ReverseOrdFieldSource.cs

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/* 
 * 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.
 */

using System;

using IndexReader = Lucene.Net.Index.IndexReader;
using FieldCache = Lucene.Net.Search.FieldCache;

namespace Lucene.Net.Search.Function
{
    
    /// <summary> Expert: obtains the ordinal of the field value from the default Lucene 
    /// <see cref="Lucene.Net.Search.FieldCache">FieldCache</see> using getStringIndex()
    /// and reverses the order.
    /// <p/>
    /// The native lucene index order is used to assign an ordinal value for each field value.
    /// <p/>
    /// Field values (terms) are lexicographically ordered by unicode value, and numbered starting at 1.
    /// <br/>
    /// Example of reverse ordinal (rord):
    /// <br/>If there were only three field values: "apple","banana","pear"
    /// <br/>then rord("apple")=3, rord("banana")=2, ord("pear")=1
    /// <p/>
    /// WARNING: 
    /// rord() depends on the position in an index and can thus change 
    /// when other documents are inserted or deleted,
    /// or if a MultiSearcher is used. 
    /// 
    /// <p/><font color="#FF0000">
    /// WARNING: The status of the <b>Search.Function</b> package is experimental. 
    /// The APIs introduced here might change in the future and will not be 
    /// supported anymore in such a case.</font>
    /// 
    /// <p/><b>NOTE</b>: with the switch in 2.9 to segment-based
    /// searching, if <see cref="GetValues" /> is invoked with a
    /// composite (multi-segment) reader, this can easily cause
    /// double RAM usage for the values in the FieldCache.  It's
    /// best to switch your application to pass only atomic
    /// (single segment) readers to this API.<p/>
    /// </summary>
    
    [Serializable]
    public class ReverseOrdFieldSource:ValueSource
    {
        private class AnonymousClassDocValues:DocValues
        {
            public AnonymousClassDocValues(int end, int[] arr, ReverseOrdFieldSource enclosingInstance)
            {
                InitBlock(end, arr, enclosingInstance);
            }
            private void  InitBlock(int end, int[] arr, ReverseOrdFieldSource enclosingInstance)
            {
                this.end = end;
                this.arr = arr;
                this.enclosingInstance = enclosingInstance;
            }
            private int end;
            private int[] arr;
            private ReverseOrdFieldSource enclosingInstance;
            public ReverseOrdFieldSource Enclosing_Instance
            {
                get
                {
                    return enclosingInstance;
                }
                
            }
            /*(non-Javadoc) <see cref="Lucene.Net.Search.Function.DocValues.floatVal(int) */
            public override float FloatVal(int doc)
            {
                return (float) (end - arr[doc]);
            }
            /* (non-Javadoc) <see cref="Lucene.Net.Search.Function.DocValues.intVal(int) */
            public override int IntVal(int doc)
            {
                return end - arr[doc];
            }
            /* (non-Javadoc) <see cref="Lucene.Net.Search.Function.DocValues.strVal(int) */
            public override System.String StrVal(int doc)
            {
                // the string value of the ordinal, not the string itself
                return System.Convert.ToString(IntVal(doc));
            }
            /*(non-Javadoc) <see cref="Lucene.Net.Search.Function.DocValues.toString(int) */
            public override System.String ToString(int doc)
            {
                return Enclosing_Instance.Description() + '=' + StrVal(doc);
            }
            /*(non-Javadoc) <see cref="Lucene.Net.Search.Function.DocValues.getInnerArray() */

            protected internal override object InnerArray
            {
                get { return arr; }
            }
        }
        public System.String field;
        
        /// <summary> Contructor for a certain field.</summary>
        /// <param name="field">field whose values reverse order is used.  
        /// </param>
        public ReverseOrdFieldSource(System.String field)
        {
            this.field = field;
        }
        
        /*(non-Javadoc) <see cref="Lucene.Net.Search.Function.ValueSource.description() */
        public override System.String Description()
        {
            return "rord(" + field + ')';
        }
        
        /*(non-Javadoc) <see cref="Lucene.Net.Search.Function.ValueSource.getValues(Lucene.Net.Index.IndexReader) */
        public override DocValues GetValues(IndexReader reader)
        {
            Lucene.Net.Search.StringIndex sindex = Lucene.Net.Search.FieldCache_Fields.DEFAULT.GetStringIndex(reader, field);
            
            int[] arr = sindex.order;
            int end = sindex.lookup.Length;
            
            return new AnonymousClassDocValues(end, arr, this);
        }
        
        /*(non-Javadoc) <see cref="java.lang.Object.equals(java.lang.Object) */
        public  override bool Equals(System.Object o)
        {
            if (o.GetType() != typeof(ReverseOrdFieldSource))
                return false;
            ReverseOrdFieldSource other = (ReverseOrdFieldSource) o;
            return this.field.Equals(other.field);
        }
        
        private static readonly int hcode;
        
        /*(non-Javadoc) <see cref="java.lang.Object.hashCode() */
        public override int GetHashCode()
        {
            return hcode + field.GetHashCode();
        }
        static ReverseOrdFieldSource()
        {
            hcode = typeof(ReverseOrdFieldSource).GetHashCode();
        }
    }
}