void buf_shr_bits(u8 *buf, u32 buf_size, u32 bits_num, u8 bit_fill)
{u8 bit_tmp, bit_prev;
 u32 bytes_cnt;
 //bits shift loop
 while (bits_num--)
 {buf += buf_size; //start from the end of buffer
  bit_prev = bit_fill;
  //1 bit buffer shift loop
  for (bytes_cnt=buf_size; bytes_cnt; bytes_cnt--)
  {
   buf--;
   bit_tmp = (*buf) & 1;
   (*buf) >>= 1; //shift next byte
   if (bit_prev) (*buf) |= 0x80;
   bit_prev = bit_tmp;
  }
 }
}