AncestorPattern.java

/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
/*
 * 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: AncestorPattern.java,v 1.2.4.1 2005/09/01 09:19:41 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.IFLT;
import com.sun.org.apache.bcel.internal.generic.ILOAD;
import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;
import com.sun.org.apache.bcel.internal.generic.ISTORE;
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.LocalVariableGen;
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;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 * @author Erwin Bolwidt <ejb@klomp.org>
 */
final class AncestorPattern extends RelativePathPattern {

    private final Pattern _left;        // may be null
    private final RelativePathPattern _right;
    private InstructionHandle _loop;

    public AncestorPattern(RelativePathPattern right) {
        this(null, right);
    }

    public AncestorPattern(Pattern left, RelativePathPattern right) {
        _left = left;
        (_right = right).setParent(this);
        if (left != null) {
            left.setParent(this);
        }
    }

    public InstructionHandle getLoopHandle() {
        return _loop;
    }

    public void setParser(Parser parser) {
        super.setParser(parser);
        if (_left != null) {
            _left.setParser(parser);
        }
        _right.setParser(parser);
    }

    public boolean isWildcard() {
        //!!! can be wildcard
        return false;
    }

    public StepPattern getKernelPattern() {
        return _right.getKernelPattern();
    }

    public void reduceKernelPattern() {
        _right.reduceKernelPattern();
    }

    public Type typeCheck(SymbolTable stable) throws TypeCheckError {
        if (_left != null) {
            _left.typeCheck(stable);
        }
        return _right.typeCheck(stable);
    }

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

        /*
         * The scope of this local var must be the entire method since
         * a another pattern may decide to jump back into the loop
         */
        final LocalVariableGen local =
            methodGen.addLocalVariable2("app", Util.getJCRefType(NODE_SIG),
                                        il.getEnd());

        final com.sun.org.apache.bcel.internal.generic.Instruction loadLocal =
            new ILOAD(local.getIndex());
        final com.sun.org.apache.bcel.internal.generic.Instruction storeLocal =
            new ISTORE(local.getIndex());

        if (_right instanceof StepPattern) {
            il.append(DUP);
            il.append(storeLocal);
            _right.translate(classGen, methodGen);
            il.append(methodGen.loadDOM());
            il.append(loadLocal);
        }
        else {
            _right.translate(classGen, methodGen);

            if (_right instanceof AncestorPattern) {
                il.append(methodGen.loadDOM());
                il.append(SWAP);
            }
        }

        if (_left != null) {
            final int getParent = cpg.addInterfaceMethodref(DOM_INTF,
                                                            GET_PARENT,
                                                            GET_PARENT_SIG);
            parent = il.append(new INVOKEINTERFACE(getParent, 2));

            il.append(DUP);
            il.append(storeLocal);
            _falseList.add(il.append(new IFLT(null)));
            il.append(loadLocal);

            _left.translate(classGen, methodGen);

            final SyntaxTreeNode p = getParent();
            if (p == null || p instanceof Instruction ||
                p instanceof TopLevelElement)
            {
                // do nothing
            }
            else {
                il.append(loadLocal);
            }

            final BranchHandle exit = il.append(new GOTO(null));
            _loop = il.append(methodGen.loadDOM());
            il.append(loadLocal);
            local.setEnd(_loop);
            il.append(new GOTO(parent));
            exit.setTarget(il.append(NOP));
            _left.backPatchFalseList(_loop);

            _trueList.append(_left._trueList);
        }
        else {
            il.append(POP2);
        }

        /*
         * If _right is an ancestor pattern, backpatch this pattern's false
         * list to the loop that searches for more ancestors.
         */
        if (_right instanceof AncestorPattern) {
            final AncestorPattern ancestor = (AncestorPattern) _right;
            _falseList.backPatch(ancestor.getLoopHandle());    // clears list
        }

        _trueList.append(_right._trueList);
        _falseList.append(_right._falseList);
    }

    public String toString() {
        return "AncestorPattern(" + _left + ", " + _right + ')';
    }
}