net.sf.saxon.functions.StreamAvailable Maven / Gradle / Ivy
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.functions;
import net.sf.saxon.event.PipelineConfiguration;
import net.sf.saxon.event.ProxyReceiver;
import net.sf.saxon.event.Receiver;
import net.sf.saxon.event.Sink;
import net.sf.saxon.expr.Callable;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.expr.parser.RetainedStaticContext;
import net.sf.saxon.lib.ParseOptions;
import net.sf.saxon.om.AttributeMap;
import net.sf.saxon.om.NamespaceMap;
import net.sf.saxon.om.NodeName;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.s9api.Location;
import net.sf.saxon.trans.QuitParsingException;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.SchemaType;
import net.sf.saxon.value.BooleanValue;
/**
* This class implements the XSLT 3.0 function stream-available()
*/
public class StreamAvailable extends SystemFunction implements Callable {
/**
* Call the Callable.
*
* @param context the dynamic evaluation context
* @param arguments the values of the arguments, supplied as Sequences.
* Generally it is advisable, if calling iterate() to process a supplied sequence, to
* call it only once; if the value is required more than once, it should first be converted
* to a {@link net.sf.saxon.om.GroundedValue} by calling the utility methd
* SequenceTool.toGroundedValue().
* If the expected value is a single item, the item should be obtained by calling
* Sequence.head(): it cannot be assumed that the item will be passed as an instance of
* {@link net.sf.saxon.om.Item} or {@link net.sf.saxon.value.AtomicValue}.
* It is the caller's responsibility to perform any type conversions required
* to convert arguments to the type expected by the callee. An exception is where
* this Callable is explicitly an argument-converting wrapper around the original
* Callable.
* @return the result of the evaluation, in the form of a Sequence. It is the responsibility
* of the callee to ensure that the type of result conforms to the expected result type.
* @throws net.sf.saxon.trans.XPathException
* if a dynamic error occurs during the evaluation of the argument
*/
@Override
public BooleanValue call(XPathContext context, Sequence[] arguments) throws XPathException {
boolean result = isAvailable(arguments[0].head().getStringValue(), context);
return BooleanValue.get(result);
}
/**
* Do the work.
* @param uri the URI to be tested
* @param context the dynamic evaluation context
* @return boolean true if the stream is available as defined by the spec
*/
private boolean isAvailable(String uri, XPathContext context) {
try {
Receiver tester = new StreamTester(context.getConfiguration().makePipelineConfiguration());
RetainedStaticContext env = getRetainedStaticContext();
DocumentFn.sendDoc(uri, env.getStaticBaseUriString(), env.getPackageData(), context, null, tester, new ParseOptions());
} catch (QuitParsingException e) {
// Indicates that the first element was reported and the parse was then aborted
return true;
} catch (XPathException e) {
return false;
}
return false;
}
/**
* An implementation of Receiver which does nothing other than throwing a QuitParsingException
* when the first startElement event is notified
*/
private static class StreamTester extends ProxyReceiver {
public StreamTester(PipelineConfiguration pipe) {
super(new Sink(pipe));
}
@Override
public void startElement(NodeName elemName, SchemaType type,
AttributeMap attributes, NamespaceMap namespaces,
Location location, int properties) throws XPathException {
throw new QuitParsingException(false);
}
}
}