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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 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.ExpressionTool;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.PromotionOffer;
import net.sf.saxon.expr.parser.Token;
import net.sf.saxon.expr.sort.AtomicComparer;
import net.sf.saxon.expr.sort.DoubleSortComparer;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.BooleanValue;
import net.sf.saxon.value.Int64Value;
import net.sf.saxon.value.NumericValue;
import java.util.Iterator;
import java.util.List;
/**
* This class implements a comparison of a numeric value to an integer constant using one of the operators
* eq, ne, lt, gt, le, ge. The semantics are identical to ValueComparison, but this is a fast path for an
* important common case.
*/
public class CompareToIntegerConstant extends Expression implements ComparisonExpression {
private Expression operand;
private long comparand;
private int operator;
/**
* Create the expression
* @param operand the operand to be compared with an integer constant. This must
* have a static type of NUMERIC, and a cardinality of EXACTLY ONE
* @param operator the comparison operator,
* one of {@link Token#FEQ}, {@link Token#FNE}, {@link Token#FGE},
* {@link Token#FGT}, {@link Token#FLE}, {@link Token#FLT}
* @param comparand the integer constant
*/
public CompareToIntegerConstant(Expression operand, int operator, long comparand) {
this.operand = operand;
this.operator = operator;
this.comparand = comparand;
adoptChildExpression(operand);
}
/**
* Get the expression on the lhs of the comparison
* @return the left hand operand
*/
public Expression getOperand() {
return operand;
}
/**
* Get the integer value on the rhs of the expression
* @return the integer constant
*/
public long getComparand() {
return comparand;
}
/**
* Get the comparison operator
* @return one of {@link Token#FEQ}, {@link Token#FNE}, {@link Token#FGE},
* {@link Token#FGT}, {@link Token#FLE}, {@link Token#FLT}
*/
public int getComparisonOperator() {
return operator;
}
/**
* 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 value {@link #EVALUATE_METHOD}
*/
public int getImplementationMethod() {
return EVALUATE_METHOD;
}
/**
* Simplify an expression. This performs any static optimization (by rewriting the expression
* as a different expression). The default implementation does nothing.
* @param visitor the expression visitor
* @return the simplified expression
* @throws XPathException
* if an error is discovered during expression
* rewriting
*/
/*@NotNull*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
operand = visitor.simplify(operand);
return this;
}
/**
* Offer promotion for this subexpression. The offer will be accepted if the subexpression
* is not dependent on the factors (e.g. the context item) identified in the PromotionOffer.
* By default the offer is not accepted - this is appropriate in the case of simple expressions
* such as constant values and variable references where promotion would give no performance
* advantage. This method is always called at compile time.
*
* @param offer details of the offer, for example the offer to move
* expressions that don't depend on the context to an outer level in
* the containing expression
* @param parent
* @return if the offer is not accepted, return this expression unchanged.
* Otherwise return the result of rewriting the expression to promote
* this subexpression
* @throws net.sf.saxon.trans.XPathException
* if any error is detected
*/
public Expression promote(PromotionOffer offer, Expression parent) throws XPathException {
Expression exp = offer.accept(parent, this);
if (exp != null) {
return exp;
} else {
operand = doPromotion(operand, offer);
return this;
}
}
public int computeSpecialProperties() {
return StaticProperty.NON_CREATIVE;
}
/**
* Compute the dependencies of an expression, as the union of the
* dependencies of its subexpressions. (This is overridden for path expressions
* and filter expressions, where the dependencies of a subexpression are not all
* propogated). This method should be called only once, to compute the dependencies;
* after that, getDependencies should be used.
*
* @return the depencies, as a bit-mask
*/
public int computeDependencies() {
return operand.getDependencies();
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
return new CompareToIntegerConstant(operand.copy(), operator, comparand);
}
/**
* Get the immediate sub-expressions of this expression. Default implementation
* returns a zero-length array, appropriate for an expression that has no
* sub-expressions.
*
* @return an iterator containing the sub-expressions of this expression
*/
/*@NotNull*/
public Iterator iterateSubExpressions() {
return new MonoIterator(operand);
}
/**
* Replace one subexpression by a replacement subexpression
*
* @param original the original subexpression
* @param replacement the replacement subexpression
* @return true if the original subexpression is found
*/
public boolean replaceSubExpression(Expression original, Expression replacement) {
if (original == operand) {
operand = replacement;
return true;
}
return false;
}
/**
* Evaluate an expression as a single item. This always returns either a single Item or
* null (denoting the empty sequence). No conversion is done. This method should not be
* used unless the static type of the expression is a subtype of "item" or "item?": that is,
* it should not be called if the expression may return a sequence. There is no guarantee that
* this condition will be detected.
*
* @param context The context in which the expression is to be evaluated
* @return the node or atomic value that results from evaluating the
* expression; or null to indicate that the result is an empty
* sequence
* @throws net.sf.saxon.trans.XPathException
* if any dynamic error occurs evaluating the
* expression
*/
public BooleanValue evaluateItem(XPathContext context) throws XPathException {
return BooleanValue.get(effectiveBooleanValue(context));
}
/**
* Get the effective boolean value of the expression. This returns false if the value
* is the empty sequence, a zero-length string, a number equal to zero, or the boolean
* false. Otherwise it returns true.
*
* @param context The context in which the expression is to be evaluated
* @return the effective boolean value
* @throws net.sf.saxon.trans.XPathException
* if any dynamic error occurs evaluating the
* expression
*/
public boolean effectiveBooleanValue(XPathContext context) throws XPathException {
NumericValue n = (NumericValue)operand.evaluateItem(context);
if (n.isNaN()) {
return (operator == Token.FNE);
}
int c = n.compareTo(comparand);
switch (operator) {
case Token.FEQ:
return c == 0;
case Token.FNE:
return c != 0;
case Token.FGT:
return c > 0;
case Token.FLT:
return c < 0;
case Token.FGE:
return c >= 0;
case Token.FLE:
return c <= 0;
default:
throw new UnsupportedOperationException("Unknown operator " + operator);
}
}
protected int computeCardinality() {
return StaticProperty.EXACTLY_ONE;
}
/**
* Perform type checking of an expression and its subexpressions. This is the second phase of
* static optimization.
*
* This checks statically that the operands of the expression have
* the correct type; if necessary it generates code to do run-time type checking or type
* conversion. A static type error is reported only if execution cannot possibly succeed, that
* is, if a run-time type error is inevitable. The call may return a modified form of the expression.
*
* This method is called after all references to functions and variables have been resolved
* to the declaration of the function or variable. However, the types of such functions and
* variables may not be accurately known if they have not been explicitly declared.
*
* If the implementation returns a value other than "this", then it is required to ensure that
* the parent pointer and location information in the returned expression have been set up correctly.
* It should not rely on the caller to do this, although for historical reasons many callers do so.
*
* @param visitor the 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 to perform necessary run-time type checks,
* and to perform other type-related optimizations
* @throws XPathException if an error is discovered during this phase
* (typically a type error)
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
operand = visitor.typeCheck(operand, contextItemType);
return this;
}
/**
* Perform optimisation of an expression and its subexpressions. This is the third and final
* phase of static optimization.
*
* 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 the 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 XPathException if an error is discovered during this phase
* (typically a type error)
*/
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
operand = visitor.optimize(operand, contextItemType);
if (operand instanceof Literal) {
Literal lit = Literal.makeLiteral(BooleanValue.get(effectiveBooleanValue(null)));
ExpressionTool.copyLocationInfo(this, lit);
return lit;
}
return this;
}
/**
* Determine the data type of the expression, if possible. All expression return
* sequences, in general; this method determines the type of the items within the
* sequence, assuming that (a) this is known in advance, and (b) it is the same for
* all items in the sequence.
*
* This method should always return a result, though it may be the best approximation
* that is available at the time.
*
* @param th the type hierarchy cache
* @return a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER,
* Type.NODE, or Type.ITEM (meaning not known at compile time)
*/
/*@NotNull*/
public ItemType getItemType(TypeHierarchy th) {
return BuiltInAtomicType.BOOLEAN;
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter destination) {
destination.startElement("compareToInteger");
destination.emitAttribute("op", Token.tokens[operator]);
destination.emitAttribute("value", comparand+"");
operand.explain(destination);
destination.endElement();
}
/**
* The toString() method for an expression attempts to give a representation of the expression
* in an XPath-like form.
*
* For subclasses of Expression that represent XPath expressions, the result should always be a string that
* parses as an XPath 3.0 expression
*
* @return a representation of the expression as a string
*/
@Override
public String toString() {
return ExpressionTool.parenthesize(operand) + " " +
Token.tokens[operator] + " " + comparand;
}
/**
* Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used
*/
public AtomicComparer getAtomicComparer() {
return DoubleSortComparer.getInstance();
// Note: this treats NaN=NaN as true, but it doesn't matter, because the rhs will never be NaN.
}
/**
* Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT,
* Token.FLE, Token.FGE
*/
public int getSingletonOperator() {
return operator;
}
/**
* Get the two operands of the comparison
* @return the two operands
*/
public Expression[] getOperands() {
return new Expression[] {operand, Literal.makeLiteral(Int64Value.makeIntegerValue(comparand))};
}
/**
* Determine whether untyped atomic values should be converted to the type of the other operand
*
* @return true if untyped values should be converted to the type of the other operand, false if they
* should be converted to strings.
*/
public boolean convertsUntypedToOther() {
return true;
}
}