Re: Adding a 'struct' into new python type
Hi Jason,
Thanks for the response. Okay, Will try to convert 'struct test' into
new python object (say 'PyStructTest') and include it inside
CountDictType as pyobject instead of 'struct'.
Will post details here, If i encounter any issues.
Cheers,
Lakshmipathi.G
FOSS Programmer.
www.giis.co.in/readme.html
On Sat, Mar 7, 2015 at 9:23 PM, Jason Swails jason.swa...@gmail.com wrote:
On Sat, Mar 7, 2015 at 4:15 AM, Lakshmipathi.G lakshmipath...@gmail.com
wrote:
Hi,
I'm following this example :
http://nedbatchelder.com/text/whirlext.html#h_making_a_type and trying
to add
new data into 'CountDict' type
Adding a simple 'char' works well.
typedef struct {
PyObject_HEAD
PyObject * dict;
int count;
char c; //add this and placed an entry into PyMemberDef as T_CHAR.
} CountDict;
I can access 'c' from python code,no issues so far.
Now I want to added 'struct type' into this 'CountDict' type.
struct test {
int x;
};
typedef struct {
PyObject_HEAD
PyObject * dict;
int count;
char c;
struct test t1; //?? how to add this
} CountDict;
How to do achieve this? (Due to legacy code dependency, I can't use
ctype/cpython etc).
thanks for any help/pointers.
The way *I* would do this is turn struct test into another Python object.
Then instead of defining it in CountDict as type struct test, define it as
the PyStructTest that you assigned it to when you turned it into a Python
class.
For example, in that website you linked to, CountDict was turned into a
CountDictType Python type. So do something similar to test in which you
turn it into a PyStructTest type in the same way. Then declare it as a
PyStructTest pointer instead of a struct test.
I'm not sure you can get around an approach like this. I believe that in
order to access data from Python, it needs to be a Python type. The
struct-to-Python-type conversion *knows* how to translate basic types, like
char, double, float, int, and long into their Python equivalents; but it
can't handle something as potentially complicated as an arbitrary struct.
Of course, if all you want to do is access t1 from C, then I think what you
have is fine.
Good luck,
Jason
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Adding a 'struct' into new python type
Hi,
I'm following this example :
http://nedbatchelder.com/text/whirlext.html#h_making_a_type and trying
to add
new data into 'CountDict' type
Adding a simple 'char' works well.
typedef struct {
PyObject_HEAD
PyObject * dict;
int count;
char c; //add this and placed an entry into PyMemberDef as T_CHAR.
} CountDict;
I can access 'c' from python code,no issues so far.
Now I want to added 'struct type' into this 'CountDict' type.
struct test {
int x;
};
typedef struct {
PyObject_HEAD
PyObject * dict;
int count;
char c;
struct test t1; //?? how to add this
} CountDict;
How to do achieve this? (Due to legacy code dependency, I can't use
ctype/cpython etc).
thanks for any help/pointers.
Cheers,
Lakshmipathi.G
FOSS Programmer.
www.giis.co.in/readme.html
--
https://mail.python.org/mailman/listinfo/python-list
Re: how avoid delay while returning from C-python api?
Yes, Cython looks easier but the problem its a very old code ( 6 or 7 years ). Almost entire code base uses plain python-c api. Thanks for the example, will use Cython or Ctypes way for side-projects! Cheers, Lakshmipathi.G FOSS Programmer. www.giis.co.in/readme.html -- https://mail.python.org/mailman/listinfo/python-list
how avoid delay while returning from C-python api?
Hi -
I have C-Python api like below. It works fine, but the problem is
while invoking this method
from python script say
#cat script.py
snip
offset=0
size=4
write_object(offset,size)
/snip
This calls write_this_c() C api and returns quickly to next printf statement.
But the return call (Py_RETURN_NONE) takes something like 4-6 seconds.
-
static
PyMethodDef xyz_methods[] = {
{write_object, write_object, METH_VARARGS,write some stuff },
{NULL, NULL, 0, NULL}
};
static PyObject *
write_object(PyObject *self, PyObject *args)
{
int offset, size;
if (!PyArg_ParseTuple(args,ii, offset, size))
Py_RETURN_NONE;
printf(before call);
write_this_c(offset, size);
printf(after call);
Py_RETURN_NONE; ##delay happens here
}
How to avoid this delay time? Thanks for any help/pointers!
Cheers,
Lakshmipathi.G
FOSS Programmer.
www.giis.co.in
--
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Re: how avoid delay while returning from C-python api?
The statement after call printed to stdout and the script waits there for few seconds. So I was assuming something delaying the return value. Just found out there is core-dump segmentation fault (core dumped) python ..Probably fixing core dump should resolve the issue. Thanks! Cheers, Lakshmipathi.G FOSS Programmer. www.giis.co.in -- https://mail.python.org/mailman/listinfo/python-list
Re: Reading c struct via python
Looks like your e... Is that the key field? Yes, you are right 'e' is the key. And rest of them are data. AND the order of the items is o before i -- that doesn't seem to match your C struct definition. Sorry, I was testing the bdb and while doing that I noticed, c-struct order is not same as inserted bdb record . But forgot to fix the struct order before posting it here. (And also I didn't expect someone will dig this deeper on the binary string output :p . Thanks for your effort! ) s format in which you precode the length of the string in the format (10s is a 10 character string), and p format in which the first byte of the string is the length (0..255) of the rest of the string. The struct module doesn't handle C-type null terminated strings directly. I think we can use 'p' format. (Thus storing the string-length before actual string content). That should help us unpack easily. Thanks Dennis Lee Bieber, for the detailed info and step by step parsing of the output. It really helped. -- Wulfraed Dennis Lee Bieber AF6VN wlfr...@ix.netcom.comHTTP://wlfraed.home.netcom.com/ -- https://mail.python.org/mailman/listinfo/python-list -- Cheers, Lakshmipathi.G FOSS Programmer. www.giis.co.in -- https://mail.python.org/mailman/listinfo/python-list
Reading c struct via python
Hi -
We have C code which writes following struct into berkeley db (my_db.db).
struct my_info {
unsigned long int i, e;
int o;
char *f;
char *s;
};
How to read this via Python? Google search gave this code
---
$ cat pybsd2.py
from bsddb import db
fruitDB = db.DB()
fruitDB.open('my_db.db', None, db.DB_BTREE, db.DB_DIRTY_READ)
cursor = fruitDB.cursor()
rec = cursor.first()
while rec:
print rec
rec = cursor.next()
fruitDB.close()
---
While storing an entry (o=500,f=/home/laks/abcde,s=OSr,i=4668368
,e=1) and reading it back i get
$ python pybsd2.py
(\x10'\x00\x00\x00\x00\x00\x00,
\xf4\x01\x00\x00\xd0;G\x00\x00\x00\x00\x00\x10'\x00\x00\x00\x00\x00\x00/home/laks/abcde\x00OSr\x00)
And this http://docs.python.org/2/library/bsddb.html says bdb module is
removed recently.
Further Searching provides modules like cpickle,ctypes,struct - not sure
which is the right approach/way to proceed.
Should we proceed with bdb module and find out how to retrive integer from
db or use others like ctypes/(c)pickle/struct etc?
Thanks for any help.
Ps : If this question already answered and discussed often, please redirect
me to that thread.
--
Cheers,
Lakshmipathi.G
FOSS Programmer.
www.giis.co.in
--
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Re: Reg secure python environment with web terminal emulator
the same exploits. Think of a binary generated elsewhere (where gcc is available) and put into your environment. That's pretty bad news :( I am convinced that 100 % security is impossible - and correspondingly would use a pragmatic approach: I would rely on OS level constraints (user with very restricted rights, process running in an isolated box) - and ensure the OS is kept up to date to reduce the risk of exploits of OS security weaknesses. Yes,agree 100% security will never be possible. I'll explore about running process as an isolated box. Thanks for the suggestions and inputs. -- Cheers, Lakshmipathi.G FOSS Programmer. www.giis.co.in -- http://mail.python.org/mailman/listinfo/python-list
Re: pexpect, loading an entry field
Hi -
I'm using Python 2.7.3 (Fedora 17) . I tried a simple example with
pexpect to copy a file to remote system. It works
$ cat pex.py
import pexpect
s = pexpect.spawn ('scp pex.py root@10.30.77.244:/tmp')
s.expect ('Password:')
s.sendline ('a')
s.expect(pexpect.EOF,timeout=20)
Execute above program (change remote ip and password) - If it works
then its not an issue with pexpect or python
environment.
--
Cheers,
Lakshmipathi.G
FOSS Programmer.
www.giis.co.in
On Tue, Aug 6, 2013 at 11:33 PM, inq1ltd inq1...@inqvista.com wrote:
pexpect looks simple to use. Please check this example
http://www.pythonforbeginners.com/systems-programming/how-to-use-the-pexpect
-module-in-python/
python help;
I am using pexpect to open my program.
Can someone tell me how to get data to appear in
an entry field.
After pexpect opens the my program I have tried to use
send, sendline, and write functions to try to put data into
the program's entry field.
However, the data is going to the terminal window,
the window that is used to initiate the call to pexpect
but not to the entry field in the open program.
I would appreciate suggestions.
jol
Thanks for the response.
I have been there but that site gives me
the same information that I get from
noah.org. I have the pexpect docs and they presume
that this problem doesn't exist.
None of the information in the NOAH site or the FAQ's
address this question.
I'm using suse linux running python 2.7 and pexpect.
The data, when using send() method is going to the terminal window,
This is the same window that is used to initiate the call to pexpect.
Pexpect opens the program but the send method sends
data to the terminal window, not the entry field located
in the child spawned by pexpect.
interact works, as does close(), TIMEOUT, EOF, before, after,
expect_exact and methods. But the entry field does not
load.
So my question is;
Why??
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Re: Reg secure python environment with web terminal emulator
Hi - Thanks for the response. Yes, we used OS features to restrict the system user accounts. We don't allow gcc - this helped us to avoid kernel exploits via C code like : https://www.centos.org/modules/newbb/viewtopic.php?viewmode=flattopic_id=42827forum=59 https://bugzilla.redhat.com/show_bug.cgi?id=962792 We are concerned whether user may try C exploits via Python code and break the system. What's the minimal python set-up you would suggest? I'm thinking something like: 1- Uninstall python-devel packages 2- Remove easy_install or pip (any such install utilities) 3- Keep only very basic modules under /usr/lib/python/site-packages and delete the others. Thanks. -- Cheers, Lakshmipathi.G FOSS Programmer. www.giis.co.in On Wed, Aug 7, 2013 at 11:35 AM, dieter die...@handshake.de wrote: Lakshmipathi.G lakshmipath...@gmail.com writes: We have a server running a web-based terminal emulator (based on shellinabox for screen-casting check www.webminal.org) that allows users to learn simple bash commands. This Linux environment secured by things like quota, selinux,ulimit etc Now some users are requesting python access. How to ensure python is executed in a restricted environment. I came across http://docs.python.org/2/library/restricted.html but it seems like disabled in 2.3. Any thoughts on how we can safely provide python access to users. When you are satisfied with the protection you have achieved for bash commands, those same protection might be sufficient for Python as well. I assume that you used operating system facilities to restrict what the (system) user can do on the operating system level: the same restriction would apply to the (same) user executing Python code. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Reg secure python environment with web terminal emulator
If you permit file I/O and anything that can spawn a process, it is
possible to create a raw binary executable and trigger its execution.
--
Yes,we permit file i/o with quota limits and spawning a process is
allowed upto a limit.
If I'm not wrong, we will be safe if user invokes subprocess or
os.system('sudo') calls
due to system constraints.
Could you please share more info about creating raw binary executable
and its potential
problem.
Thanks for your response.
--
Cheers,
Lakshmipathi.G
FOSS Programmer.
www.giis.co.in
--
http://mail.python.org/mailman/listinfo/python-list
Reg secure python environment with web terminal emulator
Hi - We have a server running a web-based terminal emulator (based on shellinabox for screen-casting check www.webminal.org) that allows users to learn simple bash commands. This Linux environment secured by things like quota, selinux,ulimit etc Now some users are requesting python access. How to ensure python is executed in a restricted environment. I came across http://docs.python.org/2/library/restricted.html but it seems like disabled in 2.3. Any thoughts on how we can safely provide python access to users. I hope this is the correct mailing-list, If not please redirect me to the right one. Thanks for any help. -- Cheers, Lakshmipathi.G FOSS Programmer. www.giis.co.in -- http://mail.python.org/mailman/listinfo/python-list
Re: pexpect, loading an entry field
pexpect looks simple to use. Please check this example http://www.pythonforbeginners.com/systems-programming/how-to-use-the-pexpect-module-in-python/ -- Cheers, Lakshmipathi.G FOSS Programmer. www.giis.co.in On Tue, Aug 6, 2013 at 8:35 PM, inq1ltd inq1...@inqvista.com wrote: python help; I am using pexpect to open my program. Can someone tell me how to get data to appear in an entry field. After pexpect opens the my program I have tried to use send, sendline, and write functions to try to put data into the program's entry field. However, the data is going to the terminal window, the window that is used to initiate the call to pexpect but not to the entry field in the open program. I would appreciate suggestions. jol -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
