net.pterodactylus.sonitus.io.OggVorbisIdentifier.java Source code

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Here is the source code for net.pterodactylus.sonitus.io.OggVorbisIdentifier.java

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/*
 * Sonitus - OggVorbisIdentifier.java - Copyright  2013 David Roden
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.pterodactylus.sonitus.io;

import java.io.IOException;
import java.io.InputStream;

import net.pterodactylus.sonitus.data.ContentMetadata;
import net.pterodactylus.sonitus.data.FormatMetadata;
import net.pterodactylus.sonitus.data.Metadata;

import com.google.common.base.Optional;
import com.jcraft.jogg.Packet;
import com.jcraft.jogg.Page;
import com.jcraft.jogg.StreamState;
import com.jcraft.jogg.SyncState;
import com.jcraft.jorbis.Comment;
import com.jcraft.jorbis.Info;

/**
 * Identifies Ogg Vorbis files. <p> All knowledge used in this class has been
 * taken from <a href="http://www.jcraft.com/jorbis/tutorial/Tutorial.html">jcraft.com/jorbis/tutorial/Tutorial.html</a>.
 * </p>
 *
 * @author <a href="mailto:bombe@pterodactylus.net">David Bombe Roden</a>
 */
public class OggVorbisIdentifier {

    /** The default size of the read buffer. */
    private static final int BUFFER_SIZE = 4096;

    /** Suppress default constructor. */
    private OggVorbisIdentifier() {
        /* nothing here. */
    }

    /**
     * Tries to parse the given stream as Ogg Vorbis file and returns a {@link
     * Metadata} describing the stream.
     *
     * @param inputStream
     *       The input stream to identify as Ogg Vorbis
     * @return The identified metadata, or {@link Optional#absent()} if the stream
     *         could not be identified
     * @throws IOException
     *       if an I/O error occurs
     */
    public static Optional<Metadata> identify(InputStream inputStream) throws IOException {

        /* stuff needed to decode Ogg. */
        Packet packet = new Packet();
        Page page = new Page();
        StreamState streamState = new StreamState();
        SyncState syncState = new SyncState();

        /* stuff needed to decode Vorbis. */
        Comment comment = new Comment();
        Info info = new Info();

        /* initialize jorbis. */
        syncState.init();
        int bufferSize = BUFFER_SIZE;
        int index = syncState.buffer(bufferSize);
        byte[] buffer = syncState.data;

        boolean streamStateInitialized = false;
        int packetsRead = 0;

        /* read until we have read the three packets required to decode the header. */
        while (packetsRead < 3) {
            int read = inputStream.read(buffer, index, bufferSize);
            syncState.wrote(read);
            switch (syncState.pageout(page)) {
            case -1:
                return Optional.absent();
            case 1:
                if (!streamStateInitialized) {
                    /* init stream state. */
                    streamState.init(page.serialno());
                    streamState.reset();
                    info.init();
                    comment.init();
                    streamStateInitialized = true;
                }
                if (streamState.pagein(page) == -1) {
                    return Optional.absent();
                }
                switch (streamState.packetout(packet)) {
                case -1:
                    return Optional.absent();
                case 1:
                    info.synthesis_headerin(comment, packet);
                    packetsRead++;
                default:
                    /* continue. */
                }

            default:
                /* continue. */
            }
            index = syncState.buffer(bufferSize);
            buffer = syncState.data;
        }

        FormatMetadata formatMetadata = new FormatMetadata(info.channels, info.rate, "Vorbis");
        ContentMetadata contentMetadata = new ContentMetadata("");
        for (int c = 0; c < comment.comments; ++c) {
            String field = comment.getComment(c);
            Optional<String> extractedField = extractField(field, "ARTIST");
            if (extractedField.isPresent()) {
                contentMetadata = contentMetadata.artist(extractedField.get());
                continue;
            }
            extractedField = extractField(field, "TITLE");
            if (extractedField.isPresent()) {
                contentMetadata = contentMetadata.name(extractedField.get());
                continue;
            }
        }
        return Optional.of(new Metadata(formatMetadata, contentMetadata));
    }

    /**
     * Extracts the content of the field from the comment if the comment contains
     * the given field.
     *
     * @param comment
     *       The comment to extract the value from
     * @param fieldName
     *       The name of the field to extract
     * @return The extracted field, or {@link Optional#absent()} if the comment
     *         does not contain the given field
     */
    private static Optional<String> extractField(String comment, String fieldName) {
        if (comment.startsWith(fieldName + "=")) {
            return Optional.of(comment.substring(fieldName.length() + 1));
        }
        return Optional.absent();
    }

}