processinginstructionpattern.java

java1.6众多例子参考

/*
 * 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: ProcessingInstructionPattern.java,v 1.2.4.1 2005/09/12 11:04:08 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import com.sun.org.apache.bcel.internal.generic.BranchHandle;
import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.GOTO;
import com.sun.org.apache.bcel.internal.generic.IFEQ;
import com.sun.org.apache.bcel.internal.generic.IF_ICMPEQ;
import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;
import com.sun.org.apache.bcel.internal.generic.INVOKEVIRTUAL;
import com.sun.org.apache.bcel.internal.generic.InstructionHandle;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.bcel.internal.generic.PUSH;
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.xml.internal.dtm.Axis;
import com.sun.org.apache.xml.internal.dtm.DTM;

/**
 * @author Morten Jorgensen
 */
final class ProcessingInstructionPattern extends StepPattern {

    private String _name = null;
    private boolean _typeChecked = false;

    /**
     * Handles calls with no parameter (current node is implicit parameter).
     */
    public ProcessingInstructionPattern(String name) {
	super(Axis.CHILD, DTM.PROCESSING_INSTRUCTION_NODE, null);
	_name = name;
	//if (_name.equals("*")) _typeChecked = true; no wildcard allowed!
    }

    /**
     *
     */
     public double getDefaultPriority() {
        return (_name != null) ? 0.0 : -0.5;       
     }
    public String toString() {
	if (_predicates == null)
	    return "processing-instruction("+_name+")";
	else
	    return "processing-instruction("+_name+")"+_predicates;
    }

    public void reduceKernelPattern() {
	_typeChecked = true;
    }

    public boolean isWildcard() {
	return false;
    }

    public Type typeCheck(SymbolTable stable) throws TypeCheckError {
	if (hasPredicates()) {
	    // Type check all the predicates (e -> position() = e)
	    final int n = _predicates.size();
	    for (int i = 0; i < n; i++) {
		final Predicate pred = (Predicate)_predicates.elementAt(i);
		pred.typeCheck(stable);
	    }
	}
	return Type.NodeSet;
    }

    public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
	final ConstantPoolGen cpg = classGen.getConstantPool();
	final InstructionList il = methodGen.getInstructionList();

	// context node is on the stack
	int gname = cpg.addInterfaceMethodref(DOM_INTF,
					      "getNodeName",
					      "(I)Ljava/lang/String;");
	int cmp = cpg.addMethodref(STRING_CLASS,
				   "equals", "(Ljava/lang/Object;)Z");

	// Push current node on the stack
	il.append(methodGen.loadCurrentNode());
	il.append(SWAP);

	// Overwrite current node with matching node
	il.append(methodGen.storeCurrentNode());

	// If pattern not reduced then check kernel
	if (!_typeChecked) {
	    il.append(methodGen.loadCurrentNode());
	    final int getType = cpg.addInterfaceMethodref(DOM_INTF,
							  "getExpandedTypeID",
                                                          "(I)I");
	    il.append(methodGen.loadDOM());
	    il.append(methodGen.loadCurrentNode());
	    il.append(new INVOKEINTERFACE(getType, 2));
	    il.append(new PUSH(cpg, DTM.PROCESSING_INSTRUCTION_NODE));
	    _falseList.add(il.append(new IF_ICMPEQ(null)));
	}

	// Load the requested processing instruction name
	il.append(new PUSH(cpg, _name));
	// Load the current processing instruction's name
	il.append(methodGen.loadDOM());
	il.append(methodGen.loadCurrentNode());
	il.append(new INVOKEINTERFACE(gname, 2));
	// Compare the two strings
	il.append(new INVOKEVIRTUAL(cmp));
	_falseList.add(il.append(new IFEQ(null)));
		
	// Compile the expressions within the predicates
	if (hasPredicates()) {
	    final int n = _predicates.size();
	    for (int i = 0; i < n; i++) {
		Predicate pred = (Predicate)_predicates.elementAt(i);
		Expression exp = pred.getExpr();
		exp.translateDesynthesized(classGen, methodGen);
		_trueList.append(exp._trueList);
		_falseList.append(exp._falseList);
	    }
	}

	// Backpatch true list and restore current iterator/node
	InstructionHandle restore;
	restore = il.append(methodGen.storeCurrentNode());
	backPatchTrueList(restore);
	BranchHandle skipFalse = il.append(new GOTO(null));

	// Backpatch false list and restore current iterator/node
	restore = il.append(methodGen.storeCurrentNode());
	backPatchFalseList(restore);
	_falseList.add(il.append(new GOTO(null)));

	// True list falls through
	skipFalse.setTarget(il.append(NOP));
    }
}