simonmcconnell / zigler

zig nifs in elixir

Zigler

Library test status:

Installation

Zigler is available in Hex, and the package can be installed by adding zigler to your list of dependencies in mix.exs:

def deps do
  [
    {:zigler, "~> 0.9.1", runtime: false}
  ]
end

Documentation

Docs can be found at https://hexdocs.pm/zigler.

Currently supported platforms

• Linux

• FreeBSD (tested, but not subjected to CI)

• MacOS (I believe it works but is still officially untested)

• Nerves cross-compilation is supported out of the box.

Zig Nifs made easy

Wouldn't it be nice if you could make NIFs as easily as you can use the asm keyword in C?

This is now possible, using the magic of Zig.

defmodule ExampleZig do
  use Zig
  ~Z"""
  /// nif: example_fun/2
  fn example_fun(value1: f64, value2: f64) bool {
    return value1 > value2;
  }
  """
end

test "example nifs" do
  assert ExampleZig.example_fun(0.8, -0.8)
  refute ExampleZig.example_fun(0.1, 0.4)
end

Zigler will do automatic type marshalling between Elixir code and Zig code. It will also convert trickier types into types you care about, for example:

defmodule ZigCollections do
  use Zig
  ~Z"""
  /// nif: string_count/1
  fn string_count(string: []u8) i64 {
    return @intCast(i64, string.len);
  }

  /// nif: list_sum/1
  fn list_sum(array: []f64) f64 {
    var sum: f64 = 0.0;
    for(array) | item | {
      sum += item;
    }
    return sum;
  }
  """
end

test "type marshalling" do
  assert 9 == ZigCollections.string_count("hello zig")
  assert 6.0 == ZigCollections.list_sum([1.0, 2.0, 3.0])
end

Memory allocation with zigler is easy! A standard BEAM allocator is provided for you, so any zig code you import will play nice with the BEAM.

defmodule Allocations do
  use Zig
  ~Z"""
  /// nif: double_atom/1
  fn double_atom(env: beam.env, string: []u8) beam.term {
    var double_string = beam.allocator.alloc(u8, string.len * 2) catch {
      return beam.raise_enomem(env);
    };

    defer beam.allocator.free(double_string);

    for (string) | char, i | {
      double_string[i] = char;
      double_string[i + string.len] = char;
    }

    return beam.make_atom(env, double_string);
  }
  """
end

test "allocations" do
  assert :foofoo == Allocations.double_atom("foo")
end

It is a goal for Zigler to make using it to bind C libraries easier than using C to bind C libraries. Here is an example:

defmodule BlasDynamic do
  use Zig,
    libs: ["/usr/lib/x86_64-linux-gnu/blas/libblas.so"],
    include: ["/usr/include/x86_64-linux-gnu"],
    link_libc: true

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

  /// nif: blas_axpy/3
  fn blas_axpy(env: beam.env, a: f64, x: []f64, y: []f64) beam.term {
    if (x.len != y.len) {
      return beam.raise_function_clause_error(env);
    }

    blas.cblas_daxpy(@intCast(c_int, x.len), a, x.ptr, 1, y.ptr, 1);

    return beam.make_f64_list(env, y) catch {
      return beam.raise_function_clause_error(env);
    };
  }
  """
end

test "we can use a blas shared library" do
  # returns aX+Y
  assert [11.0, 18.0] == BlasDynamic.blas_axpy(3.0, [2.0, 4.0], [5.0, 6.0])
end

Documentation

You can document nif functions, local functions, zig structs, variables, and types. If you document a nif function, it will be a part of the module documentation, and accessible using the iex h method, etc.

Example:

defmodule Documentation do
  use Zig
  ~Z"""
  /// a zero-arity function which returns 47.
  /// nif: zero_arity/0
  fn zero_arity() i64 {
    return 47;
  }
  """
end

Formatting

A mix format plugin is available through the zigler_format package. See the installation instructions

Zigler Principles

1. Make being a good citizen of the BEAM easy.
2. Use magic, but sparingly, only to prevent errors.
3. Let the user see behind the curtain.
4. Let the user opt out of magic.
5. Magic shouldn't get in the way.