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The XSLT and XQuery Processor
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2020 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.Configuration;
import net.sf.saxon.expr.instruct.Block;
import net.sf.saxon.expr.parser.ContextItemStaticInfo;
import net.sf.saxon.expr.parser.ExpressionTool;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.RebindingMap;
import net.sf.saxon.ma.arrays.ArrayItem;
import net.sf.saxon.ma.arrays.ArrayItemType;
import net.sf.saxon.ma.arrays.SquareArrayConstructor;
import net.sf.saxon.ma.map.KeyValuePair;
import net.sf.saxon.ma.map.MapItem;
import net.sf.saxon.ma.map.MapType;
import net.sf.saxon.ma.map.TupleType;
import net.sf.saxon.om.GroundedValue;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/**
* A lookup expression is an expression of the form A?*, where A must be a map or an array
*/
public class LookupAllExpression extends UnaryExpression {
/**
* Constructor
*
* @param base The left hand operand (which must always select a sequence of maps or arrays).
*/
public LookupAllExpression(Expression base) {
super(base);
}
@Override
protected OperandRole getOperandRole() {
return OperandRole.INSPECT;
}
/**
* Determine the data type of the items returned by this expression
*
* @return the type of the step
*/
/*@NotNull*/
@Override
public final ItemType getItemType() {
ItemType base = getBaseExpression().getItemType();
if (base instanceof MapType) {
return ((MapType)base).getValueType().getPrimaryType();
} else if (base instanceof ArrayItemType) {
return ((ArrayItemType) base).getMemberType().getPrimaryType();
} else {
return AnyItemType.getInstance();
}
}
/**
* Get the static type of the expression as a UType, following precisely the type
* inference rules defined in the XSLT 3.0 specification.
*
* @return the static item type of the expression according to the XSLT 3.0 defined rules
* @param contextItemType The type of the context item (not used)
*/
@Override
public UType getStaticUType(UType contextItemType) {
return getItemType().getUType();
}
/**
* Type-check the expression
*/
/*@NotNull*/
@Override
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
Configuration config = visitor.getConfiguration();
TypeHierarchy th = config.getTypeHierarchy();
// Check the first operand
getOperand().typeCheck(visitor, contextInfo);
ItemType containerType = getBaseExpression().getItemType();
boolean isArrayLookup = containerType instanceof ArrayItemType;
boolean isMapLookup = containerType instanceof MapType || containerType instanceof TupleType;
if (!isArrayLookup && !isMapLookup) {
if (th.relationship(containerType, MapType.ANY_MAP_TYPE) == Affinity.DISJOINT &&
th.relationship(containerType, ArrayItemType.getInstance()) == Affinity.DISJOINT) {
XPathException err = new XPathException("The left-hand operand of '?' must be a map or an array; the supplied expression is of type " + containerType, "XPTY0004");
err.setLocation(getLocation());
err.setIsTypeError(true);
err.setFailingExpression(this);
throw err;
}
}
if (getBaseExpression() instanceof Literal) {
return new Literal(iterate(visitor.makeDynamicContext()).materialize());
}
return this;
}
@Override
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException {
getOperand().optimize(visitor, contextItemType);
if (getBaseExpression() instanceof Literal) {
return new Literal(iterate(visitor.makeDynamicContext()).materialize());
}
// See W3C bug 30228. In the interests of keeping certain tests streamable, we do a rewrite of [A,B,C]?*
// to (A, B, C).
if (getBaseExpression() instanceof SquareArrayConstructor) {
List children = new ArrayList<>();
for (Operand o : getBaseExpression().operands()) {
children.add(o.getChildExpression().copy(new RebindingMap()));
}
Expression[] childExpressions = children.toArray(new Expression[0]);
Block block = new Block(childExpressions);
ExpressionTool.copyLocationInfo(this, block);
return block;
}
return this;
}
/**
* Return the estimated cost of evaluating an expression. This is a very crude measure based
* on the syntactic form of the expression (we have no knowledge of data values). We take
* the cost of evaluating a simple scalar comparison or arithmetic expression as 1 (one),
* and we assume that a sequence has length 5. The resulting estimates may be used, for
* example, to reorder the predicates in a filter expression so cheaper predicates are
* evaluated first.
* @return a rough estimate of the cost of evaluation
*/
@Override
public double getCost() {
return getBaseExpression().getCost() + 1;
}
/**
* 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;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
* @param rebindings variables that need to be re-bound.
*/
/*@NotNull*/
@Override
public LookupAllExpression copy(RebindingMap rebindings) {
return new LookupAllExpression(getBaseExpression().copy(rebindings));
}
/**
* Determine the static cardinality of the expression
*/
@Override
public int computeCardinality() {
return StaticProperty.ALLOWS_ZERO_OR_MORE;
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
if (!(other instanceof LookupAllExpression)) {
return false;
}
LookupAllExpression p = (LookupAllExpression) other;
return getBaseExpression().isEqual(p.getBaseExpression());
}
/**
* get HashCode for comparing two expressions
*/
@Override
public int computeHashCode() {
return "LookupAll".hashCode() ^ getBaseExpression().hashCode();
}
/**
* Iterate the lookup-expression in a given context
*
* @param context the evaluation context
*/
/*@NotNull*/
@Override
public SequenceIterator iterate(final XPathContext context) throws XPathException {
return new SequenceIterator() {
final SequenceIterator level0 = getBaseExpression().iterate(context);
Iterator level1 = null;
// delivers GroundedValue in the case of an array, or KeyValuePair in the case of a map
SequenceIterator level2 = null;
@Override
public Item next() throws XPathException {
if (level2 == null) {
if (level1 == null) {
Item base = level0.next();
if (base == null) {
return null;
} else if (base instanceof ArrayItem) {
level1 = ((ArrayItem)base).members().iterator();
return next();
} else if (base instanceof MapItem) {
level1 = ((MapItem)base).keyValuePairs().iterator();
return next();
} else {
LookupExpression.mustBeArrayOrMap(LookupAllExpression.this, base);
return null;
}
} else {
if (level1.hasNext()) {
Object nextEntry = level1.next();
if (nextEntry instanceof KeyValuePair) {
GroundedValue value = ((KeyValuePair)nextEntry).value;
level2 = value.iterate();
} else if (nextEntry instanceof GroundedValue) {
level2 = ((GroundedValue) nextEntry).iterate();
} else {
throw new IllegalStateException();
}
} else {
level1 = null;
}
return next();
}
} else {
Item next = level2.next();
if (next == null) {
level2 = null;
return next();
} else {
return next;
}
}
}
@Override
public void close() {
if (level0 != null) {
level0.close();
}
if (level2 != null) {
level2.close();
}
}
};
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
@Override
public void export(ExpressionPresenter destination) throws XPathException {
destination.startElement("lookupAll", this);
getBaseExpression().export(destination);
destination.endElement();
}
/**
* 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
*
* @return a representation of the expression as a string
*/
public String toString() {
return ExpressionTool.parenthesize(getBaseExpression()) + "?*";
}
@Override
public String toShortString() {
return getBaseExpression().toShortString() + "?*";
}
}
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