Implementation:Alibaba MNN Protobuf Generated TCTable Impl H

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

Overview

Header implementing the tail-call table (TCTable) dispatch mechanism for high-performance protobuf parsing.

Description

This header provides the implementation of the tail-call optimized parsing table, a next-generation parsing strategy that uses computed goto or tail-call function pointers for near-zero-overhead field dispatch. Each entry in the TCTable maps a wire-format tag to a specialized parsing function, enabling the parser to jump directly to the correct handler without loop overhead or branch misprediction. MNN vendors this file as part of the protobuf runtime because it provides the fastest available parsing path for large TensorFlow and Caffe model files where deserialization performance is critical.

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/generated_message_tctable_impl.h
• Lines: 1-302

Signature

namespace google {
namespace protobuf {
namespace internal {
struct TcFieldData { uint64 data; };
struct TcParseTableBase { const void* fast_entries; uint32 num_fast_entries; };
const char* TcParser::ParseLoop(MessageLite* msg, const char* ptr, ParseContext* ctx, const TcParseTableBase* table);
}  // namespace internal
}  // namespace protobuf
}  // namespace google

Import

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

I/O Contract

Inputs

Name	Type	Required	Description
ptr	const char*	Yes	Pointer into the raw serialized protobuf byte buffer
table	const TcParseTableBase*	Yes	Tail-call parse table mapping tags to handler functions
ctx	ParseContext*	Yes	Parse context tracking recursion depth and buffer boundaries

Outputs

Name	Type	Description
ptr	const char*	Updated pointer past the consumed bytes, or nullptr on error
msg	MessageLite*	Populated message with all parsed fields from the input buffer

Usage Examples

// MNN internal usage (generated fast-path parsing)
static const internal::TcParseTableBase kTcTable = { ... };
const char* ptr = internal::TcParser::ParseLoop(
    this, raw_ptr, &parse_ctx, &kTcTable);
if (ptr == nullptr) { /* parse error */ }

Related Pages

• Environment:Alibaba_MNN_CPU_Build_Environment