depacketizer.java

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				expect += b.getLength() - JpegRTPHeader.HEADER_SIZE;
				
			}
			return true;
		}

		/**
		 * Total length of all fragments.  Does not include JPEG header. 
		 * Assumes that complete() has been called and returns true.
		 */
		public int frameLength()
		{
			if (!rtpMarker)
				throw new IllegalStateException();
			if (list.size() <= 0)
				throw new IllegalStateException();
			
			// calculate from offset and length of last buffer:
			final Buffer b = (Buffer) list.get(list.size() - 1);
			final JpegRTPHeader jpegRtpHeader = parseJpegRTPHeader(b);
			// Observed: the frame with the marker has valid offset, 
			return jpegRtpHeader.getFragmentOffset() + b.getLength() - JpegRTPHeader.HEADER_SIZE;

		}
		
		/**
		 * Assumes that complete() has been called and returns true.
		 */
		public int copyToBuffer(Buffer bDest)
		{
			if (!rtpMarker)
				throw new IllegalStateException();
			if (list.size() <= 0)
				throw new IllegalStateException();

			// TODO: perhaps what we should do is copy the header if there is not one.
			// The test samples coming from JMStudio had headers in them, so the JPEG could not be
			// parsed if (another) header was prepended.
			final Buffer bFirst = (Buffer) list.get(0);
			final boolean prependHeader = !hasJPEGHeaders((byte []) bFirst.getData(), bFirst.getOffset() + JpegRTPHeader.HEADER_SIZE, bFirst.getLength() - JpegRTPHeader.HEADER_SIZE);
			final int MAX_HEADER = prependHeader ? 1024 : 0;	// TODO: what is actual max size for the header?  Seems to be fixed size, 600-700 bytes.
			final int MAX_TRAILER = 2;
			final int frameLength = frameLength();
			final byte[] data;
			if (bDest.getData() != null && ((byte []) bDest.getData()).length >= (frameLength + MAX_HEADER + MAX_TRAILER))
			{	data = (byte []) bDest.getData();	// reuse existing byte array
				// zero out:
				zeroData(data);

			}
			else
			{	data = new byte[frameLength + MAX_HEADER + MAX_TRAILER];	// allocate new one - existing one not there or too short
			}
			
			int offsetAfterHeaders = 0;
			if (prependHeader)
			{	
				// put initial SOI marker manually, we tell RFC2035.MakeHeaders not to do it:
				data[offsetAfterHeaders++] = (byte) 0xff;
				data[offsetAfterHeaders++] = (byte) 0xd8;
				
				// part of the header with "JFIF" in it, not generated by the code in RFC2035.
				offsetAfterHeaders = buildJFIFHeader(data, offsetAfterHeaders);

				final JpegRTPHeader jpegRtpHeaderFirst = parseJpegRTPHeader(bFirst);
				offsetAfterHeaders = RFC2035.MakeHeaders(false, data, offsetAfterHeaders, jpegRtpHeaderFirst.getType(), jpegRtpHeaderFirst.getQ(), jpegRtpHeaderFirst.getWidthInBlocks(), jpegRtpHeaderFirst.getHeightInBlocks());
			}
			if (TRACE) System.out.println("offsetAfterHeaders=" + offsetAfterHeaders);
			for (int i = 0; i < list.size(); ++i)
			{	final Buffer b = (Buffer) list.get(i);
				final JpegRTPHeader jpegRtpHeader = parseJpegRTPHeader(b);
//				
//				if (TRACE) System.out.println("Copying, length=" + (b.getLength() - JpegRTPHeader.HEADER_SIZE) + ":");
//				if (TRACE) System.out.println(dump((byte[]) b.getData(), b.getOffset() + JpegRTPHeader.HEADER_SIZE, (b.getLength() - JpegRTPHeader.HEADER_SIZE) > MAX_DUMP_SIZE ? MAX_DUMP_SIZE : (b.getLength() - JpegRTPHeader.HEADER_SIZE)));
//				if (TRACE) System.out.println("End copying.");
				
				System.arraycopy((byte []) b.getData(), b.getOffset() + JpegRTPHeader.HEADER_SIZE, data, offsetAfterHeaders + jpegRtpHeader.getFragmentOffset(), b.getLength() - JpegRTPHeader.HEADER_SIZE);
			}
			
			final boolean appendEOI = !hasJPEGTrailer(data, offsetAfterHeaders + frameLength, MAX_TRAILER);	// no need to append if it is already there.
			int trailing = 0;
			if (appendEOI)
			{
				data[offsetAfterHeaders + frameLength + trailing++] = (byte) 0xff;
				data[offsetAfterHeaders + frameLength + trailing++] = (byte) 0xd9;
			}
			
			bDest.setData(data);
			bDest.setLength(offsetAfterHeaders + frameLength + trailing);
			bDest.setOffset(0);
			bDest.setTimeStamp(bFirst.getTimeStamp());	// TODO: is the source buffer timestamp in same units?
			return offsetAfterHeaders;
		}
	}
	
	private static void zeroData(byte[] data)
	{
		int len = data.length;
		for (int i = 0; i < len; ++i)
		{	data[i] = 0;
		}
	}
	
	/**
	 * Checks to see if the data begins with SOI.  Refers to JPEG headers, not JPEGRTP headers.
	 */
	private static boolean hasJPEGHeaders(byte[] data, int offset, int len)
	{	
		if (len < 2)
			throw new IllegalArgumentException();
		if (data[offset++] != (byte) 0xff)
			return false;
		if (data[offset++] != (byte) 0xd8)
			return false;

		return true;	// starts with SOI
	}
	
	private static boolean hasJPEGTrailer(byte[] data, int offset, int len)
	{	
		if (len < 2)
			throw new IllegalArgumentException();
		if (data[offset++] != (byte) 0xff)
			return false;
		if (data[offset++] != (byte) 0xd9)
			return false;

		return true;	// ends with EOI
	}
	
	// 
	/**
	 * info on JFIF header at http://www.obrador.com/essentialjpeg/headerinfo.htm
	 * @return new offset
	 */
	private static int buildJFIFHeader(byte[] data, int offset)
	{
		// example:
//		 ffe000104a46494600010100000100010000
		
//		 JFIF marker (0xFFE0)
		data[offset++] = (byte) 0xff;	
		data[offset++] = (byte) 0xe0;
		
//	    *  length -- two bytes
		data[offset++] = (byte) 0x00;	
		data[offset++] = (byte) 0x10;	
		
//	    * identifier -- five bytes: 4A, 46, 49, 46, 00 (the ASCII code equivalent of a zero terminated "JFIF" string)
		data[offset++] = (byte) 0x4a;	
		data[offset++] = (byte) 0x46;	
		data[offset++] = (byte) 0x49;	
		data[offset++] = (byte) 0x46;	
		data[offset++] = (byte) 0x00;	
		
//	    * version -- two bytes: often 01, 02
//	          o the most significant byte is used for major revisions
//	          o the least significant byte for minor revisions
//
		data[offset++] = (byte) 0x01;	
		data[offset++] = (byte) 0x01;	
		
//	    * units -- one byte: Units for the X and Y densities
//	          o 0 => no units, X and Y specify the pixel aspect ratio
//	          o 1 => X and Y are dots per inch
//	          o 2 => X and Y are dots per cm
		data[offset++] = (byte) 0x00;	
		
//	    * Xdensity -- two bytes
		data[offset++] = (byte) 0x00;	
		data[offset++] = (byte) 0x01;
		
//	    * Ydensity -- two bytes
		data[offset++] = (byte) 0x00;	
		data[offset++] = (byte) 0x01;	
		
//	    * Xthumbnail -- one byte: 0 = no thumbnail
		data[offset++] = (byte) 0x00;	
		
//	    * Ythumbnail -- one byte: 0 = no thumbnail
		data[offset++] = (byte) 0x00;	
		

		return offset;
	}

	private static final BufferFragmentOffsetComparator bufferFragmentOffsetComparator = new BufferFragmentOffsetComparator();

	/**
	 * Compares buffers by the fragment offset.  Assumes buffers have
	 * enough data in them for a JpegRTPHeader.
	 * @author Ken Larson
	 *
	 */
	private static class BufferFragmentOffsetComparator implements Comparator
	{
		
		public int compare(Object a, Object b)
		{
			if (a == null && b == null)
				return 0;
			if (a == null)	// then a < b, return -1
				return -1;
			if (b == null)
				return 1;	// a > b
			
			final Buffer aCast = (Buffer) a;
			final Buffer bCast = (Buffer) b;
			
			final JpegRTPHeader jpegRtpHeaderA = JpegRTPHeader.parse((byte[]) aCast.getData(), aCast.getOffset());
			final JpegRTPHeader jpegRtpHeaderB = JpegRTPHeader.parse((byte[]) bCast.getData(), bCast.getOffset());
			
			return jpegRtpHeaderA.getFragmentOffset() - jpegRtpHeaderB.getFragmentOffset();

		}
	}
	
	/**
	 * Keeps track of multiple FrameAssemblers for different timestamps.  
	 * This is needed because packets may arrive out of order.
	 * @author Ken Larson
	 *
	 */
	private static class FrameAssemblerCollection
	{
		private Map frameAssemblers = new HashMap();	// FrameAssembler keyed by long - timestamp.
	
		public FrameAssembler findOrAdd(long timestamp)
		{	FrameAssembler result = (FrameAssembler) frameAssemblers.get(new Long(timestamp));
			if (result == null)
			{	result = new FrameAssembler();
				frameAssemblers.put(new Long(timestamp), result);
			}
			return result;
		}
		public void remove(FrameAssembler a)
		{	frameAssemblers.remove(a);
		}
		public void removeOlderThan(long timestamp)
		{
			final Iterator i = frameAssemblers.entrySet().iterator();
			while (i.hasNext())
			{
				final Entry e = (Entry) i.next();
				final Long entryTimestamp = (Long) e.getKey();
				if (entryTimestamp.longValue() < timestamp)
				{	if (TRACE) System.out.println("Discarding incomplete frame older than " + timestamp + ", ts=" + entryTimestamp);
					i.remove();
				}
			}
			
		}
		public void removeAllButNewestN(int n)
		{
			while (frameAssemblers.size() > n)
			{	
				final long oldestTimestamp = getOldestTimestamp();
				if (oldestTimestamp < 0)
					throw new RuntimeException();
				Long key = new Long(oldestTimestamp);
				FrameAssembler a = (FrameAssembler) frameAssemblers.get(key);
				String completeIncomplete = a.complete() ? "complete" : "incomplete";
				if (TRACE) System.out.println("Discarding " + completeIncomplete + " frame (not in newest " + n + ", ts=" + oldestTimestamp);
				frameAssemblers.remove(key);
			}
			
		}
		public long getOldestTimestamp()
		{
			long oldestSoFar = -1;
			
			final Iterator i = frameAssemblers.keySet().iterator();
			while (i.hasNext())
			{
				final Long ts = (Long) i.next();
				if (oldestSoFar < 0 || ts.longValue() < oldestSoFar)
					oldestSoFar = ts.longValue();
			}
			return oldestSoFar;
			
		}
		public void clear()
		{	frameAssemblers.clear();
		}
	}
	

	
	private static final int MAX_DUMP_SIZE = 200000;
	
	/**
	 * Debugging only.  In this version, len is the length to dump to the string, not the
	 * length minus offset as in StringUtils.  Returns the string instead of pringing to std out.
	 */
	private static String dump(byte[] data, int offset, int len)
	{
		return StringUtils.dump(data, offset, offset + len);

	}
	/**
	 * Debugging only.  Dumps as hex to std out.
	 */
	private static void dump(Buffer b, String name)
	{
		if (TRACE) System.out.println(name + ", length=" + b.getLength() + " :");
		if (TRACE) System.out.println(dump((byte[]) b.getData(), b.getOffset(), b.getLength() > MAX_DUMP_SIZE ? MAX_DUMP_SIZE : b.getLength()));

	}
}