org.apache.poi.poifs.eventfilesystem.POIFSReaderRegistry Maven / Gradle / Ivy


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

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   distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.poi.poifs.eventfilesystem;

import java.util.*;

import org.apache.poi.poifs.filesystem.DocumentDescriptor;
import org.apache.poi.poifs.filesystem.POIFSDocumentPath;

/**
 * A registry for POIFSReaderListeners and the DocumentDescriptors of
 * the documents those listeners are interested in
 *
 * @author Marc Johnson (mjohnson at apache dot org)
 * @version %I%, %G%
 */

class POIFSReaderRegistry
{

    // the POIFSReaderListeners who listen to all POIFSReaderEvents
    private Set omnivorousListeners;

    // Each mapping in this Map has a key consisting of a
    // POIFSReaderListener and a value cosisting of a Set of
    // DocumentDescriptors for the documents that POIFSReaderListener
    // is interested in; used to efficiently manage the registry
    private Map> selectiveListeners;

    // Each mapping in this Map has a key consisting of a
    // DocumentDescriptor and a value consisting of a Set of
    // POIFSReaderListeners for the document matching that
    // DocumentDescriptor; used when a document is found, to quickly
    // get the listeners interested in that document
    private Map> chosenDocumentDescriptors;

    /**
     * Construct the registry
     */

    POIFSReaderRegistry()
    {
        omnivorousListeners       = new HashSet<>();
        selectiveListeners        = new HashMap<>();
        chosenDocumentDescriptors = new HashMap<>();
    }

    /**
     * register a POIFSReaderListener for a particular document
     *
     * @param listener the listener
     * @param path the path of the document of interest
     * @param documentName the name of the document of interest
     */

    void registerListener(final POIFSReaderListener listener,
                          final POIFSDocumentPath path,
                          final String documentName)
    {
        if (!omnivorousListeners.contains(listener))
        {

            // not an omnivorous listener (if it was, this method is a
            // no-op)
            Set descriptors =
                    selectiveListeners.computeIfAbsent(listener, k -> new HashSet<>());

            // this listener has not registered before
            DocumentDescriptor descriptor = new DocumentDescriptor(path, documentName);

            if (descriptors.add(descriptor)) {

                // this listener wasn't already listening for this
                // document -- add the listener to the set of
                // listeners for this document
                Set listeners =
                        chosenDocumentDescriptors.computeIfAbsent(descriptor, k -> new HashSet<>());

                // nobody was listening for this document before
                listeners.add(listener);
            }
        }
    }

    /**
     * register for all documents
     *
     * @param listener the listener who wants to get all documents
     */

    void registerListener(final POIFSReaderListener listener)
    {
        if (!omnivorousListeners.contains(listener))
        {

            // wasn't already listening for everything, so drop
            // anything listener might have been listening for and
            // then add the listener to the set of omnivorous
            // listeners
            removeSelectiveListener(listener);
            omnivorousListeners.add(listener);
        }
    }

    /**
     * get am iterator of listeners for a particular document
     *
     * @param path the document path
     * @param name the name of the document
     *
     * @return an Iterator POIFSReaderListeners; may be empty
     */

    Iterable getListeners(final POIFSDocumentPath path, final String name)
    {
        Set rval = new HashSet<>(omnivorousListeners);
        Set selectiveListenersInner =
            chosenDocumentDescriptors.get(new DocumentDescriptor(path, name));

        if (selectiveListenersInner != null)
        {
            rval.addAll(selectiveListenersInner);
        }
        return rval;
    }

    private void removeSelectiveListener(final POIFSReaderListener listener)
    {
        Set selectedDescriptors = selectiveListeners.remove(listener);

        if (selectedDescriptors != null) {
            for (DocumentDescriptor selectedDescriptor : selectedDescriptors) {
                dropDocument(listener, selectedDescriptor);
            }
        }
    }

    private void dropDocument(final POIFSReaderListener listener,
                              final DocumentDescriptor descriptor)
    {
        Set listeners = chosenDocumentDescriptors.get(descriptor);

        listeners.remove(listener);
        if (listeners.size() == 0)
        {
            chosenDocumentDescriptors.remove(descriptor);
        }
    }
}   // end package scope class POIFSReaderRegistry