descriptor_pool.h

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#ifndef GOOGLE_PROTOBUF_PYTHON_CPP_DESCRIPTOR_POOL_H__
#define GOOGLE_PROTOBUF_PYTHON_CPP_DESCRIPTOR_POOL_H__

#include <Python.h>

#include <google/protobuf/stubs/hash.h>
#include <google/protobuf/descriptor.h>

namespace google {
namespace protobuf {
class MessageFactory;

namespace python {

// The (meta) type of all Messages classes.
struct CMessageClass;

// Wraps operations to the global DescriptorPool which contains information
// about all messages and fields.
//
// There is normally one pool per process. We make it a Python object only
// because it contains many Python references.
// TODO(amauryfa): See whether such objects can appear in reference cycles, and
// consider adding support for the cyclic GC.
//
// "Methods" that interacts with this DescriptorPool are in the cdescriptor_pool
// namespace.
typedef struct PyDescriptorPool {
  PyObject_HEAD

  // The C++ pool containing Descriptors.
  DescriptorPool* pool;

  // The C++ pool acting as an underlay. Can be NULL.
  // This pointer is not owned and must stay alive.
  const DescriptorPool* underlay;

  // The C++ descriptor database used to fetch unknown protos. Can be NULL.
  // This pointer is owned.
  const DescriptorDatabase* database;

  // DynamicMessageFactory used to create C++ instances of messages.
  // This object cache the descriptors that were used, so the DescriptorPool
  // needs to get rid of it before it can delete itself.
  //
  // Note: A C++ MessageFactory is different from the Python MessageFactory.
  // The C++ one creates messages, when the Python one creates classes.
  MessageFactory* message_factory;

  // Make our own mapping to retrieve Python classes from C++ descriptors.
  //
  // Descriptor pointers stored here are owned by the DescriptorPool above.
  // Python references to classes are owned by this PyDescriptorPool.
  typedef hash_map<const Descriptor*, CMessageClass*> ClassesByMessageMap;
  ClassesByMessageMap* classes_by_descriptor;

  // Cache the options for any kind of descriptor.
  // Descriptor pointers are owned by the DescriptorPool above.
  // Python objects are owned by the map.
  hash_map<const void*, PyObject*>* descriptor_options;
} PyDescriptorPool;


extern PyTypeObject PyDescriptorPool_Type;

namespace cdescriptor_pool {

// Looks up a message by name.
// Returns a message Descriptor, or NULL if not found.
const Descriptor* FindMessageTypeByName(PyDescriptorPool* self,
                                        const string& name);

// Registers a new Python class for the given message descriptor.
// On error, returns -1 with a Python exception set.
int RegisterMessageClass(PyDescriptorPool* self,
                         const Descriptor* message_descriptor,
                         CMessageClass* message_class);

// Retrieves the Python class registered with the given message descriptor.
//
// Returns a *borrowed* reference if found, otherwise returns NULL with an
// exception set.
CMessageClass* GetMessageClass(PyDescriptorPool* self,
                               const Descriptor* message_descriptor);

// The functions below are also exposed as methods of the DescriptorPool type.

// Looks up a message by name. Returns a PyMessageDescriptor corresponding to
// the field on success, or NULL on failure.
//
// Returns a new reference.
PyObject* FindMessageByName(PyDescriptorPool* self, PyObject* name);

// Looks up a field by name. Returns a PyFieldDescriptor corresponding to
// the field on success, or NULL on failure.
//
// Returns a new reference.
PyObject* FindFieldByName(PyDescriptorPool* self, PyObject* name);

// Looks up an extension by name. Returns a PyFieldDescriptor corresponding
// to the field on success, or NULL on failure.
//
// Returns a new reference.
PyObject* FindExtensionByName(PyDescriptorPool* self, PyObject* arg);

// Looks up an enum type by name. Returns a PyEnumDescriptor corresponding
// to the field on success, or NULL on failure.
//
// Returns a new reference.
PyObject* FindEnumTypeByName(PyDescriptorPool* self, PyObject* arg);

// Looks up a oneof by name. Returns a COneofDescriptor corresponding
// to the oneof on success, or NULL on failure.
//
// Returns a new reference.
PyObject* FindOneofByName(PyDescriptorPool* self, PyObject* arg);

}  // namespace cdescriptor_pool

// Retrieve the global descriptor pool owned by the _message module.
// This is the one used by pb2.py generated modules.
// Returns a *borrowed* reference.
// "Default" pool used to register messages from _pb2.py modules.
PyDescriptorPool* GetDefaultDescriptorPool();

// Retrieve the python descriptor pool owning a C++ descriptor pool.
// Returns a *borrowed* reference.
PyDescriptorPool* GetDescriptorPool_FromPool(const DescriptorPool* pool);

// Initialize objects used by this module.
bool InitDescriptorPool();

}  // namespace python
}  // namespace protobuf

}  // namespace google
#endif  // GOOGLE_PROTOBUF_PYTHON_CPP_DESCRIPTOR_POOL_H__