Re: [UDT] UDT to AIX portability, byte order, endianess problem

[Yunhong Gu <yu...@la...>]

Yes, you are right. somehow I skiped the testing between machines with 
different endianess. I have updated the CVS to reflect this bug fix.

Thanks,
Yunhong

On Tue, 13 Jun 2006 f....@fz... wrote:

> Hi
>
> I am trying to port UDT to AIX.
>
> Aside from some compiling difficulties (most of them arising due to gcc bugs - I had to use gcc version 3.2.1 - and the pthreads - see the additional flags in my Makefile below), I could not get the app/appserver/appclient application to work across AIX/POWERPC-boarders, meaning I could run the programs on localhost, even on 2 different AIX machines, and connect, but when trying to connect between AIX/POWERPC and LINUX/INTEL machines I got no connection with timeout errorsn no matter on which side the client/server was sitting.
>
> I suspected this to be an issue of byte ordering, and I found it to be in file src/channel.cpp, for example in line 155:
>
> const CChannel& CChannel::operator<<(CPacket& packet) const
> {
>   if (m_bEndianess)
>   {
>      // convert control information into network order
>      if (packet.getFlag())
>         for (int i = 0, n = packet.getLength() / 4; i < n; ++ i)
>            *((uint32_t *)packet.m_pcData + i) = htonl(*((uint32_t *)packet.m_pcData + i));
>
>      // convert packet header into network order
>      packet.m_nHeader[0] = htonl(packet.m_nHeader[0]);
>      packet.m_nHeader[1] = htonl(packet.m_nHeader[1]);
>   }
>
>
>
>
> so on a Big Endian architecture (m_bEndianess = true) this does a htonl(), converting the byte order from host to network order, but on a Little Endian architecture it doesnt.
>
>> From my understanding Network Byte Order IS ALREADY Big Endian, so shouldn't the littleendian machine actually do this conversion (an the bigendian skip it)?
>
> There are a few more htonl()s like the one above.
>
> I got everything to work with the changes in the source I pasted in below.
>
> Any further hints and suggestions for porting UDT to AIX are welcome :-)
>
> Kind regards,
>
> Franz Petri.
>
> PS: Just for curiousity: Did anybody get this to acutally work on OSX/POWERPC?! Or are the "Mac"-Powerpcs not bigendian?
>
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