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LSSTDataManagementBasePackage
PySharedPtr.h
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1 // -*- lsst-c++ -*-
2 /*
3  * LSST Data Management System
4  * See COPYRIGHT file at the top of the source tree.
5  *
6  * This product includes software developed by the
7  * LSST Project (http://www.lsst.org/).
8  *
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23 
24 #ifndef LSST_UTILS_PYTHON_PYSHAREDPTR_H
25 #define LSST_UTILS_PYTHON_PYSHAREDPTR_H
26 
27 #include "pybind11/pybind11.h"
28 
29 #include <memory>
30 
31 namespace lsst {
32 namespace utils {
33 namespace python {
34 
35 /* Workaround for C++ objects outliving Python objects
36  * by Xfel and florianwechsung, https://github.com/pybind/pybind11/issues/1389
37  */
48 template <typename T>
49 class PySharedPtr final {
50 public:
51  using element_type = T;
52 
59  explicit PySharedPtr(T* const ptr) : _impl() {
60  if (ptr != nullptr) {
61  // `cast` returns new PyObject only if `*ptr` not yet associated with one
62  PyObject* pyObj = pybind11::cast(ptr).ptr();
63  Py_INCREF(pyObj);
64  // if any operation with shared_ptr fails, pyObj will get decremented correctly
65  std::shared_ptr<PyObject> manager(pyObj, [](PyObject* const obj) noexcept {
66  if (obj != nullptr) Py_DECREF(obj);
67  });
68  _impl = std::shared_ptr<T>(manager, ptr);
69  }
70  }
71 
72  PySharedPtr(PySharedPtr const&) noexcept = default;
73  PySharedPtr(PySharedPtr&&) noexcept = default;
74  PySharedPtr& operator=(PySharedPtr const&) noexcept = default;
75  PySharedPtr& operator=(PySharedPtr&&) noexcept = default;
76  ~PySharedPtr() noexcept = default;
77 
78  PySharedPtr(std::shared_ptr<T> r) noexcept : _impl(std::move(r)) {}
79  operator std::shared_ptr<T>() noexcept { return _impl; }
80 
81  T* get() const noexcept { return _impl.get(); }
82 
83 private:
84  std::shared_ptr<T> _impl;
85 };
86 
87 } // namespace python
88 } // namespace utils
89 } // namespace lsst
90 
91 // Macro must be called in the global namespace
93 
94 #endif
uint64_t * ptr
Definition: RangeSet.cc:88
~PySharedPtr() noexcept=default
PySharedPtr & operator=(PySharedPtr const &) noexcept=default
A base class for image defects.
T move(T... args)
T get(T... args)
PySharedPtr(T *const ptr)
Create a pointer that counts as an extra reference in the Python environment.
Definition: PySharedPtr.h:59
PySharedPtr(std::shared_ptr< T > r) noexcept
Definition: PySharedPtr.h:78
PYBIND11_DECLARE_HOLDER_TYPE(T, lsst::utils::python::PySharedPtr< T >)
A shared pointer that tracks both a C++ object and its associated PyObject.
Definition: PySharedPtr.h:49