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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 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.Outputter;
import net.sf.saxon.event.TypeCheckingFilter;
import net.sf.saxon.expr.elab.Elaborator;
import net.sf.saxon.expr.elab.PullElaborator;
import net.sf.saxon.expr.elab.PullEvaluator;
import net.sf.saxon.expr.elab.PushEvaluator;
import net.sf.saxon.expr.instruct.TailCall;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.om.SequenceTool;
import net.sf.saxon.pattern.DocumentNodeTest;
import net.sf.saxon.s9api.Location;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.Err;
import net.sf.saxon.trans.UncheckedXPathException;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.TwoItemIterator;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.Type;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.IntegerValue;
import java.util.function.Supplier;
/**
* 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 final Supplier roleSupplier;
/**
* 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, Supplier role) {
super(sequence);
requiredCardinality = cardinality;
this.roleSupplier = 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 roleSupplier 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, Supplier roleSupplier) {
Expression result;
if (sequence instanceof Literal && Cardinality.subsumes(cardinality, SequenceTool.getCardinality(((Literal) sequence).getGroundedValue()))) {
return sequence;
}
if (sequence instanceof Atomizer && !Cardinality.allowsMany(cardinality)) {
Expression base = ((Atomizer) sequence).getBaseExpression();
result = new SingletonAtomizer(base, roleSupplier, Cardinality.allowsZero(cardinality));
} else {
result = new CardinalityChecker(sequence, cardinality, roleSupplier);
}
ExpressionTool.copyLocationInfo(sequence, result);
return result;
}
@Override
protected OperandRole getOperandRole() {
return OperandRole.SAME_FOCUS_ACTION;
}
/**
* Get the required cardinality
*
* @return the cardinality required by this checker
*/
public int getRequiredCardinality() {
return requiredCardinality;
}
/**
* Type-check the expression
*/
/*@NotNull*/
@Override
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
getOperand().typeCheck(visitor, contextInfo);
Expression base = getBaseExpression();
if (requiredCardinality == StaticProperty.ALLOWS_ZERO_OR_MORE ||
Cardinality.subsumes(requiredCardinality, base.getCardinality())) {
return base;
}
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 XPathException if an error is discovered during this phase
* (typically a type error)
*/
/*@NotNull*/
@Override
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
getOperand().optimize(visitor, contextInfo);
Expression base = getBaseExpression();
if (requiredCardinality == StaticProperty.ALLOWS_ZERO_OR_MORE ||
Cardinality.subsumes(requiredCardinality, base.getCardinality())) {
return base;
}
if ((base.getCardinality() & requiredCardinality) == 0) {
RoleDiagnostic role = roleSupplier.get();
throw new XPathException("The " + role.getMessage() +
" does not satisfy the cardinality constraints", role.getErrorCode())
.withLocation(getLocation())
.asTypeErrorIf(role.isTypeError());
}
// do cardinality checking before item checking (may avoid the need for a mapping iterator)
if (base instanceof ItemChecker) {
ItemChecker checker = (ItemChecker) base;
Expression other = checker.getBaseExpression();
// change this -> checker -> other to checker -> this -> other
setBaseExpression(other);
checker.setBaseExpression(this);
checker.setParentExpression(null);
return checker;
}
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) {
// roleSupplier.setErrorCode(code);
// }
/**
* Get the RoleLocator, which contains diagnostic information for use if the cardinality check fails
*
* @return the diagnostic information
*/
public RoleDiagnostic getRoleLocator() {
return roleSupplier.get();
}
public Supplier getRoleSupplier() {
return roleSupplier;
}
/**
* 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.
*/
@Override
public int getImplementationMethod() {
int m = ITERATE_METHOD | PROCESS_METHOD | ITEM_FEED_METHOD;
if (!Cardinality.allowsMany(requiredCardinality)) {
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.
*/
@Override
public IntegerValue[] getIntegerBounds() {
return getBaseExpression().getIntegerBounds();
}
/**
* Iterate over the sequence of values
*/
/*@NotNull*/
@Override
public SequenceIterator iterate(XPathContext context) throws XPathException {
SequenceIterator base = getBaseExpression().iterate(context);
return checkCardinality(base, context);
}
public SequenceIterator checkCardinality(SequenceIterator base, XPathContext context) throws XPathException {
// If the base iterator knows how many items there are, then check it now rather than wasting time
if (SequenceTool.supportsGetLength(base)) {
int count = SequenceTool.getLength(base);
if (count == 0 && !Cardinality.allowsZero(requiredCardinality)) {
RoleDiagnostic role = roleSupplier.get();
typeError("An empty sequence is not allowed as the " +
role.getMessage(), role.getErrorCode(), context);
} else if (count == 1 && requiredCardinality == StaticProperty.EMPTY) {
RoleDiagnostic role = roleSupplier.get();
typeError("The only value allowed for the " +
role.getMessage() + " is an empty sequence", role.getErrorCode(), context);
} else if (count > 1 && !Cardinality.allowsMany(requiredCardinality)) {
RoleDiagnostic role = roleSupplier.get();
typeError("A sequence of more than one item is not allowed as the " +
role.getMessage() + depictSequenceStart(base, 2),
role.getErrorCode(), context);
}
return base;
}
// Otherwise return an iterator that does the checking on the fly
try {
return new CardinalityCheckingIterator(base, requiredCardinality, roleSupplier, getLocation());
} catch (XPathException e) {
throw e.maybeWithContext(context);
}
}
/**
* 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) {
StringBuilder sb = new StringBuilder(64);
int count = 0;
sb.append(" (");
Item next;
while ((next = seq.next()) != null) {
if (count++ > 0) {
sb.append(", ");
}
if (count > max) {
sb.append("...) ");
return sb.toString();
}
sb.append(Err.depict(next));
}
sb.append(") ");
return sb.toString();
}
/**
* Evaluate as an Item. For this class, this implies checking that the underlying
* expression delivers a singleton.
*/
/*@Nullable*/
@Override
public Item evaluateItem(XPathContext context) throws XPathException {
try {
SequenceIterator iter = getBaseExpression().iterate(context);
Item first = iter.next();
if (first == null) {
if (!Cardinality.allowsZero(requiredCardinality)) {
RoleDiagnostic role = roleSupplier.get();
typeError("An empty sequence is not allowed as the " +
role.getMessage(), role.getErrorCode(), context);
}
return null;
} else {
if (requiredCardinality == StaticProperty.EMPTY) {
RoleDiagnostic role = roleSupplier.get();
typeError("An empty sequence is required as the " +
role.getMessage(), role.getErrorCode(), context);
return null;
}
Item second = iter.next();
if (second != null) {
RoleDiagnostic role = roleSupplier.get();
typeError("A sequence of more than one item is not allowed as the " +
role.getMessage() + depictSequenceStart(
new TwoItemIterator(first, second), 2), role.getErrorCode(), context);
return null;
}
}
return first;
} catch (UncheckedXPathException e) {
throw e.getXPathException();
}
}
/**
* Process the instruction, without returning any tail calls
*
* @param output the destination for the result
* @param context The dynamic context, giving access to the current node,
*/
@Override
public void process(Outputter output, XPathContext context) throws XPathException {
PushEvaluator pusher = makeElaborator().elaborateForPush();
TailCall tc = pusher.processLeavingTail(output, context);
Expression.dispatchTailCall(tc);
}
/**
* 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)
*/
/*@NotNull*/
@Override
public ItemType getItemType() {
return getBaseExpression().getItemType();
}
/**
* Determine the static cardinality of the expression
*/
@Override
protected 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.
*/
@Override
protected int computeSpecialProperties() {
return getBaseExpression().getSpecialProperties();
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
* @param rebindings variable bindings that need to be changed
*/
/*@NotNull*/
@Override
public Expression copy(RebindingMap rebindings) {
CardinalityChecker c2 = new CardinalityChecker(getBaseExpression().copy(rebindings), requiredCardinality, roleSupplier);
ExpressionTool.copyLocationInfo(this, c2);
return c2;
}
/**
* 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
protected int computeHashCode() {
return super.computeHashCode() ^ requiredCardinality;
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
@Override
public void export(ExpressionPresenter out) throws XPathException {
out.startElement("check", this);
String occ = Cardinality.getOccurrenceIndicator(requiredCardinality);
if (occ.equals("")) {
occ = "1";
}
out.emitAttribute("card", occ);
out.emitAttribute("diag", roleSupplier.get().save());
getBaseExpression().export(out);
out.endElement();
}
/**
* The toString() method for an expression attempts to give a representation of the expression
* in an XPath-like form. For subclasses of Expression that represent XPath expressions, the result should always
* be a string that parses as an XPath 3.0 expression.
*/
@Override
public String toString() {
Expression operand = getBaseExpression();
switch (requiredCardinality) {
case StaticProperty.ALLOWS_ONE:
return "exactly-one(" + operand + ")";
case StaticProperty.ALLOWS_ZERO_OR_ONE:
return "zero-or-one(" + operand + ")";
case StaticProperty.ALLOWS_ONE_OR_MORE:
return "one-or-more(" + operand + ")";
case StaticProperty.EMPTY:
return "must-be-empty(" + operand + ")";
default:
return "check(" + operand + ")";
}
}
/**
* 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.
*/
@Override
public String getExpressionName() {
return "CheckCardinality";
}
@Override
public String toShortString() {
return getBaseExpression().toShortString();
}
@Override
public String getStreamerName() {
return "CardinalityChecker";
}
@Override
public void setLocation(Location id) {
super.setLocation(id);
}
/**
* Make an elaborator for this expression
*
* @return a suitable elaborator
*/
@Override
public Elaborator getElaborator() {
return new CardinalityCheckerElaborator();
}
/**
* Elaborator for a {@code treat as} expression, which is usually system-generated by
* the type checking phase of the compiler
*/
public static class CardinalityCheckerElaborator extends PullElaborator {
@Override
public PullEvaluator elaborateForPull() {
CardinalityChecker expr = (CardinalityChecker) getExpression();
Expression arg = expr.getBaseExpression();
PullEvaluator argEval = arg.makeElaborator().elaborateForPull();
return context -> expr.checkCardinality(argEval.iterate(context), context);
}
@Override
public PushEvaluator elaborateForPush() {
CardinalityChecker expr = (CardinalityChecker) getExpression();
Expression next = expr.getBaseExpression();
ItemType type = Type.ITEM_TYPE;
if (next instanceof ItemChecker) {
type = ((ItemChecker) next).getRequiredType();
next = ((ItemChecker) next).getBaseExpression();
}
if ((next.getImplementationMethod() & PROCESS_METHOD) != 0 && !(type instanceof DocumentNodeTest)) {
ItemType finalType = type;
PushEvaluator pushEval = next.makeElaborator().elaborateForPush();
return (output, context) -> {
TypeCheckingFilter filter = new TypeCheckingFilter(output);
filter.setRequiredType(finalType, expr.requiredCardinality, expr.roleSupplier.get(), expr.getLocation());
TailCall tc = pushEval.processLeavingTail(filter, context);
Expression.dispatchTailCall(tc);
try {
filter.finalCheck();
} catch (XPathException e) {
throw e.maybeWithLocation(expr.getLocation());
}
return null;
};
} else {
// Force pull-mode evaluation
PullEvaluator argEval = next.makeElaborator().elaborateForPull();
return (output, context) -> {
SequenceIterator iter = expr.checkCardinality(argEval.iterate(context), context);
for (Item item; (item = iter.next()) != null;) {
output.append(item);
}
return null;
};
}
}
}
}
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