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The XSLT and XQuery Processor
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 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.parser;
import net.sf.saxon.Configuration;
import net.sf.saxon.Controller;
import net.sf.saxon.event.ComplexContentOutputter;
import net.sf.saxon.event.SequenceCollector;
import net.sf.saxon.expr.*;
import net.sf.saxon.expr.flwor.Clause;
import net.sf.saxon.expr.flwor.FLWORExpression;
import net.sf.saxon.expr.flwor.LocalVariableBinding;
import net.sf.saxon.expr.instruct.*;
import net.sf.saxon.expr.sort.ConditionalSorter;
import net.sf.saxon.expr.sort.DocumentSorter;
import net.sf.saxon.functions.*;
import net.sf.saxon.functions.hof.UserFunctionReference;
import net.sf.saxon.lib.Logger;
import net.sf.saxon.lib.NamespaceConstant;
import net.sf.saxon.lib.StandardLogger;
import net.sf.saxon.om.*;
import net.sf.saxon.pattern.Pattern;
import net.sf.saxon.str.StringView;
import net.sf.saxon.style.Compilation;
import net.sf.saxon.style.ScopedBindingElement;
import net.sf.saxon.trans.Err;
import net.sf.saxon.trans.NoDynamicContextException;
import net.sf.saxon.trans.SymbolicName;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.transpile.CSharpSuppressWarnings;
import net.sf.saxon.type.AnyItemType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.value.*;
import javax.xml.transform.SourceLocator;
import java.io.File;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.Iterator;
import java.util.List;
import java.util.function.Predicate;
/**
* This class, ExpressionTool, contains a number of useful static methods
* for manipulating expressions. Most importantly, it provides the factory
* method make() for constructing a new expression
*/
public class ExpressionTool {
private ExpressionTool() {
}
/**
* Parse an XPath expression. This performs the basic analysis of the expression against the
* grammar, it binds variable references and function calls to variable definitions and
* function definitions, and it performs context-independent expression rewriting for
* optimization purposes.
*
* @param expression The expression (as a character string)
* @param env An object giving information about the compile-time
* context of the expression
* @param start position of the first significant character in the expression
* @param terminator The token that marks the end of this expression; typically
* Token.EOF, but may for example be a right curly brace
* @param codeInjector true allows injection of tracing, debugging, or performance monitoring code; null if
* not required
* @return an object of type Expression
* @throws XPathException if the expression contains a static error
*/
/*@NotNull*/
public static Expression make(String expression, StaticContext env,
int start, int terminator,
CodeInjector codeInjector) throws XPathException {
int languageLevel = env.getXPathVersion();
XPathParser parser = env.getConfiguration().newExpressionParser("XP", false, languageLevel);
if (codeInjector != null) {
parser.setCodeInjector(codeInjector);
}
if (terminator == -1) {
terminator = Token.EOF;
}
Expression exp = parser.parse(expression, start, terminator, env);
// TODO: parser.parse() already sets the retained static context
setDeepRetainedStaticContext(exp, env.makeRetainedStaticContext());
exp = exp.simplify();
return exp;
}
/**
* Ensure that every node in the expression tree has a retained static context.
* A node that already has a retained static context will propagate it to its children.
*
* @param exp the root of the expression tree
* @param rsc the retained static context to be applied to nodes that do not already have one,
* and that do not have an ancestor with an existing retained static context.
*/
public static void setDeepRetainedStaticContext(Expression exp, RetainedStaticContext rsc) {
if (exp.getLocalRetainedStaticContext() == null) {
exp.setRetainedStaticContextLocally(rsc);
} else {
rsc = exp.getLocalRetainedStaticContext();
}
for (Operand o : exp.operands()) {
setDeepRetainedStaticContext(o.getChildExpression(), rsc);
}
}
/**
* Copy location information (the line number and reference to the container) from one expression
* to another
*
* @param from the expression containing the location information
* @param to the expression to which the information is to be copied
*/
public static void copyLocationInfo(Expression from, Expression to) {
if (from != null && to != null) {
if (to.getLocation() == null || to.getLocation() == Loc.NONE) {
to.setLocation(from.getLocation());
}
if (to.getLocalRetainedStaticContext() == null) {
to.setRetainedStaticContextLocally(from.getLocalRetainedStaticContext());
}
}
}
/**
* Remove unwanted sorting from an expression, at compile time, if and only if it is known
* that the result of the expression will be homogeneous (all nodes, or all atomic values).
* This is done when we need the effective boolean value of a sequence: the EBV of a
* homogenous sequence does not depend on its order, but this is not true when atomic
* values and nodes are mixed: (N, AV) is true, but (AV, N) is an error.
*
* @param exp the expression to be optimized
* @param forStreaming true if streamed evaluation of the expression is required
* @return the expression after rewriting
* @throws net.sf.saxon.trans.XPathException if a static error is found while doing the rewrite
*/
public static Expression unsortedIfHomogeneous(Expression exp, boolean forStreaming)
throws XPathException {
if (exp instanceof Literal) {
return exp; // fast exit
}
if (exp.getItemType() instanceof AnyItemType) {
return exp;
} else {
return exp.unordered(false, forStreaming);
}
}
/**
* Inject extra code into an expression, recursively, by applying a supplied {@link CodeInjector}
* to every expression (and FLWOR clause) in the subtree
*
* @param exp the expression to be augmented with injected code
* @param injector the code injector
* @return the augmented expression
*/
public static Expression injectCode(Expression exp, CodeInjector injector) {
if (exp instanceof FLWORExpression) {
((FLWORExpression) exp).injectCode(injector);
} else if (exp instanceof TraceExpression) {
for (Operand o : ((TraceExpression) exp).getChild().operands()) {
if (!o.getOperandRole().isConstrainedClass()) {
o.setChildExpression(injectCode(o.getChildExpression(), injector));
}
}
} else {
for (Operand o : exp.operands()) {
if (!o.getOperandRole().isConstrainedClass()) {
o.setChildExpression(injectCode(o.getChildExpression(), injector));
}
}
}
return injector.inject(exp);
}
/**
* Get an expression evaluator to be used when lazy evaluation of an expression is
* preferred. This method is called at compile time, after all optimizations have been done,
* to determine the preferred strategy for lazy evaluation, depending on the type of expression.
*
* @param exp the expression to be evaluated
* @param repeatable true if the returned value needs to be readable more than once
* @return an expression evaluator
*/
public static Evaluator lazyEvaluator(Expression exp, boolean repeatable) {
if (exp instanceof Literal) {
return Evaluator.Literal.INSTANCE;
} else if (exp instanceof VariableReference) {
return Evaluator.Variable.INSTANCE;
} else if (exp instanceof SuppliedParameterReference) {
return Evaluator.SuppliedParameter.INSTANCE;
} else if ((exp.getDependencies() &
(StaticProperty.DEPENDS_ON_POSITION |
StaticProperty.DEPENDS_ON_LAST |
StaticProperty.DEPENDS_ON_CURRENT_ITEM |
StaticProperty.DEPENDS_ON_CURRENT_GROUP |
StaticProperty.DEPENDS_ON_REGEX_GROUP)) != 0) {
// we can't save these values in the closure, so we evaluate
// the expression now if they are needed
return eagerEvaluator(exp);
} else if (exp instanceof ErrorExpression) {
return Evaluator.SingleItem.INSTANCE;
// evaluateItem() on an error expression throws the latent exception
} else if (!Cardinality.allowsMany(exp.getCardinality())) {
// singleton expressions are always evaluated eagerly
return eagerEvaluator(exp);
} else if (exp instanceof TailExpression) {
// Treat tail recursion as a special case, to avoid creating a deeply-nested
// tree of Closures.
TailExpression tail = (TailExpression) exp;
Expression base = tail.getBaseExpression();
if (base instanceof VariableReference) {
return Evaluator.LazyTail.INSTANCE;
} else if (repeatable) {
return Evaluator.MemoClosureEvaluator.INSTANCE;
} else {
return Evaluator.LazySequence.INSTANCE;
}
} else if (exp instanceof Block && ((Block) exp).isCandidateForSharedAppend()) {
// If the expression is a Block, that is, it is appending a value to a sequence,
// then we have the opportunity to use a shared list underpinning the old value and
// the new. This takes precedence over lazy evaluation (it would be possible to do this
// lazily, but more difficult). We currently do this for any Block that has a variable
// reference as one of its subexpressions. The most common case is that the first argument is a reference
// to an argument of recursive function, where the recursive function returns the result of
// appending to the sequence.
return Evaluator.SharedAppend.INSTANCE;
} else if (repeatable) {
// create a Closure, a wrapper for the expression and its context
return Evaluator.MemoClosureEvaluator.INSTANCE;
} else {
return Evaluator.LazySequence.INSTANCE;
}
}
/**
* Get the evaluator to be used when eager evaluation of an expression is
* preferred. This method is called at compile time, after all optimizations have been done,
* to determine the preferred strategy for lazy evaluation, depending on the type of expression.
*
* @param exp the expression to be evaluated
* @return an integer constant identifying the evaluation mode
*/
public static Evaluator eagerEvaluator(Expression exp) {
if (exp instanceof Literal && !(((Literal) exp).getGroundedValue() instanceof Closure)) {
return Evaluator.Literal.INSTANCE;
}
if (exp instanceof VariableReference) {
return Evaluator.Variable.INSTANCE;
}
int m = exp.getImplementationMethod();
if ((m & Expression.EVALUATE_METHOD) != 0 && !Cardinality.allowsMany(exp.getCardinality())) {
if (Cardinality.allowsZero(exp.getCardinality())) {
return Evaluator.OptionalItem.INSTANCE;
} else {
return Evaluator.SingleItem.INSTANCE;
}
} else if ((m & Expression.ITERATE_METHOD) != 0) {
return Evaluator.EagerSequence.INSTANCE;
} else {
return Evaluator.Process.INSTANCE;
}
}
/**
* Do lazy evaluation of an expression. This will return a value, which may optionally
* be a SequenceIntent, which is a wrapper around an iterator over the value of the expression.
*
* @param exp the expression to be evaluated
* @param context the run-time evaluation context for the expression. If
* the expression is not evaluated immediately, then parts of the
* context on which the expression depends need to be saved as part of
* the Closure
* @param repeatable an indication of how the value will be used. The value false indicates that the value
* is only expected to be used once, so that there is no need to keep it in memory. The value true
* indicates multiple references, so the value will be saved when first evaluated.
* @return a value: either the actual value obtained by evaluating the
* expression, or a Closure containing all the information needed to
* evaluate it later
* @throws XPathException if any error occurs in evaluating the
* expression
*/
public static Sequence lazyEvaluate(Expression exp, XPathContext context, boolean repeatable) throws XPathException {
Evaluator evaluator = lazyEvaluator(exp, repeatable);
return evaluator.evaluate(exp, context);
}
/**
* Evaluate an expression now; lazy evaluation is not permitted in this case
*
* @param exp the expression to be evaluated
* @param context the run-time evaluation context
* @return the result of evaluating the expression
* @throws net.sf.saxon.trans.XPathException if any dynamic error occurs evaluating the
* expression
*/
public static GroundedValue eagerEvaluate(Expression exp, XPathContext context) throws XPathException {
Evaluator evaluator = eagerEvaluator(exp);
return evaluator.evaluate(exp, context).materialize();
}
/**
* Scan an expression to find and mark any recursive tail function calls
*
* @param exp the expression to be analyzed
* @param qName the name of the containing function
* @param arity the arity of the containing function
* @return 0 if no tail call was found; 1 if a tail call to a different function was found;
* 2 if a tail call to the specified function was found. In this case the
* UserFunctionCall object representing the tail function call will also have been marked as
* a tail call.
*/
public static int markTailFunctionCalls(Expression exp, StructuredQName qName, int arity) {
return exp.markTailFunctionCalls(qName, arity);
}
/**
* Construct indent string, for diagnostic output
*
* @param level the indentation level (the number of spaces to return)
* @return a string of "level*2" spaces
*/
public static String indent(int level) {
StringBuilder fsb = new StringBuilder(level);
for (int i = 0; i < level; i++) {
fsb.append(" ");
}
return fsb.toString();
}
/**
* Ask whether one expression is a subexpression of another
*
* @param a the containing expression
* @param b the putative contained expression
* @return true if and only if b is a subexpression (at some level) of a
*/
public static boolean contains(Expression a, Expression b) {
Expression temp = b;
while (temp != null) {
if (temp == a) {
return true;
} else {
temp = temp.getParentExpression();
}
}
return false;
}
/**
* Determine whether an expression contains a LocalParamSetter subexpression
*
* @param exp the expression to be tested
* @return true if the exprssion contains a local parameter setter
*/
public static boolean containsLocalParam(Expression exp) {
return contains(exp, true, e -> e instanceof LocalParam);
}
/**
* Determine whether an expression contains a local variable reference,
* other than a reference to a local variable whose binding occurs
* within this expression
*
* @param exp the expression to be tested
* @return true if the expression contains a local variable reference to a local
* variable declared outside this expression.
*/
public static boolean containsLocalVariableReference(final Expression exp) {
return contains(exp, false, e -> {
if (e instanceof LocalVariableReference) {
LocalVariableReference vref = (LocalVariableReference) e;
LocalBinding binding = vref.getBinding();
return !(binding instanceof Expression && contains(exp, (Expression) binding));
}
return false;
});
}
/**
* Test whether a given expression is, or contains, at any depth, an expression that satisfies a supplied
* condition
*
* @param exp the given expression
* @param sameFocusOnly if true, only subexpressions evaluated in the same focus are searched. If false,
* all subexpressions are searched
* @param predicate the condition to be satisfied
* @return true if the given expression is or contains an expression that satisfies the condition.
*/
public static boolean contains(Expression exp, boolean sameFocusOnly, Predicate predicate) {
if (predicate.test(exp)) {
return true;
}
for (Operand info : exp.operands()) {
if ((info.hasSameFocus() || !sameFocusOnly) && contains(info.getChildExpression(), sameFocusOnly, predicate)) {
return true;
}
}
return false;
}
/**
* Determine whether an expression possible calls (directly or indirectly) xsl:result-document, or
* has other context dependencies that prevent function inlining,
* which we assume is true if it contains a template call.
* A call on result-document disqualifies the function from being
* inlined, because error XTDE1480 would then not be detected. We don't have to worry about functions
* containing further function calls because they are disqualified from inlining anyway.
*
* @param exp the expression to be tested
* @return true if there is any possibility that calling the function might result in a call on
* xsl:result-document
*/
public static boolean changesXsltContext(Expression exp) {
exp = exp.getInterpretedExpression();
if (exp instanceof ResultDocument || exp instanceof CallTemplate || exp instanceof ApplyTemplates ||
exp instanceof NextMatch || exp instanceof ApplyImports || exp.isCallOn(RegexGroup.class)
|| exp.isCallOn(CurrentGroup.class)) {
return true;
}
for (Operand o : exp.operands()) {
if (changesXsltContext(o.getChildExpression())) {
return true;
}
}
return false;
}
/**
* Return true if a given expression is evaluated repeatedly
* when a given ancestor expression is evaluated once
*
* @param child the expression to be tested
* @param ancestor the ancestor expression. May be null, in which case the search goes all the way
* to the base of the stack.
* @return true if the current expression is evaluated repeatedly
*/
public static boolean isLoopingSubexpression(Expression child, Expression ancestor) {
while (true) {
Expression parent = child.getParentExpression();
if (parent == null) {
return false;
}
if (hasLoopingSubexpression(parent, child)) {
return true;
}
if (parent == ancestor) {
return false;
}
child = parent;
}
}
public static boolean isLoopingReference(VariableReference reference, Binding binding) {
Expression child = reference;
Expression parent = child.getParentExpression();
while (true) {
if (parent == null) {
// haven't found the binding on the stack, so the safe thing is to assume we're in a loop
return true;
}
if (parent instanceof FLWORExpression) {
if (parent.hasVariableBinding(binding)) {
// The variable is declared in one of the clauses of the FLWOR expression
return ((FLWORExpression) parent).hasLoopingVariableReference(binding);
} else {
// The variable is declared outside the FLWOR expression
if (hasLoopingSubexpression(parent, child)) {
return true;
}
}
} else if (parent.getExpressionName().equals("tryCatch")) {
return true; // not actually a loop, but it's a simple way to prevent inlining of variables (test QT3 try-007)
} else {
if (parent instanceof ForEachGroup && parent.hasVariableBinding(binding)) {
return false;
}
if (hasLoopingSubexpression(parent, child)) {
return true;
}
if (parent.hasVariableBinding(binding)) {
return false;
}
}
child = parent;
parent = child.getParentExpression();
}
}
public static boolean hasLoopingSubexpression(Expression parent, Expression child) {
for (Operand info : parent.operands()) {
if (info.getChildExpression() == child) {
return info.isEvaluatedRepeatedly();
}
}
return false;
}
/**
* Get the focus-setting container of an expression
*
* *
*
Note, this always returns an expression or null. Unlike the like-named concept in the
* spec, it can't return a component such as a template or an attribute set.
*
* @param exp the expression whose focus-setting container is required
* @return the focus-setting container, or null if the focus for the expression is the same as the
* focus for the containing component as a whole
*/
public static Expression getFocusSettingContainer(Expression exp) {
Expression child = exp;
Expression parent = child.getParentExpression();
while (parent != null) {
Operand o = findOperand(parent, child);
if (o == null) {
throw new AssertionError();
}
if (!o.hasSameFocus()) {
return parent;
}
child = parent;
parent = child.getParentExpression();
}
return null;
}
/**
* Get the context-document-setting container of an expression. This is the same as the
* focus-setting container, except when the context-setting operand is a single-document node-set,
* in which case we can go up one more level. For example, given /a/b[/d/e = 3], the predicate
* /d/e = 3 can be loop-lifted from the filter expression, because it is known that the base
* expression /a/b is a single-document node-set.
*
* @param exp the expression whose document-context-setting container is required
* @return the context-document-setting container, or null if the focus for the expression is the same as the
* focus for the containing component as a whole
*/
public static Expression getContextDocumentSettingContainer(Expression exp) {
Expression child = exp;
Expression parent = child.getParentExpression();
while (parent != null) {
if (parent instanceof ContextSwitchingExpression) {
ContextSwitchingExpression switcher = (ContextSwitchingExpression) parent;
if (child == switcher.getActionExpression()) {
if (switcher.getSelectExpression().hasSpecialProperty(StaticProperty.CONTEXT_DOCUMENT_NODESET)) {
parent.resetLocalStaticProperties();
parent.getSpecialProperties();
return getContextDocumentSettingContainer(parent);
}
}
}
Operand o = findOperand(parent, child);
if (o == null) {
throw new AssertionError();
}
if (!o.hasSameFocus()) {
return parent;
}
child = parent;
parent = child.getParentExpression();
}
return null;
}
/**
* Reset the static properties for the current expression and for all its containing expressions.
* This should be done whenever the expression is changed in a way that might
* affect the properties. It causes the properties to be recomputed next time they are needed.
*
* @param exp the expression whose properties are to be reset; the method also resets local
* properties for all its ancestor expressions.
*/
public static void resetStaticProperties(Expression exp) {
int i = 0;
while (exp != null) {
exp.resetLocalStaticProperties();
exp = exp.getParentExpression();
if (i++ > 100000) {
throw new IllegalStateException("Loop in parent expression chain");
}
}
}
/**
* Return true if two objects are equal or if both are null
*
* @param x the first object
* @param y the second object
* @return true if both x and y are null or if x.equals(y)
*/
public static boolean equalOrNull(Object x, Object y) {
if (x == null) {
return y == null;
} else {
return x.equals(y);
}
}
/**
* Helper method to construct an iterator over the results of the expression when all that
* the expression itself offers is a process() method. This builds the entire results of the
* expression as a sequence in memory and then iterates over it.
*
* @param exp the expression
* @param context the dynamic evaluation context
* @return an iterator over the results of the expression
* @throws XPathException if a dynamic error occurs
*/
public static SequenceIterator getIteratorFromProcessMethod(
Expression exp, XPathContext context) throws XPathException {
Controller controller = context.getController();
assert controller != null;
SequenceCollector seq = controller.allocateSequenceOutputter();
exp.process(new ComplexContentOutputter(seq), context);
seq.close();
return seq.iterate();
}
/**
* Helper method to construct an item representing the results of the expression when all that
* the expression itself offers is a process() method.
*
* @param exp the expression
* @param context the dynamic evaluation context
* @return an iterator over the results of the expression
* @throws XPathException if a dynamic error occurs
*/
public static Item getItemFromProcessMethod(Expression exp, XPathContext context) throws XPathException {
Controller controller = context.getController();
if (controller == null) {
throw new NoDynamicContextException("No controller available");
}
SequenceCollector seq = controller.allocateSequenceOutputter(1);
exp.process(new ComplexContentOutputter(seq), context);
seq.close();
Item result = seq.getFirstItem();
seq.reset();
return result;
}
/**
* Allocate slot numbers to range variables
*
* @param exp the expression whose range variables need to have slot numbers assigned
* @param nextFree the next slot number that is available for allocation
* @param frame a SlotManager object that is used to track the mapping of slot numbers
* to variable names for debugging purposes. May be null.
* @return the next unallocated slot number.
*/
public static int allocateSlots(Expression exp, int nextFree, SlotManager frame) {
if (exp instanceof Assignation) {
((Assignation) exp).setSlotNumber(nextFree);
int count = ((Assignation) exp).getRequiredSlots();
nextFree += count;
if (frame != null) {
frame.allocateSlotNumber(((Assignation) exp).getVariableQName());
}
}
if (exp instanceof LocalParam && ((LocalParam) exp).getSlotNumber() < 0) {
((LocalParam) exp).setSlotNumber(nextFree++);
}
if (exp instanceof FLWORExpression) {
for (Clause c : ((FLWORExpression) exp).getClauseList()) {
for (LocalVariableBinding b : c.getRangeVariables()) {
b.setSlotNumber(nextFree++);
frame.allocateSlotNumber(b.getVariableQName());
}
}
}
if (exp instanceof VariableReference) {
VariableReference var = (VariableReference) exp;
Binding binding = var.getBinding();
if (exp instanceof LocalVariableReference) {
((LocalVariableReference) var).setSlotNumber(((LocalBinding) binding).getLocalSlotNumber());
}
if (binding instanceof Assignation && ((LocalBinding) binding).getLocalSlotNumber() < 0) {
// This indicates something badly wrong: we've found a variable reference on the tree, that's
// bound to a variable declaration that is no longer on the tree. All we can do is print diagnostics.
// The most common reason for this failure is that the declaration of the variable was removed
// from the tree in the mistaken belief that there were no references to the variable. Variable
// references are counted during the typeCheck phase, so this can happen if typeCheck() fails to
// visit some branch of the expression tree.
Assignation decl = (Assignation) binding;
Logger err;
try {
err = exp.getConfiguration().getLogger();
} catch (Exception ex) {
err = new StandardLogger();
}
String msg = "*** Internal Saxon error: local variable encountered whose binding has been deleted";
err.error(msg);
err.error("Variable name: " + decl.getVariableName());
err.error("Line number of reference: " + var.getLocation().getLineNumber() + " in " + var.getLocation().getSystemId());
err.error("Line number of declaration: " + decl.getLocation().getLineNumber() + " in " + decl.getLocation().getSystemId());
err.error("DECLARATION:");
try {
decl.explain(err);
} catch (Exception e) {
// ignore the secondary error
}
throw new IllegalStateException(msg);
}
}
if (exp instanceof Pattern) {
nextFree = ((Pattern) exp).allocateSlots(frame, nextFree);
} else if (exp instanceof ScopedBindingElement) {
nextFree = ((ScopedBindingElement) exp).allocateSlots(frame, nextFree);
} else {
for (Operand o : exp.operands()) {
nextFree = allocateSlots(o.getChildExpression(), nextFree, frame);
}
}
return nextFree;
// Note, we allocate a distinct slot to each range variable, even if the
// scopes don't overlap. This isn't strictly necessary, but might help
// debugging.
}
/**
* Determine the effective boolean value of a sequence, given an iterator over the sequence
*
* @param iterator An iterator over the sequence whose effective boolean value is required
* @return the effective boolean value
* @throws XPathException if a dynamic error occurs
*/
public static boolean effectiveBooleanValue(SequenceIterator iterator) throws XPathException {
Item first = iterator.next();
if (first == null) {
return false;
}
Genre genre = first.getGenre(); // Variable introduced for C# type checking
switch (genre) {
case NODE:
iterator.close();
return true;
case ATOMIC: {
if (first instanceof BooleanValue) {
if (iterator.next() != null) {
iterator.close();
ebvError("a sequence of two or more items starting with a boolean");
}
iterator.close();
return ((BooleanValue) first).getBooleanValue();
} else if (first instanceof StringValue) { // includes anyURI value
if (iterator.next() != null) {
iterator.close();
ebvError("a sequence of two or more items starting with a string ('" + first.getStringValue() + "')");
}
return !((StringValue) first).isEmpty();
} else if (first instanceof NumericValue) {
if (iterator.next() != null) {
iterator.close();
ebvError("a sequence of two or more items starting with a numeric value (" + first.getStringValue() + ")");
}
final NumericValue n = (NumericValue) first;
return (n.compareTo(0) != 0) && !n.isNaN();
} else {
iterator.close();
ebvError("a sequence starting with an atomic value of type " + ((AtomicValue) first).getItemType().getTypeName().getDisplayName());
return false;
}
}
case ARRAY:
iterator.close();
ebvError("a sequence starting with an array item (" + first.toShortString() + ")");
return false;
case MAP:
iterator.close();
ebvError("a sequence starting with a map (" + first.toShortString() + ")");
return false;
case FUNCTION: {
iterator.close();
ebvError("a sequence starting with a function (" + first.toShortString() + ")");
return false;
}
case EXTERNAL: {
if (iterator.next() != null) {
iterator.close();
ebvError("a sequence of two or more items starting with an external object value");
}
return true;
}
}
ebvError("a sequence starting with an item of unknown kind");
return false;
}
/**
* Determine the effective boolean value of a single item
*
* @param item the item whose effective boolean value is required
* @return the effective boolean value
* @throws XPathException if a dynamic error occurs
*/
public static boolean effectiveBooleanValue(Item item) throws XPathException {
if (item == null) {
return false;
}
if (item instanceof NodeInfo) {
return true;
} else if (item instanceof AtomicValue) {
if (item instanceof BooleanValue) {
return ((BooleanValue) item).getBooleanValue();
} else if (item instanceof StringValue) { // includes anyURI value
return !((StringValue) item).isEmpty();
} else if (item instanceof NumericValue) {
final NumericValue n = (NumericValue) item;
return (n.compareTo(0) != 0) && !n.isNaN();
} else if (item.getGenre() == Genre.EXTERNAL) {
return true;
} else {
ebvError("an atomic value of type " + ((AtomicValue) item).getPrimitiveType().getDisplayName());
return false;
}
} else {
ebvError(item.getGenre().toString());
return false;
}
}
/**
* Report an error in computing the effective boolean value of an expression
*
* @param reason the nature of the error
* @throws XPathException always
*/
public static void ebvError(String reason) throws XPathException {
XPathException err = new XPathException("Effective boolean value is not defined for " + reason);
err.setErrorCode("FORG0006");
err.setIsTypeError(true);
throw err;
}
/**
* Report an error in computing the effective boolean value of an expression
*
* @param reason the nature of the error
* @param cause the failing expression
* @throws XPathException always
*/
public static void ebvError(String reason, Expression cause) throws XPathException {
XPathException err = new XPathException("Effective boolean value is not defined for " + reason);
err.setErrorCode("FORG0006");
err.setIsTypeError(true);
err.setFailingExpression(cause);
throw err;
}
/**
* Ask whether an expression has a dependency on the focus
*
* @param exp the expression
* @return true if the value of the expression depends on the context item, position, or size
*/
public static boolean dependsOnFocus(Expression exp) {
return (exp.getDependencies() & StaticProperty.DEPENDS_ON_FOCUS) != 0;
}
/**
* Determine whether an expression depends on any one of a set of variables
*
* @param exp the expression being tested
* @param bindingList the set of variables being tested
* @return true if the expression depends on one of the given variables
*/
public static boolean dependsOnVariable(Expression exp, final Binding[] bindingList) {
return !(bindingList == null || bindingList.length == 0) &&
contains(exp, false, e -> {
if (e instanceof VariableReference) {
for (Binding binding : bindingList) {
if (((VariableReference) e).getBinding() == binding) {
return true;
}
}
}
return false;
});
}
/**
* Gather a list of all the variable bindings on which a given expression depends.
* In the light of spec bug 29590, this only considers variable references that
* are unconditionally evaluated: that is, it ignores variable references appearing
* in the then/else branches of a conditional or equivalent. Cycles involving
* conditional evaluation are detected dynamically.
*
* @param e the expression being tested
* @param list a list to which the bindings are to be added. The items in this list must
* implement {@link Binding}
*/
public static void gatherReferencedVariables(Expression e, List list) {
if (e instanceof VariableReference) {
Binding binding = ((VariableReference) e).getBinding();
if (!list.contains(binding)) {
list.add(binding);
}
} else {
for (Operand o : e.operands()) {
if (!o.getOperandRole().isInChoiceGroup()) {
gatherReferencedVariables(o.getChildExpression(), list);
}
}
}
}
/**
* Determine whether the expression contains any variable references or calls to user-written functions
*
* @param exp the expression being tested
* @return true if the expression includes a variable reference or function call, or an XSLT construct
* equivalent to a function call (e.g call-template). Also returns true if the expression includes
* a variable binding element, as (a) this is likely to mean it also contains a reference, and (b)
* it also needs to be caught on the same paths.
*/
public static boolean refersToVariableOrFunction(Expression exp) {
return contains(exp, false,
e -> e instanceof VariableReference
|| e instanceof UserFunctionCall
|| e instanceof Binding
|| e instanceof CallTemplate
|| e instanceof ApplyTemplates
|| e instanceof ApplyImports
|| isCallOnSystemFunction(e, "function-lookup")
|| e.isCallOn(ApplyFn.class));
}
public static boolean isCallOnSystemFunction(Expression e, String localName) {
return e instanceof StaticFunctionCall && localName.equals(((StaticFunctionCall) e).getFunctionName().getLocalPart());
}
/**
* Determine whether an expression contains a call on the function with a given name
*
* @param exp The expression being tested
* @param qName The name of the function
* @param sameFocusOnly If true, only expressions with the same (top-level) focus are searched
* @return true if the expression contains a call on the function
*/
public static boolean callsFunction(Expression exp, final StructuredQName qName, boolean sameFocusOnly) {
return contains(exp, sameFocusOnly,
e -> e instanceof FunctionCall && qName.equals(((FunctionCall) e).getFunctionName())
);
}
/**
* Determine whether an expression has a subexpression of a given implementation class
*
* @param exp The expression being tested
* @param subClass The implementation class of the sought subexpression
* @return true if the expression contains a subexpression that is an instance of the specified class
*/
public static boolean containsSubexpression(Expression exp, final Class subClass) {
return contains(exp, false, e -> subClass.isAssignableFrom(e.getClass()));
}
/**
* Gather a list of all the user-defined functions which a given expression calls directly
*
* @param e the expression being tested
* @param list a list of the functions that are called. The items in this list must
* be objects of class {@link UserFunction}
*/
public static void gatherCalledFunctions(Expression e, List list) {
if (e instanceof UserFunctionCall) {
UserFunction function = ((UserFunctionCall) e).getFunction();
if (!list.contains(function)) {
list.add(function);
}
} else {
for (Operand o : e.operands()) {
gatherCalledFunctions(o.getChildExpression(), list);
}
}
}
/**
* Gather a list of the names of the user-defined functions which a given expression calls directly
*
* @param e the expression being tested
* @param list a list of the functions that are called. The items in this list are strings in the format
* "{uri}local/arity"
*/
public static void gatherCalledFunctionNames(Expression e, List list) {
if (e instanceof UserFunctionCall) {
list.add(((UserFunctionCall) e).getSymbolicName());
} else {
for (Operand o : e.operands()) {
gatherCalledFunctionNames(o.getChildExpression(), list);
}
}
}
/**
* Optimize the implementation of a component such as a function, template, or global variable
*
* @param body the expression forming the body of the component
* @param compilation the current compilation. May be null.
* @param visitor the expression visitor
* @param cisi information about the context item for evaluation of the component body
* @param extractGlobals true if constant expressions are to be extracted as global variables
* @return the optimized expression body
* @throws XPathException if anything goes wrong
*/
public static Expression optimizeComponentBody(
Expression body, final Compilation compilation, ExpressionVisitor visitor, ContextItemStaticInfo cisi, boolean extractGlobals)
throws XPathException {
final Configuration config = visitor.getConfiguration();
Optimizer opt = visitor.obtainOptimizer();
StaticContext env = visitor.getStaticContext();
// boolean compileWithTracing = config.isCompileWithTracing();
// if (!compileWithTracing) {
// // Bug 3472 - desperate attempts to discover whether tracing was enabled for this particular compilation
// if (compilation != null) {
// compileWithTracing = compilation.getCompilerInfo().isCompileWithTracing();
// } else if (env instanceof QueryModule) {
// compileWithTracing = ((QueryModule) env).getUserQueryContext().isCompileWithTracing();
// } else if (env instanceof ExpressionContext) {
// compileWithTracing = ((ExpressionContext) env).getStyleElement().getCompilation().getCompilerInfo().isCompileWithTracing();
// }
// }
if (opt.isOptionSet(OptimizerOptions.MISCELLANEOUS)) {
ExpressionTool.resetPropertiesWithinSubtree(body);
if (opt.isOptionSet(OptimizerOptions.MISCELLANEOUS)) {
body = body.optimize(visitor, cisi);
}
body.setParentExpression(null);
if (extractGlobals && compilation != null) {
Expression exp2 = opt.promoteExpressionsToGlobal(body, compilation.getPrincipalStylesheetModule(), visitor);
if (exp2 != null) {
// Try another optimization pass: extracting global variables can identify things that are indexable
ExpressionTool.resetPropertiesWithinSubtree(exp2);
body = exp2.optimize(visitor, cisi);
}
}
if (opt.isOptionSet(OptimizerOptions.LOOP_LIFTING)) {
body = LoopLifter.process(body, visitor, cisi);
}
} else {
body = avoidDocumentSort(body);
}
if (!visitor.isOptimizeForStreaming()) {
body = opt.eliminateCommonSubexpressions(body);
}
opt.prepareForStreaming(body);
computeEvaluationModesForUserFunctionCalls(body);
body.restoreParentPointers();
return body;
}
/**
* An optimization-lite pass over the expression tree that attempts to eliminate unnecessary
* sorting into document order. We avoid a full optimization when STRICT_STREAMABILITY analysis
* is requested, because it rewrites non-streamable expressions into streamable expressions;
* but to get the streamability right, we need as a minimum to eliminate unwanted document sort
* operations.
*/
private static Expression avoidDocumentSort(Expression exp) {
if (exp instanceof DocumentSorter) {
Expression base = ((DocumentSorter) exp).getBaseExpression();
if (base.hasSpecialProperty(StaticProperty.ORDERED_NODESET)) {
return base;
}
return exp;
} else if (exp instanceof ConditionalSorter) {
DocumentSorter sorter = ((ConditionalSorter) exp).getDocumentSorter();
Expression eliminatedSorter = avoidDocumentSort(sorter);
if (eliminatedSorter != sorter) {
return eliminatedSorter;
}
}
for (Operand o : exp.operands()) {
o.setChildExpression(avoidDocumentSort(o.getChildExpression()));
}
return exp;
}
/**
* Compute argument evaluation modes for all calls on user defined functions with
* a specified expression
*
* @param exp the expression
* @throws XPathException if any error occurs
*/
public static void computeEvaluationModesForUserFunctionCalls(Expression exp) throws XPathException {
ExpressionTool.processExpressionTree(exp, null, (expression, result) -> {
if (expression instanceof UserFunctionCall) {
((UserFunctionCall) expression).allocateArgumentEvaluators();
}
if (expression instanceof LocalParam) {
((LocalParam) expression).computeEvaluationMode();
}
return false;
});
}
/**
* Clear all computed streamability properties for an expression and its contained subtree
*
* @param exp the expression whose streamability data is to be reset
* @throws XPathException should not happen
*/
public static void clearStreamabilityData(Expression exp) throws XPathException {
ExpressionTool.processExpressionTree(exp, null, (expression, result) -> {
expression.setExtraProperty("P+S", null);
expression.setExtraProperty("inversion", null);
return false;
});
}
/**
* Reset cached static properties within a subtree, meaning that they have to be
* recalulated next time they are required
*
* @param exp the root of the subtree within which static properties should be reset
*/
public static void resetPropertiesWithinSubtree(Expression exp) {
exp.resetLocalStaticProperties();
if (exp instanceof LocalVariableReference) {
LocalVariableReference ref = (LocalVariableReference) exp;
Binding binding = ref.getBinding();
if (binding instanceof Assignation) {
binding.addReference(ref, ref.isInLoop());
}
}
for (Operand o : exp.operands()) {
resetPropertiesWithinSubtree(o.getChildExpression());
o.getChildExpression().setParentExpression(exp);
}
}
/**
* Resolve calls to the XSLT current() function within an expression
*
* @param exp the expression within which calls to current() should be resolved
* @return the expression after resolving calls to current()
*/
public static Expression resolveCallsToCurrentFunction(Expression exp) {
if (exp.isCallOn(Current.class)) {
ContextItemExpression cie = new ContextItemExpression();
copyLocationInfo(exp, cie);
return cie;
} else {
if (callsFunction(exp, Current.FN_CURRENT, true)) {
// replace trivial (same-focus) calls to current by a simple "."
replaceTrivialCallsToCurrent(exp);
}
if (callsFunction(exp, Current.FN_CURRENT, false)) {
// replace non-trivial (different-focus) calls to current by a variable reference
LetExpression let = new LetExpression();
let.setVariableQName(
new StructuredQName("vv", NamespaceConstant.SAXON_GENERATED_VARIABLE, "current" + exp.hashCode()));
let.setRequiredType(SequenceType.SINGLE_ITEM);
let.setSequence(new CurrentItemExpression());
replaceCallsToCurrent(exp, let);
let.setAction(exp);
return let;
} else {
return exp;
}
}
}
/**
* Get a list of all references to a particular variable within a subtree
*
* @param exp the expression at the root of the subtree
* @param binding the variable binding whose references are sought
* @param list a list to be populated with the references to this variable
*/
public static void gatherVariableReferences(Expression exp, Binding binding, List list) {
if (exp instanceof VariableReference &&
((VariableReference) exp).getBinding() == binding) {
list.add((VariableReference) exp);
} else {
for (Operand o : exp.operands()) {
gatherVariableReferences(o.getChildExpression(), binding, list);
}
}
}
/**
* Process every node on a subtree of the expression tree using a supplied action.
*
* @param root the root of the subtree to be processed
* @param result an arbitrary object that is passed to each action call and that can be
* updated to gather results of the processing
* @param action an action to be performed on each node of the expression tree. Processing
* stops if any action returns the value true
* @return true if any call on the action operand returned true
* @throws XPathException if the callback throws an error
*/
public static boolean processExpressionTree(Expression root, Object result, ExpressionAction action) throws XPathException {
boolean done = action.process(root, result);
if (!done) {
for (Operand o : root.operands()) {
done = processExpressionTree(o.getChildExpression(), result, action);
if (done) {
return true;
}
}
}
return false;
}
/**
* Replace all selected subexpressions within a subtree
*
* @param exp the expression at the root of the subtree
* @param selector callback to determine whether a subexpression is selected
* @param replacement the expression to be used in place of the variable reference
* @param mustCopy if true, the replacement expression must be copied before use
* @return true if a replacement has been performed (in which case the replacement expression
* must be copied before being used again).
*/
public static boolean replaceSelectedSubexpressions(
Expression exp, Predicate selector, Expression replacement, boolean mustCopy) {
boolean replaced = false;
for (Operand o : exp.operands()) {
if (replaced) {
mustCopy = true;
}
Expression child = o.getChildExpression();
if (selector.test(child)) {
Expression e2 = mustCopy ? replacement.copy(new RebindingMap()) : replacement;
o.setChildExpression(e2);
replaced = true;
} else {
replaced |= replaceSelectedSubexpressions(child, selector, replacement, mustCopy);
}
}
return replaced;
}
/**
* Replace all references to a particular variable within a subtree
*
* @param exp the expression at the root of the subtree
* @param binding the variable binding whose references are sought
* @param replacement the expression to be used in place of the variable reference
* @param mustCopy true if the replacement expression must be copied before use
*/
public static void replaceVariableReferences(Expression exp, final Binding binding, Expression replacement, boolean mustCopy) {
Predicate selector =
child -> child instanceof VariableReference && ((VariableReference) child).getBinding() == binding;
boolean changed = replaceSelectedSubexpressions(exp, selector, replacement, mustCopy);
if (changed) {
resetPropertiesWithinSubtree(exp);
}
}
/**
* Determine how often a variable is referenced. This is the number of times
* it is referenced at run-time: so a reference in a loop counts as "many". This code
* currently handles local variables (Let expressions) and function parameters. It is
* not currently used for XSLT template parameters. It's not the end of the world if
* the answer is wrong (unless it's wrongly given as zero), but if wrongly returned as
* 1 then the variable will be repeatedly evaluated.
*
* @param exp the expression within which variable references are to be counted
* @param binding identifies the variable of interest
* @param inLoop true if the expression is within a loop, in which case a reference counts as many.
* This should be set to false on the initial call, it may be set to true on an internal recursive
* call
* @return the number of references. The interesting values are 0, 1, "many" (represented
* by any value >1), and the special value FILTERED, which indicates that there are
* multiple references and one or more of them is of the form {@code $x[....]} indicating that an
* index might be useful.
*/
public static int getReferenceCount(Expression exp, Binding binding, boolean inLoop) {
int rcount = 0;
if (exp instanceof VariableReference && ((VariableReference) exp).getBinding() == binding) {
if (((VariableReference) exp).isFiltered()) {
return FilterExpression.FILTERED;
} else {
rcount += inLoop ? 10 : 1;
}
} else if ((exp.getDependencies() & StaticProperty.DEPENDS_ON_LOCAL_VARIABLES) == 0) {
return 0;
} else {
for (Operand info : exp.operands()) {
Expression child = info.getChildExpression();
boolean childLoop = inLoop || info.isEvaluatedRepeatedly();
rcount += getReferenceCount(child, binding, childLoop);
if (rcount >= FilterExpression.FILTERED) {
break;
}
}
}
return rcount;
}
/**
* Get the size of an expression tree (the number of subexpressions it contains)
*
* @param exp the expression whose size is required
* @return the size of the expression tree, as the number of nodes
*/
public static int expressionSize(Expression exp) {
exp = exp.getInterpretedExpression();
int total = 1;
for (Operand o : exp.operands()) {
total += expressionSize(o.getChildExpression());
if (o.getChildExpression() instanceof UserFunctionReference) { // bug 5054
UserFunction uf = ((UserFunctionReference) o.getChildExpression()).getNominalTarget();
total += expressionSize(uf.getBody());
}
}
return total;
}
/**
* Rebind all variable references to a binding
*
* @param exp the expression whose contained variable references are to be rebound
* @param oldBinding the old binding for the variable references
* @param newBinding the new binding to which the variables should be rebound
*/
public static void rebindVariableReferences(
Expression exp, Binding oldBinding, Binding newBinding) {
if (exp instanceof VariableReference) {
if (((VariableReference) exp).getBinding() == oldBinding) {
((VariableReference) exp).fixup(newBinding);
}
} else {
for (Operand o : exp.operands()) {
rebindVariableReferences(o.getChildExpression(), oldBinding, newBinding);
}
}
}
/**
* Make a mapping expression. The resulting expression will include logic to check that the first operand
* returns nodes, and that the expression as a whole is homogeneous, unless the caller requests otherwise.
*
* @param start the start expression (the first operand of "/")
* @param step the step expression (the second operand of "/")
* @return the resulting expression.
*/
/*@NotNull*/
public static Expression makePathExpression(Expression start, Expression step) {
// the expression /.. is sometimes used to represent the empty node-set. Applying this simplification
// now avoids generating warnings for this case.
if (start instanceof RootExpression &&
step instanceof AxisExpression && ((AxisExpression) step).getAxis() == AxisInfo.PARENT) {
return Literal.makeEmptySequence();
}
SlashExpression expr = new SlashExpression(start, step);
// If start is a path expression such as a, and step is b/c, then
// instead of a/(b/c) we construct (a/b)/c. This is because it often avoids
// a sort.
// The "/" operator in XPath 2.0 is not always left-associative. Problems
// can occur if position() and last() are used on the rhs, or if node-constructors
// appear, e.g. //b/../ ops = exp.operands().iterator();
if (!ops.hasNext()) {
return false;
}
Operand o = ops.next(); // dummy variable needed for C# conversion
return ops.hasNext();
}
public static void validateTree(Expression exp) {
try {
for (Operand o : exp.checkedOperands()) {
validateTree(o.getChildExpression());
}
} catch (IllegalStateException e) {
e.printStackTrace();
}
}
/**
* Ask whether a supplied expression is a nested node constructor.
* That is, return true if the child expression creates nodes that will only be
* used as children of some parent node (meaning that they never need to be copied).
*
* @param child child expression to be tested
* @return true if the node constructed by the child expression does not need to be copied.
*/
public static boolean isLocalConstructor(Expression child) {
if (!(child instanceof ParentNodeConstructor || child instanceof SimpleNodeConstructor)) {
return false;
}
Expression parent = child.getParentExpression();
while (parent != null) {
if (parent instanceof ParentNodeConstructor) {
return true;
}
Operand o = findOperand(parent, child);
if (o.getUsage() != OperandUsage.TRANSMISSION) {
return false;
}
child = parent;
parent = parent.getParentExpression();
}
return false;
}
}