/*

  * Entagged Audio Tag library

  * Copyright (c) 2003-2005 Rapha�l Slinckx <raphael@slinckx.net>

  * 

  * This library is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public

  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *  

  * This library 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

  * Lesser General Public License for more details.

  * 

  * You should have received a copy of the GNU Lesser General Public

  * License along with this library; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

  */

 package org.jaudiotagger.audio.ogg.util;

 import org.jaudiotagger.audio.exceptions.CannotReadException;

 import org.jaudiotagger.audio.generic.Utils;

 import java.io.IOException;

 import java.io.RandomAccessFile;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.List;

 import java.util.logging.Logger;

 /**

  * $Id: OggPageHeader.java,v 1.14 2008/07/21 10:48:37 paultaylor Exp $

  * <p/>

  * reference:http://xiph.org/ogg/doc/framing.html

  *

  * @author Raphael Slinckx (KiKiDonK)

  * @version 16 d�cembre 2003

  */

 public class OggPageHeader

 {

     // Logger Object

     public static Logger logger = Logger.getLogger("org.jaudiotagger.audio.ogg.atom");

     //Capture pattern at start of header

     public static final byte[] CAPTURE_PATTERN = {'O', 'g', 'g', 'S'};

     //Ogg Page header is always 27 bytes plus the size of the segment table which is variable

     public static final int OGG_PAGE_HEADER_FIXED_LENGTH = 27;

     //Can have upto 255 segments in a page

     public static final int MAXIMUM_NO_OF_SEGMENT_SIZE = 255;

     //Each segment can be upto 255 bytes

     public static final int MAXIMUM_SEGMENT_SIZE = 255;

     //Maximum size of pageheader (27 + 255 = 282)

     public static final int MAXIMUM_PAGE_HEADER_SIZE = OGG_PAGE_HEADER_FIXED_LENGTH + MAXIMUM_NO_OF_SEGMENT_SIZE;

     //Maximum size of page data following the page header (255 * 255 = 65025)

     public static final int MAXIMUM_PAGE_DATA_SIZE = MAXIMUM_NO_OF_SEGMENT_SIZE * MAXIMUM_SEGMENT_SIZE;

     //Maximum size of page includes header and data (282 + 65025 = 65307 bytes)

     public static final int MAXIMUM_PAGE_SIZE = MAXIMUM_PAGE_HEADER_SIZE + MAXIMUM_PAGE_DATA_SIZE;

     //Starting positions of the various attributes

     public static final int FIELD_CAPTURE_PATTERN_POS = 0;

     public static final int FIELD_STREAM_STRUCTURE_VERSION_POS = 4;

     public static final int FIELD_HEADER_TYPE_FLAG_POS = 5;

     public static final int FIELD_ABSOLUTE_GRANULE_POS = 6;

     public static final int FIELD_STREAM_SERIAL_NO_POS = 14;

     public static final int FIELD_PAGE_SEQUENCE_NO_POS = 18;

     public static final int FIELD_PAGE_CHECKSUM_POS = 22;

     public static final int FIELD_PAGE_SEGMENTS_POS = 26;

     public static final int FIELD_SEGMENT_TABLE_POS = 27;

     //Length of various attributes

     public static final int FIELD_CAPTURE_PATTERN_LENGTH = 4;

     public static final int FIELD_STREAM_STRUCTURE_VERSION_LENGTH = 1;

     public static final int FIELD_HEADER_TYPE_FLAG_LENGTH = 1;

     public static final int FIELD_ABSOLUTE_GRANULE_LENGTH = 8;

     public static final int FIELD_STREAM_SERIAL_NO_LENGTH = 4;

     public static final int FIELD_PAGE_SEQUENCE_NO_LENGTH = 4;

     public static final int FIELD_PAGE_CHECKSUM_LENGTH = 4;

     public static final int FIELD_PAGE_SEGMENTS_LENGTH = 1;

     private byte[] rawHeaderData;

     private double absoluteGranulePosition;

     private int checksum;

     private byte headerTypeFlag;

     private boolean isValid = false;

     private int pageLength = 0;

     private int pageSequenceNumber, streamSerialNumber;

     private byte[] segmentTable;

     private List<PacketStartAndLength> packetList = new ArrayList<PacketStartAndLength>();

     private boolean lastPacketIncomplete = false;

     public static OggPageHeader read(RandomAccessFile raf) throws IOException, CannotReadException

     {

         long start = raf.getFilePointer();

         logger.info("Trying to read OggPage at:" + start);

         byte[] b = new byte[OggPageHeader.CAPTURE_PATTERN.length];

         raf.read(b);

         if (!(Arrays.equals(b, OggPageHeader.CAPTURE_PATTERN)))

         {

             throw new CannotReadException("OggS Header could not be found, not an ogg stream:" + new String(b));

         }

         raf.seek(start + OggPageHeader.FIELD_PAGE_SEGMENTS_POS);

         int pageSegments = raf.readByte() & 0xFF; //unsigned

         raf.seek(start);

         b = new byte[OggPageHeader.OGG_PAGE_HEADER_FIXED_LENGTH + pageSegments];

         raf.read(b);

         OggPageHeader pageHeader = new OggPageHeader(b);

         //Now just after PageHeader, ready for Packet Data

         return pageHeader;

     }

     public OggPageHeader(byte[] b)

     {

         this.rawHeaderData = b;

         int streamStructureRevision = b[FIELD_STREAM_STRUCTURE_VERSION_POS];

         headerTypeFlag = b[FIELD_HEADER_TYPE_FLAG_POS];

         if (streamStructureRevision == 0)

         {

             this.absoluteGranulePosition = 0;

             for (int i = 0; i < FIELD_ABSOLUTE_GRANULE_LENGTH; i++)

             {

                 this.absoluteGranulePosition += u(b[i + FIELD_ABSOLUTE_GRANULE_POS]) * Math.pow(2, 8 * i);

             }

             streamSerialNumber = Utils.getIntLE(b, FIELD_STREAM_SERIAL_NO_POS, 17);

             pageSequenceNumber = Utils.getIntLE(b, FIELD_PAGE_SEQUENCE_NO_POS, 21);

             checksum = Utils.getIntLE(b, FIELD_PAGE_CHECKSUM_POS, 25);

             int pageSegments = u(b[FIELD_PAGE_SEGMENTS_POS]);

             this.segmentTable = new byte[b.length - OGG_PAGE_HEADER_FIXED_LENGTH];

             int packetLength = 0;

             Integer segmentLength = null;

             for (int i = 0; i < segmentTable.length; i++)

             {

                 segmentTable[i] = b[OGG_PAGE_HEADER_FIXED_LENGTH + i];

                 segmentLength = u(segmentTable[i]);

                 this.pageLength += segmentLength;

                 packetLength += segmentLength;

                 if (segmentLength < MAXIMUM_SEGMENT_SIZE)

                 {

                     packetList.add(new PacketStartAndLength(pageLength - packetLength, packetLength));

                     packetLength = 0;

                 }

             }

             //If last segment value is 255 this packet continues onto next page

             //and will not have been added to the packetStartAndEnd list yet

             if (segmentLength == MAXIMUM_SEGMENT_SIZE)

             {

                 packetList.add(new PacketStartAndLength(pageLength - packetLength, packetLength));

                 lastPacketIncomplete = true;

             }

             isValid = true;

         }

         logger.info("Constructed OggPage:" + this.toString());

     }

     private int u(int i)

     {

         return i & 0xFF;

     }

     /**

      * @return true if the last packet on this page extends to the next page

      */

     public boolean isLastPacketIncomplete()

     {

         return lastPacketIncomplete;

     }

     public double getAbsoluteGranulePosition()

     {

         logger.fine("Number Of Samples: " + absoluteGranulePosition);

         return this.absoluteGranulePosition;

     }

     public int getCheckSum()

     {

         return checksum;

     }

     public byte getHeaderType()

     {

         return headerTypeFlag;

     }

     public int getPageLength()

     {

         logger.fine("This page length: " + pageLength);

         return this.pageLength;

     }

     public int getPageSequence()

     {

         return pageSequenceNumber;

     }

     public int getSerialNumber()

     {

         return streamSerialNumber;

     }

     public byte[] getSegmentTable()

     {

         return this.segmentTable;

     }

     public boolean isValid()

     {

         return isValid;

     }

     /**

      * @return a list of packet start position and size within this page.

      */

     public List<PacketStartAndLength> getPacketList()

     {

         return packetList;

     }

     /**

      * @return the raw header data that this pageheader is derived from

      */

     public byte[] getRawHeaderData()

     {

         return rawHeaderData;

     }

     public String toString()

     {

         String out = "Ogg Page Header:isValid:" + isValid + ":type:" + headerTypeFlag + ":oggPageHeaderLength:" + rawHeaderData.length + ":length:" + pageLength + ":seqNo:" + getPageSequence() + ":packetIncomplete:" + isLastPacketIncomplete() + ":serNum:" + this.getSerialNumber();

         for (PacketStartAndLength packet : getPacketList())

         {

             out += packet.toString();

         }

         return out;

     }

     /**

      * Within the page specifies the start and length of each packet

      * in the page offset from the end of the pageheader (after the segment table)

      */

     public static class PacketStartAndLength

     {

         private Integer startPosition = 0;

         private Integer length = 0;

         public PacketStartAndLength(int startPosition, int length)

         {

             this.startPosition = startPosition;

             this.length = length;

         }

         public int getStartPosition()

         {

             return startPosition;

         }

         public void setStartPosition(int startPosition)

         {

             this.startPosition = startPosition;

         }

         public int getLength()

         {

             return length;

         }

         public void setLength(int length)

         {

             this.length = length;

         }

         public String toString()

         {

             return "NextPkt(start:" + startPosition + ":length:" + length + "),";

         }

     }

     /**

      * This represents all the flags that can be set in the headerType field.

      * Note these values can be ORED together. For example the last packet in

      * a file would normally have a value of 0x5 because both the CONTINUED_PACKET

      * bit and the END_OF_BITSTREAM bit would be set.

      */

     public static enum HeaderTypeFlag

     {

         FRESH_PACKET((byte) 0x0),

         CONTINUED_PACKET((byte) 0x1),

         START_OF_BITSTREAM((byte) 0x2),

         END_OF_BITSTREAM((byte) 0x4);

         byte fileValue;

         HeaderTypeFlag(byte fileValue)

         {

             this.fileValue = fileValue;

         }

         /**

          * @return the value that should be written to file to enable this flag

          */

         public byte getFileValue()

         {

             return fileValue;

         }

     }

 }