[ace-users] Clarification about C++Npv1 example about mb_aligned message block, thanks!

[Douglas C. Schmidt]

Hi,

>In Chap 4.4, Logging_Handler::recv_log_record, line 27:
>27     payload->size (length + 8);
>
>Here I think it should be:
>27     payload->size(length + 8 +ACE_CDR::MAX_ALIGNMENT);
>
> >Because on line 12, it calls ACE_CDR::mb_align (payload); which may
> >cause wr_ptr_
> >is 8 before writing something to it.
> >
> >Thanks!

As per input from Steve Huston, this code changed quite some time back -
it's correct in the 3rd printing, July 2004:

 1 int Logging_Handler::recv_log_record (ACE_Message_Block *&mblk)
 2 {
 3   ACE_INET_Addr peer_addr;
 4   logging_peer_.get_remote_addr (peer_addr);
 5   mblk = new ACE_Message_Block (MAXHOSTNAMELEN + 1);
 6   peer_addr.get_host_name (mblk->wr_ptr (), MAXHOSTNAMELEN);
 7   mblk->wr_ptr (strlen (mblk->wr_ptr ()) + 1); // Go past name.
 8
 9   ACE_Message_Block *payload =
10     new ACE_Message_Block (ACE_DEFAULT_CDR_BUFSIZE);
11   // Align Message Block for a CDR stream.
12   ACE_CDR::mb_align (payload);
13
14   if (logging_peer_.recv_n (payload->wr_ptr (), 8) == 8) {
15     payload->wr_ptr (8);     // Reflect addition of 8 bytes.
16
17     ACE_InputCDR cdr (payload);
18
19     ACE_CDR::Boolean byte_order;
20     // Use helper method to disambiguate booleans from chars.
21     cdr >> ACE_InputCDR::to_boolean (byte_order);
22     cdr.reset_byte_order (byte_order);
23 
24     ACE_CDR::ULong length;
25     cdr >> length;
26
27     ACE_CDR::grow
28       (payload, 8 + ACE_CDR::MAX_ALIGNMENT + length);
29     if (logging_peer_.recv_n (payload->wr_ptr(), length) > 0) {
30       payload->wr_ptr (length);   // Reflect additional bytes.
31       mblk->cont (payload);
32       return length; // Return length of the log record.
33     }
34   }
35   payload->release ();
36   mblk->release ();
37   payload = mblk = 0;
38   return -1;
39 }

Please see

http://www.cs.wustl.edu/~schmidt/ACE/book1/Errata.txt

for all the errata in C++NPv1.

Thanks,

        Doug