flatt

Flatbuffers code reflection based generation tool with scripting support.

Why?

Flatbuffers is awesome, but you'll eventually need to (or wish you could) write additional code generation steps for your schema files. For example, generating a network protocol handler/dispatcher for you client and server and keep them in sync.

How does it work?

flatt exposes a lua runtime with some additional helper functions to help you deal with Flatbuffers schema files, reflection and template rendering. You can for example write a flatt script that will reflect your schema, manipulate that data, and render (using a template engine or not) a file with the content you just processed.

All builtin lua libraries are exported and you can use luarocks packages with it if you want to.

An example of what a flatt script looks like:

-- luarocks install lunajson
local lunajson = require("lunajson")

flatt.log.info("Generating headers...")
flatt.flatc({ "--cpp", "./schema.fbs" })

local json = flatt.reflect("./schema.fbs")
flatt.log.trace(json)

--[[
  {
    "tables": [
      {
        "id": 182975129,
        "name": "MyTable",
        "namespace": "my.namespace",
        "fields": [
          {
            "name": "some_field",
            ...
          }
        ]
      }
      ...
    ],
    "structs": [
      ...
    ],
    ...
  }
]]

local info = lunajson.decode(json)

-- generate a file using `info` data

Usage

Installation

• npm install -g flatt

Requirements

• Windows (PRs welcome to add Linux+WSL and Mac support)

Overview

flatt some/project.lua

Building

Requirements

• scoop install cmake
• scoop install charm-gum
• scoop install just

Compiling

npm install && npm run build

---

API

vars

---

flatt.vars.flatt_dir

Has the flatt executable directory.

flatt.vars.project_dir

Project directory (from the given project script file).

flatt.vars.argv

A table (list) of arguments passed next to the script file.

$ flatt project.lua --hello --world abc 123

flatt.vars.argv
-- { "--hello", "--world", "abc", "123" }

flatt.vars.argv[1]
-- { "--hello" }

-- `luarocks install argparse`
local argparse = require("argparse")

local parser = argparse("example", "Arguments example.")
parser:flag("-h --hello", "Hello argument.", "")
parser:flag("-w --world", "World argument.", "")
parser:argument("a", "Some value")
parser:argument("b", "Some value")

local args = parser:parse(flatt.vars.argv)

args.hello
-- true

args.world
-- false

args.a
-- "abc"

args.b
-- "123"

---

flatc

---

flatt.flatc(arguments)

flatt.flatc({ "--cpp", "schema.fbs" })
-- return: the exit code

---

shell

---

flatt.shell(command, arguments)

flatt.shell("echo", { "hello", "world" })
-- return: the exit code

---

reflect

---

flatt.reflect(path)

flatt.reflect("schema.fbs")
--[[
  {
    // JSON encoded schema
  }
]]

---

log

---

Functions

Level list

• trace
• debug
• info
• warn
• error
• critical

flatt.file.set_level(level)

flatt.log.set_level("info")
-- Sets the current logging level

flatt.file.get_level()

flatt.log.get_level()
-- Gets the current logging level

flatt.file.trace(line)

flatt.log.trace("log line")
-- Writes to console in white (windows)

flatt.file.trace(line)

flatt.log.trace("log line")
-- Writes to console in white (windows)

flatt.file.debug(line)

flatt.log.debug("log line")
-- Writes to console in blue (windows)

flatt.file.info(line)

flatt.log.info("log line")
-- Writes to console in green (windows)

flatt.file.warn(line)

flatt.log.warn("log line")
-- Writes to console in yellow (windows)

flatt.file.error(line)

flatt.log.error("log line")
-- Writes to console in red (windows)

flatt.file.critical(line)

flatt.log.critical("log line")
-- Writes to console in white with red background (windows)

---

file

---

Functions

flatt.file.write(path, data)

flatt.dir.read("hello.txt", "Hello world!)
-- return: "Hello world!"

flatt.file.read(path)

flatt.dir.read("hello.txt")
-- return: "Hello world!"

flatt.file.exists(path)

flatt.dir.exists("./non-existing-file.ext")
-- return: false

flatt.dir.exists("hello.txt")
-- return: true

flatt.file.hash(path)

flatt.dir.hash("./non-existing-file.ext")
-- return: nil

flatt.dir.hash("some-file.ext")
-- return: "EDCBA5DD333A60F3C98452672A1AB1711409040D"

---

dir

---

Functions

flatt.dir.hash(path)

flatt.dir.hash("./non-existing-dir")
-- return: nil

flatt.dir.hash(".")
-- return: "4CF8ADEDB3B43E78645E4DE673D2D7DD4CFADA58"

---

templates

---

Builtin provided template engine functions (inja). Use aspect for a more Lua friendly template system.

Functions

flatt.templates.render_string(template, data)

Accepts JSON encoded string for data.

flatt.templates.render_string("hello {{name}}", "{\"name\":\"world\"}")
-- return: "hello world"

flatt.templates.render_file(src, dest, data)

Accepts JSON encoded string for data.

flatt.templates.render_string("template.txt", "output.txt", "{\"name\":\"world\"}")
-- return: true

---

string

---

Functions

flatt.string.pad_left(string, len, pad = " ")

flatt.string.pad_left("1234", 8)
-- return: "    1234"

flatt.string.pad_left("1234", 8, "0")
-- return: "00001234"

flatt.string.pad_right(string, len, pad = " ")

flatt.string.pad_left("1234", 8)
-- return: "1234    "

flatt.string.pad_right("1234", 8, "0")
-- return: "12340000"

flatt.string.starts_with(string, string)

flatt.string.starts_with("hello world", "hello")
-- return: true

flatt.string.starts_with("hello world", "world")
-- return: false

flatt.string.ends_with(string, string)

flatt.string.ends_with("hello world", "hello")
-- return: false

flatt.string.ends_with("hello world", "world")
-- return: true

flatt.string.split(string, delim, limit = 0)

flatt.string.split("hello world", " ")
-- return: {"hello", "world"}

flatt.string.split("is this real life", " ", 3)
-- return: {"is", "this", "real life"}

flatt.string.trim(string)

flatt.string.trim("  hello    world  ")
-- return: "hello    world"

flatt.string.trim_left(string)

flatt.string.trim("  hello    world  ")
-- return: "hello    world  "

flatt.string.trim_right(string)

flatt.string.trim("  hello    world")
-- return: "hello    world  "

flatt.string.explode(string)

Splits the string whenever one of the following characters is found: . -_|/\

flatt.string.explode("a.b c-d|e/f\\g")
-- return: { "a", "b", "c", "d", "e", "f", "g" }

flatt.string.join(strings, delim = ",")

flatt.string.join({ "a", "b", "c", "d", "e", "f", "g" }, "~")
-- return: "a~b~c~d~e~f~g"

flatt.string.lower_case(string)

flatt.string.lower_case("NewGUIAlertBox")
-- return: "newguialertbox"

flatt.string.upper_case(string)

flatt.string.upper_case("NewGUIAlertBox")
-- return: "NEWGUIALERTBOX"

flatt.string.ucfirst(string)

flatt.string.ucfirst("NewGUIAlertBox")
-- return: "NewGUIAlertBox"

flatt.string.lcfirst(string)

flatt.string.lcfirst("NewGUIAlertBox")
-- return: "newGUIAlertBox"

flatt.string.snake_case(string)

flatt.string.snake_case("NewGUIAlertBox")
-- return: "new_gui_alert_box"

flatt.string.kebab_case(string)

flatt.string.kebab_case("NewGUIAlertBox")
-- return: "new-gui-alert-box"

flatt.string.pascal_case(string)

flatt.string.pascal_case("NewGUIAlertBox")
-- return: "NewGuiAlertBox"

flatt.string.camel_case(string)

flatt.string.camel_case("NewGUIAlertBox")
-- return: "newGuiAlertBox"

flatt.string.const_case(string)

flatt.string.const_case("NewGUIAlertBox")
-- return: "NEW_GUI_ALERT_BOX"

flatt.string.train_case(string)

flatt.string.train_case("NewGUIAlertBox")
-- return: "New-Gui-Alert-Box"

flatt.string.ada_case(string)

flatt.string.ada_case("NewGUIAlertBox")
-- return: "New_Gui_Alert_Box"

flatt.string.cobol_case(string)

flatt.string.cobol_case("NewGUIAlertBox")
-- return: "NEW-GUI-ALERT-BOX"

flatt.string.dot_case(string)

flatt.string.dot_case("NewGUIAlertBox")
-- return: "new.gui.alert.box"

flatt.string.path_case(string)

flatt.string.path_case("NewGUIAlertBox")
-- return: "new/gui/alert/box"

flatt.string.space_case(string)

flatt.string.space_case("NewGUIAlertBox")
-- return: "new gui alert box"

flatt.string.capital_case(string)

flatt.string.capital_case("NewGUIAlertBox")
-- return: "New Gui Alert Box"

flatt.string.cpp_case(string)

flatt.string.cpp_case("NewGUIAlertBox")
-- return: "new::gui::alert::box"