pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/IntEncoder.java b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/IntEncoder.java
new file mode 100644 (file)
index 0000000..bef6a34
--- /dev/null
+++ b/lucene-java-3.5.0/lucene/contrib/facet/src/java/org/apache/lucene/util/encoding/IntEncoder.java
@@ -0,0 +1,113 @@
+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.
+ */
+
+/**
+ * Encodes integers to a set {@link OutputStream}. Extending classes need to
+ * override {@link #encode(int)} to encode the value using their encoding
+ * algorithm. The default implementation of {@link #close()} closes the set
+ * {@link OutputStream}.
+ * <p>
+ * The default {@link #IntEncoder() constructor} is provided for convenience
+ * only. One must call {@link #reInit(OutputStream)} before calling
+ * {@link #encode(int)} or {@link #close()}.
+ * <p>
+ * For convenience, each encoder implements {@link #createMatchingDecoder()} for
+ * easy access to the matching decoder.
+ * <p>
+ * <b>NOTE:</b> some implementations may buffer the encoded values in memory
+ * (such as {@link IntEncoderFilter} implementations) and encoding will happen
+ * only upon calling {@link #close()}. Therefore it is important to always call
+ * {@link #close()} on the encoder at hand.
+ * <p>
+ * <b>NOTE:</b> encoders are usually not thread safe, unless specifically
+ * documented otherwise by an implementation.
+ * 
+ * @lucene.experimental
+ */
+public abstract class IntEncoder {
+
+  protected OutputStream out = null;
+
+  /**
+   * Default constructor, provided here for robustness: if in the future a
+   * constructor with parameters will be added, this might break custom
+   * implementations of this class which call this implicit constructor. So we
+   * make it explicit to avoid any such issue in the future.
+   */
+  public IntEncoder() {
+  }
+
+  /**
+   * Instructs the encoder to finish the encoding process. This method closes
+   * the output stream which was specified by {@link #reInit(OutputStream)
+   * reInit}. An implementation may do here additional cleanup required to
+   * complete the encoding, such as flushing internal buffers, etc.<br>
+   * Once this method was called, no further calls to {@link #encode(int)
+   * encode} should be made before first calling {@link #reInit(OutputStream)
+   * reInit}.
+   * <p>
+   * <b>NOTE:</b> overriding classes should make sure they either call
+   * <code>super.close()</code> or close the output stream themselves.
+   */
+  public void close() throws IOException {
+    if (out != null) {
+      out.close();
+    }
+  }
+
+  /**
+   * Encodes an integer to the output stream given in
+   * {@link #reInit(OutputStream) reInit}
+   */
+  public abstract void encode(int value) throws IOException;
+
+  /**
+   * Returns an {@link IntDecoder} which matches this encoder. Every encoder
+   * must return an {@link IntDecoder} and <code>null</code> is not a valid
+   * value. If an encoder is just a filter, it should at least return its
+   * wrapped encoder's matching decoder.
+   * <p>
+   * <b>NOTE:</b> this method should create a new instance of the matching
+   * decoder and leave the instance sharing to the caller. Returning the same
+   * instance over and over is risky because encoders and decoders are not
+   * thread safe.
+   */
+  public abstract IntDecoder createMatchingDecoder();
+  
+  /**
+   * Reinitializes the encoder with the give {@link OutputStream}. For
+   * re-usability it can be changed without the need to reconstruct a new
+   * object.
+   * <p>
+   * <b>NOTE:</b> after calling {@link #close()}, one <u><i>must</i></u> call
+   * this method even if the output stream itself hasn't changed. An example
+   * case is that the output stream wraps a byte[], and the output stream itself
+   * is reset, but its instance hasn't changed. Some implementations of
+   * {@link IntEncoder} may write some metadata about themselves to the output
+   * stream, and therefore it is imperative that one calls this method before
+   * encoding any data.
+   */
+  public void reInit(OutputStream out) {
+    this.out = out;
+  }
+
+}