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The Step.java Java example source code
/*
* reserved comment block
* DO NOT REMOVE OR ALTER!
*/
/*
* Copyright 2001-2005 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: Step.java,v 1.6 2006/06/06 22:34:34 spericas Exp $
*/
package com.sun.org.apache.xalan.internal.xsltc.compiler;
import java.util.Vector;
import com.sun.org.apache.bcel.internal.generic.ALOAD;
import com.sun.org.apache.bcel.internal.generic.ASTORE;
import com.sun.org.apache.bcel.internal.generic.CHECKCAST;
import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.ICONST;
import com.sun.org.apache.bcel.internal.generic.ILOAD;
import com.sun.org.apache.bcel.internal.generic.ISTORE;
import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;
import com.sun.org.apache.bcel.internal.generic.INVOKESPECIAL;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.bcel.internal.generic.LocalVariableGen;
import com.sun.org.apache.bcel.internal.generic.NEW;
import com.sun.org.apache.bcel.internal.generic.PUSH;
import com.sun.org.apache.xalan.internal.xsltc.DOM;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Util;
import com.sun.org.apache.xml.internal.dtm.Axis;
import com.sun.org.apache.xml.internal.dtm.DTM;
/**
* @author Jacek Ambroziak
* @author Santiago Pericas-Geertsen
* @author Morten Jorgensen
*/
final class Step extends RelativeLocationPath {
/**
* This step's axis as defined in class Axis.
*/
private int _axis;
/**
* A vector of predicates (filters) defined on this step - may be null
*/
private Vector _predicates;
/**
* Some simple predicates can be handled by this class (and not by the
* Predicate class) and will be removed from the above vector as they are
* handled. We use this boolean to remember if we did have any predicates.
*/
private boolean _hadPredicates = false;
/**
* Type of the node test.
*/
private int _nodeType;
public Step(int axis, int nodeType, Vector predicates) {
_axis = axis;
_nodeType = nodeType;
_predicates = predicates;
}
/**
* Set the parser for this element and all child predicates
*/
public void setParser(Parser parser) {
super.setParser(parser);
if (_predicates != null) {
final int n = _predicates.size();
for (int i = 0; i < n; i++) {
final Predicate exp = (Predicate)_predicates.elementAt(i);
exp.setParser(parser);
exp.setParent(this);
}
}
}
/**
* Define the axis (defined in Axis class) for this step
*/
public int getAxis() {
return _axis;
}
/**
* Get the axis (defined in Axis class) for this step
*/
public void setAxis(int axis) {
_axis = axis;
}
/**
* Returns the node-type for this step
*/
public int getNodeType() {
return _nodeType;
}
/**
* Returns the vector containing all predicates for this step.
*/
public Vector getPredicates() {
return _predicates;
}
/**
* Returns the vector containing all predicates for this step.
*/
public void addPredicates(Vector predicates) {
if (_predicates == null) {
_predicates = predicates;
}
else {
_predicates.addAll(predicates);
}
}
/**
* Returns 'true' if this step has a parent pattern.
* This method will return 'false' if this step occurs on its own under
* an element like <xsl:for-each> or .
*/
private boolean hasParentPattern() {
final SyntaxTreeNode parent = getParent();
return (parent instanceof ParentPattern ||
parent instanceof ParentLocationPath ||
parent instanceof UnionPathExpr ||
parent instanceof FilterParentPath);
}
/**
* Returns 'true' if this step has a parent location path.
*/
private boolean hasParentLocationPath() {
return getParent() instanceof ParentLocationPath;
}
/**
* Returns 'true' if this step has any predicates
*/
private boolean hasPredicates() {
return _predicates != null && _predicates.size() > 0;
}
/**
* Returns 'true' if this step is used within a predicate
*/
private boolean isPredicate() {
SyntaxTreeNode parent = this;
while (parent != null) {
parent = parent.getParent();
if (parent instanceof Predicate) return true;
}
return false;
}
/**
* True if this step is the abbreviated step '.'
*/
public boolean isAbbreviatedDot() {
return _nodeType == NodeTest.ANODE && _axis == Axis.SELF;
}
/**
* True if this step is the abbreviated step '..'
*/
public boolean isAbbreviatedDDot() {
return _nodeType == NodeTest.ANODE && _axis == Axis.PARENT;
}
/**
* Type check this step. The abbreviated steps '.' and '@attr' are
* assigned type node if they have no predicates. All other steps
* have type node-set.
*/
public Type typeCheck(SymbolTable stable) throws TypeCheckError {
// Save this value for later - important for testing for special
// combinations of steps and patterns than can be optimised
_hadPredicates = hasPredicates();
// Special case for '.'
// in the case where '.' has a context such as book/.
// or .[false()] we can not optimize the nodeset to a single node.
if (isAbbreviatedDot()) {
_type = (hasParentPattern() || hasPredicates() || hasParentLocationPath()) ?
Type.NodeSet : Type.Node;
}
else {
_type = Type.NodeSet;
}
// Type check all predicates (expressions applied to the step)
if (_predicates != null) {
final int n = _predicates.size();
for (int i = 0; i < n; i++) {
final Expression pred = (Expression)_predicates.elementAt(i);
pred.typeCheck(stable);
}
}
// Return either Type.Node or Type.NodeSet
return _type;
}
/**
* Translate a step by pushing the appropriate iterator onto the stack.
* The abbreviated steps '.' and '@attr' do not create new iterators
* if they are not part of a LocationPath and have no filters.
* In these cases a node index instead of an iterator is pushed
* onto the stack.
*/
public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
translateStep(classGen, methodGen, hasPredicates() ? _predicates.size() - 1 : -1);
}
private void translateStep(ClassGenerator classGen,
MethodGenerator methodGen,
int predicateIndex) {
final ConstantPoolGen cpg = classGen.getConstantPool();
final InstructionList il = methodGen.getInstructionList();
if (predicateIndex >= 0) {
translatePredicates(classGen, methodGen, predicateIndex);
} else {
int star = 0;
String name = null;
final XSLTC xsltc = getParser().getXSLTC();
if (_nodeType >= DTM.NTYPES) {
final Vector ni = xsltc.getNamesIndex();
name = (String)ni.elementAt(_nodeType-DTM.NTYPES);
star = name.lastIndexOf('*');
}
// If it is an attribute, but not '@*', '@pre:*' or '@node()',
// and has no parent
if (_axis == Axis.ATTRIBUTE && _nodeType != NodeTest.ATTRIBUTE
&& _nodeType != NodeTest.ANODE && !hasParentPattern()
&& star == 0)
{
int iter = cpg.addInterfaceMethodref(DOM_INTF,
"getTypedAxisIterator",
"(II)"+NODE_ITERATOR_SIG);
il.append(methodGen.loadDOM());
il.append(new PUSH(cpg, Axis.ATTRIBUTE));
il.append(new PUSH(cpg, _nodeType));
il.append(new INVOKEINTERFACE(iter, 3));
return;
}
SyntaxTreeNode parent = getParent();
// Special case for '.'
if (isAbbreviatedDot()) {
if (_type == Type.Node) {
// Put context node on stack if using Type.Node
il.append(methodGen.loadContextNode());
}
else {
if (parent instanceof ParentLocationPath){
// Wrap the context node in a singleton iterator if not.
int init = cpg.addMethodref(SINGLETON_ITERATOR,
"<init>",
"("+NODE_SIG+")V");
il.append(new NEW(cpg.addClass(SINGLETON_ITERATOR)));
il.append(DUP);
il.append(methodGen.loadContextNode());
il.append(new INVOKESPECIAL(init));
} else {
// DOM.getAxisIterator(int axis);
int git = cpg.addInterfaceMethodref(DOM_INTF,
"getAxisIterator",
"(I)"+NODE_ITERATOR_SIG);
il.append(methodGen.loadDOM());
il.append(new PUSH(cpg, _axis));
il.append(new INVOKEINTERFACE(git, 2));
}
}
return;
}
// Special case for /foo/*/bar
if ((parent instanceof ParentLocationPath) &&
(parent.getParent() instanceof ParentLocationPath)) {
if ((_nodeType == NodeTest.ELEMENT) && (!_hadPredicates)) {
_nodeType = NodeTest.ANODE;
}
}
// "ELEMENT" or "*" or "@*" or ".." or "@attr" with a parent.
switch (_nodeType) {
case NodeTest.ATTRIBUTE:
_axis = Axis.ATTRIBUTE;
case NodeTest.ANODE:
// DOM.getAxisIterator(int axis);
int git = cpg.addInterfaceMethodref(DOM_INTF,
"getAxisIterator",
"(I)"+NODE_ITERATOR_SIG);
il.append(methodGen.loadDOM());
il.append(new PUSH(cpg, _axis));
il.append(new INVOKEINTERFACE(git, 2));
break;
default:
if (star > 1) {
final String namespace;
if (_axis == Axis.ATTRIBUTE)
namespace = name.substring(0,star-2);
else
namespace = name.substring(0,star-1);
final int nsType = xsltc.registerNamespace(namespace);
final int ns = cpg.addInterfaceMethodref(DOM_INTF,
"getNamespaceAxisIterator",
"(II)"+NODE_ITERATOR_SIG);
il.append(methodGen.loadDOM());
il.append(new PUSH(cpg, _axis));
il.append(new PUSH(cpg, nsType));
il.append(new INVOKEINTERFACE(ns, 3));
break;
}
case NodeTest.ELEMENT:
// DOM.getTypedAxisIterator(int axis, int type);
final int ty = cpg.addInterfaceMethodref(DOM_INTF,
"getTypedAxisIterator",
"(II)"+NODE_ITERATOR_SIG);
// Get the typed iterator we're after
il.append(methodGen.loadDOM());
il.append(new PUSH(cpg, _axis));
il.append(new PUSH(cpg, _nodeType));
il.append(new INVOKEINTERFACE(ty, 3));
break;
}
}
}
/**
* Translate a sequence of predicates. Each predicate is translated
* by constructing an instance of <code>CurrentNodeListIterator
* which is initialized from another iterator (recursive call),
* a filter and a closure (call to translate on the predicate) and "this".
*/
public void translatePredicates(ClassGenerator classGen,
MethodGenerator methodGen,
int predicateIndex) {
final ConstantPoolGen cpg = classGen.getConstantPool();
final InstructionList il = methodGen.getInstructionList();
int idx = 0;
if (predicateIndex < 0) {
translateStep(classGen, methodGen, predicateIndex);
}
else {
final Predicate predicate = (Predicate) _predicates.get(predicateIndex--);
// Special case for predicates that can use the NodeValueIterator
// instead of an auxiliary class. Certain path/predicates pairs
// are translated into a base path, on top of which we place a
// node value iterator that tests for the desired value:
// foo[@attr = 'str'] -> foo/@attr + test(value='str')
// foo[bar = 'str'] -> foo/bar + test(value='str')
// foo/bar[. = 'str'] -> foo/bar + test(value='str')
if (predicate.isNodeValueTest()) {
Step step = predicate.getStep();
il.append(methodGen.loadDOM());
// If the predicate's Step is simply '.' we translate this Step
// and place the node test on top of the resulting iterator
if (step.isAbbreviatedDot()) {
translateStep(classGen, methodGen, predicateIndex);
il.append(new ICONST(DOM.RETURN_CURRENT));
}
// Otherwise we create a parent location path with this Step and
// the predicates Step, and place the node test on top of that
else {
ParentLocationPath path = new ParentLocationPath(this, step);
_parent = step._parent = path; // Force re-parenting
try {
path.typeCheck(getParser().getSymbolTable());
}
catch (TypeCheckError e) { }
translateStep(classGen, methodGen, predicateIndex);
path.translateStep(classGen, methodGen);
il.append(new ICONST(DOM.RETURN_PARENT));
}
predicate.translate(classGen, methodGen);
idx = cpg.addInterfaceMethodref(DOM_INTF,
GET_NODE_VALUE_ITERATOR,
GET_NODE_VALUE_ITERATOR_SIG);
il.append(new INVOKEINTERFACE(idx, 5));
}
// Handle '//*[n]' expression
else if (predicate.isNthDescendant()) {
il.append(methodGen.loadDOM());
// il.append(new ICONST(NodeTest.ELEMENT));
il.append(new PUSH(cpg, predicate.getPosType()));
predicate.translate(classGen, methodGen);
il.append(new ICONST(0));
idx = cpg.addInterfaceMethodref(DOM_INTF,
"getNthDescendant",
"(IIZ)"+NODE_ITERATOR_SIG);
il.append(new INVOKEINTERFACE(idx, 4));
}
// Handle 'elem[n]' expression
else if (predicate.isNthPositionFilter()) {
idx = cpg.addMethodref(NTH_ITERATOR_CLASS,
"<init>",
"("+NODE_ITERATOR_SIG+"I)V");
// Backwards branches are prohibited if an uninitialized object
// is on the stack by section 4.9.4 of the JVM Specification,
// 2nd Ed. We don't know whether this code might contain
// backwards branches, so we mustn't create the new object until
// after we've created the suspect arguments to its constructor.
// Instead we calculate the values of the arguments to the
// constructor first, store them in temporary variables, create
// the object and reload the arguments from the temporaries to
// avoid the problem.
translatePredicates(classGen, methodGen, predicateIndex); // recursive call
LocalVariableGen iteratorTemp
= methodGen.addLocalVariable("step_tmp1",
Util.getJCRefType(NODE_ITERATOR_SIG),
null, null);
iteratorTemp.setStart(
il.append(new ASTORE(iteratorTemp.getIndex())));
predicate.translate(classGen, methodGen);
LocalVariableGen predicateValueTemp
= methodGen.addLocalVariable("step_tmp2",
Util.getJCRefType("I"),
null, null);
predicateValueTemp.setStart(
il.append(new ISTORE(predicateValueTemp.getIndex())));
il.append(new NEW(cpg.addClass(NTH_ITERATOR_CLASS)));
il.append(DUP);
iteratorTemp.setEnd(
il.append(new ALOAD(iteratorTemp.getIndex())));
predicateValueTemp.setEnd(
il.append(new ILOAD(predicateValueTemp.getIndex())));
il.append(new INVOKESPECIAL(idx));
}
else {
idx = cpg.addMethodref(CURRENT_NODE_LIST_ITERATOR,
"<init>",
"("
+ NODE_ITERATOR_SIG
+ CURRENT_NODE_LIST_FILTER_SIG
+ NODE_SIG
+ TRANSLET_SIG
+ ")V");
// Backwards branches are prohibited if an uninitialized object
// is on the stack by section 4.9.4 of the JVM Specification,
// 2nd Ed. We don't know whether this code might contain
// backwards branches, so we mustn't create the new object until
// after we've created the suspect arguments to its constructor.
// Instead we calculate the values of the arguments to the
// constructor first, store them in temporary variables, create
// the object and reload the arguments from the temporaries to
// avoid the problem.
translatePredicates(classGen, methodGen, predicateIndex); // recursive call
LocalVariableGen iteratorTemp
= methodGen.addLocalVariable("step_tmp1",
Util.getJCRefType(NODE_ITERATOR_SIG),
null, null);
iteratorTemp.setStart(
il.append(new ASTORE(iteratorTemp.getIndex())));
predicate.translateFilter(classGen, methodGen);
LocalVariableGen filterTemp
= methodGen.addLocalVariable("step_tmp2",
Util.getJCRefType(CURRENT_NODE_LIST_FILTER_SIG),
null, null);
filterTemp.setStart(
il.append(new ASTORE(filterTemp.getIndex())));
// create new CurrentNodeListIterator
il.append(new NEW(cpg.addClass(CURRENT_NODE_LIST_ITERATOR)));
il.append(DUP);
iteratorTemp.setEnd(
il.append(new ALOAD(iteratorTemp.getIndex())));
filterTemp.setEnd(il.append(new ALOAD(filterTemp.getIndex())));
il.append(methodGen.loadCurrentNode());
il.append(classGen.loadTranslet());
if (classGen.isExternal()) {
final String className = classGen.getClassName();
il.append(new CHECKCAST(cpg.addClass(className)));
}
il.append(new INVOKESPECIAL(idx));
}
}
}
/**
* Returns a string representation of this step.
*/
public String toString() {
final StringBuffer buffer = new StringBuffer("step(\"");
buffer.append(Axis.getNames(_axis)).append("\", ").append(_nodeType);
if (_predicates != null) {
final int n = _predicates.size();
for (int i = 0; i < n; i++) {
final Predicate pred = (Predicate)_predicates.elementAt(i);
buffer.append(", ").append(pred.toString());
}
}
return buffer.append(')').toString();
}
}
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