uk.ac.sheffield.jast.filter

Class PositionFilter

java.lang.Object

uk.ac.sheffield.jast.filter.Filter

uk.ac.sheffield.jast.filter.MaskFilter

uk.ac.sheffield.jast.filter.EvalFilter

uk.ac.sheffield.jast.filter.PositionFilter

public class PositionFilter
extends EvalFilter

PositionFilter is a filter accepting sibling nodes before or after an index. A PositionFilter is typically applied after other filters, to select a range of Content-nodes above, or below a certain reference index. The comparison operator can be any of the six comparison operators, and the index is an integer, representing the indexed position of one of the sibling nodes to be tested. When PositionFilter is applied successively to sibling nodes of the same parent, it will count nodes and accept those whose count index stands in the comparison relationship with the reference index.

PositionFilter can only count children of the same parent node; but counted nodes may be a subset of the parent's children. If PositionFilter is applied to children of a different parent, it will start counting again from zero. This is the only way that the same PositionFilter object can be reliably reused. Indexing follows the W3C XPath standard, that is, the first visited index is 1 rather than 0.

Version:

2.5

Author:

Anthony J H Simons

Field Summary

Fields

Modifier and Type	Field and Description
private int	count The local counting index, used to perform counting.
private int	index The stored search index at which to report true.
private Content	parent The parent of the nodes being filtered.

Fields inherited from class uk.ac.sheffield.jast.filter.MaskFilter

mask

Fields inherited from class uk.ac.sheffield.jast.filter.Filter

ALLCONTENT, NAMENODES, PARENTNODES, PROPERTYNODES, VALUENODES, XPATHNODES, XPATHTEXT

Constructor Summary

Constructors

Modifier	Constructor and Description
private	PositionFilter(PositionFilter filter, int contentType) Secret constructor to copy a PositionFilter but reset the type mask.
	PositionFilter(java.lang.String operator, int index) Creates a PositionFilter accepting any siblings, whose index stands in the given relationship with a reference index.
	PositionFilter(java.lang.String operator, int index, int contentType) Creates a PositionFilter accepting siblings of the given content type, whose index stands in the given relationship with a reference index.

Method Summary

Modifier and Type	Method and Description
boolean	accept(Content node) Reports whether a given Content node is accepted by this PositionFilter.
Filter	and(Filter filter) Creates a Filter that is the logical AND of this PositionFilter and another Filter.
protected PositionFilter	andNodeFilter(NodeFilter other) Creates a Filter that is the conjunction of this PositionFilter and a NodeFilter.
private boolean	inRange(Content node) Counts one of a list of siblings to be counted, and returns true if the counting index stands in the specified comparison relationship with the reference index.

Methods inherited from class uk.ac.sheffield.jast.filter.EvalFilter

compareBoolean, compareDecimal, compareIntegral, compareString

Methods inherited from class uk.ac.sheffield.jast.filter.MaskFilter

getMask

Methods inherited from class uk.ac.sheffield.jast.filter.Filter

andIndexFilter, not, or, orNodeFilter, toString

Methods inherited from class java.lang.Object

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

Field Detail

parent

private Content parent

The parent of the nodes being filtered.

index

private int index

The stored search index at which to report true.

count

private int count

The local counting index, used to perform counting.

Constructor Detail

PositionFilter

public PositionFilter(java.lang.String operator,
                      int index)

Creates a PositionFilter accepting any siblings, whose index stands in the given relationship with a reference index.

Parameters:

operator - a comparison operator, as a String.

index - a reference index.

PositionFilter

public PositionFilter(java.lang.String operator,
                      int index,
                      int contentType)

Creates a PositionFilter accepting siblings of the given content type, whose index stands in the given relationship with a reference index.

Parameters:

operator - a comparison operator, as a String.

index - a reference index.

contentType - a bit-mask specifying one or more content types.

PositionFilter

private PositionFilter(PositionFilter filter,
                       int contentType)

Secret constructor to copy a PositionFilter but reset the type mask. This constructor is used by the methods that logically combine this PositionFilter with another NodeFilter. Much more efficient that having to re-analyse the operator.

Parameters:

filter - the copied PositionFilter.

contentType - a bit-mask specifying one or more content types.

Method Detail

inRange

private boolean inRange(Content node)

Counts one of a list of siblings to be counted, and returns true if the counting index stands in the specified comparison relationship with the reference index. Examines the parent-node of the counted Content node and, if this parent has not been seen before, registers it as the current parent and starts counting from scratch. If the parent has been seen before, the Content node is the next child of the same parent and the counting index is incremented. Returns true if the comparison holds between the counting and reference indices.

Parameters:

node - the Content node to be counted.

Returns:

true if the node is within the counted range.

accept

public boolean accept(Content node)

Reports whether a given Content node is accepted by this PositionFilter. A node is accepted, if it is one of a sequence of sibling nodes found at an index that lies within a range specified by an inequality relationship. Ranges are specified with reference to an index, which ranges from 1..N. All counted nodes in a sequence must be siblings (counting restarts if the parent is changed). Counting may occur after other filters have been applied, so may apply to a subset of siblings.

Overrides:

accept in class MaskFilter

Parameters:

node - a Content node.

Returns:

true, if the node is accepted, otherwise false.

and

public Filter and(Filter filter)

Creates a Filter that is the logical AND of this PositionFilter and another Filter. Ensures that any AndFilter includes the other filter as its first conjunct and this PositionFilter as its second conjunct, so that this PositionFilter counts only those nodes that were passed by the other filter. If both filters are PositionFilters, does not reverse the operands.

Overrides:

and in class Filter

Parameters:

filter - the other Filter.

Returns:

a new Filter, the conjunction of this and the other Filter.

andNodeFilter

protected PositionFilter andNodeFilter(NodeFilter other)

Creates a Filter that is the conjunction of this PositionFilter and a NodeFilter. Returns a new PositionFilter accepting in the same range, but combining the bit-masks of this and the other NodeFilter using bitwise-AND. This is more efficient than the general approach using an AndFilter.

Overrides:

andNodeFilter in class Filter

Parameters:

other - the other NodeFilter.

Returns:

a new Filter.