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.Vector;
  
  import org.apache.bcel.generic.ALOAD;
  import org.apache.bcel.generic.ASTORE;
  import org.apache.bcel.generic.ConstantPoolGen;
  import org.apache.bcel.generic.ILOAD;
  import org.apache.bcel.generic.INVOKESPECIAL;
  import org.apache.bcel.generic.ISTORE;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.bcel.generic.LocalVariableGen;
  import org.apache.bcel.generic.NEW;
  import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
  import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
  import org.apache.xalan.xsltc.compiler.util.NodeSetType;
  import org.apache.xalan.xsltc.compiler.util.ReferenceType;
  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
   */
  class FilterExpr extends Expression {
      
      /**
       * Primary expression of this filter. I.e., 'e' in '(e)[p1]...[pn]'.
       */
      private Expression   _primary;
      
      /**
       * Array of predicates in '(e)[p1]...[pn]'.
       */
      private final Vector _predicates;
  
      public FilterExpr(Expression primary, Vector predicates) {
  	_primary = primary;
  	_predicates = predicates;
  	primary.setParent(this);
      }
  
      protected Expression getExpr() {
  	if (_primary instanceof CastExpr)
  	    return ((CastExpr)_primary).getExpr();
  	else
  	    return _primary;
      }
  
      public void setParser(Parser parser) {
  	super.setParser(parser);
  	_primary.setParser(parser);
  	if (_predicates != null) {
  	    final int n = _predicates.size();
  	    for (int i = 0; i < n; i++) {
  		final Expression exp = (Expression)_predicates.elementAt(i);
  		exp.setParser(parser);
  		exp.setParent(this);
  	    }
  	}
      }
      
      public String toString() {
  	return "filter-expr(" + _primary + ", " + _predicates + ")";
      }
  
      /**
       * Type check a FilterParentPath. If the filter is not a node-set add a 
       * cast to node-set only if it is of reference type. This type coercion 
       * is needed for expressions like $x where $x is a parameter reference.
       * All optimizations are turned off before type checking underlying
       * predicates.
       */
      public Type typeCheck(SymbolTable stable) throws TypeCheckError {
  	Type ptype = _primary.typeCheck(stable);
          boolean canOptimize = _primary instanceof KeyCall;
  
  	if (ptype instanceof NodeSetType == false) {
  	    if (ptype instanceof ReferenceType)  {
  		_primary = new CastExpr(_primary, Type.NodeSet);
  	    }
  	    else {
  		throw new TypeCheckError(this);
  	    }
  	}
  
          // Type check predicates and turn all optimizations off if appropriate
  	int n = _predicates.size();
  	for (int i = 0; i < n; i++) {
  	    Predicate pred = (Predicate) _predicates.elementAt(i);
  
              if (!canOptimize) {
                  pred.dontOptimize();
              }
  	    pred.typeCheck(stable);
  	}
  	return _type = Type.NodeSet;	
      }
  	
      /**
       * Translate a filter expression by pushing the appropriate iterator
       * onto the stack.
       */
      public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
  	if (_predicates.size() > 0) {
  	    translatePredicates(classGen, methodGen);
  	}
  	else {
  	    _primary.translate(classGen, methodGen);
  	}
      }
  
      /**
       * Translate a sequence of predicates. Each predicate is translated 
       * by constructing an instance of <code>CurrentNodeListIterator</code> 
       * which is initialized from another iterator (recursive call), a 
       * filter and a closure (call to translate on the predicate) and "this". 
       */
      public void translatePredicates(ClassGenerator classGen,
  				    MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  
          // If not predicates left, translate primary expression
  	if (_predicates.size() == 0) {
  	    translate(classGen, methodGen);
  	} else {
              // Remove the next predicate to be translated
              Predicate predicate = (Predicate)_predicates.lastElement();
              _predicates.remove(predicate);
  
              // Translate the rest of the predicates from right to left
              translatePredicates(classGen, methodGen);
  
              if (predicate.isNthPositionFilter()) {
                  int nthIteratorIdx = cpg.addMethodref(NTH_ITERATOR_CLASS,
                                         "<init>",
                                         "("+NODE_ITERATOR_SIG+"I)V");
  
                  // Backwards branches are prohibited if an uninitialized object
                  // is on the stack by section 4.9.4 of the JVM Specification,
                  // 2nd Ed.  We don't know whether this code might contain
                  // backwards branches, so we mustn't create the new object unti
  
                  // after we've created the suspect arguments to its constructor
  
                  // Instead we calculate the values of the arguments to the
                  // constructor first, store them in temporary variables, create
                  // the object and reload the arguments from the temporaries to
                  // avoid the problem.
                  LocalVariableGen iteratorTemp
                          = methodGen.addLocalVariable("filter_expr_tmp1",
                                           Util.getJCRefType(NODE_ITERATOR_SIG),
                                           null, null);
                  iteratorTemp.setStart(
                          il.append(new ASTORE(iteratorTemp.getIndex())));
  
                  predicate.translate(classGen, methodGen);
                  LocalVariableGen predicateValueTemp
                          = methodGen.addLocalVariable("filter_expr_tmp2",
                                           Util.getJCRefType("I"),
                                           null, null);
                  predicateValueTemp.setStart(
                          il.append(new ISTORE(predicateValueTemp.getIndex())));
  
                  il.append(new NEW(cpg.addClass(NTH_ITERATOR_CLASS)));
                  il.append(DUP);
                  iteratorTemp.setEnd(
                          il.append(new ALOAD(iteratorTemp.getIndex())));
                  predicateValueTemp.setEnd(
                          il.append(new ILOAD(predicateValueTemp.getIndex())));
                  il.append(new INVOKESPECIAL(nthIteratorIdx));
              } else {
                  // Translate predicates from right to left
                  final int initCNLI =
                                   cpg.addMethodref(CURRENT_NODE_LIST_ITERATOR,
                                                   "<init>",
                                                   "("+NODE_ITERATOR_SIG+"Z"+
                                                   CURRENT_NODE_LIST_FILTER_SIG +
                                                   NODE_SIG+TRANSLET_SIG+")V");
  
                  // Backwards branches are prohibited if an uninitialized object
                  // is on the stack by section 4.9.4 of the JVM Specification,
                  // 2nd Ed.  We don't know whether this code might contain
                  // backwards branches, so we mustn't create the new object
                  // until after we've created the suspect arguments to its
                  // constructor.  Instead we calculate the values of the
                  // arguments to the constructor first, store them in temporary
                  // variables, create the object and reload the arguments from
                  // the temporaries to avoid the problem.
  
  
                  LocalVariableGen nodeIteratorTemp =
                      methodGen.addLocalVariable("filter_expr_tmp1",
                                             Util.getJCRefType(NODE_ITERATOR_SIG),
                                             null, null);
                  nodeIteratorTemp.setStart(
                          il.append(new ASTORE(nodeIteratorTemp.getIndex())));
  
                  predicate.translate(classGen, methodGen);
                  LocalVariableGen filterTemp =
                      methodGen.addLocalVariable("filter_expr_tmp2",
                                Util.getJCRefType(CURRENT_NODE_LIST_FILTER_SIG),
                                null, null);
                  filterTemp.setStart(
                          il.append(new ASTORE(filterTemp.getIndex())));
  
                  // Create a CurrentNodeListIterator
                  il.append(new NEW(cpg.addClass(CURRENT_NODE_LIST_ITERATOR)));
                  il.append(DUP);
              
                  // Initialize CurrentNodeListIterator
                  nodeIteratorTemp.setEnd(
                          il.append(new ALOAD(nodeIteratorTemp.getIndex())));
                  il.append(ICONST_1);
                  filterTemp.setEnd(il.append(new ALOAD(filterTemp.getIndex())));
                  il.append(methodGen.loadCurrentNode());
                  il.append(classGen.loadTranslet());
                  il.append(new INVOKESPECIAL(initCNLI));
  	    }
  	}
      }
  }
  