rtppacket.java

结构非常清晰的SIP协议栈

/*
 * Copyright (C) 2005 Luca Veltri - University of Parma - Italy
 * 
 * This source code 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 2 of the License, or
 * (at your option) any later version.
 * 
 * This source code 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 source code; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 * Author(s):
 * Luca Veltri ([e-mail])
 */

package local.net;


import org.zoolu.tools.Random;


/** RtpPacket implements a RTP packet. 
 */
public class RtpPacket
{
   /* RTP packet buffer containing both the RTP header and payload */   
   byte[] packet;

   /* RTP packet length */   
   int packet_len;

   /* RTP header length */   
   //int header_len;

   /** Gets the RTP packet */
   public byte[] getPacket()
   {  return packet;
   }

   /** Gets the RTP packet length */
   public int getLength()
   {  return packet_len;
   }

   /** Gets the RTP header length */
   public int getHeaderLength()
   {  if (packet_len>=12) return 12+4*getCscrCount();
      else return packet_len; // broken packet
   }

   /** Gets the RTP header length */
   public int getPayloadLength()
   {  if (packet_len>=12) return packet_len-getHeaderLength();
      else return 0; // broken packet
   }

   /** Sets the RTP payload length */
   public void setPayloadLength(int len)
   {  packet_len=getHeaderLength()+len;
   }

   // version (V): 2 bits
   // padding (P): 1 bit
   // extension (X): 1 bit
   // CSRC count (CC): 4 bits
   // marker (M): 1 bit
   // payload type (PT): 7 bits
   // sequence number: 16 bits
   // timestamp: 32 bits
   // SSRC: 32 bits
   // CSRC list: 0 to 15 items, 32 bits each


   /** Gets the version (V) */
   public int getVersion()
   {  if (packet_len>=12) return (packet[0]>>6 & 0x03);
      else return 0; // broken packet 
   }

   /** Sets the version (V) */
   public void setVersion(int v)
   {  if (packet_len>=12) packet[0]=(byte)((packet[0] & 0x3F) | ((v & 0x03)<<6));
   }

   /** Whether has padding (P) */
   public boolean hasPadding()
   {  if (packet_len>=12) return getBit(packet[0],5);
      else return false; // broken packet 
   }

   /** Set padding (P) */
   public void setPadding(boolean p)
   {  if (packet_len>=12) setBit(p,packet[0],5);
   }

   /** Whether has extension (X) */
   public boolean hasExtension()
   {  if (packet_len>=12) return getBit(packet[0],4);
      else return false; // broken packet 
   }

   /** Set extension (X) */
   public void setExtension(boolean x)
   {  if (packet_len>=12) setBit(x,packet[0],4);
   }

   /** Gets the CSCR count (CC) */
   public int getCscrCount()
   {  if (packet_len>=12) return (packet[0] & 0x0F);
      else return 0; // broken packet
   }

   /** Whether has marker (M) */
   public boolean hasMarker()
   {  if (packet_len>=12) return getBit(packet[1],7);
      else return false; // broken packet 
   }

   /** Set marker (M) */
   public void setMarker(boolean m)
   {  if (packet_len>=12) setBit(m,packet[1],7);
   }

   /** Gets the payload type (PT) */
   public int getPayloadType()
   {  if (packet_len>=12) return (packet[1] & 0x7F);
      else return -1; // broken packet
   }

   /** Sets the payload type (PT) */
   public void setPayloadType(int pt)
   {  if (packet_len>=12) packet[1]=(byte)((packet[1] & 0x80) | (pt & 0x7F));
   }

   /** Gets the sequence number */
   public int getSequenceNumber()
   {  if (packet_len>=12) return getInt(packet,2,4);
      else return 0; // broken packet
   }

   /** Sets the sequence number */
   public void setSequenceNumber(int sn)
   {  if (packet_len>=12) setInt(sn,packet,2,4);
   }

   /** Gets the timestamp */
   public long getTimestamp()
   {  if (packet_len>=12) return getLong(packet,4,8);
      else return 0; // broken packet
   }

   /** Sets the timestamp */
   public void setTimestamp(long timestamp)
   {  if (packet_len>=12) setLong(timestamp,packet,4,8);
   }
   
   /** Gets the SSCR */
   public long getSscr()
   {  if (packet_len>=12) return getLong(packet,8,12);
      else return 0; // broken packet
   }

   /** Sets the SSCR */
   public void setSscr(long ssrc)
   {  if (packet_len>=12) setLong(ssrc,packet,8,12);
   }

   /** Gets the CSCR list */
   public long[] getCscrList()
   {  int cc=getCscrCount();
      long[] cscr=new long[cc];
      for (int i=0; i<cc; i++) cscr[i]=getLong(packet,12+4*i,16+4*i); 
      return cscr;
   }

   /** Sets the CSCR list */
   public void setCscrList(long[] cscr)
   {  if (packet_len>=12)
      {  int cc=cscr.length;
         if (cc>15) cc=15;
         packet[0]=(byte)(((packet[0]>>4)<<4)+cc);
         cscr=new long[cc];
         for (int i=0; i<cc; i++) setLong(cscr[i],packet,12+4*i,16+4*i);   
         //header_len=12+4*cc;
      }
   }

   /** Sets the payload */
   public void setPayload(byte[] payload, int len)
   {  if (packet_len>=12)
      {  int header_len=getHeaderLength();
         for (int i=0; i<len; i++) packet[header_len+i]=payload[i]; 
         packet_len=header_len+len;
      }
   }

   /** Gets the payload */
   public byte[] getPayload()
   {  int header_len=getHeaderLength();
      int len=packet_len-header_len;
      byte[] payload=new byte[len];
      for (int i=0; i<len; i++) payload[i]=packet[header_len+i]; 
      return payload;
   }

   /** Creates a new RTP packet */ 
   public RtpPacket(byte[] buffer, int packet_length)
   {  packet=buffer;
      packet_len=packet_length;
      if (packet_len<12) packet_len=12;
      init(0x0F);
   }


   /** init the RTP packet header (only PT) */ 
   public void init(int ptype)
   {  init(ptype,Random.nextLong());
   }


   /** init the RTP packet header (PT and SSCR) */ 
   public void init(int ptype, long sscr)
   {  init(ptype,Random.nextInt(),Random.nextLong(),sscr);
   }
   

   /** init the RTP packet header (PT, SQN, TimeStamp, SSCR) */ 
   public void init(int ptype, int seqn, long timestamp, long sscr)
   {  setVersion(2);
      setPayloadType(ptype);
      setSequenceNumber(seqn);
      setTimestamp(timestamp);
      setSscr(sscr);
   }

   // *********************** Private and Static ***********************

   /** Gets int value */
   private static int getInt(byte b)
   {  return ((int)b+256)%256;
   }

   /** Gets long value */
   private static long getLong(byte[] data, int begin, int end)
   {  long n=0;
      for (; begin<end; begin++)
      {  n<<=8;
         n+=data[begin];
      }
      return n;
   }

   /** Sets long value */
   private static void setLong(long n, byte[] data, int begin, int end)
   {  for (end-- ; end>=begin; end--)
      {  data[end]=(byte)(n%256);
         n>>=8;
      }
   }

   /** Gets Int value */
   private static int getInt(byte[] data, int begin, int end)
   {  return (int)getLong(data,begin,end);
   }

   /** Sets Int value */
   private static void setInt(int n, byte[] data, int begin, int end)
   {  setLong(n,data,begin,end);
   }

   /** Gets bit value */
   private static boolean getBit(byte b, int bit)
   {  return (b>>bit)==1;
   }

   /** Sets bit value */
   private static void setBit(boolean value, byte b, int bit)
   {  if (value) b=(byte)(b|(1<<bit));
      else b=(byte)((b|(1<<bit))^(1<<bit));
   }
}