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//! Implementation for iOS, tvOS, and watchOS where `getentropy` is unavailable.
use crate::Error;
use core::{ffi::c_void, mem::MaybeUninit};
// libsystem contains the libc of Darwin, and every binary ends up linked against it either way. This
// makes it a more lightweight choice compared to `Security.framework`.
extern "C" {
// This RNG uses a thread-local CSPRNG to provide data, which is seeded by the operating system's root CSPRNG.
// Its the best option after `getentropy` on modern Darwin-based platforms that also avoids the
// high startup costs and linking of Security.framework.
//
// While its just an implementation detail, `Security.framework` just calls into this anyway.
fn CCRandomGenerateBytes(bytes: *mut c_void, size: usize) -> i32;
}
pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
let ret = unsafe { CCRandomGenerateBytes(dest.as_mut_ptr() as *mut c_void, dest.len()) };
// kCCSuccess (from CommonCryptoError.h) is always zero.
if ret != 0 {
Err(Error::IOS_SEC_RANDOM)
} else {
Ok(())
}
}