pyo3/impl_/
pyclass_init.rs

1//! Contains initialization utilities for `#[pyclass]`.
2use crate::ffi_ptr_ext::FfiPtrExt;
3use crate::internal::get_slot::TP_ALLOC;
4use crate::types::PyType;
5use crate::{ffi, Borrowed, PyErr, PyResult, Python};
6use crate::{ffi::PyTypeObject, sealed::Sealed, type_object::PyTypeInfo};
7use std::marker::PhantomData;
8
9/// Initializer for Python types.
10///
11/// This trait is intended to use internally for distinguishing `#[pyclass]` and
12/// Python native types.
13pub trait PyObjectInit<T>: Sized + Sealed {
14    /// # Safety
15    /// - `subtype` must be a valid pointer to a type object of T or a subclass.
16    unsafe fn into_new_object(
17        self,
18        py: Python<'_>,
19        subtype: *mut PyTypeObject,
20    ) -> PyResult<*mut ffi::PyObject>;
21
22    #[doc(hidden)]
23    fn can_be_subclassed(&self) -> bool;
24}
25
26/// Initializer for Python native types, like `PyDict`.
27pub struct PyNativeTypeInitializer<T: PyTypeInfo>(pub PhantomData<T>);
28
29impl<T: PyTypeInfo> PyObjectInit<T> for PyNativeTypeInitializer<T> {
30    unsafe fn into_new_object(
31        self,
32        py: Python<'_>,
33        subtype: *mut PyTypeObject,
34    ) -> PyResult<*mut ffi::PyObject> {
35        unsafe fn inner(
36            py: Python<'_>,
37            type_object: *mut PyTypeObject,
38            subtype: *mut PyTypeObject,
39        ) -> PyResult<*mut ffi::PyObject> {
40            // HACK (due to FIXME below): PyBaseObject_Type's tp_new isn't happy with NULL arguments
41            let is_base_object = type_object == std::ptr::addr_of_mut!(ffi::PyBaseObject_Type);
42            let subtype_borrowed: Borrowed<'_, '_, PyType> = unsafe {
43                subtype
44                    .cast::<ffi::PyObject>()
45                    .assume_borrowed_unchecked(py)
46                    .downcast_unchecked()
47            };
48
49            if is_base_object {
50                let alloc = subtype_borrowed
51                    .get_slot(TP_ALLOC)
52                    .unwrap_or(ffi::PyType_GenericAlloc);
53
54                let obj = unsafe { alloc(subtype, 0) };
55                return if obj.is_null() {
56                    Err(PyErr::fetch(py))
57                } else {
58                    Ok(obj)
59                };
60            }
61
62            #[cfg(Py_LIMITED_API)]
63            unreachable!("subclassing native types is not possible with the `abi3` feature");
64
65            #[cfg(not(Py_LIMITED_API))]
66            {
67                match unsafe { (*type_object).tp_new } {
68                    // FIXME: Call __new__ with actual arguments
69                    Some(newfunc) => {
70                        let obj =
71                            unsafe { newfunc(subtype, std::ptr::null_mut(), std::ptr::null_mut()) };
72                        if obj.is_null() {
73                            Err(PyErr::fetch(py))
74                        } else {
75                            Ok(obj)
76                        }
77                    }
78                    None => Err(crate::exceptions::PyTypeError::new_err(
79                        "base type without tp_new",
80                    )),
81                }
82            }
83        }
84        let type_object = T::type_object_raw(py);
85        unsafe { inner(py, type_object, subtype) }
86    }
87
88    #[inline]
89    fn can_be_subclassed(&self) -> bool {
90        true
91    }
92}
pyo3/impl_/pyclass_init.rs

pyo3/impl_/
pyclass_init.rs
