Passing a memory address (pointer) to an extension?
gagsl-py2 at yahoo.com.ar
Thu Oct 23 05:13:36 CEST 2008
En Wed, 22 Oct 2008 19:10:27 -0200, Philip Semanchuk
<philip at semanchuk.com> escribió:
> I'm writing a Python extension in C that wraps a function which takes a
> void * as a parameter. (The function is shmat() which attaches a chunk
> of shared memory to the process at the address supplied by the caller.)
> I would like to expose this function to Python, but I don't know how to
> define the interface.
> Specifically, when calling PyArg_ParseTuple(), what letter should I use
> to represent the pointer in the format string? The best idea I can come
> up with is to use a long and then cast it to a void *, but assuming that
> a long is big enough to store a void * is a shaky assumption. I could
> use a long long (technically still risky, but practically probably OK)
> but I'm not sure how widespread long longs are.
Are you *really* sure you want to supply a specific address argument? Most
of the time (if not always, unless you're doing really low level stuff) a
NULL is perfectly adequate.
Anyway, if it's going to be called from Python, the argument will be a
Python integer (or long) object); you may get the value using
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