pythonx/c_src/pythonx/python.hpp at main · princemaple/pythonx · GitHub

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#pragma once

#include <string>

// ssize_t is non-standard, for MSVC we need to define it

#if defined(_MSC_VER)

#include <BaseTsd.h>

using ssize_t = SSIZE_T;

#endif

namespace pythonx::python {

// We only use the Limited C API, which stays compatible across Python

// minor versions. At the moment we assume Python 3.10+, the list of

// available functions can be found in [1].

// Other than the C API functions, we also use Python standard library

// functions via PyObject_Call. This is fine as long as the functions

// are present in the lowest supported Python version and seem stable

// (in particular, they are not deprecated). Keep in mind that the

// C API should be preferred when possible, since invoking lower level

// operations directly should be more efficient in most cases.

// Note that we manage the library manually with `dlopen`, instead of

// linking at compile time and loading together with the NIF lib. This

// makes the development slightly more annoying, since we need to

// declare and load the individual symbols ourselves, however it makes

// the overall setup more flexible:

// 1. We want the Python library location to be configured by the

// user. We could do that by: (a) making sure the NIF library

// depends on a relative libpython.so/python.dll; (b) at runtime,

// symlink or copy the configured Python library at that relative

// location; (c) load the NIF only after symlink is in place,

// rather than upfront. Step (a) requires patching the .so/.dll

// differently on each platform; on Windows this requires compiling

// and attaching and extra manifest to the .dll. With `dlopen` we

// can simply use the configured path.

// 2. It prevents from accidentally using symbols out of Limited API.

// Technically setting Py_LIMITED_API hides a subset of function

// declarations, but there are at least certain macros that stay

// visible. By adding the symbols manually, we can make sure they

// are indeed part of the Limited API.

// 3. If necessary, we could conditionally use functions added to

// Limited API in later versions and have fallback implementations.

// 4. Compiling the NIF does not require Python at all, which makes

// it simpler. Though the main tradeoff is not being able to use

// the Python library headers.

// 5. After uninitializing Python, we should be able to unload the

// library, though there may not be an actual use case to make

// this relevant. It is also worth noting that, while in principle

// it should be possible to reinitialize Python, it can lead to

// issues in practice. For example, doing so while using numpy

// simply does not work, see [2] for discussion points.

// [1]: https://docs.python.org/3.10/c-api/stable.html#stable-abi-list

// [2]: https://bugs.python.org/issue34309

// Opaque types

using PyObjectPtr = void *;

using PyThreadStatePtr = void *;

using PyGILState_STATE = unsigned char;

using Py_ssize_t = ssize_t;

// Functions

extern PyObjectPtr (*PyBool_FromLong)(long int);

extern int (*PyBytes_AsStringAndSize)(PyObjectPtr, char **, Py_ssize_t *);

extern PyObjectPtr (*PyBytes_FromStringAndSize)(const char *, Py_ssize_t);

extern PyObjectPtr (*PyDict_Copy)(PyObjectPtr);

extern PyObjectPtr (*PyDict_GetItem)(PyObjectPtr, PyObjectPtr);

extern PyObjectPtr (*PyDict_GetItemString)(PyObjectPtr, const char *);

extern PyObjectPtr (*PyDict_New)();

extern int (*PyDict_Next)(PyObjectPtr, Py_ssize_t *, PyObjectPtr *,

PyObjectPtr *);

extern int (*PyDict_SetItem)(PyObjectPtr, PyObjectPtr, PyObjectPtr);

extern int (*PyDict_SetItemString)(PyObjectPtr, const char *, PyObjectPtr);

extern Py_ssize_t (*PyDict_Size)(PyObjectPtr);

extern void (*PyErr_Fetch)(PyObjectPtr *, PyObjectPtr *, PyObjectPtr *);

extern PyObjectPtr (*PyErr_Occurred)();

extern PyObjectPtr (*PyEval_GetBuiltins)();

extern PyObjectPtr (*PyEval_EvalCode)(PyObjectPtr, PyObjectPtr, PyObjectPtr);

extern PyThreadStatePtr (*PyEval_SaveThread)();

extern double (*PyFloat_AsDouble)(PyObjectPtr);

extern PyObjectPtr (*PyFloat_FromDouble)(double);

extern PyGILState_STATE (*PyGILState_Ensure)();

extern void (*PyGILState_Release)(PyGILState_STATE);

extern PyObjectPtr (*PyImport_AddModule)(const char *);

extern PyObjectPtr (*PyImport_ImportModule)(const char *);

extern PyObjectPtr (*PyIter_Next)(PyObjectPtr);

extern int (*PyList_Append)(PyObjectPtr, PyObjectPtr);

extern PyObjectPtr (*PyList_GetItem)(PyObjectPtr, Py_ssize_t);

extern PyObjectPtr (*PyList_New)(Py_ssize_t);

extern Py_ssize_t (*PyList_Size)(PyObjectPtr);

extern int (*PyList_SetItem)(PyObjectPtr, Py_ssize_t, PyObjectPtr);

extern long long (*PyLong_AsLongLongAndOverflow)(PyObjectPtr, int *);

extern PyObjectPtr (*PyLong_FromLongLong)(long long);

extern PyObjectPtr (*PyLong_FromString)(const char *, char **, int);

extern PyObjectPtr (*PyLong_FromUnsignedLongLong)(unsigned long long);

extern PyObjectPtr (*PyModule_GetDict)(PyObjectPtr);

extern PyObjectPtr (*PyObject_Call)(PyObjectPtr, PyObjectPtr, PyObjectPtr);

extern PyObjectPtr (*PyObject_CallNoArgs)(PyObjectPtr);

extern PyObjectPtr (*PyObject_GetAttrString)(PyObjectPtr, const char *);

extern PyObjectPtr (*PyObject_GetIter)(PyObjectPtr);

extern int (*PyObject_IsInstance)(PyObjectPtr, PyObjectPtr);

extern PyObjectPtr (*PyObject_Repr)(PyObjectPtr);

extern int (*PyObject_SetAttrString)(PyObjectPtr, const char *, PyObjectPtr);

extern PyObjectPtr (*PyObject_Str)(PyObjectPtr);

extern int (*PySet_Add)(PyObjectPtr, PyObjectPtr);

extern PyObjectPtr (*PySet_New)(PyObjectPtr);

extern Py_ssize_t (*PySet_Size)(PyObjectPtr);

extern PyObjectPtr (*PyTuple_GetItem)(PyObjectPtr, Py_ssize_t);

extern PyObjectPtr (*PyTuple_New)(Py_ssize_t);

extern PyObjectPtr (*PyTuple_Pack)(Py_ssize_t, ...);

extern int (*PyTuple_SetItem)(PyObjectPtr, Py_ssize_t, PyObjectPtr);

extern Py_ssize_t (*PyTuple_Size)(PyObjectPtr);

extern const char *(*PyUnicode_AsUTF8AndSize)(PyObjectPtr, Py_ssize_t *);

extern PyObjectPtr (*PyUnicode_FromStringAndSize)(const char *, Py_ssize_t);

extern PyObjectPtr (*Py_BuildValue)(const char *, ...);

extern PyObjectPtr (*Py_CompileString)(const char *, const char *, int);

extern void (*Py_DecRef)(PyObjectPtr);

extern int (*Py_FinalizeEx)();

extern void (*Py_IncRef)(PyObjectPtr);

extern void (*Py_InitializeEx)(int);

extern int (*Py_IsFalse)(PyObjectPtr);

extern int (*Py_IsNone)(PyObjectPtr);

extern int (*Py_IsTrue)(PyObjectPtr);

extern void (*Py_SetPythonHome)(const wchar_t *);

// Opens Python dynamic library at the given path and looks up all

// relevant symbols.

// Raises `std::runtime_error` if loading fails.

void load_python_library(std::string path);

// Closes the Python library.

void unload_python_library();

} // namespace pythonx::python

pythonx/c_src/pythonx/python.hpp at main · princemaple/pythonx · GitHub

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