package org.pdf4j.saxon.expr;
import org.pdf4j.saxon.om.Item;
import org.pdf4j.saxon.om.NodeInfo;
import org.pdf4j.saxon.sort.GlobalOrderComparer;
import org.pdf4j.saxon.trans.XPathException;
import org.pdf4j.saxon.type.BuiltInAtomicType;
import org.pdf4j.saxon.type.ItemType;
import org.pdf4j.saxon.type.TypeHierarchy;
import org.pdf4j.saxon.value.BooleanValue;
import org.pdf4j.saxon.value.SequenceType;
/**
* IdentityComparison: a boolean expression that compares two nodes
* for equals, not-equals, greater-than or less-than based on identity and
* document ordering
*/
public final class IdentityComparison extends BinaryExpression {
private boolean generateIdEmulation = false;
// this flag is set if an "X is Y" or "X isnot Y" comparison is being used
// to emulate generate-id(X) = / != generate-id(Y). The handling of an empty
// sequence in the two cases is different.
/**
* Create an identity comparison identifying the two operands and the operator
* @param p1 the left-hand operand
* @param op the operator, as a token returned by the Tokenizer (e.g. Token.LT)
* @param p2 the right-hand operand
*/
public IdentityComparison(Expression p1, int op, Expression p2) {
super(p1, op, p2);
}
/**
* Set flag to indicate different empty-sequence behavior when emulating
* comparison of two generate-id's
* @param flag true if this function is being used to compare generate-id() output
*/
public void setGenerateIdEmulation(boolean flag) {
generateIdEmulation = flag;
}
/**
* Test the flag that indicates different empty-sequence behavior when emulating
* comparison of two generate-id's
* @return true if this function is being used to compare generate-id() output
*/
public boolean isGenerateIdEmulation() {
return generateIdEmulation;
}
/**
* Type-check the expression
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
operand0 = visitor.typeCheck(operand0, contextItemType);
operand1 = visitor.typeCheck(operand1, contextItemType);
if (!generateIdEmulation) {
if (Literal.isEmptySequence(operand0) || Literal.isEmptySequence(operand1)) {
return Literal.makeEmptySequence();
}
}
RoleLocator role0 = new RoleLocator(RoleLocator.BINARY_EXPR, Token.tokens[operator], 0);
//role0.setSourceLocator(this);
operand0 = TypeChecker.staticTypeCheck(
operand0, SequenceType.OPTIONAL_NODE, false, role0, visitor);
RoleLocator role1 = new RoleLocator(RoleLocator.BINARY_EXPR, Token.tokens[operator], 1);
//role1.setSourceLocator(this);
operand1 = TypeChecker.staticTypeCheck(
operand1, SequenceType.OPTIONAL_NODE, false, role1, visitor);
return this;
}
/**
* 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 org.pdf4j.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)
*/
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
Expression r = super.optimize(visitor, contextItemType);
if (r != this) {
if (!generateIdEmulation) {
if (Literal.isEmptySequence(operand0) || Literal.isEmptySequence(operand1)) {
return Literal.makeEmptySequence();
}
}
}
return r;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
public Expression copy() {
return new IdentityComparison(operand0.copy(), operator, operand1.copy());
}
/**
* Evaluate the expression
*/
public Item evaluateItem(XPathContext context) throws XPathException {
NodeInfo node1 = getNode(operand0, context);
if (node1==null) {
if (generateIdEmulation) {
return BooleanValue.get(getNode(operand1, context)==null);
}
return null;
}
NodeInfo node2 = getNode(operand1, context);
if (node2==null) {
if (generateIdEmulation) {
return BooleanValue.FALSE;
}
return null;
}
return BooleanValue.get(compareIdentity(node1, node2));
}
public boolean effectiveBooleanValue(XPathContext context) throws XPathException {
NodeInfo node1 = getNode(operand0, context);
if (node1==null) {
return generateIdEmulation && getNode(operand1, context) == null;
}
NodeInfo node2 = getNode(operand1, context);
return node2 != null && compareIdentity(node1, node2);
}
private boolean compareIdentity(NodeInfo node1, NodeInfo node2) {
switch (operator) {
case Token.IS:
return node1.isSameNodeInfo(node2);
case Token.PRECEDES:
return GlobalOrderComparer.getInstance().compare(node1, node2) < 0;
case Token.FOLLOWS:
return GlobalOrderComparer.getInstance().compare(node1, node2) > 0;
default:
throw new UnsupportedOperationException("Unknown node identity test");
}
}
private NodeInfo getNode(Expression exp, XPathContext c) throws XPathException {
return (NodeInfo)exp.evaluateItem(c);
}
/**
* Determine the data type of the expression
* @return Type.BOOLEAN
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return BuiltInAtomicType.BOOLEAN;
}
}
//
// 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.
//