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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 Lucene.Net.Analysis.Tokenattributes;
using AttributeSource = Lucene.Net.Util.AttributeSource;
namespace Lucene.Net.Analysis
{
/// <summary>An abstract base class for simple, character-oriented tokenizers.</summary>
public abstract class CharTokenizer:Tokenizer
{
protected CharTokenizer(System.IO.TextReader input):base(input)
{
offsetAtt = AddAttribute<IOffsetAttribute>();
termAtt = AddAttribute<ITermAttribute>();
}
protected CharTokenizer(AttributeSource source, System.IO.TextReader input):base(source, input)
{
offsetAtt = AddAttribute<IOffsetAttribute>();
termAtt = AddAttribute<ITermAttribute>();
}
protected CharTokenizer(AttributeFactory factory, System.IO.TextReader input):base(factory, input)
{
offsetAtt = AddAttribute<IOffsetAttribute>();
termAtt = AddAttribute<ITermAttribute>();
}
private int offset = 0, bufferIndex = 0, dataLen = 0;
private const int MAX_WORD_LEN = 255;
private const int IO_BUFFER_SIZE = 4096;
private readonly char[] ioBuffer = new char[IO_BUFFER_SIZE];
private readonly ITermAttribute termAtt;
private readonly IOffsetAttribute offsetAtt;
/// <summary>Returns true iff a character should be included in a token. This
/// tokenizer generates as tokens adjacent sequences of characters which
/// satisfy this predicate. Characters for which this is false are used to
/// define token boundaries and are not included in tokens.
/// </summary>
protected internal abstract bool IsTokenChar(char c);
/// <summary>Called on each token character to normalize it before it is added to the
/// token. The default implementation does nothing. Subclasses may use this
/// to, e.g., lowercase tokens.
/// </summary>
protected internal virtual char Normalize(char c)
{
return c;
}
public override bool IncrementToken()
{
ClearAttributes();
int length = 0;
int start = bufferIndex;
char[] buffer = termAtt.TermBuffer();
while (true)
{
if (bufferIndex >= dataLen)
{
offset += dataLen;
dataLen = input.Read(ioBuffer, 0, ioBuffer.Length);
if (dataLen <= 0)
{
dataLen = 0; // so next offset += dataLen won't decrement offset
if (length > 0)
break;
return false;
}
bufferIndex = 0;
}
char c = ioBuffer[bufferIndex++];
if (IsTokenChar(c))
{
// if it's a token char
if (length == 0)
// start of token
start = offset + bufferIndex - 1;
else if (length == buffer.Length)
buffer = termAtt.ResizeTermBuffer(1 + length);
buffer[length++] = Normalize(c); // buffer it, normalized
if (length == MAX_WORD_LEN)
// buffer overflow!
break;
}
else if (length > 0)
// at non-Letter w/ chars
break; // return 'em
}
termAtt.SetTermLength(length);
offsetAtt.SetOffset(CorrectOffset(start), CorrectOffset(start + length));
return true;
}
public override void End()
{
// set final offset
int finalOffset = CorrectOffset(offset);
offsetAtt.SetOffset(finalOffset, finalOffset);
}
public override void Reset(System.IO.TextReader input)
{
base.Reset(input);
bufferIndex = 0;
offset = 0;
dataLen = 0;
}
}
}
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