zig: graceful tcp client shutdown

main.zig

const std = @import("std");
const os = std.os;

const File = std.fs.File;

pub fn shutdown(fd: os.fd_t, how: i32) !void {
    const rc = os.system.shutdown(fd, how);
    switch (os.errno(rc)) {
        0 => return,
        os.EBADF => unreachable,
        os.EINVAL => return error.UnknownShutdownMethod,
        os.ENOTCONN => return error.SocketNotConnected,
        os.ENOTSOCK => return error.FileDescriptorNotSocket,
        else => unreachable,
    }
}

pub fn dispose(file: File) void {
    shutdown(file.handle, os.SHUT_RDWR) catch |err| switch (err) {
        error.SocketNotConnected => @panic(@errorName(err)),
        else => @panic(@errorName(err)),
    };

    // file.close();

    std.event.Loop.instance.?.close(file.handle);

    std.log.info("ok", .{});
}

pub fn readLoop(conn: File) !void {
    var buf: [4096]u8 = undefined;
    while (true) {
        const n = try os.read(conn.handle, &buf);
        if (n == 0) return error.EndOfStream;
    }
}

pub const io_mode = .evented;

pub fn main() !void {
    var conn = try std.net.tcpConnectToAddress(try std.net.Address.parseIp("127.0.0.1", 9000));
    var frame = async readLoop(conn);
    std.time.sleep(1000 * std.time.ns_per_ms);
    dispose(conn);
    try await frame;

    std.log.info("done!", .{});
}