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.Dictionary;
  import java.util.Vector;
  
  import org.apache.bcel.generic.GOTO_W;
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
  import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
  
  /**
   * A test sequence is a sequence of patterns that
   *
   *  (1) occured in templates in the same mode
   *  (2) share the same kernel node type (e.g. A/B and C/C/B)
   *  (3) may also contain patterns matching "*" and "node()"
   *      (element sequence only) or matching "@*" (attribute
   *      sequence only).
   *
   * A test sequence may have a default template, which will be 
   * instantiated if none of the other patterns match. 
   * @author Jacek Ambroziak
   * @author Santiago Pericas-Geertsen
   * @author Erwin Bolwidt <ejb@klomp.org>
   * @author Morten Jorgensen <morten.jorgensen@sun.com>
   */
  final class TestSeq {
  
      /**
       * Integer code for the kernel type of this test sequence
       */
      private int _kernelType;
  
      /**
       * Vector of all patterns in the test sequence. May include
       * patterns with "*", "@*" or "node()" kernel.
       */
      private Vector _patterns = null;
  
      /**
       * A reference to the Mode object.
       */
      private Mode _mode = null;
  
      /**
       * Default template for this test sequence
       */
      private Template _default = null;
  
      /**
       * Instruction list representing this test sequence.
       */
      private InstructionList _instructionList;
  
      /**
       * Cached handle to avoid compiling more than once.
       */
      private InstructionHandle _start = null;
  
      /**
       * Creates a new test sequence given a set of patterns and a mode.
       */
      public TestSeq(Vector patterns, Mode mode) {
  	this(patterns, -2, mode);
      }
  
      public TestSeq(Vector patterns, int kernelType, Mode mode) {
  	_patterns = patterns;
  	_kernelType = kernelType;
  	_mode = mode;
      }
  
      /**
       * Returns a string representation of this test sequence. Notice
       * that test sequences are mutable, so the value returned by this
       * method is different before and after calling reduce().
       */
      public String toString() {
  	final int count = _patterns.size();
  	final StringBuffer result = new StringBuffer();
  
  	for (int i = 0; i < count; i++) {
  	    final LocationPathPattern pattern =
  		(LocationPathPattern) _patterns.elementAt(i);
  
  	    if (i == 0) {
  		result.append("Testseq for kernel " + _kernelType)
  		      .append('\n');
  	    }
  	    result.append("   pattern " + i + ": ")
  	          .append(pattern.toString())
  		  .append('\n');
  	}
  	return result.toString();
      }
  
      /**
       * Returns the instruction list for this test sequence
       */
      public InstructionList getInstructionList() {
  	return _instructionList;
      }
  
      /**
       * Return the highest priority for a pattern in this test
       * sequence. This is either the priority of the first or
       * of the default pattern.
       */
      public double getPriority() {
  	final Template template = (_patterns.size() == 0) ? _default 
  	    : ((Pattern) _patterns.elementAt(0)).getTemplate();
  	return template.getPriority();
      }
  
      /**
       * Returns the position of the highest priority pattern in 
       * this test sequence.
       */
      public int getPosition() {
  	final Template template = (_patterns.size() == 0) ? _default 
  	    : ((Pattern) _patterns.elementAt(0)).getTemplate();
  	return template.getPosition();
      }
  
      /**
       * Reduce the patterns in this test sequence. Creates a new
       * vector of patterns and sets the default pattern if it
       * finds a patterns that is fully reduced.
       */
      public void reduce() {
  	final Vector newPatterns = new Vector();
  
  	final int count = _patterns.size();
  	for (int i = 0; i < count; i++) {
  	    final LocationPathPattern pattern =
  		(LocationPathPattern)_patterns.elementAt(i);
  		
  	    // Reduce this pattern
  	    pattern.reduceKernelPattern();
  			
  	    // Is this pattern fully reduced?
  	    if (pattern.isWildcard()) {
  		_default = pattern.getTemplate();
  		break; 		// Ignore following patterns 
  	    }
  	    else {
  		newPatterns.addElement(pattern);
  	    }
  	}
  	_patterns = newPatterns;
      }
  
      /**
       * Returns, by reference, the templates that are included in 
       * this test sequence. Note that a single template can occur 
       * in several test sequences if its pattern is a union.
       */
      public void findTemplates(Dictionary templates) {
  	if (_default != null) {
  	    templates.put(_default, this);
  	}
  	for (int i = 0; i < _patterns.size(); i++) {
  	    final LocationPathPattern pattern =
  		(LocationPathPattern)_patterns.elementAt(i);
  	    templates.put(pattern.getTemplate(), this);
  	}
      }
  
      /**
       * Get the instruction handle to a template's code. This is 
       * used when a single template occurs in several test 
       * sequences; that is, if its pattern is a union of patterns 
       * (e.g. match="A/B | A/C").
       */
      private InstructionHandle getTemplateHandle(Template template) {
  	return (InstructionHandle)_mode.getTemplateInstructionHandle(template);
      }
  
      /**
       * Returns pattern n in this test sequence
       */
      private LocationPathPattern getPattern(int n) {
  	return (LocationPathPattern)_patterns.elementAt(n);
      }
  
      /**
       * Compile the code for this test sequence. Compile patterns 
       * from highest to lowest priority. Note that since patterns 
       * can be share by multiple test sequences, instruction lists 
       * must be copied before backpatching.
       */
      public InstructionHandle compile(ClassGenerator classGen,
  				     MethodGenerator methodGen,
  				     InstructionHandle continuation) 
      {
  	// Returned cached value if already compiled
  	if (_start != null) {
  	    return _start;
  	}
  
  	// If not patterns, then return handle for default template
  	final int count = _patterns.size();
  	if (count == 0) {
  	    return (_start = getTemplateHandle(_default));
  	}
  
  	// Init handle to jump when all patterns failed
  	InstructionHandle fail = (_default == null) ? continuation
  	    : getTemplateHandle(_default);
  	
  	// Compile all patterns in reverse order
  	for (int n = count - 1; n >= 0; n--) {
  	    final LocationPathPattern pattern = getPattern(n);
  	    final Template template = pattern.getTemplate();
  	    final InstructionList il = new InstructionList();
  
  	    // Patterns expect current node on top of stack
  	    il.append(methodGen.loadCurrentNode());
  
  	    // Apply the test-code compiled for the pattern
  	    InstructionList ilist = methodGen.getInstructionList(pattern);
  	    if (ilist == null) {
  		ilist = pattern.compile(classGen, methodGen);
  		methodGen.addInstructionList(pattern, ilist);
  	    }
  
  	    // Make a copy of the instruction list for backpatching
  	    InstructionList copyOfilist = ilist.copy();
  
  	    FlowList trueList = pattern.getTrueList();
  	    if (trueList != null) {
  		trueList = trueList.copyAndRedirect(ilist, copyOfilist);
  	    }
  	    FlowList falseList = pattern.getFalseList();
  	    if (falseList != null) {
  		falseList = falseList.copyAndRedirect(ilist, copyOfilist);
  	    }
  
  	    il.append(copyOfilist);
  
  	    // On success branch to the template code
  	    final InstructionHandle gtmpl = getTemplateHandle(template);
  	    final InstructionHandle success = il.append(new GOTO_W(gtmpl));
  
  	    if (trueList != null) {
  		trueList.backPatch(success);
  	    }
  	    if (falseList != null) {
  		falseList.backPatch(fail);
  	    } 
  
  	    // Next pattern's 'fail' target is this pattern's first instruction
  	    fail = il.getStart();
  
  	    // Append existing instruction list to the end of this one
  	    if (_instructionList != null) {
  		il.append(_instructionList);
  	    }
  
  	    // Set current instruction list to be this one
  	    _instructionList = il;
  	}
  	return (_start = fail);
      }
  }
  