package client.net.sf.saxon.ce.expr;
import client.net.sf.saxon.ce.om.Item;
import client.net.sf.saxon.ce.om.SequenceIterator;
import client.net.sf.saxon.ce.trans.Err;
import client.net.sf.saxon.ce.trans.XPathException;
import client.net.sf.saxon.ce.tree.util.FastStringBuffer;
import client.net.sf.saxon.ce.type.ItemType;
import client.net.sf.saxon.ce.type.TypeHierarchy;
import client.net.sf.saxon.ce.value.Cardinality;
/**
* A CardinalityChecker implements the cardinality checking of "treat as": that is,
* it returns the supplied sequence, checking that its cardinality is correct
*/
public final class CardinalityChecker extends UnaryExpression {
private int requiredCardinality = -1;
private RoleLocator role;
/**
* Private Constructor: use factory method
* @param sequence the base sequence whose cardinality is to be checked
* @param cardinality the required cardinality
* @param role information to be used in error reporting
*/
private CardinalityChecker(Expression sequence, int cardinality, RoleLocator role) {
super(sequence);
requiredCardinality = cardinality;
this.role = role;
computeStaticProperties();
adoptChildExpression(sequence);
}
/**
* Factory method to construct a CardinalityChecker. The method may create an expression that combines
* the cardinality checking with the functionality of the underlying expression class
* @param sequence the base sequence whose cardinality is to be checked
* @param cardinality the required cardinality
* @param role information to be used in error reporting
* @return a new Expression that does the CardinalityChecking (not necessarily a CardinalityChecker)
*/
public static Expression makeCardinalityChecker(Expression sequence, int cardinality, RoleLocator role) {
Expression result = new CardinalityChecker(sequence, cardinality, role);
ExpressionTool.copyLocationInfo(sequence, result);
return result;
}
/**
* Get the required cardinality
* @return the cardinality required by this checker
*/
public int getRequiredCardinality() {
return requiredCardinality;
}
/**
* Type-check the expression
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
operand = visitor.typeCheck(operand, contextItemType);
if (requiredCardinality == StaticProperty.ALLOWS_ZERO_OR_MORE ||
Cardinality.subsumes(requiredCardinality, operand.getCardinality())) {
return operand;
}
return this;
}
/**
* Perform optimisation of an expression and its subexpressions.
* <p/>
* <p>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.</p>
*
* @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 client.net.sf.saxon.ce.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)
*/
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
operand = visitor.optimize(operand, contextItemType);
if (requiredCardinality == StaticProperty.ALLOWS_ZERO_OR_MORE ||
Cardinality.subsumes(requiredCardinality, operand.getCardinality())) {
return operand;
}
return this;
}
/**
* Set the error code to be returned (this is used when evaluating the functions such
* as exactly-one() which have their own error codes)
* @param code the error code to be used
*/
public void setErrorCode(String code) {
role.setErrorCode(code);
}
/**
* Get the RoleLocator, which contains diagnostic information for use if the cardinality check fails
* @return the diagnostic information
*/
public RoleLocator getRoleLocator() {
return role;
}
/**
* 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;
if (!Cardinality.allowsMany(requiredCardinality)) {
m |= EVALUATE_METHOD;
}
return m;
}
/**
* Iterate over the sequence of values
*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
SequenceIterator base = operand.iterate(context);
// If the base iterator knows how many items there are, then check it now rather than wasting time
if ((base.getProperties() & SequenceIterator.LAST_POSITION_FINDER) != 0) {
int count = ((LastPositionFinder)base).getLastPosition();
if (count == 0 && !Cardinality.allowsZero(requiredCardinality)) {
typeError("An empty sequence is not allowed as the " +
role.getMessage(), role.getErrorCode(), context);
} else if (count == 1 && requiredCardinality == StaticProperty.EMPTY) {
typeError("The only value allowed for the " +
role.getMessage() + " is an empty sequence", role.getErrorCode(), context);
} else if (count > 1 && !Cardinality.allowsMany(requiredCardinality)) {
typeError("A sequence of more than one item is not allowed as the " +
role.getMessage() + depictSequenceStart(base.getAnother(), 2),
role.getErrorCode(), context);
}
return base;
}
// Otherwise return an iterator that does the checking on the fly
return new CardinalityCheckingIterator(base, requiredCardinality, role, getSourceLocator());
}
/**
* Show the first couple of items in a sequence in an error message
* @param seq iterator over the sequence
* @param max maximum number of items to be shown
* @return a message display of the contents of the sequence
*/
public static String depictSequenceStart(SequenceIterator seq, int max) {
try {
FastStringBuffer sb = new FastStringBuffer(FastStringBuffer.SMALL);
int count = 0;
sb.append(" (");
while (true) {
Item next = seq.next();
if (next == null) {
sb.append(") ");
return sb.toString();
}
if (count++ > 0) {
sb.append(", ");
}
if (count > max) {
sb.append("...) ");
return sb.toString();
}
sb.append(Err.depict(next));
}
} catch (XPathException e) {
return "";
}
}
/**
* Evaluate as an Item.
*/
public Item evaluateItem(XPathContext context) throws XPathException {
SequenceIterator iter = operand.iterate(context);
Item item = null;
while (true) {
Item nextItem = iter.next();
if (nextItem == null) break;
if (requiredCardinality == StaticProperty.EMPTY) {
typeError("An empty sequence is required as the " +
role.getMessage(), role.getErrorCode(), context);
return null;
}
if (item != null) {
typeError("A sequence of more than one item is not allowed as the " +
role.getMessage() + depictSequenceStart(iter.getAnother(), 2), role.getErrorCode(), context);
return null;
}
item = nextItem;
}
if (item == null && !Cardinality.allowsZero(requiredCardinality)) {
typeError("An empty sequence is not allowed as the " +
role.getMessage(), role.getErrorCode(), context);
return null;
}
return item;
}
/**
* Determine the data type of the items returned by the expression, if possible
* @return a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE,
* or Type.ITEM (meaning not known in advance)
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return operand.getItemType(th);
}
/**
* Determine the static cardinality of the expression
*/
public int computeCardinality() {
return requiredCardinality;
}
/**
* Get the static properties of this expression (other than its type). The result is
* bit-signficant. These properties are used for optimizations. In general, if
* property bit is set, it is true, but if it is unset, the value is unknown.
*/
public int computeSpecialProperties() {
return operand.getSpecialProperties();
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
requiredCardinality == ((CardinalityChecker)other).requiredCardinality;
}
/**
* 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() ^ requiredCardinality;
}
}
// 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.