net.sf.saxon.expr.Atomizer Maven / Gradle / Ivy
package net.sf.saxon.expr;
import net.sf.saxon.Configuration;
import net.sf.saxon.event.ReceiverOptions;
import net.sf.saxon.instruct.ValueOf;
import net.sf.saxon.om.*;
import net.sf.saxon.pattern.EmptySequenceTest;
import net.sf.saxon.pattern.NodeTest;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.*;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.Value;
/**
* 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; //set to true if it is known that the nodes being atomized will be untyped
private boolean singleValued; // set to true if all atomized nodes will atomize to a single atomic value
private Configuration config;
/**
* Constructor
* @param sequence the sequence to be atomized
* @param config the Configuration. Used only for optimization, may be null. Atomization is faster if
* it is known in advance that all nodes will be untyped.
*/
public Atomizer(Expression sequence, Configuration config) {
super(sequence);
this.config = config;
if (config != null) {
untyped = (config.areAllNodesUntyped());
computeSingleValued(config.getTypeHierarchy());
}
sequence.setFlattened(true);
}
/**
* Simplify an expression
* @param visitor an expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
config = visitor.getConfiguration();
untyped = config.areAllNodesUntyped();
operand = visitor.simplify(operand);
if (operand instanceof Literal) {
Value 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;
}
}
} else if (operand instanceof ValueOf && (((ValueOf)operand).getOptions()& ReceiverOptions.DISABLE_ESCAPING) == 0) {
// XSLT users tend to use ValueOf unnecessarily
return ((ValueOf)operand).convertToStringJoin(visitor.getStaticContext());
}
return this;
}
/**
* Type-check the expression
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
operand = visitor.typeCheck(operand, contextItemType);
// If the configuration allows typed data, check whether the content type of these particular nodes is untyped
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
computeSingleValued(th);
visitor.resetStaticProperties();
if (th.isSubType(operand.getItemType(th), BuiltInAtomicType.ANY_ATOMIC)) {
return operand;
}
operand.setFlattened(true);
return this;
}
private void computeSingleValued(TypeHierarchy th) {
singleValued = untyped;
if (!singleValued) {
ItemType nodeType = operand.getItemType(th);
if (nodeType instanceof NodeTest) {
SchemaType st = ((NodeTest)nodeType).getContentType();
if (st == AnyType.getInstance() || st.isAtomicType()) {
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 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 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)
*/
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
Expression exp = super.optimize(visitor, contextItemType);
if (exp == this) {
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
if (th.isSubType(operand.getItemType(th), BuiltInAtomicType.ANY_ATOMIC)) {
return operand;
}
if (operand instanceof ValueOf && (((ValueOf)operand).getOptions()& ReceiverOptions.DISABLE_ESCAPING) == 0) {
// XSLT users tend to use ValueOf unnecessarily
return ((ValueOf)operand).convertToStringJoin(visitor.getStaticContext());
}
}
return exp;
}
/**
* Determine the special properties of this expression
* @return {@link StaticProperty#NON_CREATIVE}.
*/
public int computeSpecialProperties() {
int p = super.computeSpecialProperties();
return p | StaticProperty.NON_CREATIVE;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
public Expression copy() {
return new Atomizer(getBaseExpression().copy(), config);
}
/**
* Iterate over the sequence of values
*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
SequenceIterator base = operand.iterate(context);
return getAtomizingIterator(base);
}
/**
* 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 Item evaluateItem(XPathContext context) throws XPathException {
Item i = operand.evaluateItem(context);
if (i==null) {
return null;
}
if (i instanceof NodeInfo) {
SequenceIterator it = i.getTypedValue();
return it.next();
} else {
return i;
}
}
/**
* 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.
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return getAtomizedItemType(operand, 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
*/
public static ItemType getAtomizedItemType(Expression operand, boolean alwaysUntyped, TypeHierarchy th) {
ItemType in = operand.getItemType(th);
if (in.isAtomicType()) {
return in;
}
if (in instanceof NodeTest) {
if (in instanceof EmptySequenceTest) {
return in;
}
int kinds = ((NodeTest)in).getNodeKindMask();
if (alwaysUntyped) {
// Some node-kinds always have a typed value that's a string
if ((kinds | STRING_KINDS) == STRING_KINDS) {
return BuiltInAtomicType.STRING;
}
// Some node-kinds are always untyped atomic; some are untypedAtomic provided that the configuration
// is untyped
if ((kinds | UNTYPED_IF_UNTYPED_KINDS) == UNTYPED_IF_UNTYPED_KINDS) {
return BuiltInAtomicType.UNTYPED_ATOMIC;
}
} else {
if ((kinds | UNTYPED_KINDS) == UNTYPED_KINDS) {
return BuiltInAtomicType.UNTYPED_ATOMIC;
}
}
return in.getAtomizedItemType();
}
return BuiltInAtomicType.ANY_ATOMIC;
}
/**
* Node kinds whose typed value is always a string
*/
private static final int STRING_KINDS =
(1<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 = operand.addToPathMap(pathMap, pathMapNodeSet);
if (result != null) {
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
* @return an iterator that returns atomic values, the result of the atomization
*/
public static SequenceIterator getAtomizingIterator(SequenceIterator base) {
if (base instanceof AxisIterator) {
return new AxisAtomizingIterator((AxisIterator)base);
}
return new MappingIterator(base, AtomizingFunction.getInstance());
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public String displayExpressionName() {
return "atomize";
}
/**
* 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 SequenceIterator map(Item item) throws XPathException {
if (item instanceof NodeInfo) {
return item.getTypedValue();
} else {
return SingletonIterator.makeIterator(item);
}
}
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//
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