🚀 go-pugleaf

In article <3610F74A.A7A6BECD@mail.cern.ch>,
Marko Asplund  <aspa@mail.cern.ch> wrote:
>i have an application where i need to send C structs, with BSD socket
>interface's read() and write() routines, between heterogenous machine
>architectures. the structs are quite simple containing only char arrays
>and integers e.g.
>
>	struct data {
>		char somestring[9];
>		int status;
>		int foo;
>		char otherstring[5];
>	};
>
>so, my question is how do i accomplish sending this struct over the
>network, to a machine with different architecture? when i do a write()
>does the system send everything in the struct, including padding fields,
>over the network? i assume i can rely on the C compiler to preserve the
>order of the struct members. but, i probably can't rely on int member
>fields being of certain length (at least not on all platforms). can i
>assume something about the paddings between members? for example, can i
>assume that if the char arrays lengths are multiples of 4, there will be
>no padding fields in most architecture?

You can't really assume anything.  Besides the issues you raised, there's
also the problem of byte order within the integers.

You should use a standard encoding mechanism.  Most Unix systems include
the XDR library routines, which implement the encoding mechanism used by
ONC RPC protocols (e.g. NFS).

-- 
Barry Margolin, barmar@bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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