package net.sf.saxon.expr;
import net.sf.saxon.Configuration;
import net.sf.saxon.om.*;
import net.sf.saxon.pattern.*;
import net.sf.saxon.sort.IntHashSet;
import net.sf.saxon.sort.IntIterator;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.*;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.EmptySequence;
import java.util.Iterator;
/**
* An AxisExpression is always obtained by simplifying a PathExpression.
* It represents a PathExpression that starts at the context node, and uses
* a simple node-test with no filters. For example "*", "title", "./item",
* "@*", or "ancestor::chapter*".
*
* <p>An AxisExpression delivers nodes in axis order (not in document order).
* To get nodes in document order, in the case of a reverse axis, the expression
* should be wrapped in a call on reverse().</p>
*/
public final class AxisExpression extends Expression {
private byte axis;
private NodeTest test;
private ItemType itemType = null;
private ItemType contextItemType = null;
int computedCardinality = -1;
private boolean doneWarnings = false;
/**
* Constructor
* @param axis The axis to be used in this AxisExpression: relevant constants are defined
* in class net.sf.saxon.om.Axis.
* @param nodeTest The conditions to be satisfied by selected nodes. May be null,
* indicating that any node on the axis is acceptable
* @see net.sf.saxon.om.Axis
*/
public AxisExpression(byte axis, NodeTest nodeTest) {
this.axis = axis;
test = nodeTest;
}
/**
* Simplify an expression
* @return the simplified expression
* @param visitor an expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) {
if (axis == Axis.PARENT && (test==null || test instanceof AnyNodeTest)) {
ParentNodeExpression p = new ParentNodeExpression();
ExpressionTool.copyLocationInfo(this, p);
return p;
}
return this;
}
/**
* Type-check the expression
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
Configuration config = visitor.getConfiguration();
NamePool namePool = config.getNamePool();
StaticContext env = visitor.getStaticContext();
if (contextItemType == null) {
XPathException err = new XPathException("Axis step " + toString(namePool) +
" cannot be used here: the context item is undefined");
err.setIsTypeError(true);
err.setErrorCode("XPDY0002");
err.setLocator(this);
throw err;
}
if (contextItemType.isAtomicType()) {
XPathException err = new XPathException("Axis step " + toString(namePool) +
" cannot be used here: the context item is an atomic value");
err.setIsTypeError(true);
err.setErrorCode("XPTY0020");
err.setLocator(this);
throw err;
}
if (this.contextItemType == contextItemType && doneWarnings) {
return this;
}
this.contextItemType = contextItemType;
doneWarnings = true;
if (contextItemType instanceof NodeTest) {
int origin = contextItemType.getPrimitiveType();
if (origin != Type.NODE) {
if (Axis.isAlwaysEmpty(axis, origin)) {
env.issueWarning("The " + Axis.axisName[axis] + " axis starting at " +
(origin==Type.ELEMENT || origin == Type.ATTRIBUTE ? "an " : "a ") +
NodeKindTest.nodeKindName(origin) + " node will never select anything",
this);
return Literal.makeEmptySequence();
}
}
if (test != null) {
int kind = test.getPrimitiveType();
if (kind != Type.NODE) {
if (!Axis.containsNodeKind(axis, kind)) {
env.issueWarning("The " + Axis.axisName[axis] + " axis will never select any " +
NodeKindTest.nodeKindName(kind) + " nodes",
this);
return Literal.makeEmptySequence();
}
}
if (axis==Axis.SELF && kind!=Type.NODE && origin!=Type.NODE && kind!=origin) {
env.issueWarning("The self axis will never select any " +
NodeKindTest.nodeKindName(kind) +
" nodes when starting at " +
(origin==Type.ELEMENT || origin == Type.ATTRIBUTE ? "an " : "a ") +
NodeKindTest.nodeKindName(origin) + " node", this);
return Literal.makeEmptySequence();
}
if (axis==Axis.SELF) {
itemType = new CombinedNodeTest((NodeTest)contextItemType, Token.INTERSECT, test);
}
// If the content type of the context item is known, see whether the node test can select anything
if (contextItemType instanceof DocumentNodeTest && axis == Axis.CHILD && kind == Type.ELEMENT) {
NodeTest elementTest = ((DocumentNodeTest)contextItemType).getElementTest();
IntHashSet requiredNames = elementTest.getRequiredNodeNames();
if (requiredNames != null) {
// check that the name appearing in the step is one of the names allowed by the nodetest
IntHashSet selected = test.getRequiredNodeNames();
if (selected != null && selected.intersect(requiredNames).isEmpty()) {
env.issueWarning("Starting at a document node, the step is selecting an element whose name " +
"is not among the names of child elements permitted for this document node type", this);
return Literal.makeEmptySequence();
}
}
itemType = elementTest;
return this;
}
SchemaType contentType = ((NodeTest)contextItemType).getContentType();
if (contentType == AnyType.getInstance()) {
// fast exit in non-schema-aware case
return this;
}
int targetfp = test.getFingerprint();
if (contentType.isSimpleType()) {
if ((axis == Axis.CHILD || axis==Axis.DESCENDANT || axis==Axis.DESCENDANT_OR_SELF) &&
(kind==Type.ELEMENT || kind==Type.ATTRIBUTE || kind==Type.DOCUMENT)) {
env.issueWarning("The " + Axis.axisName[axis] + " axis will never select any " +
NodeKindTest.nodeKindName(kind) +
" nodes when starting at a node with simple type " +
contentType.getDescription(), this);
} else if (axis == Axis.CHILD && kind == Type.TEXT &&
(visitor.getParentExpression() instanceof Atomizer)) {
env.issueWarning("Selecting the text nodes of an element with simple content may give the " +
"wrong answer in the presence of comments or processing instructions. It is usually " +
"better to omit the '/text()' step", this);
} else if (axis == Axis.ATTRIBUTE) {
Iterator extensions = config.getExtensionsOfType(contentType);
boolean found = false;
if (targetfp == -1) {
while (extensions.hasNext()) {
ComplexType extension = (ComplexType)extensions.next();
if (extension.allowsAttributes()) {
found = true;
break;
}
}
} else {
while (extensions.hasNext()) {
ComplexType extension = (ComplexType)extensions.next();
try {
if (extension.getAttributeUseType(targetfp) != null) {
found = true;
break;
}
} catch (SchemaException e) {
// ignore the error
}
}
}
if (!found) {
env.issueWarning("The " + Axis.axisName[axis] + " axis will never select " +
(targetfp == -1 ?
"any attribute nodes" :
"an attribute node named " + env.getNamePool().getDisplayName(targetfp)) +
" when starting at a node with simple type " +
contentType.getDescription(), this);
// Despite the warning, leave the expression unchanged. This is because
// we don't necessarily know about all extended types at compile time:
// in particular, we don't seal the XML Schema namespace to block extensions
// of built-in types
}
}
} else if (((ComplexType)contentType).isSimpleContent() &&
(axis==Axis.CHILD || axis==Axis.DESCENDANT || axis==Axis.DESCENDANT_OR_SELF) &&
(kind==Type.ELEMENT || kind==Type.DOCUMENT)) {
// We don't need to consider extended types here, because a type with complex content
// can never be defined as an extension of a type with simple content
env.issueWarning("The " + Axis.axisName[axis] + " axis will never select any " +
NodeKindTest.nodeKindName(kind) +
" nodes when starting at a node with type " +
contentType.getDescription() +
", as this type requires simple content", this);
return new Literal(EmptySequence.getInstance());
} else if (((ComplexType)contentType).isEmptyContent() &&
(axis==Axis.CHILD || axis==Axis.DESCENDANT || axis==Axis.DESCENDANT_OR_SELF)) {
for (Iterator iter=config.getExtensionsOfType(contentType); iter.hasNext();) {
ComplexType extension = (ComplexType)iter.next();
if (!extension.isEmptyContent()) {
return this;
}
}
env.issueWarning("The " + Axis.axisName[axis] + " axis will never select any" +
" nodes when starting at a node with type " +
contentType.getDescription() +
", as this type requires empty content", this);
return new Literal(EmptySequence.getInstance());
} else if (axis==Axis.ATTRIBUTE && targetfp != -1) {
try {
SchemaType schemaType = ((ComplexType)contentType).getAttributeUseType(targetfp);
if (schemaType == null) {
String n = env.getNamePool().getDisplayName(targetfp);
env.issueWarning("The complex type " + contentType.getDescription() +
" does not allow an attribute named " + n, this);
return new Literal(EmptySequence.getInstance());
} else {
itemType = new CombinedNodeTest(
test,
Token.INTERSECT,
new ContentTypeTest(Type.ATTRIBUTE, schemaType, env.getConfiguration()));
}
} catch (SchemaException e) {
// ignore the exception
}
} else if (axis==Axis.CHILD && kind==Type.ELEMENT) {
try {
int childElement = targetfp;
if (targetfp == -1) {
// select="child::*"
if (((ComplexType)contentType).containsElementWildcard()) {
return this;
}
IntHashSet children = new IntHashSet();
((ComplexType)contentType).gatherAllPermittedChildren(children);
if (children.isEmpty()) {
env.issueWarning("The complex type " + contentType.getDescription() +
" does not allow children", this);
return new Literal(EmptySequence.getInstance());
}
// if (children.contains(-1)) {
// return this;
// }
if (children.size() == 1) {
IntIterator iter = children.iterator();
if (iter.hasNext()) {
childElement = iter.next();
}
} else {
return this;
}
}
SchemaType schemaType = ((ComplexType)contentType).getElementParticleType(childElement, true);
if (schemaType == null) {
String n = env.getNamePool().getDisplayName(childElement);
env.issueWarning("The complex type " + contentType.getDescription() +
" does not allow a child element named " + n, this);
return new Literal(EmptySequence.getInstance());
} else {
itemType = new CombinedNodeTest(
test,
Token.INTERSECT,
new ContentTypeTest(Type.ELEMENT, schemaType, env.getConfiguration()));
computedCardinality = ((ComplexType)contentType).getElementParticleCardinality(childElement);
visitor.resetStaticProperties();
if (computedCardinality == StaticProperty.ALLOWS_ZERO) {
// this shouldn't happen, because we've already checked for this a different way.
// but it's worth being safe (there was a bug involving an incorrect inference here)
String n = env.getNamePool().getDisplayName(childElement);
env.issueWarning("The complex type " + contentType.getDescription() +
" appears not to allow a child element named " + n, this);
return new Literal(EmptySequence.getInstance());
}
if (!Cardinality.allowsMany(computedCardinality)) {
// if there can be at most one child of this name, create a FirstItemExpression
// to stop the search after the first one is found
return new FirstItemExpression(this);
}
}
} catch (SchemaException e) {
// ignore the exception
}
} else if (axis==Axis.DESCENDANT && kind==Type.ELEMENT && targetfp != -1) {
// when searching for a specific element on the descendant axis, try to produce a more
// specific path that avoids searching branches of the tree where the element cannot occur
try {
IntHashSet descendants = new IntHashSet();
((ComplexType)contentType).gatherAllPermittedDescendants(descendants);
if (descendants.contains(-1)) {
return this;
}
if (descendants.contains(targetfp)) {
IntHashSet children = new IntHashSet();
((ComplexType)contentType).gatherAllPermittedChildren(children);
IntHashSet usefulChildren = new IntHashSet();
boolean considerSelf = false;
boolean considerDescendants = false;
for (IntIterator child = children.iterator(); child.hasNext();) {
int c = child.next();
if (c == targetfp) {
usefulChildren.add(c);
considerSelf = true;
}
SchemaType st = ((ComplexType)contentType).getElementParticleType(c, true);
if (st == null) {
throw new AssertionError("Can't find type for element " + c);
}
if (st instanceof ComplexType) {
IntHashSet subDescendants = new IntHashSet();
((ComplexType)st).gatherAllPermittedDescendants(subDescendants);
if (subDescendants.contains(targetfp)) {
usefulChildren.add(c);
considerDescendants = true;
}
}
}
if (usefulChildren.size() < children.size()) {
NodeTest childTest = makeUnionNodeTest(usefulChildren, visitor.getConfiguration().getNamePool());
AxisExpression first = new AxisExpression(Axis.CHILD, childTest);
ExpressionTool.copyLocationInfo(this, first);
byte nextAxis;
if (considerSelf) {
nextAxis = (considerDescendants ? Axis.DESCENDANT_OR_SELF : Axis.SELF);
} else {
nextAxis = Axis.DESCENDANT;
}
AxisExpression next = new AxisExpression(nextAxis, test);
ExpressionTool.copyLocationInfo(this, next);
PathExpression path = new PathExpression(first, next);
ExpressionTool.copyLocationInfo(this, path);
return path.typeCheck(visitor, contextItemType);
}
} else {
String n = env.getNamePool().getDisplayName(targetfp);
env.issueWarning("The complex type " + contentType.getDescription() +
" does not allow a descendant element named " + n, this);
}
} catch (SchemaException e) {
throw new AssertionError(e);
}
}
}
}
return this;
}
/**
* Make a union node test for a set of supplied element fingerprints
* @param elements the set of integer element fingerprints to be tested for
* @param pool the name pool
* @return a NodeTest that returns true if the node is an element whose name is one of the names
* in this set
*/
private NodeTest makeUnionNodeTest(IntHashSet elements, NamePool pool) {
NodeTest test = null;
for (IntIterator iter = elements.iterator(); iter.hasNext();) {
int fp = iter.next();
NodeTest nextTest = new NameTest(Type.ELEMENT, fp, pool);
if (test == null) {
test = nextTest;
} else {
test = new CombinedNodeTest(test, Token.UNION, nextTest);
}
}
if (test == null) {
return EmptySequenceTest.getInstance();
} else {
return test;
}
}
/**
* Get the static type of the context item for this AxisExpression. May be null if not known.
* @return the statically-inferred type, or null if not known
*/
public ItemType getContextItemType() {
return contextItemType;
}
/**
* 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 net.sf.saxon.type.Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
*/
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) {
return this;
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
if (!(other instanceof AxisExpression)) {
return false;
}
if (axis != ((AxisExpression)other).axis) {
return false;
}
if (test==null) {
return ((AxisExpression)other).test==null;
}
return test.toString().equals(((AxisExpression)other).test.toString());
}
/**
* get HashCode for comparing two expressions
*/
public int hashCode() {
// generate an arbitrary hash code that depends on the axis and the node test
int h = 9375162 + axis<<20;
if (test != null) {
h ^= test.getPrimitiveType()<<16;
h ^= test.getFingerprint();
}
return h;
}
/**
* Determine which aspects of the context the expression depends on. The result is
* a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and
* XPathContext.CURRENT_NODE
*/
public int getIntrinsicDependencies() {
return StaticProperty.DEPENDS_ON_CONTEXT_ITEM;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
public Expression copy() {
AxisExpression a2 = new AxisExpression(axis, test);
a2.itemType = itemType;
a2.contextItemType = contextItemType;
a2.computedCardinality = computedCardinality;
return a2;
}
/**
* 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 StaticProperty.CONTEXT_DOCUMENT_NODESET |
StaticProperty.SINGLE_DOCUMENT_NODESET |
StaticProperty.NON_CREATIVE |
(Axis.isForwards[axis] ? StaticProperty.ORDERED_NODESET : StaticProperty.REVERSE_DOCUMENT_ORDER) |
(Axis.isPeerAxis[axis] ? StaticProperty.PEER_NODESET : 0) |
(Axis.isSubtreeAxis[axis] ? StaticProperty.SUBTREE_NODESET : 0) |
((axis==Axis.ATTRIBUTE || axis==Axis.NAMESPACE) ? StaticProperty.ATTRIBUTE_NS_NODESET : 0);
}
/**
* Determine the data type of the items returned by this expression
* @return Type.NODE or a subtype, based on the NodeTest in the axis step, plus
* information about the content type if this is known from schema analysis
* @param th the type hierarchy cache
*/
public final ItemType getItemType(TypeHierarchy th) {
if (itemType != null) {
return itemType;
}
int p = Axis.principalNodeType[axis];
switch (p) {
case Type.ATTRIBUTE:
case Type.NAMESPACE:
return NodeKindTest.makeNodeKindTest(p);
default:
if (test==null) {
return AnyNodeTest.getInstance();
} else {
return test;
//return NodeKindTest.makeNodeKindTest(test.getPrimitiveType());
}
}
}
/**
* Specify that the expression returns a singleton
*/
public final int computeCardinality() {
if (computedCardinality != -1) {
return computedCardinality;
}
if (axis == Axis.ATTRIBUTE && test instanceof NameTest) {
return StaticProperty.ALLOWS_ZERO_OR_ONE;
} else if (axis == Axis.SELF) {
return StaticProperty.ALLOWS_ZERO_OR_ONE;
} else {
return StaticProperty.ALLOWS_ZERO_OR_MORE;
}
// the parent axis isn't handled by this class
}
/**
* Determine whether the expression can be evaluated without reference to the part of the context
* document outside the subtree rooted at the context node.
* @return true if the expression has no dependencies on the context node, or if the only dependencies
* on the context node are downward selections using the self, child, descendant, attribute, and namespace
* axes.
*/
public boolean isSubtreeExpression() {
return Axis.isSubtreeAxis[axis];
}
/**
* Get the axis
* @return the axis number, for example {@link Axis#CHILD}
*/
public byte getAxis() {
return axis;
}
/**
* Get the NodeTest. Returns null if the AxisExpression can return any node.
* @return the node test, or null if all nodes are returned
*/
public NodeTest getNodeTest() {
return test;
}
/**
* 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.
*
* @param pathMap the PathMap to which the expression should be added
* @param pathMapNodeSet
* @return the pathMapNode representing the focus established by this expression, in the case where this
* expression is the first operand of a path expression or filter expression
*/
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) {
if (pathMapNodeSet == null) {
ContextItemExpression cie = new ContextItemExpression();
cie.setContainer(getContainer());
pathMapNodeSet = new PathMap.PathMapNodeSet(pathMap.makeNewRoot(cie));
}
PathMap.PathMapNodeSet target = pathMapNodeSet.createArc(this);
// if (isStringValueUsed()) {
// target.setAtomized();
// }
return target;
}
/**
* Evaluate the path-expression in a given context to return a NodeSet
* @param context the evaluation context
*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
Item item = context.getContextItem();
try {
if (test==null) {
return ((NodeInfo)item).iterateAxis(axis);
} else {
return ((NodeInfo)item).iterateAxis(axis, test);
}
} catch (NullPointerException npe) {
NamePool pool;
try {
pool = context.getConfiguration().getNamePool();
} catch (Exception err) {
pool = null;
}
XPathException err = new XPathException("The context item for axis step " +
(pool == null ? toString() : toString(pool)) + " is undefined");
err.setErrorCode("XPDY0002");
err.setXPathContext(context);
err.setLocator(this);
err.setIsTypeError(true);
throw err;
} catch (ClassCastException cce) {
NamePool pool;
try {
pool = context.getConfiguration().getNamePool();
} catch (Exception err) {
pool = null;
}
XPathException err = new XPathException("The context item for axis step " +
(pool == null ? toString() : toString(pool)) + " is not a node");
err.setErrorCode("XPTY0020");
err.setXPathContext(context);
err.setLocator(this);
err.setIsTypeError(true);
throw err;
} catch (UnsupportedOperationException err) {
// the namespace axis is not supported for all tree implementations
dynamicError(err.getMessage(), "XPST0010", context);
return null;
}
}
/**
* Iterate the axis from a given starting node, without regard to context
* @param origin the starting node
* @return the iterator over the axis
*/
public SequenceIterator iterate(Item origin) throws XPathException {
try {
if (test==null) {
return ((NodeInfo)origin).iterateAxis(axis);
} else {
return ((NodeInfo)origin).iterateAxis(axis, test);
}
} catch (ClassCastException cce) {
XPathException err = new XPathException("The context item for axis step " +
toString() + " is not a node");
err.setErrorCode("XPTY0020");
err.setLocator(this);
err.setIsTypeError(true);
throw err;
}
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter destination) {
destination.startElement("axis");
destination.emitAttribute("name", Axis.axisName[axis]);
destination.emitAttribute("nodeTest", (test==null ? "node()" : test.toString()));
destination.endElement();
}
/**
* Represent the expression as a string for diagnostics
*/
public String toString() {
return Axis.axisName[axis] +
"::" +
(test==null ? "node()" : test.toString());
}
/**
* Represent the expression as a string for diagnostics
* @param pool the name pool, used for expanding names in the node test
* @return a string representation of the expression
*/
public String toString(NamePool pool) {
return Axis.axisName[axis] +
"::" +
(test==null ? "node()" : test.toString(pool));
}
}
//
// 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.
//