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//! Implementation for Hermit
use crate::Error;
use core::{mem::MaybeUninit, num::NonZeroU32};
/// Minimum return value which we should get from syscalls in practice,
/// because Hermit uses positive `i32`s for error codes:
/// https://github.com/hermitcore/libhermit-rs/blob/main/src/errno.rs
const MIN_RET_CODE: isize = -(i32::MAX as isize);
extern "C" {
fn sys_read_entropy(buffer: *mut u8, length: usize, flags: u32) -> isize;
}
pub fn getrandom_inner(mut dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
while !dest.is_empty() {
let res = unsafe { sys_read_entropy(dest.as_mut_ptr() as *mut u8, dest.len(), 0) };
// Positive `isize`s can be safely casted to `usize`
if res > 0 && (res as usize) <= dest.len() {
dest = &mut dest[res as usize..];
} else {
let err = match res {
MIN_RET_CODE..=-1 => NonZeroU32::new(-res as u32).unwrap().into(),
_ => Error::UNEXPECTED,
};
return Err(err);
}
}
Ok(())
}
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