Mikael Normark wrote:
> I checked the size of int and long long on both systems and found that
> they were the same but when I checked sizeof(struct sample_pkt_t) it
> returned 396 on Ubuntu and 528 on Cygwin so I need to find a
> workaround for the adressing issue, perhaps that solves the problem.
It's a well-known problem in C that the same struct can be laid out
differently on different machines according to padding rules. There is a lot
of knowledge out there on the ways to address these problems when transferring
data over a network, protocols like RPC use a process called "marshalling" to
communicate data structures item-by-item in a canonical format, but that's
perhaps a little over-engineered for your needs here. (Well, depends; are you
planning on making this application part of a massive public deployment
somewhere, or is it mostly for your own personal use?)
>> // Holdning the raw sample data and timestamp when
>> // the sample was fetched.
>> struct sample_t{
>> int sample;
>> long long timestamp;
>> };
>>
>> // A package that will hold samples data over
>> // the TCP transfer.
>> struct sample_pkg_t{
>> unsigned int type; //Should
>> always be PKG_SAMPLES
>> unsigned int pkg_nr; //Counter
>> increased for each package
>> unsigned int nr_samples; // Shouldbe same
>> as ADC_SAMPLES_IN_PKG
>> struct sample_t sample[SAMPLES_IN_PKG]; // The samples data
>> };
If you want a quick bodge that will work for your situation (but it only
works because Cygwin and Ubuntu have the same size types involved, and might
well fall down when 64-bit hosts try to talk to 32-bit hosts), take a look in
the GCC manual for the use of "attribute ((__packed__))" on the struct
definition. You could make it more 32-vs-64 robust by replacing all the types
with the stdint.h size-specific types (int -> int32_t, long long -> int64_t,
unsigned int -> uint32_t) as well if you liked.
cheers,
DaveK
--
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
Problem reports: http://cygwin.com/problems.html
Documentation: http://cygwin.com/docs.html
FAQ: http://cygwin.com/faq/
