step.java

java1.6众多例子参考

/*
 * 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 <xsl:apply-templates>.
     */
    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) {
	final ConstantPoolGen cpg = classGen.getConstantPool();
	final InstructionList il = methodGen.getInstructionList();

	if (hasPredicates()) {
	    translatePredicates(classGen, methodGen);
	} 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));