de.susebox.jtopas.spi

Class StandardSequenceHandler

java.lang.Object

de.susebox.jtopas.spi.StandardSequenceHandler

All Implemented Interfaces:

SequenceHandler

public class StandardSequenceHandler
extends java.lang.Object
implements SequenceHandler

Simple implementation of the SequenceHandler interface. This class works only with the TokenizerProperties interface methods and is aware of changes in these properties. It does not cache any information and is therefore a more or less slow way to handle special sequences.

This class is a bridge between arbitrary Tokenizer implementations using the SPI interface SequenceHandler and any TokenizerProperties implementation that does not implement the SequenceHandler interface itself.

Author:

Heiko Blau

See Also:

SequenceHandler, Tokenizer, TokenizerProperties

Constructor Summary

Constructors

Constructor and Description
StandardSequenceHandler(TokenizerProperties props) The constructor takes the TokenizerProperties that provide the special sequences.

Method Summary

Modifier and Type	Method and Description
int	getSequenceMaxLength() This method returns the length of the longest special sequence, comment or string prefix that is known to this SequenceHandler.
boolean	hasSequenceCommentOrString() This method can be used by a Tokenizer implementation for a fast detection if special sequence checking must be performed at all.
TokenizerProperty	startsWithSequenceCommentOrString(DataProvider dataProvider) This method checks if a given range of data starts with a special sequence, a comment or a string.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

StandardSequenceHandler

public StandardSequenceHandler(TokenizerProperties props)

The constructor takes the TokenizerProperties that provide the special sequences.

Parameters:

props - the TokenizerProperties to take the sequences from

Method Detail

hasSequenceCommentOrString

public boolean hasSequenceCommentOrString()

This method can be used by a Tokenizer implementation for a fast detection if special sequence checking must be performed at all. If the method returns false time-consuming preparations can be skipped.

Specified by:

hasSequenceCommentOrString in interface SequenceHandler

Returns:

true if there actually are pattern that can be tested for a match, false otherwise.

startsWithSequenceCommentOrString

public TokenizerProperty startsWithSequenceCommentOrString(DataProvider dataProvider)
                                                    throws java.lang.NullPointerException

This method checks if a given range of data starts with a special sequence, a comment or a string. These three types of token are tested together since both comment and string prefixes are ordinary special sequences. Only the actions preformed after a string or comment has been detected, are different.
The method returns null if no special sequence, comment or string could matches the the leading part of the data range given through the DataProvider.

Specified by:

startsWithSequenceCommentOrString in interface SequenceHandler

Parameters:

dataProvider - the source to get the data range from

Returns:

a TokenizerProperty if a special sequence, comment or string could be detected, null otherwise

Throws:

java.lang.NullPointerException - if no DataProvider is given

getSequenceMaxLength

public int getSequenceMaxLength()

This method returns the length of the longest special sequence, comment or string prefix that is known to this SequenceHandler. When calling startsWithSequenceCommentOrString(de.susebox.jtopas.spi.DataProvider), the passed DataProvider parameter will supply at least this number of characters (see DataProvider.getLength()). If less characters are provided, EOF is reached.
The method is an easy approach to the problem of how to provide more data in case a test runs out of characters. The invoking Tokenizer (represented by the given DataProvider) can supply enough data for the startsWithSequenceCommentOrString(de.susebox.jtopas.spi.DataProvider) method.

Specified by:

getSequenceMaxLength in interface SequenceHandler

Returns:

the number of characters needed in the worst case to identify a special sequence