de.susebox.jtopas.spi

Interface SequenceHandler

All Known Subinterfaces:

DataMapper

All Known Implementing Classes:

NoCaseSequenceStore, SequenceStore, StandardSequenceHandler, StandardTokenizerProperties

public interface SequenceHandler

This interface must be implemented by classes that should be used as a special sequence, string and comment start sequence checker for Tokenizer implementations.

Author:

Heiko Blau

See Also:

Tokenizer, TokenizerProperties, DataMapper

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.

Method Detail

hasSequenceCommentOrString

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.

Returns:

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

startsWithSequenceCommentOrString

TokenizerProperty startsWithSequenceCommentOrString(DataProvider dataProvider)
                                             throws TokenizerException,
                                                    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.
In cases of strings or comments, the return value contains the description for the introducing character sequence, NOT the whole string or comment. The reading of the rest of the string or comment is done by the calling Tokenizer.

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:

TokenizerException - generic exception

java.lang.NullPointerException - if no DataProvider is given

getSequenceMaxLength

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.

Returns:

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