static void
powercycle_turn_radio_off(void)
{
  if(we_are_sending == 0 &&
     waiting_for_packet == 0) {
    off();
  }
#if XMAC_CONF_COMPOWER
  compower_accumulate(&compower_idle_activity);
#endif /* XMAC_CONF_COMPOWER */
}

/**
 * Send a probe packet.
 */
static void
send_probe(void)
{
  struct lpp_hdr *hdr;
  struct announcement_msg *adata;
  struct announcement *a;

  /* Set up the probe header. */
  packetbuf_clear();
  packetbuf_set_datalen(sizeof(struct lpp_hdr));
  hdr = packetbuf_dataptr();
  hdr->type = TYPE_PROBE;
  rimeaddr_copy(&hdr->sender, &rimeaddr_node_addr);
  /*  rimeaddr_copy(&hdr->receiver, packetbuf_addr(PACKETBUF_ADDR_RECEIVER));*/
  rimeaddr_copy(&hdr->receiver, &rimeaddr_null);

  packetbuf_set_addr(PACKETBUF_ADDR_RECEIVER, &rimeaddr_null);
  {
    int hdrlen = NETSTACK_FRAMER.create();
    if(hdrlen == 0) {
      /* Failed to send */
      return;
    }
  }
  
  /* Construct the announcements */
  adata = (struct announcement_msg *)((char *)hdr + sizeof(struct lpp_hdr));
  
  adata->num = 0;
  for(a = announcement_list(); a != NULL; a = list_item_next(a)) {
    adata->data[adata->num].id = a->id;
    adata->data[adata->num].value = a->value;
    adata->num++;
  }

  packetbuf_set_datalen(sizeof(struct lpp_hdr) +
		      ANNOUNCEMENT_MSG_HEADERLEN +
		      sizeof(struct announcement_data) * adata->num);

  /*  PRINTF("Sending probe\n");*/

  /*  printf("probe\n");*/

  if(NETSTACK_RADIO.channel_clear()) {
    NETSTACK_RADIO.send(packetbuf_hdrptr(), packetbuf_totlen());
  } else {
    off_time_adjustment = random_rand() % (OFF_TIME / 2);
  }

  compower_accumulate(&compower_idle_activity);
}

/*---------------------------------------------------------------------------*/
static void
powercycle_turn_radio_off(void)
{
#if CONTIKIMAC_CONF_COMPOWER
  uint8_t was_on = radio_is_on;
#endif /* CONTIKIMAC_CONF_COMPOWER */
  
  if(we_are_sending == 0 && we_are_receiving_burst == 0) {
    off();
#if CONTIKIMAC_CONF_COMPOWER
    if(was_on && !radio_is_on) {
      compower_accumulate(&compower_idle_activity);
    }
#endif /* CONTIKIMAC_CONF_COMPOWER */
  }
}

/**
 * Send a probe packet.
 */
static void
send_probe(void)
{
  struct lpp_hdr *hdr;
  struct announcement_msg *adata;
  struct announcement *a;

  /* Set up the probe header. */
  packetbuf_clear();
  packetbuf_set_datalen(sizeof(struct lpp_hdr));
  hdr = packetbuf_dataptr();
  hdr->type = TYPE_PROBE;
  rimeaddr_copy(&hdr->sender, &rimeaddr_node_addr);
  rimeaddr_copy(&hdr->receiver, packetbuf_addr(PACKETBUF_ADDR_RECEIVER));


  /* Construct the announcements */
  adata = (struct announcement_msg *)((char *)hdr + sizeof(struct lpp_hdr));
  
  adata->num = 0;
  for(a = announcement_list(); a != NULL; a = a->next) {
    adata->data[adata->num].id = a->id;
    adata->data[adata->num].value = a->value;
    adata->num++;
  }

  packetbuf_set_datalen(sizeof(struct lpp_hdr) +
		      ANNOUNCEMENT_MSG_HEADERLEN +
		      sizeof(struct announcement_data) * adata->num);

  /*  PRINTF("Sending probe\n");*/

  /*  printf("probe\n");*/
  
  /* XXX should first check access to the medium (CCA - Clear Channel
     Assessment) and add LISTEN_TIME to off_time_adjustment if there
     is a packet in the air. */
  radio->send(packetbuf_hdrptr(), packetbuf_totlen());

  compower_accumulate(&compower_idle_activity);
}

/*---------------------------------------------------------------------------*/
static void
remove_queued_packet(void *item)
{
  struct queue_list_item *i = item;
  
  PRINTF("%d.%d: removing queued packet\n",
	 rimeaddr_node_addr.u8[0], rimeaddr_node_addr.u8[1]);

  
  ctimer_stop(&i->removal_timer);  
  queuebuf_free(i->packet);
  list_remove(pending_packets_list, i);
  list_remove(queued_packets_list, i);

  /* XXX potential optimization */
  if(list_length(queued_packets_list) == 0 && is_listening == 0) {
    turn_radio_off();
    compower_accumulate(&i->compower);
  }

  memb_free(&queued_packets_memb, i);
}

/*---------------------------------------------------------------------------*/
static void
remove_queued_packet(struct queue_list_item *i, uint8_t tx_ok)
{
  mac_callback_t sent;
  void *ptr;
  int num_transmissions = 0;
  int status;
  
  PRINTF("%d.%d: removing queued packet\n",
	 rimeaddr_node_addr.u8[0], rimeaddr_node_addr.u8[1]);


  queuebuf_to_packetbuf(i->packet);
  
  ctimer_stop(&i->removal_timer);
  queuebuf_free(i->packet);
  list_remove(pending_packets_list, i);
  list_remove(queued_packets_list, i);

  /* XXX potential optimization */
  if(list_length(queued_packets_list) == 0 && is_listening == 0) {
    turn_radio_off();
    compower_accumulate(&i->compower);
  }

  sent = i->sent_callback;
  ptr = i->sent_callback_ptr;
  num_transmissions = i->num_transmissions;
  memb_free(&queued_packets_memb, i);
  if(num_transmissions == 0 || tx_ok == 0) {
    status = MAC_TX_NOACK;
  } else {
    status = MAC_TX_OK;
  }
  mac_call_sent_callback(sent, ptr, status, num_transmissions);
}

//.........这里部分代码省略.........
          queuebuf_to_packetbuf(i->packet);

#if WITH_PENDING_BROADCAST
          if(i->broadcast_flag == BROADCAST_FLAG_NONE ||
             i->broadcast_flag == BROADCAST_FLAG_SEND) {
            i->num_transmissions = 1;
            NETSTACK_RADIO.send(queuebuf_dataptr(i->packet),
                                queuebuf_datalen(i->packet));
            sent = 1;
            PRINTF("%d.%d: got a probe from %d.%d, sent packet to %d.%d\n",
		   rimeaddr_node_addr.u8[0], rimeaddr_node_addr.u8[1],
                   hdr.sender.u8[0], hdr.sender.u8[1],
                   receiver->u8[0], receiver->u8[1]);
	      
          } else {
            PRINTF("%d.%d: got a probe from %d.%d, did not send packet\n",
                   rimeaddr_node_addr.u8[0], rimeaddr_node_addr.u8[1],
                   hdr.sender.u8[0], hdr.sender.u8[1]);
          }
#else /* WITH_PENDING_BROADCAST */
          i->num_transmissions = 1;
          NETSTACK_RADIO.send(queuebuf_dataptr(i->packet),
                               queuebuf_datalen(i->packet));
          PRINTF("%d.%d: got a probe from %d.%d, sent packet to %d.%d\n",
                 rimeaddr_node_addr.u8[0], rimeaddr_node_addr.u8[1],
                 hdr.sender.u8[0], hdr.sender.u8[1],
                 receiver->u8[0], receiver->u8[1]);
#endif /* WITH_PENDING_BROADCAST */

          /*          off();*/

          /* Attribute the energy spent on listening for the probe
             to this packet transmission. */
          compower_accumulate(&i->compower);
	    
          /* If the packet was not a broadcast packet, we dequeue it
             now. Broadcast packets should be transmitted to all
             neighbors, and are dequeued by the dutycycling function
             instead, after the appropriate time. */
          if(!rimeaddr_cmp(receiver, &rimeaddr_null)) {
            if(detect_ack()) {
              remove_queued_packet(i, 1);
            } else {
              remove_queued_packet(i, 0);
            }

#if WITH_PROBE_AFTER_TRANSMISSION
            /* Send a probe packet to catch any reply from the other node. */
            restart_dutycycle(PROBE_AFTER_TRANSMISSION_TIME);
#endif /* WITH_PROBE_AFTER_TRANSMISSION */

#if WITH_STREAMING
            if(is_streaming) {
              ctimer_set(&stream_probe_timer, STREAM_PROBE_TIME,
                         send_stream_probe, NULL);
            }
#endif /* WITH_STREAMING */
          }

          if(sent) {
            turn_radio_off();
          }

#if WITH_ACK_OPTIMIZATION
          if(packetbuf_attr(PACKETBUF_ATTR_RELIABLE) ||
             packetbuf_attr(PACKETBUF_ATTR_ERELIABLE)) {

/*---------------------------------------------------------------------------*/
static void
input_packet(void)
{
  static struct ctimer ct;
  if(!we_are_receiving_burst) {
    off();
  }

  /*  printf("cycle_start 0x%02x 0x%02x\n", cycle_start, cycle_start % CYCLE_TIME);*/

  if(packetbuf_totlen() > 0 && NETSTACK_FRAMER.parse() >= 0) {
    if(packetbuf_datalen() > 0 &&
       packetbuf_totlen() > 0 &&
       (linkaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                     &linkaddr_node_addr) ||
        packetbuf_holds_broadcast())) {
      /* This is a regular packet that is destined to us or to the
         broadcast address. */

      /* If FRAME_PENDING is set, we are receiving a packets in a burst */
      /* TODO To prevent denial-of-sleep attacks, the transceiver should
         be disabled upon receipt of an unauthentic frame. */
      we_are_receiving_burst = packetbuf_attr(PACKETBUF_ATTR_PENDING);
      if(we_are_receiving_burst) {
        on();
        /* Set a timer to turn the radio off in case we do not receive
	   a next packet */
        ctimer_set(&ct, INTER_PACKET_DEADLINE, recv_burst_off, NULL);
      } else {
        off();
        ctimer_stop(&ct);
      }

#if RDC_WITH_DUPLICATE_DETECTION
      /* Check for duplicate packet. */
      if(mac_sequence_is_duplicate()) {
        /* Drop the packet. */
        /*        printf("Drop duplicate ContikiMAC layer packet\n");*/
        return;
      }
      mac_sequence_register_seqno();
#endif /* RDC_WITH_DUPLICATE_DETECTION */

#if CONTIKIMAC_CONF_COMPOWER
      /* Accumulate the power consumption for the packet reception. */
      compower_accumulate(&current_packet);
      /* Convert the accumulated power consumption for the received
         packet to packet attributes so that the higher levels can
         keep track of the amount of energy spent on receiving the
         packet. */
      compower_attrconv(&current_packet);

      /* Clear the accumulated power consumption so that it is ready
         for the next packet. */
      compower_clear(&current_packet);
#endif /* CONTIKIMAC_CONF_COMPOWER */

      PRINTDEBUG("contikimac: data (%u)\n", packetbuf_datalen());
      NETSTACK_MAC.input();
      return;
    } else {
      PRINTDEBUG("contikimac: data not for us\n");
    }
  } else {
    PRINTF("contikimac: failed to parse (%u)\n", packetbuf_totlen());
  }
}

/*---------------------------------------------------------------------------*/
static void
input_packet(void)
{
  static struct ctimer ct;
  if(!we_are_receiving_burst) {
    off();
  }

  /*  printf("cycle_start 0x%02x 0x%02x\n", cycle_start, cycle_start % CYCLE_TIME);*/
#ifdef NETSTACK_DECRYPT
  NETSTACK_DECRYPT();
#endif /* NETSTACK_DECRYPT */

  if(packetbuf_totlen() > 0 && NETSTACK_FRAMER.parse() >= 0) {
#if WITH_CONTIKIMAC_HEADER
    struct hdr *chdr;
    chdr = packetbuf_dataptr();
    if(chdr->id != CONTIKIMAC_ID) {
      PRINTF("contikimac: failed to parse hdr (%u)\n", packetbuf_totlen());
      return;
    }
    packetbuf_hdrreduce(sizeof(struct hdr));
    packetbuf_set_datalen(chdr->len);
#endif /* WITH_CONTIKIMAC_HEADER */

    if(packetbuf_datalen() > 0 &&
       packetbuf_totlen() > 0 &&
       (rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                     &rimeaddr_node_addr) ||
        rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                     &rimeaddr_null))) {
      /* This is a regular packet that is destined to us or to the
         broadcast address. */
#if !RDC_CONF_HARDWARE_SEND_ACK
        if (rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER), &rimeaddr_node_addr))
        {
          we_are_acking = 1;
          /* need to send an ack */
          static uint8_t ackbuf[ACK_LEN] = { 0 };
          ackbuf[ACK_LEN - 1] = packetbuf_attr(PACKETBUF_ATTR_PACKET_ID);
          NETSTACK_RADIO.send(ackbuf, ACK_LEN);
          we_are_acking = 0;
        }
#endif
      /* If FRAME_PENDING is set, we are receiving a packets in a burst */
      we_are_receiving_burst = packetbuf_attr(PACKETBUF_ATTR_PENDING);
      if(we_are_receiving_burst) {
        on();
        /* Set a timer to turn the radio off in case we do not receive
	   a next packet */
        ctimer_set(&ct, INTER_PACKET_DEADLINE, recv_burst_off, NULL);
      } else {
        off();
        ctimer_stop(&ct);
      }

      /* Check for duplicate packet. */
      if(mac_sequence_is_duplicate()) {
        /* Drop the packet. */
        /*        printf("Drop duplicate ContikiMAC layer packet\n");*/
        return;
      }
      mac_sequence_register_seqno();

#if CONTIKIMAC_CONF_COMPOWER
      /* Accumulate the power consumption for the packet reception. */
      compower_accumulate(&current_packet);
      /* Convert the accumulated power consumption for the received
         packet to packet attributes so that the higher levels can
         keep track of the amount of energy spent on receiving the
         packet. */
      compower_attrconv(&current_packet);

      /* Clear the accumulated power consumption so that it is ready
         for the next packet. */
      compower_clear(&current_packet);
#endif /* CONTIKIMAC_CONF_COMPOWER */

      PRINTDEBUG("contikimac: data (%u)\n", packetbuf_datalen());
      NETSTACK_MAC.input();
      return;
    } else {
      PRINTDEBUG("contikimac: data not for us\n");
    }
  } else {
    PRINTF("contikimac: failed to parse (%u)\n", packetbuf_totlen());
  }
}

/*---------------------------------------------------------------------------*/
static void
powercycle_turn_radio_off(void)
{
#if CONTIKIMAC_CONF_COMPOWER
  uint8_t was_on = radio_is_on;
#endif /* CONTIKIMAC_CONF_COMPOWER */
  
#if RDC_CONF_HARDWARE_SEND_ACK
  if(we_are_sending == 0 && we_are_receiving_burst == 0) {
#else
  if(we_are_sending == 0 && we_are_receiving_burst == 0 && we_are_acking == 0) {
#endif
    off();
#if CONTIKIMAC_CONF_COMPOWER
    if(was_on && !radio_is_on) {
      compower_accumulate(&compower_idle_activity);
    }
#endif /* CONTIKIMAC_CONF_COMPOWER */
  }
}
/*---------------------------------------------------------------------------*/
static void
powercycle_turn_radio_on(void)
{
#if RDC_CONF_HARDWARE_SEND_ACK
  if(we_are_sending == 0 && we_are_receiving_burst == 0) {
#else
  if(we_are_sending == 0 && we_are_receiving_burst == 0 && we_are_acking == 0) {
#endif
    on();
  }
}
/*---------------------------------------------------------------------------*/
static char
powercycle(struct rtimer *t, void *ptr)
{
#if SYNC_CYCLE_STARTS
  static volatile rtimer_clock_t sync_cycle_start;
  static volatile uint8_t sync_cycle_phase;
#endif

  PT_BEGIN(&pt);

#if SYNC_CYCLE_STARTS
  sync_cycle_start = RTIMER_NOW();
#else
  cycle_start = RTIMER_NOW();
#endif

  while(1) {
    static uint8_t packet_seen;
    static rtimer_clock_t t0;
    static uint8_t count;

#if SYNC_CYCLE_STARTS
    /* Compute cycle start when RTIMER_ARCH_SECOND is not a multiple
       of CHANNEL_CHECK_RATE */
    if(sync_cycle_phase++ == NETSTACK_RDC_CHANNEL_CHECK_RATE) {
      sync_cycle_phase = 0;
      sync_cycle_start += RTIMER_ARCH_SECOND;
      cycle_start = sync_cycle_start;
    } else {
#if (RTIMER_ARCH_SECOND * NETSTACK_RDC_CHANNEL_CHECK_RATE) > 65535
      cycle_start = sync_cycle_start + ((unsigned long)(sync_cycle_phase*RTIMER_ARCH_SECOND))/NETSTACK_RDC_CHANNEL_CHECK_RATE;
#else
      cycle_start = sync_cycle_start + (sync_cycle_phase*RTIMER_ARCH_SECOND)/NETSTACK_RDC_CHANNEL_CHECK_RATE;
#endif
    }
#else
    cycle_start += CYCLE_TIME;
#endif

    packet_seen = 0;

    for(count = 0; count < CCA_COUNT_MAX; ++count) {
      t0 = RTIMER_NOW();
      if(we_are_sending == 0 && we_are_receiving_burst == 0) {
        powercycle_turn_radio_on();
        /* Check if a packet is seen in the air. If so, we keep the
             radio on for a while (LISTEN_TIME_AFTER_PACKET_DETECTED) to
             be able to receive the packet. We also continuously check
             the radio medium to make sure that we wasn't woken up by a
             false positive: a spurious radio interference that was not
             caused by an incoming packet. */
        if(NETSTACK_RADIO.channel_clear() == 0) {
          packet_seen = 1;
          break;
        }
        powercycle_turn_radio_off();
      }
      schedule_powercycle_fixed(t, RTIMER_NOW() + CCA_SLEEP_TIME);
      PT_YIELD(&pt);
    }

    if(packet_seen) {
      static rtimer_clock_t start;
      static uint8_t silence_periods, periods;
      start = RTIMER_NOW();

//.........这里部分代码省略.........

/*---------------------------------------------------------------------------*/
static void
input_packet(void)
{
  static struct ctimer ct;
  int duplicate = 0;

#if CONTIKIMAC_SEND_SW_ACK
  int original_datalen;
  uint8_t *original_dataptr;

  original_datalen = packetbuf_datalen();
  original_dataptr = packetbuf_dataptr();
#endif

  if(!we_are_receiving_burst) {
    off();
  }

  if(packetbuf_datalen() == ACK_LEN) {
    /* Ignore ack packets */
    PRINTF("ContikiMAC: ignored ack\n");
    return;
  }

  /*  printf("cycle_start 0x%02x 0x%02x\n", cycle_start, cycle_start % CYCLE_TIME);*/

  if(packetbuf_totlen() > 0 && NETSTACK_FRAMER.parse() >= 0) {
    if(packetbuf_datalen() > 0 &&
       packetbuf_totlen() > 0 &&
       (linkaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                     &linkaddr_node_addr) ||
        packetbuf_holds_broadcast())) {
      /* This is a regular packet that is destined to us or to the
         broadcast address. */

      /* If FRAME_PENDING is set, we are receiving a packets in a burst */
      we_are_receiving_burst = packetbuf_attr(PACKETBUF_ATTR_PENDING);
      if(we_are_receiving_burst) {
        on();
        /* Set a timer to turn the radio off in case we do not receive
	   a next packet */
        ctimer_set(&ct, INTER_PACKET_DEADLINE, recv_burst_off, NULL);
      } else {
        off();
        ctimer_stop(&ct);
      }

#if RDC_WITH_DUPLICATE_DETECTION
      /* Check for duplicate packet. */
      duplicate = mac_sequence_is_duplicate();
      if(duplicate) {
        /* Drop the packet. */
        PRINTF("contikimac: Drop duplicate\n");
      } else {
        mac_sequence_register_seqno();
      }
#endif /* RDC_WITH_DUPLICATE_DETECTION */

#if CONTIKIMAC_CONF_COMPOWER
      /* Accumulate the power consumption for the packet reception. */
      compower_accumulate(&current_packet);
      /* Convert the accumulated power consumption for the received
         packet to packet attributes so that the higher levels can
         keep track of the amount of energy spent on receiving the
         packet. */
      compower_attrconv(&current_packet);

      /* Clear the accumulated power consumption so that it is ready
         for the next packet. */
      compower_clear(&current_packet);
#endif /* CONTIKIMAC_CONF_COMPOWER */

      PRINTDEBUG("contikimac: data (%u)\n", packetbuf_datalen());

#if CONTIKIMAC_SEND_SW_ACK
      {
        frame802154_t info154;
        frame802154_parse(original_dataptr, original_datalen, &info154);
        if(info154.fcf.frame_type == FRAME802154_DATAFRAME &&
            info154.fcf.ack_required != 0 &&
            linkaddr_cmp((linkaddr_t *)&info154.dest_addr,
                &linkaddr_node_addr)) {
          uint8_t ackdata[ACK_LEN] = {0, 0, 0};

          we_are_sending = 1;
          ackdata[0] = FRAME802154_ACKFRAME;
          ackdata[1] = 0;
          ackdata[2] = info154.seq;
          NETSTACK_RADIO.send(ackdata, ACK_LEN);
          we_are_sending = 0;
        }
      }
#endif /* CONTIKIMAC_SEND_SW_ACK */

      if(!duplicate) {
        NETSTACK_MAC.input();
      }
      return;
    } else {
//.........这里部分代码省略.........

/*---------------------------------------------------------------------------*/
static void
input_packet(void)
{
  struct xmac_hdr *hdr;
  printf("input packet!\n");
  if(NETSTACK_FRAMER.parse() >= 0) {
    hdr = packetbuf_dataptr();

    if(hdr->dispatch != DISPATCH) {
      someone_is_sending = 0;
      if(rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                                     &rimeaddr_node_addr) ||
	 rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                      &rimeaddr_null)) {
	/* This is a regular packet that is destined to us or to the
	   broadcast address. */

	/* We have received the final packet, so we can go back to being
	   asleep. */
	off();

        /* Check for duplicate packet by comparing the sequence number
           of the incoming packet with the last few ones we saw. */
        {
          int i;
          for(i = 0; i < MAX_SEQNOS; ++i) {
            if(packetbuf_attr(PACKETBUF_ATTR_PACKET_ID) == received_seqnos[i].seqno &&
               rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_SENDER),
                            &received_seqnos[i].sender)) {
              /* Drop the packet. */
              return;
            }
          }
          for(i = MAX_SEQNOS - 1; i > 0; --i) {
            memcpy(&received_seqnos[i], &received_seqnos[i - 1],
                   sizeof(struct seqno));
          }
          received_seqnos[0].seqno = packetbuf_attr(PACKETBUF_ATTR_PACKET_ID);
          rimeaddr_copy(&received_seqnos[0].sender,
                        packetbuf_addr(PACKETBUF_ADDR_SENDER));
        }

#if XMAC_CONF_COMPOWER
	/* Accumulate the power consumption for the packet reception. */
	compower_accumulate(&current_packet);
	/* Convert the accumulated power consumption for the received
	   packet to packet attributes so that the higher levels can
	   keep track of the amount of energy spent on receiving the
	   packet. */
	compower_attrconv(&current_packet);

	/* Clear the accumulated power consumption so that it is ready
	   for the next packet. */
	compower_clear(&current_packet);
#endif /* XMAC_CONF_COMPOWER */

	waiting_for_packet = 0;

        PRINTDEBUG("xmac: data(%u)\n", packetbuf_datalen());
	NETSTACK_MAC.input();
        return;
      } else {
        PRINTDEBUG("xmac: data not for us\n");
      }

    } else if(hdr->type == TYPE_STROBE) {
      someone_is_sending = 2;

      if(rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                      &rimeaddr_node_addr)) {
	/* This is a strobe packet for us. */

	/* If the sender address is someone else, we should
	   acknowledge the strobe and wait for the packet. By using
	   the same address as both sender and receiver, we flag the
	   message is a strobe ack. */
        waiting_for_packet = 1;
#if 0
	hdr->type = TYPE_STROBE_ACK;
	packetbuf_set_addr(PACKETBUF_ADDR_RECEIVER,
			   packetbuf_addr(PACKETBUF_ADDR_SENDER));
	packetbuf_set_addr(PACKETBUF_ADDR_SENDER, &rimeaddr_node_addr);
	packetbuf_compact();
	if(NETSTACK_FRAMER.create() >= 0) {
	  /* We turn on the radio in anticipation of the incoming
	     packet. */
	  someone_is_sending = 1;
	  waiting_for_packet = 1;
	  on();
	  NETSTACK_RADIO.send(packetbuf_hdrptr(), packetbuf_totlen());
	  PRINTDEBUG("xmac: send strobe ack %u\n", packetbuf_totlen());
	} else {
	  PRINTF("xmac: failed to send strobe ack\n");
	}
#endif /* 0 */
      } else if(rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                             &rimeaddr_null)) {
	/* If the receiver address is null, the strobe is sent to
	   prepare for an incoming broadcast packet. If this is the
//.........这里部分代码省略.........

//.........这里部分代码省略.........
	  off();
	  wt = RTIMER_NOW();
	  while(RTIMER_CLOCK_LT(RTIMER_NOW(), wt + WAIT_TIME_BEFORE_STROBE_ACK));
#endif /* 0 */
#if RDC_CONF_HARDWARE_ACK
          if(ret == RADIO_TX_OK) {
            got_strobe_ack = 1;
          } else {
            off();
          }
#else
          if(detect_ack()) {
            got_strobe_ack = 1;
          } else {
            off();
          }
#endif /* RDC_CONF_HARDWARE_ACK */

        }
      }
    }
  }

#if WITH_ACK_OPTIMIZATION
  /* If we have received the strobe ACK, and we are sending a packet
     that will need an upper layer ACK (as signified by the
     PACKETBUF_ATTR_RELIABLE packet attribute), we keep the radio on. */
  if(got_strobe_ack && (packetbuf_attr(PACKETBUF_ATTR_RELIABLE) ||
			packetbuf_attr(PACKETBUF_ATTR_ERELIABLE) ||
			packetbuf_attr(PACKETBUF_ATTR_PACKET_TYPE) ==
			PACKETBUF_ATTR_PACKET_TYPE_STREAM)) {
    on(); /* Wait for ACK packet */
    waiting_for_packet = 1;
  } else {
    off();
  }
#endif /* WITH_ACK_OPTIMIZATION */

  /* restore the packet to send */
  queuebuf_to_packetbuf(packet);
  queuebuf_free(packet);

  /* Send the data packet. */
  if((is_broadcast || got_strobe_ack || is_streaming) && collisions == 0) {
    ret = NETSTACK_RADIO.send(packetbuf_hdrptr(), packetbuf_totlen());

    if(!is_broadcast) {
#if RDC_CONF_HARDWARE_ACK
      if(ret == RADIO_TX_OK) {
        got_ack = 1;
      }
#else
      if(detect_ack()) {
        got_ack = 1;
      }
#endif /* RDC_CONF_HARDWARE_ACK */
    }
  }
  off();

#if WITH_ENCOUNTER_OPTIMIZATION
  if(got_strobe_ack && !is_streaming) {
    register_encounter(packetbuf_addr(PACKETBUF_ADDR_RECEIVER), encounter_time);
  }
#endif /* WITH_ENCOUNTER_OPTIMIZATION */
  watchdog_start();

  PRINTF("xmac: send (strobes=%u,len=%u,%s), done\n", strobes,
	 packetbuf_totlen(), got_strobe_ack ? "ack" : "no ack");

#if XMAC_CONF_COMPOWER
  /* Accumulate the power consumption for the packet transmission. */
  compower_accumulate(&current_packet);

  /* Convert the accumulated power consumption for the transmitted
     packet to packet attributes so that the higher levels can keep
     track of the amount of energy spent on transmitting the
     packet. */
  compower_attrconv(&current_packet);

  /* Clear the accumulated power consumption so that it is ready for
     the next packet. */
  compower_clear(&current_packet);
#endif /* XMAC_CONF_COMPOWER */

  we_are_sending = 0;

  LEDS_OFF(LEDS_BLUE);
  if(collisions == 0) {
    if(is_broadcast == 0 && got_ack == 0) {
      return MAC_TX_NOACK;
    } else {
      return MAC_TX_OK;
    }
  } else {
    someone_is_sending++;
    return MAC_TX_COLLISION;
  }

}

static char
powercycle(struct rtimer *t, void *ptr)
{
  PT_BEGIN(&pt);

  while(1) {
    static uint8_t packet_seen;
    static rtimer_clock_t t0;
    static uint8_t count;

    cycle_start = RTIMER_NOW();

    if(WITH_STREAMING && is_streaming) {
#if NURTIMER
      if(!RTIMER_CLOCK_LT(cycle_start, RTIMER_NOW(), stream_until))
#else
        if(!RTIMER_CLOCK_LT(RTIMER_NOW(), stream_until))
#endif
          {
            is_streaming = 0;
            rimeaddr_copy(&is_streaming_to, &rimeaddr_null);
            rimeaddr_copy(&is_streaming_to_too, &rimeaddr_null);
          }
    }

    packet_seen = 0;

    do {
      for(count = 0; count < CCA_COUNT_MAX; ++count) {
        t0 = RTIMER_NOW();
        if(we_are_sending == 0) {
          powercycle_turn_radio_on();
#if 0
#if NURTIMER
          while(RTIMER_CLOCK_LT(t0, RTIMER_NOW(), t0 + CCA_CHECK_TIME));
#else
          while(RTIMER_CLOCK_LT(RTIMER_NOW(), t0 + CCA_CHECK_TIME));
#endif
#endif /* 0 */
          /* Check if a packet is seen in the air. If so, we keep the
             radio on for a while (LISTEN_TIME_AFTER_PACKET_DETECTED) to
             be able to receive the packet. We also continuously check
             the radio medium to make sure that we wasn't woken up by a
             false positive: a spurious radio interference that was not
             caused by an incoming packet. */
          if(NETSTACK_RADIO.channel_clear() == 0) {
            packet_seen = 1;
            break;
          }
          powercycle_turn_radio_off();
        }
        schedule_powercycle_fixed(t, RTIMER_NOW() + CCA_SLEEP_TIME);
        /*        COOJA_DEBUG_STR("yield\n");*/
        PT_YIELD(&pt);
      }
      
      if(packet_seen) {
        static rtimer_clock_t start;
        static uint8_t silence_periods, periods;
        start = RTIMER_NOW();
        
        periods = silence_periods = 0;
        while(we_are_sending == 0 && radio_is_on &&
              RTIMER_CLOCK_LT(RTIMER_NOW(), (start + LISTEN_TIME_AFTER_PACKET_DETECTED))) {
          
          /* Check for a number of consecutive periods of
             non-activity. If we see two such periods, we turn the
             radio off. Also, if a packet has been successfully
             received (as indicated by the
             NETSTACK_RADIO.pending_packet() function), we stop
             snooping. */
          if(NETSTACK_RADIO.channel_clear()) {
            ++silence_periods;
          } else {
            silence_periods = 0;
          }
          
          ++periods;
        
          if(NETSTACK_RADIO.receiving_packet()) {
            silence_periods = 0;
          }
          if(silence_periods > MAX_SILENCE_PERIODS) {
            LEDS_ON(LEDS_RED);
            powercycle_turn_radio_off();
#if CONTIKIMAC_CONF_COMPOWER
            compower_accumulate(&compower_idle_activity);
#endif /* CONTIKIMAC_CONF_COMPOWER */
            LEDS_OFF(LEDS_RED);
            break;
          }
#if 1
          if(periods > MAX_NONACTIVITY_PERIODIC && !(NETSTACK_RADIO.receiving_packet() ||
                                                     NETSTACK_RADIO.pending_packet())) {
            LEDS_ON(LEDS_GREEN);
            powercycle_turn_radio_off();
#if CONTIKIMAC_CONF_COMPOWER
            compower_accumulate(&compower_idle_activity);
#endif /* CONTIKIMAC_CONF_COMPOWER */
            
//.........这里部分代码省略.........

//.........这里部分代码省略.........
      int ret;

      txtime = RTIMER_NOW();
      ret = NETSTACK_RADIO.transmit(transmit_len);

#if RDC_CONF_HARDWARE_ACK
     /* For radios that block in the transmit routine and detect the
	ACK in hardware */
      if(ret == RADIO_TX_OK) {
        if(!is_broadcast) {
          got_strobe_ack = 1;
          encounter_time = txtime;
          break;
        }
      } else if (ret == RADIO_TX_NOACK) {
      } else if (ret == RADIO_TX_COLLISION) {
          PRINTF("contikimac: collisions while sending\n");
          collisions++;
      }
      wt = RTIMER_NOW();
      while(RTIMER_CLOCK_LT(RTIMER_NOW(), wt + INTER_PACKET_INTERVAL)) { }
#else /* RDC_CONF_HARDWARE_ACK */
     /* Wait for the ACK packet */
      wt = RTIMER_NOW();
      while(RTIMER_CLOCK_LT(RTIMER_NOW(), wt + INTER_PACKET_INTERVAL)) { }

      if(!is_broadcast && (NETSTACK_RADIO.receiving_packet() ||
                           NETSTACK_RADIO.pending_packet() ||
                           NETSTACK_RADIO.channel_clear() == 0)) {
        uint8_t ackbuf[ACK_LEN];
        wt = RTIMER_NOW();
        while(RTIMER_CLOCK_LT(RTIMER_NOW(), wt + AFTER_ACK_DETECTECT_WAIT_TIME)) { }

        len = NETSTACK_RADIO.read(ackbuf, ACK_LEN);
        if(len == ACK_LEN && seqno == ackbuf[ACK_LEN - 1]) {
          got_strobe_ack = 1;
          encounter_time = txtime;
          break;
        } else {
          PRINTF("contikimac: collisions while sending\n");
          collisions++;
        }
      }
#endif /* RDC_CONF_HARDWARE_ACK */
    }
  }

  off();

  PRINTF("contikimac: send (strobes=%u, len=%u, %s, %s), done\n", strobes,
         packetbuf_totlen(),
         got_strobe_ack ? "ack" : "no ack",
         collisions ? "collision" : "no collision");

#if CONTIKIMAC_CONF_COMPOWER
  /* Accumulate the power consumption for the packet transmission. */
  compower_accumulate(&current_packet);

  /* Convert the accumulated power consumption for the transmitted
     packet to packet attributes so that the higher levels can keep
     track of the amount of energy spent on transmitting the
     packet. */
  compower_attrconv(&current_packet);

  /* Clear the accumulated power consumption so that it is ready for
     the next packet. */
  compower_clear(&current_packet);
#endif /* CONTIKIMAC_CONF_COMPOWER */

  contikimac_is_on = contikimac_was_on;
  we_are_sending = 0;

  /* Determine the return value that we will return from the
     function. We must pass this value to the phase module before we
     return from the function.  */
  if(collisions > 0) {
    ret = MAC_TX_COLLISION;
  } else if(!is_broadcast && !got_strobe_ack) {
    ret = MAC_TX_NOACK;
  } else {
    ret = MAC_TX_OK;
  }

#if WITH_PHASE_OPTIMIZATION
  if(is_known_receiver && got_strobe_ack) {
    PRINTF("no miss %d wake-ups %d\n",
	   packetbuf_addr(PACKETBUF_ADDR_RECEIVER)->u8[0],
           strobes);
  }

  if(!is_broadcast) {
    if(collisions == 0 && is_receiver_awake == 0) {
      phase_update(&phase_list, packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
		   encounter_time, ret);
    }
  }
#endif /* WITH_PHASE_OPTIMIZATION */

  return ret;
}

/**
 * Duty cycle the radio and send probes. This function is called
 * repeatedly by a ctimer. The function restart_dutycycle() is used to
 * (re)start the duty cycling.
 */
static int
dutycycle(void *ptr)
{
  struct ctimer *t = ptr;
	
  PT_BEGIN(&dutycycle_pt);

  while(1) {

#if WITH_PENDING_BROADCAST
    {
	/* Before sending the probe, we mark all broadcast packets in
	   our output queue to be pending. This means that they are
	   ready to be sent, once we know that no neighbor is
	   currently broadcasting. */
      for(p = list_head(queued_packets_list); p != NULL; p = list_item_next(p)) {
	  if(p->broadcast_flag == BROADCAST_FLAG_WAITING) {
	    PRINTF("wait -> pending\n");
	    set_broadcast_flag(p, BROADCAST_FLAG_PENDING);
	  }
	}
      }
#endif /* WITH_PENDING_BROADCAST */
    
    /* Turn on the radio for sending a probe packet and 
       anticipating a data packet from a neighbor. */
    turn_radio_on();

    /* Send a probe packet. */
    send_probe();

    /* Set a timer so that we keep the radio on for LISTEN_TIME. */
    ctimer_set(t, LISTEN_TIME, (void (*)(void *))dutycycle, t);
    PT_YIELD(&dutycycle_pt);

#if WITH_PENDING_BROADCAST
    {
      struct queue_list_item *p;
      /* Go through the list of packets we are waiting to send, and
	 check if there are any pending broadcasts in the list. If
	 there are pending broadcasts, and we did not receive any
	 broadcast packets from a neighbor in response to our probe,
	 we mark the broadcasts as being ready to send. */
      for(p = list_head(queued_packets_list); p != NULL; p = list_item_next(p)) {
	if(p->broadcast_flag == BROADCAST_FLAG_PENDING) {
	  PRINTF("pending -> send\n");
	  set_broadcast_flag(p, BROADCAST_FLAG_SEND);
	  turn_radio_on();
	}
      }
    }
#endif /* WITH_PENDING_BROADCAST */

    /* If we have no packets to send (indicated by the list length of
       queued_packets_list being zero), we should turn the radio
       off. Othersize, we keep the radio on. */
    if(num_packets_to_send() == 0) {
      
      /* If we are not listening for announcements, we turn the radio
	 off and wait until we send the next probe. */
      if(is_listening == 0) {
        int current_off_time;
        if(!NETSTACK_RADIO.receiving_packet()) {
          turn_radio_off();
          compower_accumulate(&compower_idle_activity);
        }
        current_off_time = off_time - off_time_adjustment;
        if(current_off_time < LISTEN_TIME * 2) {
          current_off_time = LISTEN_TIME * 2;
        }
        off_time_adjustment = 0;
	ctimer_set(t, current_off_time, (void (*)(void *))dutycycle, t);
	PT_YIELD(&dutycycle_pt);

#if WITH_ADAPTIVE_OFF_TIME
	off_time += LOWEST_OFF_TIME;
	if(off_time > OFF_TIME) {
	  off_time = OFF_TIME;
	}
#endif /* WITH_ADAPTIVE_OFF_TIME */

      } else {
	/* We are listening for annonucements, so we count down the
	   listen time, and keep the radio on. */
	is_listening--;
	ctimer_set(t, OFF_TIME, (void (*)(void *))dutycycle, t);
	PT_YIELD(&dutycycle_pt);
      }
    } else {
      /* We had pending packets to send, so we do not turn the radio off. */

      ctimer_set(t, off_time, (void (*)(void *))dutycycle, t);
      PT_YIELD(&dutycycle_pt);
    }
  }
//.........这里部分代码省略.........

//.........这里部分代码省略.........
        wt = RTIMER_NOW();
#if NURTIMER
        while(RTIMER_CLOCK_LT(wt, RTIMER_NOW(), wt + AFTER_ACK_DETECTECT_WAIT_TIME));
#else
        while(RTIMER_CLOCK_LT(RTIMER_NOW(), wt + AFTER_ACK_DETECTECT_WAIT_TIME)) { }
#endif
        len = NETSTACK_RADIO.read(ackbuf, ACK_LEN);
        if(len == ACK_LEN) {
          got_strobe_ack = 1;
          //          encounter_time = last_transmission_time;
          encounter_time = now;
          break;
        } else {
          PRINTF("contikimac: collisions while sending\n");
          collisions++;
        }
      }
      last_transmission_time = now;
      first_transmission = 0;
    }
  }

  if(WITH_ACK_OPTIMIZATION) {
    /* If we have received the strobe ACK, and we are sending a packet
       that will need an upper layer ACK (as signified by the
       PACKETBUF_ATTR_RELIABLE packet attribute), we keep the radio on. */
    if(got_strobe_ack && is_reliable) {
      on();                       /* Wait for ACK packet */
    } else {
      off();
    }
  } else {
    off();
  }

  PRINTF("contikimac: send (strobes=%u, len=%u, %s, %s), done\n", strobes,
         packetbuf_totlen(),
         got_strobe_ack ? "ack" : "no ack",
         collisions ? "collision" : "no collision");

#if CONTIKIMAC_CONF_COMPOWER
  /* Accumulate the power consumption for the packet transmission. */
  compower_accumulate(&current_packet);

  /* Convert the accumulated power consumption for the transmitted
     packet to packet attributes so that the higher levels can keep
     track of the amount of energy spent on transmitting the
     packet. */
  compower_attrconv(&current_packet);

  /* Clear the accumulated power consumption so that it is ready for
     the next packet. */
  compower_clear(&current_packet);
#endif /* CONTIKIMAC_CONF_COMPOWER */

  we_are_sending = 0;

  /* Determine the return value that we will return from the
     function. We must pass this value to the phase module before we
     return from the function.  */
  if(collisions > 0) {
    ret = MAC_TX_COLLISION;
  } else if(!is_broadcast && !got_strobe_ack) {
    ret = MAC_TX_NOACK;
  } else {
    ret = MAC_TX_OK;
  }

#if WITH_PHASE_OPTIMIZATION
  /*  if(!first_transmission)*/ {

    /*    COOJA_DEBUG_PRINTF("first phase 0x%02x\n", encounter_time % CYCLE_TIME);*/
    
    if(WITH_ACK_OPTIMIZATION) {
      if(collisions == 0 && packetbuf_attr(PACKETBUF_ATTR_PACKET_TYPE) !=
         PACKETBUF_ATTR_PACKET_TYPE_ACK && is_streaming == 0) {
        phase_update(&phase_list, packetbuf_addr(PACKETBUF_ADDR_RECEIVER), encounter_time,
                     ret);
      }
    } else {
      if(collisions == 0 && is_streaming == 0) {
        phase_update(&phase_list, packetbuf_addr(PACKETBUF_ADDR_RECEIVER), encounter_time,
                     ret);
      }
    }
  }
#endif /* WITH_PHASE_OPTIMIZATION */

  return ret;
}
/*---------------------------------------------------------------------------*/
static void
qsend_packet(mac_callback_t sent, void *ptr)
{
  int ret = send_packet(sent, ptr);
  if(ret != MAC_TX_DEFERRED) {
    //    printf("contikimac qsend_packet %p\n", ptr);
    mac_call_sent_callback(sent, ptr, ret, 1);
  }
}