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use crate::io;
use crate::mem;
use crate::sync;
use crate::sys::c;
#[derive(Clone, Copy, Debug, PartialEq)]
enum HashMapRng {
Preferred,
Fallback,
}
pub fn hashmap_random_keys() -> (u64, u64) {
match get_hashmap_rng() {
HashMapRng::Preferred => {
preferred_rng().expect("couldn't generate random bytes with preferred RNG")
}
HashMapRng::Fallback => {
fallback_rng().expect("couldn't generate random bytes with fallback RNG")
}
}
}
fn get_hashmap_rng() -> HashMapRng {
static VALUE: sync::OnceLock<HashMapRng> = sync::OnceLock::new();
*VALUE.get_or_init(choose_hashmap_rng)
}
fn choose_hashmap_rng() -> HashMapRng {
let preferred_error = match preferred_rng() {
Ok(_) => return HashMapRng::Preferred,
Err(e) => e,
};
match fallback_rng() {
Ok(_) => return HashMapRng::Fallback,
Err(fallback_error) => panic!(
"preferred RNG broken: `{}`, fallback RNG broken: `{}`",
preferred_error, fallback_error
),
}
}
fn preferred_rng() -> Result<(u64, u64), io::Error> {
use crate::ptr;
let mut v = (0, 0);
let ret = unsafe {
c::BCryptGenRandom(
ptr::null_mut(),
&mut v as *mut _ as *mut u8,
mem::size_of_val(&v) as c::ULONG,
c::BCRYPT_USE_SYSTEM_PREFERRED_RNG,
)
};
if ret == 0 { Ok(v) } else { Err(io::Error::last_os_error()) }
}
#[cfg(not(target_vendor = "uwp"))]
fn fallback_rng() -> Result<(u64, u64), io::Error> {
let mut v = (0, 0);
let ret =
unsafe { c::RtlGenRandom(&mut v as *mut _ as *mut u8, mem::size_of_val(&v) as c::ULONG) };
if ret != 0 { Ok(v) } else { Err(io::Error::last_os_error()) }
}
#[cfg(target_vendor = "uwp")]
fn fallback_rng() -> Result<(u64, u64), io::Error> {
Err(io::const_io_error!(io::ErrorKind::Unsupported, "RtlGenRandom() not supported on UWP"))
}