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//! Process arguments and environment — the `std::env` subset, read from the

//! values the loader hands to `_start`.

//!

//! `argv`/`envp` are the classic C `char**` arrays (NUL-terminated C strings,

//! the arrays themselves NULL-terminated). We capture the pointers once at

//! startup and decode lazily, lossily as UTF-8 (matching how `std` treats

//! non-Unicode on a best-effort basis here).

use crate::alloc::string::String;

use core::ffi::{c_char, CStr};

use core::fmt;

use core::ptr;

use core::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};

static ARGC: AtomicUsize = AtomicUsize::new(0);

static ARGV: AtomicPtr<*const u8> = AtomicPtr::new(ptr::null_mut());

static ENVP: AtomicPtr<*const u8> = AtomicPtr::new(ptr::null_mut());

/// Record the loader-provided argument and environment vectors. Called once by

/// the [`entry!`](crate::entry) glue before user `main`.

pub(crate) unsafe fn init(argc: usize, argv: *const *const u8, envp: *const *const u8) {

ARGC.store(argc, Ordering::Relaxed);

ARGV.store(argv as *mut *const u8, Ordering::Relaxed);

ENVP.store(envp as *mut *const u8, Ordering::Relaxed);

}

/// WASI startup: `argv` is supplied by the command crt; the environment is

/// fetched via WASI `environ_get` into leaked buffers (process-lifetime).

#[cfg(target_family = "wasm")]

pub(crate) unsafe fn init_wasm(argc: usize, argv: *const *const u8) {

use crate::alloc::vec::Vec;

use crate::arch::wasi;

ARGC.store(argc, Ordering::Relaxed);

ARGV.store(argv as *mut *const u8, Ordering::Relaxed);

let mut count: usize = 0;

let mut buf_size: usize = 0;

if wasi::environ_sizes_get(&mut count, &mut buf_size) == 0 && count > 0 {

let mut ptrs: Vec<*mut u8> = Vec::with_capacity(count + 1);

ptrs.resize(count + 1, ptr::null_mut());

let mut buf: Vec<u8> = Vec::with_capacity(buf_size.max(1));

buf.resize(buf_size.max(1), 0);

if wasi::environ_get(ptrs.as_mut_ptr(), buf.as_mut_ptr()) == 0 {

ptrs[count] = ptr::null_mut(); // NULL-terminate the char** array

let leaked = ptrs.leak();

core::mem::forget(buf); // the strings the pointers reference

ENVP.store(leaked.as_mut_ptr() as *mut *const u8, Ordering::Relaxed);

}

#[inline]

unsafe fn cstr_to_string(p: *const u8) -> String {

let bytes = CStr::from_ptr(p as *const c_char).to_bytes();

String::from_utf8_lossy(bytes).into_owned()

}

/// Iterator over the program's command-line arguments. `args().next()` is the

/// program path, mirroring `std::env::args()`.

pub struct Args {

idx: usize,

argc: usize,

argv: *const *const u8,

}

impl Iterator for Args {

type Item = String;

fn next(&mut self) -> Option<String> {

if self.idx >= self.argc || self.argv.is_null() {

return None;

}

let p = unsafe { *self.argv.add(self.idx) };

self.idx += 1;

if p.is_null() {

return None;

}

Some(unsafe { cstr_to_string(p) })

}

impl ExactSizeIterator for Args {

fn len(&self) -> usize {

self.argc.saturating_sub(self.idx)

}

/// Returns the command-line arguments, the first being the program path.

pub fn args() -> Args {

Args {

idx: 0,

argc: ARGC.load(Ordering::Relaxed),

argv: ARGV.load(Ordering::Relaxed) as *const *const u8,

}

// The mutable environment: lazily seeded from the loader's `envp`, then owned by

// us so `set_var`/`remove_var` work (std keeps its own copy of `environ` too).

use crate::collections::BTreeMap;

use crate::sync::{Mutex, OnceLock};

static ENV_MAP: OnceLock<Mutex<BTreeMap<String, String>>> = OnceLock::new();

fn env_map() -> &'static Mutex<BTreeMap<String, String>> {

ENV_MAP.get_or_init(|| {

let mut m = BTreeMap::new();

let envp = ENVP.load(Ordering::Relaxed) as *const *const u8;

if !envp.is_null() {

let mut i = 0;

loop {

let p = unsafe { *envp.add(i) };

if p.is_null() {

break;

}

i += 1;

let bytes = unsafe { CStr::from_ptr(p as *const c_char).to_bytes() };

if let Some(eq) = bytes.iter().position(|&b| b == b'=') {

let k = String::from_utf8_lossy(&bytes[..eq]).into_owned();

let v = String::from_utf8_lossy(&bytes[eq + 1..]).into_owned();

m.insert(k, v);

}

Mutex::new(m)

})

}

/// Iterator over `(key, value)` environment pairs.

pub struct Vars {

inner: crate::alloc::vec::IntoIter<(String, String)>,

}

impl Iterator for Vars {

type Item = (String, String);

fn next(&mut self) -> Option<(String, String)> {

self.inner.next()

}

/// Returns a snapshot iterator over the environment variables.

pub fn vars() -> Vars {

let snapshot: crate::alloc::vec::Vec<(String, String)> = env_map()

.lock()

.unwrap()

.iter()

.map(|(k, v)| (k.clone(), v.clone()))

.collect();

Vars {

inner: snapshot.into_iter(),

}

/// The error type for [`var`].

#[derive(Debug, PartialEq, Eq, Clone)]

pub enum VarError {

/// The variable was not set.

NotPresent,

}

impl fmt::Display for VarError {

fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

match self {

VarError::NotPresent => f.write_str("environment variable not found"),

}

impl core::error::Error for VarError {}

/// Fetch the environment variable `key`. Mirrors `std::env::var`.

pub fn var(key: &str) -> Result<String, VarError> {

env_map()

.lock()

.unwrap()

.get(key)

.cloned()

.ok_or(VarError::NotPresent)

}

/// Set the environment variable `key` to `value`.

pub fn set_var<K: AsRef<str>, V: AsRef<str>>(key: K, value: V) {

env_map()

.lock()

.unwrap()

.insert(key.as_ref().into(), value.as_ref().into());

}

/// Remove the environment variable `key`.

pub fn remove_var<K: AsRef<str>>(key: K) {

env_map().lock().unwrap().remove(key.as_ref());

}

/// Returns the current working directory.

pub fn current_dir() -> crate::io::Result<crate::path::PathBuf> {

let mut buf = [0u8; 4096];

crate::syscall::getcwd(&mut buf).map_err(crate::io::Error::from)?;

let end = buf.iter().position(|&b| b == 0).unwrap_or(buf.len());

Ok(crate::path::PathBuf::from(

String::from_utf8_lossy(&buf[..end]).into_owned(),

))

}

/// Change the current working directory.

pub fn set_current_dir<P: AsRef<crate::path::Path>>(path: P) -> crate::io::Result<()> {

let c = crate::ffi::CString::new(path.as_ref().as_str().as_bytes())

.map_err(|_| crate::io::Error::from(crate::io::ErrorKind::InvalidInput))?;

crate::syscall::chdir(&c).map_err(crate::io::Error::from)

}

/// Returns the OS temporary-files directory (`$TMPDIR`, else `/tmp`).

pub fn temp_dir() -> crate::path::PathBuf {

match var("TMPDIR") {

Ok(d) if !d.is_empty() => crate::path::PathBuf::from(d),

_ => crate::path::PathBuf::from("/tmp"),

}

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