/*
* Copyright 2001-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* $Id: Predicate.java,v 1.35 2004/12/15 17:35:38 jycli Exp $
*/
package org.apache.xalan.xsltc.compiler;
import java.util.ArrayList;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.generic.ASTORE;
import org.apache.bcel.generic.CHECKCAST;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.GETFIELD;
import org.apache.bcel.generic.INVOKESPECIAL;
import org.apache.bcel.generic.InstructionList;
import org.apache.bcel.generic.LocalVariableGen;
import org.apache.bcel.generic.NEW;
import org.apache.bcel.generic.PUSH;
import org.apache.bcel.generic.PUTFIELD;
import org.apache.xalan.xsltc.compiler.util.BooleanType;
import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
import org.apache.xalan.xsltc.compiler.util.FilterGenerator;
import org.apache.xalan.xsltc.compiler.util.IntType;
import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
import org.apache.xalan.xsltc.compiler.util.NumberType;
import org.apache.xalan.xsltc.compiler.util.ReferenceType;
import org.apache.xalan.xsltc.compiler.util.ResultTreeType;
import org.apache.xalan.xsltc.compiler.util.TestGenerator;
import org.apache.xalan.xsltc.compiler.util.Type;
import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
import org.apache.xalan.xsltc.compiler.util.Util;
import org.apache.xalan.xsltc.runtime.Operators;
/**
* @author Jacek Ambroziak
* @author Santiago Pericas-Geertsen
* @author Morten Jorgensen
*/
final class Predicate extends Expression implements Closure {
/**
* The predicate's expression.
*/
private Expression _exp = null;
/**
* This flag indicates if optimizations are turned on. The
* method <code>dontOptimize()</code> can be called to turn
* optimizations off.
*/
private boolean _canOptimize = true;
/**
* Flag indicatig if the nth position optimization is on. It
* is set in <code>typeCheck()</code>.
*/
private boolean _nthPositionFilter = false;
/**
* Flag indicatig if the nth position descendant is on. It
* is set in <code>typeCheck()</code>.
*/
private boolean _nthDescendant = false;
/**
* Cached node type of the expression that owns this predicate.
*/
int _ptype = -1;
/**
* Name of the inner class.
*/
private String _className = null;
/**
* List of variables in closure.
*/
private ArrayList _closureVars = null;
/**
* Reference to parent closure.
*/
private Closure _parentClosure = null;
/**
* Cached value of method <code>getCompareValue()</code>.
*/
private Expression _value = null;
/**
* Cached value of method <code>getCompareValue()</code>.
*/
private Step _step = null;
/**
* Initializes a predicate.
*/
public Predicate(Expression exp) {
_exp = exp;
_exp.setParent(this);
}
/**
* Set the parser for this expression.
*/
public void setParser(Parser parser) {
super.setParser(parser);
_exp.setParser(parser);
}
/**
* Returns a boolean value indicating if the nth position optimization
* is on. Must be call after type checking!
*/
public boolean isNthPositionFilter() {
return _nthPositionFilter;
}
/**
* Returns a boolean value indicating if the nth descendant optimization
* is on. Must be call after type checking!
*/
public boolean isNthDescendant() {
return _nthDescendant;
}
/**
* Turns off all optimizations for this predicate.
*/
public void dontOptimize() {
_canOptimize = false;
}
/**
* Returns true if the expression in this predicate contains a call
* to position().
*/
public boolean hasPositionCall() {
return _exp.hasPositionCall();
}
/**
* Returns true if the expression in this predicate contains a call
* to last().
*/
public boolean hasLastCall() {
return _exp.hasLastCall();
}
// -- Begin Closure interface --------------------
/**
* Returns true if this closure is compiled in an inner class (i.e.
* if this is a real closure).
*/
public boolean inInnerClass() {
return (_className != null);
}
/**
* Returns a reference to its parent closure or null if outermost.
*/
public Closure getParentClosure() {
if (_parentClosure == null) {
SyntaxTreeNode node = getParent();
do {
if (node instanceof Closure) {
_parentClosure = (Closure) node;
break;
}
if (node instanceof TopLevelElement) {
break; // way up in the tree
}
node = node.getParent();
} while (node != null);
}
return _parentClosure;
}
/**
* Returns the name of the auxiliary class or null if this predicate
* is compiled inside the Translet.
*/
public String getInnerClassName() {
return _className;
}
/**
* Add new variable to the closure.
*/
public void addVariable(VariableRefBase variableRef) {
if (_closureVars == null) {
_closureVars = new ArrayList();
}
// Only one reference per variable
if (!_closureVars.contains(variableRef)) {
_closureVars.add(variableRef);
// Add variable to parent closure as well
Closure parentClosure = getParentClosure();
if (parentClosure != null) {
parentClosure.addVariable(variableRef);
}
}
}
// -- End Closure interface ----------------------
/**
* Returns the node type of the expression owning this predicate. The
* return value is cached in <code>_ptype</code>.
*/
public int getPosType() {
if (_ptype == -1) {
SyntaxTreeNode parent = getParent();
if (parent instanceof StepPattern) {
_ptype = ((StepPattern)parent).getNodeType();
}
else if (parent instanceof AbsoluteLocationPath) {
AbsoluteLocationPath path = (AbsoluteLocationPath)parent;
Expression exp = path.getPath();
if (exp instanceof Step) {
_ptype = ((Step)exp).getNodeType();
}
}
else if (parent instanceof VariableRefBase) {
final VariableRefBase ref = (VariableRefBase)parent;
final VariableBase var = ref.getVariable();
final Expression exp = var.getExpression();
if (exp instanceof Step) {
_ptype = ((Step)exp).getNodeType();
}
}
else if (parent instanceof Step) {
_ptype = ((Step)parent).getNodeType();
}
}
return _ptype;
}
public boolean parentIsPattern() {
return (getParent() instanceof Pattern);
}
public Expression getExpr() {
return _exp;
}
public String toString() {
return "pred(" + _exp + ')';
}
/**
* Type check a predicate expression. If the type of the expression is
* number convert it to boolean by adding a comparison with position().
* Note that if the expression is a parameter, we cannot distinguish
* at compile time if its type is number or not. Hence, expressions of
* reference type are always converted to booleans.
*
* This method may be called twice, before and after calling
* <code>dontOptimize()</code>. If so, the second time it should honor
* the new value of <code>_canOptimize</code>.
*/
public Type typeCheck(SymbolTable stable) throws TypeCheckError {
Type texp = _exp.typeCheck(stable);
// We need explicit type information for reference types - no good!
if (texp instanceof ReferenceType) {
_exp = new CastExpr(_exp, texp = Type.Real);
}
// A result tree fragment should not be cast directly to a number type,
// but rather to a boolean value, and then to a numer (0 or 1).
// Ref. section 11.2 of the XSLT 1.0 spec
if (texp instanceof ResultTreeType) {
_exp = new CastExpr(_exp, Type.Boolean);
_exp = new CastExpr(_exp, Type.Real);
texp = _exp.typeCheck(stable);
}
// Numerical types will be converted to a position filter
if (texp instanceof NumberType) {
// Cast any numerical types to an integer
if (texp instanceof IntType == false) {
_exp = new CastExpr(_exp, Type.Int);
}
if (_canOptimize) {
// Nth position optimization. Expression must not depend on context
_nthPositionFilter =
!_exp.hasLastCall() && !_exp.hasPositionCall();
// _nthDescendant optimization - only if _nthPositionFilter is on
if (_nthPositionFilter) {
SyntaxTreeNode parent = getParent();
_nthDescendant = (parent instanceof Step) &&
(parent.getParent() instanceof AbsoluteLocationPath);
return _type = Type.NodeSet;
}
}
// Reset optimization flags
_nthPositionFilter = _nthDescendant = false;
// Otherwise, expand [e] to [position() = e]
final QName position =
getParser().getQNameIgnoreDefaultNs("position");
final PositionCall positionCall =
new PositionCall(position);
positionCall.setParser(getParser());
positionCall.setParent(this);
_exp = new EqualityExpr(Operators.EQ, positionCall,
_exp);
if (_exp.typeCheck(stable) != Type.Boolean) {
_exp = new CastExpr(_exp, Type.Boolean);
}
return _type = Type.Boolean;
}
else {
// All other types will be handled as boolean values
if (texp instanceof BooleanType == false) {
_exp = new CastExpr(_exp, Type.Boolean);
}
return _type = Type.Boolean;
}
}
/**
* Create a new "Filter" class implementing
* <code>CurrentNodeListFilter</code>. Allocate registers for local
* variables and local parameters passed in the closure to test().
* Notice that local variables need to be "unboxed".
*/
private void compileFilter(ClassGenerator classGen,
MethodGenerator methodGen) {
TestGenerator testGen;
LocalVariableGen local;
FilterGenerator filterGen;
_className = getXSLTC().getHelperClassName();
filterGen = new FilterGenerator(_className,
"java.lang.Object",
toString(),
ACC_PUBLIC | ACC_SUPER,
new String[] {
CURRENT_NODE_LIST_FILTER
},
classGen.getStylesheet());
final ConstantPoolGen cpg = filterGen.getConstantPool();
final int length = (_closureVars == null) ? 0 : _closureVars.size();
// Add a new instance variable for each var in closure
for (int i = 0; i < length; i++) {
VariableBase var = ((VariableRefBase) _closureVars.get(i)).getVariable();
filterGen.addField(new Field(ACC_PUBLIC,
cpg.addUtf8(var.getEscapedName()),
cpg.addUtf8(var.getType().toSignature()),
null, cpg.getConstantPool()));
}
final InstructionList il = new InstructionList();
testGen = new TestGenerator(ACC_PUBLIC | ACC_FINAL,
org.apache.bcel.generic.Type.BOOLEAN,
new org.apache.bcel.generic.Type[] {
org.apache.bcel.generic.Type.INT,
org.apache.bcel.generic.Type.INT,
org.apache.bcel.generic.Type.INT,
org.apache.bcel.generic.Type.INT,
Util.getJCRefType(TRANSLET_SIG),
Util.getJCRefType(NODE_ITERATOR_SIG)
},
new String[] {
"node",
"position",
"last",
"current",
"translet",
"iterator"
},
"test", _className, il, cpg);
// Store the dom in a local variable
local = testGen.addLocalVariable("document",
Util.getJCRefType(DOM_INTF_SIG),
null, null);
final String className = classGen.getClassName();
il.append(filterGen.loadTranslet());
il.append(new CHECKCAST(cpg.addClass(className)));
il.append(new GETFIELD(cpg.addFieldref(className,
DOM_FIELD, DOM_INTF_SIG)));
il.append(new ASTORE(local.getIndex()));
// Store the dom index in the test generator
testGen.setDomIndex(local.getIndex());
_exp.translate(filterGen, testGen);
il.append(IRETURN);
testGen.stripAttributes(true);
testGen.setMaxLocals();
testGen.setMaxStack();
testGen.removeNOPs();
filterGen.addEmptyConstructor(ACC_PUBLIC);
filterGen.addMethod(testGen.getMethod());
getXSLTC().dumpClass(filterGen.getJavaClass());
}
/**
* Returns true if the predicate is a test for the existance of an
* element or attribute. All we have to do is to get the first node
* from the step, check if it is there, and then return true/false.
*/
public boolean isBooleanTest() {
return (_exp instanceof BooleanExpr);
}
/**
* Method to see if we can optimise the predicate by using a specialised
* iterator for expressions like '/foo/bar[@attr = $var]', which are
* very common in many stylesheets
*/
public boolean isNodeValueTest() {
if (!_canOptimize) return false;
return (getStep() != null && getCompareValue() != null);
}
/**
* Returns the step in an expression of the form 'step = value'.
* Null is returned if the expression is not of the right form.
* Optimization if off if null is returned.
*/
public Step getStep() {
// Returned cached value if called more than once
if (_step != null) {
return _step;
}
// Nothing to do if _exp is null
if (_exp == null) {
return null;
}
// Ignore if not equality expression
if (_exp instanceof EqualityExpr) {
EqualityExpr exp = (EqualityExpr)_exp;
Expression left = exp.getLeft();
Expression right = exp.getRight();
// Unwrap and set _step if appropriate
if (left instanceof CastExpr) {
left = ((CastExpr) left).getExpr();
}
if (left instanceof Step) {
_step = (Step) left;
}
// Unwrap and set _step if appropriate
if (right instanceof CastExpr) {
right = ((CastExpr)right).getExpr();
}
if (right instanceof Step) {
_step = (Step)right;
}
}
return _step;
}
/**
* Returns the value in an expression of the form 'step = value'.
* A value may be either a literal string or a variable whose
* type is string. Optimization if off if null is returned.
*/
public Expression getCompareValue() {
// Returned cached value if called more than once
if (_value != null) {
return _value;
}
// Nothing to to do if _exp is null
if (_exp == null) {
return null;
}
// Ignore if not an equality expression
if (_exp instanceof EqualityExpr) {
EqualityExpr exp = (EqualityExpr) _exp;
Expression left = exp.getLeft();
Expression right = exp.getRight();
// Return if left is literal string
if (left instanceof LiteralExpr) {
_value = left;
return _value;
}
// Return if left is a variable reference of type string
if (left instanceof VariableRefBase &&
left.getType() == Type.String)
{
_value = left;
return _value;
}
// Return if right is literal string
if (right instanceof LiteralExpr) {
_value = right;
return _value;
}
// Return if left is a variable reference whose type is string
if (right instanceof VariableRefBase &&
right.getType() == Type.String)
{
_value = right;
return _value;
}
}
return null;
}
/**
* Translate a predicate expression. This translation pushes
* two references on the stack: a reference to a newly created
* filter object and a reference to the predicate's closure.
*/
public void translateFilter(ClassGenerator classGen,
MethodGenerator methodGen)
{
final ConstantPoolGen cpg = classGen.getConstantPool();
final InstructionList il = methodGen.getInstructionList();
// Compile auxiliary class for filter
compileFilter(classGen, methodGen);
// Create new instance of filter
il.append(new NEW(cpg.addClass(_className)));
il.append(DUP);
il.append(new INVOKESPECIAL(cpg.addMethodref(_className,
"<init>", "()V")));
// Initialize closure variables
final int length = (_closureVars == null) ? 0 : _closureVars.size();
for (int i = 0; i < length; i++) {
VariableRefBase varRef = (VariableRefBase) _closureVars.get(i);
VariableBase var = varRef.getVariable();
Type varType = var.getType();
il.append(DUP);
// Find nearest closure implemented as an inner class
Closure variableClosure = _parentClosure;
while (variableClosure != null) {
if (variableClosure.inInnerClass()) break;
variableClosure = variableClosure.getParentClosure();
}
// Use getfield if in an inner class
if (variableClosure != null) {
il.append(ALOAD_0);
il.append(new GETFIELD(
cpg.addFieldref(variableClosure.getInnerClassName(),
var.getEscapedName(), varType.toSignature())));
}
else {
// Use a load of instruction if in translet class
il.append(var.loadInstruction());
}
// Store variable in new closure
il.append(new PUTFIELD(
cpg.addFieldref(_className, var.getEscapedName(),
varType.toSignature())));
}
}
/**
* Translate a predicate expression. If non of the optimizations apply
* then this translation pushes two references on the stack: a reference
* to a newly created filter object and a reference to the predicate's
* closure. See class <code>Step</code> for further details.
*/
public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
final ConstantPoolGen cpg = classGen.getConstantPool();
final InstructionList il = methodGen.getInstructionList();
if (_nthPositionFilter || _nthDescendant) {
_exp.translate(classGen, methodGen);
}
else if (isNodeValueTest() && (getParent() instanceof Step)) {
_value.translate(classGen, methodGen);
il.append(new CHECKCAST(cpg.addClass(STRING_CLASS)));
il.append(new PUSH(cpg, ((EqualityExpr)_exp).getOp()));
}
else {
translateFilter(classGen, methodGen);
}
}
}