On 04/18/2012 01:57 PM, Christoph Rupp wrote:
Hi,
i have a C++ class that i'm wrapping with boost::python:
class Foo {
// ...
const char *get_buffer();
size_t get_size() const;
// ...
};
I want to send this class through a thrift interface (which uses the
write() method to send the data to a file or a socket). For a few days now
i'm trying to implement this. By now i understand that i have to implement
the buffer protocol, and i know that i can create a buffer with
boost::python (read-only access is sufficient):
inline object as_buffer(const Foo&f) {
return object (handle<> (PyBuffer_FromMemory ((void*)f.get_buffer(),
f.get_size())));
}
(This is based on an email from 2009 that i found in this mailing list's
archive.)
But i do not know how to glue it together to form a full module. This is
how the module looks right now:
BOOST_PYTHON_MODULE(Foo)
{
class_<Foo, boost::noncopyable>("Foo",
init<int32_t, bool>())
.def("add", afn)
.def("finalize",&Foo::finalize)
.def("empty",&Foo::empty)
.def("clear",&Foo::clear)
;
}
How can i include that buffer conversion?
Sorry about the long delay in a reply, but I'm afraid that right now it
looks *really* tricky (possibly impossible) to add the buffer protocol
to a Boost.Python class. Python doesn't have a special named methods
for the buffer protocol:
http://stackoverflow.com/questions/2079272/which-methods-implement-the-buffer-interface-in-python
And Boost.Python doesn't give you access to the PyTypeObject structure
where you'd be able to add the PyBufferProcs slots.
I think you have two options:
- Wrap your buffer-getter function with another name and find a way to
get your serialization code to use that.
- Wrap this class class using the raw Python C-API and use
Boost.Python custom lvalue converters to make it work with any
Boost.Python-wrapped code you have. You could use Boost.Python to wrap
all the member functions, for instance, and add them to the Python C-API
class's dict.
Neither option is great, but hopefully one will allow you to move forward.
HTH!
Jim
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