freakin out over C++ module in python

[nephish@xit.net]

lo there all !

i have a huge delima, i have to be able to connect to a data server and
recieve info from it. The servers software guys release some visual C++
modules that one can incorporate into a visual C++ project. Which is
great, but i am developing in linux, and only am very familliar with
python. i have tried to use swig to make a python module out of it, and
it wouldn't work. Tried to just compile them with gcc and that would
not work either. So, i have to go thru and try to re-create them in
python. So here is the trick, i don't know anything about C++, but this
has got to work.


and so, i guess the main question i have is.... is there a module or
program that will parse these classes and duplicate them for a python
module ? Some kind of code translator ? Or is that just way out there?

i would go thru it line by line, but i just dont know enough about C++,
how it pulls off a socket connection, etc.. and some of the things i
dont know how to do in python. like how to make an unsigned long init.

whew. so, i guess i could google each line... but if someone has an
easier alternative, i am all ears.. its about 400 lines total.

thanks.
sk

[Diez B. Roggisch]

Re: freakin out over C++ module in python

> and so, i guess the main question i have is.... is there a module or[color=blue]
> program that will parse these classes and duplicate them for a python
> module ? Some kind of code translator ? Or is that just way out there?[/color]

No, there isn't.
[color=blue]
> i would go thru it line by line, but i just dont know enough about C++,
> how it pulls off a socket connection, etc.. and some of the things i
> dont know how to do in python. like how to make an unsigned long init.[/color]

Use module struct.

Regards,

Diez

[nephish@xit.net]

Re: freakin out over C++ module in python

ok, well enough, looked at struct and it does seem to be what i am
after. for that anyway.
thanks, guess i will just have to take the time and pull it apart.

cheers
sk

[Jay Parlar]

Re: freakin out over C++ module in python


On Apr 18, 2006, at 4:43 AM, nephish@xit.net wrote:
[color=blue]
> ok, well enough, looked at struct and it does seem to be what i am
> after. for that anyway.
> thanks, guess i will just have to take the time and pull it apart.
>[/color]

I recommend you also take a look at http://pyconstruct.sourceforge.net/
It has the same purpose as 'struct', but is MUCH more Pythonic. I've
described Contstruct as "the replacement for 'struct' I've been looking
for since I started coding in Python".

Jay P.

[Michael Ekstrand]

Re: freakin out over C++ module in python

nephish@xit.net wrote:[color=blue]
> i would go thru it line by line, but i just dont know enough about C++,
> how it pulls off a socket connection, etc.. and some of the things i
> dont know how to do in python. like how to make an unsigned long init.[/color]

The networking code in C++ should be at least vaguely similar to the
appropriate Python code using the socket module. Python's socket module
is a fairly thin wrapper around BSD sockets; its method names, etc.
match the socket system calls. If the C++ is using plain berkely-ish
socket code, you'll find connect(), send(), recv() calls (or something
similar - I don't know what Winsock calls them for sure); these map to
appropriate methods and functions in the socket module. If the C++ code
is using some C++ sockets wrapper, I don't know; it still would probably
be somewhat similar. Or similar enough that you can read it. Unless
they're somehow finagling sockets in to the iostreams library (possible,
but unlikely).

- Michael

--
mouse, n: a device for pointing at the xterm in which you want to type.
-- Fortune
Visit me on the Web: http://www.elehack.net

[nephish@xit.net]

Re: freakin out over C++ module in python

pyconstruct looks cool. i dont know if the classes are using the plain
berkely-ish code. i couldn't find anything in it that pointed to send()
recv(), & such. i found other stuff like SetSocketOpt() and so on like
this :

long CClientSocket:: ConnectToServer (LPCTSTR serverAddr, UINT port)

{

BOOL socketOption = TRUE;

const int rcvBuffsize = 64 *1024;

const int sendBuffsize = 64*1024;



if ( !Create() )

return ERR_SOCKET_CREA TE;

int intvalue = sizeof(int);

if(!( SetSockOpt(SO_D ONTROUTE,&socke tOption,sizeof( BOOL),SOL_SOCKE T)
&&

SetSockOpt(SO_R CVBUF,&rcvBuffs ize,sizeof(int) ,SOL_SOCKET) &&

SetSockOpt(SO_S NDBUF,&sendBuff size,sizeof(int ),SOL_SOCKET) &&

SetSockOpt(TCP_ NODELAY,&socket Option,sizeof(B OOL),SOL_SOCKET ) &&

SetSockOpt(SO_K EEPALIVE,&socke tOption,sizeof( BOOL),SOL_SOCKE T)))

return ERR_SOCKET_CREA TE;


i looked around for some of these and found most references to UDP. I
guess its also a windows specific thing too. thanks for the tips
gents....

[Serge Orlov]

Re: freakin out over C++ module in python

nephish@xit.net wrote:[color=blue]
> pyconstruct looks cool. i dont know if the classes are using the plain
> berkely-ish code. i couldn't find anything in it that pointed to send()
> recv(), & such. i found other stuff like SetSocketOpt() and so on like
> this :
>
> long CClientSocket:: ConnectToServer (LPCTSTR serverAddr, UINT port)
>
> {
>
> BOOL socketOption = TRUE;
>
> const int rcvBuffsize = 64 *1024;
>
> const int sendBuffsize = 64*1024;
>
>
>
> if ( !Create() )
>
> return ERR_SOCKET_CREA TE;
>
> int intvalue = sizeof(int);
>
> if(!( SetSockOpt(SO_D ONTROUTE,&socke tOption,sizeof( BOOL),SOL_SOCKE T)
> &&
>
> SetSockOpt(SO_R CVBUF,&rcvBuffs ize,sizeof(int) ,SOL_SOCKET) &&
>
> SetSockOpt(SO_S NDBUF,&sendBuff size,sizeof(int ),SOL_SOCKET) &&
>
> SetSockOpt(TCP_ NODELAY,&socket Option,sizeof(B OOL),SOL_SOCKET ) &&
>
> SetSockOpt(SO_K EEPALIVE,&socke tOption,sizeof( BOOL),SOL_SOCKE T)))
>
> return ERR_SOCKET_CREA TE;
>
>
> i looked around for some of these and found most references to UDP. I
> guess its also a windows specific thing too.[/color]

Nope. It's a UNIX function:

http://www.opengroup.org/onlinepubs/007908799/xns/setsockopt.html

And corresponding Python stuff is in the socket module. The code above
can be roughly translated as

def ConnectToServer (self, serverAddr, port):
s = socket.socket(s ocket.AF_INET, socket.SOCK_STR EAM)
self.connection = s
s.connect((serv erAddr, port))
s.setsockopt(so cket.SOL_SOCKET , socket.SO_DONTR OUTE, 1)
s.setsockopt(so cket.SOL_SOCKET , socket.TCP_NODE LAY, 1)
s.setsockopt(so cket.SOL_SOCKET , socket.SO_KEEPA LIVE, 1)
s.setsockopt(so cket.SOL_SOCKET , socket.SO_RCVBU F, 64*1024)
s.setsockopt(so cket.SOL_SOCKET , socket.SO_SNDBU F, 64*1024)

Note, you don't need to handle errors in this method like C++ code,
instead catch socket.error exception where you handle *all* fatal
exceptions during connection setup.

With regards to your first question about automatic language
translation - don't even dream about it. IMHO, C++ is one of the most
complicated high-level languages for automatic translation.

[nephish@xit.net]

Re: freakin out over C++ module in python

wow , thanks for the tips and the link.. i can at least see whats going
on here.
this project is beginning to look believable to me.

i have another question.. later , in this same class, after it goes
thru some error handling, it returns like this
return COM_SUCCESS;
but i cannot find where COM_SUCCESS is defined.
can something in C++ just represent itself?

thanks again for all your help.

[Serge Orlov]

Re: freakin out over C++ module in python


nephish@xit.net wrote:[color=blue]
> wow , thanks for the tips and the link.. i can at least see whats going
> on here.
> this project is beginning to look believable to me.
>
> i have another question.. later , in this same class, after it goes
> thru some error handling, it returns like this
> return COM_SUCCESS;
> but i cannot find where COM_SUCCESS is defined.
> can something in C++ just represent itself?[/color]

Unlikely. This is just C-style error handling. If function returns 0 it
means there were no error and if it return non-zero it means error. You
can do the same in python, but I would recommend using exceptions. If
there is an error you raise an exception, if there is no error, you
don't do anything.

[nephish@xit.net]

Re: freakin out over C++ module in python

sounds cool, most stuff i write is strife with try - except

thanks for the tip

-sk