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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.event.SequenceReceiver;
import net.sf.saxon.event.TypeCheckingFilter;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.pattern.CombinedNodeTest;
import net.sf.saxon.pattern.DocumentNodeTest;
import net.sf.saxon.pattern.NodeTest;
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.IntegerValue;
/**
* 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 RoleDiagnostic 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, RoleDiagnostic 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;
}
protected OperandRole getOperandRole() {
return OperandRole.SAME_FOCUS_ACTION;
}
/**
* Get the RoleLocator (used to construct error messages)
*
* @return the RoleLocator
*/
public RoleDiagnostic getRoleLocator() {
return role;
}
/**
* Simplify an expression
*
*/
/*@NotNull*/
public Expression simplify() throws XPathException {
Expression operand = getBaseExpression().simplify();
if (requiredItemType instanceof AnyItemType) {
return operand;
}
setBaseExpression(operand);
return this;
}
/**
* Type-check the expression
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
typeCheckChildren(visitor, contextInfo);
Expression operand = getBaseExpression();
// When typeCheck is called a second time, we might have more information...
final TypeHierarchy th = 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();
int relation = th.relationship(requiredItemType, supplied);
if (relation == TypeHierarchy.SAME_TYPE || relation == TypeHierarchy.SUBSUMES) {
return operand;
} else if (relation == TypeHierarchy.DISJOINT) {
if (Cardinality.allowsZero(card)) {
String message = role.composeErrorMessage(
requiredItemType, operand.getItemType());
visitor.getStaticContext().issueWarning("The only value that can pass type-checking is an empty sequence. " +
message, getLocation());
} 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());
XPathException err = new XPathException(message);
err.setErrorCode(role.getErrorCode());
err.setLocation(this.getLocation());
err.setIsTypeError(role.isTypeError());
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 | ITEM_FEED_METHOD;
if (!Cardinality.allowsMany(getCardinality())) {
m |= EVALUATE_METHOD;
}
return m;
}
/**
* For an expression that returns an integer or a sequence of integers, get
* a lower and upper bound on the values of the integers that may be returned, from
* static analysis. The default implementation returns null, meaning "unknown" or
* "not applicable". Other implementations return an array of two IntegerValue objects,
* representing the lower and upper bounds respectively. The values
* UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that
* the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH
* are used to indicate values limited by the size of a string or the size of a sequence.
*
* @return the lower and upper bounds of integer values in the result, or null to indicate
* unknown or not applicable.
*/
/*@Nullable*/
@Override
public IntegerValue[] getIntegerBounds() {
return getBaseExpression().getIntegerBounds();
}
/**
* Iterate over the sequence of values
*/
/*@NotNull*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
SequenceIterator base = getBaseExpression().iterate(context);
return new ItemMappingIterator(base, getMappingFunction(context), true);
}
/**
* Get the mapping function used to implement this item check. This mapping function is applied
* to each item in the input sequence.
*
* @param context The dynamic context used to evaluate the mapping function
* @return the mapping function. This will be an identity mapping: the output sequence is the same
* as the input sequence, unless the dynamic type checking reveals an error.
*/
public ItemMappingFunction getMappingFunction(XPathContext context) {
return new ItemTypeCheckingFunction- (requiredItemType, role, getLocation(), context.getConfiguration());
}
/**
* Evaluate as an Item.
*/
public Item evaluateItem(XPathContext context) throws XPathException {
final TypeHierarchy th = context.getConfiguration().getTypeHierarchy();
Item item = getBaseExpression().evaluateItem(context);
if (item == null) {
return null;
}
if (requiredItemType.matches(item, th)) {
return item;
} else if (requiredItemType.getUType().subsumes(UType.STRING) && BuiltInAtomicType.ANY_URI.matches(item, th)) {
return item;
} else {
String message = role.composeErrorMessage(requiredItemType, Type.getItemType(item, th));
String errorCode = role.getErrorCode();
if ("XPDY0050".equals(errorCode)) {
// error in "treat as" assertion
dynamicError(message, errorCode, context);
} else {
typeError(message, errorCode, context);
}
return null;
}
}
/**
* 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 = getBaseExpression();
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(out);
filter.setRequiredType(requiredItemType, card, role, getLocation());
context.setReceiver(filter);
next.process(context);
filter.close();
context.setReceiver(out);
} else {
super.process(context);
}
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
ItemChecker exp = new ItemChecker(getBaseExpression().copy(), requiredItemType, role);
ExpressionTool.copyLocationInfo(this, exp);
return exp;
}
/**
* Determine the data type of the items returned by the expression
*
*
* /*@NotNull
*/
public ItemType getItemType() {
ItemType operandType = getBaseExpression().getItemType();
TypeHierarchy th = getConfiguration().getTypeHierarchy();
int relationship = th.relationship(requiredItemType, operandType);
switch (relationship) {
case TypeHierarchy.OVERLAPS:
if (requiredItemType instanceof NodeTest && operandType instanceof NodeTest) {
return new CombinedNodeTest((NodeTest) requiredItemType, Token.INTERSECT, (NodeTest) operandType);
} else {
// we don't know how to intersect atomic types, it doesn't actually happen
return requiredItemType;
}
case TypeHierarchy.SUBSUMES:
case TypeHierarchy.SAME_TYPE:
// shouldn't happen, but it doesn't matter
return operandType;
case TypeHierarchy.SUBSUMED_BY:
default:
return requiredItemType;
}
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
requiredItemType == ((ItemChecker) other).requiredItemType;
}
/**
* get HashCode for comparing two expressions. Note that this hashcode gives the same
* result for (A op B) and for (B op A), whether or not the operator is commutative.
*/
@Override
public int hashCode() {
return super.hashCode() ^ requiredItemType.hashCode();
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void export(ExpressionPresenter out) {
out.startElement("treat", this);
out.emitAttribute("as", requiredItemType.toString());
out.emitAttribute("diag", role.save());
getBaseExpression().export(out);
out.endElement();
}
/**
* Get a name identifying the kind of expression, in terms meaningful to a user.
*
* @return a name identifying the kind of expression, in terms meaningful to a user.
* The name will always be in the form of a lexical XML QName, and should match the name used
* in explain() output displaying the expression.
*/
public String getExpressionName() {
return "TreatAs";
}
/**
* 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() {
String typeDesc = requiredItemType.toString();
return "(" + getBaseExpression().toString() + ") treat as " + typeDesc;
}
@Override
public String toShortString() {
return getBaseExpression().toShortString();
}
//project:preconditions
public Expression optimizeForType(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException {
Expression base = getBaseExpression();
if(base instanceof ContextItemExpression &&
requiredItemType.equals(contextItemType.getItemType())) {
return base;
}
return this;
}
}
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