pyo3/
type_object.rs

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1//! Python type object information
2
3use crate::ffi_ptr_ext::FfiPtrExt;
4use crate::types::any::PyAnyMethods;
5use crate::types::{PyAny, PyType};
6use crate::{ffi, Bound, Python};
7use std::ptr;
8
9/// `T: PyLayout<U>` represents that `T` is a concrete representation of `U` in the Python heap.
10/// E.g., `PyClassObject` is a concrete representation of all `pyclass`es, and `ffi::PyObject`
11/// is of `PyAny`.
12///
13/// This trait is intended to be used internally.
14///
15/// # Safety
16///
17/// This trait must only be implemented for types which represent valid layouts of Python objects.
18pub unsafe trait PyLayout<T> {}
19
20/// `T: PySizedLayout<U>` represents that `T` is not a instance of
21/// [`PyVarObject`](https://docs.python.org/3/c-api/structures.html#c.PyVarObject).
22///
23/// In addition, that `T` is a concrete representation of `U`.
24pub trait PySizedLayout<T>: PyLayout<T> + Sized {}
25
26/// Python type information.
27/// All Python native types (e.g., `PyDict`) and `#[pyclass]` structs implement this trait.
28///
29/// This trait is marked unsafe because:
30///  - specifying the incorrect layout can lead to memory errors
31///  - the return value of type_object must always point to the same PyTypeObject instance
32///
33/// It is safely implemented by the `pyclass` macro.
34///
35/// # Safety
36///
37/// Implementations must provide an implementation for `type_object_raw` which infallibly produces a
38/// non-null pointer to the corresponding Python type object.
39pub unsafe trait PyTypeInfo: Sized {
40    /// Class name.
41    const NAME: &'static str;
42
43    /// Module name, if any.
44    const MODULE: Option<&'static str>;
45
46    /// Returns the PyTypeObject instance for this type.
47    fn type_object_raw(py: Python<'_>) -> *mut ffi::PyTypeObject;
48
49    /// Returns the safe abstraction over the type object.
50    #[inline]
51    fn type_object(py: Python<'_>) -> Bound<'_, PyType> {
52        // Making the borrowed object `Bound` is necessary for soundness reasons. It's an extreme
53        // edge case, but arbitrary Python code _could_ change the __class__ of an object and cause
54        // the type object to be freed.
55        //
56        // By making `Bound` we assume ownership which is then safe against races.
57        unsafe {
58            Self::type_object_raw(py)
59                .cast::<ffi::PyObject>()
60                .assume_borrowed_unchecked(py)
61                .to_owned()
62                .downcast_into_unchecked()
63        }
64    }
65
66    /// Checks if `object` is an instance of this type or a subclass of this type.
67    #[inline]
68    fn is_type_of(object: &Bound<'_, PyAny>) -> bool {
69        unsafe { ffi::PyObject_TypeCheck(object.as_ptr(), Self::type_object_raw(object.py())) != 0 }
70    }
71
72    /// Checks if `object` is an instance of this type.
73    #[inline]
74    fn is_exact_type_of(object: &Bound<'_, PyAny>) -> bool {
75        unsafe {
76            ptr::eq(
77                ffi::Py_TYPE(object.as_ptr()),
78                Self::type_object_raw(object.py()),
79            )
80        }
81    }
82}
83
84/// Implemented by types which can be used as a concrete Python type inside `Py<T>` smart pointers.
85pub trait PyTypeCheck {
86    /// Name of self. This is used in error messages, for example.
87    const NAME: &'static str;
88
89    /// Checks if `object` is an instance of `Self`, which may include a subtype.
90    ///
91    /// This should be equivalent to the Python expression `isinstance(object, Self)`.
92    fn type_check(object: &Bound<'_, PyAny>) -> bool;
93}
94
95impl<T> PyTypeCheck for T
96where
97    T: PyTypeInfo,
98{
99    const NAME: &'static str = <T as PyTypeInfo>::NAME;
100
101    #[inline]
102    fn type_check(object: &Bound<'_, PyAny>) -> bool {
103        T::is_type_of(object)
104    }
105}
pyo3/type_object.rs

pyo3/
type_object.rs
