TermPositions.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;

namespace Lucene.Net.Index
{
    
    /// <summary> TermPositions provides an interface for enumerating the &lt;document,
    /// frequency, &lt;position&gt;* &gt; tuples for a term.  <p/> The document and
    /// frequency are the same as for a TermDocs.  The positions portion lists the ordinal
    /// positions of each occurrence of a term in a document.
    /// 
    /// </summary>
    /// <seealso cref="IndexReader.TermPositions()">
    /// </seealso>
    
    public interface TermPositions : TermDocs
    {
        /// <summary>Returns next position in the current document.  It is an error to call
        /// this more than <see cref="TermDocs.Freq()" /> times
        /// without calling <see cref="TermDocs.Next()" /><p/> This is
        /// invalid until <see cref="TermDocs.Next()" /> is called for
        /// the first time.
        /// </summary>
        int NextPosition();

        /// <summary> Returns the length of the payload at the current term position.
        /// This is invalid until <see cref="NextPosition()" /> is called for
        /// the first time.<br/>
        /// </summary>
        /// <value> length of the current payload in number of bytes </value>
        int PayloadLength { get; }

        /// <summary> Returns the payload data at the current term position.
        /// This is invalid until <see cref="NextPosition()" /> is called for
        /// the first time.
        /// This method must not be called more than once after each call
        /// of <see cref="NextPosition()" />. However, payloads are loaded lazily,
        /// so if the payload data for the current position is not needed,
        /// this method may not be called at all for performance reasons.<br/>
        /// 
        /// </summary>
        /// <param name="data">the array into which the data of this payload is to be
        /// stored, if it is big enough; otherwise, a new byte[] array
        /// is allocated for this purpose. 
        /// </param>
        /// <param name="offset">the offset in the array into which the data of this payload
        /// is to be stored.
        /// </param>
        /// <returns> a byte[] array containing the data of this payload
        /// </returns>
        /// <throws>  IOException </throws>
        byte[] GetPayload(byte[] data, int offset);

        /// <summary> Checks if a payload can be loaded at this position.
        /// <p/>
        /// Payloads can only be loaded once per call to 
        /// <see cref="NextPosition()" />.
        /// 
        /// </summary>
        /// <value> true if there is a payload available at this position that can be loaded </value>
        bool IsPayloadAvailable { get; }
    }
}