/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/*

 * Copyright 2003-2004 The Apache Software Foundation.

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

/*

 * $Id: AttributesImplSerializer.java,v 1.2.4.1 2005/09/15 08:15:14 suresh_emailid Exp $

 */

package com.sun.org.apache.xml.internal.serializer;

import java.util.Hashtable;

import org.xml.sax.Attributes;

import org.xml.sax.helpers.AttributesImpl;

/**

 * This class extends org.xml.sax.helpers.AttributesImpl which implements org.

 * xml.sax.Attributes. But for optimization this class adds a Hashtable for

 * faster lookup of an index by qName, which is commonly done in the stream

 * serializer.

 *

 * @see org.xml.sax.Attributes

 *

 * @xsl.usage internal

 */

public final class AttributesImplSerializer extends AttributesImpl

{

    /**

     * Hash table of qName/index values to quickly lookup the index

     * of an attributes qName.  qNames are in uppercase in the hash table

     * to make the search case insensitive.

     *

     * The keys to the hashtable to find the index are either

     * "prefix:localName"  or "{uri}localName".

     */

    private final Hashtable m_indexFromQName = new Hashtable();

    private final StringBuffer m_buff = new StringBuffer();

    /**

     * This is the number of attributes before switching to the hash table,

     * and can be tuned, but 12 seems good for now - Brian M.

     */

    private static final int MAX = 12;

    /**

     * One less than the number of attributes before switching to

     * the Hashtable.

     */

    private static final int MAXMinus1 = MAX - 1;

    /**

     * This method gets the index of an attribute given its qName.

     * @param qname the qualified name of the attribute, e.g. "prefix1:locName1"

     * @return the integer index of the attribute.

     * @see org.xml.sax.Attributes#getIndex(String)

     */

    public final int getIndex(String qname)

    {

        int index;

        if (super.getLength() < MAX)

        {

            // if we haven't got too many attributes let the

            // super class look it up

            index = super.getIndex(qname);

            return index;

        }

        // we have too many attributes and the super class is slow

        // so find it quickly using our Hashtable.

        Integer i = (Integer)m_indexFromQName.get(qname);

        if (i == null)

            index = -1;

        else

            index = i.intValue();

        return index;

    }

    /**

     * This method adds the attribute, but also records its qName/index pair in

     * the hashtable for fast lookup by getIndex(qName).

     * @param uri the URI of the attribute

     * @param local the local name of the attribute

     * @param qname the qualified name of the attribute

     * @param type the type of the attribute

     * @param val the value of the attribute

     *

     * @see org.xml.sax.helpers.AttributesImpl#addAttribute(String, String, String, String, String)

     * @see #getIndex(String)

     */

    public final void addAttribute(

        String uri,

        String local,

        String qname,

        String type,

        String val)

    {

        int index = super.getLength();

        super.addAttribute(uri, local, qname, type, val);

        // (index + 1) is now the number of attributes

        // so either compare (index+1) to MAX, or compare index to (MAX-1)

        if (index < MAXMinus1)

        {

            return;

        }

        else if (index == MAXMinus1)

        {

            switchOverToHash(MAX);

        }

        else

        {

            /* add the key with the format of "prefix:localName" */

            /* we have just added the attibute, its index is the old length */

            Integer i = new Integer(index);

            m_indexFromQName.put(qname, i);

            /* now add with key of the format "{uri}localName" */

            m_buff.setLength(0);

            m_buff.append('{').append(uri).append('}').append(local);

            String key = m_buff.toString();

            m_indexFromQName.put(key, i);

        }

        return;

    }

    /**

     * We are switching over to having a hash table for quick look

     * up of attributes, but up until now we haven't kept any

     * information in the Hashtable, so we now update the Hashtable.

     * Future additional attributes will update the Hashtable as

     * they are added.

     * @param numAtts

     */

    private void switchOverToHash(int numAtts)

    {

        for (int index = 0; index < numAtts; index++)

        {

            String qName = super.getQName(index);

            Integer i = new Integer(index);

            m_indexFromQName.put(qName, i);

            // Add quick look-up to find with uri/local name pair

            String uri = super.getURI(index);

            String local = super.getLocalName(index);

            m_buff.setLength(0);

            m_buff.append('{').append(uri).append('}').append(local);

            String key = m_buff.toString();

            m_indexFromQName.put(key, i);

        }

    }

    /**

     * This method clears the accumulated attributes.

     *

     * @see org.xml.sax.helpers.AttributesImpl#clear()

     */

    public final void clear()

    {

        int len = super.getLength();

        super.clear();

        if (MAX <= len)

        {

            // if we have had enough attributes and are

            // using the Hashtable, then clear the Hashtable too.

            m_indexFromQName.clear();

        }

    }

    /**

     * This method sets the attributes, previous attributes are cleared,

     * it also keeps the hashtable up to date for quick lookup via

     * getIndex(qName).

     * @param atts the attributes to copy into these attributes.

     * @see org.xml.sax.helpers.AttributesImpl#setAttributes(Attributes)

     * @see #getIndex(String)

     */

    public final void setAttributes(Attributes atts)

    {

        super.setAttributes(atts);

        // we've let the super class add the attributes, but

        // we need to keep the hash table up to date ourselves for the

        // potentially new qName/index pairs for quick lookup.

        int numAtts = atts.getLength();

        if (MAX <= numAtts)

            switchOverToHash(numAtts);

    }

    /**

     * This method gets the index of an attribute given its uri and locanName.

     * @param uri the URI of the attribute name.

     * @param localName the local namer (after the ':' ) of the attribute name.

     * @return the integer index of the attribute.

     * @see org.xml.sax.Attributes#getIndex(String)

     */

    public final int getIndex(String uri, String localName)

    {

        int index;

        if (super.getLength() < MAX)

        {

            // if we haven't got too many attributes let the

            // super class look it up

            index = super.getIndex(uri,localName);

            return index;

        }

        // we have too many attributes and the super class is slow

        // so find it quickly using our Hashtable.

        // Form the key of format "{uri}localName"

        m_buff.setLength(0);

        m_buff.append('{').append(uri).append('}').append(localName);

        String key = m_buff.toString();

        Integer i = (Integer)m_indexFromQName.get(key);

        if (i == null)

            index = -1;

        else

            index = i.intValue();

        return index;

    }

}