code: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements. See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership. The ASF licenses this file
   * to you 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.
   */
  /*
   * $Id$
   */
  
  package org.apache.xalan.xsltc.compiler;
  
  import java.util.Enumeration;
  import java.util.Vector;
  
  import org.apache.bcel.generic.BranchHandle;
  import org.apache.bcel.generic.ConstantPoolGen;
  import org.apache.bcel.generic.GOTO;
  import org.apache.bcel.generic.IFGT;
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
  import org.apache.xalan.xsltc.compiler.util.ErrorMsg;
  import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
  import org.apache.xalan.xsltc.compiler.util.NodeSetType;
  import org.apache.xalan.xsltc.compiler.util.NodeType;
  import org.apache.xalan.xsltc.compiler.util.ReferenceType;
  import org.apache.xalan.xsltc.compiler.util.ResultTreeType;
  import org.apache.xalan.xsltc.compiler.util.Type;
  import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
  import org.apache.xalan.xsltc.compiler.util.Util;
  
  /**
   * @author Jacek Ambroziak
   * @author Santiago Pericas-Geertsen
   * @author Morten Jorgensen
   */
  final class ForEach extends Instruction {
  
      private Expression _select;
      private Type       _type;
  
      public void display(int indent) {
  	indent(indent);
  	Util.println("ForEach");
  	indent(indent + IndentIncrement);
  	Util.println("select " + _select.toString());
  	displayContents(indent + IndentIncrement);
      }
  		
      public void parseContents(Parser parser) {
  	_select = parser.parseExpression(this, "select", null);
  
  	parseChildren(parser);
  
          // make sure required attribute(s) have been set
          if (_select.isDummy()) {
  	    reportError(this, parser, ErrorMsg.REQUIRED_ATTR_ERR, "select");
          }
      }
  	
      public Type typeCheck(SymbolTable stable) throws TypeCheckError {
  	_type = _select.typeCheck(stable);
  
  	if (_type instanceof ReferenceType || _type instanceof NodeType) {
  	    _select = new CastExpr(_select, Type.NodeSet);
  	    typeCheckContents(stable);
  	    return Type.Void;
  	}
  	if (_type instanceof NodeSetType||_type instanceof ResultTreeType) {
  	    typeCheckContents(stable);
  	    return Type.Void;
  	}
  	throw new TypeCheckError(this);
      }
  
      public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  
  	// Save current node and current iterator on the stack
  	il.append(methodGen.loadCurrentNode());
  	il.append(methodGen.loadIterator());
  		
  	// Collect sort objects associated with this instruction
  	final Vector sortObjects = new Vector();
  	Enumeration children = elements();
  	while (children.hasMoreElements()) {
  	    final Object child = children.nextElement();
  	    if (child instanceof Sort) {
  		sortObjects.addElement(child);
  	    }
  	}
  
  	if ((_type != null) && (_type instanceof ResultTreeType)) {
  	    // Store existing DOM on stack - must be restored when loop is done
  	    il.append(methodGen.loadDOM());
  
  	    // <xsl:sort> cannot be applied to a result tree - issue warning
  	    if (sortObjects.size() > 0) {
  		ErrorMsg msg = new ErrorMsg(ErrorMsg.RESULT_TREE_SORT_ERR,this);
  		getParser().reportError(WARNING, msg);
  	    }
  
  	    // Put the result tree on the stack (DOM)
  	    _select.translate(classGen, methodGen);
  	    // Get an iterator for the whole DOM - excluding the root node
  	    _type.translateTo(classGen, methodGen, Type.NodeSet);
  	    // Store the result tree as the default DOM
  	    il.append(SWAP);
  	    il.append(methodGen.storeDOM());
  	}
  	else {
  	    // Compile node iterator
  	    if (sortObjects.size() > 0) {
  		Sort.translateSortIterator(classGen, methodGen,
  					   _select, sortObjects);
  	    }
  	    else {
  		_select.translate(classGen, methodGen);
  	    }
  
  	    if (_type instanceof ReferenceType == false) {
                  il.append(methodGen.loadContextNode());
                  il.append(methodGen.setStartNode());
  	    }
  	}
  
  
  	// Overwrite current iterator
  	il.append(methodGen.storeIterator());
  
  	// Give local variables (if any) default values before starting loop
  	initializeVariables(classGen, methodGen);
  
  	final BranchHandle nextNode = il.append(new GOTO(null));
  	final InstructionHandle loop = il.append(NOP);
  
  	translateContents(classGen, methodGen);
  		    
  	nextNode.setTarget(il.append(methodGen.loadIterator()));
  	il.append(methodGen.nextNode());
  	il.append(DUP);
  	il.append(methodGen.storeCurrentNode());
  	il.append(new IFGT(loop));
  
  	// Restore current DOM (if result tree was used instead for this loop)
  	if ((_type != null) && (_type instanceof ResultTreeType)) {
  	    il.append(methodGen.storeDOM());	    
  	}
  
  	// Restore current node and current iterator from the stack
  	il.append(methodGen.storeIterator());
  	il.append(methodGen.storeCurrentNode());
      }
  
      /**
       * The code that is generated by nested for-each loops can appear to some
       * JVMs as if it is accessing un-initialized variables. We must add some
       * code that pushes the default variable value on the stack and pops it
       * into the variable slot. This is done by the Variable.initialize()
       * method. The code that we compile for this loop looks like this:
       *
       *           initialize iterator
       *           initialize variables <-- HERE!!!
       *           goto   Iterate
       *  Loop:    :
       *           : (code for <xsl:for-each> contents)
       *           :
       *  Iterate: node = iterator.next();
       *           if (node != END) goto Loop
       */
      public void initializeVariables(ClassGenerator classGen,
  				   MethodGenerator methodGen) {
  	final int n = elementCount();
  	for (int i = 0; i < n; i++) {
  	    final Object child = getContents().elementAt(i);
  	    if (child instanceof Variable) {
  		Variable var = (Variable)child;
  		var.initialize(classGen, methodGen);
  	    }
  	}
      }
  
  }
  