com.saxonica.ee.stream.adjunct

Class FirstItemExpressionAdjunct

java.lang.Object

com.saxonica.ee.stream.adjunct.StreamingAdjunct

com.saxonica.ee.stream.adjunct.TransmissionAdjunct

com.saxonica.ee.stream.adjunct.FilteringAdjunct

com.saxonica.ee.stream.adjunct.FirstItemExpressionAdjunct

All Implemented Interfaces:

FeedMaker

public class FirstItemExpressionAdjunct
extends FilteringAdjunct
implements FeedMaker

Generate streaming code for a first item expression (when not part of a Watch).

Constructor Summary

Constructors

Constructor and Description
FirstItemExpressionAdjunct()

Method Summary

Methods

Modifier and Type	Method and Description
PostureAndSweep	computeStreamability(boolean allowExtensions, ContextItemStaticInfo contextInfo, List<String> reasons) Get the posture and sweep of this expression as defined in the W3C streamability specifications.
FilteringFeed.Filter	makeFilter(XPathContext context) Make a filter for the event stream
Pattern	toStreamingPattern(Configuration config) Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)

Methods inherited from class com.saxonica.ee.stream.adjunct.FilteringAdjunct

makeItemFeed

Methods inherited from class com.saxonica.ee.stream.adjunct.TransmissionAdjunct

getWatchMaker, makeTransmissionFlow

Methods inherited from class com.saxonica.ee.stream.adjunct.StreamingAdjunct

getConfiguration, getDefaultFeedMaker, getExpression, getFeedMaker, setConfiguration, setExpression

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.saxonica.ee.stream.feed.FeedMaker

makeItemFeed

Constructor Detail

FirstItemExpressionAdjunct

public FirstItemExpressionAdjunct()

Method Detail

computeStreamability

public PostureAndSweep computeStreamability(boolean allowExtensions,
                                   ContextItemStaticInfo contextInfo,
                                   List<String> reasons)

Get the posture and sweep of this expression as defined in the W3C streamability specifications. This provides an assessment of stylesheet code against the W3C criteria for guaranteed streamability, and is implemented to allow these criteria to be tested. It is not the case that all expression that emerge as streamable from this analysis are currently capable of being streamed by Saxon

Overrides:

computeStreamability in class StreamingAdjunct

Parameters:

allowExtensions - if false, the definition of "guaranteed streamability" in the W3C specification is used. If true, Saxon extensions are permitted, which make some

contextInfo - Information about the context item type and posture

reasons - the caller may supply a list, in which case the implementation may add to this

Returns:

the posture and sweep of the expression

toStreamingPattern

public Pattern toStreamingPattern(Configuration config)

Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)

Overrides:

toStreamingPattern in class StreamingAdjunct

Parameters:

config - the Saxon configuration

Returns:

the equivalent pattern if conversion succeeds; otherwise null

makeFilter

public FilteringFeed.Filter makeFilter(XPathContext context)
                                throws XPathException

Make a filter for the event stream

Specified by:

makeFilter in class FilteringAdjunct

Parameters:

context - the XPath dyamic context

Returns:

a filter that can be added to the event stream

Throws:

XPathException - if a dynamic evaluation error occurs