Re: [boost] Re: Boost::Python

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-10-01 10:32:27

Great idea. Would you care to post it at the boost-users Wiki?

http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl

===================================================
  David Abrahams, C++ library designer for hire
 resume: http://users.rcn.com/abrahams/resume.html

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          email: david.abrahams_at_[hidden]
===================================================

----- Original Message -----
From: <daveh-lists_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Monday, October 01, 2001 10:03 AM
Subject: [boost] Re: Boost::Python

>
>
> Another method that I have used is to create a class interface to
> your buffer which includes a copy constructor, maybe something along
> these lines (This is not complete, just for an idea):
>
> class AccessBuffer
> {
> public:
>   AccessBuffer(const void *pData) : m_pData(pData)
>   {
>   }
>   AccessBuffer(const AccessBuffer &rBuffer)
>   {
>     m_pData = rBuffer.m_pData;
>   }
>   AccessBuffer &operator=(const AccessBuffer &rBuffer)
>   {
>     m_pData = rBuffer.m_pData;
>     return *this;
>   }
>   // Add your data manipulation functions here
>   unsigned char GetByte(int n)
>   {
>     return ((const unsigned char *)m_pData)[n];
>   }
> private:
>   const void *m_pData;
> };
>
> Then you just need to declare the class and the data manipulation
> methods in boost and pass a reference (not pointer) to this class in
> your function call.
>
> I have successfully used boost::python to support embedding python
> and have objects that simultaneously exist (can be called from) in
> python and c++ and that have virtual methods that can be overriden in
> python.
>
>
> Dave Hawkes
>
> --- In boost_at_y..., "David Abrahams" <david.abrahams_at_r...> wrote:
> > Mike,
> >
> > First of all, you'll need to pick a different interface
> for "function" (or
> > wrap a different function and have it call your function), because
> > Boost.Python can only convert a single Python object into a single
> function
> > parameter.
> >
> > Probably the easiest thing you can do is to write a function taking
> a
> > boost::python::ref (which is kind of a smart pointer to a
> PyObject), and
> > just use the regular Python 'C' API to extract the buffer data.
> >
> > If you want to get fancier, you could create a type which
> corresponds to a
> > Python buffer (perhaps struct my_buffer { void* data; int size; };)
> and
> > write a family of from_python(PyObject*, type<buffer>) functions
> which check
> > the argument type and convert Python buffers into your buffer type.
> You can
> > look at boost/python/conversions.hpp for some examples. That would
> allow you
> > to automatically wrap functions which accept my_buffer arguments.
> >
> > HTH,
> > Dave
> >
> > ===================================================
> >   David Abrahams, C++ library designer for hire
> >  resume: http://users.rcn.com/abrahams/resume.html
> >
> >         C++ Booster (http://www.boost.org)
> >           email: david.abrahams_at_r...
> > ===================================================
> >
> > ----- Original Message -----
> > From: "Mike Ensor" <MikeEnsor_at_C...>
> > To: <boost_at_y...>
> > Sent: Saturday, September 29, 2001 7:47 PM
> > Subject: [boost] Boost::Python
> >
> >
> > > I am using Boost.Python to build c++ to python wrappers.  I am
> > > trying to make binary data available to python and visa versa.  I
> have
> > tried
> > > many different approaches.  The functions in C++ look similar to
> this:
> > >
> > > void function(const void* buffer, int size);
> > >
> > > and in python I can create a "buffer" of information.  When I
> check
> > > the type of the "buffer" it is a "buffer".
> > >
> > > When I compile the c++ it won't let me because "none of the 425
> > > overloads can convert prameter 2 from type 'struct
> > boost::python::type<void
> > > const*>'"
> > >
> > > How do I make the const void * be seen in Python and how do I send
> > > in binary data into this function from python?
> > >
> > > Thank you for your help,
> > > Mike Ensor
> > > mikeensor_at_c...
> > >
> > >
> > > Info: http://www.boost.org  Unsubscribe:
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> > >
>
>
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