1 /*
   2  * reserved comment block
   3  * DO NOT REMOVE OR ALTER!
   4  */
   5 /*
   6  * Copyright 2001-2004 The Apache Software Foundation.
   7  *
   8  * Licensed under the Apache License, Version 2.0 (the "License");
   9  * you may not use this file except in compliance with the License.
  10  * You may obtain a copy of the License at
  11  *
  12  *     http://www.apache.org/licenses/LICENSE-2.0
  13  *
  14  * Unless required by applicable law or agreed to in writing, software
  15  * distributed under the License is distributed on an "AS IS" BASIS,
  16  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  17  * See the License for the specific language governing permissions and
  18  * limitations under the License.
  19  */
  20 /*
  21  * $Id: UnionPathExpr.java,v 1.2.4.1 2005/09/12 11:34:14 pvedula Exp $
  22  */
  23 
  24 package com.sun.org.apache.xalan.internal.xsltc.compiler;
  25 
  26 import java.util.Vector;
  27 
  28 import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
  29 import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;
  30 import com.sun.org.apache.bcel.internal.generic.INVOKESPECIAL;
  31 import com.sun.org.apache.bcel.internal.generic.INVOKEVIRTUAL;
  32 import com.sun.org.apache.bcel.internal.generic.InstructionList;
  33 import com.sun.org.apache.bcel.internal.generic.NEW;
  34 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
  35 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
  36 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
  37 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
  38 import com.sun.org.apache.xml.internal.dtm.Axis;
  39 import com.sun.org.apache.xml.internal.dtm.DTM;
  40 
  41 /**
  42  * @author Jacek Ambroziak
  43  * @author Santiago Pericas-Geertsen
  44  */
  45 final class UnionPathExpr extends Expression {
  46 
  47     private final Expression _pathExpr;
  48     private final Expression _rest;
  49     private boolean _reverse = false;
  50 
  51     // linearization for top level UnionPathExprs
  52     private Expression[] _components;
  53 
  54     public UnionPathExpr(Expression pathExpr, Expression rest) {
  55         _pathExpr = pathExpr;
  56         _rest     = rest;
  57     }
  58 
  59     public void setParser(Parser parser) {
  60         super.setParser(parser);
  61         // find all expressions in this Union
  62         final Vector components = new Vector();
  63         flatten(components);
  64         final int size = components.size();
  65         _components = (Expression[])components.toArray(new Expression[size]);
  66         for (int i = 0; i < size; i++) {
  67             _components[i].setParser(parser);
  68             _components[i].setParent(this);
  69             if (_components[i] instanceof Step) {
  70                 final Step step = (Step)_components[i];
  71                 final int axis = step.getAxis();
  72                 final int type = step.getNodeType();
  73                 // Put attribute iterators first
  74                 if ((axis == Axis.ATTRIBUTE) || (type == DTM.ATTRIBUTE_NODE)) {
  75                     _components[i] = _components[0];
  76                     _components[0] = step;
  77                 }
  78                 // Check if the union contains a reverse iterator
  79         if (Axis.isReverse(axis)) _reverse = true;
  80             }
  81         }
  82         // No need to reverse anything if another expression lies on top of this
  83         if (getParent() instanceof Expression) _reverse = false;
  84     }
  85 
  86     public Type typeCheck(SymbolTable stable) throws TypeCheckError {
  87         final int length = _components.length;
  88         for (int i = 0; i < length; i++) {
  89             if (_components[i].typeCheck(stable) != Type.NodeSet) {
  90                 _components[i] = new CastExpr(_components[i], Type.NodeSet);
  91             }
  92         }
  93         return _type = Type.NodeSet;
  94     }
  95 
  96     public String toString() {
  97         return "union(" + _pathExpr + ", " + _rest + ')';
  98     }
  99 
 100     private void flatten(Vector components) {
 101         components.addElement(_pathExpr);
 102         if (_rest != null) {
 103             if (_rest instanceof UnionPathExpr) {
 104                 ((UnionPathExpr)_rest).flatten(components);
 105             }
 106             else {
 107                 components.addElement(_rest);
 108             }
 109         }
 110     }
 111 
 112     public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
 113         final ConstantPoolGen cpg = classGen.getConstantPool();
 114         final InstructionList il = methodGen.getInstructionList();
 115 
 116         final int init = cpg.addMethodref(UNION_ITERATOR_CLASS,
 117                                           "<init>",
 118                                           "("+DOM_INTF_SIG+")V");
 119         final int iter = cpg.addMethodref(UNION_ITERATOR_CLASS,
 120                                           ADD_ITERATOR,
 121                                           ADD_ITERATOR_SIG);
 122 
 123         // Create the UnionIterator and leave it on the stack
 124         il.append(new NEW(cpg.addClass(UNION_ITERATOR_CLASS)));
 125         il.append(DUP);
 126         il.append(methodGen.loadDOM());
 127         il.append(new INVOKESPECIAL(init));
 128 
 129         // Add the various iterators to the UnionIterator
 130         final int length = _components.length;
 131         for (int i = 0; i < length; i++) {
 132             _components[i].translate(classGen, methodGen);
 133             il.append(new INVOKEVIRTUAL(iter));
 134         }
 135 
 136         // Order the iterator only if strictly needed
 137         if (_reverse) {
 138             final int order = cpg.addInterfaceMethodref(DOM_INTF,
 139                                                         ORDER_ITERATOR,
 140                                                         ORDER_ITERATOR_SIG);
 141             il.append(methodGen.loadDOM());
 142             il.append(SWAP);
 143             il.append(methodGen.loadContextNode());
 144             il.append(new INVOKEINTERFACE(order, 3));
 145 
 146         }
 147     }
 148 }