Implementation:Alibaba MNN Protobuf Descriptor CC
| Knowledge Sources | |
|---|---|
| Domains | Serialization, Reflection |
| Last Updated | 2026-02-10 12:00 GMT |
Overview
Core implementation of the Protocol Buffers Descriptor system providing runtime schema reflection and message introspection.
Description
This is one of the largest and most critical files in the protobuf runtime, implementing the full descriptor infrastructure that enables runtime introspection of protobuf schemas. It includes the construction, validation, and cross-linking of file descriptors, message descriptors, field descriptors, enum descriptors, and service descriptors from their proto definitions. MNN vendors this file because TensorFlow and Caffe model converters rely on the descriptor system to dynamically resolve message types, validate schemas, and perform reflection-based serialization during model format parsing.
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/descriptor.cc - Lines: 1-8025
Signature
namespace google {
namespace protobuf {
const FileDescriptor* DescriptorPool::BuildFile(const FileDescriptorProto& proto);
const Descriptor* DescriptorPool::FindMessageTypeByName(const std::string& name) const;
const FieldDescriptor* Descriptor::FindFieldByName(const std::string& name) const;
const EnumValueDescriptor* EnumDescriptor::FindValueByNumber(int number) const;
} // namespace protobuf
} // namespace google
Import
#include "3rd_party/protobuf/src/google/protobuf/descriptor.h"
I/O Contract
Inputs
| Name | Type | Required | Description |
|---|---|---|---|
| proto | FileDescriptorProto |
Yes | Parsed .proto file descriptor to build into the pool |
| name | const std::string& |
Yes | Fully qualified type name for descriptor lookups |
Outputs
| Name | Type | Description |
|---|---|---|
| FileDescriptor | const FileDescriptor* |
Built and cross-linked file descriptor with all contained types |
| Descriptor | const Descriptor* |
Message descriptor providing field access and nested type enumeration |
| FieldDescriptor | const FieldDescriptor* |
Individual field descriptor with type, number, and label metadata |
Usage Examples
// MNN internal usage
const auto* pool = google::protobuf::DescriptorPool::generated_pool();
const auto* desc = pool->FindMessageTypeByName("tensorflow.GraphDef");
const auto* field = desc->FindFieldByName("node");
int field_count = desc->field_count();