Simplistic libuv wrapper example in Zig

libuv.zig

const std = @import("std");
const warn = @import("std").debug.warn; // XXX DEBUG
const assert = std.debug.assert;

const c = @cImport({
    @cInclude("uv.h");
});

pub const UVError = error{ E2BIG, EACCES, EADDRINUSE, EADDRNOTAVAIL, EAFNOSUPPORT, EAGAIN, EAI_ADDRFAMILY, EAI_AGAIN, EAI_BADFLAGS, EAI_BADHINTS, EAI_CANCELED, EAI_FAIL, EAI_FAMILY, EAI_MEMORY, EAI_NODATA, EAI_NONAME, EAI_OVERFLOW, EAI_PROTOCOL, EAI_SERVICE, EAI_SOCKTYPE, EALREADY, EBADF, EBUSY, ECANCELED, ECHARSET, ECONNABORTED, ECONNREFUSED, ECONNRESET, EDESTADDRREQ, EEXIST, EFAULT, EFBIG, EHOSTUNREACH, EINTR, EINVAL, EIO, EISCONN, EISDIR, ELOOP, EMFILE, EMSGSIZE, ENAMETOOLONG, ENETDOWN, ENETUNREACH, ENFILE, ENOBUFS, ENODEV, ENOENT, ENOMEM, ENONET, ENOPROTOOPT, ENOSPC, ENOSYS, ENOTCONN, ENOTDIR, ENOTEMPTY, ENOTSOCK, ENOTSUP, EPERM, EPIPE, EPROTO, EPROTONOSUPPORT, EPROTOTYPE, ERANGE, EROFS, ESHUTDOWN, ESPIPE, ESRCH, ETIMEDOUT, ETXTBSY, EXDEV, UNKNOWN, EOF, ENXIO, EMLINK };

fn check_uv(r: i32) !void {
    if (r >= 0) return;

    return switch (r) {
        // All positive (including 0) numbers
        c.UV_E2BIG => UVError.E2BIG,
        c.UV_EACCES => UVError.EACCES,
        c.UV_EADDRINUSE => UVError.EADDRINUSE,
        c.UV_EADDRNOTAVAIL => UVError.EADDRNOTAVAIL,
        c.UV_EAFNOSUPPORT => UVError.EAFNOSUPPORT,
        c.UV_EAGAIN => UVError.EAGAIN,
        c.UV_EAI_ADDRFAMILY => UVError.EAI_ADDRFAMILY,
        c.UV_EAI_AGAIN => UVError.EAI_AGAIN,
        c.UV_EAI_BADFLAGS => UVError.EAI_BADFLAGS,
        c.UV_EAI_BADHINTS => UVError.EAI_BADHINTS,
        c.UV_EAI_CANCELED => UVError.EAI_CANCELED,
        c.UV_EAI_FAIL => UVError.EAI_FAIL,
        c.UV_EAI_FAMILY => UVError.EAI_FAMILY,
        c.UV_EAI_MEMORY => UVError.EAI_MEMORY,
        c.UV_EAI_NODATA => UVError.EAI_NODATA,
        c.UV_EAI_NONAME => UVError.EAI_NONAME,
        c.UV_EAI_OVERFLOW => UVError.EAI_OVERFLOW,
        c.UV_EAI_PROTOCOL => UVError.EAI_PROTOCOL,
        c.UV_EAI_SERVICE => UVError.EAI_SERVICE,
        c.UV_EAI_SOCKTYPE => UVError.EAI_SOCKTYPE,
        c.UV_EALREADY => UVError.EALREADY,
        c.UV_EBADF => UVError.EBADF,
        c.UV_EBUSY => UVError.EBUSY,
        c.UV_ECANCELED => UVError.ECANCELED,
        c.UV_ECHARSET => UVError.ECHARSET,
        c.UV_ECONNABORTED => UVError.ECONNABORTED,
        c.UV_ECONNREFUSED => UVError.ECONNREFUSED,
        c.UV_ECONNRESET => UVError.ECONNRESET,
        c.UV_EDESTADDRREQ => UVError.EDESTADDRREQ,
        c.UV_EEXIST => UVError.EEXIST,
        c.UV_EFAULT => UVError.EFAULT,
        c.UV_EFBIG => UVError.EFBIG,
        c.UV_EHOSTUNREACH => UVError.EHOSTUNREACH,
        c.UV_EINTR => UVError.EINTR,
        c.UV_EINVAL => UVError.EINVAL,
        c.UV_EIO => UVError.EIO,
        c.UV_EISCONN => UVError.EISCONN,
        c.UV_EISDIR => UVError.EISDIR,
        c.UV_ELOOP => UVError.ELOOP,
        c.UV_EMFILE => UVError.EMFILE,
        c.UV_EMSGSIZE => UVError.EMSGSIZE,
        c.UV_ENAMETOOLONG => UVError.ENAMETOOLONG,
        c.UV_ENETDOWN => UVError.ENETDOWN,
        c.UV_ENETUNREACH => UVError.ENETUNREACH,
        c.UV_ENFILE => UVError.ENFILE,
        c.UV_ENOBUFS => UVError.ENOBUFS,
        c.UV_ENODEV => UVError.ENODEV,
        c.UV_ENOENT => UVError.ENOENT,
        c.UV_ENOMEM => UVError.ENOMEM,
        c.UV_ENONET => UVError.ENONET,
        c.UV_ENOPROTOOPT => UVError.ENOPROTOOPT,
        c.UV_ENOSPC => UVError.ENOSPC,
        c.UV_ENOSYS => UVError.ENOSYS,
        c.UV_ENOTCONN => UVError.ENOTCONN,
        c.UV_ENOTDIR => UVError.ENOTDIR,
        c.UV_ENOTEMPTY => UVError.ENOTEMPTY,
        c.UV_ENOTSOCK => UVError.ENOTSOCK,
        c.UV_ENOTSUP => UVError.ENOTSUP,
        c.UV_EPERM => UVError.EPERM,
        c.UV_EPIPE => UVError.EPIPE,
        c.UV_EPROTO => UVError.EPROTO,
        c.UV_EPROTONOSUPPORT => UVError.EPROTONOSUPPORT,
        c.UV_EPROTOTYPE => UVError.EPROTOTYPE,
        c.UV_ERANGE => UVError.ERANGE,
        c.UV_EROFS => UVError.EROFS,
        c.UV_ESHUTDOWN => UVError.ESHUTDOWN,
        c.UV_ESPIPE => UVError.ESPIPE,
        c.UV_ESRCH => UVError.ESRCH,
        c.UV_ETIMEDOUT => UVError.ETIMEDOUT,
        c.UV_ETXTBSY => UVError.ETXTBSY,
        c.UV_EXDEV => UVError.EXDEV,
        c.UV_UNKNOWN => UVError.UNKNOWN,
        c.UV_EOF => UVError.EOF,
        c.UV_ENXIO => UVError.ENXIO,
        c.UV_EMLINK => UVError.EMLINK,
        else => unreachable,
    };
}

fn cb_loop_sleep(handle: ?*c.uv_timer_t) callconv(.C) void {
    const aligned_ptr = @alignCast(@alignOf(@Frame(Loop.sleep)), handle.?.data);
    var frame = @ptrCast(*@Frame(Loop.sleep), aligned_ptr);
    resume frame;
}

pub const Loop = struct {
    uv_loop: c.uv_loop_t,

    fn init(self: *Loop) !void {
        self.* = Loop{ .uv_loop = undefined };
        try check_uv(c.uv_loop_init(&self.uv_loop));
    }

    fn close(self: *Loop) !void {
        var r: i32 = c.uv_loop_close(&self.uv_loop);
        try check_uv(r);
    }

    fn run(self: *Loop) !i32 {
        var r: i32 = c.uv_run(&self.uv_loop, c.uv_run_mode.UV_RUN_DEFAULT);
        try check_uv(r);
        return r;
    }

    fn stop(self: *Loop) void {
        c.uv_stop(&self.uv_loop);
    }

    fn alive(self: *Loop) bool {
        return c.uv_loop_alive(&self.uv_loop) != 0;
    }

    fn backendTimeout(self: *Loop) i32 {
        return c.uv_backend_timeout(&self.uv_loop);
    }

    fn now(self: *Loop) u64 {
        return c.uv_now(&self.uv_loop);
    }

    fn updateTime(self: *Loop) void {
        c.uv_update_time(&self.uv_loop);
    }

    fn sleep(self: *Loop, milliseconds: u64) !void {
        var handle: c.uv_timer_t = undefined;
        try check_uv(c.uv_timer_init(&self.uv_loop, &handle));
        handle.data = @frame();
        try check_uv(c.uv_timer_start(&handle, cb_loop_sleep, milliseconds, 0));
        suspend;
    }
};

var loop: Loop = undefined;

fn start_coroutine(id: i32) !void {
    warn("coroutine {}: sleeping for 1s...\n", .{id});
    try loop.sleep(1000);
    warn("coroutine {}: done!\n", .{id});
}

fn amain() !void {
    warn("amain: sleeping for 1s...\n", .{});
    try loop.sleep(1000);
    warn("amain: starting 3 coroutines...\n", .{});
    var c1 = async start_coroutine(1);
    var c2 = async start_coroutine(2);
    var c3 = async start_coroutine(3);
    warn("amain: waiting for coroutines to return...\n", .{});
    _ = await c1;
    _ = await c2;
    _ = await c3;
    warn("amain: done!\n", .{});
}

pub fn main() !void {
    try loop.init();
    _ = async amainWrap();

    var res: i32 = try loop.run();
    if (res > 0) warn("uv loop exited with more than one handle ({} remaining)\n", .{res});
}

fn amainWrap() void {
    amain() catch |e| {
        std.debug.warn("{}\n", .{e});
        if (@errorReturnTrace()) |trace| {
            std.debug.dumpStackTrace(trace.*);
        }
        std.process.exit(1);
    };
}