monq.jfa.actions

Class Hold

java.lang.Object

monq.jfa.AbstractFaAction

monq.jfa.actions.Hold

All Implemented Interfaces:

java.io.Serializable, FaAction

public class Hold
extends AbstractFaAction

hold back output until a decision can be made whether to ship or to drop filtered output. Associate this callback with a pattern that defines the start of a lengthy region of text only at the end of which a decision can be made whether to drop it or copy it to the output.

This callback sets DfaRun.collect to true and records the position. To store the position, the callback obtains a Map from a MapProvider that has to be in the DfaRun.clientData field of the calling DfaRun. The Hold object stores only one entry in the Map with itself as the key. Consequently you may use the Map in other callbacks to store information that may be necessary to make the later decision whether to ship or drop the text.

At the point where the decision can be made, use the callback generated by either drop() or ship() to delete or deliver the output held back so far. A typical use looks like:

   Hold hold = new Hold();
   ...
   nfa.or("start", hold)
      .or("goodEnd", hold.ship())
      .or("badEnd", hold.drop())
      // or in a different scenario with If
      .or("end", new If(v, hold.ship(), hold.drop()))

In the use with If, v would be a Verifier which performs whatever test is necessary to check whether the held back output shall be shipped or dropped.

Objects of this class can operate in nested contexts. Only the outermost Hold object will set DfaRun.collect back to false.

Author:

© 2003,2004 Harald Kirsch

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
Hold()

Method Summary

Modifier and Type	Method and Description
AbstractFaAction	drop() create an FaAction which drops (deletes) the output held back by this object.
int	getStart(DfaRun r) returns the position this object current refers to as the start position where data is being hold back.
void	invoke(java.lang.StringBuilder yytext, int start, DfaRun r) is called by methods of DfaRun in case of a match.
AbstractFaAction	ship() create an FaAction which ships (delivers) the output held back by this object.

Methods inherited from class monq.jfa.AbstractFaAction

mergeWith, setPriority

Methods inherited from class java.lang.Object

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

Constructor Detail

Hold

public Hold()

Method Detail

invoke

public void invoke(java.lang.StringBuilder yytext,
                   int start,
                   DfaRun r)

Description copied from interface: FaAction

is called by methods of DfaRun in case of a match. Parameter yytext contains the matching text from position start onwards. The callback may change the whole of yytext, but the under most circumstances, only the matching text should be changed. Parameter runner is the DfaRun object which called this function. Of interest are its fields DfaRun.clientData and DfaRun.collect.

getStart

public int getStart(DfaRun r)

returns the position this object current refers to as the start position where data is being hold back.

drop

public AbstractFaAction drop()

create an FaAction which drops (deletes) the output held back by this object. The action returned will throw an IllegalStateException when called while there is no data being held back.

ship

public AbstractFaAction ship()

create an FaAction which ships (delivers) the output held back by this object. The action returned will throw an IllegalStateException when called while there is no data being is held back.