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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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.expr;
import net.sf.saxon.expr.parser.*;
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;
/**
* Expression class for a cast to a union type
*/
public class CastToUnion extends UnaryExpression {
private UnionType targetType;
private boolean allowEmpty;
/**
* Create a cast expression to a union type
* @param source the operand of the cast
* @param targetType the union type that is the result of the cast
* @param allowEmpty true if an empty sequence may be supplied as input, converting to an empty sequence on output
*/
public CastToUnion(Expression source, UnionType targetType, boolean allowEmpty) {
super(source);
this.targetType = targetType;
this.allowEmpty = allowEmpty;
}
/**
* Get the usage (in terms of streamability analysis) of the single operand
* @return the operand usage
*/
protected OperandRole getOperandRole() {
return OperandRole.SINGLE_ATOMIC;
}
/**
* Ask whether the value of the operand is allowed to be empty
* @return true if an empty sequence may be supplied as input, converting to an empty sequence on output
*/
public boolean isAllowEmpty() {
return allowEmpty;
}
/**
* Get the union type that is the target of this cast operation
* @return the target type of the cast
*/
public UnionType getTargetType() {
return targetType;
}
/**
* Get the namespace resolver that will be used to resolve any namespace-sensitive values (such as QNames) when casting
* @return the namespace resolver, or null if there is none.
*/
public NamespaceResolver getNamespaceResolver() {
return getRetainedStaticContext();
}
/**
* Type-check the expression
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
typeCheckChildren(visitor, contextInfo);
SequenceType atomicType = SequenceType.makeSequenceType(BuiltInAtomicType.ANY_ATOMIC, getCardinality());
RoleDiagnostic role = new RoleDiagnostic(RoleDiagnostic.TYPE_OP, "cast as", 0);
Expression operand = TypeChecker.staticTypeCheck(getBaseExpression(), atomicType, false, role, visitor);
setBaseExpression(operand);
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.getLength() == 0) {
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.setLocation(getLocation());
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 contextInfo 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, ContextItemStaticInfo contextInfo) throws XPathException {
Expression e2 = super.optimize(visitor, contextInfo);
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(getBaseExpression().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(getBaseExpression().getCardinality())) {
c |= StaticProperty.ALLOWS_ZERO;
}
try {
if (targetType.containsListType()) {
c |= StaticProperty.ALLOWS_ZERO;
c |= StaticProperty.ALLOWS_MANY;
}
} catch (MissingComponentException e) {
c |= StaticProperty.ALLOWS_ZERO;
c |= StaticProperty.ALLOWS_MANY;
}
return c;
}
/**
* Get the static type of the expression
*/
/*@NotNull*/
public ItemType getItemType() {
if (targetType instanceof PlainType) {
return 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);
ExpressionTool.copyLocationInfo(this, c);
c.setRetainedStaticContext(getRetainedStaticContext());
return c;
}
/**
* An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
* This method indicates which of these methods is provided directly. The other methods will always be available
* indirectly, using an implementation that relies on one of the other methods.
*
* @return the implementation method, for example {@link #ITERATE_METHOD} or {@link #EVALUATE_METHOD} or
* {@link #PROCESS_METHOD}
*/
@Override
public int getImplementationMethod() {
return ITERATE_METHOD;
}
/**
* Evaluate the expression
*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
ConversionRules rules = context.getConfiguration().getConversionRules();
AtomicValue value = (AtomicValue) getBaseExpression().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.setLocation(getLocation());
e.setErrorCode("XPTY0004");
throw e;
}
}
try {
AtomicSequence result = cast(value, targetType, getRetainedStaticContext(), rules);
return result.iterate();
} catch (XPathException err) {
err.maybeSetContext(context);
err.maybeSetLocation(getLocation());
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)
*/
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();
Iterable memberTypes = targetType.getPlainMemberTypes();
// 2a. Is the type annotation itself a member type of the union?
for (PlainType member : memberTypes) {
if (label.equals(member)) {
return value;
}
}
// 2b. Failing that, is some supertype of the type annotation a member type of the union?
for (PlainType member : memberTypes) {
AtomicType t = label;
while (t != null) {
if (t.equals(member)) {
return value;
} else {
t = t.getBaseType() instanceof AtomicType ? (AtomicType) t.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 " + targetType.getDescription(), "FORG0001");
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
other instanceof CastToUnion &&
targetType == ((CastToUnion) other).targetType &&
allowEmpty == ((CastToUnion) other).allowEmpty &&
ExpressionTool.equalOrNull(getRetainedStaticContext(), ((CastToUnion) other).getRetainedStaticContext());
}
/**
* 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() + "(" + getBaseExpression().toString() + ")";
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void export(ExpressionPresenter out) {
out.startElement("castToUnion", this);
out.emitAttribute("as", targetType.toString());
getBaseExpression().export(out);
out.endElement();
}
}
// Copyright (c) 2011 Saxonica Limited. All rights reserved.
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