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.classfile.Field;
  import org.apache.bcel.generic.ALOAD;
  import org.apache.bcel.generic.ASTORE;
  import org.apache.bcel.generic.BranchHandle;
  import org.apache.bcel.generic.ConstantPoolGen;
  import org.apache.bcel.generic.GETFIELD;
  import org.apache.bcel.generic.GOTO;
  import org.apache.bcel.generic.GOTO_W;
  import org.apache.bcel.generic.IFLT;
  import org.apache.bcel.generic.IFNE;
  import org.apache.bcel.generic.IFNONNULL;
  import org.apache.bcel.generic.IF_ICMPEQ;
  import org.apache.bcel.generic.IF_ICMPLT;
  import org.apache.bcel.generic.IF_ICMPNE;
  import org.apache.bcel.generic.ILOAD;
  import org.apache.bcel.generic.INVOKEINTERFACE;
  import org.apache.bcel.generic.INVOKESPECIAL;
  import org.apache.bcel.generic.ISTORE;
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.bcel.generic.LocalVariableGen;
  import org.apache.bcel.generic.NEW;
  import org.apache.bcel.generic.PUSH;
  import org.apache.bcel.generic.PUTFIELD;
  import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
  import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
  import org.apache.xalan.xsltc.compiler.util.Type;
  import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
  import org.apache.xalan.xsltc.compiler.util.Util;
  import org.apache.xml.dtm.Axis;
  import org.apache.xml.dtm.DTM;
  
  /**
   * @author Jacek Ambroziak
   * @author Santiago Pericas-Geertsen
   * @author Erwin Bolwidt <ejb@klomp.org>
   */
  class StepPattern extends RelativePathPattern {
  
      private static final int NO_CONTEXT = 0;
      private static final int SIMPLE_CONTEXT = 1;
      private static final int GENERAL_CONTEXT = 2;
  
      protected final int _axis;
      protected final int _nodeType;
      protected Vector _predicates;
  
      private Step    _step = null;
      private boolean _isEpsilon = false;
      private int     _contextCase;
  
      private double  _priority = Double.MAX_VALUE;
  
      public StepPattern(int axis, int nodeType, Vector predicates) {
  	_axis = axis;
  	_nodeType = nodeType;
  	_predicates = predicates;
      }
  
      public void setParser(Parser parser) {
  	super.setParser(parser);
  	if (_predicates != null) {
  	    final int n = _predicates.size();
  	    for (int i = 0; i < n; i++) {
  		final Predicate exp = (Predicate)_predicates.elementAt(i);
  		exp.setParser(parser);
  		exp.setParent(this);
  	    }
  	}
      }
  
      public int getNodeType() {
  	return _nodeType;
      }
  
      public void setPriority(double priority) {
  	_priority = priority;
      }
      
      public StepPattern getKernelPattern() {
  	return this;
      }
  	
      public boolean isWildcard() {
  	return _isEpsilon && hasPredicates() == false;
      }
  
      public StepPattern setPredicates(Vector predicates) {
  	_predicates = predicates;
  	return(this);
      }
      
      protected boolean hasPredicates() {
  	return _predicates != null && _predicates.size() > 0;
      }
  
      public double getDefaultPriority() {
  	if (_priority != Double.MAX_VALUE) {
  	    return _priority;
  	}
  
  	if (hasPredicates()) {
  	    return 0.5;
  	}
  	else {
  	    switch(_nodeType) {
  	    case -1:
  		return -0.5;	// node()
  	    case 0:
  		return 0.0;
  	    default:
  		return (_nodeType >= NodeTest.GTYPE) ? 0.0 : -0.5;
  	    }
  	}
      }
      
      public int getAxis() {
  	return _axis;
      }
  
      public void reduceKernelPattern() {
  	_isEpsilon = true;
      }
  	
      public String toString() {
  	final StringBuffer buffer = new StringBuffer("stepPattern(\"");
      buffer.append(Axis.getNames(_axis))
  	    .append("\", ")
  	    .append(_isEpsilon ? 
  			("epsilon{" + Integer.toString(_nodeType) + "}") :
  			 Integer.toString(_nodeType));
  	if (_predicates != null)
  	    buffer.append(", ").append(_predicates.toString());
  	return buffer.append(')').toString();
      }
      
      private int analyzeCases() {
  	boolean noContext = true;
  	final int n = _predicates.size();
  
  	for (int i = 0; i < n && noContext; i++) {
  	    Predicate pred = (Predicate) _predicates.elementAt(i);
              if (pred.isNthPositionFilter() || 
                  pred.hasPositionCall() || 
                  pred.hasLastCall()) 
              {
  		noContext = false;
  	    }
  	}
  
  	if (noContext) {
  	    return NO_CONTEXT;
  	}
  	else if (n == 1) {
  	    return SIMPLE_CONTEXT;
  	}
  	return GENERAL_CONTEXT;
      }
  
      private String getNextFieldName() {
  	return  "__step_pattern_iter_" + getXSLTC().nextStepPatternSerial();
      }
  
      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);
              }
  
              // Analyze context cases
              _contextCase = analyzeCases();
  
              Step step = null;
  
              // Create an instance of Step to do the translation
              if (_contextCase == SIMPLE_CONTEXT) {
                  Predicate pred = (Predicate)_predicates.elementAt(0);
                  if (pred.isNthPositionFilter()) {
                      _contextCase = GENERAL_CONTEXT;
                      step = new Step(_axis, _nodeType, _predicates);
                  } else {
                      step = new Step(_axis, _nodeType, null);
                  }
              } else if (_contextCase == GENERAL_CONTEXT) {
                  final int len = _predicates.size();
                  for (int i = 0; i < len; i++) {
                      ((Predicate)_predicates.elementAt(i)).dontOptimize();
                  }
  
                  step = new Step(_axis, _nodeType, _predicates);
              }
              
              if (step != null) {
                  step.setParser(getParser());
                  step.typeCheck(stable);
                  _step = step;
              }
          }
          return _axis == Axis.CHILD ? Type.Element : Type.Attribute;
      }
  
      private void translateKernel(ClassGenerator classGen, 
  				 MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  	
  	if (_nodeType == DTM.ELEMENT_NODE) {
  	    final int check = cpg.addInterfaceMethodref(DOM_INTF,
  							"isElement", "(I)Z");
  	    il.append(methodGen.loadDOM());
  	    il.append(SWAP);
  	    il.append(new INVOKEINTERFACE(check, 2));
  	
  	    // Need to allow for long jumps here
  	    final BranchHandle icmp = il.append(new IFNE(null));
  	    _falseList.add(il.append(new GOTO_W(null)));
  	    icmp.setTarget(il.append(NOP));
  	}
  	else if (_nodeType == DTM.ATTRIBUTE_NODE) {
  	    final int check = cpg.addInterfaceMethodref(DOM_INTF,
  							"isAttribute", "(I)Z");
  	    il.append(methodGen.loadDOM());
  	    il.append(SWAP);
  	    il.append(new INVOKEINTERFACE(check, 2));
  	
  	    // Need to allow for long jumps here
  	    final BranchHandle icmp = il.append(new IFNE(null));
  	    _falseList.add(il.append(new GOTO_W(null)));
  	    icmp.setTarget(il.append(NOP));
  	}
  	else {
  	    // context node is on the stack
  	    final int getEType = cpg.addInterfaceMethodref(DOM_INTF,
  							  "getExpandedTypeID",
                                                            "(I)I");
  	    il.append(methodGen.loadDOM());
  	    il.append(SWAP);
  	    il.append(new INVOKEINTERFACE(getEType, 2));
  	    il.append(new PUSH(cpg, _nodeType));
  	
  	    // Need to allow for long jumps here
  	    final BranchHandle icmp = il.append(new IF_ICMPEQ(null));
  	    _falseList.add(il.append(new GOTO_W(null)));
  	    icmp.setTarget(il.append(NOP));
  	}
      }
  
      private void translateNoContext(ClassGenerator classGen, 
  				    MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  
  	// 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 (!_isEpsilon) {
  	    il.append(methodGen.loadCurrentNode());
  	    translateKernel(classGen, methodGen);
  	}
  
  	// Compile the expressions within the predicates
  	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));
      }
  
      private void translateSimpleContext(ClassGenerator classGen, 
  					MethodGenerator methodGen) {
  	int index;
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  
  	// Store matching node into a local variable
  	LocalVariableGen match;
  	match = methodGen.addLocalVariable("step_pattern_tmp1", 
  					   Util.getJCRefType(NODE_SIG),
  					   null, null);
  	match.setStart(il.append(new ISTORE(match.getIndex())));
  
  	// If pattern not reduced then check kernel
  	if (!_isEpsilon) {
  	    il.append(new ILOAD(match.getIndex()));
   	    translateKernel(classGen, methodGen);
  	}
  
  	// Push current iterator and current node on the stack
  	il.append(methodGen.loadCurrentNode());
  	il.append(methodGen.loadIterator());
  
  	// Create a new matching iterator using the matching node
  	index = cpg.addMethodref(MATCHING_ITERATOR, "<init>", 
  				 "(I" + NODE_ITERATOR_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.
  
  	_step.translate(classGen, methodGen);
          LocalVariableGen stepIteratorTemp =
                  methodGen.addLocalVariable("step_pattern_tmp2",
                                             Util.getJCRefType(NODE_ITERATOR_SIG),
                                             null, null);
          stepIteratorTemp.setStart(
                  il.append(new ASTORE(stepIteratorTemp.getIndex())));
  
  	il.append(new NEW(cpg.addClass(MATCHING_ITERATOR)));
  	il.append(DUP);
  	il.append(new ILOAD(match.getIndex()));
          stepIteratorTemp.setEnd(
                  il.append(new ALOAD(stepIteratorTemp.getIndex())));
  	il.append(new INVOKESPECIAL(index));
  
  	// Get the parent of the matching node
  	il.append(methodGen.loadDOM());
  	il.append(new ILOAD(match.getIndex()));
  	index = cpg.addInterfaceMethodref(DOM_INTF, GET_PARENT, GET_PARENT_SIG);
  	il.append(new INVOKEINTERFACE(index, 2));
  
  	// Start the iterator with the parent 
  	il.append(methodGen.setStartNode());
  
  	// Overwrite current iterator and current node
  	il.append(methodGen.storeIterator());
  	match.setEnd(il.append(new ILOAD(match.getIndex())));
  	il.append(methodGen.storeCurrentNode());
  
  	// Translate the expression of the predicate 
  	Predicate pred = (Predicate) _predicates.elementAt(0);
  	Expression exp = pred.getExpr();
  	exp.translateDesynthesized(classGen, methodGen);
  
  	// Backpatch true list and restore current iterator/node
  	InstructionHandle restore = il.append(methodGen.storeIterator());
  	il.append(methodGen.storeCurrentNode());
  	exp.backPatchTrueList(restore);
  	BranchHandle skipFalse = il.append(new GOTO(null));
  
  	// Backpatch false list and restore current iterator/node
  	restore = il.append(methodGen.storeIterator());
  	il.append(methodGen.storeCurrentNode());
  	exp.backPatchFalseList(restore);
  	_falseList.add(il.append(new GOTO(null)));
  
  	// True list falls through
  	skipFalse.setTarget(il.append(NOP));
      }
  
      private void translateGeneralContext(ClassGenerator classGen, 
  					 MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  
  	int iteratorIndex = 0;
  	BranchHandle ifBlock = null;
  	LocalVariableGen iter, node, node2;
  	final String iteratorName = getNextFieldName();
  
  	// Store node on the stack into a local variable
  	node = methodGen.addLocalVariable("step_pattern_tmp1", 
  					  Util.getJCRefType(NODE_SIG),
  					  null, null);
  	node.setStart(il.append(new ISTORE(node.getIndex())));
  
  	// Create a new local to store the iterator
  	iter = methodGen.addLocalVariable("step_pattern_tmp2", 
  					  Util.getJCRefType(NODE_ITERATOR_SIG),
  					  null, null);
  
  	// Add a new private field if this is the main class
  	if (!classGen.isExternal()) {
  	    final Field iterator =
  		new Field(ACC_PRIVATE, 
  			  cpg.addUtf8(iteratorName),
  			  cpg.addUtf8(NODE_ITERATOR_SIG),
  			  null, cpg.getConstantPool());
  	    classGen.addField(iterator);
  	    iteratorIndex = cpg.addFieldref(classGen.getClassName(), 
  					    iteratorName,
  					    NODE_ITERATOR_SIG);
  
  	    il.append(classGen.loadTranslet());
  	    il.append(new GETFIELD(iteratorIndex));
  	    il.append(DUP);
  	    iter.setStart(il.append(new ASTORE(iter.getIndex())));
  	    ifBlock = il.append(new IFNONNULL(null));
  	    il.append(classGen.loadTranslet());
  	}	
  
  	// Compile the step created at type checking time
  	_step.translate(classGen, methodGen);
  	InstructionHandle iterStore = il.append(new ASTORE(iter.getIndex()));
  
  	// If in the main class update the field too
  	if (!classGen.isExternal()) {
  	    il.append(new ALOAD(iter.getIndex()));
  	    il.append(new PUTFIELD(iteratorIndex));
  	    ifBlock.setTarget(il.append(NOP));
  	} else {
              // If class is not external, start of range for iter variable was
              // set above
              iter.setStart(iterStore);       
          }
  
  	// Get the parent of the node on the stack
  	il.append(methodGen.loadDOM());
  	il.append(new ILOAD(node.getIndex()));
  	int index = cpg.addInterfaceMethodref(DOM_INTF,
  					      GET_PARENT, GET_PARENT_SIG);
  	il.append(new INVOKEINTERFACE(index, 2));
  
  	// Initialize the iterator with the parent
  	il.append(new ALOAD(iter.getIndex()));
  	il.append(SWAP);
  	il.append(methodGen.setStartNode());
  
  	/* 
  	 * Inline loop:
  	 *
  	 * int node2;
  	 * while ((node2 = iter.next()) != NodeIterator.END 
  	 *		  && node2 < node);
  	 * return node2 == node; 
  	 */
  	BranchHandle skipNext;
  	InstructionHandle begin, next;
  	node2 = methodGen.addLocalVariable("step_pattern_tmp3", 
  					   Util.getJCRefType(NODE_SIG),
  					   null, null);
  
  	skipNext = il.append(new GOTO(null));
  	next = il.append(new ALOAD(iter.getIndex()));
          node2.setStart(next);
  	begin = il.append(methodGen.nextNode());
  	il.append(DUP);
  	il.append(new ISTORE(node2.getIndex()));
  	_falseList.add(il.append(new IFLT(null)));	// NodeIterator.END
  
  	il.append(new ILOAD(node2.getIndex()));
  	il.append(new ILOAD(node.getIndex()));
  	iter.setEnd(il.append(new IF_ICMPLT(next)));
  
  	node2.setEnd(il.append(new ILOAD(node2.getIndex())));
  	node.setEnd(il.append(new ILOAD(node.getIndex())));
  	_falseList.add(il.append(new IF_ICMPNE(null)));
  
  	skipNext.setTarget(begin);
      }
  	
      public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  
  	if (hasPredicates()) {
  	    switch (_contextCase) {
  	    case NO_CONTEXT:
  		translateNoContext(classGen, methodGen);
  		break;
  		
  	    case SIMPLE_CONTEXT:
  		translateSimpleContext(classGen, methodGen);
  		break;
  		
  	    default:
  		translateGeneralContext(classGen, methodGen);
  		break;
  	    }
  	}
  	else if (isWildcard()) {
  	    il.append(POP); 	// true list falls through
  	}
  	else {
  	    translateKernel(classGen, methodGen);
  	}
      }
  }
  