package client.net.sf.saxon.ce.functions;
import client.net.sf.saxon.ce.expr.*;
import client.net.sf.saxon.ce.expr.instruct.SimpleNodeConstructor;
import client.net.sf.saxon.ce.om.Item;
import client.net.sf.saxon.ce.trans.XPathException;
import client.net.sf.saxon.ce.type.BuiltInAtomicType;
import client.net.sf.saxon.ce.type.ItemType;
import client.net.sf.saxon.ce.type.TypeHierarchy;
import client.net.sf.saxon.ce.value.StringValue;
/**
* Implement XPath function string()
*/
public class StringFn extends SystemFunction {
public StringFn newInstance() {
return new StringFn();
}
/**
* Simplify and validate.
* This is a pure function so it can be simplified in advance if the arguments are known
* @param visitor an expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
useContextItemAsDefault();
argument[0].setFlattened(true);
return simplifyArguments(visitor);
}
/**
* Perform optimisation of an expression and its subexpressions.
* <p/>
* <p>This method is called after all references to functions and variables have been resolved
* to the declaration of the function or variable, and after all type checking has been done.</p>
* @param visitor an expression visitor
* @param contextItemType the static type of "." at the point where this expression is invoked.
* The parameter is set to null if it is known statically that the context item will be undefined.
* If the type of the context item is not known statically, the argument is set to
* {@link client.net.sf.saxon.ce.type.Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws client.net.sf.saxon.ce.trans.XPathException
* if an error is discovered during this phase
* (typically a type error)
*/
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
Expression e = super.optimize(visitor, contextItemType);
if (e != this) {
return e;
}
TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
if (th.isSubType(argument[0].getItemType(th), BuiltInAtomicType.STRING) &&
argument[0].getCardinality() == StaticProperty.EXACTLY_ONE) {
return argument[0];
}
if (argument[0] instanceof SimpleNodeConstructor) {
return ((SimpleNodeConstructor)argument[0]).getContentExpression();
}
return this;
}
/**
* Evaluate the function
*/
public Item evaluateItem(XPathContext c) throws XPathException {
try {
Item arg = argument[0].evaluateItem(c);
if (arg==null) {
return StringValue.EMPTY_STRING;
} else if (arg instanceof StringValue && ((StringValue)arg).getTypeLabel() == BuiltInAtomicType.STRING) {
return arg;
} else {
return StringValue.makeStringValue(arg.getStringValueCS());
}
} catch (UnsupportedOperationException e) {
// Cannot obtain the string value of a function item
typeError(e.getMessage(), "FOTY0014", c);
return null;
}
}
}
// 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.