lua-pb

Lua Protocol Buffers.

Supports dynamic loading of Protocol Buffer message definition files .proto

Installing

$ sudo luarocks install "https://raw.github.com/Neopallium/lua-pb/master/lua-pb-scm-0.rockspec"

Design

Frontend .proto definition file parser:

• pb/proto/scanner.lua -- LPeg lexer for .proto files.
• pb/proto/util.lua -- some utility functions.
• pb/proto/grammar.lua -- LPeg grammar for .proto files.
• pb/proto/parser.lua -- LPeg based .proto -> AST tree parser.

There can be multiple Backend message definition compilers. An optimized backend for LuaJIT is planned.

Standard backend compiler

• pb/standard.lua -- main compiler code.
• pb/handlers.lua -- a helper object for managing registered encode/decode formats.
• pb/standard/message.lua -- defines message interface.
• pb/standard/repeated.lua -- defines repeated field interface.
• pb/standard/pack.lua -- binary format encoding (Uses modules luabitops & struct)
• pb/standard/unpack.lua -- binary format decoding (Uses modules luabitops & struct)
• pb/standard/buffer.lua -- encoding buffer
• pb/standard/unknown.lua -- object for hold unknown fields.
• pb/standard/dump.lua -- message dumping code.

Finished

• .proto definition parser
• Message encoding/decoding
• Dumping messages to text format.
• Support for packing/unpacking unknown fields.

TODO

• rename pb/handlers.lua to pb/formats.lua

Missing features:

• custom options:

  import "google/protobuf/descriptor.proto";

  extend google.protobuf.MessageOptions { optional string my_option = 51234; }

  message MyMessage { option (my_option) = "Hello world!"; }

• services

Improvements:

• store unknown fields as raw binary, only fully decode when accessed.
• LuaJIT optimized backend compiler.