Create a basic node addon with zig

This requires node headers within .

Running zig build will generate an addon.node file in the zig-out/lib folder.

This has only been tested on MacOS

.gitignore

@@ -1,2 +1,3 @@
-.zig-cache/
 zig-out/
+.zig-cache/
+.cache/

build.zig

@@ -0,0 +1,82 @@
+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+
+    // Standard optimization options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
+    // set a preferred release mode, allowing the user to decide how to optimize.
+    const optimize = b.standardOptimizeOption(.{});
+
+    const lib = b.addStaticLibrary(.{
+        .name = "node-zig",
+        // In this case the main source file is merely a path, however, in more
+        // complicated build scripts, this could be a generated file.
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    lib.addIncludePath(.{ .src_path = .{
+        .owner = b,
+        .sub_path = ".cache/node/node-v20.18.0/include/node",
+    } });
+
+    // This declares intent for the library to be installed into the standard
+    // location when the user invokes the "install" step (the default step when
+    // running `zig build`).
+    b.installArtifact(lib);
+
+    // Creates a step for unit testing. This only builds the test executable
+    // but does not run it.
+    const lib_unit_tests = b.addTest(.{
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    lib_unit_tests.addIncludePath(.{ .src_path = .{
+        .owner = b,
+        .sub_path = ".cache/node/node-v20.18.0/include/node",
+    } });
+
+    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
+
+    // Similar to creating the run step earlier, this exposes a `test` step to
+    // the `zig build --help` menu, providing a way for the user to request
+    // running the unit tests.
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_lib_unit_tests.step);
+
+    const nodeAddon = b.addSharedLibrary(.{
+        .name = "addon",
+        .target = target,
+        .optimize = optimize,
+    });
+
+    nodeAddon.linker_allow_shlib_undefined = true;
+
+    nodeAddon.linkLibrary(lib);
+    nodeAddon.addIncludePath(.{ .src_path = .{
+        .owner = b,
+        .sub_path = ".cache/node/node-v20.18.0/include/node",
+    } });
+    nodeAddon.linkLibC();
+    nodeAddon.addCSourceFile(.{
+        .file = .{ .src_path = .{
+            .owner = b,
+            .sub_path = "src/addon.c",
+        } },
+        .flags = &.{ "-Wall", "-fPIC" },
+    });
+
+    b.getInstallStep()
+        .dependOn(&b.addInstallArtifact(nodeAddon, .{ .dest_sub_path = "addon.node" }).step);
+}

build.zig.zon

@@ -0,0 +1,72 @@
+.{
+    // This is the default name used by packages depending on this one. For
+    // example, when a user runs `zig fetch --save <url>`, this field is used
+    // as the key in the `dependencies` table. Although the user can choose a
+    // different name, most users will stick with this provided value.
+    //
+    // It is redundant to include "zig" in this name because it is already
+    // within the Zig package namespace.
+    .name = "node-zig",
+
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
+    .version = "0.0.0",
+
+    // This field is optional.
+    // This is currently advisory only; Zig does not yet do anything
+    // with this value.
+    //.minimum_zig_version = "0.11.0",
+
+    // This field is optional.
+    // Each dependency must either provide a `url` and `hash`, or a `path`.
+    // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+    // Once all dependencies are fetched, `zig build` no longer requires
+    // internet connectivity.
+    .dependencies = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+        //
+        //    // When this is set to `true`, a package is declared to be lazily
+        //    // fetched. This makes the dependency only get fetched if it is
+        //    // actually used.
+        //    .lazy = false,
+        //},
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package. Only files listed here will remain on disk
+    // when using the zig package manager. As a rule of thumb, one should list
+    // files required for compilation plus any license(s).
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}

src/addon.c

@@ -0,0 +1,6 @@
+#include <node_api.h>
+#include <stdio.h>
+
+extern napi_value Init(napi_env env, napi_value exports);
+
+NAPI_MODULE("addon", Init)

src/root.zig

@@ -0,0 +1,74 @@
+const node_api = @cImport({
+    @cInclude("node_api.h");
+});
+
+const assert = @import("std").debug.assert;
+
+const napi_status = node_api.napi_status;
+const napi_env = node_api.napi_env;
+const napi_callback_info = node_api.napi_callback_info;
+const napi_value = node_api.napi_value;
+
+fn add(env: napi_env, info: napi_callback_info) callconv(.C) napi_value {
+    var args: [2]napi_value = undefined; // must be var b/c of cast
+    var argc: usize = 2;
+    var status: node_api.napi_status = undefined;
+
+    status = node_api.napi_get_cb_info(env, info, &argc, &args, null, null);
+    assert(status == node_api.napi_ok);
+
+    if (argc < 2) {
+        _ = node_api.napi_throw_type_error(env, null, "Wrong number of arguments");
+        return null;
+    }
+
+    var valuetype0: node_api.napi_valuetype = undefined;
+    status = node_api.napi_typeof(env, args[0], &valuetype0);
+    assert(status == node_api.napi_ok);
+
+    var valuetype1: node_api.napi_valuetype = undefined;
+    status = node_api.napi_typeof(env, args[1], &valuetype1);
+    assert(status == node_api.napi_ok);
+
+    if (valuetype0 != node_api.napi_number or valuetype1 != node_api.napi_number) {
+        _ = node_api.napi_throw_type_error(env, null, "Wrong arguments");
+        return null;
+    }
+
+    var value0: f64 = undefined;
+    status = node_api.napi_get_value_double(env, args[0], &value0);
+    assert(status == node_api.napi_ok);
+
+    var value1: f64 = undefined;
+    status = node_api.napi_get_value_double(env, args[1], &value1);
+    assert(status == node_api.napi_ok);
+
+    var sum: napi_value = undefined;
+    status = node_api.napi_create_double(env, value0 + value1, &sum);
+    assert(status == node_api.napi_ok);
+
+    return sum;
+}
+
+fn declareNapiMethod(name: anytype, func: node_api.napi_callback) node_api.napi_property_descriptor {
+    return .{
+        .utf8name = name,
+        .method = func,
+        .attributes = node_api.napi_default,
+        .name = null,
+        .getter = null,
+        .setter = null,
+        .value = null,
+        .data = null,
+    };
+}
+
+export fn Init(env: napi_env, exports: napi_value) napi_value {
+    // see: https://nodejs.org/api/n-api.html#napi_property_descriptor
+    var addDescriptor = declareNapiMethod("add", add);
+
+    const status = node_api.napi_define_properties(env, exports, 1, &addDescriptor);
+    assert(status == node_api.napi_ok);
+
+    return exports;
+}