# Protocol Buffers - Google's data interchange format
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# https://developers.google.com/protocol-buffers/
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"""A database of Python protocol buffer generated symbols.
SymbolDatabase is the MessageFactory for messages generated at compile time,
and makes it easy to create new instances of a registered type, given only the
type's protocol buffer symbol name.
Example usage:
db = symbol_database.SymbolDatabase()
# Register symbols of interest, from one or multiple files.
db.RegisterFileDescriptor(my_proto_pb2.DESCRIPTOR)
db.RegisterMessage(my_proto_pb2.MyMessage)
db.RegisterEnumDescriptor(my_proto_pb2.MyEnum.DESCRIPTOR)
# The database can be used as a MessageFactory, to generate types based on
# their name:
types = db.GetMessages(['my_proto.proto'])
my_message_instance = types['MyMessage']()
# The database's underlying descriptor pool can be queried, so it's not
# necessary to know a type's filename to be able to generate it:
filename = db.pool.FindFileContainingSymbol('MyMessage')
my_message_instance = db.GetMessages([filename])['MyMessage']()
# This functionality is also provided directly via a convenience method:
my_message_instance = db.GetSymbol('MyMessage')()
"""
from google.protobuf import descriptor_pool
from google.protobuf import message_factory
class SymbolDatabase(message_factory.MessageFactory):
"""A database of Python generated symbols."""
def RegisterMessage(self, message):
"""Registers the given message type in the local database.
Calls to GetSymbol() and GetMessages() will return messages registered here.
Args:
message: a message.Message, to be registered.
Returns:
The provided message.
"""
desc = message.DESCRIPTOR
self._classes[desc] = message
self.RegisterMessageDescriptor(desc)
return message
def RegisterMessageDescriptor(self, message_descriptor):
"""Registers the given message descriptor in the local database.
Args:
message_descriptor: a descriptor.MessageDescriptor.
"""
self.pool.AddDescriptor(message_descriptor)
def RegisterEnumDescriptor(self, enum_descriptor):
"""Registers the given enum descriptor in the local database.
Args:
enum_descriptor: a descriptor.EnumDescriptor.
Returns:
The provided descriptor.
"""
self.pool.AddEnumDescriptor(enum_descriptor)
return enum_descriptor
def RegisterServiceDescriptor(self, service_descriptor):
"""Registers the given service descriptor in the local database.
Args:
service_descriptor: a descriptor.ServiceDescriptor.
Returns:
The provided descriptor.
"""
self.pool.AddServiceDescriptor(service_descriptor)
def RegisterFileDescriptor(self, file_descriptor):
"""Registers the given file descriptor in the local database.
Args:
file_descriptor: a descriptor.FileDescriptor.
Returns:
The provided descriptor.
"""
self.pool.AddFileDescriptor(file_descriptor)
def GetSymbol(self, symbol):
"""Tries to find a symbol in the local database.
Currently, this method only returns message.Message instances, however, if
may be extended in future to support other symbol types.
Args:
symbol: A str, a protocol buffer symbol.
Returns:
A Python class corresponding to the symbol.
Raises:
KeyError: if the symbol could not be found.
"""
return self._classes[self.pool.FindMessageTypeByName(symbol)]
def GetMessages(self, files):
# TODO(amauryfa): Fix the differences with MessageFactory.
"""Gets all registered messages from a specified file.
Only messages already created and registered will be returned; (this is the
case for imported _pb2 modules)
But unlike MessageFactory, this version also returns already defined nested
messages, but does not register any message extensions.
Args:
files: The file names to extract messages from.
Returns:
A dictionary mapping proto names to the message classes.
Raises:
KeyError: if a file could not be found.
"""
def _GetAllMessages(desc):
"""Walk a message Descriptor and recursively yields all message names."""
yield desc
for msg_desc in desc.nested_types:
for nested_desc in _GetAllMessages(msg_desc):
yield nested_desc
result = {}
for file_name in files:
file_desc = self.pool.FindFileByName(file_name)
for msg_desc in file_desc.message_types_by_name.values():
for desc in _GetAllMessages(msg_desc):
try:
result[desc.full_name] = self._classes[desc]
except KeyError:
# This descriptor has no registered class, skip it.
pass
return result
_DEFAULT = SymbolDatabase(pool=descriptor_pool.Default())
def Default():
"""Returns the default SymbolDatabase."""
return _DEFAULT
