rustpython-host_env 0.6.0

// spell-checker:disable
// TODO: we can move more os-specific bindings/interfaces from stdlib::{os, posix, nt} to here

use crate::crt_fd;
#[cfg(windows)]
use crate::fs;
#[cfg(windows)]
pub use crate::posix::rename;
#[cfg(any(unix, target_os = "wasi"))]
pub use crate::posix_unix_like::rename;
#[cfg(any(unix, windows))]
use core::ffi::CStr;
use core::str::Utf8Error;
#[cfg(windows)]
use core::time::Duration;
use std::{
    env,
    ffi::{OsStr, OsString},
    io,
    path::PathBuf,
    process::ExitCode,
};
#[cfg(windows)]
use {
    std::{os::windows::io::AsRawHandle, path::Path},
    windows_sys::Win32::{
        Foundation::FILETIME,
        Storage::FileSystem::{FILE_FLAG_BACKUP_SEMANTICS, SetFilePointerEx, SetFileTime},
        System::SystemInformation::{GetSystemInfo, SYSTEM_INFO},
    },
};

bitflagset::bitflag! {
    #[derive(Copy, Clone, Debug, PartialEq, Eq)]
    #[repr(u8)]
    pub enum AccessFlag {
        X = 0,
        W = 1,
        R = 2,
    }
}

bitflagset::bitflagset! {
    #[derive(Copy, Clone, PartialEq, Eq)]
    pub struct AccessMode(u8): AccessFlag
}

pub const F_OK: u8 = AccessMode::empty().bits();
pub const X_OK: u8 = AccessMode::from_element(AccessFlag::X).bits();
pub const W_OK: u8 = AccessMode::from_element(AccessFlag::W).bits();
pub const R_OK: u8 = AccessMode::from_element(AccessFlag::R).bits();

#[cfg(any(unix, target_os = "wasi"))]
pub use libc::AT_FDCWD;
#[cfg(not(any(unix, target_os = "wasi")))]
pub const AT_FDCWD: i32 = -100;

#[cfg(unix)]
pub use libc::{AT_REMOVEDIR, AT_SYMLINK_FOLLOW, AT_SYMLINK_NOFOLLOW};

#[cfg(any(
    target_os = "freebsd",
    target_os = "linux",
    target_os = "netbsd",
    target_vendor = "apple"
))]
pub use libc::AT_EACCESS;

/// bionic does not export `AT_EACCESS`; the value is the Linux `fcntl.h` one.
#[cfg(target_os = "android")]
pub const AT_EACCESS: i32 = 0x200;

#[cfg(all(unix, not(target_os = "redox")))]
pub use libc::{ST_NOSUID, ST_RDONLY};

/// `open(2)` flags. libc on hosts that bind them; Darwin/BSD numbers on
/// `wasm32-unknown-unknown`, matching the guest errno table.
#[cfg(any(unix, windows, target_os = "wasi"))]
pub use libc::{O_APPEND, O_CREAT, O_EXCL, O_RDONLY, O_RDWR, O_TRUNC, O_WRONLY};

#[cfg(unix)]
pub use libc::{O_ACCMODE, O_CLOEXEC, O_DIRECTORY, O_NOFOLLOW, O_NONBLOCK};

#[cfg(any(
    target_os = "android",
    target_os = "dragonfly",
    target_os = "freebsd",
    target_os = "linux",
    target_os = "macos",
    target_os = "netbsd",
    target_os = "redox"
))]
pub use libc::{O_ASYNC, O_NDELAY, O_NOCTTY};

#[cfg(any(
    target_os = "android",
    target_os = "freebsd",
    target_os = "linux",
    target_os = "macos",
    target_os = "netbsd"
))]
pub use libc::O_DSYNC;

#[cfg(any(
    target_os = "android",
    target_os = "dragonfly",
    target_os = "freebsd",
    target_os = "linux",
    target_os = "macos",
    target_os = "netbsd"
))]
pub use libc::O_SYNC;

#[cfg(any(
    target_os = "dragonfly",
    target_os = "freebsd",
    target_os = "macos",
    target_os = "netbsd",
    target_os = "redox"
))]
pub use libc::O_FSYNC;

#[cfg(any(target_os = "linux", target_os = "android"))]
pub use libc::{O_DIRECT, O_LARGEFILE, O_NOATIME, O_PATH, O_RSYNC, O_TMPFILE};

#[cfg(target_os = "freebsd")]
pub use libc::{O_DIRECT, O_PATH};

#[cfg(target_os = "redox")]
pub use libc::O_PATH;

#[cfg(target_os = "netbsd")]
pub use libc::{O_DIRECT, O_RSYNC};

#[cfg(target_os = "dragonfly")]
pub use libc::O_DIRECT;

#[cfg(any(target_os = "macos", target_os = "ios"))]
pub use libc::{O_EVTONLY, O_EXEC, O_EXLOCK, O_NOFOLLOW_ANY, O_SEARCH, O_SHLOCK, O_SYMLINK};

#[cfg(any(
    target_os = "dragonfly",
    target_os = "freebsd",
    target_os = "netbsd",
    target_os = "redox"
))]
pub use libc::{O_EXLOCK, O_SHLOCK};

#[cfg(target_os = "redox")]
pub use libc::O_SYMLINK;

#[cfg(windows)]
pub use libc::{O_BINARY, O_NOINHERIT, O_RANDOM, O_SEQUENTIAL, O_TEMPORARY, O_TEXT};

#[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
mod wasm_oflag {
    pub const O_RDONLY: i32 = 0x0000;
    pub const O_WRONLY: i32 = 0x0001;
    pub const O_RDWR: i32 = 0x0002;
    pub const O_ACCMODE: i32 = 0x0003;
    pub const O_NONBLOCK: i32 = 0x0004;
    pub const O_APPEND: i32 = 0x0008;
    pub const O_SYNC: i32 = 0x0080;
    pub const O_NOFOLLOW: i32 = 0x0100;
    pub const O_CREAT: i32 = 0x0200;
    pub const O_TRUNC: i32 = 0x0400;
    pub const O_EXCL: i32 = 0x0800;
    pub const O_DIRECTORY: i32 = 0x0010_0000;
    pub const O_CLOEXEC: i32 = 0x0100_0000;
    pub const O_NDELAY: i32 = O_NONBLOCK;
}

#[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
pub use wasm_oflag::*;

bitflagset::bitflag! {
    /// BSD `chflags` bits. Values are bit *positions*; masks are `1 << pos`.
    #[derive(Copy, Clone, Debug, PartialEq, Eq)]
    #[repr(u8)]
    pub enum ChFlag {
        UfNodump = 0,
        UfImmutable = 1,
        UfAppend = 2,
        UfOpaque = 3,
        UfNounlink = 4,
        UfCompressed = 5,
        UfTracked = 6,
        UfDatavault = 7,
        UfHidden = 15,
        SfArchived = 16,
        SfImmutable = 17,
        SfAppend = 18,
        SfNounlink = 20,
        SfSnapshot = 21,
        SfFirmlink = 23,
        SfDataless = 30,
    }
}

bitflagset::bitflagset! {
    #[derive(Copy, Clone, PartialEq, Eq)]
    pub struct ChFlags(u32): ChFlag
}

impl ChFlags {
    /// Owner-settable bits, including reserved user-flag positions.
    pub const UF_SETTABLE: Self = Self::from_bits_retain(0x0000ffff);
    pub const SF_SETTABLE: Self = Self::from_bits_retain(if cfg!(target_os = "macos") {
        0x3fff0000
    } else {
        0xffff0000
    });
    #[cfg(target_os = "macos")]
    pub const SF_SUPPORTED: Self = Self::from_bits_retain(0x009f0000);
    #[cfg(target_os = "macos")]
    pub const SF_SYNTHETIC: Self = Self::from_bits_retain(0xc0000000);
}

pub const UF_NODUMP: u32 = ChFlags::from_element(ChFlag::UfNodump).bits();
pub const UF_IMMUTABLE: u32 = ChFlags::from_element(ChFlag::UfImmutable).bits();
pub const UF_APPEND: u32 = ChFlags::from_element(ChFlag::UfAppend).bits();
pub const UF_OPAQUE: u32 = ChFlags::from_element(ChFlag::UfOpaque).bits();
pub const UF_NOUNLINK: u32 = ChFlags::from_element(ChFlag::UfNounlink).bits();
pub const UF_COMPRESSED: u32 = ChFlags::from_element(ChFlag::UfCompressed).bits();
pub const UF_TRACKED: u32 = ChFlags::from_element(ChFlag::UfTracked).bits();
pub const UF_DATAVAULT: u32 = ChFlags::from_element(ChFlag::UfDatavault).bits();
pub const UF_HIDDEN: u32 = ChFlags::from_element(ChFlag::UfHidden).bits();
pub const UF_SETTABLE: u32 = ChFlags::UF_SETTABLE.bits();
pub const SF_ARCHIVED: u32 = ChFlags::from_element(ChFlag::SfArchived).bits();
pub const SF_IMMUTABLE: u32 = ChFlags::from_element(ChFlag::SfImmutable).bits();
pub const SF_APPEND: u32 = ChFlags::from_element(ChFlag::SfAppend).bits();
pub const SF_NOUNLINK: u32 = ChFlags::from_element(ChFlag::SfNounlink).bits();
pub const SF_SNAPSHOT: u32 = ChFlags::from_element(ChFlag::SfSnapshot).bits();
pub const SF_FIRMLINK: u32 = ChFlags::from_element(ChFlag::SfFirmlink).bits();
pub const SF_DATALESS: u32 = ChFlags::from_element(ChFlag::SfDataless).bits();
pub const SF_SETTABLE: u32 = ChFlags::SF_SETTABLE.bits();
#[cfg(target_os = "macos")]
pub const SF_SUPPORTED: u32 = ChFlags::SF_SUPPORTED.bits();
#[cfg(target_os = "macos")]
pub const SF_SYNTHETIC: u32 = ChFlags::SF_SYNTHETIC.bits();

const _: () = {
    assert!(UF_NODUMP == 0x00000001);
    assert!(UF_IMMUTABLE == 0x00000002);
    assert!(UF_APPEND == 0x00000004);
    assert!(UF_OPAQUE == 0x00000008);
    assert!(UF_NOUNLINK == 0x00000010);
    assert!(UF_COMPRESSED == 0x00000020);
    assert!(UF_TRACKED == 0x00000040);
    assert!(UF_DATAVAULT == 0x00000080);
    assert!(UF_HIDDEN == 0x00008000);
    assert!(UF_SETTABLE == 0x0000ffff);
    assert!(SF_ARCHIVED == 0x00010000);
    assert!(SF_IMMUTABLE == 0x00020000);
    assert!(SF_APPEND == 0x00040000);
    assert!(SF_NOUNLINK == 0x00100000);
    assert!(SF_SNAPSHOT == 0x00200000);
    assert!(SF_FIRMLINK == 0x00800000);
    assert!(SF_DATALESS == 0x40000000);
};

/// Solaris door/port and BSD whiteout. `_stat` publishes 0 where the
/// platform has no such file type.
pub const S_IFDOOR: u32 = 0;
pub const S_IFPORT: u32 = 0;
pub const S_IFWHT: u32 = if cfg!(target_os = "macos") {
    0o160000
} else {
    0
};

#[cfg(not(any(unix, windows, target_os = "wasi")))]
pub fn rename(
    from: impl AsRef<std::path::Path>,
    from_fd: Option<crt_fd::Borrowed<'_>>,
    to: impl AsRef<std::path::Path>,
    to_fd: Option<crt_fd::Borrowed<'_>>,
) -> io::Result<()> {
    if from_fd.is_none() && to_fd.is_none() {
        std::fs::rename(from, to)
    } else {
        Err(io::Error::new(
            io::ErrorKind::Unsupported,
            "renameat is not available on this platform",
        ))
    }
}

/// Convert exit code to std::process::ExitCode
///
/// On Windows, this supports the full u32 range including STATUS_CONTROL_C_EXIT (0xC000013A).
/// On other platforms, only the lower 8 bits are used.
pub fn exit_code(code: u32) -> ExitCode {
    #[cfg(windows)]
    {
        // For large exit codes like STATUS_CONTROL_C_EXIT (0xC000013A),
        // we need to call std::process::exit() directly since ExitCode::from(u8)
        // would truncate the value, and ExitCode::from_raw() is still unstable.
        // FIXME: side effect in exit_code is not ideal.
        if code > u8::MAX as u32 {
            std::process::exit(code as i32)
        }
    }
    ExitCode::from(code as u8)
}

pub fn current_dir() -> io::Result<PathBuf> {
    env::current_dir()
}

#[must_use]
pub fn temp_dir() -> PathBuf {
    env::temp_dir()
}

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

pub fn var_os(key: impl AsRef<OsStr>) -> Option<OsString> {
    env::var_os(key)
}

#[must_use]
pub fn vars_os() -> env::VarsOs {
    env::vars_os()
}

#[must_use]
pub fn vars() -> env::Vars {
    env::vars()
}

/// # Safety
/// The caller must ensure no other threads can concurrently read or write
/// the process environment while this mutation is performed.
pub unsafe fn set_var(key: impl AsRef<OsStr>, value: impl AsRef<OsStr>) {
    unsafe { env::set_var(key, value) };
}

/// # Safety
/// The caller must ensure no other threads can concurrently read or write
/// the process environment while this mutation is performed.
pub unsafe fn remove_var(key: impl AsRef<OsStr>) {
    unsafe { env::remove_var(key) };
}

/// Publish the working directory as `=X:` for the drive it is on.
///
/// CRT `_wspawnve` / `_wexecve` walk the environment for the first `=X:`
/// entry with no bound; a process that was not started by cmd.exe has none
/// and that walk runs off the block. A UNC-like path is on no drive and
/// publishes nothing.
#[cfg(windows)]
pub fn publish_drive_current_directory() -> io::Result<()> {
    use std::os::windows::ffi::OsStrExt;
    use windows_sys::Win32::System::Environment::SetEnvironmentVariableW;

    let mut cwd_wide: Vec<u16> = env::current_dir()?.as_os_str().encode_wide().collect();
    let unc_like = cwd_wide.len() >= 2
        && ((cwd_wide[0] == b'\\' as u16 && cwd_wide[1] == b'\\' as u16)
            || (cwd_wide[0] == b'/' as u16 && cwd_wide[1] == b'/' as u16));
    if unc_like || cwd_wide.is_empty() {
        return Ok(());
    }
    let env_name = [b'=' as u16, cwd_wide[0], b':' as u16, 0];
    cwd_wide.push(0);
    let ok = unsafe { SetEnvironmentVariableW(env_name.as_ptr(), cwd_wide.as_ptr()) };
    if ok == 0 {
        Err(io::Error::last_os_error())
    } else {
        Ok(())
    }
}

/// Whether the process environment already has an `=X:` drive-cwd entry.
#[cfg(windows)]
pub fn environment_has_drive_current_directory() -> bool {
    use windows_sys::Win32::System::Environment::{
        FreeEnvironmentStringsW, GetEnvironmentStringsW,
    };

    let block = unsafe { GetEnvironmentStringsW() };
    if block.is_null() {
        return false;
    }
    let mut present = false;
    let mut entry = block;
    unsafe {
        while *entry != 0 {
            if *entry == b'=' as u16 {
                present = true;
                break;
            }
            while *entry != 0 {
                entry = entry.add(1);
            }
            entry = entry.add(1);
        }
        FreeEnvironmentStringsW(block);
    }
    present
}

/// Publish `=X:` when the process environment has none, so a later
/// `_wspawnv` / `_wexecv` walk has a first entry.
#[cfg(windows)]
pub fn ensure_drive_current_directory() {
    if !environment_has_drive_current_directory() {
        let _ = publish_drive_current_directory();
    }
}

pub fn set_current_dir(path: impl AsRef<std::path::Path>) -> io::Result<()> {
    env::set_current_dir(&path)?;
    #[cfg(windows)]
    publish_drive_current_directory()?;
    Ok(())
}

#[must_use]
pub fn process_id() -> u32 {
    std::process::id()
}

#[cfg(any(not(target_arch = "wasm32"), target_os = "wasi"))]
pub fn cpu_count() -> usize {
    num_cpus::get()
}

#[cfg(not(any(not(target_arch = "wasm32"), target_os = "wasi")))]
pub fn cpu_count() -> usize {
    1
}

#[cfg(unix)]
pub fn page_size() -> usize {
    rustix::param::page_size()
}

#[cfg(target_arch = "wasm32")]
pub const fn page_size() -> usize {
    // WebAssembly's page size is a constant defined by the spec.
    1024 * 64
}

#[cfg(windows)]
pub fn page_size() -> usize {
    let mut info = SYSTEM_INFO::default();
    unsafe {
        GetSystemInfo(&mut info);
    }
    info.dwPageSize as _
}

#[cfg(unix)]
pub fn alloc_granularity() -> usize {
    // On Unix-likes, the page size is the smallest allocation unit rather than a separate concept
    // of allocation granularity.
    page_size()
}

#[cfg(target_arch = "wasm32")]
pub const fn alloc_granularity() -> usize {
    // Like Unix, WebAssembly doesn't separate page size and alloc granularity.
    page_size()
}

#[cfg(windows)]
pub fn alloc_granularity() -> usize {
    let mut info = SYSTEM_INFO::default();
    unsafe {
        GetSystemInfo(&mut info);
    }
    info.dwAllocationGranularity as _
}

pub fn device_encoding(_fd: i32) -> Option<String> {
    #[cfg(any(
        target_os = "android",
        target_os = "redox",
        all(target_arch = "wasm32", not(target_os = "wasi"))
    ))]
    {
        Some("UTF-8".to_owned())
    }

    #[cfg(windows)]
    {
        use windows_sys::Win32::System::Console;
        let cp = match _fd {
            0 => unsafe { Console::GetConsoleCP() },
            1 | 2 => unsafe { Console::GetConsoleOutputCP() },
            _ => 0,
        };

        Some(format!("cp{cp}"))
    }

    #[cfg(not(any(
        target_os = "android",
        target_os = "redox",
        windows,
        all(target_arch = "wasm32", not(target_os = "wasi"))
    )))]
    {
        let encoding = unsafe {
            let encoding = libc::nl_langinfo(libc::CODESET);
            if encoding.is_null() || encoding.read() == b'\0' as libc::c_char {
                "UTF-8".to_owned()
            } else {
                core::ffi::CStr::from_ptr(encoding)
                    .to_string_lossy()
                    .into_owned()
            }
        };

        Some(encoding)
    }
}

pub fn exit(code: i32) -> ! {
    std::process::exit(code)
}

/// Wrapper around the C `abort()` call: terminates the process abnormally.
pub fn abort() -> ! {
    unsafe extern "C" {
        fn abort() -> !;
    }
    unsafe { abort() }
}

/// Read `size` cryptographically random bytes from the OS.
pub fn urandom(size: usize) -> io::Result<Vec<u8>> {
    let mut buf = vec![0u8; size];
    getrandom::fill(&mut buf).map_err(io::Error::from)?;
    Ok(buf)
}

#[cfg(any(unix, windows, target_os = "wasi"))]
pub fn isatty(fd: i32) -> bool {
    unsafe { suppress_iph!(libc::isatty(fd)) != 0 }
}

#[cfg(not(any(unix, windows, target_os = "wasi")))]
pub fn isatty(_fd: i32) -> bool {
    false
}

#[cfg(any(unix, windows))]
pub fn system(command: &CStr) -> libc::c_int {
    unsafe { libc::system(command.as_ptr()) }
}

#[cfg(target_os = "linux")]
pub fn copy_file_range(
    src: crt_fd::Borrowed<'_>,
    offset_src: Option<&mut u64>,
    dst: crt_fd::Borrowed<'_>,
    offset_dst: Option<&mut u64>,
    count: usize,
) -> rustix::io::Result<usize> {
    // `copy_file_range` isn't wrapped in every libc (i.e. musl).
    // However, Rustix is a safe wrapper around the syscall that bypasses libc.
    rustix::fs::copy_file_range(src, offset_src, dst, offset_dst, count)
}

#[cfg(windows)]
pub fn seek_fd(
    fd: crt_fd::Borrowed<'_>,
    position: crt_fd::Offset,
    how: i32,
) -> io::Result<crt_fd::Offset> {
    use crate::windows::CheckWin32Bool;

    let handle = crt_fd::as_handle(fd)?;
    // `SetFilePointer` returns the low half of the new position and reports
    // failure with the value a position four gigabytes in also has, so the two
    // are only told apart through the error code. The `Ex` form answers with
    // the whole position and a success flag of its own.
    let mut new_position = 0;
    unsafe {
        SetFilePointerEx(
            handle.as_raw_handle(),
            position,
            &mut new_position,
            how as _,
        )
    }
    .check_win32_bool()?;
    Ok(new_position)
}

#[cfg(any(unix, target_os = "wasi"))]
pub fn seek_fd(
    fd: crt_fd::Borrowed<'_>,
    position: crt_fd::Offset,
    how: i32,
) -> io::Result<crt_fd::Offset> {
    unsafe { suppress_iph!(libc::lseek(fd.as_raw(), position, how)) }.check_libc_neg()
}

#[cfg(windows)]
fn filetime_from_duration(duration: Duration) -> FILETIME {
    let intervals = ((duration.as_secs() as i64 + 11644473600) * 10_000_000)
        + (duration.subsec_nanos() as i64 / 100);
    FILETIME {
        dwLowDateTime: intervals as u32,
        dwHighDateTime: (intervals >> 32) as u32,
    }
}

#[cfg(windows)]
pub fn set_file_times(
    path: impl AsRef<Path>,
    access: Duration,
    modified: Duration,
) -> io::Result<()> {
    use crate::windows::CheckWin32Bool;
    let access = filetime_from_duration(access);
    let modified = filetime_from_duration(modified);
    let file = fs::open_write_with_custom_flags(path, FILE_FLAG_BACKUP_SEMANTICS)?;
    unsafe {
        SetFileTime(
            file.as_raw_handle() as _,
            core::ptr::null(),
            &access,
            &modified,
        )
    }
    .check_win32_bool()
}

pub trait ErrorExt {
    fn posix_errno(&self) -> i32;
}

impl ErrorExt for io::Error {
    #[cfg(not(windows))]
    fn posix_errno(&self) -> i32 {
        self.raw_os_error().unwrap_or(0)
    }
    #[cfg(windows)]
    fn posix_errno(&self) -> i32 {
        // A C runtime error carries its exact errno as the payload; report it
        // directly instead of round-tripping through a Win32 error code.
        if let Some(crt) = self.get_ref().and_then(|e| e.downcast_ref::<CrtErrno>()) {
            return crt.0;
        }
        let winerror = self.raw_os_error().unwrap_or(0);
        winerror_to_errno(winerror)
    }
}

/// Wraps a raw C runtime `errno` inside an [`io::Error`].
///
/// CRT functions (`open`, `read`, `dup`, ...) report failures through `errno`,
/// not `GetLastError`. Translating that `errno` into a Win32 error code is
/// lossy — any value missing from [`errno_to_winerror`] collapses to `EINVAL` —
/// and also attaches a spurious `winerror` to the resulting `OSError`. Carrying
/// the `errno` as the error payload lets [`ErrorExt::posix_errno`] recover it
/// exactly while leaving `raw_os_error()` empty, so no `winerror` is reported.
#[cfg(windows)]
#[derive(Debug)]
struct CrtErrno(i32);

#[cfg(windows)]
impl core::fmt::Display for CrtErrno {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match crate::errno::strerror_string(self.0) {
            Some(msg) => f.write_str(&msg),
            None => write!(f, "os error {}", self.0),
        }
    }
}

#[cfg(windows)]
impl core::error::Error for CrtErrno {}

/// Build an [`io::Error`] that preserves a raw C runtime `errno`.
///
/// The [`io::ErrorKind`] is derived from the closest Win32 mapping so callers
/// matching on `kind()` keep working, while the exact `errno` is preserved for
/// [`ErrorExt::posix_errno`].
#[cfg(windows)]
#[must_use]
pub fn io_error_from_errno(errno: i32) -> io::Error {
    let kind = io::Error::from_raw_os_error(errno_to_winerror(errno)).kind();
    io::Error::new(kind, CrtErrno(errno))
}

#[cfg(all(not(windows), not(target_arch = "wasm32")))]
impl ErrorExt for rustix::io::Errno {
    fn posix_errno(&self) -> i32 {
        self.raw_os_error()
    }
}

/// Get the last error from C runtime library functions (like _dup, _dup2, _fstat, etc.)
/// CRT functions set errno, not GetLastError(), so we need to read errno directly.
#[cfg(windows)]
#[must_use]
pub fn errno_io_error() -> io::Error {
    io_error_from_errno(get_errno())
}

#[cfg(not(windows))]
#[must_use]
pub fn errno_io_error() -> io::Error {
    std::io::Error::last_os_error()
}

/// Convert a libc-style return value into an `io::Result`.
///
/// Negative values are treated as errors; errno is read via [`errno_io_error`].
/// Modeled after PyPy's `rposix.handle_posix_error`.
pub trait CheckLibcResult: Sized {
    /// Returns `Ok(self)` if non-negative, otherwise `Err` with the current errno.
    fn check_libc_neg(self) -> io::Result<Self>;
}

macro_rules! impl_check_libc_result {
    ($($ty:ty),* $(,)?) => {
        $(
            impl CheckLibcResult for $ty {
                #[inline]
                fn check_libc_neg(self) -> io::Result<Self> {
                    if self < 0 { Err(errno_io_error()) } else { Ok(self) }
                }
            }
        )*
    };
}

impl_check_libc_result!(i16, i32, i64, isize);

/// libc convention where `0` means success and any non-zero value indicates failure
/// (with errno set). Used by APIs like `sigemptyset`, `sigaction`, `pthread_*`, etc.
pub trait CheckLibcZero {
    /// Returns `Ok(())` if `self == 0`, otherwise the current errno as an `io::Error`.
    fn check_libc_zero(self) -> io::Result<()>;
}

macro_rules! impl_check_libc_zero {
    ($($ty:ty),* $(,)?) => {
        $(
            impl CheckLibcZero for $ty {
                #[inline]
                fn check_libc_zero(self) -> io::Result<()> {
                    if self == 0 { Ok(()) } else { Err(errno_io_error()) }
                }
            }
        )*
    };
}

impl_check_libc_zero!(i32, i64, isize);

#[cfg(windows)]
pub fn get_errno() -> i32 {
    unsafe extern "C" {
        fn _get_errno(pValue: *mut i32) -> i32;
    }
    let mut errno = 0;
    unsafe { suppress_iph!(_get_errno(&mut errno)) };
    errno
}

#[cfg(not(windows))]
#[must_use]
pub fn get_errno() -> i32 {
    std::io::Error::last_os_error().posix_errno()
}

pub fn clear_errno() {
    set_errno(0);
}

/// Set errno to the specified value.
#[cfg(windows)]
pub fn set_errno(value: i32) {
    unsafe extern "C" {
        fn _set_errno(value: i32) -> i32;
    }
    unsafe { suppress_iph!(_set_errno(value)) };
}

#[cfg(unix)]
pub fn set_errno(value: i32) {
    nix::errno::Errno::from_raw(value).set();
}

#[cfg(target_os = "wasi")]
pub fn set_errno(value: i32) {
    unsafe {
        *libc::__errno_location() = value;
    }
}

#[cfg(not(any(unix, windows, target_os = "wasi")))]
pub fn set_errno(_value: i32) {}

// WASIp1, like Unix, provides byte-preserving OsStr conversions.
#[cfg(any(unix, all(target_os = "wasi", not(target_env = "p2"))))]
pub fn bytes_as_os_str(b: &[u8]) -> Result<&std::ffi::OsStr, Utf8Error> {
    use self::ffi::OsStrExt;
    Ok(std::ffi::OsStr::from_bytes(b))
}

#[cfg(not(any(unix, all(target_os = "wasi", not(target_env = "p2")))))]
pub fn bytes_as_os_str(b: &[u8]) -> Result<&std::ffi::OsStr, Utf8Error> {
    Ok(core::str::from_utf8(b)?.as_ref())
}

#[cfg(unix)]
pub use std::os::unix::ffi;

// WASIp1 uses stable std::os::wasi::ffi
#[cfg(all(target_os = "wasi", not(target_env = "p2")))]
pub use std::os::wasi::ffi;

// WASIp2: std::os::wasip2::ffi is unstable, so we provide a stable implementation
// leveraging WASI's UTF-8 string guarantee
#[cfg(all(target_os = "wasi", target_env = "p2"))]
pub mod ffi {
    use std::ffi::{OsStr, OsString};

    pub trait OsStrExt: sealed::Sealed {
        fn as_bytes(&self) -> &[u8];
        fn from_bytes(slice: &[u8]) -> &Self;
    }

    impl OsStrExt for OsStr {
        fn as_bytes(&self) -> &[u8] {
            // WASI strings are guaranteed to be UTF-8
            self.to_str().expect("wasip2 strings are UTF-8").as_bytes()
        }

        fn from_bytes(slice: &[u8]) -> &OsStr {
            // WASI strings are guaranteed to be UTF-8
            OsStr::new(core::str::from_utf8(slice).expect("wasip2 strings are UTF-8"))
        }
    }

    pub trait OsStringExt: sealed::Sealed {
        fn from_vec(vec: Vec<u8>) -> Self;
        fn into_vec(self) -> Vec<u8>;
    }

    impl OsStringExt for OsString {
        fn from_vec(vec: Vec<u8>) -> OsString {
            // WASI strings are guaranteed to be UTF-8
            OsString::from(String::from_utf8(vec).expect("wasip2 strings are UTF-8"))
        }

        fn into_vec(self) -> Vec<u8> {
            // WASI strings are guaranteed to be UTF-8
            self.to_str()
                .expect("wasip2 strings are UTF-8")
                .as_bytes()
                .to_vec()
        }
    }

    mod sealed {
        pub trait Sealed {}
        impl Sealed for std::ffi::OsStr {}
        impl Sealed for std::ffi::OsString {}
    }
}

#[cfg(windows)]
#[must_use]
pub fn errno_to_winerror(errno: i32) -> i32 {
    use libc::*;
    use windows_sys::Win32::Foundation::*;
    let winerror = match errno {
        ENOENT => ERROR_FILE_NOT_FOUND,
        E2BIG => ERROR_BAD_ENVIRONMENT,
        ENOEXEC => ERROR_BAD_FORMAT,
        EBADF => ERROR_INVALID_HANDLE,
        ECHILD => ERROR_WAIT_NO_CHILDREN,
        EAGAIN => ERROR_NO_PROC_SLOTS,
        ENOMEM => ERROR_NOT_ENOUGH_MEMORY,
        EACCES => ERROR_ACCESS_DENIED,
        EEXIST => ERROR_FILE_EXISTS,
        EXDEV => ERROR_NOT_SAME_DEVICE,
        ENOTDIR => ERROR_DIRECTORY,
        EMFILE => ERROR_TOO_MANY_OPEN_FILES,
        ENOSPC => ERROR_DISK_FULL,
        EPIPE => ERROR_BROKEN_PIPE,
        ENOTEMPTY => ERROR_DIR_NOT_EMPTY,
        EILSEQ => ERROR_NO_UNICODE_TRANSLATION,
        EINVAL => ERROR_INVALID_FUNCTION,
        _ => ERROR_INVALID_FUNCTION,
    };
    winerror as _
}

// winerror: https://learn.microsoft.com/windows/win32/debug/system-error-codes--0-499-
// errno: https://learn.microsoft.com/cpp/c-runtime-library/errno-constants?view=msvc-170
#[cfg(windows)]
#[must_use]
pub fn winerror_to_errno(winerror: i32) -> i32 {
    use libc::*;
    use windows_sys::Win32::{
        Foundation::*,
        Networking::WinSock::{
            WSAEACCES, WSAEBADF, WSAECONNABORTED, WSAECONNREFUSED, WSAECONNRESET, WSAEFAULT,
            WSAEINTR, WSAEINVAL, WSAEMFILE,
        },
    };
    // Unwrap FACILITY_WIN32 HRESULT errors.
    // if ((winerror & 0xFFFF0000) == 0x80070000) {
    //     winerror &= 0x0000FFFF;
    // }

    // Winsock error codes (10000-11999) are errno values.
    if (10000..12000).contains(&winerror) {
        match winerror {
            WSAEINTR | WSAEBADF | WSAEACCES | WSAEFAULT | WSAEINVAL | WSAEMFILE => {
                // Winsock definitions of errno values. See WinSock2.h
                return winerror - 10000;
            }
            _ => return winerror as _,
        }
    }

    #[allow(non_upper_case_globals)]
    match winerror as u32 {
        ERROR_FILE_NOT_FOUND
        | ERROR_PATH_NOT_FOUND
        | ERROR_INVALID_DRIVE
        | ERROR_NO_MORE_FILES
        | ERROR_BAD_NETPATH
        | ERROR_BAD_NET_NAME
        | ERROR_BAD_PATHNAME
        | ERROR_FILENAME_EXCED_RANGE => ENOENT,
        ERROR_BAD_ENVIRONMENT => E2BIG,
        ERROR_BAD_FORMAT
        | ERROR_INVALID_STARTING_CODESEG
        | ERROR_INVALID_STACKSEG
        | ERROR_INVALID_MODULETYPE
        | ERROR_INVALID_EXE_SIGNATURE
        | ERROR_EXE_MARKED_INVALID
        | ERROR_BAD_EXE_FORMAT
        | ERROR_ITERATED_DATA_EXCEEDS_64k
        | ERROR_INVALID_MINALLOCSIZE
        | ERROR_DYNLINK_FROM_INVALID_RING
        | ERROR_IOPL_NOT_ENABLED
        | ERROR_INVALID_SEGDPL
        | ERROR_AUTODATASEG_EXCEEDS_64k
        | ERROR_RING2SEG_MUST_BE_MOVABLE
        | ERROR_RELOC_CHAIN_XEEDS_SEGLIM
        | ERROR_INFLOOP_IN_RELOC_CHAIN => ENOEXEC,
        ERROR_INVALID_HANDLE | ERROR_INVALID_TARGET_HANDLE | ERROR_DIRECT_ACCESS_HANDLE => EBADF,
        ERROR_WAIT_NO_CHILDREN | ERROR_CHILD_NOT_COMPLETE => ECHILD,
        ERROR_NO_PROC_SLOTS | ERROR_MAX_THRDS_REACHED | ERROR_NESTING_NOT_ALLOWED => EAGAIN,
        ERROR_ARENA_TRASHED
        | ERROR_NOT_ENOUGH_MEMORY
        | ERROR_INVALID_BLOCK
        | ERROR_NOT_ENOUGH_QUOTA => ENOMEM,
        ERROR_ACCESS_DENIED
        | ERROR_CURRENT_DIRECTORY
        | ERROR_WRITE_PROTECT
        | ERROR_BAD_UNIT
        | ERROR_NOT_READY
        | ERROR_BAD_COMMAND
        | ERROR_CRC
        | ERROR_BAD_LENGTH
        | ERROR_SEEK
        | ERROR_NOT_DOS_DISK
        | ERROR_SECTOR_NOT_FOUND
        | ERROR_OUT_OF_PAPER
        | ERROR_WRITE_FAULT
        | ERROR_READ_FAULT
        | ERROR_GEN_FAILURE
        | ERROR_SHARING_VIOLATION
        | ERROR_LOCK_VIOLATION
        | ERROR_WRONG_DISK
        | ERROR_SHARING_BUFFER_EXCEEDED
        | ERROR_NETWORK_ACCESS_DENIED
        | ERROR_CANNOT_MAKE
        | ERROR_FAIL_I24
        | ERROR_DRIVE_LOCKED
        | ERROR_SEEK_ON_DEVICE
        | ERROR_NOT_LOCKED
        | ERROR_LOCK_FAILED
        | 35 => EACCES,
        ERROR_FILE_EXISTS | ERROR_ALREADY_EXISTS => EEXIST,
        ERROR_NOT_SAME_DEVICE => EXDEV,
        ERROR_DIRECTORY => ENOTDIR,
        ERROR_TOO_MANY_OPEN_FILES => EMFILE,
        ERROR_DISK_FULL => ENOSPC,
        ERROR_BROKEN_PIPE | ERROR_NO_DATA => EPIPE,
        ERROR_DIR_NOT_EMPTY => ENOTEMPTY,
        ERROR_NO_UNICODE_TRANSLATION => EILSEQ,
        // Connection-related Windows error codes - map to Winsock error codes
        // which Python uses on Windows (errno.ECONNREFUSED = 10061, etc.)
        ERROR_CONNECTION_REFUSED => WSAECONNREFUSED,
        ERROR_CONNECTION_ABORTED => WSAECONNABORTED,
        ERROR_NETNAME_DELETED => WSAECONNRESET,
        ERROR_INVALID_FUNCTION
        | ERROR_INVALID_ACCESS
        | ERROR_INVALID_DATA
        | ERROR_INVALID_PARAMETER
        | ERROR_NEGATIVE_SEEK => EINVAL,
        _ => EINVAL,
    }
}

#[cfg(test)]
mod tests {
    #[test]
    fn o_rdonly_is_zero() {
        assert_eq!(super::O_RDONLY, 0);
    }

    #[test]
    fn o_wronly_is_one() {
        assert_eq!(super::O_WRONLY, 1);
    }
}