walkerfactory.java

java1.6众多例子参考

        if(isProx)
          return true;
        break;
      default:
        return true; // be conservative...
    }
    return false;
  }
    
  /**
   * Tell if the predicates need to have proximity knowledge.
   */
  public static boolean mightBeProximate(Compiler compiler, int opPos, int stepType)
          throws javax.xml.transform.TransformerException
  {

    boolean mightBeProximate = false;
    int argLen;

    switch (stepType)
    {
    case OpCodes.OP_VARIABLE :
    case OpCodes.OP_EXTFUNCTION :
    case OpCodes.OP_FUNCTION :
    case OpCodes.OP_GROUP :
      argLen = compiler.getArgLength(opPos);
      break;
    default :
      argLen = compiler.getArgLengthOfStep(opPos);
    }

    int predPos = compiler.getFirstPredicateOpPos(opPos);
    int count = 0;

    while (OpCodes.OP_PREDICATE == compiler.getOp(predPos))
    {
      count++;
      
      int innerExprOpPos = predPos+2;
      int predOp = compiler.getOp(innerExprOpPos);

      switch(predOp)
      {
        case OpCodes.OP_VARIABLE:
        	return true; // Would need more smarts to tell if this could be a number or not!
        case OpCodes.OP_LOCATIONPATH:
          // OK.
          break;
        case OpCodes.OP_NUMBER:
        case OpCodes.OP_NUMBERLIT:
          return true; // that's all she wrote!
        case OpCodes.OP_FUNCTION:
          boolean isProx 
            = functionProximateOrContainsProximate(compiler, innerExprOpPos);
          if(isProx)
            return true;
          break;
        case OpCodes.OP_GT:
        case OpCodes.OP_GTE:
        case OpCodes.OP_LT:
        case OpCodes.OP_LTE:
        case OpCodes.OP_EQUALS:
          int leftPos = compiler.getFirstChildPos(innerExprOpPos);
          int rightPos = compiler.getNextOpPos(leftPos);
          isProx = isProximateInnerExpr(compiler, leftPos);
          if(isProx)
            return true;
          isProx = isProximateInnerExpr(compiler, rightPos);
          if(isProx)
            return true;
          break;
        default:
          return true; // be conservative...
      }

      predPos = compiler.getNextOpPos(predPos);
    }

    return mightBeProximate;
  }
  
  /**
   * Special purpose function to see if we can optimize the pattern for 
   * a DescendantIterator.
   *
   * @param compiler non-null reference to compiler object that has processed
   *                 the XPath operations into an opcode map.
   * @param stepOpCodePos The opcode position for the step.
   * @param stepIndex The top-level step index withing the iterator.
   *
   * @return 32 bits as an integer that give information about the location
   * path as a whole.
   *
   * @throws javax.xml.transform.TransformerException
   */
  private static boolean isOptimizableForDescendantIterator(
          Compiler compiler, int stepOpCodePos, int stepIndex)
            throws javax.xml.transform.TransformerException
  {

    int stepType;
    int stepCount = 0;
    boolean foundDorDS = false;
    boolean foundSelf = false;
    boolean foundDS = false;
    
    int nodeTestType = OpCodes.NODETYPE_NODE;
    
    while (OpCodes.ENDOP != (stepType = compiler.getOp(stepOpCodePos)))
    {
      // The DescendantIterator can only do one node test.  If there's more 
      // than one, use another iterator.
      if(nodeTestType != OpCodes.NODETYPE_NODE && nodeTestType != OpCodes.NODETYPE_ROOT)
        return false;
        
      stepCount++;
      if(stepCount > 3)
        return false;
        
      boolean mightBeProximate = mightBeProximate(compiler, stepOpCodePos, stepType);
      if(mightBeProximate)
        return false;

      switch (stepType)
      {
      case OpCodes.FROM_FOLLOWING :
      case OpCodes.FROM_FOLLOWING_SIBLINGS :
      case OpCodes.FROM_PRECEDING :
      case OpCodes.FROM_PRECEDING_SIBLINGS :
      case OpCodes.FROM_PARENT :
      case OpCodes.OP_VARIABLE :
      case OpCodes.OP_EXTFUNCTION :
      case OpCodes.OP_FUNCTION :
      case OpCodes.OP_GROUP :
      case OpCodes.FROM_NAMESPACE :
      case OpCodes.FROM_ANCESTORS :
      case OpCodes.FROM_ANCESTORS_OR_SELF :
      case OpCodes.FROM_ATTRIBUTES :
      case OpCodes.MATCH_ATTRIBUTE :
      case OpCodes.MATCH_ANY_ANCESTOR :
      case OpCodes.MATCH_IMMEDIATE_ANCESTOR :
        return false;
      case OpCodes.FROM_ROOT :
        if(1 != stepCount)
          return false;
        break;
      case OpCodes.FROM_CHILDREN :
        if(!foundDS && !(foundDorDS && foundSelf))
          return false;
        break;
      case OpCodes.FROM_DESCENDANTS_OR_SELF :
        foundDS = true;
      case OpCodes.FROM_DESCENDANTS :
        if(3 == stepCount)
          return false;
        foundDorDS = true;
        break;
      case OpCodes.FROM_SELF :
        if(1 != stepCount)
          return false;
        foundSelf = true;
        break;
      default :
        throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NULL_ERROR_HANDLER, new Object[]{Integer.toString(stepType)})); //"Programmer's assertion: unknown opcode: "
                                  // + stepType);
      }
      
      nodeTestType = compiler.getStepTestType(stepOpCodePos);

      int nextStepOpCodePos = compiler.getNextStepPos(stepOpCodePos);

      if (nextStepOpCodePos < 0)
        break;
        
      if(OpCodes.ENDOP != compiler.getOp(nextStepOpCodePos))
      {
        if(compiler.countPredicates(stepOpCodePos) > 0)
        {
          return false;
        }
      }
      
      stepOpCodePos = nextStepOpCodePos;
    }

    return true;
  }

  /**
   * Analyze the location path and return 32 bits that give information about
   * the location path as a whole.  See the BIT_XXX constants for meaning about
   * each of the bits.
   *
   * @param compiler non-null reference to compiler object that has processed
   *                 the XPath operations into an opcode map.
   * @param stepOpCodePos The opcode position for the step.
   * @param stepIndex The top-level step index withing the iterator.
   *
   * @return 32 bits as an integer that give information about the location
   * path as a whole.
   *
   * @throws javax.xml.transform.TransformerException
   */
  private static int analyze(
          Compiler compiler, int stepOpCodePos, int stepIndex)
            throws javax.xml.transform.TransformerException
  {

    int stepType;
    int stepCount = 0;
    int analysisResult = 0x00000000;  // 32 bits of analysis

    while (OpCodes.ENDOP != (stepType = compiler.getOp(stepOpCodePos)))
    {
      stepCount++;

      // String namespace = compiler.getStepNS(stepOpCodePos);
      // boolean isNSWild = (null != namespace) 
      //                   ? namespace.equals(NodeTest.WILD) : false;
      // String localname = compiler.getStepLocalName(stepOpCodePos);
      // boolean isWild = (null != localname) ? localname.equals(NodeTest.WILD) : false;
      boolean predAnalysis = analyzePredicate(compiler, stepOpCodePos,
                                              stepType);

      if (predAnalysis)
        analysisResult |= BIT_PREDICATE;

      switch (stepType)
      {
      case OpCodes.OP_VARIABLE :
      case OpCodes.OP_EXTFUNCTION :
      case OpCodes.OP_FUNCTION :
      case OpCodes.OP_GROUP :
        analysisResult |= BIT_FILTER;
        break;
      case OpCodes.FROM_ROOT :
        analysisResult |= BIT_ROOT;
        break;
      case OpCodes.FROM_ANCESTORS :
        analysisResult |= BIT_ANCESTOR;
        break;
      case OpCodes.FROM_ANCESTORS_OR_SELF :
        analysisResult |= BIT_ANCESTOR_OR_SELF;
        break;
      case OpCodes.FROM_ATTRIBUTES :
        analysisResult |= BIT_ATTRIBUTE;
        break;
      case OpCodes.FROM_NAMESPACE :
        analysisResult |= BIT_NAMESPACE;
        break;
      case OpCodes.FROM_CHILDREN :
        analysisResult |= BIT_CHILD;
        break;
      case OpCodes.FROM_DESCENDANTS :
        analysisResult |= BIT_DESCENDANT;
        break;
      case OpCodes.FROM_DESCENDANTS_OR_SELF :

        // Use a special bit to to make sure we get the right analysis of "//foo".
        if (2 == stepCount && BIT_ROOT == analysisResult)
        {
          analysisResult |= BIT_ANY_DESCENDANT_FROM_ROOT;
        }

        analysisResult |= BIT_DESCENDANT_OR_SELF;
        break;
      case OpCodes.FROM_FOLLOWING :
        analysisResult |= BIT_FOLLOWING;
        break;
      case OpCodes.FROM_FOLLOWING_SIBLINGS :
        analysisResult |= BIT_FOLLOWING_SIBLING;
        break;
      case OpCodes.FROM_PRECEDING :
        analysisResult |= BIT_PRECEDING;
        break;
      case OpCodes.FROM_PRECEDING_SIBLINGS :
        analysisResult |= BIT_PRECEDING_SIBLING;
        break;
      case OpCodes.FROM_PARENT :
        analysisResult |= BIT_PARENT;
        break;
      case OpCodes.FROM_SELF :
        analysisResult |= BIT_SELF;
        break;
      case OpCodes.MATCH_ATTRIBUTE :
        analysisResult |= (BIT_MATCH_PATTERN | BIT_ATTRIBUTE);
        break;
      case OpCodes.MATCH_ANY_ANCESTOR :
        analysisResult |= (BIT_MATCH_PATTERN | BIT_ANCESTOR);
        break;
      case OpCodes.MATCH_IMMEDIATE_ANCESTOR :
        analysisResult |= (BIT_MATCH_PATTERN | BIT_PARENT);
        break;
      default :
        throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NULL_ERROR_HANDLER, new Object[]{Integer.toString(stepType)})); //"Programmer's assertion: unknown opcode: "
                                   //+ stepType);
      }

      if (OpCodes.NODETYPE_NODE == compiler.getOp(stepOpCodePos + 3))  // child::node()
      {
        analysisResult |= BIT_NODETEST_ANY;
      }

      stepOpCodePos = compiler.getNextStepPos(stepOpCodePos);

      if (stepOpCodePos < 0)
        break;
    }

    analysisResult |= (stepCount & BITS_COUNT);

    return analysisResult;
  }
  
  /**
   * Tell if the given axis goes downword.  Bogus name, if you can think of 
   * a better one, please do tell.  This really has to do with inverting 
   * attribute axis.
   * @param axis One of Axis.XXX.
   * @return true if the axis is not a child axis and does not go up from 
   * the axis root.
   */
  public static boolean isDownwardAxisOfMany(int axis)
  {
    return ((Axis.DESCENDANTORSELF == axis) ||
          (Axis.DESCENDANT == axis) 
          || (Axis.FOLLOWING == axis) 
//          || (Axis.FOLLOWINGSIBLING == axis) 
          || (Axis.PRECEDING == axis) 
//          || (Axis.PRECEDINGSIBLING == axis)
          );
  }

  /**
   * Read a <a href="http://www.w3.org/TR/xpath#location-paths">LocationPath</a>
   * as a generalized match pattern.  What this means is that the LocationPath
   * is read backwards, as a test on a given node, to see if it matches the
   * criteria of the selection, and ends up at the context node.  Essentially,
   * this is a backwards query from a given node, to find the context node.
   * <p>So, the selection "foo/daz[2]" is, in non-abreviated expanded syntax,
   * "self::node()/following-sibling::foo/child::daz[position()=2]".
   * Taking this as a match pattern for a probable node, it works out to
   * "self::daz/parent::foo[child::daz[position()=2 and isPrevStepNode()]
   * precedingSibling::node()[isContextNodeOfLocationPath()]", adding magic
   * isPrevStepNode and isContextNodeOfLocationPath operations.  Predicates in
   * the location path have to be executed by the following step,
   * because they have to know the context of their execution.
   *
   * @param mpi The MatchPatternIterator to which the steps will be attached.
   * @param compiler The compiler that holds the syntax tree/op map to
   * construct from.
   * @param stepOpCodePos The current op code position within the opmap.
   * @param stepIndex The top-level step index withing the iterator.
   *
   * @return A StepPattern object, which may contain relative StepPatterns.
   *
   * @throws javax.xml.transform.TransformerException
   */
  static StepPattern loadSteps(
          MatchPatternIterator mpi, Compiler compiler, int stepOpCodePos, 
                                                       int stepIndex)
            throws javax.xml.transform.TransformerException
  {
    if (DEBUG_PATTERN_CREATION)
    {
      System.out.println("================");
      System.out.println("loadSteps for: "+compiler.getPatternString());
    }
    int stepType;
    StepPattern step = null;
    StepPattern firstStep = null, prevStep = null;
    int analysis = analyze(compiler, stepOpCodePos, stepIndex);

    while (OpCodes.ENDOP != (stepType = compiler.getOp(stepOpCodePos)))
    {
      step = createDefaultStepPattern(compiler, stepOpCodePos, mpi, analysis,
                                      firstStep, prevStep);

      if (null == firstStep)
      {
        firstStep = step;
      }
      else
      {

        //prevStep.setNextWalker(step);
        step.setRelativePathPattern(prevStep);
      }

      prevStep = step;
      stepOpCodePos = compiler.getNextStepPos(stepOpCodePos);

      if (stepOpCodePos < 0)
        break;
    }
    
    int axis = Axis.SELF;
    int paxis = Axis.SELF;
    StepPattern tail = step;
    for (StepPattern pat = step; null != pat; 
         pat = pat.getRelativePathPattern()) 
    {
      int nextAxis = pat.getAxis();
      //int nextPaxis = pat.getPredicateAxis();
      pat.setAxis(axis);
      
      // The predicate axis can't be moved!!!  Test Axes103
      // pat.setPredicateAxis(paxis);
      
      // If we have an attribute or namespace axis that went up, then 
      // it won't find the attribute in the inverse, since the select-to-match
      // axes are not invertable (an element is a parent of an attribute, but 
      // and attribute is not a child of an element).
      // If we don't do the magic below, then "@*/ancestor-or-self::*" gets
      // inverted for match to "self::*/descendant-or-self::@*/parent::node()",
      // which obviously won't work.
      // So we will rewrite this as:
      // "self::*/descendant-or-self::*/attribute::*/parent::node()"
      // Child has to be rewritten a little differently:
      // select: "@*/parent::*"
      // inverted match: "self::*/child::@*/parent::node()"
      // rewrite: "self::*/attribute::*/parent::node()"
      // Axes that go down in the select, do not have to have special treatment 
      // in the rewrite. The following inverted match will still not select 
      // anything.
      // select: "@*/child::*"
      // inverted match: "self::*/parent::@*/parent::node()"
      // Lovely business, this.
      // -sb
      int whatToShow = pat.getWhatToShow();
      if(whatToShow == DTMFilter.SHOW_ATTRIBUTE || 
         whatToShow == DTMFilter.SHOW_NAMESPACE)
      {
        int newAxis = (whatToShow == DTMFilter.SHOW_ATTRIBUTE) ? 
                       Axis.ATTRIBUTE : Axis.NAMESPACE;
        if(isDownwardAxisOfMany(axis))
        {
          StepPattern attrPat = new StepPattern(whatToShow, 
                                    pat.getNamespace(),
                                    pat.getLocalName(),
                                //newAxis, pat.getPredicateAxis);
                                                newAxis, 0); // don't care about the predicate axis
          XNumber score = pat.getStaticScore();
          pat.setNamespace(null);
          pat.setLocalName(NodeTest.WILD);
          attrPat.setPredicates(pat.getPredicates());
          pat.setPredicates(null);
          pat.setWhatToShow(DTMFilter.SHOW_ELEMENT);
          StepPattern rel = pat.getRelativePathPattern();
          pat.setRelativePathPattern(attrPat);
          attrPat.setRelativePathPattern(rel);
          attrPat.setStaticScore(score);
          
          // This is needed to inverse a following pattern, because of the 
          // wacky Xalan rules for following from an attribute.  See axes108.
          // By these rules, following from an attribute is not strictly 
          // inverseable.