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 /// Deprecated name for [`PyTypeInfo::type_object`].
67 #[deprecated(since = "0.23.0", note = "renamed to `PyTypeInfo::type_object`")]
68 #[inline]
69 fn type_object_bound(py: Python<'_>) -> Bound<'_, PyType> {
70 Self::type_object(py)
71 }
72
73 /// Checks if `object` is an instance of this type or a subclass of this type.
74 #[inline]
75 fn is_type_of(object: &Bound<'_, PyAny>) -> bool {
76 unsafe { ffi::PyObject_TypeCheck(object.as_ptr(), Self::type_object_raw(object.py())) != 0 }
77 }
78
79 /// Deprecated name for [`PyTypeInfo::is_type_of`].
80 #[deprecated(since = "0.23.0", note = "renamed to `PyTypeInfo::is_type_of`")]
81 #[inline]
82 fn is_type_of_bound(object: &Bound<'_, PyAny>) -> bool {
83 Self::is_type_of(object)
84 }
85
86 /// Checks if `object` is an instance of this type.
87 #[inline]
88 fn is_exact_type_of(object: &Bound<'_, PyAny>) -> bool {
89 unsafe {
90 ptr::eq(
91 ffi::Py_TYPE(object.as_ptr()),
92 Self::type_object_raw(object.py()),
93 )
94 }
95 }
96
97 /// Deprecated name for [`PyTypeInfo::is_exact_type_of`].
98 #[deprecated(since = "0.23.0", note = "renamed to `PyTypeInfo::is_exact_type_of`")]
99 #[inline]
100 fn is_exact_type_of_bound(object: &Bound<'_, PyAny>) -> bool {
101 Self::is_exact_type_of(object)
102 }
103}
104
105/// Implemented by types which can be used as a concrete Python type inside `Py<T>` smart pointers.
106pub trait PyTypeCheck {
107 /// Name of self. This is used in error messages, for example.
108 const NAME: &'static str;
109
110 /// Checks if `object` is an instance of `Self`, which may include a subtype.
111 ///
112 /// This should be equivalent to the Python expression `isinstance(object, Self)`.
113 fn type_check(object: &Bound<'_, PyAny>) -> bool;
114}
115
116impl<T> PyTypeCheck for T
117where
118 T: PyTypeInfo,
119{
120 const NAME: &'static str = <T as PyTypeInfo>::NAME;
121
122 #[inline]
123 fn type_check(object: &Bound<'_, PyAny>) -> bool {
124 T::is_type_of(object)
125 }
126}
127