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//! Implementation for Hermit
use crate::Error;
use core::mem::MaybeUninit;
extern "C" {
fn sys_read_entropy(buffer: *mut u8, length: usize, flags: u32) -> isize;
// Note that `sys_secure_rand32/64` are implemented using `sys_read_entropy`:
// https://github.com/hermit-os/kernel/blob/430da84/src/syscalls/entropy.rs#L62-L104
// But this may change in future and can depend on compilation target,
// so to future-proof we use these "syscalls".
fn sys_secure_rand32(value: *mut u32) -> i32;
fn sys_secure_rand64(value: *mut u64) -> i32;
}
#[inline]
pub fn inner_u32() -> Result<u32, Error> {
let mut res = MaybeUninit::uninit();
let ret = unsafe { sys_secure_rand32(res.as_mut_ptr()) };
match ret {
0 => Ok(unsafe { res.assume_init() }),
-1 => Err(Error::UNSUPPORTED),
_ => Err(Error::UNEXPECTED),
}
}
#[inline]
pub fn inner_u64() -> Result<u64, Error> {
let mut res = MaybeUninit::uninit();
let ret = unsafe { sys_secure_rand64(res.as_mut_ptr()) };
match ret {
0 => Ok(unsafe { res.assume_init() }),
-1 => Err(Error::UNSUPPORTED),
_ => Err(Error::UNEXPECTED),
}
}
#[inline]
pub fn fill_inner(mut dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
while !dest.is_empty() {
let res = unsafe { sys_read_entropy(dest.as_mut_ptr().cast::<u8>(), dest.len(), 0) };
match res {
res if res > 0 => {
let len = usize::try_from(res).map_err(|_| Error::UNEXPECTED)?;
dest = dest.get_mut(len..).ok_or(Error::UNEXPECTED)?;
}
code => {
let code = i32::try_from(code).map_err(|_| Error::UNEXPECTED)?;
return Err(Error::from_neg_error_code(code));
}
}
}
Ok(())
}
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