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   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
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   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
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   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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   * accompanied this code).
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   *
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  // NamespaceSupport.java - generic Namespace support for SAX.
  // http://www.saxproject.org
  // Written by David Megginson
  // This class is in the Public Domain.  NO WARRANTY!
  // $Id: NamespaceSupport.java,v 1.5 2004/11/03 22:53:09 jsuttor Exp $
  
  package org.xml.sax.helpers;
  
  import java.util.EmptyStackException;
  import java.util.Enumeration;
  import java.util.Hashtable;
  import java.util.Vector;
  
  
  /**
   * Encapsulate Namespace logic for use by applications using SAX,
   * or internally by SAX drivers.
   *
   * <blockquote>
   * <em>This module, both source code and documentation, is in the
   * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
   * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
   * for further information.
   * </blockquote>
   *
   * <p>This class encapsulates the logic of Namespace processing: it
   * tracks the declarations currently in force for each context and
   * automatically processes qualified XML names into their Namespace
   * parts; it can also be used in reverse for generating XML qnames
   * from Namespaces.</p>
   *
   * <p>Namespace support objects are reusable, but the reset method
   * must be invoked between each session.</p>
   *
   * <p>Here is a simple session:</p>
   *
   * <pre>
   * String parts[] = new String[3];
   * NamespaceSupport support = new NamespaceSupport();
   *
   * support.pushContext();
   * support.declarePrefix("", "http://www.w3.org/1999/xhtml");
   * support.declarePrefix("dc", "http://www.purl.org/dc#");
   *
   * parts = support.processName("p", parts, false);
   * System.out.println("Namespace URI: " + parts[0]);
   * System.out.println("Local name: " + parts[1]);
   * System.out.println("Raw name: " + parts[2]);
   *
   * parts = support.processName("dc:title", parts, false);
   * System.out.println("Namespace URI: " + parts[0]);
   * System.out.println("Local name: " + parts[1]);
   * System.out.println("Raw name: " + parts[2]);
   *
   * support.popContext();
   * </pre>
   *
   * <p>Note that this class is optimized for the use case where most
   * elements do not contain Namespace declarations: if the same
   * prefix/URI mapping is repeated for each context (for example), this
   * class will be somewhat less efficient.</p>
   *
   * <p>Although SAX drivers (parsers) may choose to use this class to
   * implement namespace handling, they are not required to do so.
   * Applications must track namespace information themselves if they
   * want to use namespace information.
   *
   * @since SAX 2.0
   * @author David Megginson
   */
  public class NamespaceSupport
  {
  
  
      ////////////////////////////////////////////////////////////////////
      // Constants.
      ////////////////////////////////////////////////////////////////////
  
  
      /**
       * The XML Namespace URI as a constant.
       * The value is <code>http://www.w3.org/XML/1998/namespace</code>
       * as defined in the "Namespaces in XML" * recommendation.
       *
       * <p>This is the Namespace URI that is automatically mapped
       * to the "xml" prefix.</p>
       */
      public final static String XMLNS =
          "http://www.w3.org/XML/1998/namespace";
  
  
      /**
       * The namespace declaration URI as a constant.
       * The value is <code>http://www.w3.org/xmlns/2000/</code>, as defined
       * in a backwards-incompatible erratum to the "Namespaces in XML"
       * recommendation.  Because that erratum postdated SAX2, SAX2 defaults
       * to the original recommendation, and does not normally use this URI.
       *
       *
       * <p>This is the Namespace URI that is optionally applied to
       * <em>xmlns</em> and <em>xmlns:*</em> attributes, which are used to
       * declare namespaces.  </p>
       *
       * @since SAX 2.1alpha
       * @see #setNamespaceDeclUris
       * @see #isNamespaceDeclUris
       */
      public final static String NSDECL =
          "http://www.w3.org/xmlns/2000/";
  
  
      /**
       * An empty enumeration.
       */
      private final static Enumeration EMPTY_ENUMERATION =
          new Vector().elements();
  
  
      ////////////////////////////////////////////////////////////////////
      // Constructor.
      ////////////////////////////////////////////////////////////////////
  
  
      /**
       * Create a new Namespace support object.
       */
      public NamespaceSupport ()
      {
          reset();
      }
  
  
  
      ////////////////////////////////////////////////////////////////////
      // Context management.
      ////////////////////////////////////////////////////////////////////
  
  
      /**
       * Reset this Namespace support object for reuse.
       *
       * <p>It is necessary to invoke this method before reusing the
       * Namespace support object for a new session.  If namespace
       * declaration URIs are to be supported, that flag must also
       * be set to a non-default value.
       * </p>
       *
       * @see #setNamespaceDeclUris
       */
      public void reset ()
      {
          contexts = new Context[32];
          namespaceDeclUris = false;
          contextPos = 0;
          contexts[contextPos] = currentContext = new Context();
          currentContext.declarePrefix("xml", XMLNS);
      }
  
  
      /**
       * Start a new Namespace context.
       * The new context will automatically inherit
       * the declarations of its parent context, but it will also keep
       * track of which declarations were made within this context.
       *
       * <p>Event callback code should start a new context once per element.
       * This means being ready to call this in either of two places.
       * For elements that don't include namespace declarations, the
       * <em>ContentHandler.startElement()</em> callback is the right place.
       * For elements with such a declaration, it'd done in the first
       * <em>ContentHandler.startPrefixMapping()</em> callback.
       * A boolean flag can be used to
       * track whether a context has been started yet.  When either of
       * those methods is called, it checks the flag to see if a new context
       * needs to be started.  If so, it starts the context and sets the
       * flag.  After <em>ContentHandler.startElement()</em>
       * does that, it always clears the flag.
       *
       * <p>Normally, SAX drivers would push a new context at the beginning
       * of each XML element.  Then they perform a first pass over the
       * attributes to process all namespace declarations, making
       * <em>ContentHandler.startPrefixMapping()</em> callbacks.
       * Then a second pass is made, to determine the namespace-qualified
       * names for all attributes and for the element name.
       * Finally all the information for the
       * <em>ContentHandler.startElement()</em> callback is available,
       * so it can then be made.
       *
       * <p>The Namespace support object always starts with a base context
       * already in force: in this context, only the "xml" prefix is
       * declared.</p>
       *
       * @see org.xml.sax.ContentHandler
       * @see #popContext
       */
      public void pushContext ()
      {
          int max = contexts.length;
  
          contextPos++;
  
                                  // Extend the array if necessary
          if (contextPos >= max) {
              Context newContexts[] = new Context[max*2];
              System.arraycopy(contexts, 0, newContexts, 0, max);
              max *= 2;
              contexts = newContexts;
          }
  
                                  // Allocate the context if necessary.
          currentContext = contexts[contextPos];
          if (currentContext == null) {
              contexts[contextPos] = currentContext = new Context();
          }
  
                                  // Set the parent, if any.
          if (contextPos > 0) {
              currentContext.setParent(contexts[contextPos - 1]);
          }
      }
  
  
      /**
       * Revert to the previous Namespace context.
       *
       * <p>Normally, you should pop the context at the end of each
       * XML element.  After popping the context, all Namespace prefix
       * mappings that were previously in force are restored.</p>
       *
       * <p>You must not attempt to declare additional Namespace
       * prefixes after popping a context, unless you push another
       * context first.</p>
       *
       * @see #pushContext
       */
      public void popContext ()
      {
          contexts[contextPos].clear();
          contextPos--;
          if (contextPos < 0) {
              throw new EmptyStackException();
          }
          currentContext = contexts[contextPos];
      }
  
  
  
      ////////////////////////////////////////////////////////////////////
      // Operations within a context.
      ////////////////////////////////////////////////////////////////////
  
  
      /**
       * Declare a Namespace prefix.  All prefixes must be declared
       * before they are referenced.  For example, a SAX driver (parser)
       * would scan an element's attributes
       * in two passes:  first for namespace declarations,
       * then a second pass using {@link #processName processName()} to
       * interpret prefixes against (potentially redefined) prefixes.
       *
       * <p>This method declares a prefix in the current Namespace
       * context; the prefix will remain in force until this context
       * is popped, unless it is shadowed in a descendant context.</p>
       *
       * <p>To declare the default element Namespace, use the empty string as
       * the prefix.</p>
       *
       * <p>Note that there is an asymmetry in this library: {@link
       * #getPrefix getPrefix} will not return the "" prefix,
       * even if you have declared a default element namespace.
       * To check for a default namespace,
       * you have to look it up explicitly using {@link #getURI getURI}.
       * This asymmetry exists to make it easier to look up prefixes
       * for attribute names, where the default prefix is not allowed.</p>
       *
       * @param prefix The prefix to declare, or the empty string to
       *  indicate the default element namespace.  This may never have
       *  the value "xml" or "xmlns".
       * @param uri The Namespace URI to associate with the prefix.
       * @return true if the prefix was legal, false otherwise
       *
       * @see #processName
       * @see #getURI
       * @see #getPrefix
       */
      public boolean declarePrefix (String prefix, String uri)
      {
          if (prefix.equals("xml") || prefix.equals("xmlns")) {
              return false;
          } else {
              currentContext.declarePrefix(prefix, uri);
              return true;
          }
      }
  
  
      /**
       * Process a raw XML qualified name, after all declarations in the
       * current context have been handled by {@link #declarePrefix
       * declarePrefix()}.
       *
       * <p>This method processes a raw XML qualified name in the
       * current context by removing the prefix and looking it up among
       * the prefixes currently declared.  The return value will be the
       * array supplied by the caller, filled in as follows:</p>
       *
       * <dl>
       * <dt>parts[0]</dt>
       * <dd>The Namespace URI, or an empty string if none is
       *  in use.</dd>
       * <dt>parts[1]</dt>
       * <dd>The local name (without prefix).</dd>
       * <dt>parts[2]</dt>
       * <dd>The original raw name.</dd>
       * </dl>
       *
       * <p>All of the strings in the array will be internalized.  If
       * the raw name has a prefix that has not been declared, then
       * the return value will be null.</p>
       *
       * <p>Note that attribute names are processed differently than
       * element names: an unprefixed element name will receive the
       * default Namespace (if any), while an unprefixed attribute name
       * will not.</p>
       *
       * @param qName The XML qualified name to be processed.
       * @param parts An array supplied by the caller, capable of
       *        holding at least three members.
       * @param isAttribute A flag indicating whether this is an
       *        attribute name (true) or an element name (false).
       * @return The supplied array holding three internalized strings
       *        representing the Namespace URI (or empty string), the
       *        local name, and the XML qualified name; or null if there
       *        is an undeclared prefix.
       * @see #declarePrefix
       * @see java.lang.String#intern */
      public String [] processName (String qName, String parts[],
                                    boolean isAttribute)
      {
          String myParts[] = currentContext.processName(qName, isAttribute);
          if (myParts == null) {
              return null;
          } else {
              parts[0] = myParts[0];
              parts[1] = myParts[1];
              parts[2] = myParts[2];
              return parts;
          }
      }
  
  
      /**
       * Look up a prefix and get the currently-mapped Namespace URI.
       *
       * <p>This method looks up the prefix in the current context.
       * Use the empty string ("") for the default Namespace.</p>
       *
       * @param prefix The prefix to look up.
       * @return The associated Namespace URI, or null if the prefix
       *         is undeclared in this context.
       * @see #getPrefix
       * @see #getPrefixes
       */
      public String getURI (String prefix)
      {
          return currentContext.getURI(prefix);
      }
  
  
      /**
       * Return an enumeration of all prefixes whose declarations are
       * active in the current context.
       * This includes declarations from parent contexts that have
       * not been overridden.
       *
       * <p><strong>Note:</strong> if there is a default prefix, it will not be
       * returned in this enumeration; check for the default prefix
       * using the {@link #getURI getURI} with an argument of "".</p>
       *
       * @return An enumeration of prefixes (never empty).
       * @see #getDeclaredPrefixes
       * @see #getURI
       */
      public Enumeration getPrefixes ()
      {
          return currentContext.getPrefixes();
      }
  
  
      /**
       * Return one of the prefixes mapped to a Namespace URI.
       *
       * <p>If more than one prefix is currently mapped to the same
       * URI, this method will make an arbitrary selection; if you
       * want all of the prefixes, use the {@link #getPrefixes}
       * method instead.</p>
       *
       * <p><strong>Note:</strong> this will never return the empty (default) prefix;
       * to check for a default prefix, use the {@link #getURI getURI}
       * method with an argument of "".</p>
       *
       * @param uri the namespace URI
       * @return one of the prefixes currently mapped to the URI supplied,
       *         or null if none is mapped or if the URI is assigned to
       *         the default namespace
       * @see #getPrefixes(java.lang.String)
       * @see #getURI
       */
      public String getPrefix (String uri)
      {
          return currentContext.getPrefix(uri);
      }
  
  
      /**
       * Return an enumeration of all prefixes for a given URI whose
       * declarations are active in the current context.
       * This includes declarations from parent contexts that have
       * not been overridden.
       *
       * <p>This method returns prefixes mapped to a specific Namespace
       * URI.  The xml: prefix will be included.  If you want only one
       * prefix that's mapped to the Namespace URI, and you don't care
       * which one you get, use the {@link #getPrefix getPrefix}
       *  method instead.</p>
       *
       * <p><strong>Note:</strong> the empty (default) prefix is <em>never</em> included
       * in this enumeration; to check for the presence of a default
       * Namespace, use the {@link #getURI getURI} method with an
       * argument of "".</p>
       *
       * @param uri The Namespace URI.
       * @return An enumeration of prefixes (never empty).
       * @see #getPrefix
       * @see #getDeclaredPrefixes
       * @see #getURI
       */
      public Enumeration getPrefixes (String uri)
      {
          Vector prefixes = new Vector();
          Enumeration allPrefixes = getPrefixes();
          while (allPrefixes.hasMoreElements()) {
              String prefix = (String)allPrefixes.nextElement();
              if (uri.equals(getURI(prefix))) {
                  prefixes.addElement(prefix);
              }
          }
          return prefixes.elements();
      }
  
  
      /**
       * Return an enumeration of all prefixes declared in this context.
       *
       * <p>The empty (default) prefix will be included in this
       * enumeration; note that this behaviour differs from that of
       * {@link #getPrefix} and {@link #getPrefixes}.</p>
       *
       * @return An enumeration of all prefixes declared in this
       *         context.
       * @see #getPrefixes
       * @see #getURI
       */
      public Enumeration getDeclaredPrefixes ()
      {
          return currentContext.getDeclaredPrefixes();
      }
  
      /**
       * Controls whether namespace declaration attributes are placed
       * into the {@link #NSDECL NSDECL} namespace
       * by {@link #processName processName()}.  This may only be
       * changed before any contexts have been pushed.
       *
       * @since SAX 2.1alpha
       *
       * @exception IllegalStateException when attempting to set this
       *  after any context has been pushed.
       */
      public void setNamespaceDeclUris (boolean value)
      {
          if (contextPos != 0)
              throw new IllegalStateException ();
          if (value == namespaceDeclUris)
              return;
          namespaceDeclUris = value;
          if (value)
              currentContext.declarePrefix ("xmlns", NSDECL);
          else {
              contexts[contextPos] = currentContext = new Context();
              currentContext.declarePrefix("xml", XMLNS);
          }
      }
  
      /**
       * Returns true if namespace declaration attributes are placed into
       * a namespace.  This behavior is not the default.
       *
       * @since SAX 2.1alpha
       */
      public boolean isNamespaceDeclUris ()
          { return namespaceDeclUris; }
  
  
  
      ////////////////////////////////////////////////////////////////////
      // Internal state.
      ////////////////////////////////////////////////////////////////////
  
      private Context contexts[];
      private Context currentContext;
      private int contextPos;
      private boolean namespaceDeclUris;
  
  
      ////////////////////////////////////////////////////////////////////
      // Internal classes.
      ////////////////////////////////////////////////////////////////////
  
      /**
       * Internal class for a single Namespace context.
       *
       * <p>This module caches and reuses Namespace contexts,
       * so the number allocated
       * will be equal to the element depth of the document, not to the total
       * number of elements (i.e. 5-10 rather than tens of thousands).
       * Also, data structures used to represent contexts are shared when
       * possible (child contexts without declarations) to further reduce
       * the amount of memory that's consumed.
       * </p>
       */
      final class Context {
  
          /**
           * Create the root-level Namespace context.
           */
          Context ()
          {
              copyTables();
          }
  
  
          /**
           * (Re)set the parent of this Namespace context.
           * The context must either have been freshly constructed,
           * or must have been cleared.
           *
           * @param context The parent Namespace context object.
           */
          void setParent (Context parent)
          {
              this.parent = parent;
              declarations = null;
              prefixTable = parent.prefixTable;
              uriTable = parent.uriTable;
              elementNameTable = parent.elementNameTable;
              attributeNameTable = parent.attributeNameTable;
              defaultNS = parent.defaultNS;
              declSeen = false;
          }
  
          /**
           * Makes associated state become collectible,
           * invalidating this context.
           * {@link #setParent} must be called before
           * this context may be used again.
           */
          void clear ()
          {
              parent = null;
              prefixTable = null;
              uriTable = null;
              elementNameTable = null;
              attributeNameTable = null;
              defaultNS = null;
          }
  
  
          /**
           * Declare a Namespace prefix for this context.
           *
           * @param prefix The prefix to declare.
           * @param uri The associated Namespace URI.
           * @see org.xml.sax.helpers.NamespaceSupport#declarePrefix
           */
          void declarePrefix (String prefix, String uri)
          {
                                  // Lazy processing...
  //          if (!declsOK)
  //              throw new IllegalStateException (
  //                  "can't declare any more prefixes in this context");
              if (!declSeen) {
                  copyTables();
              }
              if (declarations == null) {
                  declarations = new Vector();
              }
  
              prefix = prefix.intern();
              uri = uri.intern();
              if ("".equals(prefix)) {
                  if ("".equals(uri)) {
                      defaultNS = null;
                  } else {
                      defaultNS = uri;
                  }
              } else {
                  prefixTable.put(prefix, uri);
                  uriTable.put(uri, prefix); // may wipe out another prefix
              }
              declarations.addElement(prefix);
          }
  
  
          /**
           * Process an XML qualified name in this context.
           *
           * @param qName The XML qualified name.
           * @param isAttribute true if this is an attribute name.
           * @return An array of three strings containing the
           *         URI part (or empty string), the local part,
           *         and the raw name, all internalized, or null
           *         if there is an undeclared prefix.
           * @see org.xml.sax.helpers.NamespaceSupport#processName
           */
          String [] processName (String qName, boolean isAttribute)
          {
              String name[];
              Hashtable table;
  
                                  // Select the appropriate table.
              if (isAttribute) {
                  table = attributeNameTable;
              } else {
                  table = elementNameTable;
              }
  
                                  // Start by looking in the cache, and
                                  // return immediately if the name
                                  // is already known in this content
              name = (String[])table.get(qName);
              if (name != null) {
                  return name;
              }
  
                                  // We haven't seen this name in this
                                  // context before.  Maybe in the parent
                                  // context, but we can't assume prefix
                                  // bindings are the same.
              name = new String[3];
              name[2] = qName.intern();
              int index = qName.indexOf(':');
  
  
                                  // No prefix.
              if (index == -1) {
                  if (isAttribute) {
                      if (qName == "xmlns" && namespaceDeclUris)
                          name[0] = NSDECL;
                      else
                          name[0] = "";
                  } else if (defaultNS == null) {
                      name[0] = "";
                  } else {
                      name[0] = defaultNS;
                  }
                  name[1] = name[2];
              }
  
                                  // Prefix
              else {
                  String prefix = qName.substring(0, index);
                  String local = qName.substring(index+1);
                  String uri;
                  if ("".equals(prefix)) {
                      uri = defaultNS;
                  } else {
                      uri = (String)prefixTable.get(prefix);
                  }
                  if (uri == null
                          || (!isAttribute && "xmlns".equals (prefix))) {
                      return null;
                  }
                  name[0] = uri;
                  name[1] = local.intern();
              }
  
                                  // Save in the cache for future use.
                                  // (Could be shared with parent context...)
              table.put(name[2], name);
              return name;
          }
  
  
          /**
           * Look up the URI associated with a prefix in this context.
           *
           * @param prefix The prefix to look up.
           * @return The associated Namespace URI, or null if none is
           *         declared.
           * @see org.xml.sax.helpers.NamespaceSupport#getURI
           */
          String getURI (String prefix)
          {
              if ("".equals(prefix)) {
                  return defaultNS;
              } else if (prefixTable == null) {
                  return null;
              } else {
                  return (String)prefixTable.get(prefix);
              }
          }
  
  
          /**
           * Look up one of the prefixes associated with a URI in this context.
           *
           * <p>Since many prefixes may be mapped to the same URI,
           * the return value may be unreliable.</p>
           *
           * @param uri The URI to look up.
           * @return The associated prefix, or null if none is declared.
           * @see org.xml.sax.helpers.NamespaceSupport#getPrefix
           */
          String getPrefix (String uri)
          {
              if (uriTable == null) {
                  return null;
              } else {
                  return (String)uriTable.get(uri);
              }
          }
  
  
          /**
           * Return an enumeration of prefixes declared in this context.
           *
           * @return An enumeration of prefixes (possibly empty).
           * @see org.xml.sax.helpers.NamespaceSupport#getDeclaredPrefixes
           */
          Enumeration getDeclaredPrefixes ()
          {
              if (declarations == null) {
                  return EMPTY_ENUMERATION;
              } else {
                  return declarations.elements();
              }
          }
  
  
          /**
           * Return an enumeration of all prefixes currently in force.
           *
           * <p>The default prefix, if in force, is <em>not</em>
           * returned, and will have to be checked for separately.</p>
           *
           * @return An enumeration of prefixes (never empty).
           * @see org.xml.sax.helpers.NamespaceSupport#getPrefixes
           */
          Enumeration getPrefixes ()
          {
              if (prefixTable == null) {
                  return EMPTY_ENUMERATION;
              } else {
                  return prefixTable.keys();
              }
          }
  
  
  
          ////////////////////////////////////////////////////////////////
          // Internal methods.
          ////////////////////////////////////////////////////////////////
  
  
          /**
           * Copy on write for the internal tables in this context.
           *
           * <p>This class is optimized for the normal case where most
           * elements do not contain Namespace declarations.</p>
           */
          private void copyTables ()
          {
              if (prefixTable != null) {
                  prefixTable = (Hashtable)prefixTable.clone();
              } else {
                  prefixTable = new Hashtable();
              }
              if (uriTable != null) {
                  uriTable = (Hashtable)uriTable.clone();
              } else {
                  uriTable = new Hashtable();
              }
              elementNameTable = new Hashtable();
              attributeNameTable = new Hashtable();
              declSeen = true;
          }
  
  
  
          ////////////////////////////////////////////////////////////////
          // Protected state.
          ////////////////////////////////////////////////////////////////
  
          Hashtable prefixTable;
          Hashtable uriTable;
          Hashtable elementNameTable;
          Hashtable attributeNameTable;
          String defaultNS = null;
  
  
  
          ////////////////////////////////////////////////////////////////
          // Internal state.
          ////////////////////////////////////////////////////////////////
  
          private Vector declarations = null;
          private boolean declSeen = false;
          private Context parent = null;
      }
  }
  
  // end of NamespaceSupport.java
  