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#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""Provides DescriptorPool to use as a container for proto2 descriptors.
The DescriptorPool is used in conjection with a DescriptorDatabase to maintain
a collection of protocol buffer descriptors for use when dynamically creating
message types at runtime.
For most applications protocol buffers should be used via modules generated by
the protocol buffer compiler tool. This should only be used when the type of
protocol buffers used in an application or library cannot be predetermined.
Below is a straightforward example on how to use this class:
pool = DescriptorPool()
file_descriptor_protos = [ ... ]
for file_descriptor_proto in file_descriptor_protos:
pool.Add(file_descriptor_proto)
my_message_descriptor = pool.FindMessageTypeByName('some.package.MessageType')
The message descriptor can be used in conjunction with the message_factory
module in order to create a protocol buffer class that can be encoded and
decoded.
If you want to get a Python class for the specified proto, use the
helper functions inside google.net.proto2.python.public.message_factory
directly instead of this class.
"""
import sys
from google.net.proto2.python.public import descriptor
from google.net.proto2.python.public import descriptor_database
from google.net.proto2.python.public import text_encoding
def _NormalizeFullyQualifiedName(name):
"""Remove leading period from fully-qualified type name.
Due to b/13860351 in descriptor_database.py, types in the root namespace are
generated with a leading period. This function removes that prefix.
Args:
name: A str, the fully-qualified symbol name.
Returns:
A str, the normalized fully-qualified symbol name.
"""
return name.lstrip('.')
class DescriptorPool(object):
"""A collection of protobufs dynamically constructed by descriptor protos."""
def __init__(self, descriptor_db=None):
"""Initializes a Pool of proto buffs.
The descriptor_db argument to the constructor is provided to allow
specialized file descriptor proto lookup code to be triggered on demand. An
example would be an implementation which will read and compile a file
specified in a call to FindFileByName() and not require the call to Add()
at all. Results from this database will be cached internally here as well.
Args:
descriptor_db: A secondary source of file descriptors.
"""
self._internal_db = descriptor_database.DescriptorDatabase()
self._descriptor_db = descriptor_db
self._descriptors = {}
self._enum_descriptors = {}
self._file_descriptors = {}
def Add(self, file_desc_proto):
"""Adds the FileDescriptorProto and its types to this pool.
Args:
file_desc_proto: The FileDescriptorProto to add.
"""
self._internal_db.Add(file_desc_proto)
def AddDescriptor(self, desc):
"""Adds a Descriptor to the pool, non-recursively.
If the Descriptor contains nested messages or enums, the caller must
explicitly register them. This method also registers the FileDescriptor
associated with the message.
Args:
desc: A Descriptor.
"""
if not isinstance(desc, descriptor.Descriptor):
raise TypeError('Expected instance of descriptor.Descriptor.')
self._descriptors[desc.full_name] = desc
self.AddFileDescriptor(desc.file)
def AddEnumDescriptor(self, enum_desc):
"""Adds an EnumDescriptor to the pool.
This method also registers the FileDescriptor associated with the message.
Args:
enum_desc: An EnumDescriptor.
"""
if not isinstance(enum_desc, descriptor.EnumDescriptor):
raise TypeError('Expected instance of descriptor.EnumDescriptor.')
self._enum_descriptors[enum_desc.full_name] = enum_desc
self.AddFileDescriptor(enum_desc.file)
def AddFileDescriptor(self, file_desc):
"""Adds a FileDescriptor to the pool, non-recursively.
If the FileDescriptor contains messages or enums, the caller must explicitly
register them.
Args:
file_desc: A FileDescriptor.
"""
if not isinstance(file_desc, descriptor.FileDescriptor):
raise TypeError('Expected instance of descriptor.FileDescriptor.')
self._file_descriptors[file_desc.name] = file_desc
def FindFileByName(self, file_name):
"""Gets a FileDescriptor by file name.
Args:
file_name: The path to the file to get a descriptor for.
Returns:
A FileDescriptor for the named file.
Raises:
KeyError: if the file can not be found in the pool.
"""
try:
return self._file_descriptors[file_name]
except KeyError:
pass
try:
file_proto = self._internal_db.FindFileByName(file_name)
except KeyError:
_, error, _ = sys.exc_info()
if self._descriptor_db:
file_proto = self._descriptor_db.FindFileByName(file_name)
else:
raise error
if not file_proto:
raise KeyError('Cannot find a file named %s' % file_name)
return self._ConvertFileProtoToFileDescriptor(file_proto)
def FindFileContainingSymbol(self, symbol):
"""Gets the FileDescriptor for the file containing the specified symbol.
Args:
symbol: The name of the symbol to search for.
Returns:
A FileDescriptor that contains the specified symbol.
Raises:
KeyError: if the file can not be found in the pool.
"""
symbol = _NormalizeFullyQualifiedName(symbol)
try:
return self._descriptors[symbol].file
except KeyError:
pass
try:
return self._enum_descriptors[symbol].file
except KeyError:
pass
try:
file_proto = self._internal_db.FindFileContainingSymbol(symbol)
except KeyError:
_, error, _ = sys.exc_info()
if self._descriptor_db:
file_proto = self._descriptor_db.FindFileContainingSymbol(symbol)
else:
raise error
if not file_proto:
raise KeyError('Cannot find a file containing %s' % symbol)
return self._ConvertFileProtoToFileDescriptor(file_proto)
def FindMessageTypeByName(self, full_name):
"""Loads the named descriptor from the pool.
Args:
full_name: The full name of the descriptor to load.
Returns:
The descriptor for the named type.
"""
full_name = _NormalizeFullyQualifiedName(full_name)
if full_name not in self._descriptors:
self.FindFileContainingSymbol(full_name)
return self._descriptors[full_name]
def FindEnumTypeByName(self, full_name):
"""Loads the named enum descriptor from the pool.
Args:
full_name: The full name of the enum descriptor to load.
Returns:
The enum descriptor for the named type.
"""
full_name = _NormalizeFullyQualifiedName(full_name)
if full_name not in self._enum_descriptors:
self.FindFileContainingSymbol(full_name)
return self._enum_descriptors[full_name]
def _ConvertFileProtoToFileDescriptor(self, file_proto):
"""Creates a FileDescriptor from a proto or returns a cached copy.
This method also has the side effect of loading all the symbols found in
the file into the appropriate dictionaries in the pool.
Args:
file_proto: The proto to convert.
Returns:
A FileDescriptor matching the passed in proto.
"""
if file_proto.name not in self._file_descriptors:
built_deps = list(self._GetDeps(file_proto.dependency))
direct_deps = [self.FindFileByName(n) for n in file_proto.dependency]
file_descriptor = descriptor.FileDescriptor(
name=file_proto.name,
package=file_proto.package,
options=file_proto.options,
serialized_pb=file_proto.SerializeToString(),
dependencies=direct_deps)
scope = {}
for dependency in built_deps:
scope.update(self._ExtractSymbols(
dependency.message_types_by_name.values()))
scope.update((_PrefixWithDot(enum.full_name), enum)
for enum in dependency.enum_types_by_name.values())
for message_type in file_proto.message_type:
message_desc = self._ConvertMessageDescriptor(
message_type, file_proto.package, file_descriptor, scope)
file_descriptor.message_types_by_name[message_desc.name] = message_desc
for enum_type in file_proto.enum_type:
file_descriptor.enum_types_by_name[enum_type.name] = (
self._ConvertEnumDescriptor(enum_type, file_proto.package,
file_descriptor, None, scope))
for index, extension_proto in enumerate(file_proto.extension):
extension_desc = self.MakeFieldDescriptor(
extension_proto, file_proto.package, index, is_extension=True)
extension_desc.containing_type = self._GetTypeFromScope(
file_descriptor.package, extension_proto.extendee, scope)
self.SetFieldType(extension_proto, extension_desc,
file_descriptor.package, scope)
file_descriptor.extensions_by_name[extension_desc.name] = extension_desc
for desc_proto in file_proto.message_type:
self.SetAllFieldTypes(file_proto.package, desc_proto, scope)
if file_proto.package:
desc_proto_prefix = _PrefixWithDot(file_proto.package)
else:
desc_proto_prefix = ''
for desc_proto in file_proto.message_type:
desc = self._GetTypeFromScope(desc_proto_prefix, desc_proto.name, scope)
file_descriptor.message_types_by_name[desc_proto.name] = desc
self.Add(file_proto)
self._file_descriptors[file_proto.name] = file_descriptor
return self._file_descriptors[file_proto.name]
def _ConvertMessageDescriptor(self, desc_proto, package=None, file_desc=None,
scope=None):
"""Adds the proto to the pool in the specified package.
Args:
desc_proto: The descriptor_pb2.DescriptorProto protobuf message.
package: The package the proto should be located in.
file_desc: The file containing this message.
scope: Dict mapping short and full symbols to message and enum types.
Returns:
The added descriptor.
"""
if package:
desc_name = '.'.join((package, desc_proto.name))
else:
desc_name = desc_proto.name
if file_desc is None:
file_name = None
else:
file_name = file_desc.name
if scope is None:
scope = {}
nested = [
self._ConvertMessageDescriptor(nested, desc_name, file_desc, scope)
for nested in desc_proto.nested_type]
enums = [
self._ConvertEnumDescriptor(enum, desc_name, file_desc, None, scope)
for enum in desc_proto.enum_type]
fields = [self.MakeFieldDescriptor(field, desc_name, index)
for index, field in enumerate(desc_proto.field)]
extensions = [
self.MakeFieldDescriptor(extension, desc_name, index, is_extension=True)
for index, extension in enumerate(desc_proto.extension)]
oneofs = [
descriptor.OneofDescriptor(desc.name, '.'.join((desc_name, desc.name)),
index, None, [])
for index, desc in enumerate(desc_proto.oneof_decl)]
extension_ranges = [(r.start, r.end) for r in desc_proto.extension_range]
if extension_ranges:
is_extendable = True
else:
is_extendable = False
desc = descriptor.Descriptor(
name=desc_proto.name,
full_name=desc_name,
filename=file_name,
containing_type=None,
fields=fields,
oneofs=oneofs,
nested_types=nested,
enum_types=enums,
extensions=extensions,
options=desc_proto.options,
is_extendable=is_extendable,
extension_ranges=extension_ranges,
file=file_desc,
serialized_start=None,
serialized_end=None)
for nested in desc.nested_types:
nested.containing_type = desc
for enum in desc.enum_types:
enum.containing_type = desc
for field_index, field_desc in enumerate(desc_proto.field):
if field_desc.HasField('oneof_index'):
oneof_index = field_desc.oneof_index
oneofs[oneof_index].fields.append(fields[field_index])
fields[field_index].containing_oneof = oneofs[oneof_index]
scope[_PrefixWithDot(desc_name)] = desc
self._descriptors[desc_name] = desc
return desc
def _ConvertEnumDescriptor(self, enum_proto, package=None, file_desc=None,
containing_type=None, scope=None):
"""Make a protobuf EnumDescriptor given an EnumDescriptorProto protobuf.
Args:
enum_proto: The descriptor_pb2.EnumDescriptorProto protobuf message.
package: Optional package name for the new message EnumDescriptor.
file_desc: The file containing the enum descriptor.
containing_type: The type containing this enum.
scope: Scope containing available types.
Returns:
The added descriptor
"""
if package:
enum_name = '.'.join((package, enum_proto.name))
else:
enum_name = enum_proto.name
if file_desc is None:
file_name = None
else:
file_name = file_desc.name
values = [self._MakeEnumValueDescriptor(value, index)
for index, value in enumerate(enum_proto.value)]
desc = descriptor.EnumDescriptor(name=enum_proto.name,
full_name=enum_name,
filename=file_name,
file=file_desc,
values=values,
containing_type=containing_type,
options=enum_proto.options)
scope['.%s' % enum_name] = desc
self._enum_descriptors[enum_name] = desc
return desc
def MakeFieldDescriptor(self, field_proto, message_name, index,
is_extension=False):
"""Creates a field descriptor from a FieldDescriptorProto.
For message and enum type fields, this method will do a look up
in the pool for the appropriate descriptor for that type. If it
is unavailable, it will fall back to the _source function to
create it. If this type is still unavailable, construction will
fail.
Args:
field_proto: The proto describing the field.
message_name: The name of the containing message.
index: Index of the field
is_extension: Indication that this field is for an extension.
Returns:
An initialized FieldDescriptor object
"""
if message_name:
full_name = '.'.join((message_name, field_proto.name))
else:
full_name = field_proto.name
return descriptor.FieldDescriptor(
name=field_proto.name,
full_name=full_name,
index=index,
number=field_proto.number,
type=field_proto.type,
cpp_type=None,
message_type=None,
enum_type=None,
containing_type=None,
label=field_proto.label,
has_default_value=False,
default_value=None,
is_extension=is_extension,
extension_scope=None,
options=field_proto.options)
def SetAllFieldTypes(self, package, desc_proto, scope):
"""Sets all the descriptor's fields's types.
This method also sets the containing types on any extensions.
Args:
package: The current package of desc_proto.
desc_proto: The message descriptor to update.
scope: Enclosing scope of available types.
"""
package = _PrefixWithDot(package)
main_desc = self._GetTypeFromScope(package, desc_proto.name, scope)
if package == '.':
nested_package = _PrefixWithDot(desc_proto.name)
else:
nested_package = '.'.join([package, desc_proto.name])
for field_proto, field_desc in zip(desc_proto.field, main_desc.fields):
self.SetFieldType(field_proto, field_desc, nested_package, scope)
for extension_proto, extension_desc in (
zip(desc_proto.extension, main_desc.extensions)):
extension_desc.containing_type = self._GetTypeFromScope(
nested_package, extension_proto.extendee, scope)
self.SetFieldType(extension_proto, extension_desc, nested_package, scope)
for nested_type in desc_proto.nested_type:
self.SetAllFieldTypes(nested_package, nested_type, scope)
def SetFieldType(self, field_proto, field_desc, package, scope):
"""Sets the field's type, cpp_type, message_type and enum_type.
Args:
field_proto: Data about the field in proto format.
field_desc: The descriptor to modiy.
package: The package the field's container is in.
scope: Enclosing scope of available types.
"""
if field_proto.type_name:
desc = self._GetTypeFromScope(package, field_proto.type_name, scope)
else:
desc = None
if not field_proto.HasField('type'):
if isinstance(desc, descriptor.Descriptor):
field_proto.type = descriptor.FieldDescriptor.TYPE_MESSAGE
else:
field_proto.type = descriptor.FieldDescriptor.TYPE_ENUM
field_desc.cpp_type = descriptor.FieldDescriptor.ProtoTypeToCppProtoType(
field_proto.type)
if (field_proto.type == descriptor.FieldDescriptor.TYPE_MESSAGE
or field_proto.type == descriptor.FieldDescriptor.TYPE_GROUP):
field_desc.message_type = desc
if field_proto.type == descriptor.FieldDescriptor.TYPE_ENUM:
field_desc.enum_type = desc
if field_proto.label == descriptor.FieldDescriptor.LABEL_REPEATED:
field_desc.has_default_value = False
field_desc.default_value = []
elif field_proto.HasField('default_value'):
field_desc.has_default_value = True
if (field_proto.type == descriptor.FieldDescriptor.TYPE_DOUBLE or
field_proto.type == descriptor.FieldDescriptor.TYPE_FLOAT):
field_desc.default_value = float(field_proto.default_value)
elif field_proto.type == descriptor.FieldDescriptor.TYPE_STRING:
field_desc.default_value = field_proto.default_value
elif field_proto.type == descriptor.FieldDescriptor.TYPE_BOOL:
field_desc.default_value = field_proto.default_value.lower() == 'true'
elif field_proto.type == descriptor.FieldDescriptor.TYPE_ENUM:
field_desc.default_value = field_desc.enum_type.values_by_name[
field_proto.default_value].number
elif field_proto.type == descriptor.FieldDescriptor.TYPE_BYTES:
field_desc.default_value = text_encoding.CUnescape(
field_proto.default_value)
else:
field_desc.default_value = int(field_proto.default_value)
else:
field_desc.has_default_value = False
field_desc.default_value = None
field_desc.type = field_proto.type
def _MakeEnumValueDescriptor(self, value_proto, index):
"""Creates a enum value descriptor object from a enum value proto.
Args:
value_proto: The proto describing the enum value.
index: The index of the enum value.
Returns:
An initialized EnumValueDescriptor object.
"""
return descriptor.EnumValueDescriptor(
name=value_proto.name,
index=index,
number=value_proto.number,
options=value_proto.options,
type=None)
def _ExtractSymbols(self, descriptors):
"""Pulls out all the symbols from descriptor protos.
Args:
descriptors: The messages to extract descriptors from.
Yields:
A two element tuple of the type name and descriptor object.
"""
for desc in descriptors:
yield (_PrefixWithDot(desc.full_name), desc)
for symbol in self._ExtractSymbols(desc.nested_types):
yield symbol
for enum in desc.enum_types:
yield (_PrefixWithDot(enum.full_name), enum)
def _GetDeps(self, dependencies):
"""Recursively finds dependencies for file protos.
Args:
dependencies: The names of the files being depended on.
Yields:
Each direct and indirect dependency.
"""
for dependency in dependencies:
dep_desc = self.FindFileByName(dependency)
yield dep_desc
for parent_dep in dep_desc.dependencies:
yield parent_dep
def _GetTypeFromScope(self, package, type_name, scope):
"""Finds a given type name in the current scope.
Args:
package: The package the proto should be located in.
type_name: The name of the type to be found in the scope.
scope: Dict mapping short and full symbols to message and enum types.
Returns:
The descriptor for the requested type.
"""
if type_name not in scope:
components = _PrefixWithDot(package).split('.')
while components:
possible_match = '.'.join(components + [type_name])
if possible_match in scope:
type_name = possible_match
break
else:
components.pop(-1)
return scope[type_name]
def _PrefixWithDot(name):
return name if name.startswith('.') else '.%s' % name