1 // Copyright 2019 Developers of the Rand project.
2 //
3 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
4 // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
5 // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
6 // option. This file may not be copied, modified, or distributed
7 // except according to those terms.
8 #![allow(dead_code)]
9 use crate::{util::LazyUsize, Error};
10 use core::{num::NonZeroU32, ptr::NonNull};
11
12 cfg_if! {
13 if #[cfg(any(target_os = "netbsd", target_os = "openbsd", target_os = "android"))] {
14 use libc::__errno as errno_location;
15 } else if #[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "redox"))] {
16 use libc::__errno_location as errno_location;
17 } else if #[cfg(any(target_os = "solaris", target_os = "illumos"))] {
18 use libc::___errno as errno_location;
19 } else if #[cfg(any(target_os = "macos", target_os = "freebsd"))] {
20 use libc::__error as errno_location;
21 } else if #[cfg(target_os = "haiku")] {
22 use libc::_errnop as errno_location;
23 }
24 }
25
26 cfg_if! {
27 if #[cfg(target_os = "vxworks")] {
28 use libc::errnoGet as get_errno;
29 } else if #[cfg(target_os = "dragonfly")] {
30 // Until rust-lang/rust#29594 is stable, we cannot get the errno value
31 // on DragonFlyBSD. So we just return an out-of-range errno.
32 unsafe fn get_errno() -> libc::c_int { -1 }
33 } else {
34 unsafe fn get_errno() -> libc::c_int { *errno_location() }
35 }
36 }
37
last_os_error() -> Error38 pub fn last_os_error() -> Error {
39 let errno = unsafe { get_errno() };
40 if errno > 0 {
41 Error::from(NonZeroU32::new(errno as u32).unwrap())
42 } else {
43 Error::ERRNO_NOT_POSITIVE
44 }
45 }
46
47 // Fill a buffer by repeatedly invoking a system call. The `sys_fill` function:
48 // - should return -1 and set errno on failure
49 // - should return the number of bytes written on success
sys_fill_exact( mut buf: &mut [u8], sys_fill: impl Fn(&mut [u8]) -> libc::ssize_t, ) -> Result<(), Error>50 pub fn sys_fill_exact(
51 mut buf: &mut [u8],
52 sys_fill: impl Fn(&mut [u8]) -> libc::ssize_t,
53 ) -> Result<(), Error> {
54 while !buf.is_empty() {
55 let res = sys_fill(buf);
56 if res < 0 {
57 let err = last_os_error();
58 // We should try again if the call was interrupted.
59 if err.raw_os_error() != Some(libc::EINTR) {
60 return Err(err);
61 }
62 } else {
63 // We don't check for EOF (ret = 0) as the data we are reading
64 // should be an infinite stream of random bytes.
65 buf = &mut buf[(res as usize)..];
66 }
67 }
68 Ok(())
69 }
70
71 // A "weak" binding to a C function that may or may not be present at runtime.
72 // Used for supporting newer OS features while still building on older systems.
73 // F must be a function pointer of type `unsafe extern "C" fn`. Based off of the
74 // weak! macro in libstd.
75 pub struct Weak {
76 name: &'static str,
77 addr: LazyUsize,
78 }
79
80 impl Weak {
81 // Construct a binding to a C function with a given name. This function is
82 // unsafe because `name` _must_ be null terminated.
new(name: &'static str) -> Self83 pub const unsafe fn new(name: &'static str) -> Self {
84 Self {
85 name,
86 addr: LazyUsize::new(),
87 }
88 }
89
90 // Return a function pointer if present at runtime. Otherwise, return null.
ptr(&self) -> Option<NonNull<libc::c_void>>91 pub fn ptr(&self) -> Option<NonNull<libc::c_void>> {
92 let addr = self.addr.unsync_init(|| unsafe {
93 libc::dlsym(libc::RTLD_DEFAULT, self.name.as_ptr() as *const _) as usize
94 });
95 NonNull::new(addr as *mut _)
96 }
97 }
98
99 cfg_if! {
100 if #[cfg(any(target_os = "linux", target_os = "emscripten"))] {
101 use libc::open64 as open;
102 } else {
103 use libc::open;
104 }
105 }
106
107 // SAFETY: path must be null terminated, FD must be manually closed.
open_readonly(path: &str) -> Result<libc::c_int, Error>108 pub unsafe fn open_readonly(path: &str) -> Result<libc::c_int, Error> {
109 debug_assert_eq!(path.as_bytes().last(), Some(&0));
110 let fd = open(path.as_ptr() as *const _, libc::O_RDONLY | libc::O_CLOEXEC);
111 if fd < 0 {
112 return Err(last_os_error());
113 }
114 Ok(fd)
115 }
116