net.sf.saxon.evpull.SequenceComposer Maven / Gradle / Ivy
Show all versions of Saxon-HE Show documentation
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2015 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.evpull;
import net.sf.saxon.event.PipelineConfiguration;
import net.sf.saxon.event.TreeReceiver;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.tiny.Statistics;
import net.sf.saxon.tree.tiny.TinyBuilder;
/**
* This class takes a sequence of pull events and composes them into a sequence of items. This involves building
* any element or document nodes that are presented in decomposed form.
*
* Note: this SequenceIterator does not implement the getAnother() method, which limits its use,
* since getAnother() is needed to support the XPath last() function.
*/
public class SequenceComposer implements SequenceIterator {
private EventIterator base;
private PipelineConfiguration pipe;
/**
* Create a sequence composer
*
* @param iter the underlying event iterator
* @param pipe the pipeline configuration
*/
public SequenceComposer(EventIterator iter, PipelineConfiguration pipe) {
base = EventStackIterator.flatten(iter);
this.pipe = pipe;
}
/**
* Get the next item in the sequence. This method changes the state of the
* iterator, in particular it affects the result of subsequent calls of
* position() and current().
*
* @return the next item, or null if there are no more items. Once a call
* on next() has returned null, no further calls should be made. The preferred
* action for an iterator if subsequent calls on next() are made is to return
* null again, and all implementations within Saxon follow this rule.
* @throws net.sf.saxon.trans.XPathException
* if an error occurs retrieving the next item
* @since 8.4
*/
public Item next() throws XPathException {
PullEvent pe = base.next();
if (pe == null) {
return null;
}
if (pe instanceof Item) {
return (Item) pe;
} else if (pe instanceof StartDocumentEvent || pe instanceof StartElementEvent) {
SubtreeIterator sub = new SubtreeIterator(base, pe);
TinyBuilder builder = new TinyBuilder(pipe);
builder.setStatistics(Statistics.TEMPORARY_TREE_STATISTICS);
TreeReceiver receiver = new TreeReceiver(builder);
EventIteratorToReceiver.copy(sub, receiver);
return builder.getCurrentRoot();
} else {
throw new IllegalStateException(pe.getClass().getName());
}
}
public void close() {
}
/**
* Get another SequenceIterator that iterates over the same items as the original,
* but which is repositioned at the start of the sequence.
*
* This method allows access to all the items in the sequence without disturbing the
* current position of the iterator. Internally, its main use is in evaluating the last()
* function.
*
* This method does not change the state of the iterator.
*
* @return a SequenceIterator that iterates over the same items,
* positioned before the first item
* @throws net.sf.saxon.trans.XPathException
* if any error occurs
* @since 8.4
*/
/*@NotNull*/
public SequenceIterator getAnother() throws XPathException {
throw new UnsupportedOperationException("getAnother");
}
/**
* Get properties of this iterator, as a bit-significant integer.
*
* @return the properties of this iterator. This will be some combination of
* properties such as {@link #GROUNDED}, {@link #LAST_POSITION_FINDER},
* and {@link #LOOKAHEAD}. It is always
* acceptable to return the value zero, indicating that there are no known special properties.
* It is acceptable for the properties of the iterator to change depending on its state.
* @since 8.6
*/
public int getProperties() {
return 0;
}
private static class SubtreeIterator implements EventIterator {
private int level = 0;
private EventIterator base;
private PullEvent first;
public SubtreeIterator(EventIterator base, PullEvent first) {
this.base = base;
this.first = first;
}
/**
* Get the next event in the sequence
*
* @return the next event, or null when the sequence is exhausted. Note that since an EventIterator is
* itself a PullEvent, this method may return a nested iterator.
* @throws net.sf.saxon.trans.XPathException
* if a dynamic evaluation error occurs
*/
public PullEvent next() throws XPathException {
if (first != null) {
PullEvent pe = first;
first = null;
return pe;
}
if (level < 0) {
return null;
}
PullEvent pe = base.next();
if (pe instanceof StartElementEvent || pe instanceof StartDocumentEvent) {
level++;
} else if (pe instanceof EndElementEvent || pe instanceof EndDocumentEvent) {
level--;
}
return pe;
}
/**
* Determine whether the EventIterator returns a flat sequence of events, or whether it can return
* nested event iterators
*
* @return true if the next() method is guaranteed never to return an EventIterator
*/
public boolean isFlatSequence() {
return base.isFlatSequence();
}
}
/**
* Main method for testing only
*
* @param args not used
* @throws Exception
*/
// public static void main(String[] args) throws Exception {
// Configuration config = new Configuration();
// DocumentInfo doc = config.buildDocument(new StreamSource(new File("c:/MyJava/samples/data/books.xml")));
// PipelineConfiguration pipe = config.makePipelineConfiguration();
// pipe.setHostLanguage(Configuration.XQUERY);
// EventIterator e = new Decomposer(new SingletonEventIterator(doc), pipe);
// SequenceIterator iter = new SequenceComposer(e, pipe);
// while (true) {
// NodeInfo item = (NodeInfo) iter.next();
// if (item == null) {
// break;
// }
// System.out.println(QueryResult.serialize(item));
// }
// }
}