Implementation:Alibaba MNN FlatBuffers IDL Parser

Knowledge Sources	Alibaba_MNN FlatBuffers
Domains	Serialization, Schema_Parsing
Last Updated	2026-02-10 12:00 GMT

Overview

Full schema parser for .fbs files that builds an in-memory representation of FlatBuffers schemas.

Description

idl_parser.cpp implements the core Parser class that tokenizes and parses FlatBuffers schema files (.fbs) into an in-memory abstract representation. It handles all schema constructs including tables, structs, enums, unions, namespaces, includes, attributes, and rpc_service declarations. The parser also supports parsing JSON data against a known schema for binary conversion. At 3172 lines, this is the largest single file in the vendored FlatBuffers source tree.

Usage

Vendored dependency used internally by MNN for model serialization. Not directly imported by end users.

Code Reference

Source Location

• Repository: Alibaba_MNN
• File: 3rd_party/flatbuffers/src/idl_parser.cpp
• Lines: 1-3172

Signature

namespace flatbuffers {
class Parser {
public:
    bool Parse(const char *source, const char **include_paths = nullptr,
               const char *source_filename = nullptr);
    bool SetRootType(const char *name);
    SymbolTable<StructDef> structs_;
    SymbolTable<EnumDef> enums_;
};
}

Import

#include "flatbuffers/idl.h"

I/O Contract

Input	Output
Raw .fbs schema text + optional include paths	Populated Parser with structs_, enums_, services_ symbol tables
JSON text + previously parsed schema	Binary FlatBuffer in Parser::builder_

Usage Examples

#include "flatbuffers/idl.h"

flatbuffers::Parser parser;
const char *include_paths[] = {"schemas/", nullptr};
bool ok = parser.Parse(schema_text, include_paths, "model.fbs");
if (ok) {
    parser.SetRootType("Net");
    // Schema is now ready for code generation or JSON parsing
}

Related Pages

• Environment:Alibaba_MNN_CPU_Build_Environment