# $Id: rtp.py 23 2006-11-08 15:45:33Z dugsong $

"""Real-Time Transport Protocol"""

from dpkt import Packet

# version 1100 0000 0000 0000 ! 0xC000  14
# p       0010 0000 0000 0000 ! 0x2000  13
# x       0001 0000 0000 0000 ! 0x1000  12
# cc      0000 1111 0000 0000 ! 0x0F00   8
# m       0000 0000 1000 0000 ! 0x0080   7
# pt      0000 0000 0111 1111 ! 0x007F   0
#

_VERSION_MASK= 0xC000
_P_MASK     = 0x2000
_X_MASK     = 0x1000
_CC_MASK    = 0x0F00
_M_MASK     = 0x0080
_PT_MASK    = 0x007F
_VERSION_SHIFT=14
_P_SHIFT    = 13
_X_SHIFT    = 12
_CC_SHIFT   = 8
_M_SHIFT    = 7
_PT_SHIFT   = 0

VERSION = 2

class RTP(Packet):
    __hdr__ = (
        ('_type', 'H',      0x8000),
        ('seq',     'H',    0),
        ('ts',      'I',    0),
        ('ssrc',    'I',    0),
    )
    csrc = ''

    def _get_version(self): return (self._type&_VERSION_MASK)>>_VERSION_SHIFT
    def _set_version(self, ver):
        self._type = (ver << _VERSION_SHIFT) | (self._type & ~_VERSION_MASK)
    def _get_p(self): return (self._type & _P_MASK) >> _P_SHIFT
    def _set_p(self, p): self._type = (p << _P_SHIFT) | (self._type & ~_P_MASK)
    def _get_x(self): return (self._type & _X_MASK) >> _X_SHIFT
    def _set_x(self, x): self._type = (x << _X_SHIFT) | (self._type & ~_X_MASK)
    def _get_cc(self): return (self._type & _CC_MASK) >> _CC_SHIFT
    def _set_cc(self, cc): self._type = (cc<<_CC_SHIFT)|(self._type&~_CC_MASK)
    def _get_m(self): return (self._type & _M_MASK) >> _M_SHIFT
    def _set_m(self, m): self._type = (m << _M_SHIFT) | (self._type & ~_M_MASK)
    def _get_pt(self): return (self._type & _PT_MASK) >> _PT_SHIFT
    def _set_pt(self, m): self._type = (m << _PT_SHIFT)|(self._type&~_PT_MASK)

    version = property(_get_version, _set_version)
    p = property(_get_p, _set_p)
    x = property(_get_x, _set_x)
    cc = property(_get_cc, _set_cc)
    m = property(_get_m, _set_m)
    pt = property(_get_pt, _set_pt)

    def __len__(self):
        return self.__hdr_len__ + len(self.csrc) + len(self.data)

    def __str__(self):
        return self.pack_hdr() + self.csrc + str(self.data)

    def unpack(self, buf):
        super(RTP, self).unpack(buf)
        self.csrc = buf[self.__hdr_len__:self.__hdr_len__ + self.cc * 4]
        self.data = buf[self.__hdr_len__ + self.cc * 4:]