Implementation:Alibaba MNN Protobuf Arena H

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

Overview

Header declaring the Protocol Buffers Arena allocator class for pooled memory management of protobuf messages.

Description

This header defines the google::protobuf::Arena class and its associated ArenaOptions configuration struct. The Arena provides a region-based allocation strategy where multiple protobuf messages share a common memory pool, dramatically reducing allocation overhead and enabling batch deallocation. MNN vendors this header as part of the protobuf runtime to support efficient memory management when parsing large TensorFlow and Caffe model files that contain deeply nested message hierarchies.

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/arena.h
• Lines: 1-821

Signature

namespace google {
namespace protobuf {
struct ArenaOptions { size_t start_block_size; size_t max_block_size; };
class PROTOBUF_EXPORT Arena final {
  template <typename T> static T* CreateMessage(Arena* arena);
  template <typename T> static T* Create(Arena* arena);
  uint64 SpaceUsed() const;
};
}  // namespace protobuf
}  // namespace google

Import

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

I/O Contract

Inputs

Name	Type	Required	Description
ArenaOptions	ArenaOptions	No	Configuration controlling block sizes and custom allocator hooks

Outputs

Name	Type	Description
Arena class	google::protobuf::Arena	Region-based allocator providing CreateMessage and Create factory methods

Usage Examples

// MNN internal usage
#include "google/protobuf/arena.h"
google::protobuf::ArenaOptions opts;
opts.start_block_size = 8192;
google::protobuf::Arena arena(opts);
auto* node = Arena::CreateMessage<NodeDef>(&arena);

Related Pages

• Environment:Alibaba_MNN_CPU_Build_Environment