walkerfactory.java

java1.6众多例子参考

/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed 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: WalkerFactory.java,v 1.2.4.1 2005/09/10 03:42:19 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xalan.internal.res.XSLMessages;
import com.sun.org.apache.xml.internal.dtm.Axis;
import com.sun.org.apache.xml.internal.dtm.DTMFilter;
import com.sun.org.apache.xml.internal.dtm.DTMIterator;
import com.sun.org.apache.xpath.internal.Expression;
import com.sun.org.apache.xpath.internal.compiler.Compiler;
import com.sun.org.apache.xpath.internal.compiler.FunctionTable;
import com.sun.org.apache.xpath.internal.compiler.OpCodes;
import com.sun.org.apache.xpath.internal.objects.XNumber;
import com.sun.org.apache.xpath.internal.patterns.ContextMatchStepPattern;
import com.sun.org.apache.xpath.internal.patterns.FunctionPattern;
import com.sun.org.apache.xpath.internal.patterns.NodeTest;
import com.sun.org.apache.xpath.internal.patterns.StepPattern;
import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;

/**
 * This class is both a factory for XPath location path expressions,
 * which are built from the opcode map output, and an analysis engine
 * for the location path expressions in order to provide optimization hints.
 */
public class WalkerFactory
{

  /**
   * This method is for building an array of possible levels
   * where the target element(s) could be found for a match.
   * @param lpi The owning location path iterator.
   * @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.
   *
   * @return non-null AxesWalker derivative.
   *
   * @throws javax.xml.transform.TransformerException
   * @xsl.usage advanced
   */
  static AxesWalker loadOneWalker(
          WalkingIterator lpi, Compiler compiler, int stepOpCodePos)
            throws javax.xml.transform.TransformerException
  {

    AxesWalker firstWalker = null;
    int stepType = compiler.getOp(stepOpCodePos);

    if (stepType != OpCodes.ENDOP)
    {

      // m_axesWalkers = new AxesWalker[1];
      // As we unwind from the recursion, create the iterators.
      firstWalker = createDefaultWalker(compiler, stepType, lpi, 0);

      firstWalker.init(compiler, stepOpCodePos, stepType);
    }

    return firstWalker;
  }

  /**
   * This method is for building an array of possible levels
   * where the target element(s) could be found for a match.
   * @param lpi The owning location path iterator object.
   * @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 non-null AxesWalker derivative.
   *
   * @throws javax.xml.transform.TransformerException
   * @xsl.usage advanced
   */
  static AxesWalker loadWalkers(
          WalkingIterator lpi, Compiler compiler, int stepOpCodePos, int stepIndex)
            throws javax.xml.transform.TransformerException
  {

    int stepType;
    AxesWalker firstWalker = null;
    AxesWalker walker, prevWalker = null;

    int analysis = analyze(compiler, stepOpCodePos, stepIndex);

    while (OpCodes.ENDOP != (stepType = compiler.getOp(stepOpCodePos)))
    {
      walker = createDefaultWalker(compiler, stepOpCodePos, lpi, analysis);

      walker.init(compiler, stepOpCodePos, stepType);
      walker.exprSetParent(lpi);

      // walker.setAnalysis(analysis);
      if (null == firstWalker)
      {
        firstWalker = walker;
      }
      else
      {
        prevWalker.setNextWalker(walker);
        walker.setPrevWalker(prevWalker);
      }

      prevWalker = walker;
      stepOpCodePos = compiler.getNextStepPos(stepOpCodePos);

      if (stepOpCodePos < 0)
        break;
    }

    return firstWalker;
  }
  
  public static boolean isSet(int analysis, int bits)
  {
    return (0 != (analysis & bits));
  }
  
  public static void diagnoseIterator(String name, int analysis, Compiler compiler)
  {
    System.out.println(compiler.toString()+", "+name+", "
                             + Integer.toBinaryString(analysis) + ", "
                             + getAnalysisString(analysis));
  }

  /**
   * Create a new LocPathIterator iterator.  The exact type of iterator
   * returned is based on an analysis of the XPath operations.
   *
   * @param compiler non-null reference to compiler object that has processed
   *                 the XPath operations into an opcode map.
   * @param opPos The position of the operation code for this itterator.
   *
   * @return non-null reference to a LocPathIterator or derivative.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public static DTMIterator newDTMIterator(
          Compiler compiler, int opPos,
          boolean isTopLevel)
            throws javax.xml.transform.TransformerException
  {

    int firstStepPos = compiler.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;
  }
  
  /**
   * 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.
   *
   * @return 32 bits as an integer that give information about the location
   * path as a whole.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public static int getAxisFromStep(
          Compiler compiler, int stepOpCodePos)
            throws javax.xml.transform.TransformerException
  {

    int stepType = compiler.getOp(stepOpCodePos);

    switch (stepType)
    {
    case OpCodes.FROM_FOLLOWING :
      return Axis.FOLLOWING;
    case OpCodes.FROM_FOLLOWING_SIBLINGS :
      return Axis.FOLLOWINGSIBLING;
    case OpCodes.FROM_PRECEDING :
      return Axis.PRECEDING;
    case OpCodes.FROM_PRECEDING_SIBLINGS :
      return Axis.PRECEDINGSIBLING;
    case OpCodes.FROM_PARENT :
      return Axis.PARENT;
    case OpCodes.FROM_NAMESPACE :
      return Axis.NAMESPACE;
    case OpCodes.FROM_ANCESTORS :
      return Axis.ANCESTOR;
    case OpCodes.FROM_ANCESTORS_OR_SELF :
      return Axis.ANCESTORORSELF;
    case OpCodes.FROM_ATTRIBUTES :
      return Axis.ATTRIBUTE;
    case OpCodes.FROM_ROOT :
      return Axis.ROOT;
    case OpCodes.FROM_CHILDREN :
      return Axis.CHILD;
    case OpCodes.FROM_DESCENDANTS_OR_SELF :
      return Axis.DESCENDANTORSELF;
    case OpCodes.FROM_DESCENDANTS :
      return Axis.DESCENDANT;
    case OpCodes.FROM_SELF :
      return Axis.SELF;
    case OpCodes.OP_EXTFUNCTION :
    case OpCodes.OP_FUNCTION :
    case OpCodes.OP_GROUP :
    case OpCodes.OP_VARIABLE :
      return Axis.FILTEREDLIST;
    }

    throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NULL_ERROR_HANDLER, new Object[]{Integer.toString(stepType)})); //"Programmer's assertion: unknown opcode: "
                               //+ stepType);
   }
    
    /**
     * Get a corresponding BIT_XXX from an axis.
     * @param axis One of Axis.ANCESTOR, etc.
     * @return One of BIT_ANCESTOR, etc.
     */
    static public int getAnalysisBitFromAxes(int axis)
    {
      switch (axis) // Generate new traverser
        {
        case Axis.ANCESTOR :
          return BIT_ANCESTOR;
        case Axis.ANCESTORORSELF :
          return BIT_ANCESTOR_OR_SELF;
        case Axis.ATTRIBUTE :
          return BIT_ATTRIBUTE;
        case Axis.CHILD :
          return BIT_CHILD;
        case Axis.DESCENDANT :
          return BIT_DESCENDANT;
        case Axis.DESCENDANTORSELF :
          return BIT_DESCENDANT_OR_SELF;
        case Axis.FOLLOWING :
          return BIT_FOLLOWING;
        case Axis.FOLLOWINGSIBLING :
          return BIT_FOLLOWING_SIBLING;
        case Axis.NAMESPACE :
        case Axis.NAMESPACEDECLS :
          return BIT_NAMESPACE;
        case Axis.PARENT :
          return BIT_PARENT;
        case Axis.PRECEDING :
          return BIT_PRECEDING;
        case Axis.PRECEDINGSIBLING :
          return BIT_PRECEDING_SIBLING;
        case Axis.SELF :
          return BIT_SELF;
        case Axis.ALLFROMNODE :
          return BIT_DESCENDANT_OR_SELF;
          // case Axis.PRECEDINGANDANCESTOR :
        case Axis.DESCENDANTSFROMROOT :
        case Axis.ALL :
        case Axis.DESCENDANTSORSELFFROMROOT :
          return BIT_ANY_DESCENDANT_FROM_ROOT;
        case Axis.ROOT :
          return BIT_ROOT;
        case Axis.FILTEREDLIST :
          return BIT_FILTER;
        default :
          return BIT_FILTER;
      }
    }
  
  static boolean functionProximateOrContainsProximate(Compiler compiler, 
                                                      int opPos)
  {
    int endFunc = opPos + compiler.getOp(opPos + 1) - 1;
    opPos = compiler.getFirstChildPos(opPos);
    int funcID = compiler.getOp(opPos);
    //  System.out.println("funcID: "+funcID);
    //  System.out.println("opPos: "+opPos);
    //  System.out.println("endFunc: "+endFunc);
    switch(funcID)
    {
      case FunctionTable.FUNC_LAST:
      case FunctionTable.FUNC_POSITION:
        return true;
      default:
        opPos++;
        int i = 0;
        for (int p = opPos; p < endFunc; p = compiler.getNextOpPos(p), i++)
        {
          int innerExprOpPos = p+2;
          int argOp = compiler.getOp(innerExprOpPos);
          boolean prox = isProximateInnerExpr(compiler, innerExprOpPos);
          if(prox)
            return true;
        }

    }
    return false;
  }
  
  static boolean isProximateInnerExpr(Compiler compiler, int opPos)
  {
    int op = compiler.getOp(opPos);
    int innerExprOpPos = opPos+2;
    switch(op)
    {
      case OpCodes.OP_ARGUMENT:
        if(isProximateInnerExpr(compiler, innerExprOpPos))
          return true;
        break;
      case OpCodes.OP_VARIABLE:
      case OpCodes.OP_NUMBERLIT:
      case OpCodes.OP_LITERAL:
      case OpCodes.OP_LOCATIONPATH:
        break; // OK
      case OpCodes.OP_FUNCTION:
        boolean isProx = functionProximateOrContainsProximate(compiler, opPos);
        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(op);
        int rightPos = compiler.getNextOpPos(leftPos);
        isProx = isProximateInnerExpr(compiler, leftPos);
        if(isProx)
          return true;
        isProx = isProximateInnerExpr(compiler, rightPos);