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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.
*/
/**
* 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}.
*
* The default {@link #IntEncoder() constructor} is provided for convenience
* only. One must call {@link #reInit(OutputStream)} before calling
* {@link #encode(int)} or {@link #close()}.
*
* For convenience, each encoder implements {@link #createMatchingDecoder()} for
* easy access to the matching decoder.
*
* NOTE: 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.
*
* NOTE: 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.
* Once this method was called, no further calls to {@link #encode(int)
* encode} should be made before first calling {@link #reInit(OutputStream)
* reInit}.
*
* NOTE: overriding classes should make sure they either call
* super.close() 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 null is not a valid
* value. If an encoder is just a filter, it should at least return its
* wrapped encoder's matching decoder.
*
* NOTE: 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.
*
* NOTE: after calling {@link #close()}, one must 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;
}
}