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#![allow(unsafe_op_in_unsafe_fn)]
use core::slice::memchr;
use libc::c_char;
use crate::ffi::{CStr, OsStr, OsString};
use crate::os::unix::prelude::*;
use crate::sync::{PoisonError, RwLock};
use crate::sys::common::small_c_string::run_with_cstr;
use crate::sys::cvt;
use crate::{fmt, io, vec};
pub struct Env {
iter: vec::IntoIter<(OsString, OsString)>,
}
// FIXME(https://github.com/rust-lang/rust/issues/114583): Remove this when <OsStr as Debug>::fmt matches <str as Debug>::fmt.
pub struct EnvStrDebug<'a> {
slice: &'a [(OsString, OsString)],
}
impl fmt::Debug for EnvStrDebug<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let Self { slice } = self;
f.debug_list()
.entries(slice.iter().map(|(a, b)| (a.to_str().unwrap(), b.to_str().unwrap())))
.finish()
}
}
impl Env {
pub fn str_debug(&self) -> impl fmt::Debug + '_ {
let Self { iter } = self;
EnvStrDebug { slice: iter.as_slice() }
}
}
impl fmt::Debug for Env {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let Self { iter } = self;
f.debug_list().entries(iter.as_slice()).finish()
}
}
impl !Send for Env {}
impl !Sync for Env {}
impl Iterator for Env {
type Item = (OsString, OsString);
fn next(&mut self) -> Option<(OsString, OsString)> {
self.iter.next()
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
// Use `_NSGetEnviron` on Apple platforms.
//
// `_NSGetEnviron` is the documented alternative (see `man environ`), and has
// been available since the first versions of both macOS and iOS.
//
// Nowadays, specifically since macOS 10.8, `environ` has been exposed through
// `libdyld.dylib`, which is linked via. `libSystem.dylib`:
// <https://github.com/apple-oss-distributions/dyld/blob/dyld-1160.6/libdyld/libdyldGlue.cpp#L913>
//
// So in the end, it likely doesn't really matter which option we use, but the
// performance cost of using `_NSGetEnviron` is extremely miniscule, and it
// might be ever so slightly more supported, so let's just use that.
//
// NOTE: The header where this is defined (`crt_externs.h`) was added to the
// iOS 13.0 SDK, which has been the source of a great deal of confusion in the
// past about the availability of this API.
//
// NOTE(madsmtm): Neither this nor using `environ` has been verified to not
// cause App Store rejections; if this is found to be the case, an alternative
// implementation of this is possible using `[NSProcessInfo environment]`
// - which internally uses `_NSGetEnviron` and a system-wide lock on the
// environment variables to protect against `setenv`, so using that might be
// desirable anyhow? Though it also means that we have to link to Foundation.
#[cfg(target_vendor = "apple")]
pub unsafe fn environ() -> *mut *const *const c_char {
libc::_NSGetEnviron() as *mut *const *const c_char
}
// Use the `environ` static which is part of POSIX.
#[cfg(not(target_vendor = "apple"))]
pub unsafe fn environ() -> *mut *const *const c_char {
unsafe extern "C" {
static mut environ: *const *const c_char;
}
&raw mut environ
}
static ENV_LOCK: RwLock<()> = RwLock::new(());
pub fn env_read_lock() -> impl Drop {
ENV_LOCK.read().unwrap_or_else(PoisonError::into_inner)
}
/// Returns a vector of (variable, value) byte-vector pairs for all the
/// environment variables of the current process.
pub fn env() -> Env {
unsafe {
let _guard = env_read_lock();
let mut environ = *environ();
let mut result = Vec::new();
if !environ.is_null() {
while !(*environ).is_null() {
if let Some(key_value) = parse(CStr::from_ptr(*environ).to_bytes()) {
result.push(key_value);
}
environ = environ.add(1);
}
}
return Env { iter: result.into_iter() };
}
fn parse(input: &[u8]) -> Option<(OsString, OsString)> {
// Strategy (copied from glibc): Variable name and value are separated
// by an ASCII equals sign '='. Since a variable name must not be
// empty, allow variable names starting with an equals sign. Skip all
// malformed lines.
if input.is_empty() {
return None;
}
let pos = memchr::memchr(b'=', &input[1..]).map(|p| p + 1);
pos.map(|p| {
(
OsStringExt::from_vec(input[..p].to_vec()),
OsStringExt::from_vec(input[p + 1..].to_vec()),
)
})
}
}
pub fn getenv(k: &OsStr) -> Option<OsString> {
// environment variables with a nul byte can't be set, so their value is
// always None as well
run_with_cstr(k.as_bytes(), &|k| {
let _guard = env_read_lock();
let v = unsafe { libc::getenv(k.as_ptr()) } as *const libc::c_char;
if v.is_null() {
Ok(None)
} else {
// SAFETY: `v` cannot be mutated while executing this line since we've a read lock
let bytes = unsafe { CStr::from_ptr(v) }.to_bytes().to_vec();
Ok(Some(OsStringExt::from_vec(bytes)))
}
})
.ok()
.flatten()
}
pub unsafe fn setenv(k: &OsStr, v: &OsStr) -> io::Result<()> {
run_with_cstr(k.as_bytes(), &|k| {
run_with_cstr(v.as_bytes(), &|v| {
let _guard = ENV_LOCK.write();
cvt(libc::setenv(k.as_ptr(), v.as_ptr(), 1)).map(drop)
})
})
}
pub unsafe fn unsetenv(n: &OsStr) -> io::Result<()> {
run_with_cstr(n.as_bytes(), &|nbuf| {
let _guard = ENV_LOCK.write();
cvt(libc::unsetenv(nbuf.as_ptr())).map(drop)
})
}
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