Class SegmentingTokenizerBase

Breaks text into sentences with a ICU4N.Text.BreakIterator and allows subclasses to decompose these sentences into words.

This can be used by subclasses that need sentence context for tokenization purposes, such as CJK segmenters.

Additionally it can be used by subclasses that want to mark sentence boundaries (with a custom attribute, extra token, position increment, etc) for downstream processing.

Note

This API is experimental and might change in incompatible ways in the next release.

Inheritance

object

AttributeSource

TokenStream

Tokenizer

SegmentingTokenizerBase

ThaiTokenizer

Implements

IDisposable

Inherited Members

Tokenizer.m_input

Tokenizer.Dispose(bool)

Tokenizer.CorrectOffset(int)

Tokenizer.SetReader(TextReader)

TokenStream.Dispose()

AttributeSource.GetAttributeFactory()

AttributeSource.GetAttributeClassesEnumerator()

AttributeSource.GetAttributeImplsEnumerator()

AttributeSource.AddAttributeImpl(Attribute)

AttributeSource.AddAttribute<T>()

AttributeSource.HasAttributes

AttributeSource.HasAttribute<T>()

AttributeSource.GetAttribute<T>()

AttributeSource.ClearAttributes()

AttributeSource.CaptureState()

AttributeSource.RestoreState(AttributeSource.State)

AttributeSource.GetHashCode()

AttributeSource.Equals(object)

AttributeSource.ReflectAsString(bool)

AttributeSource.ReflectWith(IAttributeReflector)

AttributeSource.CloneAttributes()

AttributeSource.CopyTo(AttributeSource)

AttributeSource.ToString()

object.Equals(object, object)

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: Lucene.Net.Analysis.Util

Assembly: Lucene.Net.ICU.dll

Syntax

public abstract class SegmentingTokenizerBase : Tokenizer, IDisposable

Constructors

SegmentingTokenizerBase(AttributeFactory, TextReader, BreakIterator)

Construct a new SegmenterBase, also supplying the Lucene.Net.Util.AttributeSource.AttributeFactory

Declaration

protected SegmentingTokenizerBase(AttributeSource.AttributeFactory factory, TextReader reader, BreakIterator iterator)

Parameters

Type	Name	Description
AttributeSource.AttributeFactory	factory
TextReader	reader
BreakIterator	iterator

SegmentingTokenizerBase(TextReader, BreakIterator)

Construct a new SegmenterBase, using the provided ICU4N.Text.BreakIterator for sentence segmentation.

Note that you should never share ICU4N.Text.BreakIterators across different Lucene.Net.Analysis.TokenStreams, instead a newly created or cloned one should always be provided to this constructor.

Declaration

protected SegmentingTokenizerBase(TextReader reader, BreakIterator iterator)

Parameters

Type	Name	Description
TextReader	reader
BreakIterator	iterator

Fields

BUFFERMAX

Breaks text into sentences with a ICU4N.Text.BreakIterator and allows subclasses to decompose these sentences into words.

This can be used by subclasses that need sentence context for tokenization purposes, such as CJK segmenters.

Additionally it can be used by subclasses that want to mark sentence boundaries (with a custom attribute, extra token, position increment, etc) for downstream processing.

Note

This API is experimental and might change in incompatible ways in the next release.

Declaration

protected const int BUFFERMAX = 1024

Field Value

Type	Description
int

m_buffer

Breaks text into sentences with a ICU4N.Text.BreakIterator and allows subclasses to decompose these sentences into words.

This can be used by subclasses that need sentence context for tokenization purposes, such as CJK segmenters.

Additionally it can be used by subclasses that want to mark sentence boundaries (with a custom attribute, extra token, position increment, etc) for downstream processing.

Note

This API is experimental and might change in incompatible ways in the next release.

Declaration

protected readonly char[] m_buffer

Field Value

Type	Description
char[]

m_offset

accumulated offset of previous buffers for this reader, for offsetAtt

Declaration

protected int m_offset

Field Value

Type	Description
int

Methods

End()

This method is called by the consumer after the last token has been consumed, after Lucene.Net.Analysis.TokenStream.IncrementToken() returned false (using the new Lucene.Net.Analysis.TokenStream API). Streams implementing the old API should upgrade to use this feature.

This method can be used to perform any end-of-stream operations, such as setting the final offset of a stream. The final offset of a stream might differ from the offset of the last token eg in case one or more whitespaces followed after the last token, but a WhitespaceTokenizer was used.

Additionally any skipped positions (such as those removed by a stopfilter) can be applied to the position increment, or any adjustment of other attributes where the end-of-stream value may be important.

If you override this method, always call base.End();.

Declaration

public override sealed void End()

Overrides

Lucene.Net.Analysis.TokenStream.End()

Exceptions

Type	Condition
IOException	If an I/O error occurs

IncrementToken()

Consumers (i.e., Lucene.Net.Index.IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate Lucene.Net.Util.IAttributes with the attributes of the next token.

The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use Lucene.Net.Util.AttributeSource.CaptureState() to create a copy of the current attribute state.

this method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to Lucene.Net.Util.AttributeSource.AddAttribute<T>() and Lucene.Net.Util.AttributeSource.GetAttribute<T>(), references to all Lucene.Net.Util.IAttributes that this stream uses should be retrieved during instantiation.

To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in Lucene.Net.Analysis.TokenStream.IncrementToken().

Declaration

public override sealed bool IncrementToken()

Returns

Type	Description
bool	false for end of stream; true otherwise

Overrides

Lucene.Net.Analysis.TokenStream.IncrementToken()

IncrementWord()

Returns true if another word is available

Declaration

protected abstract bool IncrementWord()

Returns

Type	Description
bool

IsSafeEnd(char)

For sentence tokenization, these are the unambiguous break positions.

Declaration

protected virtual bool IsSafeEnd(char ch)

Parameters

Type	Name	Description
char	ch

Returns

Type	Description
bool

Reset()

This method is called by a consumer before it begins consumption using Lucene.Net.Analysis.TokenStream.IncrementToken().

Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.

If you override this method, always call base.Reset(), otherwise some internal state will not be correctly reset (e.g., Lucene.Net.Analysis.Tokenizer will throw InvalidOperationException on further usage).

Declaration

public override void Reset()

Overrides

Lucene.Net.Analysis.Tokenizer.Reset()

SetNextSentence(int, int)

Provides the next input sentence for analysis

Declaration

protected abstract void SetNextSentence(int sentenceStart, int sentenceEnd)

Parameters

Type	Name	Description
int	sentenceStart
int	sentenceEnd

Implements

IDisposable