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An OSGi bundle for Saxon-HE
package net.sf.saxon.expr;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.RoleLocator;
import net.sf.saxon.expr.parser.TypeChecker;
import net.sf.saxon.lib.ConversionRules;
import net.sf.saxon.om.*;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.*;
import net.sf.saxon.value.*;
import net.sf.saxon.value.StringValue;
import java.util.Set;
/**
* Expression class for a cast to a union type
*/
public class CastToUnion extends UnaryExpression {
private UnionType targetType;
private boolean allowEmpty;
/*@Nullable*/
private NamespaceResolver nsResolver = null;
public CastToUnion(Expression source, UnionType targetType, boolean allowEmpty) {
super(source);
this.targetType = targetType;
this.allowEmpty = allowEmpty;
}
public boolean isAllowEmpty() {
return allowEmpty;
}
public UnionType getTargetType() {
return targetType;
}
public NamespaceResolver getNamespaceResolver() {
return nsResolver;
}
/**
* Simplify the expression
*
* @param visitor an expression visitor
* @return the simplified expression
*/
/*@NotNull*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
if (targetType.isNamespaceSensitive()) {
StaticContext env = visitor.getStaticContext();
nsResolver = env.getNamespaceResolver();
}
operand = visitor.simplify(operand);
return this;
}
/**
* Type-check the expression
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
operand = visitor.typeCheck(operand, contextItemType);
SequenceType atomicType = SequenceType.makeSequenceType(BuiltInAtomicType.ANY_ATOMIC, getCardinality());
RoleLocator role = new RoleLocator(RoleLocator.TYPE_OP, "cast as", 0);
//role.setSourceLocator(this);
operand = TypeChecker.staticTypeCheck(operand, atomicType, false, role, visitor);
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
if (operand instanceof Literal) {
GroundedValue literalOperand = ((Literal) operand).getValue();
if (literalOperand instanceof AtomicValue) {
GroundedValue av = SequenceTool.toGroundedValue(iterate(visitor.getStaticContext().makeEarlyEvaluationContext()));
return Literal.makeLiteral(av);
}
if (literalOperand instanceof EmptySequence) {
if (allowEmpty) {
return operand;
} else {
XPathException err = new XPathException("Cast can never succeed: the operand must not be an empty sequence");
err.setErrorCode("XPTY0004");
err.setLocator(this);
err.setIsTypeError(true);
throw err;
}
}
}
return this;
}
/**
* 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 net.sf.saxon.trans.XPathException
* if an error is discovered during this phase
* (typically a type error)
*/
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
Expression e2 = super.optimize(visitor, contextItemType);
if (e2 != this) {
return e2;
}
// if the operand can't be empty, then set allowEmpty to false to provide more information for analysis
if (!Cardinality.allowsZero(operand.getCardinality())) {
allowEmpty = false;
resetLocalStaticProperties();
}
return this;
}
/**
* Get the static cardinality of the expression
*/
public int computeCardinality() {
int c = StaticProperty.ALLOWS_ONE;
if (allowEmpty && Cardinality.allowsZero(operand.getCardinality())) {
c |= StaticProperty.ALLOWS_ZERO;
}
if (targetType.containsListType()) {
c |= StaticProperty.ALLOWS_ZERO;
c |= StaticProperty.ALLOWS_MANY;
}
return c;
}
/**
* Get the static type of the expression
*
* @param th the type hierarchy cache
*/
/*@NotNull*/
public ItemType getItemType(TypeHierarchy th) {
if (targetType instanceof PlainType) {
return (PlainType)targetType;
}
return BuiltInAtomicType.ANY_ATOMIC;
}
/**
* Determine the special properties of this expression
*
* @return {@link StaticProperty#NON_CREATIVE}.
*/
public int computeSpecialProperties() {
int p = super.computeSpecialProperties();
return p | StaticProperty.NON_CREATIVE;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
CastToUnion c = new CastToUnion(getBaseExpression().copy(), targetType, allowEmpty);
c.nsResolver = nsResolver;
return c;
}
/**
* Evaluate the expression
*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
ConversionRules rules = context.getConfiguration().getConversionRules();
AtomicValue value = (AtomicValue) operand.evaluateItem(context);
if (value == null) {
if (allowEmpty) {
return null;
} else {
XPathException e = new XPathException("Cast does not allow an empty sequence");
e.setXPathContext(context);
e.setLocator(this);
e.setErrorCode("XPTY0004");
throw e;
}
}
try {
AtomicSequence result = cast(value, targetType, nsResolver, rules);
return result.iterate();
} catch (XPathException err) {
err.maybeSetContext(context);
err.maybeSetLocation(this);
err.setErrorCode("FORG0001");
throw err;
}
}
/**
* Static method to perform the castable check of an atomic value to a union type
*
* @param value the input value to be converted. Must not be null.
* @param targetType the union type to which the value is to be converted
* @param nsResolver the namespace context, required if the type is namespace-sensitive
* @param context the XPath dynamic evaluation context
* @return the result of the conversion (may be a sequence if the union includes list types in its membership)
* @throws XPathException if the conversion fails
*/
public static boolean castable(AtomicValue value, UnionType targetType,
NamespaceResolver nsResolver, XPathContext context) {
try {
CastToUnion.cast(value, targetType, nsResolver, context.getConfiguration().getConversionRules());
return true;
} catch (XPathException err) {
return false;
}
}
/**
* Static method to perform the cast of an atomic value to a union type
*
* @param value the input value to be converted. Must not be null.
* @param targetType the union type to which the value is to be converted
* @param nsResolver the namespace context, required if the type is namespace-sensitive
* @param rules the conversion rules
* @return the result of the conversion (may be a sequence if the union includes list types in its membership)
* @throws XPathException if the conversion fails
*/
public static AtomicSequence cast(AtomicValue value, UnionType targetType,
NamespaceResolver nsResolver, ConversionRules rules)
throws XPathException {
//ConversionRules rules = context.getConfiguration().getConversionRules();
if (value == null) {
throw new NullPointerException();
}
// 1. If the value is a string or untypedAtomic, try casting to each of the member types
if (value instanceof StringValue && !(value instanceof AnyURIValue)) {
try {
return targetType.getTypedValue(value.getStringValueCS(), nsResolver, rules);
} catch (ValidationException e) {
e.setErrorCode("FORG0001");
throw e;
}
}
// 2. If the value is an instance of a type in the transitive membership of the union, return it unchanged
AtomicType label = value.getItemType();
Set memberTypes = targetType.getPlainMemberTypes();
while (label != null) {
if (memberTypes.contains(label)) {
return value;
} else {
label = (label.getBaseType() instanceof AtomicType ? (AtomicType) label.getBaseType() : null);
}
}
// 3. if the value can be cast to any of the member types, return the result of that cast
for (PlainType type : memberTypes) {
if (type instanceof AtomicType) {
Converter c = rules.getConverter(value.getItemType(), (AtomicType) type);
if (c != null) {
ConversionResult result = c.convert(value);
if (result instanceof AtomicValue) {
return (AtomicValue) result;
}
}
}
}
throw new XPathException("Cannot convert the supplied value to the required union type", "FORG0001");
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
targetType == ((CastToUnion) other).targetType &&
allowEmpty == ((CastToUnion) other).allowEmpty &&
nsResolver == ((CastToUnion) other).nsResolver;
}
/**
* get HashCode for comparing two expressions.
*/
@Override
public int hashCode() {
return super.hashCode() ^ targetType.hashCode();
}
/**
* The toString() method for an expression attempts to give a representation of the expression
* in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
* In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
*/
public String toString() {
return targetType.getEQName() + "(" + operand.toString() + ")";
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter out) {
out.startElement("castToUnion");
out.emitAttribute("as", targetType.toString());
operand.explain(out);
out.endElement();
}
}
// Copyright (c) 2011 Saxonica Limited. All rights reserved.