The ffi module

Let’s start with the modules that don’t depend on any others and work our way from there. The ffi module contains mappings to the syscalls and data structures we need to communicate with the operating system. We’ll also explain how epoll works in detail once we have presented the syscalls.

It’s only a few lines of code, so I’ll place the first part here so it’s easier to keep track of where we are in the file since there’s quite a bit to explain. Open the ffi.rs file and write the following lines of code:

ch04/a-epoll/src/ffi.rs

pub const EPOLL_CTL_ADD: i32 = 1;
pub const EPOLLIN: i32 = 0x1;
pub const EPOLLET: i32 = 1 << 31;
#[link(name = "c")]
extern "C" {
  pub fn epoll_create(size: i32) -> i32;
  pub fn close(fd: i32) -> i32;
  pub fn epoll_ctl(epfd: i32, op: i32, fd: i32, event: *mut Event) -> i32;
  pub fn epoll_wait(epfd: i32, events...