getrandom/
util_libc.rs

1use crate::Error;
2use core::mem::MaybeUninit;
3
4cfg_if! {
5    if #[cfg(any(target_os = "netbsd", target_os = "openbsd", target_os = "android"))] {
6        use libc::__errno as errno_location;
7    } else if #[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "hurd", target_os = "redox", target_os = "dragonfly"))] {
8        use libc::__errno_location as errno_location;
9    } else if #[cfg(any(target_os = "solaris", target_os = "illumos"))] {
10        use libc::___errno as errno_location;
11    } else if #[cfg(any(target_os = "macos", target_os = "freebsd"))] {
12        use libc::__error as errno_location;
13    } else if #[cfg(target_os = "haiku")] {
14        use libc::_errnop as errno_location;
15    } else if #[cfg(target_os = "nto")] {
16        use libc::__get_errno_ptr as errno_location;
17    } else if #[cfg(any(all(target_os = "horizon", target_arch = "arm"), target_os = "vita"))] {
18        extern "C" {
19            // Not provided by libc: https://github.com/rust-lang/libc/issues/1995
20            fn __errno() -> *mut libc::c_int;
21        }
22        use __errno as errno_location;
23    } else if #[cfg(target_os = "aix")] {
24        use libc::_Errno as errno_location;
25    }
26}
27
28cfg_if! {
29    if #[cfg(target_os = "vxworks")] {
30        use libc::errnoGet as get_errno;
31    } else {
32        unsafe fn get_errno() -> libc::c_int { *errno_location() }
33    }
34}
35
36pub(crate) fn last_os_error() -> Error {
37    let errno: libc::c_int = unsafe { get_errno() };
38
39    // c_int-to-u32 conversion is lossless for nonnegative values if they are the same size.
40    const _: () = assert!(core::mem::size_of::<libc::c_int>() == core::mem::size_of::<u32>());
41
42    match u32::try_from(errno) {
43        Ok(code) if code != 0 => Error::from_os_error(code),
44        _ => Error::ERRNO_NOT_POSITIVE,
45    }
46}
47
48/// Fill a buffer by repeatedly invoking `sys_fill`.
49///
50/// The `sys_fill` function:
51///   - should return -1 and set errno on failure
52///   - should return the number of bytes written on success
53#[allow(dead_code)]
54pub(crate) fn sys_fill_exact(
55    mut buf: &mut [MaybeUninit<u8>],
56    sys_fill: impl Fn(&mut [MaybeUninit<u8>]) -> libc::ssize_t,
57) -> Result<(), Error> {
58    while !buf.is_empty() {
59        let res = sys_fill(buf);
60        match res {
61            res if res > 0 => {
62                let len = usize::try_from(res).map_err(|_| Error::UNEXPECTED)?;
63                buf = buf.get_mut(len..).ok_or(Error::UNEXPECTED)?;
64            }
65            -1 => {
66                let err = last_os_error();
67                // We should try again if the call was interrupted.
68                if err.raw_os_error() != Some(libc::EINTR) {
69                    return Err(err);
70                }
71            }
72            // Negative return codes not equal to -1 should be impossible.
73            // EOF (ret = 0) should be impossible, as the data we are reading
74            // should be an infinite stream of random bytes.
75            _ => return Err(Error::UNEXPECTED),
76        }
77    }
78    Ok(())
79}
getrandom/util_libc.rs

getrandom/
util_libc.rs
