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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 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.value;
import net.sf.saxon.expr.StaticProperty;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.om.GroundedValue;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.SingletonIterator;
/**
* A value that is a sequence containing zero or one items. Used only for nodes.
*/
public class SingletonItem implements GroundedValue {
/*@Nullable*/ protected T item = null;
/**
* Create a sequence containing zero or one items
* @param item The node or function-item to be contained in the sequence, or null if the sequence
* is to be empty
*/
public SingletonItem(T item) {
this.item = item;
}
public CharSequence getStringValueCS() throws XPathException {
return item.getStringValueCS();
}
/**
* Get the first item in the sequence.
*
* @return the first item in the sequence if there is one, or null if the sequence
* is empty
* @throws net.sf.saxon.trans.XPathException
* in the situation where the sequence is evaluated lazily, and
* evaluation of the first item causes a dynamic error.
*/
public Item head() throws XPathException {
return item;
}
/**
* Return the value in the form of an Item
* @return the value in the form of an Item
*/
/*@Nullable*/ public T asItem() {
return item;
}
/**
* Process the instruction, without returning any tail calls
* @param context The dynamic context, giving access to the current node,
* the current variables, etc.
*/
public void process(/*@NotNull*/ XPathContext context) throws XPathException {
if (item != null) {
context.getReceiver().append(item, 0, NodeInfo.ALL_NAMESPACES);
}
}
/**
* Determine the static cardinality
*/
public int getCardinality() {
if (item ==null) {
return StaticProperty.EMPTY;
} else {
return StaticProperty.EXACTLY_ONE;
}
}
/**
* Get the length of the sequence
*/
public int getLength() {
return (item ==null ? 0 : 1);
}
/**
* Get the n'th item in the sequence (starting from 0). This is defined for all
* SequenceValues, but its real benefits come for a SequenceValue stored extensionally
* (or for a MemoClosure, once all the values have been read)
*/
/*@Nullable*/ public T itemAt(int n) {
if (n==0 && item !=null) {
return item;
} else {
return null;
}
}
/**
* Get a subsequence of the value
*
*
* @param start the index of the first item to be included in the result, counting from zero.
* A negative value is taken as zero. If the value is beyond the end of the sequence, an empty
* sequence is returned
* @param length the number of items to be included in the result. Specify Integer.MAX_VALUE to
* get the subsequence up to the end of the base sequence. If the value is negative, an empty sequence
* is returned. If the value goes off the end of the sequence, the result returns items up to the end
* of the sequence
* @return the required subsequence. If min is
*/
/*@NotNull*/ public GroundedValue subsequence(int start, int length) {
if (item != null && start <= 0 && start+length > 0) {
return this;
} else {
return EmptySequence.getInstance();
}
}
/**
* Return an enumeration of this nodeset value.
*/
/*@NotNull*/ public SequenceIterator iterate() {
return SingletonIterator.makeIterator(item);
}
/**
* Get the effective boolean value
*/
public boolean effectiveBooleanValue() {
return (item != null);
}
/**
* Convert the value to a string, using the serialization rules.
* For atomic values this is the same as a cast; for sequence values
* it gives a space-separated list. For QNames and NOTATIONS, or lists
* containing them, it fails.
*/
/*@NotNull*/ public String getStringValue() {
return (item ==null ? "" : item.getStringValue());
}
/**
* Returns a string representation of the object.
* @return a string representation of the object.
*/
@Override
public String toString() {
return item.toString();
}
/**
* Reduce the sequence to its simplest form. If the value is an empty sequence, the result will be
* EmptySequence.getInstance(). If the value is a single atomic value, the result will be an instance
* of AtomicValue. If the value is a single item of any other kind, the result will be an instance
* of SingletonItem. Otherwise, the result will typically be unchanged.
*
* @return the simplified sequence
*/
public GroundedValue reduce() {
return this;
}
}