protobuf/python/descriptor_containers.h

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#ifndef PYUPB_DESCRIPTOR_CONTAINERS_H__
#define PYUPB_DESCRIPTOR_CONTAINERS_H__

// This file defines immutable Python containiner types whose data comes from
// an underlying descriptor (def).
//
// Because there are many instances of these types that vend different kinds of
// data (fields, oneofs, enums, etc) these types accept a "vtable" of function
// pointers. This saves us from having to define numerous distinct Python types
// for each kind of data we want to vend.
//
// The underlying upb APIs follow a consistent pattern that allows us to use
// those functions directly inside these vtables, greatly reducing the amount of
// "adaptor" code we need to write.

#include <stdbool.h>

#include "upb/def.h"

#include "protobuf.h"

// -----------------------------------------------------------------------------
// PyUpb_GenericSequence
// -----------------------------------------------------------------------------

// A Python object that vends a sequence of descriptors.

typedef struct {
  // Returns the number of elements in the map.
  int (*get_elem_count)(const void *parent);
  // Returns an element by index.
  const void *(*index)(const void *parent, int idx);
  // Returns a Python object wrapping this element, caller owns a ref.
  PyObject *(*get_elem_wrapper)(const void *elem);
} PyUpb_GenericSequence_Funcs;

// Returns a new GenericSequence.  The vtable `funcs` must outlive this object
// (generally it should be static).  The GenericSequence will take a ref on
// `parent_obj`, which must be sufficient to keep `parent` alive.  The object
// `parent` will be passed as an argument to the functions in `funcs`.
PyObject *PyUpb_GenericSequence_New(const PyUpb_GenericSequence_Funcs *funcs,
                                    const void *parent, PyObject *parent_obj);

// -----------------------------------------------------------------------------
// PyUpb_ByNameMap
// -----------------------------------------------------------------------------

// A Python object that vends a name->descriptor map.

typedef struct {
  PyUpb_GenericSequence_Funcs base;
  // Looks up by name and returns either a pointer to the element or NULL.
  const void *(*lookup)(const void *parent, const char *key);
  // Returns the name associated with this element.
  const char *(*get_elem_name)(const void *elem);
} PyUpb_ByNameMap_Funcs;

// Returns a new ByNameMap.  The vtable `funcs` must outlive this object
// (generally it should be static).  The ByNameMap will take a ref on
// `parent_obj`, which must be sufficient to keep `parent` alive.  The object
// `parent` will be passed as an argument to the functions in `funcs`.
PyObject *PyUpb_ByNameMap_New(const PyUpb_ByNameMap_Funcs *funcs,
                              const void *parent, PyObject *parent_obj);

// -----------------------------------------------------------------------------
// PyUpb_ByNumberMap
// -----------------------------------------------------------------------------

// A Python object that vends a number->descriptor map.

typedef struct {
  PyUpb_GenericSequence_Funcs base;
  // Looks up by name and returns either a pointer to the element or NULL.
  const void *(*lookup)(const void *parent, int num);
  // Returns the name associated with this element.
  int (*get_elem_num)(const void *elem);
} PyUpb_ByNumberMap_Funcs;

// Returns a new ByNumberMap.  The vtable `funcs` must outlive this object
// (generally it should be static).  The ByNumberMap will take a ref on
// `parent_obj`, which must be sufficient to keep `parent` alive.  The object
// `parent` will be passed as an argument to the functions in `funcs`.
PyObject *PyUpb_ByNumberMap_New(const PyUpb_ByNumberMap_Funcs *funcs,
                                const void *parent, PyObject *parent_obj);

bool PyUpb_InitDescriptorContainers(PyObject* m);

#endif   // PYUPB_DESCRIPTOR_CONTAINERS_H__