public static DTMIterator newDTMIterator()

in src/org/apache/xpath/axes/WalkerFactory.java [158:285]
81 lines of code
31 McCabe index (conditional complexity)

  public static DTMIterator newDTMIterator(
          Compiler compiler, int opPos,
          boolean isTopLevel)
            throws javax.xml.transform.TransformerException
  {

    int firstStepPos = OpMap.getFirstChildPos(opPos);
    int analysis = analyze(compiler, firstStepPos, 0);
    boolean isOneStep = isOneStep(analysis);
    DTMIterator iter;

    // Is the iteration a one-step attribute pattern (i.e. select="@foo")?
    if (isOneStep && walksSelfOnly(analysis) && 
        isWild(analysis) && !hasPredicate(analysis))
    {
      if (DEBUG_ITERATOR_CREATION)
        diagnoseIterator("SelfIteratorNoPredicate", analysis, compiler);

      // Then use a simple iteration of the attributes, with node test 
      // and predicate testing.
      iter = new SelfIteratorNoPredicate(compiler, opPos, analysis);
    }
    // Is the iteration exactly one child step?
    else if (walksChildrenOnly(analysis) && isOneStep)
    {

      // Does the pattern specify *any* child with no predicate? (i.e. select="child::node()".
      if (isWild(analysis) && !hasPredicate(analysis))
      {
        if (DEBUG_ITERATOR_CREATION)
          diagnoseIterator("ChildIterator", analysis, compiler);

        // Use simple child iteration without any test.
        iter = new ChildIterator(compiler, opPos, analysis);
      }
      else
      {
        if (DEBUG_ITERATOR_CREATION)
          diagnoseIterator("ChildTestIterator", analysis, compiler);

        // Else use simple node test iteration with predicate test.
        iter = new ChildTestIterator(compiler, opPos, analysis);
      }
    }
    // Is the iteration a one-step attribute pattern (i.e. select="@foo")?
    else if (isOneStep && walksAttributes(analysis))
    {
      if (DEBUG_ITERATOR_CREATION)
        diagnoseIterator("AttributeIterator", analysis, compiler);

      // Then use a simple iteration of the attributes, with node test 
      // and predicate testing.
      iter = new AttributeIterator(compiler, opPos, analysis);
    }
    else if(isOneStep && !walksFilteredList(analysis))
    {
      if( !walksNamespaces(analysis) 
      && (walksInDocOrder(analysis) || isSet(analysis, BIT_PARENT)))
      {
        if (false || DEBUG_ITERATOR_CREATION)
          diagnoseIterator("OneStepIteratorForward", analysis, compiler);
  
        // Then use a simple iteration of the attributes, with node test 
        // and predicate testing.
        iter = new OneStepIteratorForward(compiler, opPos, analysis);
      }
      else
      {
        if (false || DEBUG_ITERATOR_CREATION)
          diagnoseIterator("OneStepIterator", analysis, compiler);
  
        // Then use a simple iteration of the attributes, with node test 
        // and predicate testing.
        iter = new OneStepIterator(compiler, opPos, analysis);
      }
    }

    // Analysis of "//center":
    // bits: 1001000000001010000000000000011
    // count: 3
    // root
    // child:node()
    // BIT_DESCENDANT_OR_SELF
    // It's highly possible that we should have a seperate bit set for 
    // "//foo" patterns.
    // For at least the time being, we can't optimize patterns like 
    // "//table[3]", because this has to be analyzed as 
    // "/descendant-or-self::node()/table[3]" in order for the indexes 
    // to work right.
    else if (isOptimizableForDescendantIterator(compiler, firstStepPos, 0)
              // && getStepCount(analysis) <= 3 
              // && walksDescendants(analysis) 
              // && walksSubtreeOnlyFromRootOrContext(analysis)
             )
    {
      if (DEBUG_ITERATOR_CREATION)
        diagnoseIterator("DescendantIterator", analysis, compiler);

      iter = new DescendantIterator(compiler, opPos, analysis);
    }
    else
    { 
      if(isNaturalDocOrder(compiler, firstStepPos, 0, analysis))
      {
        if (false || DEBUG_ITERATOR_CREATION)
        {
          diagnoseIterator("WalkingIterator", analysis, compiler);
        }
  
        iter = new WalkingIterator(compiler, opPos, analysis, true);
      }
      else
      {
//        if (DEBUG_ITERATOR_CREATION)
//          diagnoseIterator("MatchPatternIterator", analysis, compiler);
//
//        return new MatchPatternIterator(compiler, opPos, analysis);
        if (DEBUG_ITERATOR_CREATION)
          diagnoseIterator("WalkingIteratorSorted", analysis, compiler);

        iter = new WalkingIteratorSorted(compiler, opPos, analysis, true);
      }
    }
    if(iter instanceof LocPathIterator)
      ((LocPathIterator)iter).setIsTopLevel(isTopLevel);
      
    return iter;
  }