/*
 * 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: XPathParser.java 468655 2006-10-28 07:12:06Z minchau $
 */
package org.apache.xpath.compiler;

import javax.xml.transform.ErrorListener;
import javax.xml.transform.TransformerException;

import org.apache.xalan.res.XSLMessages;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xpath.XPathProcessorException;
import org.apache.xpath.domapi.XPathStylesheetDOM3Exception;
import org.apache.xpath.objects.XNumber;
import org.apache.xpath.objects.XString;
import org.apache.xpath.res.XPATHErrorResources;

Tokenizes and parses XPath expressions. This should really be named
XPathParserImpl, and may be renamed in the future.
@xsl.usage
general/**
 * Tokenizes and parses XPath expressions. This should really be named
 * XPathParserImpl, and may be renamed in the future.
 * @xsl.usage general
 */
public class XPathParser
{
	// %REVIEW% Is there a better way of doing this?
	// Upside is minimum object churn. Downside is that we don't have a useful
	// backtrace in the exception itself -- but we don't expect to need one.
	static public final String CONTINUE_AFTER_FATAL_ERROR="CONTINUE_AFTER_FATAL_ERROR";

  
The XPath to be processed.
/**
   * The XPath to be processed.
   */
  private OpMap m_ops;

  
The next token in the pattern.
/**
   * The next token in the pattern.
   */
  transient String m_token;

  
The first char in m_token, the theory being that this
is an optimization because we won't have to do charAt(0) as
often.
/**
   * The first char in m_token, the theory being that this
   * is an optimization because we won't have to do charAt(0) as
   * often.
   */
  transient char m_tokenChar = 0;

  
The position in the token queue is tracked by m_queueMark.
/**
   * The position in the token queue is tracked by m_queueMark.
   */
  int m_queueMark = 0;

  
Results from checking FilterExpr syntax
/**
   * Results from checking FilterExpr syntax
   */
  protected final static int FILTER_MATCH_FAILED     = 0;
  protected final static int FILTER_MATCH_PRIMARY    = 1;
  protected final static int FILTER_MATCH_PREDICATES = 2;

  
The parser constructor.
/**
   * The parser constructor.
   */
  public XPathParser(ErrorListener errorListener, javax.xml.transform.SourceLocator sourceLocator)
  {
    m_errorListener = errorListener;
    m_sourceLocator = sourceLocator;
  }

  
The prefix resolver to map prefixes to namespaces in the OpMap.
/**
   * The prefix resolver to map prefixes to namespaces in the OpMap.
   */
  PrefixResolver m_namespaceContext;

  
Given an string, init an XPath object for selections,
in order that a parse doesn't
have to be done each time the expression is evaluated.
Params:
compiler – The compiler object.
expression – A string conforming to the XPath grammar.
namespaceContext – An object that is able to resolve prefixes in
the XPath to namespaces.
Throws:
TransformerException – /**
   * Given an string, init an XPath object for selections,
   * in order that a parse doesn't
   * have to be done each time the expression is evaluated.
   * 
   * @param compiler The compiler object.
   * @param expression A string conforming to the XPath grammar.
   * @param namespaceContext An object that is able to resolve prefixes in
   * the XPath to namespaces.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public void initXPath(
          Compiler compiler, String expression, PrefixResolver namespaceContext)
            throws javax.xml.transform.TransformerException
  {

    m_ops = compiler;
    m_namespaceContext = namespaceContext;
    m_functionTable = compiler.getFunctionTable();

    Lexer lexer = new Lexer(compiler, namespaceContext, this);

    lexer.tokenize(expression);

    m_ops.setOp(0,OpCodes.OP_XPATH);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH,2);
    
    
	// Patch for Christine's gripe. She wants her errorHandler to return from
	// a fatal error and continue trying to parse, rather than throwing an exception.
	// Without the patch, that put us into an endless loop.
	//
	// %REVIEW% Is there a better way of doing this?
	// %REVIEW% Are there any other cases which need the safety net?
	// 	(and if so do we care right now, or should we rewrite the XPath
	//	grammar engine and can fix it at that time?)
	try {

      nextToken();
      Expr();

      if (null != m_token)
      {
        String extraTokens = "";

        while (null != m_token)
        {
          extraTokens += "'" + m_token + "'";

          nextToken();

          if (null != m_token)
            extraTokens += ", ";
        }

        error(XPATHErrorResources.ER_EXTRA_ILLEGAL_TOKENS,
              new Object[]{ extraTokens });  //"Extra illegal tokens: "+extraTokens);
      }

    } 
    catch (org.apache.xpath.XPathProcessorException e)
    {
	  if(CONTINUE_AFTER_FATAL_ERROR.equals(e.getMessage()))
	  {
		// What I _want_ to do is null out this XPath.
		// I doubt this has the desired effect, but I'm not sure what else to do.
		// %REVIEW%!!!
		initXPath(compiler, "/..",  namespaceContext);
	  }
	  else
		throw e;
    }

    compiler.shrink();
  }

  
Given an string, init an XPath object for pattern matches,
in order that a parse doesn't
have to be done each time the expression is evaluated.
Params:
compiler – The XPath object to be initialized.
expression – A String representing the XPath.
namespaceContext – An object that is able to resolve prefixes in
the XPath to namespaces.
Throws:
TransformerException – /**
   * Given an string, init an XPath object for pattern matches,
   * in order that a parse doesn't
   * have to be done each time the expression is evaluated.
   * @param compiler The XPath object to be initialized.
   * @param expression A String representing the XPath.
   * @param namespaceContext An object that is able to resolve prefixes in
   * the XPath to namespaces.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public void initMatchPattern(
          Compiler compiler, String expression, PrefixResolver namespaceContext)
            throws javax.xml.transform.TransformerException
  {

    m_ops = compiler;
    m_namespaceContext = namespaceContext;
    m_functionTable = compiler.getFunctionTable();

    Lexer lexer = new Lexer(compiler, namespaceContext, this);

    lexer.tokenize(expression);

    m_ops.setOp(0, OpCodes.OP_MATCHPATTERN);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, 2);

    nextToken();
    Pattern();

    if (null != m_token)
    {
      String extraTokens = "";

      while (null != m_token)
      {
        extraTokens += "'" + m_token + "'";

        nextToken();

        if (null != m_token)
          extraTokens += ", ";
      }

      error(XPATHErrorResources.ER_EXTRA_ILLEGAL_TOKENS,
            new Object[]{ extraTokens });  //"Extra illegal tokens: "+extraTokens);
    }

    // Terminate for safety.
    m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.ENDOP);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH)+1);

    m_ops.shrink();
  }

  
The error listener where syntax errors are to be sent.
/** The error listener where syntax errors are to be sent.
   */
  private ErrorListener m_errorListener;
  
  
The source location of the XPath. /** The source location of the XPath. */
  javax.xml.transform.SourceLocator m_sourceLocator;
  
  
The table contains build-in functions and customized functions /** The table contains build-in functions and customized functions */
  private FunctionTable m_functionTable;

  
Allow an application to register an error event handler, where syntax 
errors will be sent.  If the error listener is not set, syntax errors 
will be sent to System.err.
Params:
handler – Reference to error listener where syntax errors will be 
               sent./**
   * Allow an application to register an error event handler, where syntax 
   * errors will be sent.  If the error listener is not set, syntax errors 
   * will be sent to System.err.
   * 
   * @param handler Reference to error listener where syntax errors will be 
   *                sent.
   */
  public void setErrorHandler(ErrorListener handler)
  {
    m_errorListener = handler;
  }

  
Return the current error listener.
Returns:
The error listener, which should not normally be null, but may be./**
   * Return the current error listener.
   *
   * @return The error listener, which should not normally be null, but may be.
   */
  public ErrorListener getErrorListener()
  {
    return m_errorListener;
  }

  
Check whether m_token matches the target string. 
Params:
s – A string reference or null.
Returns:
If m_token is null, returns false (or true if s is also null), or 
return true if the current token matches the string, else false./**
   * Check whether m_token matches the target string. 
   *
   * @param s A string reference or null.
   *
   * @return If m_token is null, returns false (or true if s is also null), or 
   * return true if the current token matches the string, else false.
   */
  final boolean tokenIs(String s)
  {
    return (m_token != null) ? (m_token.equals(s)) : (s == null);
  }

  
Check whether m_tokenChar==c. 
Params:
c – A character to be tested.
Returns:
If m_token is null, returns false, or return true if c matches 
        the current token./**
   * Check whether m_tokenChar==c. 
   *
   * @param c A character to be tested.
   *
   * @return If m_token is null, returns false, or return true if c matches 
   *         the current token.
   */
  final boolean tokenIs(char c)
  {
    return (m_token != null) ? (m_tokenChar == c) : false;
  }

  
Look ahead of the current token in order to
make a branching decision.
Params:
c – the character to be tested for.
n – number of tokens to look ahead.  Must be
greater than 1.
Returns:
true if the next token matches the character argument./**
   * Look ahead of the current token in order to
   * make a branching decision.
   *
   * @param c the character to be tested for.
   * @param n number of tokens to look ahead.  Must be
   * greater than 1.
   *
   * @return true if the next token matches the character argument.
   */
  final boolean lookahead(char c, int n)
  {

    int pos = (m_queueMark + n);
    boolean b;

    if ((pos <= m_ops.getTokenQueueSize()) && (pos > 0)
            && (m_ops.getTokenQueueSize() != 0))
    {
      String tok = ((String) m_ops.m_tokenQueue.elementAt(pos - 1));

      b = (tok.length() == 1) ? (tok.charAt(0) == c) : false;
    }
    else
    {
      b = false;
    }

    return b;
  }

  
Look behind the first character of the current token in order to
make a branching decision.
Params:
c – the character to compare it to.
n – number of tokens to look behind.  Must be
greater than 1.  Note that the look behind terminates
at either the beginning of the string or on a '|'
character.  Because of this, this method should only
be used for pattern matching.
Returns:
true if the token behind the current token matches the character 
        argument./**
   * Look behind the first character of the current token in order to
   * make a branching decision.
   * 
   * @param c the character to compare it to.
   * @param n number of tokens to look behind.  Must be
   * greater than 1.  Note that the look behind terminates
   * at either the beginning of the string or on a '|'
   * character.  Because of this, this method should only
   * be used for pattern matching.
   *
   * @return true if the token behind the current token matches the character 
   *         argument.
   */
  private final boolean lookbehind(char c, int n)
  {

    boolean isToken;
    int lookBehindPos = m_queueMark - (n + 1);

    if (lookBehindPos >= 0)
    {
      String lookbehind = (String) m_ops.m_tokenQueue.elementAt(lookBehindPos);

      if (lookbehind.length() == 1)
      {
        char c0 = (lookbehind == null) ? '|' : lookbehind.charAt(0);

        isToken = (c0 == '|') ? false : (c0 == c);
      }
      else
      {
        isToken = false;
      }
    }
    else
    {
      isToken = false;
    }

    return isToken;
  }

  
look behind the current token in order to
see if there is a useable token.
Params:
n – number of tokens to look behind.  Must be
greater than 1.  Note that the look behind terminates
at either the beginning of the string or on a '|'
character.  Because of this, this method should only
be used for pattern matching.
Returns:
true if look behind has a token, false otherwise./**
   * look behind the current token in order to
   * see if there is a useable token.
   * 
   * @param n number of tokens to look behind.  Must be
   * greater than 1.  Note that the look behind terminates
   * at either the beginning of the string or on a '|'
   * character.  Because of this, this method should only
   * be used for pattern matching.
   * 
   * @return true if look behind has a token, false otherwise.
   */
  private final boolean lookbehindHasToken(int n)
  {

    boolean hasToken;

    if ((m_queueMark - n) > 0)
    {
      String lookbehind = (String) m_ops.m_tokenQueue.elementAt(m_queueMark - (n - 1));
      char c0 = (lookbehind == null) ? '|' : lookbehind.charAt(0);

      hasToken = (c0 == '|') ? false : true;
    }
    else
    {
      hasToken = false;
    }

    return hasToken;
  }

  
Look ahead of the current token in order to
make a branching decision.
Params:
s – the string to compare it to.
n – number of tokens to lookahead.  Must be
greater than 1.
Returns:
true if the token behind the current token matches the string 
        argument./**
   * Look ahead of the current token in order to
   * make a branching decision.
   * 
   * @param s the string to compare it to.
   * @param n number of tokens to lookahead.  Must be
   * greater than 1.
   *
   * @return true if the token behind the current token matches the string 
   *         argument.
   */
  private final boolean lookahead(String s, int n)
  {

    boolean isToken;

    if ((m_queueMark + n) <= m_ops.getTokenQueueSize())
    {
      String lookahead = (String) m_ops.m_tokenQueue.elementAt(m_queueMark + (n - 1));

      isToken = (lookahead != null) ? lookahead.equals(s) : (s == null);
    }
    else
    {
      isToken = (null == s);
    }

    return isToken;
  }

  
Retrieve the next token from the command and
store it in m_token string.
/**
   * Retrieve the next token from the command and
   * store it in m_token string.
   */
  private final void nextToken()
  {

    if (m_queueMark < m_ops.getTokenQueueSize())
    {
      m_token = (String) m_ops.m_tokenQueue.elementAt(m_queueMark++);
      m_tokenChar = m_token.charAt(0);
    }
    else
    {
      m_token = null;
      m_tokenChar = 0;
    }
  }

  
Retrieve a token relative to the current token.
Params:
i – Position relative to current token.
Returns:
The string at the given index, or null if the index is out 
        of range./**
   * Retrieve a token relative to the current token.
   * 
   * @param i Position relative to current token.
   *
   * @return The string at the given index, or null if the index is out 
   *         of range.
   */
  private final String getTokenRelative(int i)
  {

    String tok;
    int relative = m_queueMark + i;

    if ((relative > 0) && (relative < m_ops.getTokenQueueSize()))
    {
      tok = (String) m_ops.m_tokenQueue.elementAt(relative);
    }
    else
    {
      tok = null;
    }

    return tok;
  }

  
Retrieve the previous token from the command and
store it in m_token string.
/**
   * Retrieve the previous token from the command and
   * store it in m_token string.
   */
  private final void prevToken()
  {

    if (m_queueMark > 0)
    {
      m_queueMark--;

      m_token = (String) m_ops.m_tokenQueue.elementAt(m_queueMark);
      m_tokenChar = m_token.charAt(0);
    }
    else
    {
      m_token = null;
      m_tokenChar = 0;
    }
  }

  
Consume an expected token, throwing an exception if it
isn't there.
Params:
expected – The string to be expected.
Throws:
TransformerException – /**
   * Consume an expected token, throwing an exception if it
   * isn't there.
   *
   * @param expected The string to be expected.
   *
   * @throws javax.xml.transform.TransformerException
   */
  private final void consumeExpected(String expected)
          throws javax.xml.transform.TransformerException
  {

    if (tokenIs(expected))
    {
      nextToken();
    }
    else
    {
      error(XPATHErrorResources.ER_EXPECTED_BUT_FOUND, new Object[]{ expected,
                                                                     m_token });  //"Expected "+expected+", but found: "+m_token);

	  // Patch for Christina's gripe. She wants her errorHandler to return from
	  // this error and continue trying to parse, rather than throwing an exception.
	  // Without the patch, that put us into an endless loop.
		throw new XPathProcessorException(CONTINUE_AFTER_FATAL_ERROR);
	}
  }

  
Consume an expected token, throwing an exception if it
isn't there.
Params:
expected – the character to be expected.
Throws:
TransformerException – /**
   * Consume an expected token, throwing an exception if it
   * isn't there.
   *
   * @param expected the character to be expected.
   *
   * @throws javax.xml.transform.TransformerException
   */
  private final void consumeExpected(char expected)
          throws javax.xml.transform.TransformerException
  {

    if (tokenIs(expected))
    {
      nextToken();
    }
    else
    {
      error(XPATHErrorResources.ER_EXPECTED_BUT_FOUND,
            new Object[]{ String.valueOf(expected),
                          m_token });  //"Expected "+expected+", but found: "+m_token);

	  // Patch for Christina's gripe. She wants her errorHandler to return from
	  // this error and continue trying to parse, rather than throwing an exception.
	  // Without the patch, that put us into an endless loop.
		throw new XPathProcessorException(CONTINUE_AFTER_FATAL_ERROR);
    }
  }

  
Warn the user of a problem.
Params:
msg – An error msgkey that corresponds to one of the constants found in XPATHErrorResources, which is a key for a format string.
args – An array of arguments represented in the format string, which 
            may be null.
Throws:
TransformerException – if the current ErrorListoner determines to 
                             throw an exception./**
   * Warn the user of a problem.
   *
   * @param msg An error msgkey that corresponds to one of the constants found 
   *            in {@link org.apache.xpath.res.XPATHErrorResources}, which is 
   *            a key for a format string.
   * @param args An array of arguments represented in the format string, which 
   *             may be null.
   *
   * @throws TransformerException if the current ErrorListoner determines to 
   *                              throw an exception.
   */
  void warn(String msg, Object[] args) throws TransformerException
  {

    String fmsg = XSLMessages.createXPATHWarning(msg, args);
    ErrorListener ehandler = this.getErrorListener();

    if (null != ehandler)
    {
      // TO DO: Need to get stylesheet Locator from here.
      ehandler.warning(new TransformerException(fmsg, m_sourceLocator));
    }
    else
    {
      // Should never happen.
      System.err.println(fmsg);
    }
  }

  
Notify the user of an assertion error, and probably throw an
exception.
Params:
b –  If false, a runtime exception will be thrown.
msg – The assertion message, which should be informative.
Throws:
RuntimeException – if the b argument is false./**
   * Notify the user of an assertion error, and probably throw an
   * exception.
   *
   * @param b  If false, a runtime exception will be thrown.
   * @param msg The assertion message, which should be informative.
   * 
   * @throws RuntimeException if the b argument is false.
   */
  private void assertion(boolean b, String msg)
  {

    if (!b)
    {
      String fMsg = XSLMessages.createXPATHMessage(
        XPATHErrorResources.ER_INCORRECT_PROGRAMMER_ASSERTION,
        new Object[]{ msg });

      throw new RuntimeException(fMsg);
    }
  }

  
Notify the user of an error, and probably throw an
exception.
Params:
msg – An error msgkey that corresponds to one of the constants found in XPATHErrorResources, which is a key for a format string.
args – An array of arguments represented in the format string, which 
            may be null.
Throws:
TransformerException – if the current ErrorListoner determines to 
                             throw an exception./**
   * Notify the user of an error, and probably throw an
   * exception.
   *
   * @param msg An error msgkey that corresponds to one of the constants found 
   *            in {@link org.apache.xpath.res.XPATHErrorResources}, which is 
   *            a key for a format string.
   * @param args An array of arguments represented in the format string, which 
   *             may be null.
   *
   * @throws TransformerException if the current ErrorListoner determines to 
   *                              throw an exception.
   */
  void error(String msg, Object[] args) throws TransformerException
  {

    String fmsg = XSLMessages.createXPATHMessage(msg, args);
    ErrorListener ehandler = this.getErrorListener();

    TransformerException te = new TransformerException(fmsg, m_sourceLocator);
    if (null != ehandler)
    {
      // TO DO: Need to get stylesheet Locator from here.
      ehandler.fatalError(te);
    }
    else
    {
      // System.err.println(fmsg);
      throw te;
    }
  }

  
This method is added to support DOM 3 XPath API.

This method is exactly like error(String, Object[]); except that
the underlying TransformerException is 
XpathStylesheetDOM3Exception (which extends TransformerException).

So older XPath code in Xalan is not affected by this. To older XPath code
the behavior of whether error() or errorForDOM3() is called because it is
always catching TransformerException objects and is oblivious to
the new subclass of XPathStylesheetDOM3Exception. Older XPath code 
runs as before.

However, newer DOM3 XPath code upon catching a TransformerException can
can check if the exception is an instance of XPathStylesheetDOM3Exception
and take appropriate action.
Params:
msg – An error msgkey that corresponds to one of the constants found in XPATHErrorResources, which is a key for a format string.
args – An array of arguments represented in the format string, which 
            may be null.
Throws:
TransformerException – if the current ErrorListoner determines to 
                             throw an exception./**
   * This method is added to support DOM 3 XPath API.
   * <p>
   * This method is exactly like error(String, Object[]); except that
   * the underlying TransformerException is 
   * XpathStylesheetDOM3Exception (which extends TransformerException).
   * <p>
   * So older XPath code in Xalan is not affected by this. To older XPath code
   * the behavior of whether error() or errorForDOM3() is called because it is
   * always catching TransformerException objects and is oblivious to
   * the new subclass of XPathStylesheetDOM3Exception. Older XPath code 
   * runs as before.
   * <p>
   * However, newer DOM3 XPath code upon catching a TransformerException can
   * can check if the exception is an instance of XPathStylesheetDOM3Exception
   * and take appropriate action.
   * 
   * @param msg An error msgkey that corresponds to one of the constants found 
   *            in {@link org.apache.xpath.res.XPATHErrorResources}, which is 
   *            a key for a format string.
   * @param args An array of arguments represented in the format string, which 
   *             may be null.
   *
   * @throws TransformerException if the current ErrorListoner determines to 
   *                              throw an exception.
   */
  void errorForDOM3(String msg, Object[] args) throws TransformerException
  {

	String fmsg = XSLMessages.createXPATHMessage(msg, args);
	ErrorListener ehandler = this.getErrorListener();

	TransformerException te = new XPathStylesheetDOM3Exception(fmsg, m_sourceLocator);
	if (null != ehandler)
	{
	  // TO DO: Need to get stylesheet Locator from here.
	  ehandler.fatalError(te);
	}
	else
	{
	  // System.err.println(fmsg);
	  throw te;
	}
  }
  
Dump the remaining token queue.
Thanks to Craig for this.
Returns:
A dump of the remaining token queue, which may be appended to 
        an error message./**
   * Dump the remaining token queue.
   * Thanks to Craig for this.
   *
   * @return A dump of the remaining token queue, which may be appended to 
   *         an error message.
   */
  protected String dumpRemainingTokenQueue()
  {

    int q = m_queueMark;
    String returnMsg;

    if (q < m_ops.getTokenQueueSize())
    {
      String msg = "\n Remaining tokens: (";

      while (q < m_ops.getTokenQueueSize())
      {
        String t = (String) m_ops.m_tokenQueue.elementAt(q++);

        msg += (" '" + t + "'");
      }

      returnMsg = msg + ")";
    }
    else
    {
      returnMsg = "";
    }

    return returnMsg;
  }

  
Given a string, return the corresponding function token.
Params:
key – A local name of a function.
Returns:
 The function ID, which may correspond to one of the FUNC_XXX values found in FunctionTable, but may be a value installed by an external module./**
   * Given a string, return the corresponding function token.
   *
   * @param key A local name of a function.
   *
   * @return   The function ID, which may correspond to one of the FUNC_XXX 
   *    values found in {@link org.apache.xpath.compiler.FunctionTable}, but may 
   *    be a value installed by an external module.
   */
  final int getFunctionToken(String key)
  {

    int tok;
    
    Object id;

    try
    {
      // These are nodetests, xpathparser treats them as functions when parsing
      // a FilterExpr. 
      id = Keywords.lookupNodeTest(key);
      if (null == id) id = m_functionTable.getFunctionID(key);
      tok = ((Integer) id).intValue();
    }
    catch (NullPointerException npe)
    {
      tok = -1;
    }
    catch (ClassCastException cce)
    {
      tok = -1;
    }

    return tok;
  }

  
Insert room for operation.  This will NOT set
the length value of the operation, but will update
the length value for the total expression.
Params:
pos – The position where the op is to be inserted.
length – The length of the operation space in the op map.
op – The op code to the inserted./**
   * Insert room for operation.  This will NOT set
   * the length value of the operation, but will update
   * the length value for the total expression.
   *
   * @param pos The position where the op is to be inserted.
   * @param length The length of the operation space in the op map.
   * @param op The op code to the inserted.
   */
  void insertOp(int pos, int length, int op)
  {

    int totalLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    for (int i = totalLen - 1; i >= pos; i--)
    {
      m_ops.setOp(i + length, m_ops.getOp(i));
    }

    m_ops.setOp(pos,op);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH,totalLen + length);
  }

  
Insert room for operation.  This WILL set
the length value of the operation, and will update
the length value for the total expression.
Params:
length – The length of the operation.
op – The op code to the inserted./**
   * Insert room for operation.  This WILL set
   * the length value of the operation, and will update
   * the length value for the total expression.
   *
   * @param length The length of the operation.
   * @param op The op code to the inserted.
   */
  void appendOp(int length, int op)
  {

    int totalLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    m_ops.setOp(totalLen, op);
    m_ops.setOp(totalLen + OpMap.MAPINDEX_LENGTH, length);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, totalLen + length);
  }

  // ============= EXPRESSIONS FUNCTIONS =================

  
Expr  ::=  OrExpr
Throws:
TransformerException – /**
   *
   *
   * Expr  ::=  OrExpr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void Expr() throws javax.xml.transform.TransformerException
  {
    OrExpr();
  }

  
OrExpr  ::=  AndExpr
| OrExpr 'or' AndExpr
Throws:
TransformerException – /**
   *
   *
   * OrExpr  ::=  AndExpr
   * | OrExpr 'or' AndExpr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void OrExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    AndExpr();

    if ((null != m_token) && tokenIs("or"))
    {
      nextToken();
      insertOp(opPos, 2, OpCodes.OP_OR);
      OrExpr();

      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
        m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
    }
  }

  
AndExpr  ::=  EqualityExpr
| AndExpr 'and' EqualityExpr
Throws:
TransformerException – /**
   *
   *
   * AndExpr  ::=  EqualityExpr
   * | AndExpr 'and' EqualityExpr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void AndExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    EqualityExpr(-1);

    if ((null != m_token) && tokenIs("and"))
    {
      nextToken();
      insertOp(opPos, 2, OpCodes.OP_AND);
      AndExpr();

      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
        m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
    }
  }

  
Params:
addPos – Position where expression is to be added, or -1 for append.
Throws:
TransformerException – 
@returns
an Object which is either a String, a Number, a Boolean, or a vector
of nodes.
EqualityExpr  ::=  RelationalExpr
| EqualityExpr '=' RelationalExpr
Returns:
the position at the end of the equality expression./**
   *
   * @returns an Object which is either a String, a Number, a Boolean, or a vector
   * of nodes.
   *
   * EqualityExpr  ::=  RelationalExpr
   * | EqualityExpr '=' RelationalExpr
   *
   *
   * @param addPos Position where expression is to be added, or -1 for append.
   *
   * @return the position at the end of the equality expression.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected int EqualityExpr(int addPos) throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    if (-1 == addPos)
      addPos = opPos;

    RelationalExpr(-1);

    if (null != m_token)
    {
      if (tokenIs('!') && lookahead('=', 1))
      {
        nextToken();
        nextToken();
        insertOp(addPos, 2, OpCodes.OP_NOTEQUALS);

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = EqualityExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
      else if (tokenIs('='))
      {
        nextToken();
        insertOp(addPos, 2, OpCodes.OP_EQUALS);

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = EqualityExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
    }

    return addPos;
  }

  
.
Params:
addPos – Position where expression is to be added, or -1 for append.
Throws:
TransformerException – 
@returns
an Object which is either a String, a Number, a Boolean, or a vector
of nodes.
RelationalExpr  ::=  AdditiveExpr
| RelationalExpr '<' AdditiveExpr
| RelationalExpr '>' AdditiveExpr
| RelationalExpr '<=' AdditiveExpr
| RelationalExpr '>=' AdditiveExpr
Returns:
the position at the end of the relational expression./**
   * .
   * @returns an Object which is either a String, a Number, a Boolean, or a vector
   * of nodes.
   *
   * RelationalExpr  ::=  AdditiveExpr
   * | RelationalExpr '<' AdditiveExpr
   * | RelationalExpr '>' AdditiveExpr
   * | RelationalExpr '<=' AdditiveExpr
   * | RelationalExpr '>=' AdditiveExpr
   *
   *
   * @param addPos Position where expression is to be added, or -1 for append.
   *
   * @return the position at the end of the relational expression.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected int RelationalExpr(int addPos) throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    if (-1 == addPos)
      addPos = opPos;

    AdditiveExpr(-1);

    if (null != m_token)
    {
      if (tokenIs('<'))
      {
        nextToken();

        if (tokenIs('='))
        {
          nextToken();
          insertOp(addPos, 2, OpCodes.OP_LTE);
        }
        else
        {
          insertOp(addPos, 2, OpCodes.OP_LT);
        }

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = RelationalExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH, 
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
      else if (tokenIs('>'))
      {
        nextToken();

        if (tokenIs('='))
        {
          nextToken();
          insertOp(addPos, 2, OpCodes.OP_GTE);
        }
        else
        {
          insertOp(addPos, 2, OpCodes.OP_GT);
        }

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = RelationalExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
    }

    return addPos;
  }

  
This has to handle construction of the operations so that they are evaluated
in pre-fix order.  So, for 9+7-6, instead of |+|9|-|7|6|, this needs to be
evaluated as |-|+|9|7|6|.
AdditiveExpr  ::=  MultiplicativeExpr
| AdditiveExpr '+' MultiplicativeExpr
| AdditiveExpr '-' MultiplicativeExpr
Params:
addPos – Position where expression is to be added, or -1 for append.
Throws:
TransformerException – 
Returns:
the position at the end of the equality expression./**
   * This has to handle construction of the operations so that they are evaluated
   * in pre-fix order.  So, for 9+7-6, instead of |+|9|-|7|6|, this needs to be
   * evaluated as |-|+|9|7|6|.
   *
   * AdditiveExpr  ::=  MultiplicativeExpr
   * | AdditiveExpr '+' MultiplicativeExpr
   * | AdditiveExpr '-' MultiplicativeExpr
   *
   *
   * @param addPos Position where expression is to be added, or -1 for append.
   *
   * @return the position at the end of the equality expression.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected int AdditiveExpr(int addPos) throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    if (-1 == addPos)
      addPos = opPos;

    MultiplicativeExpr(-1);

    if (null != m_token)
    {
      if (tokenIs('+'))
      {
        nextToken();
        insertOp(addPos, 2, OpCodes.OP_PLUS);

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = AdditiveExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
      else if (tokenIs('-'))
      {
        nextToken();
        insertOp(addPos, 2, OpCodes.OP_MINUS);

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = AdditiveExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH, 
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
    }

    return addPos;
  }

  
This has to handle construction of the operations so that they are evaluated
in pre-fix order.  So, for 9+7-6, instead of |+|9|-|7|6|, this needs to be
evaluated as |-|+|9|7|6|.
MultiplicativeExpr  ::=  UnaryExpr
| MultiplicativeExpr MultiplyOperator UnaryExpr
| MultiplicativeExpr 'div' UnaryExpr
| MultiplicativeExpr 'mod' UnaryExpr
| MultiplicativeExpr 'quo' UnaryExpr
Params:
addPos – Position where expression is to be added, or -1 for append.
Throws:
TransformerException – 
Returns:
the position at the end of the equality expression./**
   * This has to handle construction of the operations so that they are evaluated
   * in pre-fix order.  So, for 9+7-6, instead of |+|9|-|7|6|, this needs to be
   * evaluated as |-|+|9|7|6|.
   *
   * MultiplicativeExpr  ::=  UnaryExpr
   * | MultiplicativeExpr MultiplyOperator UnaryExpr
   * | MultiplicativeExpr 'div' UnaryExpr
   * | MultiplicativeExpr 'mod' UnaryExpr
   * | MultiplicativeExpr 'quo' UnaryExpr
   *
   * @param addPos Position where expression is to be added, or -1 for append.
   *
   * @return the position at the end of the equality expression.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected int MultiplicativeExpr(int addPos) throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    if (-1 == addPos)
      addPos = opPos;

    UnaryExpr();

    if (null != m_token)
    {
      if (tokenIs('*'))
      {
        nextToken();
        insertOp(addPos, 2, OpCodes.OP_MULT);

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = MultiplicativeExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
      else if (tokenIs("div"))
      {
        nextToken();
        insertOp(addPos, 2, OpCodes.OP_DIV);

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = MultiplicativeExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
      else if (tokenIs("mod"))
      {
        nextToken();
        insertOp(addPos, 2, OpCodes.OP_MOD);

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = MultiplicativeExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
      else if (tokenIs("quo"))
      {
        nextToken();
        insertOp(addPos, 2, OpCodes.OP_QUO);

        int opPlusLeftHandLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - addPos;

        addPos = MultiplicativeExpr(addPos);
        m_ops.setOp(addPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(addPos + opPlusLeftHandLen + 1) + opPlusLeftHandLen);
        addPos += 2;
      }
    }

    return addPos;
  }

  
UnaryExpr  ::=  UnionExpr
| '-' UnaryExpr
Throws:
TransformerException – /**
   *
   * UnaryExpr  ::=  UnionExpr
   * | '-' UnaryExpr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void UnaryExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);
    boolean isNeg = false;

    if (m_tokenChar == '-')
    {
      nextToken();
      appendOp(2, OpCodes.OP_NEG);

      isNeg = true;
    }

    UnionExpr();

    if (isNeg)
      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
        m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
  }

  
StringExpr  ::=  Expr
Throws:
TransformerException – /**
   *
   * StringExpr  ::=  Expr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void StringExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    appendOp(2, OpCodes.OP_STRING);
    Expr();

    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
  }

  
StringExpr  ::=  Expr
Throws:
TransformerException – /**
   *
   *
   * StringExpr  ::=  Expr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void BooleanExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    appendOp(2, OpCodes.OP_BOOL);
    Expr();

    int opLen = m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos;

    if (opLen == 2)
    {
      error(XPATHErrorResources.ER_BOOLEAN_ARG_NO_LONGER_OPTIONAL, null);  //"boolean(...) argument is no longer optional with 19990709 XPath draft.");
    }

    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH, opLen);
  }

  
NumberExpr  ::=  Expr
Throws:
TransformerException – /**
   *
   *
   * NumberExpr  ::=  Expr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void NumberExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    appendOp(2, OpCodes.OP_NUMBER);
    Expr();

    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
  }

  
The context of the right hand side expressions is the context of the
left hand side expression. The results of the right hand side expressions
are node sets. The result of the left hand side UnionExpr is the union
of the results of the right hand side expressions.
UnionExpr    ::=    PathExpr
| UnionExpr '|' PathExpr
Throws:
TransformerException – /**
   * The context of the right hand side expressions is the context of the
   * left hand side expression. The results of the right hand side expressions
   * are node sets. The result of the left hand side UnionExpr is the union
   * of the results of the right hand side expressions.
   *
   *
   * UnionExpr    ::=    PathExpr
   * | UnionExpr '|' PathExpr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void UnionExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);
    boolean continueOrLoop = true;
    boolean foundUnion = false;

    do
    {
      PathExpr();

      if (tokenIs('|'))
      {
        if (false == foundUnion)
        {
          foundUnion = true;

          insertOp(opPos, 2, OpCodes.OP_UNION);
        }

        nextToken();
      }
      else
      {
        break;
      }

      // this.m_testForDocOrder = true;
    }
    while (continueOrLoop);

    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
  }

  
PathExpr  ::=  LocationPath
| FilterExpr
| FilterExpr '/' RelativeLocationPath
| FilterExpr '//' RelativeLocationPath
Throws:
XSLProcessorException – thrown if the active ProblemListener and XPathContext decide
the error condition is severe enough to halt processing.
TransformerException – /**
   * PathExpr  ::=  LocationPath
   * | FilterExpr
   * | FilterExpr '/' RelativeLocationPath
   * | FilterExpr '//' RelativeLocationPath
   *
   * @throws XSLProcessorException thrown if the active ProblemListener and XPathContext decide
   * the error condition is severe enough to halt processing.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void PathExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    int filterExprMatch = FilterExpr();

    if (filterExprMatch != FILTER_MATCH_FAILED)
    {
      // If FilterExpr had Predicates, a OP_LOCATIONPATH opcode would already
      // have been inserted.
      boolean locationPathStarted = (filterExprMatch==FILTER_MATCH_PREDICATES);

      if (tokenIs('/'))
      {
        nextToken();

        if (!locationPathStarted)
        {
          // int locationPathOpPos = opPos;
          insertOp(opPos, 2, OpCodes.OP_LOCATIONPATH);

          locationPathStarted = true;
        }

        if (!RelativeLocationPath())
        {
          // "Relative location path expected following '/' or '//'"
          error(XPATHErrorResources.ER_EXPECTED_REL_LOC_PATH, null);
        }

      }

      // Terminate for safety.
      if (locationPathStarted)
      {
        m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.ENDOP);
        m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);
        m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
      }
    }
    else
    {
      LocationPath();
    }
  }

  
FilterExpr  ::=  PrimaryExpr
| FilterExpr Predicate
Throws:
XSLProcessorException – thrown if the active ProblemListener and XPathContext decide
the error condition is severe enough to halt processing.
TransformerException – 
Returns:
 FILTER_MATCH_PREDICATES, if this method successfully matched a
         FilterExpr with one or more Predicates;
         FILTER_MATCH_PRIMARY, if this method successfully matched a
         FilterExpr that was just a PrimaryExpr; or
         FILTER_MATCH_FAILED, if this method did not match a FilterExpr/**
   *
   *
   * FilterExpr  ::=  PrimaryExpr
   * | FilterExpr Predicate
   *
   * @throws XSLProcessorException thrown if the active ProblemListener and XPathContext decide
   * the error condition is severe enough to halt processing.
   *
   * @return  FILTER_MATCH_PREDICATES, if this method successfully matched a
   *          FilterExpr with one or more Predicates;
   *          FILTER_MATCH_PRIMARY, if this method successfully matched a
   *          FilterExpr that was just a PrimaryExpr; or
   *          FILTER_MATCH_FAILED, if this method did not match a FilterExpr
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected int FilterExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    int filterMatch;

    if (PrimaryExpr())
    {
      if (tokenIs('['))
      {

        // int locationPathOpPos = opPos;
        insertOp(opPos, 2, OpCodes.OP_LOCATIONPATH);

        while (tokenIs('['))
        {
          Predicate();
        }

        filterMatch = FILTER_MATCH_PREDICATES;
      }
      else
      {
        filterMatch = FILTER_MATCH_PRIMARY;
      }
    }
    else
    {
      filterMatch = FILTER_MATCH_FAILED;
    }

    return filterMatch;

    /*
     * if(tokenIs('['))
     * {
     *   Predicate();
     *   m_ops.m_opMap[opPos + OpMap.MAPINDEX_LENGTH] = m_ops.m_opMap[OpMap.MAPINDEX_LENGTH] - opPos;
     * }
     */
  }

  
PrimaryExpr  ::=  VariableReference
| '(' Expr ')'
| Literal
| Number
| FunctionCall
Throws:
TransformerException – 
Returns:
true if this method successfully matched a PrimaryExpr/**
   *
   * PrimaryExpr  ::=  VariableReference
   * | '(' Expr ')'
   * | Literal
   * | Number
   * | FunctionCall
   *
   * @return true if this method successfully matched a PrimaryExpr
   *
   * @throws javax.xml.transform.TransformerException
   *
   */
  protected boolean PrimaryExpr() throws javax.xml.transform.TransformerException
  {

    boolean matchFound;
    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    if ((m_tokenChar == '\'') || (m_tokenChar == '"'))
    {
      appendOp(2, OpCodes.OP_LITERAL);
      Literal();

      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH, 
        m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

      matchFound = true;
    }
    else if (m_tokenChar == '$')
    {
      nextToken();  // consume '$'
      appendOp(2, OpCodes.OP_VARIABLE);
      QName();
      
      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
        m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

      matchFound = true;
    }
    else if (m_tokenChar == '(')
    {
      nextToken();
      appendOp(2, OpCodes.OP_GROUP);
      Expr();
      consumeExpected(')');

      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
        m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

      matchFound = true;
    }
    else if ((null != m_token) && ((('.' == m_tokenChar) && (m_token.length() > 1) && Character.isDigit(
            m_token.charAt(1))) || Character.isDigit(m_tokenChar)))
    {
      appendOp(2, OpCodes.OP_NUMBERLIT);
      Number();

      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
        m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

      matchFound = true;
    }
    else if (lookahead('(', 1) || (lookahead(':', 1) && lookahead('(', 3)))
    {
      matchFound = FunctionCall();
    }
    else
    {
      matchFound = false;
    }

    return matchFound;
  }

  
Argument    ::=    Expr
Throws:
TransformerException – /**
   *
   * Argument    ::=    Expr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void Argument() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    appendOp(2, OpCodes.OP_ARGUMENT);
    Expr();

    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
  }

  
FunctionCall    ::=    FunctionName '(' ( Argument ( ',' Argument)*)? ')'
Throws:
TransformerException – 
Returns:
true if, and only if, a FunctionCall was matched/**
   *
   * FunctionCall    ::=    FunctionName '(' ( Argument ( ',' Argument)*)? ')'
   *
   * @return true if, and only if, a FunctionCall was matched
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected boolean FunctionCall() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    if (lookahead(':', 1))
    {
      appendOp(4, OpCodes.OP_EXTFUNCTION);

      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 1, m_queueMark - 1);

      nextToken();
      consumeExpected(':');

      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 2, m_queueMark - 1);

      nextToken();
    }
    else
    {
      int funcTok = getFunctionToken(m_token);

      if (-1 == funcTok)
      {
        error(XPATHErrorResources.ER_COULDNOT_FIND_FUNCTION,
              new Object[]{ m_token });  //"Could not find function: "+m_token+"()");
      }

      switch (funcTok)
      {
      case OpCodes.NODETYPE_PI :
      case OpCodes.NODETYPE_COMMENT :
      case OpCodes.NODETYPE_TEXT :
      case OpCodes.NODETYPE_NODE :
        // Node type tests look like function calls, but they're not
        return false;
      default :
        appendOp(3, OpCodes.OP_FUNCTION);

        m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 1, funcTok);
      }

      nextToken();
    }

    consumeExpected('(');

    while (!tokenIs(')') && m_token != null)
    {
      if (tokenIs(','))
      {
        error(XPATHErrorResources.ER_FOUND_COMMA_BUT_NO_PRECEDING_ARG, null);  //"Found ',' but no preceding argument!");
      }

      Argument();

      if (!tokenIs(')'))
      {
        consumeExpected(',');

        if (tokenIs(')'))
        {
          error(XPATHErrorResources.ER_FOUND_COMMA_BUT_NO_FOLLOWING_ARG,
                null);  //"Found ',' but no following argument!");
        }
      }
    }

    consumeExpected(')');

    // Terminate for safety.
    m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.ENDOP);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH,m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);
    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH, 
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

    return true;
  }

  // ============= GRAMMAR FUNCTIONS =================

  
LocationPath ::= RelativeLocationPath
| AbsoluteLocationPath
Throws:
TransformerException – /**
   *
   * LocationPath ::= RelativeLocationPath
   * | AbsoluteLocationPath
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void LocationPath() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    // int locationPathOpPos = opPos;
    appendOp(2, OpCodes.OP_LOCATIONPATH);

    boolean seenSlash = tokenIs('/');

    if (seenSlash)
    {
      appendOp(4, OpCodes.FROM_ROOT);

      // Tell how long the step is without the predicate
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 2, 4);
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 1, OpCodes.NODETYPE_ROOT);

      nextToken();
    } else if (m_token == null) {
      error(XPATHErrorResources.ER_EXPECTED_LOC_PATH_AT_END_EXPR, null);
    }

    if (m_token != null)
    {
      if (!RelativeLocationPath() && !seenSlash)
      {
        // Neither a '/' nor a RelativeLocationPath - i.e., matched nothing
        // "Location path expected, but found "+m_token+" was encountered."
        error(XPATHErrorResources.ER_EXPECTED_LOC_PATH, 
              new Object [] {m_token});
      }
    }

    // Terminate for safety.
    m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.ENDOP);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH,m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);
    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
  }

  
RelativeLocationPath ::= Step
| RelativeLocationPath '/' Step
| AbbreviatedRelativeLocationPath
Throws:
TransformerException – 
@returns
true if, and only if, a RelativeLocationPath was matched/**
   *
   * RelativeLocationPath ::= Step
   * | RelativeLocationPath '/' Step
   * | AbbreviatedRelativeLocationPath
   *
   * @returns true if, and only if, a RelativeLocationPath was matched
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected boolean RelativeLocationPath()
               throws javax.xml.transform.TransformerException
  {
    if (!Step())
    {
      return false;
    }

    while (tokenIs('/'))
    {
      nextToken();

      if (!Step())
      {
        // RelativeLocationPath can't end with a trailing '/'
        // "Location step expected following '/' or '//'"
        error(XPATHErrorResources.ER_EXPECTED_LOC_STEP, null);
      }
    }

    return true;
  }

  
Step    ::=    Basis Predicate
| AbbreviatedStep
Throws:
TransformerException – 
@returns
false if step was empty (or only a '/'); true, otherwise/**
   *
   * Step    ::=    Basis Predicate
   * | AbbreviatedStep
   *
   * @returns false if step was empty (or only a '/'); true, otherwise
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected boolean Step() throws javax.xml.transform.TransformerException
  {
    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    boolean doubleSlash = tokenIs('/');

    // At most a single '/' before each Step is consumed by caller; if the
    // first thing is a '/', that means we had '//' and the Step must not
    // be empty.
    if (doubleSlash)
    {
      nextToken();

      appendOp(2, OpCodes.FROM_DESCENDANTS_OR_SELF);

      // Have to fix up for patterns such as '//@foo' or '//attribute::foo',
      // which translate to 'descendant-or-self::node()/attribute::foo'.
      // notice I leave the '/' on the queue, so the next will be processed
      // by a regular step pattern.

      // Make room for telling how long the step is without the predicate
      m_ops.setOp(OpMap.MAPINDEX_LENGTH,m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.NODETYPE_NODE);
      m_ops.setOp(OpMap.MAPINDEX_LENGTH,m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

      // Tell how long the step is without the predicate
      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 1,
          m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

      // Tell how long the step is with the predicate
      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
          m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

      opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);
    }

    if (tokenIs("."))
    {
      nextToken();

      if (tokenIs('['))
      {
        error(XPATHErrorResources.ER_PREDICATE_ILLEGAL_SYNTAX, null);  //"'..[predicate]' or '.[predicate]' is illegal syntax.  Use 'self::node()[predicate]' instead.");
      }

      appendOp(4, OpCodes.FROM_SELF);

      // Tell how long the step is without the predicate
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 2,4);
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 1, OpCodes.NODETYPE_NODE);
    }
    else if (tokenIs(".."))
    {
      nextToken();
      appendOp(4, OpCodes.FROM_PARENT);

      // Tell how long the step is without the predicate
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 2,4);
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 1, OpCodes.NODETYPE_NODE);
    }

    // There is probably a better way to test for this 
    // transition... but it gets real hairy if you try 
    // to do it in basis().
    else if (tokenIs('*') || tokenIs('@') || tokenIs('_')
             || (m_token!= null && Character.isLetter(m_token.charAt(0))))
    {
      Basis();

      while (tokenIs('['))
      {
        Predicate();
      }

      // Tell how long the entire step is.
      m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
        m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos); 
    }
    else
    {
      // No Step matched - that's an error if previous thing was a '//'
      if (doubleSlash)
      {
        // "Location step expected following '/' or '//'"
        error(XPATHErrorResources.ER_EXPECTED_LOC_STEP, null);
      }

      return false;
    }

    return true;
  }

  
Basis    ::=    AxisName '::' NodeTest
| AbbreviatedBasis
Throws:
TransformerException – /**
   *
   * Basis    ::=    AxisName '::' NodeTest
   * | AbbreviatedBasis
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void Basis() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);
    int axesType;

    // The next blocks guarantee that a FROM_XXX will be added.
    if (lookahead("::", 1))
    {
      axesType = AxisName();

      nextToken();
      nextToken();
    }
    else if (tokenIs('@'))
    {
      axesType = OpCodes.FROM_ATTRIBUTES;

      appendOp(2, axesType);
      nextToken();
    }
    else
    {
      axesType = OpCodes.FROM_CHILDREN;

      appendOp(2, axesType);
    }

    // Make room for telling how long the step is without the predicate
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

    NodeTest(axesType);

    // Tell how long the step is without the predicate
    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 1,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
   }

  
Basis    ::=    AxisName '::' NodeTest
| AbbreviatedBasis
Throws:
TransformerException – 
Returns:
FROM_XXX axes type, found in Keywords./**
   *
   * Basis    ::=    AxisName '::' NodeTest
   * | AbbreviatedBasis
   *
   * @return FROM_XXX axes type, found in {@link org.apache.xpath.compiler.Keywords}.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected int AxisName() throws javax.xml.transform.TransformerException
  {

    Object val = Keywords.getAxisName(m_token);

    if (null == val)
    {
      error(XPATHErrorResources.ER_ILLEGAL_AXIS_NAME,
            new Object[]{ m_token });  //"illegal axis name: "+m_token);
    }

    int axesType = ((Integer) val).intValue();

    appendOp(2, axesType);

    return axesType;
  }

  
NodeTest    ::=    WildcardName
| NodeType '(' ')'
| 'processing-instruction' '(' Literal ')'
Params:
axesType – FROM_XXX axes type, found in Keywords.
Throws:
TransformerException – /**
   *
   * NodeTest    ::=    WildcardName
   * | NodeType '(' ')'
   * | 'processing-instruction' '(' Literal ')'
   *
   * @param axesType FROM_XXX axes type, found in {@link org.apache.xpath.compiler.Keywords}.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void NodeTest(int axesType) throws javax.xml.transform.TransformerException
  {

    if (lookahead('(', 1))
    {
      Object nodeTestOp = Keywords.getNodeType(m_token);

      if (null == nodeTestOp)
      {
        error(XPATHErrorResources.ER_UNKNOWN_NODETYPE,
              new Object[]{ m_token });  //"Unknown nodetype: "+m_token);
      }
      else
      {
        nextToken();

        int nt = ((Integer) nodeTestOp).intValue();

        m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), nt);
        m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

        consumeExpected('(');

        if (OpCodes.NODETYPE_PI == nt)
        {
          if (!tokenIs(')'))
          {
            Literal();
          }
        }

        consumeExpected(')');
      }
    }
    else
    {

      // Assume name of attribute or element.
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.NODENAME);
      m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

      if (lookahead(':', 1))
      {
        if (tokenIs('*'))
        {
          m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.ELEMWILDCARD);
        }
        else
        {
          m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), m_queueMark - 1);

          // Minimalist check for an NCName - just check first character
          // to distinguish from other possible tokens
          if (!Character.isLetter(m_tokenChar) && !tokenIs('_'))
          {
            // "Node test that matches either NCName:* or QName was expected."
            error(XPATHErrorResources.ER_EXPECTED_NODE_TEST, null);
          }
        }

        nextToken();
        consumeExpected(':');
      }
      else
      {
        m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.EMPTY);
      }

      m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

      if (tokenIs('*'))
      {
        m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.ELEMWILDCARD);
      }
      else
      {
        m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), m_queueMark - 1);

        // Minimalist check for an NCName - just check first character
        // to distinguish from other possible tokens
        if (!Character.isLetter(m_tokenChar) && !tokenIs('_'))
        {
          // "Node test that matches either NCName:* or QName was expected."
          error(XPATHErrorResources.ER_EXPECTED_NODE_TEST, null);
        }
      }

      m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

      nextToken();
    }
  }

  
Predicate ::= '[' PredicateExpr ']'
Throws:
TransformerException – /**
   *
   * Predicate ::= '[' PredicateExpr ']'
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void Predicate() throws javax.xml.transform.TransformerException
  {

    if (tokenIs('['))
    {
      nextToken();
      PredicateExpr();
      consumeExpected(']');
    }
  }

  
PredicateExpr ::= Expr
Throws:
TransformerException – /**
   *
   * PredicateExpr ::= Expr
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void PredicateExpr() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    appendOp(2, OpCodes.OP_PREDICATE);
    Expr();

    // Terminate for safety.
    m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.ENDOP);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);
    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
  }

  
QName ::=  (Prefix ':')? LocalPart
Prefix ::=  NCName
LocalPart ::=  NCName
Throws:
TransformerException – /**
   * QName ::=  (Prefix ':')? LocalPart
   * Prefix ::=  NCName
   * LocalPart ::=  NCName
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void QName() throws javax.xml.transform.TransformerException
  {
    // Namespace
    if(lookahead(':', 1))
    {
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), m_queueMark - 1);
      m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

      nextToken();
      consumeExpected(':');
    }
    else
    {
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.EMPTY);
      m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);
    }
    
    // Local name
    m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), m_queueMark - 1);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

    nextToken();
  }

  
NCName ::=  (Letter | '_') (NCNameChar)
NCNameChar ::=  Letter | Digit | '.' | '-' | '_' | CombiningChar | Extender
/**
   * NCName ::=  (Letter | '_') (NCNameChar)
   * NCNameChar ::=  Letter | Digit | '.' | '-' | '_' | CombiningChar | Extender
   */
  protected void NCName()
  {

    m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), m_queueMark - 1);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

    nextToken();
  }

  
The value of the Literal is the sequence of characters inside
the " or ' characters>.
Literal  ::=  '"' [^"]* '"'
| "'" [^']* "'"
Throws:
TransformerException – /**
   * The value of the Literal is the sequence of characters inside
   * the " or ' characters>.
   *
   * Literal  ::=  '"' [^"]* '"'
   * | "'" [^']* "'"
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void Literal() throws javax.xml.transform.TransformerException
  {

    int last = m_token.length() - 1;
    char c0 = m_tokenChar;
    char cX = m_token.charAt(last);

    if (((c0 == '\"') && (cX == '\"')) || ((c0 == '\'') && (cX == '\'')))
    {

      // Mutate the token to remove the quotes and have the XString object
      // already made.
      int tokenQueuePos = m_queueMark - 1;

      m_ops.m_tokenQueue.setElementAt(null,tokenQueuePos);

      Object obj = new XString(m_token.substring(1, last));

      m_ops.m_tokenQueue.setElementAt(obj,tokenQueuePos);

      // lit = m_token.substring(1, last);
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), tokenQueuePos);
      m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

      nextToken();
    }
    else
    {
      error(XPATHErrorResources.ER_PATTERN_LITERAL_NEEDS_BE_QUOTED,
            new Object[]{ m_token });  //"Pattern literal ("+m_token+") needs to be quoted!");
    }
  }

  
Number ::= [0-9]+('.'[0-9]+)? | '.'[0-9]+
Throws:
TransformerException – /**
   *
   * Number ::= [0-9]+('.'[0-9]+)? | '.'[0-9]+
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void Number() throws javax.xml.transform.TransformerException
  {

    if (null != m_token)
    {

      // Mutate the token to remove the quotes and have the XNumber object
      // already made.
      double num;

      try
      {
      	// XPath 1.0 does not support number in exp notation
      	if ((m_token.indexOf('e') > -1)||(m_token.indexOf('E') > -1))
      		throw new NumberFormatException();
        num = Double.valueOf(m_token).doubleValue();
      }
      catch (NumberFormatException nfe)
      {
        num = 0.0;  // to shut up compiler.

        error(XPATHErrorResources.ER_COULDNOT_BE_FORMATTED_TO_NUMBER,
              new Object[]{ m_token });  //m_token+" could not be formatted to a number!");
      }

      m_ops.m_tokenQueue.setElementAt(new XNumber(num),m_queueMark - 1);
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), m_queueMark - 1);
      m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

      nextToken();
    }
  }

  // ============= PATTERN FUNCTIONS =================

  
Pattern  ::=  LocationPathPattern
| Pattern '|' LocationPathPattern
Throws:
TransformerException – /**
   *
   * Pattern  ::=  LocationPathPattern
   * | Pattern '|' LocationPathPattern
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void Pattern() throws javax.xml.transform.TransformerException
  {

    while (true)
    {
      LocationPathPattern();

      if (tokenIs('|'))
      {
        nextToken();
      }
      else
      {
        break;
      }
    }
  }

  
LocationPathPattern  ::=  '/' RelativePathPattern?
| IdKeyPattern (('/' | '//') RelativePathPattern)?
| '//'? RelativePathPattern
Throws:
TransformerException – /**
   *
   *
   * LocationPathPattern  ::=  '/' RelativePathPattern?
   * | IdKeyPattern (('/' | '//') RelativePathPattern)?
   * | '//'? RelativePathPattern
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void LocationPathPattern() throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);

    final int RELATIVE_PATH_NOT_PERMITTED = 0;
    final int RELATIVE_PATH_PERMITTED     = 1;
    final int RELATIVE_PATH_REQUIRED      = 2;

    int relativePathStatus = RELATIVE_PATH_NOT_PERMITTED;

    appendOp(2, OpCodes.OP_LOCATIONPATHPATTERN);

    if (lookahead('(', 1)
            && (tokenIs(Keywords.FUNC_ID_STRING)
                || tokenIs(Keywords.FUNC_KEY_STRING)))
    {
      IdKeyPattern();

      if (tokenIs('/'))
      {
        nextToken();

        if (tokenIs('/'))
        {
          appendOp(4, OpCodes.MATCH_ANY_ANCESTOR);

          nextToken();
        }
        else
        {
          appendOp(4, OpCodes.MATCH_IMMEDIATE_ANCESTOR);
        }

        // Tell how long the step is without the predicate
        m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 2, 4);
        m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 1, OpCodes.NODETYPE_FUNCTEST);

        relativePathStatus = RELATIVE_PATH_REQUIRED;
      }
    }
    else if (tokenIs('/'))
    {
      if (lookahead('/', 1))
      {
        appendOp(4, OpCodes.MATCH_ANY_ANCESTOR);
        
        // Added this to fix bug reported by Myriam for match="//x/a"
        // patterns.  If you don't do this, the 'x' step will think it's part
        // of a '//' pattern, and so will cause 'a' to be matched when it has
        // any ancestor that is 'x'.
        nextToken();

        relativePathStatus = RELATIVE_PATH_REQUIRED;
      }
      else
      {
        appendOp(4, OpCodes.FROM_ROOT);

        relativePathStatus = RELATIVE_PATH_PERMITTED;
      }


      // Tell how long the step is without the predicate
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 2, 4);
      m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH) - 1, OpCodes.NODETYPE_ROOT);

      nextToken();
    }
    else
    {
      relativePathStatus = RELATIVE_PATH_REQUIRED;
    }

    if (relativePathStatus != RELATIVE_PATH_NOT_PERMITTED)
    {
      if (!tokenIs('|') && (null != m_token))
      {
        RelativePathPattern();
      }
      else if (relativePathStatus == RELATIVE_PATH_REQUIRED)
      {
        // "A relative path pattern was expected."
        error(XPATHErrorResources.ER_EXPECTED_REL_PATH_PATTERN, null);
      }
    }

    // Terminate for safety.
    m_ops.setOp(m_ops.getOp(OpMap.MAPINDEX_LENGTH), OpCodes.ENDOP);
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);
    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);
  }

  
IdKeyPattern  ::=  'id' '(' Literal ')'
| 'key' '(' Literal ',' Literal ')'
(Also handle doc())
Throws:
TransformerException – /**
   *
   * IdKeyPattern  ::=  'id' '(' Literal ')'
   * | 'key' '(' Literal ',' Literal ')'
   * (Also handle doc())
   *
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void IdKeyPattern() throws javax.xml.transform.TransformerException
  {
    FunctionCall();
  }

  
RelativePathPattern  ::=  StepPattern
| RelativePathPattern '/' StepPattern
| RelativePathPattern '//' StepPattern
Throws:
TransformerException – /**
   *
   * RelativePathPattern  ::=  StepPattern
   * | RelativePathPattern '/' StepPattern
   * | RelativePathPattern '//' StepPattern
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected void RelativePathPattern()
              throws javax.xml.transform.TransformerException
  {

    // Caller will have consumed any '/' or '//' preceding the
    // RelativePathPattern, so let StepPattern know it can't begin with a '/'
    boolean trailingSlashConsumed = StepPattern(false);

    while (tokenIs('/'))
    {
      nextToken();

      // StepPattern() may consume first slash of pair in "a//b" while
      // processing StepPattern "a".  On next iteration, let StepPattern know
      // that happened, so it doesn't match ill-formed patterns like "a///b".
      trailingSlashConsumed = StepPattern(!trailingSlashConsumed);
    }
  }

  
StepPattern  ::=  AbbreviatedNodeTestStep
Params:
isLeadingSlashPermitted – a boolean indicating whether a slash can
       appear at the start of this step
Throws:
TransformerException – 
Returns:
boolean indicating whether a slash following the step was consumed/**
   *
   * StepPattern  ::=  AbbreviatedNodeTestStep
   *
   * @param isLeadingSlashPermitted a boolean indicating whether a slash can
   *        appear at the start of this step
   *
   * @return boolean indicating whether a slash following the step was consumed
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected boolean StepPattern(boolean isLeadingSlashPermitted)
            throws javax.xml.transform.TransformerException
  {
    return AbbreviatedNodeTestStep(isLeadingSlashPermitted);
  }

  
AbbreviatedNodeTestStep    ::=    '@'? NodeTest Predicate
Params:
isLeadingSlashPermitted – a boolean indicating whether a slash can
       appear at the start of this step
Throws:
TransformerException – 
Returns:
boolean indicating whether a slash following the step was consumed/**
   *
   * AbbreviatedNodeTestStep    ::=    '@'? NodeTest Predicate
   *
   * @param isLeadingSlashPermitted a boolean indicating whether a slash can
   *        appear at the start of this step
   *
   * @return boolean indicating whether a slash following the step was consumed
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected boolean AbbreviatedNodeTestStep(boolean isLeadingSlashPermitted)
            throws javax.xml.transform.TransformerException
  {

    int opPos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);
    int axesType;

    // The next blocks guarantee that a MATCH_XXX will be added.
    int matchTypePos = -1;

    if (tokenIs('@'))
    {
      axesType = OpCodes.MATCH_ATTRIBUTE;

      appendOp(2, axesType);
      nextToken();
    }
    else if (this.lookahead("::", 1))
    {
      if (tokenIs("attribute"))
      {
        axesType = OpCodes.MATCH_ATTRIBUTE;

        appendOp(2, axesType);
      }
      else if (tokenIs("child"))
      {
        matchTypePos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);
        axesType = OpCodes.MATCH_IMMEDIATE_ANCESTOR;

        appendOp(2, axesType);
      }
      else
      {
        axesType = -1;

        this.error(XPATHErrorResources.ER_AXES_NOT_ALLOWED,
                   new Object[]{ this.m_token });
      }

      nextToken();
      nextToken();
    }
    else if (tokenIs('/'))
    {
      if (!isLeadingSlashPermitted)
      {
        // "A step was expected in the pattern, but '/' was encountered."
        error(XPATHErrorResources.ER_EXPECTED_STEP_PATTERN, null);
      }
      axesType = OpCodes.MATCH_ANY_ANCESTOR;

      appendOp(2, axesType);
      nextToken();
    }
    else
    {
      matchTypePos = m_ops.getOp(OpMap.MAPINDEX_LENGTH);
      axesType = OpCodes.MATCH_IMMEDIATE_ANCESTOR;

      appendOp(2, axesType);
    }

    // Make room for telling how long the step is without the predicate
    m_ops.setOp(OpMap.MAPINDEX_LENGTH, m_ops.getOp(OpMap.MAPINDEX_LENGTH) + 1);

    NodeTest(axesType);

    // Tell how long the step is without the predicate
    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH + 1,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

    while (tokenIs('['))
    {
      Predicate();
    }

    boolean trailingSlashConsumed;

    // For "a//b", where "a" is current step, we need to mark operation of
    // current step as "MATCH_ANY_ANCESTOR".  Then we'll consume the first
    // slash and subsequent step will be treated as a MATCH_IMMEDIATE_ANCESTOR
    // (unless it too is followed by '//'.)
    //
    // %REVIEW%  Following is what happens today, but I'm not sure that's
    // %REVIEW%  correct behaviour.  Perhaps no valid case could be constructed
    // %REVIEW%  where it would matter?
    //
    // If current step is on the attribute axis (e.g., "@x//b"), we won't
    // change the current step, and let following step be marked as
    // MATCH_ANY_ANCESTOR on next call instead.
    if ((matchTypePos > -1) && tokenIs('/') && lookahead('/', 1))
    {
      m_ops.setOp(matchTypePos, OpCodes.MATCH_ANY_ANCESTOR);

      nextToken();

      trailingSlashConsumed = true;
    }
    else
    {
      trailingSlashConsumed = false;
    }

    // Tell how long the entire step is.
    m_ops.setOp(opPos + OpMap.MAPINDEX_LENGTH,
      m_ops.getOp(OpMap.MAPINDEX_LENGTH) - opPos);

    return trailingSlashConsumed;
  }
}