org.treetank.service.xml.xpath.functions

Class AbsFunction

java.lang.Object

org.treetank.axis.AbsAxis

org.treetank.service.xml.xpath.expr.AbsExpression

org.treetank.service.xml.xpath.functions.AbsFunction

All Implemented Interfaces:

Iterable<Long>, Iterator<Long>

Direct Known Subclasses:

FNBoolean, FNCount, FNNot, FNPosition, FNString, FNSum

public abstract class AbsFunction
extends AbsExpression

AbstractFunction

Abstract super class for all function classes.

All functions that extend the abstract class only need take care of the result computation. Everything else, like checking if arguments are valid and adding the result with the corresponding type to the transaction list is done by the abstract super class.

Developer Example

   Must extend <code>AbstractFunction</code> and implement <code>IAxis</code>.
   And the implement the abstract method computeResult(), that returns the 
   computed value as a bye-array
   
   
   
   public class ExampleFunctionAxis extends AbstractFunction implements IAxis {
  
     public ExampleAxis(final INodeReadTrx rtx, final List<IAxis> args,
       final int min, final int max, final int returnType) {
       // Must be called as first.
       super(rtx, args, min, max, returnType);
     }
     protected byte[] computeResult() {
       .... compute value and return as byte array
     }
   
   }
 

Constructor Summary

Constructors

Constructor and Description
AbsFunction(INodeReadTrx rtx, List<AbsAxis> args, int min, int max, int returnType) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
protected abstract byte[]	computeResult() Computes the result value of the function.
AtomicValue	evaluate() Performs the expression dependent evaluation of the expression.
protected List<AbsAxis>	getArgs()
void	reset(long mNodeKey) Resetting the nodekey of this axis to a given nodekey.
void	varifyParam(int mNumber) Checks if the number of input arguments of this function is a valid according to the function specification in XQuery 1.0 and XPath 2.0 Functions and Operators.

Methods inherited from class org.treetank.service.xml.xpath.expr.AbsExpression

hasNext

Methods inherited from class org.treetank.axis.AbsAxis

addAtomicToItemList, close, getItemList, getNode, getStartKey, isSelfIncluded, iterator, moveTo, next, remove, resetToLastKey, resetToStartKey

Methods inherited from class java.lang.Object

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

Constructor Detail

AbsFunction

public AbsFunction(INodeReadTrx rtx,
           List<AbsAxis> args,
           int min,
           int max,
           int returnType)
            throws TTXPathException

Constructor. Initializes internal state and do a statical analysis concerning the function's arguments.

Parameters:

rtx - Transaction to operate on

args - List of function arguments

min - min number of allowed function arguments

max - max number of allowed function arguments

returnType - the type that the function's result will have

Throws:

TTXPathException - if the verify process is failing.

Method Detail

varifyParam

public final void varifyParam(int mNumber)
                       throws TTXPathException

Checks if the number of input arguments of this function is a valid according to the function specification in XQuery 1.0 and XPath 2.0 Functions and Operators. Throws an XPath error in case of a non-valid number.

Parameters:

mNumber - number of given function arguments

Throws:

TTXPathException - if function call fails.

reset

public void reset(long mNodeKey)

Resetting the nodekey of this axis to a given nodekey.

Overrides:

reset in class AbsExpression

Parameters:

mNodeKey - the nodekey where the reset should occur to.

evaluate

public AtomicValue evaluate()
                     throws TTXPathException

Performs the expression dependent evaluation of the expression. (Template method)

Specified by:

evaluate in class AbsExpression

Throws:

TTXPathException - if evaluation fails.

computeResult

protected abstract byte[] computeResult()
                                 throws TTXPathException

Computes the result value of the function. This implementation is acts as a hook operation and needs to be overridden by the concrete function classes, otherwise an exception is thrown.

Returns:

value of the result

Throws:

TTXPathException - if anythin odd happens while execution

getArgs

protected List<AbsAxis> getArgs()

Returns:

the list of function arguments