use crate::{
util_libc::{open_readonly, sys_fill_exact},
Error,
};
use core::{
cell::UnsafeCell,
mem::MaybeUninit,
sync::atomic::{AtomicUsize, Ordering::Relaxed},
};
const FILE_PATH: &str = "/dev/urandom\0";
const FD_UNINIT: usize = usize::max_value();
pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
let fd = get_rng_fd()?;
sys_fill_exact(dest, |buf| unsafe {
libc::read(fd, buf.as_mut_ptr() as *mut libc::c_void, buf.len())
})
}
fn get_rng_fd() -> Result<libc::c_int, Error> {
static FD: AtomicUsize = AtomicUsize::new(FD_UNINIT);
fn get_fd() -> Option<libc::c_int> {
match FD.load(Relaxed) {
FD_UNINIT => None,
val => Some(val as libc::c_int),
}
}
if let Some(fd) = get_fd() {
return Ok(fd);
}
static MUTEX: Mutex = Mutex::new();
unsafe { MUTEX.lock() };
let _guard = DropGuard(|| unsafe { MUTEX.unlock() });
if let Some(fd) = get_fd() {
return Ok(fd);
}
#[cfg(any(target_os = "android", target_os = "linux"))]
wait_until_rng_ready()?;
let fd = unsafe { open_readonly(FILE_PATH)? };
debug_assert!(fd >= 0 && (fd as usize) < FD_UNINIT);
FD.store(fd as usize, Relaxed);
Ok(fd)
}
#[cfg(any(target_os = "android", target_os = "linux"))]
fn wait_until_rng_ready() -> Result<(), Error> {
let fd = unsafe { open_readonly("/dev/random\0")? };
let mut pfd = libc::pollfd {
fd,
events: libc::POLLIN,
revents: 0,
};
let _guard = DropGuard(|| unsafe {
libc::close(fd);
});
loop {
let res = unsafe { libc::poll(&mut pfd, 1, -1) };
if res >= 0 {
debug_assert_eq!(res, 1); return Ok(());
}
let err = crate::util_libc::last_os_error();
match err.raw_os_error() {
Some(libc::EINTR) | Some(libc::EAGAIN) => continue,
_ => return Err(err),
}
}
}
struct Mutex(UnsafeCell<libc::pthread_mutex_t>);
impl Mutex {
const fn new() -> Self {
Self(UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER))
}
unsafe fn lock(&self) {
let r = libc::pthread_mutex_lock(self.0.get());
debug_assert_eq!(r, 0);
}
unsafe fn unlock(&self) {
let r = libc::pthread_mutex_unlock(self.0.get());
debug_assert_eq!(r, 0);
}
}
unsafe impl Sync for Mutex {}
struct DropGuard<F: FnMut()>(F);
impl<F: FnMut()> Drop for DropGuard<F> {
fn drop(&mut self) {
self.0()
}
}