Implementation:Alibaba MNN Protobuf Extension Set H

Knowledge Sources	Alibaba_MNN Protocol Buffers
Domains	Serialization, Extensibility
Last Updated	2026-02-10 12:00 GMT

Overview

Header declaring the Protocol Buffers ExtensionSet class and related types for managing extension fields on protobuf messages.

Description

This header defines the ExtensionSet class within the google::protobuf::internal namespace, providing the interface for storing, accessing, and serializing extension fields. It includes type-specific getters and setters for all protobuf scalar types, string types, and message types, as well as repeated field variants. The header also defines the ExtensionInfo struct and registration mechanisms for extension fields. MNN vendors this header because the Caffe protobuf schema uses extensions extensively, and the full ExtensionSet infrastructure is needed to correctly parse these model files.

Usage

Vendored dependency used internally by MNN for parsing protobuf-based model formats (TensorFlow, Caffe). Not directly imported by end users.

Code Reference

Source Location

• Repository: Alibaba_MNN
• File: 3rd_party/protobuf/src/google/protobuf/extension_set.h
• Lines: 1-1560

Signature

namespace google {
namespace protobuf {
namespace internal {
class PROTOBUF_EXPORT ExtensionSet {
  bool Has(int number) const;
  void Clear(int number);
  size_t SpaceUsedExcludingSelfLong() const;
  bool SerializeWithCachedSizes(int start, int end, io::CodedOutputStream* output) const;
};
}  // namespace internal
}  // namespace protobuf
}  // namespace google

Import

#include "3rd_party/protobuf/src/google/protobuf/extension_set.h"

I/O Contract

Inputs

Name	Type	Required	Description
N/A	N/A	N/A	Header-only declarations; provides the ExtensionSet interface for extension field management

Outputs

Name	Type	Description
ExtensionSet	google::protobuf::internal::ExtensionSet	Container class managing all extension fields on a protobuf message

Usage Examples

// MNN internal usage (within generated message code)
#include "google/protobuf/extension_set.h"
internal::ExtensionSet _extensions_;
if (_extensions_.Has(kConvolutionParam)) {
  const auto& param = _extensions_.GetMessage(kConvolutionParam, default_instance);
}

Related Pages

• Environment:Alibaba_MNN_CPU_Build_Environment