package net.sf.saxon.expr;
import net.sf.saxon.event.SequenceReceiver;
import net.sf.saxon.event.TypeCheckingFilter;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NamePool;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.pattern.DocumentNodeTest;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.*;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.Value;
/**
* A ItemChecker implements the item type checking of "treat as": that is,
* it returns the supplied sequence, checking that all its items are of the correct type
*/
public final class ItemChecker extends UnaryExpression {
private ItemType requiredItemType;
private RoleLocator role;
/**
* Constructor
* @param sequence the expression whose value we are checking
* @param itemType the required type of the items in the sequence
* @param role information used in constructing an error message
*/
public ItemChecker(Expression sequence, ItemType itemType, RoleLocator role) {
super(sequence);
requiredItemType = itemType;
this.role = role;
adoptChildExpression(sequence);
}
/**
* Get the required type
* @return the required type of the items in the sequence
*/
public ItemType getRequiredType() {
return requiredItemType;
}
/**
* Get the RoleLocator (used to construct error messages)
* @return the RoleLocator
*/
public RoleLocator getRoleLocator() {
return role;
}
/**
* Simplify an expression
* @param visitor an expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
operand = visitor.simplify(operand);
if (requiredItemType instanceof AnyItemType) {
return operand;
}
return this;
}
/**
* Type-check the expression
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
operand = visitor.typeCheck(operand, contextItemType);
// When typeCheck is called a second time, we might have more information...
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
int card = operand.getCardinality();
if (card == StaticProperty.EMPTY) {
//value is always empty, so no item checking needed
return operand;
}
ItemType supplied = operand.getItemType(th);
int relation = th.relationship(requiredItemType, supplied);
if (relation == TypeHierarchy.SAME_TYPE || relation == TypeHierarchy.SUBSUMES) {
return operand;
} else if (relation == TypeHierarchy.DISJOINT) {
final NamePool namePool = visitor.getConfiguration().getNamePool();
if (Cardinality.allowsZero(card)) {
String message = role.composeErrorMessage(
requiredItemType, operand.getItemType(th), namePool);
visitor.getStaticContext().issueWarning("The only value that can pass type-checking is an empty sequence. " +
message, this);
} else if (requiredItemType.equals(BuiltInAtomicType.STRING) && th.isSubType(supplied, BuiltInAtomicType.ANY_URI)) {
// URI promotion will take care of this at run-time
return operand;
} else {
String message = role.composeErrorMessage(requiredItemType, operand.getItemType(th), namePool);
XPathException err = new XPathException(message);
err.setErrorCode(role.getErrorCode());
err.setLocator(this);
err.setIsTypeError(true);
throw err;
}
}
return this;
}
/**
* 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. This implementation provides both iterate() and
* process() methods natively.
*/
public int getImplementationMethod() {
int m = ITERATE_METHOD | PROCESS_METHOD;
if (!Cardinality.allowsMany(getCardinality())) {
m |= EVALUATE_METHOD;
}
return m;
}
/**
* Iterate over the sequence of values
*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
SequenceIterator base = operand.iterate(context);
ItemCheckMappingFunction map = new ItemCheckMappingFunction();
map.externalContext = context;
return new ItemMappingIterator(base, map);
}
/**
* Mapping function: this is used only if the expression does not allow a sequence of more than
* one item.
*/
private class ItemCheckMappingFunction implements ItemMappingFunction {
public XPathContext externalContext;
public Item map(Item item) throws XPathException {
testConformance(item, externalContext);
return item;
}
}
/**
* Evaluate as an Item.
*/
public Item evaluateItem(XPathContext context) throws XPathException {
Item item = operand.evaluateItem(context);
if (item==null) return null;
testConformance(item, context);
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(XPathContext context) throws XPathException {
Expression next = operand;
int card = StaticProperty.ALLOWS_ZERO_OR_MORE;
if (next instanceof CardinalityChecker) {
card = ((CardinalityChecker)next).getRequiredCardinality();
next = ((CardinalityChecker)next).getBaseExpression();
}
if ((next.getImplementationMethod() & PROCESS_METHOD) != 0 && !(requiredItemType instanceof DocumentNodeTest)) {
SequenceReceiver out = context.getReceiver();
TypeCheckingFilter filter = new TypeCheckingFilter();
filter.setUnderlyingReceiver(out);
filter.setPipelineConfiguration(out.getPipelineConfiguration());
filter.setRequiredType(requiredItemType, card, role);
context.setReceiver(filter);
next.process(context);
filter.close();
context.setReceiver(filter);
} else {
super.process(context);
}
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
public Expression copy() {
return new ItemChecker(getBaseExpression().copy(), requiredItemType, role);
}
private void testConformance(Item item, XPathContext context) throws XPathException {
if (!requiredItemType.matchesItem(item, true, (context == null ? null : context.getConfiguration()))) {
String message;
if (context == null) {
// no name pool available
message = "Supplied value of type " + Type.displayTypeName(item) +
" does not match the required type of " + role.getMessage();
} else {
final NamePool pool = context.getNamePool();
final TypeHierarchy th = context.getConfiguration().getTypeHierarchy();
message = role.composeErrorMessage(requiredItemType, Value.asValue(item).getItemType(th), pool);
}
String errorCode = role.getErrorCode();
if ("XPDY0050".equals(errorCode)) {
// error in "treat as" assertion
dynamicError(message, errorCode, context);
} else {
typeError(message, errorCode, context);
}
}
}
/**
* Determine the data type of the items returned by the expression
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
// TODO: take the intersection of the required type with the static type of the operand
return requiredItemType;
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
requiredItemType == ((ItemChecker)other).requiredItemType;
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter out) {
out.startElement("treat");
out.emitAttribute("as", requiredItemType.toString(out.getConfiguration().getNamePool()));
operand.explain(out);
out.endElement();
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//