnesIntEncoder.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.
+ */
+
+/**
+ * A variation of {@link FourFlagsIntEncoder} which translates the data as
+ * follows:
+ * <ul>
+ * <li>Values &ge; 2 are trnalsated to <code>value+1</code> (2 &rArr; 3, 3
+ * &rArr; 4 and so forth).
+ * <li>Any <code>N</code> occurrences of 1 are encoded as a single 2.
+ * <li>Otherwise, each 1 is encoded as 1.
+ * </ul>
+ * <p>
+ * Encoding examples:
+ * <ul>
+ * <li>N = 4: the data 1,1,1,1,1 is translated to: 2, 1
+ * <li>N = 3: the data 1,2,3,4,1,1,1,1,5 is translated to 1,3,4,5,2,1,6
+ * </ul>
+ * <b>NOTE:</b> this encoder does not support values &le; 0 and
+ * {@link Integer#MAX_VALUE}. 0 is not supported because it's not supported by
+ * {@link FourFlagsIntEncoder} and {@link Integer#MAX_VALUE} because this
+ * encoder translates N to N+1, which will cause an overflow and
+ * {@link Integer#MAX_VALUE} will become a negative number, which is not
+ * supported as well.<br>
+ * This does not mean you cannot encode {@link Integer#MAX_VALUE}. If it is not
+ * the first value to encode, and you wrap this encoder with
+ * {@link DGapIntEncoder}, then the value that will be sent to this encoder will
+ * be <code>MAX_VAL - prev</code>.
+ * 
+ * @lucene.experimental
+ */
+public class NOnesIntEncoder extends FourFlagsIntEncoder {
+
+  /** Number of consecutive '1's to be translated into single target value '2'. */
+  private int n;
+
+  /** Counts the number of consecutive ones seen. */
+  private int onesCounter = 0;
+
+  /**
+   * Constructs an encoder with a given value of N (N: Number of consecutive
+   * '1's to be translated into single target value '2').
+   */
+  public NOnesIntEncoder(int n) {
+    this.n = n;
+  }
+
+  @Override
+  public void close() throws IOException {
+    // We might have ones in our buffer, encode them as neccesary.
+    while (onesCounter-- > 0) {
+      super.encode(1);
+    }
+
+    super.close();
+  }
+
+  @Override
+  public void encode(int value) throws IOException {
+    if (value == 1) {
+      // Increment the number of consecutive ones seen so far
+      if (++onesCounter == n) {
+        super.encode(2);
+        onesCounter = 0;
+      }
+      return;
+    }
+
+    // If it's not one - there might have been ones we had to encode prior to
+    // this value
+    while (onesCounter > 0) {
+      --onesCounter;
+      super.encode(1);
+    }
+
+    // encode value + 1 --> the translation.
+    super.encode(value + 1);
+  }
+
+  @Override
+  public IntDecoder createMatchingDecoder() {
+    return new NOnesIntDecoder(n);
+  }
+
+  @Override
+  public void reInit(OutputStream out) {
+    super.reInit(out);
+    onesCounter = 0;
+  }
+
+  @Override
+  public String toString() {
+    return "NOnes (" + n + ") (" + super.toString() + ")";
+  }
+
+}