namespacesupport2.java

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// Local classes.
// These were _internal_ classes... but in fact they don't have to be,
// and may be more efficient if they aren't. 
////////////////////////////////////////////////////////////////////

/**
 * Implementation of Enumeration filter, wrapped
 * aroung the get-all-prefixes version of the operation. This is NOT
 * necessarily the most efficient approach; finding the URI and then asking
 * what prefixes apply to it might make much more sense.
 */
class PrefixForUriEnumerator implements Enumeration
{
    private Enumeration allPrefixes;
    private String uri;
    private String lookahead=null;
    private NamespaceSupport2 nsup;
     
    // Kluge: Since one can't do a constructor on an
    // anonymous class (as far as I know)...
    PrefixForUriEnumerator(NamespaceSupport2 nsup,String uri, Enumeration allPrefixes)
    {
	this.nsup=nsup;
        this.uri=uri;
        this.allPrefixes=allPrefixes;
    }
        
    public boolean hasMoreElements()
    {
        if(lookahead!=null)
            return true;
            
        while(allPrefixes.hasMoreElements())
            {
                String prefix=(String)allPrefixes.nextElement();
                if(uri.equals(nsup.getURI(prefix)))
                    {
                        lookahead=prefix;
                        return true;
                    }
            }
        return false;
    }
        
    public Object nextElement()
    {
        if(hasMoreElements())
            {
                String tmp=lookahead;
                lookahead=null;
                return tmp;
            }
        else
            throw new java.util.NoSuchElementException();
    }
}

/**
 * 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).</p>
 */
final class Context2 {

    ////////////////////////////////////////////////////////////////
    // Manefest Constants
    ////////////////////////////////////////////////////////////////
        
    /**
     * An empty enumeration.
     */
    private final static Enumeration EMPTY_ENUMERATION =
        new Vector().elements();

    ////////////////////////////////////////////////////////////////
    // Protected state.
    ////////////////////////////////////////////////////////////////
        
    Hashtable prefixTable;
    Hashtable uriTable;
    Hashtable elementNameTable;
    Hashtable attributeNameTable;
    String defaultNS = null;

    ////////////////////////////////////////////////////////////////
    // Internal state.
    ////////////////////////////////////////////////////////////////
        
    private Vector declarations = null;
    private boolean tablesDirty = false;
    private Context2 parent = null;
    private Context2 child = null;

    /**
     * Create a new Namespace context.
     */
    Context2 (Context2 parent)
    {
        if(parent==null)
            {
                prefixTable = new Hashtable();
                uriTable = new Hashtable();
                elementNameTable=null; 
                attributeNameTable=null; 
            }
        else
            setParent(parent);
    }

        
    /**
     * @returns The child Namespace context object, or null if this
     * is the last currently on the chain.
     */
    Context2 getChild()
    {
        return child;
    }
        
    /**
     * @returns The parent Namespace context object, or null if this
     * is the root.
     */
    Context2 getParent()
    {
        return parent;
    }
        
    /**
     * (Re)set the parent of this Namespace context.
     * This is separate from the c'tor because it's re-applied
     * when a Context2 is reused by push-after-pop.
     *
     * @param parent The parent Namespace context object.
     */
    void setParent (Context2 parent)
    {
        this.parent = parent;
        parent.child = this;        // JJK: Doubly-linked
        declarations = null;
        prefixTable = parent.prefixTable;
        uriTable = parent.uriTable;
        elementNameTable = parent.elementNameTable;
        attributeNameTable = parent.attributeNameTable;
        defaultNS = parent.defaultNS;
        tablesDirty = false;
    }
        
        
    /**
     * Declare a Namespace prefix for this context.
     *
     * @param prefix The prefix to declare.
     * @param uri The associated Namespace URI.
     * @see org.xml.sax.helpers.NamespaceSupport2#declarePrefix
     */
    void declarePrefix (String prefix, String uri)
    {
                                // Lazy processing...
        if (!tablesDirty) {
            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 a raw XML 1.0 name in this context.
     *
     * @param qName The raw XML 1.0 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.NamespaceSupport2#processName
     */
    String [] processName (String qName, boolean isAttribute)
    {
        String name[];
        Hashtable table;
            
                                // Select the appropriate table.
        if (isAttribute) {
            if(elementNameTable==null)
                elementNameTable=new Hashtable();
            table = elementNameTable;
        } else {
            if(attributeNameTable==null)
                attributeNameTable=new Hashtable();
            table = attributeNameTable;
        }
            
                                // 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.
        name = new String[3];
        int index = qName.indexOf(':');
            
            
                                // No prefix.
        if (index == -1) {
            if (isAttribute || defaultNS == null) {
                name[0] = "";
            } else {
                name[0] = defaultNS;
            }
            name[1] = qName.intern();
            name[2] = name[1];
        }
            
                                // 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) {
                return null;
            }
            name[0] = uri;
            name[1] = local.intern();
            name[2] = qName.intern();
        }
            
                                // Save in the cache for future use.
        table.put(name[2], name);
        tablesDirty = true;
        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.NamespaceSupport2#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.NamespaceSupport2#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.NamespaceSupport2#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.NamespaceSupport2#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. In that case,
     * the Context2 will share data structures with its parent.
     * New tables are obtained only when new declarations are issued,
     * so they can be popped off the stack.</p>
     *
     * <p> JJK: **** Alternative: each Context2 might declare
     *  _only_ its local bindings, and delegate upward if not found.</p>
     */     
    private void copyTables ()
    {
        // Start by copying our parent's bindings
        prefixTable = (Hashtable)prefixTable.clone();
        uriTable = (Hashtable)uriTable.clone();

        // Replace the caches with empty ones, rather than
        // trying to determine which bindings should be flushed.
        // As far as I can tell, these caches are never actually
        // used in Xalan... More efficient to remove the whole
        // cache system? ****
        if(elementNameTable!=null)
            elementNameTable=new Hashtable(); 
        if(attributeNameTable!=null)
            attributeNameTable=new Hashtable(); 
        tablesDirty = true;
    }

}


// end of NamespaceSupport2.java