Filling a byte array in Java

Posted by Corleone on Stack Overflow See other posts from Stack Overflow or by Corleone
Published on 2010-04-10T18:29:55Z Indexed on 2010/04/10 18:33 UTC
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Hey all!

For part of a project I'm working on I am implementing a RTPpacket where I have to fill the header array of byte with RTP header fields.

  //size of the RTP header:
  static int HEADER_SIZE = 12; // bytes

  //Fields that compose the RTP header
  public int Version; // 2 bits
  public int Padding; // 1 bit
  public int Extension; // 1 bit
  public int CC; // 4 bits
  public int Marker; // 1 bit
  public int PayloadType; // 7 bits
  public int SequenceNumber; // 16 bits
  public int TimeStamp; // 32 bits
  public int Ssrc; // 32 bits

  //Bitstream of the RTP header
  public byte[] header = new byte[ HEADER_SIZE ];

This was my approach:

/*      
 * bits 0-1: Version
 * bit    2: Padding 
 * bit    3: Extension
 * bits 4-7: CC
 */
header[0] = new Integer( (Version << 6)|(Padding << 5)|(Extension << 6)|CC ).byteValue();

/* 
 * bit    0: Marker
 * bits 1-7: PayloadType
 */
header[1] = new Integer( (Marker << 7)|PayloadType ).byteValue();

/* SequenceNumber takes 2 bytes = 16 bits */
header[2] = new Integer( SequenceNumber >> 8 ).byteValue();
header[3] = new Integer( SequenceNumber ).byteValue();

/* TimeStamp takes 4 bytes = 32 bits */
for ( int i = 0; i < 4; i++ )
    header[7-i] = new Integer( TimeStamp >> (8*i) ).byteValue();

/* Ssrc takes 4 bytes = 32 bits */
for ( int i = 0; i < 4; i++ )
    header[11-i] = new Integer( Ssrc >> (8*i) ).byteValue();

Any other, maybe 'better' ways to do this?

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