TermAttribute.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 Lucene.Net.Support;
using ArrayUtil = Lucene.Net.Util.ArrayUtil;
using Attribute = Lucene.Net.Util.Attribute;

namespace Lucene.Net.Analysis.Tokenattributes
{
    
    /// <summary> The term text of a Token.</summary>
    [Serializable]
    public class TermAttribute:Attribute, ITermAttribute, System.ICloneable
    {
        private static int MIN_BUFFER_SIZE = 10;
        
        private char[] termBuffer;
        private int termLength;

        /// <summary>Returns the Token's term text.
        /// 
        /// This method has a performance penalty
        /// because the text is stored internally in a char[].  If
        /// possible, use <see cref="TermBuffer()" /> and 
        /// <see cref="TermLength()" /> directly instead.  If you 
        /// really need a String, use this method, which is nothing more than
        /// a convenience call to <b>new String(token.termBuffer(), 0, token.termLength())</b>
        /// </summary>
        public virtual string Term
        {
            get
            {
                InitTermBuffer();
                return new System.String(termBuffer, 0, termLength);
            }
        }

        /// <summary>Copies the contents of buffer, starting at offset for
        /// length characters, into the termBuffer array.
        /// </summary>
        /// <param name="buffer">the buffer to copy
        /// </param>
        /// <param name="offset">the index in the buffer of the first character to copy
        /// </param>
        /// <param name="length">the number of characters to copy
        /// </param>
        public virtual void  SetTermBuffer(char[] buffer, int offset, int length)
        {
            GrowTermBuffer(length);
            Array.Copy(buffer, offset, termBuffer, 0, length);
            termLength = length;
        }
        
        /// <summary>Copies the contents of buffer into the termBuffer array.</summary>
        /// <param name="buffer">the buffer to copy
        /// </param>
        public virtual void  SetTermBuffer(System.String buffer)
        {
            int length = buffer.Length;
            GrowTermBuffer(length);
            TextSupport.GetCharsFromString(buffer, 0, length, termBuffer, 0);
            termLength = length;
        }
        
        /// <summary>Copies the contents of buffer, starting at offset and continuing
        /// for length characters, into the termBuffer array.
        /// </summary>
        /// <param name="buffer">the buffer to copy
        /// </param>
        /// <param name="offset">the index in the buffer of the first character to copy
        /// </param>
        /// <param name="length">the number of characters to copy
        /// </param>
        public virtual void  SetTermBuffer(System.String buffer, int offset, int length)
        {
            System.Diagnostics.Debug.Assert(offset <= buffer.Length);
            System.Diagnostics.Debug.Assert(offset + length <= buffer.Length);
            GrowTermBuffer(length);
            TextSupport.GetCharsFromString(buffer, offset, offset + length, termBuffer, 0);
            termLength = length;
        }
        
        /// <summary>Returns the internal termBuffer character array which
        /// you can then directly alter.  If the array is too
        /// small for your token, use <see cref="ResizeTermBuffer(int)" />
        /// to increase it.  After
        /// altering the buffer be sure to call <see cref="SetTermLength" />
        /// to record the number of valid
        /// characters that were placed into the termBuffer. 
        /// </summary>
        public virtual char[] TermBuffer()
        {
            InitTermBuffer();
            return termBuffer;
        }
        
        /// <summary>Grows the termBuffer to at least size newSize, preserving the
        /// existing content. Note: If the next operation is to change
        /// the contents of the term buffer use
        /// <see cref="SetTermBuffer(char[], int, int)" />,
        /// <see cref="SetTermBuffer(String)" />, or
        /// <see cref="SetTermBuffer(String, int, int)" />
        /// to optimally combine the resize with the setting of the termBuffer.
        /// </summary>
        /// <param name="newSize">minimum size of the new termBuffer
        /// </param>
        /// <returns> newly created termBuffer with length >= newSize
        /// </returns>
        public virtual char[] ResizeTermBuffer(int newSize)
        {
            if (termBuffer == null)
            {
                // The buffer is always at least MIN_BUFFER_SIZE
                termBuffer = new char[ArrayUtil.GetNextSize(newSize < MIN_BUFFER_SIZE?MIN_BUFFER_SIZE:newSize)];
            }
            else
            {
                if (termBuffer.Length < newSize)
                {
                    // Not big enough; create a new array with slight
                    // over allocation and preserve content
                    char[] newCharBuffer = new char[ArrayUtil.GetNextSize(newSize)];
                    Array.Copy(termBuffer, 0, newCharBuffer, 0, termBuffer.Length);
                    termBuffer = newCharBuffer;
                }
            }
            return termBuffer;
        }
        
        
        /// <summary>Allocates a buffer char[] of at least newSize, without preserving the existing content.
        /// its always used in places that set the content 
        /// </summary>
        /// <param name="newSize">minimum size of the buffer
        /// </param>
        private void  GrowTermBuffer(int newSize)
        {
            if (termBuffer == null)
            {
                // The buffer is always at least MIN_BUFFER_SIZE
                termBuffer = new char[ArrayUtil.GetNextSize(newSize < MIN_BUFFER_SIZE?MIN_BUFFER_SIZE:newSize)];
            }
            else
            {
                if (termBuffer.Length < newSize)
                {
                    // Not big enough; create a new array with slight
                    // over allocation:
                    termBuffer = new char[ArrayUtil.GetNextSize(newSize)];
                }
            }
        }
        
        private void  InitTermBuffer()
        {
            if (termBuffer == null)
            {
                termBuffer = new char[ArrayUtil.GetNextSize(MIN_BUFFER_SIZE)];
                termLength = 0;
            }
        }
        
        /// <summary>Return number of valid characters (length of the term)
        /// in the termBuffer array. 
        /// </summary>
        public virtual int TermLength()
        {
            return termLength;
        }
        
        /// <summary>Set number of valid characters (length of the term) in
        /// the termBuffer array. Use this to truncate the termBuffer
        /// or to synchronize with external manipulation of the termBuffer.
        /// Note: to grow the size of the array,
        /// use <see cref="ResizeTermBuffer(int)" /> first.
        /// </summary>
        /// <param name="length">the truncated length
        /// </param>
        public virtual void  SetTermLength(int length)
        {
            InitTermBuffer();
            if (length > termBuffer.Length)
                throw new System.ArgumentException("length " + length + " exceeds the size of the termBuffer (" + termBuffer.Length + ")");
            termLength = length;
        }
        
        public override int GetHashCode()
        {
            InitTermBuffer();
            int code = termLength;
            code = code * 31 + ArrayUtil.HashCode(termBuffer, 0, termLength);
            return code;
        }
        
        public override void  Clear()
        {
            termLength = 0;
        }
        
        public override System.Object Clone()
        {
            TermAttribute t = (TermAttribute) base.Clone();
            // Do a deep clone
            if (termBuffer != null)
            {
                t.termBuffer = new char[termBuffer.Length];
                termBuffer.CopyTo(t.termBuffer, 0);
            }
            return t;
        }
        
        public  override bool Equals(System.Object other)
        {
            if (other == this)
            {
                return true;
            }
            
            if (other is ITermAttribute)
            {
                InitTermBuffer();
                TermAttribute o = ((TermAttribute) other);
                o.InitTermBuffer();
                
                if (termLength != o.termLength)
                    return false;
                for (int i = 0; i < termLength; i++)
                {
                    if (termBuffer[i] != o.termBuffer[i])
                    {
                        return false;
                    }
                }
                return true;
            }
            
            return false;
        }
        
        public override System.String ToString()
        {
            InitTermBuffer();
            return "term=" + new System.String(termBuffer, 0, termLength);
        }
        
        public override void  CopyTo(Attribute target)
        {
            InitTermBuffer();
            ITermAttribute t = (ITermAttribute) target;
            t.SetTermBuffer(termBuffer, 0, termLength);
        }
    }
}