operate

fn operate(userdata: ?*anyopaque, operation: Io.Operation) Io.Cancelable!Io.Operation.Result {
    const ev: *Evented = @ptrCast(@alignCast(userdata));
    switch (operation) {
        .file_read_streaming => |o| return .{
            .file_read_streaming = ev.fileReadStreaming(o.file, o.data) catch |err| switch (err) {
                error.Canceled => |e| return e,
                else => |e| e,
            },
        },
        .file_write_streaming => |o| return .{
            .file_write_streaming = ev.fileWriteStreaming(
                o.file,
                o.header,
                o.data,
                o.splat,
            ) catch |err| switch (err) {
                error.Canceled => |e| return e,
                else => |e| e,
            },
        },
        .device_io_control => |*o| return .{ .device_io_control = try deviceIoControl(o) },
        .net_receive => @panic("TODO implement net_receive operation"),
        .net_send => @panic("TODO implement net_send operation"),
        .net_read => @panic("TODO implement net_read operation"),
        .net_write => @panic("TODO implement net_write operation"),
    }
}