hostchan.c

这个是LINUX下的GDB调度工具的源码

    }
  }
  else if (msg_home < (unsigned char) (OppoSeq+1)){
    /* already received this message */
#ifdef RET_DEBUG
    printf("sequence numbers low\n");
#endif   
    return adp_seq_low;
  }
  else {  /* we've missed something */
#ifdef RET_DEBUG
    printf("sequence numbers high\n");
#endif   
    return adp_seq_high;
  }
}

static unsigned long tv_diff(const struct timeval *time_now, 
                             const struct timeval *time_was)
{
    return (  ((time_now->tv_sec * 1000000) + time_now->tv_usec)
            - ((time_was->tv_sec * 1000000) + time_was->tv_usec) );
}

#if !defined(__unix) && !defined(__CYGWIN__)
static void gettimeofday( struct timeval *time_now, void *dummy )
{
    time_t t = clock();
    UNUSED(dummy);
    time_now->tv_sec = t/CLOCKS_PER_SEC;
    time_now->tv_usec = (t%CLOCKS_PER_SEC)*(1000000/CLOCKS_PER_SEC);
}
#endif

static AdpErrs pacemaker(void)
{
  Packet *packet;

  packet = DevSW_AllocatePacket(CF_DATA_BYTE_POS);
  if (packet == NULL) {
    printf("ERROR: could not allocate a packet in pacemaker()\n");
    return adp_malloc_failure;
  }
  packet->pk_buffer[CF_CHANNEL_BYTE_POS] = CI_PRIVATE;
  packet->pk_buffer[CF_HOME_SEQ_BYTE_POS] = HomeSeq;
  packet->pk_buffer[CF_OPPO_SEQ_BYTE_POS] = OppoSeq;
  packet->pk_buffer[CF_FLAGS_BYTE_POS] = CF_RELIABLE | CF_HEARTBEAT;
  packet->pk_length = CF_DATA_BYTE_POS;
  return DevSW_Write(deviceToUse, packet, DC_DBUG);
}  

#ifdef FAKE_BAD_LINE_RX
static AdpErrs fake_bad_line_rx( const Packet *const packet, AdpErrs adp_err )
{
    static unsigned int bl_num = 0;

    if (     (packet != NULL)
          && (bl_num++ >= 20 )
          && ((bl_num % FAKE_BAD_LINE_RX) == 0))
    {
        printf("DEBUG: faking a bad packet\n");
        return adp_bad_packet;
    }
    return adp_err;
}
#endif /* def FAKE_BAD_LINE_RX */

#ifdef FAKE_BAD_LINE_TX
static unsigned char tmp_ch;

static void fake_bad_line_tx( void )
{
    static unsigned int bl_num = 0;

    /* give the thing a chance to boot then try corrupting stuff */
    if ( (bl_num++ >= 20) && ((bl_num % FAKE_BAD_LINE_TX) == 0)) 
    {
        printf("DEBUG: faking a bad packet for tx\n");
        tmp_ch = writeQueueSend->pk_buffer[CF_FLAGS_BYTE_POS];
        writeQueueSend->pk_buffer[CF_FLAGS_BYTE_POS] = 77;
    }
}

static void unfake_bad_line_tx( void )
{
    static unsigned int bl_num = 0;

    /*
     * must reset the packet so that its not corrupted when we
     *  resend it 
     */   
    if ( (bl_num >= 20) && ((bl_num % FAKE_BAD_LINE_TX) != 0))
    {
        writeQueueSend->pk_buffer[CF_FLAGS_BYTE_POS] = tmp_ch;
    }
}
#endif /* def FAKE_BAD_LINE_TX */

/*
 * NOTE: we are assuming that a resolution of microseconds will
 * be good enough for the purporses of the heartbeat.  If this proves
 * not to be the case then we may need a rethink, possibly using
 * [get,set]itimer
 */
static struct timeval time_now;
static struct timeval time_lastalive;

static void async_process_dbug_read( const AsyncMode mode,
                                     bool *const finished  )
{
    Packet *packet;
    unsigned int msg_home, msg_oppo;
    AdpErrs adp_err;

    adp_err = DevSW_Read(deviceToUse, DC_DBUG, &packet,
                         mode == async_block_on_read    );

#ifdef FAKE_BAD_LINE_RX
    adp_err = fake_bad_line_rx( packet, adp_err );
#endif

    if (adp_err == adp_bad_packet) {
        /* We got a bad packet, ask for a resend, send a resend message */
#ifdef DEBUG
        printf("received a bad packet\n");
#endif
        send_resend_msg(DC_DBUG);
    }
    else if (packet != NULL)
    {
        /* update the heartbeat clock */
        gettimeofday(&time_lastalive, NULL);

            /*
             * we got a live one here - were we waiting for it?
             */
        if (mode == async_block_on_read)
           /* not any more */
           *finished = TRUE;
#ifdef RETRANS

        if (packet->pk_length < CF_DATA_BYTE_POS) {
            /* we've got a packet with no header information! */
            printf("ERROR: packet with no transport header\n");
            send_resend_msg(DC_DBUG);
        }
        else {
#ifdef RET_DEBUG
            unsigned int c;
#endif
            /*
             * TODO: Check to see if its acknowledgeing anything, remove
             * those packets it is from the queue.  If its a retrans add the
             * packets to the queue
             */
            msg_home = packet->pk_buffer[CF_HOME_SEQ_BYTE_POS];
            msg_oppo = packet->pk_buffer[CF_OPPO_SEQ_BYTE_POS];
#ifdef RET_DEBUG
            printf("msg seq numbers are hseq 0x%x oseq 0x%x\n",
                   msg_home, msg_oppo);
            for (c=0;c<packet->pk_length;c++)
               printf("%02.2x", packet->pk_buffer[c]);
            printf("\n");
#endif
            /* now was it a resend request? */
            if ((packet->pk_buffer[CF_FLAGS_BYTE_POS]) 
                & CF_RESEND) {
                /* we've been asked for a resend so we had better resend */
                /*
                 * I don't think we can use a resend as acknowledgement for
                 * anything so lets not do this for the moment
                 * check_seq(msg_home, msg_oppo);
                 */
#ifdef RET_DEBUG
                printf("received a resend request\n");
#endif
                if (HomeSeq != msg_oppo) {
                    int found = FALSE;
                    /* need to resend from msg_oppo +1 upwards */
                    DevSW_FreePacket(packet);
                    resending = TRUE;
                    /* find the correct packet to resend from */
                    packet = writeQueueRoot;
                    while (((packet->pk_next) != NULL) && !found) {
                        if ((packet->pk_buffer[CF_OPPO_SEQ_BYTE_POS])
                            != msg_oppo+1) {
                            resend_pkt = packet;
                            found = TRUE;
                        }
                        packet = packet->pk_next;
                    }
                    if (!found) {
                        panic("trying to resend non-existent packets\n");
                    }
                }
                else if (OppoSeq != msg_home) {
                    /* 
                     * send a resend request telling the target where we think
                     * the world is at 
                     */
                    DevSW_FreePacket(packet);
                    send_resend_msg(DC_DBUG);
                }
            }
            else {
                /* not a resend request, lets check the sequence numbers */
                
                if ((packet->pk_buffer[CF_CHANNEL_BYTE_POS] != CI_HBOOT) &&
                    (packet->pk_buffer[CF_CHANNEL_BYTE_POS] != CI_TBOOT)) {
                    adp_err = check_seq(msg_home, msg_oppo);
                    if (adp_err == adp_seq_low) {
                        /* we have already received this packet so discard */
                        DevSW_FreePacket(packet);
                    }
                    else if (adp_err == adp_seq_high) {
                        /*
                         * we must have missed a packet somewhere, discard this 
                         * packet and tell the target where we are
                         */
                        DevSW_FreePacket(packet);
                        send_resend_msg(DC_DBUG);
                    }
                    else
                       /*
                        * now pass the packet to whoever is waiting for it
                        */
                       FireCallback(packet);
                }
                else
                   FireCallback(packet);
            }
        }
#else
        /*
             * now pass the packet to whoever is waiting for it
             */
        FireCallback(packet);
#endif
    }
}

static void async_process_appl_read(void)
{
    Packet *packet;
    AdpErrs adp_err;

    /* see if there is anything for the DC_APPL channel */
    adp_err = DevSW_Read(deviceToUse, DC_APPL, &packet, FALSE);

    if (adp_err == adp_ok && packet != NULL)
    {
        /* got an application packet on a shared device */

#ifdef DEBUG
        printf("GOT DC_APPL PACKET: len %d\nData: ", packet->pk_length);
        {
            unsigned int c;
            for ( c = 0; c < packet->pk_length; ++c )
               printf( "%02X ", packet->pk_buffer[c] );
        }
        printf("\n");
#endif

        if (dc_appl_handler != NULL)
        {
            dc_appl_handler( deviceToUse, packet );
        }
        else
        {
            /* for now, just free it!! */
#ifdef DEBUG
            printf("no handler - dropping DC_APPL packet\n");
#endif
            DevSW_FreePacket( packet );
        }
    }
}

static void async_process_write( const AsyncMode mode,
                                 bool *const finished  )
{
    Packet *packet;

#ifdef DEBUG
    static unsigned int num_written = 0;
#endif

    /*
     * NOTE: here we rely in the fact that any packet in the writeQueueSend
     * section of the queue will need its sequence number setting up while
     * and packet in the writeQueueRoot section will have its sequence
     * numbers set up from when it was first sent so we can easily look
     * up the packet numbers when(if) we want to resend the packet.
     */

#ifdef DEBUG
    if (writeQueueSend!=NULL)
       printf("written 0x%x\n",num_written += writeQueueSend->pk_length);
#endif
    /*
     * give the switcher a chance to complete any partial writes
     */
    if (DevSW_FlushPendingWrite(deviceToUse) == adp_write_busy)
    {
        /* no point trying a new write */
        return;
    }
      
    /*
     * now see whether there is anything to write
     */
    packet = NULL;
    if (resending) {
        packet = resend_pkt;
#ifdef RET_DEBUG
        printf("resending hseq 0x%x oseq 0x%x\n", 
               packet->pk_buffer[CF_HOME_SEQ_BYTE_POS],
               packet->pk_buffer[CF_OPPO_SEQ_BYTE_POS]);
#endif
    }
    else if (writeQueueSend != NULL) {
#ifdef RETRANS
        /* set up the sequence number on the packet */
        packet = writeQueueSend;
        HomeSeq++;
        (writeQueueSend->pk_buffer[CF_OPPO_SEQ_BYTE_POS])
            = OppoSeq;
        (writeQueueSend->pk_buffer[CF_HOME_SEQ_BYTE_POS])
            = HomeSeq;
        (writeQueueSend->pk_buffer[CF_FLAGS_BYTE_POS])
            = CF_RELIABLE;
# ifdef RET_DEBUG
        printf("sending packet with hseq 0x%x oseq 0x%x\n",
               writeQueueSend->pk_buffer[CF_HOME_SEQ_BYTE_POS],
               writeQueueSend->pk_buffer[CF_OPPO_SEQ_BYTE_POS]);
# endif
#endif /* RETRANS */
    }

    if (packet != NULL) {
        AdpErrs dev_err;

#ifdef FAKE_BAD_LINE_TX
        fake_bad_line_tx();
#endif

        dev_err = DevSW_Write(deviceToUse, packet, DC_DBUG);
        if (dev_err == adp_ok) {
#ifdef RETRANS
            if (resending) {
                /* check to see if we've recovered yet */
                if ((packet->pk_next) == NULL){
# ifdef RET_DEBUG
                    printf("we have recovered\n");
# endif
                    resending = FALSE;
                }
                else {
                    resend_pkt = resend_pkt->pk_next;
                }
            }
            else {
                /* 
                 * move the packet we just sent from the send queue to the root
                 */
                Packet *tmp_pkt, *tmp;

# ifdef FAKE_BAD_LINE_TX
                unfake_bad_line_tx();
# endif

                tmp_pkt = writeQueueSend;
                writeQueueSend = writeQueueSend->pk_next;
                tmp_pkt->pk_next = NULL;
                if (writeQueueRoot == NULL)
                   writeQueueRoot = tmp_pkt;
                else {
                    tmp = writeQueueRoot;
                    while (tmp->pk_next != NULL) {
                        tmp = tmp->pk_next;
                    }
                    tmp->pk_next = tmp_pkt;
                }
            }
#else  /* not RETRANS */
            /*
             * switcher has taken the write, so remove it from the
             * queue, and free its resources
             */
            DevSW_FreePacket(Adp_removeFromQueue(&writeQueueSend));
#endif /* if RETRANS ... else ... */

            if (mode == async_block_on_write)
               *finished = DevSW_WriteFinished(deviceToUse);

        } /* endif write ok */
    }
    else /* packet == NULL */
    {
        if (mode == async_block_on_write)
           *finished = DevSW_WriteFinished(deviceToUse);
    }
}

static void async_process_heartbeat( void )
{
    /* check to see whether we need to send a heartbeat */
    gettimeofday(&time_now, NULL);

    if (tv_diff(&time_now, &time_lastalive) >= HEARTRATE)
    {
        /*
         * if we've not booted then don't do send a heartrate the link
         * must be reliable enough for us to boot without any clever stuff,
         * if we can't do this then theres little chance of the link staying
         * together even with the resends etc
         */
        if (heartbeat_enabled) {
            gettimeofday(&time_lastalive, NULL);
            pacemaker();
        }
    }
}

static void async_process_callbacks( void )
{
    /* call any registered asynchronous callbacks */
    unsigned int i;
    for ( i = 0; i < num_async_callbacks; ++i )
       async_callbacks[i]( deviceToUse, &time_now );
}

void Adp_AsynchronousProcessing(const AsyncMode mode)
{
    bool finished = FALSE;
#ifdef DEBUG
    unsigned int wc = 0, dc = 0, ac = 0, hc = 0;
# define INC_COUNT(x) ((x)++)
#else
# define INC_COUNT(x)
#endif

    if ((time_lastalive.tv_sec == 0) && (time_lastalive.tv_usec == 0)) {
      /* first time through, needs initing */
      gettimeofday(&time_lastalive, NULL);
    }

    /* main loop */
    do
    {
        async_process_write( mode, &finished );
        INC_COUNT(wc);

        if ( ! finished && mode != async_block_on_write )
        {
            async_process_dbug_read( mode, &finished );
            INC_COUNT(dc);
        }

        if ( ! finished && mode != async_block_on_write )
        {
           async_process_appl_read();
           INC_COUNT(ac);
        }

        if ( ! finished )
        {
          if (heartbeat_configured)
            async_process_heartbeat();
          async_process_callbacks();
          INC_COUNT(hc);
        }

    } while (!finished && mode != async_block_on_nothing);

#ifdef DEBUG
    if ( mode != async_block_on_nothing )
       printf( "Async: %s - w %d, d %d, a %d, h %d\n",
               mode == async_block_on_write ? "blk_write" : "blk_read",
               wc, dc, ac, hc );
#endif
}

/*
 * install a handler for DC_APPL packets (can be NULL), returning old one.
 */
DC_Appl_Handler Adp_Install_DC_Appl_Handler(const DC_Appl_Handler handler)
{
    DC_Appl_Handler old_handler = dc_appl_handler;

#ifdef DEBUG
    printf( "Installing DC_APPL handler %x (old %x)\n", handler, old_handler );
#endif

    dc_appl_handler = handler;
    return old_handler;
}


/*
 * add an asynchronous processing callback to the list
 * TRUE == okay, FALSE == no more async processing slots
 */
bool Adp_Install_Async_Callback( const Adp_Async_Callback callback_proc )
{
    if ( num_async_callbacks < MAX_ASYNC_CALLBACKS && callback_proc != NULL )
    {
        async_callbacks[num_async_callbacks] = callback_proc;
        ++num_async_callbacks;
        return TRUE;
    }
    else
       return FALSE;
}


/*
 * delay for a given period (in microseconds)
 */
void Adp_delay(unsigned int period)
{
    struct timeval tv;

#ifdef DEBUG
    printf("delaying for %d microseconds\n", period);
#endif
    tv.tv_sec = (period / 1000000);
    tv.tv_usec = (period % 1000000);

    (void)select(0, NULL, NULL, NULL, &tv);
}

/* EOF hostchan.c */