com.saxonica.ee.stream.feed

Class AbsorptionFeed

java.lang.Object

com.saxonica.ee.stream.feed.ItemFeed

com.saxonica.ee.stream.feed.AbsorptionFeed

All Implemented Interfaces:

Feed

Direct Known Subclasses:

CopyOfFeed, SimpleContentFeed, SnapshotFeed, StringValueFeed, TypedValueFeed

public abstract class AbsorptionFeed
extends ItemFeed

This class is used as an abstract superclass for expressions where the consuming operand is absorbed by the expression: for example, data(), string(), or copy-of(). It handles the fact that the input can be crawling, which means that selected nodes can be nested. We therefore need to be collecting the result values of multiple nodes during the same pass of the input. Hence we maintain a stack of values-under-construction. Moreover, an inner value will be available before the outer value, but it follows the outer value in document order, so it needs to be held pending until the outer value is available. Hence we maintain a list of values that are ready to be output.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AbsorptionFeed.PendingItem A pending item represents a tree under construction.

Constructor Summary

Constructors

Constructor and Description
AbsorptionFeed(Feed result, XPathContext context)

Method Summary

Methods

Modifier and Type	Method and Description
void	endSelectedParentNode(int locationId) Signal that the endElement event has occurred for the element whose startElement event caused the Watch to be activated.
protected abstract AbsorptionFeed.PendingItem	makePendingItem(int sequenceNr, FleetingParentNode node) Create a pending item (appropriate to the subclass) containing the data needed to compute the result value for one node in the streamed input sequence
protected abstract Sequence	processGroundedItem(Item item) Process a grounded item in the input sequence: either a streamed leaf node such as an attribute or text node, or an atomic value, or a non-streamed element or document node injected into the sequence for example by use of the comma operator.
void	processItem(Item item) Signal that a node (other than an element) that matches the selection has been found.
void	setHasFailed() Mark this feed as having failed (that is, as having detected and reported a dynamic error).
Receiver	startSelectedParentNode(FleetingParentNode node, int locationId) Signal that an element has been found that matches the selection that this Watch is looking for.

Methods inherited from class com.saxonica.ee.stream.feed.ItemFeed

close, dynamicError, getContext, getExpression, getPipelineConfiguration, getReceiver, getResult, getTerminator, hasFailed, open, processItems, setExpression, setPipelineConfiguration, setTerminator

Methods inherited from class java.lang.Object

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

Constructor Detail

AbsorptionFeed

public AbsorptionFeed(Feed result,
              XPathContext context)

Method Detail

startSelectedParentNode

public final Receiver startSelectedParentNode(FleetingParentNode node,
                               int locationId)
                                       throws XPathException

Signal that an element has been found that matches the selection that this Watch is looking for.

Specified by:

startSelectedParentNode in interface Feed

Overrides:

startSelectedParentNode in class ItemFeed

Parameters:

node - the node that matches the selection

locationId - @throws net.sf.saxon.type.ValidationException May be raised if the constraint implemented by this

Returns:

a Receiver to be notified of all events starting with the startElement/startDocument event for the matched element, and ending with the endElement event for that element; or null if this feature is not required.

Throws:

XPathException - May be raised if a dynamic error occurs

makePendingItem

protected abstract AbsorptionFeed.PendingItem makePendingItem(int sequenceNr,
                                         FleetingParentNode node)
                                                       throws XPathException

Create a pending item (appropriate to the subclass) containing the data needed to compute the result value for one node in the streamed input sequence

Parameters:

sequenceNr - the sequence number of this node within a set of nested nodes

node - the streamed input node

Returns:

the data needed to process this node

Throws:

XPathException - if a dynamic error is detected at this stage

endSelectedParentNode

public final void endSelectedParentNode(int locationId)
                                 throws XPathException

Signal that the endElement event has occurred for the element whose startElement event caused the Watch to be activated.

Specified by:

endSelectedParentNode in interface Feed

Overrides:

endSelectedParentNode in class ItemFeed

Parameters:

locationId - the location of the element

Throws:

XPathException - if a dynamic error occurs

processItem

public void processItem(Item item)
                 throws XPathException

Signal that a node (other than an element) that matches the selection has been found. This may be a leaf node in the streamed input, or it may be a grounded node or atomic value (of any kind) that has been mixed into the input sequence for example using a comma operator.

Specified by:

processItem in interface Feed

Specified by:

processItem in class ItemFeed

Parameters:

item - the node or other item that was matched.

Throws:

XPathException - May be raised if a dynamic error occurs

processGroundedItem

protected abstract Sequence processGroundedItem(Item item)
                                         throws XPathException

Process a grounded item in the input sequence: either a streamed leaf node such as an attribute or text node, or an atomic value, or a non-streamed element or document node injected into the sequence for example by use of the comma operator.

Parameters:

item - the grounded item

Returns:

the result of processing the grounded item

Throws:

XPathException - if a dynamic error occurs

setHasFailed

public void setHasFailed()

Description copied from class: ItemFeed

Mark this feed as having failed (that is, as having detected and reported a dynamic error). Once the feed is marked as having failed, it should not attempt to process any further input.

Overrides:

setHasFailed in class ItemFeed