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// Copyright (c) 2017-present PyO3 Project and Contributors use crate::err::{PyErr, PyResult}; use crate::gil; use crate::object::PyObject; use crate::objectprotocol::ObjectProtocol; use crate::type_object::{PyBorrowFlagLayout, PyDowncastImpl}; use crate::{ ffi, AsPyPointer, FromPyObject, IntoPy, IntoPyPointer, PyAny, PyCell, PyClass, PyClassInitializer, PyRef, PyRefMut, PyTypeInfo, Python, ToPyObject, }; use std::marker::PhantomData; use std::mem; use std::ptr::NonNull; /// Types that are built into the Python interpreter. /// /// PyO3 is designed in a way that all references to those types are bound /// to the GIL, which is why you can get a token from all references of those /// types. pub unsafe trait PyNativeType: Sized { fn py(&self) -> Python { unsafe { Python::assume_gil_acquired() } } } /// A Python object of known type. /// /// Accessing this object is thread-safe, since any access to its API requires a /// `Python<'py>` GIL token. /// /// See [the guide](https://pyo3.rs/master/types.html) for an explanation /// of the different Python object types. /// /// Technically, it is a safe wrapper around `NonNull<ffi::PyObject>` with /// specified type information. #[derive(Debug)] #[repr(transparent)] pub struct Py<T>(NonNull<ffi::PyObject>, PhantomData<T>); unsafe impl<T> Send for Py<T> {} unsafe impl<T> Sync for Py<T> {} impl<T> Py<T> { /// Create a new instance `Py<T>`. /// /// This method is **soft-duplicated** since PyO3 0.9.0. /// Use [`PyCell::new`](../pycell/struct.PyCell.html#method.new) and /// `Py::from` instead. pub fn new(py: Python, value: impl Into<PyClassInitializer<T>>) -> PyResult<Py<T>> where T: PyClass, T::BaseLayout: PyBorrowFlagLayout<T::BaseType>, { let initializer = value.into(); let obj = unsafe { initializer.create_cell(py)? }; let ob = unsafe { Py::from_owned_ptr(obj as _) }; Ok(ob) } /// Creates a `Py<T>` instance for the given FFI pointer. /// /// This moves ownership over the pointer into the `Py<T>`. /// Undefined behavior if the pointer is NULL or invalid. #[inline] pub unsafe fn from_owned_ptr(ptr: *mut ffi::PyObject) -> Py<T> { debug_assert!( !ptr.is_null() && ffi::Py_REFCNT(ptr) > 0, format!("REFCNT: {:?} - {:?}", ptr, ffi::Py_REFCNT(ptr)) ); Py(NonNull::new_unchecked(ptr), PhantomData) } /// Creates a `Py<T>` instance for the given FFI pointer. /// /// Panics if the pointer is NULL. /// Undefined behavior if the pointer is invalid. #[inline] pub unsafe fn from_owned_ptr_or_panic(ptr: *mut ffi::PyObject) -> Py<T> { match NonNull::new(ptr) { Some(nonnull_ptr) => Py(nonnull_ptr, PhantomData), None => { crate::err::panic_after_error(); } } } /// Construct `Py<T>` from the result of a Python FFI call that /// /// Returns a new reference (owned pointer). /// Returns `Err(PyErr)` if the pointer is NULL. /// Unsafe because the pointer might be invalid. pub unsafe fn from_owned_ptr_or_err(py: Python, ptr: *mut ffi::PyObject) -> PyResult<Py<T>> { match NonNull::new(ptr) { Some(nonnull_ptr) => Ok(Py(nonnull_ptr, PhantomData)), None => Err(PyErr::fetch(py)), } } /// Creates a `Py<T>` instance for the given Python FFI pointer. /// /// Calls `Py_INCREF()` on the ptr. /// Undefined behavior if the pointer is NULL or invalid. #[inline] pub unsafe fn from_borrowed_ptr(ptr: *mut ffi::PyObject) -> Py<T> { debug_assert!( !ptr.is_null() && ffi::Py_REFCNT(ptr) > 0, format!("REFCNT: {:?} - {:?}", ptr, ffi::Py_REFCNT(ptr)) ); ffi::Py_INCREF(ptr); Py(NonNull::new_unchecked(ptr), PhantomData) } /// Gets the reference count of the `ffi::PyObject` pointer. #[inline] pub fn get_refcnt(&self) -> isize { unsafe { ffi::Py_REFCNT(self.0.as_ptr()) } } /// Clones self by calling `Py_INCREF()` on the ptr. #[inline] pub fn clone_ref(&self, _py: Python) -> Py<T> { unsafe { Py::from_borrowed_ptr(self.0.as_ptr()) } } /// Returns the inner pointer without decreasing the refcount. /// /// This will eventually move into its own trait. pub(crate) fn into_non_null(self) -> NonNull<ffi::PyObject> { let pointer = self.0; mem::forget(self); pointer } } /// Retrieves `&'py` types from `Py<T>` or `PyObject`. /// /// # Examples /// `PyObject::as_ref` returns `&PyAny`. /// ``` /// # use pyo3::prelude::*; /// use pyo3::ObjectProtocol; /// let obj: PyObject = { /// let gil = Python::acquire_gil(); /// let py = gil.python(); /// py.eval("[]", None, None).unwrap().to_object(py) /// }; /// let gil = Python::acquire_gil(); /// let py = gil.python(); /// assert_eq!(obj.as_ref(py).len().unwrap(), 0); // PyAny implements ObjectProtocol /// ``` /// /// `Py<T>::as_ref` returns `&PyDict`, `&PyList` or so for native types, and `&PyCell<T>` /// for `#[pyclass]`. /// ``` /// # use pyo3::prelude::*; /// use pyo3::ObjectProtocol; /// let obj: PyObject = { /// let gil = Python::acquire_gil(); /// let py = gil.python(); /// py.eval("[]", None, None).unwrap().to_object(py) /// }; /// let gil = Python::acquire_gil(); /// let py = gil.python(); /// assert_eq!(obj.as_ref(py).len().unwrap(), 0); // PyAny implements ObjectProtocol /// ``` pub trait AsPyRef: Sized { type Target; /// Return reference to object. fn as_ref(&self, py: Python<'_>) -> &Self::Target; } impl<T> AsPyRef for Py<T> where T: PyTypeInfo, { type Target = T::AsRefTarget; fn as_ref(&self, _py: Python) -> &Self::Target { let any = self as *const Py<T> as *const PyAny; unsafe { PyDowncastImpl::unchecked_downcast(&*any) } } } impl<T> ToPyObject for Py<T> { /// Converts `Py` instance -> PyObject. fn to_object(&self, py: Python) -> PyObject { unsafe { PyObject::from_borrowed_ptr(py, self.as_ptr()) } } } impl<T> IntoPy<PyObject> for Py<T> { /// Converts a `Py` instance to `PyObject`. /// Consumes `self` without calling `Py_DECREF()`. #[inline] fn into_py(self, _py: Python) -> PyObject { unsafe { PyObject::from_not_null(self.into_non_null()) } } } impl<T> AsPyPointer for Py<T> { /// Gets the underlying FFI pointer, returns a borrowed pointer. #[inline] fn as_ptr(&self) -> *mut ffi::PyObject { self.0.as_ptr() } } impl<T> IntoPyPointer for Py<T> { /// Gets the underlying FFI pointer, returns a owned pointer. #[inline] #[must_use] fn into_ptr(self) -> *mut ffi::PyObject { self.into_non_null().as_ptr() } } // Native types `&T` can be converted to `Py<T>` impl<'a, T> std::convert::From<&'a T> for Py<T> where T: AsPyPointer + PyNativeType, { fn from(obj: &'a T) -> Self { unsafe { Py::from_borrowed_ptr(obj.as_ptr()) } } } // `&PyCell<T>` can be converted to `Py<T>` impl<'a, T> std::convert::From<&PyCell<T>> for Py<T> where T: PyClass, { fn from(cell: &PyCell<T>) -> Self { unsafe { Py::from_borrowed_ptr(cell.as_ptr()) } } } impl<'a, T> std::convert::From<PyRef<'a, T>> for Py<T> where T: PyClass, { fn from(pyref: PyRef<'a, T>) -> Self { unsafe { Py::from_borrowed_ptr(pyref.as_ptr()) } } } impl<'a, T> std::convert::From<PyRefMut<'a, T>> for Py<T> where T: PyClass, { fn from(pyref: PyRefMut<'a, T>) -> Self { unsafe { Py::from_borrowed_ptr(pyref.as_ptr()) } } } impl<T> PartialEq for Py<T> { #[inline] fn eq(&self, o: &Py<T>) -> bool { self.0 == o.0 } } /// Dropping a `Py` instance decrements the reference count on the object by 1. impl<T> Drop for Py<T> { fn drop(&mut self) { unsafe { gil::register_pointer(self.0); } } } impl<T> std::convert::From<Py<T>> for PyObject { #[inline] fn from(ob: Py<T>) -> Self { unsafe { PyObject::from_not_null(ob.into_non_null()) } } } impl<'a, T> std::convert::From<&'a T> for PyObject where T: AsPyPointer, { fn from(ob: &'a T) -> Self { unsafe { Py::<T>::from_borrowed_ptr(ob.as_ptr()) }.into() } } impl<'a, T> std::convert::From<&'a mut T> for PyObject where T: AsPyPointer, { fn from(ob: &'a mut T) -> Self { unsafe { Py::<T>::from_borrowed_ptr(ob.as_ptr()) }.into() } } impl<'a, T> FromPyObject<'a> for Py<T> where T: AsPyPointer, &'a T: 'a + FromPyObject<'a>, { /// Extracts `Self` from the source `PyObject`. fn extract(ob: &'a PyAny) -> PyResult<Self> { unsafe { ob.extract::<&T>() .map(|val| Py::from_borrowed_ptr(val.as_ptr())) } } } /// Reference to a converted [ToPyObject]. /// /// Many methods want to take anything that can be converted into a Python object. This type /// takes care of both types types that are already Python object (i.e. implement /// [AsPyPointer]) and those that don't (i.e. [ToPyObject] types). /// For the [AsPyPointer] types, we just use the borrowed pointer, which is a lot faster /// and simpler than creating a new extra object. The remaning [ToPyObject] types are /// converted to Python objects, the owned pointer is stored and decref'd on drop. /// /// # Example /// /// ``` /// use pyo3::ffi; /// use pyo3::{ToPyObject, AsPyPointer, PyNativeType, ManagedPyRef}; /// use pyo3::types::{PyDict, PyAny}; /// /// pub fn get_dict_item<'p>(dict: &'p PyDict, key: &impl ToPyObject) -> Option<&'p PyAny> { /// let key = ManagedPyRef::from_to_pyobject(dict.py(), key); /// unsafe { /// dict.py().from_borrowed_ptr_or_opt(ffi::PyDict_GetItem(dict.as_ptr(), key.as_ptr())) /// } /// } /// ``` #[repr(transparent)] pub struct ManagedPyRef<'p, T: ToPyObject + ?Sized> { data: *mut ffi::PyObject, data_type: PhantomData<T>, _py: Python<'p>, } /// This should eventually be replaced with a generic `IntoPy` trait impl by figuring /// out the correct lifetime annotation to make the compiler happy. impl<'p, T: ToPyObject> ManagedPyRef<'p, T> { pub fn from_to_pyobject(py: Python<'p>, to_pyobject: &T) -> Self { to_pyobject.to_managed_py_ref(py) } } impl<'p, T: ToPyObject> AsPyPointer for ManagedPyRef<'p, T> { fn as_ptr(&self) -> *mut ffi::PyObject { self.data } } /// Helper trait to choose the right implementation for [ManagedPyRef]. pub trait ManagedPyRefDispatch: ToPyObject { /// Optionally converts into a Python object and stores the pointer to the python heap. fn to_managed_py_ref<'p>(&self, py: Python<'p>) -> ManagedPyRef<'p, Self>; /// Dispatch over a xdecref and a noop drop impl fn drop_impl(borrowed: &mut ManagedPyRef<Self>); } /// Case 1: It's a Rust object which still needs to be converted to a Python object. /// This means we're storing the owned pointer that into_ptr() has given us /// and therefore need to xdecref when we're done. /// /// Note that the actual implementations are part of the trait declaration to avoid /// a specialization error impl<T: ToPyObject + ?Sized> ManagedPyRefDispatch for T { /// Contains the case 1 impl (with to_object) to avoid a specialization error default fn to_managed_py_ref<'p>(&self, py: Python<'p>) -> ManagedPyRef<'p, Self> { ManagedPyRef { data: self.to_object(py).into_ptr(), data_type: PhantomData, _py: py, } } /// Contains the case 1 impl (decref) to avoid a specialization error default fn drop_impl(borrowed: &mut ManagedPyRef<Self>) { unsafe { ffi::Py_DECREF(borrowed.data) }; } } /// Case 2: It's an object on the Python heap, we're just storing a borrowed pointer. /// The object we're getting is an owned pointer, it might have it's own drop impl. impl<T: ToPyObject + AsPyPointer + ?Sized> ManagedPyRefDispatch for T { /// Use AsPyPointer to copy the pointer and store it as borrowed pointer fn to_managed_py_ref<'p>(&self, py: Python<'p>) -> ManagedPyRef<'p, Self> { ManagedPyRef { data: self.as_ptr(), data_type: PhantomData, _py: py, } } /// We have a borrowed pointer, so nothing to do here fn drop_impl(_: &mut ManagedPyRef<T>) {} } impl<'p, T: ToPyObject + ?Sized> Drop for ManagedPyRef<'p, T> { /// Uses the internal [ManagedPyRefDispatch] trait to get the right drop impl without causing /// a specialization error fn drop(&mut self) { ManagedPyRefDispatch::drop_impl(self); } } #[cfg(test)] mod test { use super::{ManagedPyRef, Py}; use crate::ffi; use crate::types::PyDict; use crate::{AsPyPointer, Python}; #[test] fn py_from_dict() { let dict = { let gil = Python::acquire_gil(); let py = gil.python(); let native = PyDict::new(py); Py::from(native) }; assert_eq!(unsafe { ffi::Py_REFCNT(dict.as_ptr()) }, 1); } #[test] fn borrowed_py_ref_with_to_pointer() { let gil = Python::acquire_gil(); let py = gil.python(); let native = PyDict::new(py); let ref_count = unsafe { ffi::Py_REFCNT(native.as_ptr()) }; let borrowed = ManagedPyRef::from_to_pyobject(py, native); assert_eq!(native.as_ptr(), borrowed.data); assert_eq!(ref_count, unsafe { ffi::Py_REFCNT(borrowed.data) }); drop(borrowed); assert_eq!(ref_count, unsafe { ffi::Py_REFCNT(native.as_ptr()) }); } #[test] fn borrowed_py_ref_with_to_object() { let gil = Python::acquire_gil(); let py = gil.python(); let convertible = (1, 2, 3); let borrowed = ManagedPyRef::from_to_pyobject(py, &convertible); let ptr = borrowed.data; // The refcountwould become 0 after dropping, which means the gc can free the pointer // and getting the refcount would be UB. This incref ensures that it remains 1 unsafe { ffi::Py_INCREF(ptr); } assert_eq!(2, unsafe { ffi::Py_REFCNT(ptr) }); drop(borrowed); assert_eq!(1, unsafe { ffi::Py_REFCNT(ptr) }); unsafe { ffi::Py_DECREF(ptr); } } }