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/*
 * COPIED FROM APACHE LUCENE 4.7.2
 *
 * Git URL: [email protected]:apache/lucene.git, tag: releases/lucene-solr/4.7.2, path: lucene/core/src/java
 *
 * (see https://issues.apache.org/jira/browse/OAK-10786 for details)
 */

package org.apache.lucene.codecs.lucene40;

/*
 * 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.
 */

import java.io.IOException;

import org.apache.lucene.codecs.CodecUtil;
import org.apache.lucene.codecs.StoredFieldsFormat;
import org.apache.lucene.codecs.StoredFieldsReader;
import org.apache.lucene.codecs.StoredFieldsWriter;
import org.apache.lucene.index.FieldInfos;
import org.apache.lucene.index.SegmentInfo;
import org.apache.lucene.store.DataOutput; // javadocs
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.IOContext;

/** 
 * Lucene 4.0 Stored Fields Format.
 * Stored fields are represented by two files:
 * 
 * 
 * The field index, or .fdx file.
 * This is used to find the location within the field data file of the fields
 * of a particular document. Because it contains fixed-length data, this file may
 * be easily randomly accessed. The position of document n 's field data is
 * the {@link DataOutput#writeLong Uint64} at n*8 in this file.
 * This contains, for each document, a pointer to its field data, as
 * follows:
 * 
 * FieldIndex (.fdx) --> <Header>, <FieldValuesPosition> ^SegSize
 * Header --> {@link CodecUtil#writeHeader CodecHeader}
 * FieldValuesPosition --> {@link DataOutput#writeLong Uint64}
 * 
 * 
 * 
 * The field data, or .fdt file.
 * This contains the stored fields of each document, as follows:
 * 
 * FieldData (.fdt) --> <Header>, <DocFieldData> ^SegSize
 * Header --> {@link CodecUtil#writeHeader CodecHeader}
 * DocFieldData --> FieldCount, <FieldNum, Bits, Value>
 * ^FieldCount
 * FieldCount --> {@link DataOutput#writeVInt VInt}
 * FieldNum --> {@link DataOutput#writeVInt VInt}
 * Bits --> {@link DataOutput#writeByte Byte}
 * 
 * low order bit reserved.
 * second bit is one for fields containing binary data
 * third bit reserved.
 * 4th to 6th bit (mask: 0x7<<3) define the type of a numeric field:
 * 
 * all bits in mask are cleared if no numeric field at all
 * 1<<3: Value is Int
 * 2<<3: Value is Long
 * 3<<3: Value is Int as Float (as of {@link Float#intBitsToFloat(int)}
 * 4<<3: Value is Long as Double (as of {@link Double#longBitsToDouble(long)}
 * 
 * 
 * 
 * Value --> String | BinaryValue | Int | Long (depending on Bits)
 * BinaryValue --> ValueSize, <{@link DataOutput#writeByte Byte}>^ValueSize
 * ValueSize --> {@link DataOutput#writeVInt VInt}
 * 
 * 
 * 
 * @lucene.experimental */
public class Lucene40StoredFieldsFormat extends StoredFieldsFormat {

  /** Sole constructor. */
  public Lucene40StoredFieldsFormat() {
  }

  @Override
  public StoredFieldsReader fieldsReader(Directory directory, SegmentInfo si,
      FieldInfos fn, IOContext context) throws IOException {
    return new Lucene40StoredFieldsReader(directory, si, fn, context);
  }

  @Override
  public StoredFieldsWriter fieldsWriter(Directory directory, SegmentInfo si,
      IOContext context) throws IOException {
    return new Lucene40StoredFieldsWriter(directory, si.name, context);
  }
}