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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.functions;
import net.sf.saxon.Configuration;
import net.sf.saxon.expr.*;
import net.sf.saxon.expr.parser.ExpressionTool;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.Optimizer;
import net.sf.saxon.expr.parser.TypeChecker;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.pattern.NodeTest;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.BooleanValue;
/**
* This class supports the XPath function boolean()
*/
public class BooleanFn extends SystemFunctionCall implements Negatable, Callable {
/**
* Static analysis: prevent sorting of the argument
*/
public void checkArguments(/*@NotNull*/ ExpressionVisitor visitor) throws XPathException {
super.checkArguments(visitor);
XPathException err = TypeChecker.ebvError(argument[0], visitor.getConfiguration().getTypeHierarchy());
if (err != null) {
err.setLocator(this);
throw err;
}
Optimizer opt = visitor.getConfiguration().obtainOptimizer();
argument[0] = ExpressionTool.unsortedIfHomogeneous(opt, argument[0]);
}
/**
* Perform optimisation of an expression and its subexpressions.
*
* 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.
*
* @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 net.sf.saxon.type.Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws XPathException if an error is discovered during this phase
* (typically a type error)
*/
/*@NotNull*/
public Expression optimize(/*@NotNull*/ ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
Expression e = super.optimize(visitor, contextItemType);
if (e == this) {
Expression ebv = rewriteEffectiveBooleanValue(argument[0], visitor, contextItemType);
if (ebv != null) {
ebv = ebv.optimize(visitor, contextItemType);
if (ebv.getItemType(visitor.getConfiguration().getTypeHierarchy()) == BuiltInAtomicType.BOOLEAN &&
ebv.getCardinality() == StaticProperty.EXACTLY_ONE) {
return ebv;
} else {
argument[0] = ebv;
adoptChildExpression(ebv);
return this;
}
}
}
return e;
}
/**
* Check whether this specific instance of the expression is negatable
*
* @return true if it is
*/
public boolean isNegatable(ExpressionVisitor visitor) {
return true;
}
/**
* Create an expression that returns the negation of this expression
* @return the negated expression
*/
public Expression negate() {
return SystemFunctionCall.makeSystemFunction("not", getArguments());
}
/**
* Optimize an expression whose effective boolean value is required. It is appropriate
* to apply this rewrite to any expression whose value will be obtained by calling
* the Expression.effectiveBooleanValue() method (and not otherwise)
* @param exp the expression whose EBV is to be evaluated
* @param visitor an expression visitor
* @param contextItemType the type of the context item for this expression
* @return an expression that returns the EBV of exp, or null if no optimization was possible
* @throws XPathException if static errors are found
*/
public static Expression rewriteEffectiveBooleanValue(
Expression exp, ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
Configuration config = visitor.getConfiguration();
TypeHierarchy th = config.getTypeHierarchy();
exp = ExpressionTool.unsortedIfHomogeneous(config.obtainOptimizer(), exp);
if (exp instanceof ValueComparison) {
ValueComparison vc = (ValueComparison)exp;
if (vc.getResultWhenEmpty() == null) {
vc.setResultWhenEmpty(BooleanValue.FALSE);
}
return exp;
} else if (exp instanceof BooleanFn) {
return ((BooleanFn)exp).getArguments()[0];
} else if (th.isSubType(exp.getItemType(th), BuiltInAtomicType.BOOLEAN) &&
exp.getCardinality() == StaticProperty.EXACTLY_ONE) {
return exp;
} else if (exp instanceof Count) {
// rewrite boolean(count(x)) => exists(x)
FunctionCall exists = SystemFunctionCall.makeSystemFunction("exists", ((Count) exp).getArguments());
assert exists != null;
exists.setLocationId(exp.getLocationId());
return exists.optimize(visitor, contextItemType);
} else if (exp.getItemType(th) instanceof NodeTest) {
// rewrite boolean(x) => exists(x)
FunctionCall exists = SystemFunctionCall.makeSystemFunction("exists", new Expression[]{exp});
assert exists != null;
exists.setLocationId(exp.getLocationId());
return exists.optimize(visitor, contextItemType);
} else {
return null;
}
}
/**
* Evaluate the function
*/
public BooleanValue evaluateItem(XPathContext context) throws XPathException {
return BooleanValue.get(effectiveBooleanValue(context));
}
/**
* Evaluate the effective boolean value
*/
public boolean effectiveBooleanValue(XPathContext c) throws XPathException {
try {
return argument[0].effectiveBooleanValue(c);
} catch (XPathException e) {
e.maybeSetLocation(this);
e.maybeSetContext(c);
throw e;
}
}
public Sequence call(XPathContext c, Sequence[] arguments) throws XPathException {
try {
boolean bValue = ExpressionTool.effectiveBooleanValue(arguments[0].iterate());
return BooleanValue.get(bValue);
} catch (XPathException e) {
e.maybeSetLocation(this);
e.maybeSetContext(c);
throw e;
}
}
}