protobuf/python/protobuf.h

/*
 * Copyright (c) 2009-2021, Google LLC
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 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of Google LLC nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 */

#ifndef PYUPB_PROTOBUF_H__
#define PYUPB_PROTOBUF_H__

#include <stdbool.h>

#include "python/descriptor.h"
#include "python/python.h"
#include "upb/table_internal.h"

#define PYUPB_MODULE_NAME "google.protobuf.pyext._message"

#define PYUPB_RETURN_OOM return PyErr_SetNone(PyExc_MemoryError), NULL

struct PyUpb_WeakMap;
typedef struct PyUpb_WeakMap PyUpb_WeakMap;

// -----------------------------------------------------------------------------
// ModuleState
// -----------------------------------------------------------------------------

// We store all "global" state in this struct instead of using (C) global
// variables. This makes this extension compatible with sub-interpreters.

typedef struct {
  // From descriptor.c
  PyTypeObject *descriptor_types[kPyUpb_Descriptor_Count];

  // From descriptor_containers.c
  PyTypeObject *by_name_map_type;
  PyTypeObject *by_number_map_type;
  PyTypeObject *descriptor_iterator_type;
  PyTypeObject *generic_sequence_type;

  // From descriptor_pool.c
  PyObject *default_pool;

  // From descriptor_pool.c
  PyTypeObject *descriptor_pool_type;

  // From map.c
  PyTypeObject* map_iterator_type;
  PyTypeObject* message_map_container_type;
  PyTypeObject* scalar_map_container_type;

  // From message.c
  PyObject *decode_error_class;
  PyObject* descriptor_string;
  PyObject *encode_error_class;
  PyObject *enum_type_wrapper_class;
  PyObject *message_class;
  PyTypeObject *cmessage_type;
  PyTypeObject *message_meta_type;

  // From protobuf.c
  PyObject *wkt_bases;
  PyTypeObject *arena_type;
  PyUpb_WeakMap *obj_cache;

  // From repeated.c
  PyTypeObject* repeated_composite_container_type;
  PyTypeObject* repeated_scalar_container_type;
} PyUpb_ModuleState;

// Returns the global state object from the current interpreter. The current
// interpreter is looked up from thread-local state.
PyUpb_ModuleState *PyUpb_ModuleState_Get(void);
PyUpb_ModuleState *PyUpb_ModuleState_GetFromModule(PyObject *module);

// Returns NULL if module state is not yet available (during startup).
// Any use of the module state during startup needs to be passed explicitly.
PyUpb_ModuleState* PyUpb_ModuleState_MaybeGet(void);

// Returns:
//   from google.protobuf.internal.well_known_types import WKTBASES
//
// This has to be imported lazily rather than at module load time, because
// otherwise it would cause a circular import.
PyObject *PyUpb_GetWktBases(PyUpb_ModuleState *state);

// -----------------------------------------------------------------------------
// WeakMap
// -----------------------------------------------------------------------------

// A WeakMap maps C pointers to the corresponding Python wrapper object. We
// want a consistent Python wrapper object for each C object, both to save
// memory and to provide object stability (ie. x is x).
//
// Each wrapped object should add itself to the map when it is constructed and
// remove itself from the map when it is destroyed. The map is weak so it does
// not take references to the cached objects.

PyUpb_WeakMap *PyUpb_WeakMap_New(void);
void PyUpb_WeakMap_Free(PyUpb_WeakMap *map);

// Adds the given object to the map, indexed by the given key.
void PyUpb_WeakMap_Add(PyUpb_WeakMap *map, const void *key, PyObject *py_obj);

// Removes the given key from the cache. It must exist in the cache currently.
void PyUpb_WeakMap_Delete(PyUpb_WeakMap *map, const void *key);
void PyUpb_WeakMap_TryDelete(PyUpb_WeakMap *map, const void *key);

// Returns a new reference to an object if it exists, otherwise returns NULL.
PyObject *PyUpb_WeakMap_Get(PyUpb_WeakMap *map, const void *key);

#define PYUPB_WEAKMAP_BEGIN UPB_INTTABLE_BEGIN

// Iteration over the weak map, eg.
//
// intptr_t it = PYUPB_WEAKMAP_BEGIN;
// while (PyUpb_WeakMap_Next(map, &key, &obj, &it)) {
//   // ...
// }
//
// Note that the callee does not own a ref on the returned `obj`.
bool PyUpb_WeakMap_Next(PyUpb_WeakMap *map, const void **key, PyObject **obj,
                        intptr_t *iter);
void PyUpb_WeakMap_DeleteIter(PyUpb_WeakMap *map, intptr_t *iter);

// -----------------------------------------------------------------------------
// ObjCache
// -----------------------------------------------------------------------------

// The object cache is a global WeakMap for mapping upb objects to the
// corresponding wrapper.
void PyUpb_ObjCache_Add(const void *key, PyObject *py_obj);
void PyUpb_ObjCache_Delete(const void *key);
PyObject *PyUpb_ObjCache_Get(const void *key);  // returns NULL if not present.
PyUpb_WeakMap *PyUpb_ObjCache_Instance(void);

// -----------------------------------------------------------------------------
// Arena
// -----------------------------------------------------------------------------

PyObject *PyUpb_Arena_New(void);
upb_arena *PyUpb_Arena_Get(PyObject *arena);

// -----------------------------------------------------------------------------
// Utilities
// -----------------------------------------------------------------------------

PyTypeObject *AddObject(PyObject *m, const char *name, PyType_Spec *spec);

// Creates a Python type from `spec` and adds it to the given module `m`.
PyTypeObject *PyUpb_AddClass(PyObject *m, PyType_Spec *spec);

// Like PyUpb_AddClass(), but allows you to specify a tuple of base classes
// in `bases`.
PyTypeObject* PyUpb_AddClassWithBases(PyObject* m, PyType_Spec* spec,
                                      PyObject* bases);

// A function that implements the tp_new slot for types that we do not allow
// users to create directly. This will immediately fail with an error message.
PyObject *PyUpb_Forbidden_New(PyObject *cls, PyObject *args, PyObject *kwds);

// Our standard dealloc func. It follows the guidance defined in:
//   https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_dealloc
// However it tests Py_TPFLAGS_HEAPTYPE dynamically so that a single dealloc
// function can work for any type.
static inline void PyUpb_Dealloc(void *self) {
  PyTypeObject *tp = Py_TYPE(self);
  freefunc tp_free = PyType_GetSlot(tp, Py_tp_free);
  tp_free(self);
  if (PyType_GetFlags(tp) & Py_TPFLAGS_HEAPTYPE) {
    Py_DECREF(tp);
  }
}

// Equivalent to the Py_NewRef() function introduced in Python 3.10.  If/when we
// drop support for Python <3.10, we can remove this function and replace all
// callers with Py_NewRef().
static inline PyObject *PyUpb_NewRef(PyObject *obj) {
  Py_INCREF(obj);
  return obj;
}

const char *PyUpb_GetStrData(PyObject *obj);

#endif  // PYUPB_PROTOBUF_H__