Inline NIF support for Zig

Motivation

Zig is a general-purpose programming language designed for robustness, optimality, and maintainability.

The programming philosophy of Zig matches up nicely with the programming philosophy of the BEAM VM and in particular its emphasis on simplicity and structure should very appealing to the practitioners of Elixir.

The following features make Zig extremely amenable to inline language support in a BEAM language:

• simplicity. Zig's syntax is definable in a simple YACC document and Zig takes a stance against making its featureset more complex (though it may evolve somewhat en route to 1.0)
• Composability. Zig is unopinionated about how to go about memory allocations. Its allocator interface is very easily able to be backed by the BEAM's, which means that you have access to generic memory allocation strategies through its composable allocator scheme.
• C integration. It's very easy to design C-interop between Zig and C. In fact, Zig is likely to be an easier glue language for C ABIs than C.
• OOM safety and sanity. Zig makes it easy to defer memory destruction, meaning you often don't have to worry about memory leaks. By design, alloc should be failable (as is the BEAM's alloc) so it offers an extra layer of protection for you BEAM VM against an OOM situation.

Basic usage

In the BEAM, you can define a NIF by consulting the following document and implementing the appropriate shared object/DLL callbacks. However, Zigler will take care of all of this for you.

Simply use Zigler in your module, providing the app atom in the property list.

Then, use the sigil_Z/2 macro and write zig code. Any nifs you define should be preceded with the /// nif: function_name/arity zig docstring.

Example

defmodule MyModule do
  use Zigler, otp_app: :my_app

  ~Z"""
  /// nif: my_func/1
  fn my_func(val: i64) i64 {
    return val + 1;
  }
  """

end

Zigler will automatically fill out the appropriate NIF C template, compile the shared object, and bind it into the module pre-compilation. In the case of the example, there will be a MyModule.my_func/1 function call found in the module.

Zigler will also make sure that your statically-typed Zig data are guarded when you marshal it from the dynamically-typed BEAM world. However, you may only pass in and return certain types (though the generic beam.term type) is supported.

Environment

Sometimes, you will need to pass the BEAM environment (which is the code execution context, including process info, etc.) into the NIF function. In this case, you should pass it as the first argument, as a beam.env type value.

Example

defmodule MyModule do
  use Zigler, otp_app: :my_app

  ~Z"""
  /// nif: my_func_with_env/1
  fn my_func_with_env(env: beam.env, pid: beam.pid) void {
    var sendable_term: []u64 = "ping"[0..];
    var msg = beam.make_slice(env, sendable_term);
    var res = e.enif_send(env, pid, env, msg);
  }
  """
end

External Libraries

If you need to bind static (*.a) or dynamic (*.so) libraries into your module, you may link them with the :libs argument.

Note that for shared libraries, a library with an identical path must exist in the target release environment.

Example

defmodule Blas do
  use Zigler,
    otp_app: :my_app,
    libs: ["/usr/lib/x86_64-linux-gnu/blas/libblas.so"],
    include: ["/usr/include/x86_64-linux-gnu"]

  ~Z"""
  const blas = @cImport({
    @cInclude("cblas.h");
  ...

Compilation assistance

If something should go wrong, Zigler will translate the Zig compiler error into an Elixir compiler error, and let you know exactly which line in the ~Z block it came from.

Syntactic Sugar

Some of the erlang nif terms can get unwieldy, especially in Zig, which prefers terseness. Each of the basic BEAM types is shadowed by a Zig type in the beam module. The beam struct is always imported into the header of the zig file used, so all zig code in the same directory as the module should have access to the beam struct if they @import("beam.zig")

Importing files

If you need to write code outside of the basic module (you will, for anything non-trivial), just place it in the same directory as your module.

Example

~Z"""
const extra_code = @import("extra_code.zig");

/// nif: use_extra_code/1
fn use_extra_code(val: i64) i64 {
  return extra_code.extra_fn(val);
}
"""

If you would like to include a custom c header file, create an include/ directory inside your path tree and it will be available to zig as a default search path as follows:

~Z"""
const c = @cImport({
  @cInclude("my_c_header.h");
});

// nif: my_nif/1
...
"""

Documentation

Use the builtin zig /// docstring to write your documentation. If it's in front of the nif declaration, it will wind up in the correct place in your elixir documentation.

See Zigler.Doc for more information on how to document in zig and what to document. See Mix.Tasks.ZigDoc for information on how to get your Elixir project to incorporate zig documentation.

Tests

Use the builtin zig test keyword to write your internal zig unit tests. These can be imported into an ExUnit module by following this example:

defmodule MyTest do
  use ExUnit.Case
  use Zigler.Unit
  zigtest ModuleWithZigCode
end

See Zigler.Unit for more information.