1 package org.apache.lucene.util.encoding;
3 import java.io.IOException;
4 import java.io.OutputStream;
7 * Licensed to the Apache Software Foundation (ASF) under one or more
8 * contributor license agreements. See the NOTICE file distributed with
9 * this work for additional information regarding copyright ownership.
10 * The ASF licenses this file to You under the Apache License, Version 2.0
11 * (the "License"); you may not use this file except in compliance with
12 * the License. You may obtain a copy of the License at
14 * http://www.apache.org/licenses/LICENSE-2.0
16 * Unless required by applicable law or agreed to in writing, software
17 * distributed under the License is distributed on an "AS IS" BASIS,
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19 * See the License for the specific language governing permissions and
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24 * Encodes integers to a set {@link OutputStream}. Extending classes need to
25 * override {@link #encode(int)} to encode the value using their encoding
26 * algorithm. The default implementation of {@link #close()} closes the set
27 * {@link OutputStream}.
29 * The default {@link #IntEncoder() constructor} is provided for convenience
30 * only. One must call {@link #reInit(OutputStream)} before calling
31 * {@link #encode(int)} or {@link #close()}.
33 * For convenience, each encoder implements {@link #createMatchingDecoder()} for
34 * easy access to the matching decoder.
36 * <b>NOTE:</b> some implementations may buffer the encoded values in memory
37 * (such as {@link IntEncoderFilter} implementations) and encoding will happen
38 * only upon calling {@link #close()}. Therefore it is important to always call
39 * {@link #close()} on the encoder at hand.
41 * <b>NOTE:</b> encoders are usually not thread safe, unless specifically
42 * documented otherwise by an implementation.
44 * @lucene.experimental
46 public abstract class IntEncoder {
48 protected OutputStream out = null;
51 * Default constructor, provided here for robustness: if in the future a
52 * constructor with parameters will be added, this might break custom
53 * implementations of this class which call this implicit constructor. So we
54 * make it explicit to avoid any such issue in the future.
60 * Instructs the encoder to finish the encoding process. This method closes
61 * the output stream which was specified by {@link #reInit(OutputStream)
62 * reInit}. An implementation may do here additional cleanup required to
63 * complete the encoding, such as flushing internal buffers, etc.<br>
64 * Once this method was called, no further calls to {@link #encode(int)
65 * encode} should be made before first calling {@link #reInit(OutputStream)
68 * <b>NOTE:</b> overriding classes should make sure they either call
69 * <code>super.close()</code> or close the output stream themselves.
71 public void close() throws IOException {
78 * Encodes an integer to the output stream given in
79 * {@link #reInit(OutputStream) reInit}
81 public abstract void encode(int value) throws IOException;
84 * Returns an {@link IntDecoder} which matches this encoder. Every encoder
85 * must return an {@link IntDecoder} and <code>null</code> is not a valid
86 * value. If an encoder is just a filter, it should at least return its
87 * wrapped encoder's matching decoder.
89 * <b>NOTE:</b> this method should create a new instance of the matching
90 * decoder and leave the instance sharing to the caller. Returning the same
91 * instance over and over is risky because encoders and decoders are not
94 public abstract IntDecoder createMatchingDecoder();
97 * Reinitializes the encoder with the give {@link OutputStream}. For
98 * re-usability it can be changed without the need to reconstruct a new
101 * <b>NOTE:</b> after calling {@link #close()}, one <u><i>must</i></u> call
102 * this method even if the output stream itself hasn't changed. An example
103 * case is that the output stream wraps a byte[], and the output stream itself
104 * is reset, but its instance hasn't changed. Some implementations of
105 * {@link IntEncoder} may write some metadata about themselves to the output
106 * stream, and therefore it is imperative that one calls this method before
109 public void reInit(OutputStream out) {