net.sf.saxon.expr.Atomizer Maven / Gradle / Ivy
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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.expr.parser.*;
import net.sf.saxon.ma.arrays.ArrayItemType;
import net.sf.saxon.event.ReceiverOptions;
import net.sf.saxon.expr.instruct.Block;
import net.sf.saxon.expr.instruct.Choose;
import net.sf.saxon.expr.instruct.ValueOf;
import net.sf.saxon.om.*;
import net.sf.saxon.pattern.NodeKindTest;
import net.sf.saxon.pattern.NodeTest;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.*;
import net.sf.saxon.type.*;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.Cardinality;
import java.util.Map;
/**
* An Atomizer is an expression corresponding essentially to the fn:data() function: it
* maps a sequence by replacing nodes with their typed values
*/
public final class Atomizer extends UnaryExpression {
private boolean untyped = false; //set to true if it is known that the nodes being atomized will be untyped
private boolean singleValued = false; // set to true if all atomized nodes will atomize to a single atomic value
/*@Nullable*/ private ItemType operandItemType = null;
/**
* Constructor
*
* @param sequence the sequence to be atomized
*/
public Atomizer(Expression sequence) {
super(sequence);
sequence.setFlattened(true);
}
/**
* Make an atomizer with a given operand
*
* @param sequence the operand
* @return an Atomizer that atomizes the given operand, or another expression that returns the same result
*/
public static Expression makeAtomizer(Expression sequence) {
if (sequence instanceof Literal && ((Literal) sequence).getValue() instanceof AtomicSequence) {
return sequence;
} else {
return new Atomizer(sequence);
}
}
protected OperandRole getOperandRole() {
return OperandRole.ATOMIC_SEQUENCE;
}
/**
* 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}
*/
public int getImplementationMethod() {
return ITERATE_METHOD | WATCH_METHOD;
}
public ItemType getOperandItemType() {
if (operandItemType == null) {
operandItemType = getBaseExpression().getItemType();
}
return operandItemType;
}
/**
* Simplify an expression
*
*/
/*@NotNull*/
public Expression simplify() throws XPathException {
//untyped = !getContainer().getPackageData().isSchemaAware();
untyped = !getPackageData().isSchemaAware();
computeSingleValued(getConfiguration().getTypeHierarchy());
Expression operand = getBaseExpression().simplify();
if (operand instanceof Literal) {
GroundedValue val = ((Literal) operand).getValue();
if (val instanceof AtomicValue) {
return operand;
}
SequenceIterator iter = val.iterate();
while (true) {
// if all items in the sequence are atomic (they generally will be, since this is
// done at compile time), then return the sequence
Item i = iter.next();
if (i == null) {
return operand;
}
if (i instanceof NodeInfo) {
return this;
}
if (i instanceof Function) {
if (((Function)i).isArray()) {
return this;
} else {
XPathException err = new XPathException("Cannot atomize a function item", "FOTY0013");
err.setLocation(getLocation());
throw err;
}
}
}
} else if (operand instanceof ValueOf && (((ValueOf) operand).getOptions() & ReceiverOptions.DISABLE_ESCAPING) == 0) {
// XSLT users tend to use ValueOf unnecessarily
return ((ValueOf) operand).convertToCastAsString();
}
setBaseExpression(operand);
return this;
}
/**
* Type-check the expression
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
typeCheckChildren(visitor, contextInfo);
untyped = untyped | !visitor.getStaticContext().getPackageData().isSchemaAware();
// If the configuration allows typed data, check whether the content type of these particular nodes is untyped
final TypeHierarchy th = getConfiguration().getTypeHierarchy();
computeSingleValued(th);
resetLocalStaticProperties();
ItemType operandType = getOperandItemType();
if (th.isSubType(operandType, BuiltInAtomicType.ANY_ATOMIC)) {
return getBaseExpression();
}
if (!operandType.isAtomizable()) {
XPathException err;
if (operandType instanceof FunctionItemType) {
err = new XPathException(
"Cannot atomize a function item", "FOTY0013");
} else {
err = new XPathException(
"Cannot atomize an element that is defined in the schema to have element-only content", "FOTY0012");
}
err.setIsTypeError(true);
err.setLocation(getLocation());
throw err;
}
getBaseExpression().setFlattened(true);
return this;
}
private void computeSingleValued(TypeHierarchy th) {
ItemType operandType = getOperandItemType();
if (th.relationship(operandType, ArrayItemType.ANY_ARRAY_TYPE) != TypeHierarchy.DISJOINT) {
singleValued = false;
} else {
singleValued = untyped;
if (!singleValued) {
ItemType nodeType = getBaseExpression().getItemType();
if (nodeType instanceof NodeTest) {
SchemaType st = ((NodeTest) nodeType).getContentType();
if (st == Untyped.getInstance() || st.isAtomicType() || (st.isComplexType() && st != AnyType.getInstance())) {
singleValued = true;
}
if (!nodeType.getUType().overlaps(UType.ELEMENT.union(UType.ATTRIBUTE))) {
singleValued = true;
}
}
}
}
}
/**
* 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 net.sf.saxon.trans.XPathException
* if an error is discovered during this phase
* (typically a type error)
*/
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
Expression exp = super.optimize(visitor, contextInfo);
if (exp == this) {
final TypeHierarchy th = getConfiguration().getTypeHierarchy();
Expression operand = getBaseExpression();
if (th.isSubType(operand.getItemType(), BuiltInAtomicType.ANY_ATOMIC)) {
return operand;
}
if (operand instanceof ValueOf && (((ValueOf) operand).getOptions() & ReceiverOptions.DISABLE_ESCAPING) == 0) {
// XSLT users tend to use ValueOf unnecessarily
Expression cast = ((ValueOf) operand).convertToCastAsString();
return cast.optimize(visitor, contextInfo);
}
if (operand instanceof LetExpression || operand instanceof ForExpression) {
// replace data(let $x := y return z) by (let $x := y return data(z))
Expression action = ((Assignation) operand).getAction();
((Assignation) operand).setAction(new Atomizer(action));
return operand.optimize(visitor, contextInfo);
}
if (operand instanceof Choose) {
// replace data(if x then y else z) by (if x then data(y) else data(z)
((Choose)operand).atomizeActions();
return operand.optimize(visitor, contextInfo);
}
if (operand instanceof Block) {
// replace data((x,y,z)) by (data(x), data(y), data(z)) as some of the atomizers
// may prove to be redundant. (Also, it helps streaming)
Operand[] children = ((Block) operand).getOperanda();
Expression[] atomizedChildren = new Expression[children.length];
for (int i = 0; i < children.length; i++) {
atomizedChildren[i] = new Atomizer(children[i].getChildExpression());
}
Block newBlock = new Block(atomizedChildren);
return newBlock.typeCheck(visitor, contextInfo).optimize(visitor, contextInfo);
}
}
return exp;
}
/**
* Ask whether it is known that any nodes in the input will always be untyped
*
* @return true if it is known that all nodes in the input will be untyped
*/
public boolean isUntyped() {
return untyped;
}
/**
* Determine the special properties of this expression
*
* @return {@link StaticProperty#NON_CREATIVE}.
*/
public int computeSpecialProperties() {
int p = super.computeSpecialProperties();
p &= ~StaticProperty.NODESET_PROPERTIES;
return p | StaticProperty.NON_CREATIVE;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
* @param rebindings
*/
/*@NotNull*/
public Expression copy(RebindingMap rebindings) {
Atomizer copy = new Atomizer(getBaseExpression().copy(rebindings));
copy.untyped = untyped;
copy.singleValued = singleValued;
ExpressionTool.copyLocationInfo(this, copy);
return copy;
}
/**
* Iterate over the sequence of values
*/
/*@NotNull*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
SequenceIterator base = getBaseExpression().iterate(context);
return getAtomizingIterator(base, untyped);
}
/**
* Evaluate as an Item. This should only be called if the Atomizer has cardinality zero-or-one,
* which will only be the case if the underlying expression has cardinality zero-or-one.
*/
public AtomicValue evaluateItem(XPathContext context) throws XPathException {
Item i = getBaseExpression().evaluateItem(context);
if (i == null) {
return null;
} else {
return i.atomize().head();
}
}
/**
* Determine the data type of the items returned by the expression, if possible
*
* @return a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER. For this class, the
* result is always an atomic type, but it might be more specific.
*/
/*@NotNull*/
public ItemType getItemType() {
operandItemType = getBaseExpression().getItemType();
TypeHierarchy th = getConfiguration().getTypeHierarchy();
return getAtomizedItemType(getBaseExpression(), untyped, th);
}
/**
* Compute the type that will result from atomizing the result of a given expression
*
* @param operand the given expression
* @param alwaysUntyped true if it is known that nodes will always be untyped
* @param th the type hierarchy cache
* @return the item type of the result of evaluating the operand expression, after atomization, or
* xs:error if it is known that atomization will return an error
*/
public static ItemType getAtomizedItemType(Expression operand, boolean alwaysUntyped, TypeHierarchy th) {
ItemType in = operand.getItemType();
if (in.isPlainType()) {
return in;
} else if (in instanceof NodeTest) {
UType kinds = in.getUType();
if (alwaysUntyped) {
// Some node-kinds always have a typed value that's a string
if (STRING_KINDS.subsumes(kinds)) {
return BuiltInAtomicType.STRING;
}
// Some node-kinds are always untyped atomic; some are untypedAtomic provided that the configuration
// is untyped
if (UNTYPED_IF_UNTYPED_KINDS.subsumes(kinds)) {
return BuiltInAtomicType.UNTYPED_ATOMIC;
}
} else {
if (UNTYPED_KINDS.subsumes(kinds)) {
return BuiltInAtomicType.UNTYPED_ATOMIC;
}
}
return in.getAtomizedItemType();
} else if (in instanceof JavaExternalObjectType) {
return in.getAtomizedItemType();
} else if (in instanceof ArrayItemType) {
return ((ArrayItemType)in).getMemberType().getPrimaryType().getAtomizedItemType();
} else if (in instanceof FunctionItemType) {
return ErrorType.getInstance();
}
return BuiltInAtomicType.ANY_ATOMIC;
}
/**
* Node kinds whose typed value is always a string
*/
public static final UType STRING_KINDS =
UType.NAMESPACE.union(UType.COMMENT).union(UType.PI);
/**
* Node kinds whose typed value is always untypedAtomic
*/
public static final UType UNTYPED_KINDS =
UType.TEXT.union(UType.DOCUMENT);
/**
* Node kinds whose typed value is untypedAtomic if the configuration is untyped
*/
public static final UType UNTYPED_IF_UNTYPED_KINDS =
UType.TEXT.union(UType.ELEMENT).union(UType.DOCUMENT).union(UType.ATTRIBUTE);
/**
* Determine the static cardinality of the expression
*/
public int computeCardinality() {
ItemType in = getOperandItemType();
Expression operand = getBaseExpression();
if (singleValued) {
return operand.getCardinality();
} else if (untyped && in instanceof NodeTest) {
return operand.getCardinality();
} else if (Cardinality.allowsMany(operand.getCardinality())) {
return StaticProperty.ALLOWS_ZERO_OR_MORE;
} else if (in.isPlainType()) {
return operand.getCardinality();
} else if (in instanceof NodeTest) {
SchemaType schemaType = ((NodeTest) in).getContentType();
if (schemaType.isAtomicType()) {
// can return at most one atomic value per node
return operand.getCardinality();
}
}
return StaticProperty.ALLOWS_ZERO_OR_MORE;
}
/**
* Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited
* by an expression in a source tree.
*
* The default implementation of this method assumes that an expression does no navigation other than
* the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the
* same context as the containing expression. The method must be overridden for any expression
* where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression,
* and RootExpression (because they perform navigation), and for the doc(), document(), and collection()
* functions because they create a new navigation root. Implementations also exist for PathExpression and
* FilterExpression because they have subexpressions that are evaluated in a different context from the
* calling expression.
*
* @param pathMap the PathMap to which the expression should be added
* @param pathMapNodeSet the PathMapNodeSet to which the paths embodied in this expression should be added
* @return the pathMapNodeSet representing the points in the source document that are both reachable by this
* expression, and that represent possible results of this expression. For an expression that does
* navigation, it represents the end of the arc in the path map that describes the navigation route. For other
* expressions, it is the same as the input pathMapNode.
*/
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) {
PathMap.PathMapNodeSet result = getBaseExpression().addToPathMap(pathMap, pathMapNodeSet);
if (result != null) {
TypeHierarchy th = getConfiguration().getTypeHierarchy();
ItemType operandItemType = getBaseExpression().getItemType();
if (th.relationship(NodeKindTest.ELEMENT, operandItemType) != TypeHierarchy.DISJOINT ||
th.relationship(NodeKindTest.DOCUMENT, operandItemType) != TypeHierarchy.DISJOINT) {
result.setAtomized();
}
}
return null;
}
/**
* Get an iterator that returns the result of atomizing the sequence delivered by the supplied
* iterator
*
* @param base the supplied iterator, the input to atomization
* @param untyped this can safely be set to true if it is known that all nodes in the base sequence will
* be untyped; but it is always OK to set it to false.
* @return an iterator that returns atomic values, the result of the atomization
* @throws net.sf.saxon.trans.XPathException
* if a dynamic evaluation error occurs
*/
public static SequenceIterator getAtomizingIterator(SequenceIterator base, boolean untyped) throws XPathException {
int properties = base.getProperties();
if ((properties & SequenceIterator.LAST_POSITION_FINDER) != 0) {
int count = ((LastPositionFinder) base).getLength();
if (count == 0) {
return EmptyIterator.emptyIterator();
} else if (count == 1) {
Item first = base.next();
return first.atomize().iterate();
}
} else if ((properties & SequenceIterator.ATOMIZING) != 0) {
return new AxisAtomizingIterator((AtomizedValueIterator)base);
}
if (untyped) {
return new UntypedAtomizingIterator(base);
} else {
return new AtomizingIterator(base);
}
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public String getExpressionName() {
return "data";
}
/**
* 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
*/
@Override
public String toString() {
return "data(" + getBaseExpression().toString() + ")";
}
@Override
public String toShortString() {
return getBaseExpression().toShortString();
}
/**
* Implement the mapping function. This is stateless, so there is a singleton instance.
*/
public static class AtomizingFunction implements MappingFunction {
/**
* Private constructor, ensuring that everyone uses the singleton instance
*/
private AtomizingFunction() {
}
private static final AtomizingFunction theInstance = new AtomizingFunction();
/**
* Get the singleton instance
*
* @return the singleton instance of this mapping function
*/
public static AtomizingFunction getInstance() {
return theInstance;
}
public AtomicIterator map(Item item) throws XPathException {
if (item instanceof NodeInfo) {
return ((NodeInfo) item).atomize().iterate();
} else if (item instanceof AtomicValue) {
return new SingleAtomicIterator((AtomicValue)item);
} else {
throw new XPathException("Cannot atomize a function item or external object", "FOTY0013");
}
}
}
}
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