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package org.apache.lucene.util;
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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import java.io.IOException;
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import org.apache.lucene.index.CorruptIndexException;
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import org.apache.lucene.index.IndexFormatTooNewException;
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import org.apache.lucene.index.IndexFormatTooOldException;
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import org.apache.lucene.store.DataInput;
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import org.apache.lucene.store.DataOutput;
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* @lucene.experimental
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public final class CodecUtil {
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private CodecUtil() {} // no instance
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private final static int CODEC_MAGIC = 0x3fd76c17;
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public static DataOutput writeHeader(DataOutput out, String codec, int version)
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BytesRef bytes = new BytesRef(codec);
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if (bytes.length != codec.length() || bytes.length >= 128) {
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throw new IllegalArgumentException("codec must be simple ASCII, less than 128 characters in length [got " + codec + "]");
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out.writeInt(CODEC_MAGIC);
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out.writeString(codec);
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out.writeInt(version);
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public static int headerLength(String codec) {
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return 9+codec.length();
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public static int checkHeader(DataInput in, String codec, int minVersion, int maxVersion)
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// Safety to guard against reading a bogus string:
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final int actualHeader = in.readInt();
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if (actualHeader != CODEC_MAGIC) {
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throw new CorruptIndexException("codec header mismatch: actual header=" + actualHeader + " vs expected header=" + CODEC_MAGIC + " (resource: " + in + ")");
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final String actualCodec = in.readString();
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if (!actualCodec.equals(codec)) {
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throw new CorruptIndexException("codec mismatch: actual codec=" + actualCodec + " vs expected codec=" + codec + " (resource: " + in + ")");
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final int actualVersion = in.readInt();
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if (actualVersion < minVersion) {
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throw new IndexFormatTooOldException(in, actualVersion, minVersion, maxVersion);
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if (actualVersion > maxVersion) {
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throw new IndexFormatTooNewException(in, actualVersion, minVersion, maxVersion);