Bundlex

Bundlex is a multi-platform tool for compiling C code along with elixir projects, for use in NIFs, CNodes and Ports. The tool provides also convenient way of accessing compiled code in elixir modules.

This tool is a part of Membrane Framework

Instalation

To install, you need to configure Mix project as follows:

defmodule MyApp.Mixfile do
  use Mix.Project

  def project do
    [
      app: :my_app,
      compilers: [:bundlex] ++ Mix.compilers, # add bundlex to compilers
      deps: deps(),
      # ...
   ]
  end

  defp deps() do
    [
      {:bundlex, "~> 0.4.0"} # add bundlex to deps
    ]
  end
end

and create bundlex.exs file in the project root folder, containing Bundlex project module:

defmodule Membrane.Element.Mad.BundlexProject do
  use Bundlex.Project

  def project() do
    []
  end
end

Now your project does not contain any C sources, but should compile successfully, and some Bundlex messages should be printed while compilation proceeds.

Usage

Adding natives to project

Adding natives can be done in project/0 function of Bundlex project module in the following way:

defmodule MyApp.BundlexProject do
  use Bundlex.Project

  def project() do
    [
      natives: natives(Bundlex.platform),
      libs: libs()
    ]
  end

  defp natives(:linux) do
    [
      my_native: [
        sources: ["something.c", "linux_specific.c"],
        interface: :nif
      ],
      my_other_native: [
        sources: ["something_other.c", "linux_specific.c"],
        interface: :cnode
      ],
      my_other_native: [
        sources: ["something_more_other.c", "linux_specific.c"],
        interface: :port
      ]
    ]
  end

  defp natives(_platform) do
    [
      my_native: [
        sources: ["something.c", "multiplatform.c"],
        interface: :nif
      ],
      my_other_native: [
        sources: ["something_other.c", "multiplatform.c"],
        interface: :cnode
      ],
      my_other_native: [
        sources: ["something_more_other.c", "multiplatform.c"],
        interface: :port
      ]
    ]
  end

  defp libs() do
    [
      my_lib: [
        sources: ["something.c"],
        interface: :nif
      ],
      my_lib: [
        sources: ["something_other.c"],
        interface: :cnode
      ]
    ]
  end
end

As we can see, we can specify two types of resources:

natives - code implemented in C that will be used within Elixir code
libs - can be used by other resources as dependencies (see deps option below)

The sources should reside in project_root/c_src/my_app directory (this can be changed with src_base option, see below).

Configuration of each native may contain following options:

sources - C files to be compiled (at least one must be provided),
includes - Paths to look for header files (empty list by default).
lib_dirs - Absolute paths to look for libraries (empty list by default).
libs - Names of libraries to link (empty list by default).
pkg_configs - Names of libraries for which the appropriate flags will be obtained using pkg-config (empty list by default).
deps - Dependencies in the form of {app, lib_name}, where app is the application name of the dependency, and lib_name is the name of lib specified in Bundlex project of this dependency. Empty list by default. See Dependencies section below for details.
src_base - Native files should reside in project_root/c_src/<src_base> (application name by default).
compiler_flags - Custom flags for compiler.
linker_flags - Custom flags for linker.
language - Language of native. :c or :cpp may be chosen (:c by default)
interface - Interface used to integrate with Elixir code. The following interfaces are available:
- :nif - dynamically linked to the Erlang VM (see Erlang docs)
- :cnode - executed as separate OS processes, accessed through sockets (see Erlang docs)
- :port - executed as separate OS processes (see Elixir Port docs) Specifying no interface is valid only for libs.
preprocessors - Modules that will preprocess the native, see Bundlex.Project.Preprocessor.

Dependencies

Each native can have dependencies - libs that are statically linked to it and can be included in its native code like #include lib_name/some_header.h. The following rules apply:

To add dependencies from a separate project, it must be available via Mix.
Only libs can be added as dependencies.
Each dependency of a native must specify the same or no interface. If there exist multiple versions of dependency with different interfaces, the proper version is selected automatically.
A lib that specifies no interface can depend on libs with no interfaces only.

Compilation options

The following command-line arguments can be passed:

--store-scripts - if set, shell scripts are stored in the project root folder for further analysis.

Loading NIFs in modules

NIFs compiled with Bundlex can be loaded the same way as any other NIFs (see :erlang.load_nif/2), but Bundlex provides Bundlex.Loader module to save you some boilerplate:

defmodule MyApp.SomeNativeStuff do
  use Bundlex.Loader, nif: :my_nif

  def normal_function(a, b, c, d) do
    private_native_function(a+b, c+d)
  end

  defnif native_function(a, b)

  defnifp private_native_function(x, y)

end

Note that unlike when using :erlang.load_nif/2, here defs and defps can be used to create usual functions, native ones are declared with defnif and defnifp. This is achieved by creating a new module under the hood, and that is why the module passed to C macro ERL_NIF_INIT has to be succeeded by .Nif, i.e.

ERL_NIF_INIT(MyApp.SomeNativeStuff.Nif, funs, load, NULL, upgrade, unload)

Despite this, any native erlang macros and functions shall be used as usual, as described at http://erlang.org/doc/man/erl_nif.html

Interacting with CNodes

As in the case of NIFs, CNodes compiled with Bundlex can be used like any other CNodes (see built-in Node module), while some useful stuff for interacting with them is provided. Bundlex.CNode module contains utilities that make it easier to spawn and control CNodes, and allow them to treat them more like usual Elixir processes. Check out the documentation for more details.

Interacting with Ports

Similarly to CNodes Bundlex provides Bundlex.Port module for a little easier interacting with Ports. Please refer to the module's documentation to see how to use it.

More examples

More advanced examples can be found in our test_projects or in our repositories where we use Bundlex e.g. in Unifex.

Copyright and License

Licensed under the Apache License, Version 2.0

TypedLambda / bundlex