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extern crate libc;
use std::num::NonZeroUsize;
use std::{mem, ptr};
pub(crate) fn num_threads() -> Option<NonZeroUsize> {
// Safety: `sysctl` and `getpid` are both thread-safe.
// `kip` is only accessed if sysctl() succeeds and agrees with the expected size,
// and the data only trusted if both its embedded size and pid match expectations
unsafe {
let pid = libc::getpid();
let mib: [libc::c_int; 4] = [libc::CTL_KERN, libc::KERN_PROC, libc::KERN_PROC_PID, pid];
let mut kip: libc::kinfo_proc = mem::zeroed();
let expected_kip_len = mem::size_of_val(&kip);
let mut kip_len = expected_kip_len;
let ret = libc::sysctl(
mib.as_ptr(),
mib.len() as u32,
&mut kip as *mut _ as *mut libc::c_void,
&mut kip_len,
ptr::null(),
0,
);
if ret == 0
&& kip_len == expected_kip_len
&& kip.ki_structsize == expected_kip_len as i32
&& kip.ki_pid == pid
{
NonZeroUsize::new(kip.ki_numthreads as usize)
} else {
None
}
}
}
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