[Feature Usage]

[yashgupta1299]

This is a correct way to use it? Because when I am not using keep alive policy it is stil working? why. Also In existing usage should I take buffer as const ref or it is fine??

I want to make sure data_view remain valid and even if arr goes out of scope or del still data_view points to valid memory. I do not want to do a memcopy from python to pybind11 rather want to use the same mem inside c++ via pybind 11.

Python Code:

arr = np.array([1, 2, 3, 4, 5], dtype=np.uint8)
data = Data(arr)
data_view = np.frombuffer(data, dtype=np.uint8)
arr[0] = 7
data_view[1] = 8
print(arr, data_view) # [7 8 3 4 5] [7 8 3 4 5]

typedef struct {
// Buffer Size
size_t size;
// Buffer pointer
uint8_t *data;
} Data;

PYBIND11_MODULE(mymod, m) {
py::class<Data, std::shared_ptr>(m, "Data", py::buffer_protocol())
.def(py::init<>())
.def(py::init([](py::buffer buffer) {
py::buffer_info info = buffer.request();
auto qdata = std::make_shared();
qdata->size = info.itemsize * info.size;
qdata->data = static_cast<uint8_t*>(info.ptr);
return qdata;
}), py::keep_alive<1, 2>())
.def_buffer([](Data &qdata) -> py::buffer_info {
return pybind11::buffer_info(qdata.data, qdata.size);
})
.def_readonly("size", &Data::size)
.def_readonly("data", &Data::data);
}