relibc/src/header/stdlib/mod.rs

//! stdlib implementation for Redox, following http://pubs.opengroup.org/onlinepubs/7908799/xsh/stdlib.h.html

use core::convert::TryFrom;
use core::{intrinsics, iter, mem, ptr, slice};
use rand::distributions::{Alphanumeric, Distribution, Uniform};
use rand::prng::XorShiftRng;
use rand::rngs::JitterRng;
use rand::{Rng, SeedableRng};

use c_str::CStr;
use fs::File;
use header::errno::*;
use header::fcntl::*;
use header::limits;
use header::string::*;
use header::time::constants::CLOCK_MONOTONIC;
use header::time::timespec;
use header::unistd::{sysconf, _SC_PAGESIZE};
use header::wchar::*;
use header::{ctype, errno, unistd};
use platform;
use platform::types::*;
use platform::{Pal, Sys};

mod lcg48;
mod sort;

pub const EXIT_FAILURE: c_int = 1;
pub const EXIT_SUCCESS: c_int = 0;
pub const RAND_MAX: c_int = 2_147_483_647;

//Maximum number of bytes in a multibyte character for the current locale
pub const MB_CUR_MAX: c_int = 4;
//Maximum number of bytes in a multibyte characters for any locale
pub const MB_LEN_MAX: c_int = 4;

static mut ATEXIT_FUNCS: [Option<extern "C" fn()>; 32] = [None; 32];
static mut RNG: Option<XorShiftRng> = None;

lazy_static! {
    static ref RNG_SAMPLER: Uniform<c_int> = Uniform::new_inclusive(0, RAND_MAX);
}

#[no_mangle]
pub extern "C" fn _Exit(status: c_int) {
    unistd::_exit(status);
}

#[no_mangle]
pub unsafe extern "C" fn a64l(s: *const c_char) -> c_long {
    if s.is_null() {
        return 0;
    }
    let mut l: c_long = 0;
    // a64l does not support more than 6 characters at once
    for x in 0..6 {
        let c = *s.offset(x);
        if c == 0 {
            // string is null terminated
            return l;
        }
        // ASCII to base64 conversion:
        let mut bits: c_long = if c < 58 {
            (c - 46) as c_long // ./0123456789
        } else if c < 91 {
            (c - 53) as c_long // A-Z
        } else {
            (c - 59) as c_long // a-z
        };
        bits <<= 6 * x;
        l |= bits;
    }
    l
}

#[no_mangle]
pub unsafe extern "C" fn abort() {
    intrinsics::abort();
}

#[no_mangle]
pub extern "C" fn abs(i: c_int) -> c_int {
    i.abs()
}

#[no_mangle]
pub unsafe extern "C" fn aligned_alloc(alignment: size_t, size: size_t) -> *mut c_void {
    if size % alignment == 0 {
        /* The size-is-multiple-of-alignment requirement is the only
         * difference between aligned_alloc() and memalign(). */
        memalign(alignment, size)
    } else {
        platform::errno = errno::EINVAL;
        ptr::null_mut()
    }
}

#[no_mangle]
pub unsafe extern "C" fn atexit(func: Option<extern "C" fn()>) -> c_int {
    for i in 0..ATEXIT_FUNCS.len() {
        if ATEXIT_FUNCS[i] == None {
            ATEXIT_FUNCS[i] = func;
            return 0;
        }
    }

    1
}

#[no_mangle]
pub unsafe extern "C" fn atof(s: *const c_char) -> c_double {
    strtod(s, ptr::null_mut())
}

macro_rules! dec_num_from_ascii {
    ($s:expr, $t:ty) => {
        unsafe {
            let mut s = $s;
            // Iterate past whitespace
            while ctype::isspace(*s as c_int) != 0 {
                s = s.offset(1);
            }

            // Find out if there is a - sign
            let neg_sign = match *s {
                0x2d => {
                    s = s.offset(1);
                    true
                }
                // '+' increment s and continue parsing
                0x2b => {
                    s = s.offset(1);
                    false
                }
                _ => false,
            };

            let mut n: $t = 0;
            while ctype::isdigit(*s as c_int) != 0 {
                n = 10 * n - (*s as $t - 0x30);
                s = s.offset(1);
            }

            if neg_sign {
                n
            } else {
                -n
            }
        }
    };
}

#[no_mangle]
pub extern "C" fn atoi(s: *const c_char) -> c_int {
    dec_num_from_ascii!(s, c_int)
}

#[no_mangle]
pub extern "C" fn atol(s: *const c_char) -> c_long {
    dec_num_from_ascii!(s, c_long)
}

#[no_mangle]
pub extern "C" fn atoll(s: *const c_char) -> c_longlong {
    dec_num_from_ascii!(s, c_longlong)
}

unsafe extern "C" fn void_cmp(a: *const c_void, b: *const c_void) -> c_int {
    *(a as *const i32) - *(b as *const i32) as c_int
}

#[no_mangle]
pub unsafe extern "C" fn bsearch(
    key: *const c_void,
    base: *const c_void,
    nel: size_t,
    width: size_t,
    compar: Option<unsafe extern "C" fn(*const c_void, *const c_void) -> c_int>,
) -> *mut c_void {
    let mut start = base;
    let mut len = nel;
    let cmp_fn = compar.unwrap_or(void_cmp);
    while len > 0 {
        let med = (start as size_t + (len >> 1) * width) as *const c_void;
        let diff = cmp_fn(key, med);
        if diff == 0 {
            return med as *mut c_void;
        } else if diff > 0 {
            start = (med as usize + width) as *const c_void;
            len -= 1;
        }
        len >>= 1;
    }
    ptr::null_mut()
}

#[no_mangle]
pub unsafe extern "C" fn calloc(nelem: size_t, elsize: size_t) -> *mut c_void {
    //Handle possible integer overflow in size calculation
    let size_result = nelem.checked_mul(elsize);
    match size_result {
        Some(size) => {
            /* If allocation fails here, errno setting will be handled
             * by malloc() */
            let ptr = malloc(size);
            if !ptr.is_null() {
                intrinsics::write_bytes(ptr as *mut u8, 0, size);
            }
            ptr
        }
        None => {
            // For overflowing multiplication, we have to set errno here
            platform::errno = errno::ENOMEM;
            ptr::null_mut()
        }
    }
}

#[repr(C)]
pub struct div_t {
    quot: c_int,
    rem: c_int,
}

#[no_mangle]
pub extern "C" fn div(numer: c_int, denom: c_int) -> div_t {
    div_t {
        quot: numer / denom,
        rem: numer % denom,
    }
}

#[no_mangle]
pub unsafe extern "C" fn drand48() -> c_double {
    let new_xi = lcg48::generator_step(lcg48::DEFAULT_XI.as_mut_ptr());
    lcg48::float64_from_x(new_xi)
}

// #[no_mangle]
pub extern "C" fn ecvt(
    value: c_double,
    ndigit: c_int,
    decpt: *mut c_int,
    sign: *mut c_int,
) -> *mut c_char {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn erand48(xsubi: *mut c_ushort) -> c_double {
    let new_xi = lcg48::generator_step(xsubi);
    lcg48::float64_from_x(new_xi)
}

#[no_mangle]
pub unsafe extern "C" fn exit(status: c_int) {
    extern "C" {
        static __fini_array_start: extern "C" fn();
        static __fini_array_end: extern "C" fn();

        fn pthread_terminate();
        fn _fini();
    }

    for i in (0..ATEXIT_FUNCS.len()).rev() {
        if let Some(func) = ATEXIT_FUNCS[i] {
            (func)();
        }
    }

    // Look for the neighbor functions in memory until the end
    let mut f = &__fini_array_end as *const _;
    #[allow(clippy::op_ref)]
    while f > &__fini_array_start {
        f = f.offset(-1);
        (*f)();
    }

    _fini();

    pthread_terminate();

    Sys::exit(status);
}

// #[no_mangle]
pub extern "C" fn fcvt(
    value: c_double,
    ndigit: c_int,
    decpt: *mut c_int,
    sign: *mut c_int,
) -> *mut c_char {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn free(ptr: *mut c_void) {
    platform::free(ptr);
}

// #[no_mangle]
pub extern "C" fn gcvt(value: c_double, ndigit: c_int, buf: *mut c_char) -> *mut c_char {
    unimplemented!();
}

unsafe fn find_env(search: *const c_char) -> Option<(usize, *mut c_char)> {
    for (i, item) in platform::inner_environ.iter().enumerate() {
        let mut item = *item;
        if item.is_null() {
            assert_eq!(
                i,
                platform::inner_environ.len() - 1,
                "an early null pointer in environ vector"
            );
            break;
        }
        let mut search = search;
        loop {
            let end_of_query = *search == 0 || *search == b'=' as c_char;
            assert_ne!(*item, 0, "environ has an item without value");
            if *item == b'=' as c_char || end_of_query {
                if *item == b'=' as c_char && end_of_query {
                    // Both keys env here
                    return Some((i, item.offset(1)));
                } else {
                    break;
                }
            }

            if *item != *search {
                break;
            }

            item = item.offset(1);
            search = search.offset(1);
        }
    }
    None
}

#[no_mangle]
pub unsafe extern "C" fn getenv(name: *const c_char) -> *mut c_char {
    find_env(name).map(|val| val.1).unwrap_or(ptr::null_mut())
}

// #[no_mangle]
pub extern "C" fn getsubopt(
    optionp: *mut *mut c_char,
    tokens: *const *mut c_char,
    valuep: *mut *mut c_char,
) -> c_int {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn grantpt(fildes: c_int) -> c_int {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn initstate(seec: c_uint, state: *mut c_char, size: size_t) -> *mut c_char {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn jrand48(xsubi: *mut c_ushort) -> c_long {
    let new_xi = lcg48::generator_step(xsubi);
    lcg48::int32_from_x(new_xi)
}

// #[no_mangle]
pub extern "C" fn l64a(value: c_long) -> *mut c_char {
    unimplemented!();
}

#[no_mangle]
pub extern "C" fn labs(i: c_long) -> c_long {
    i.abs()
}

#[no_mangle]
pub unsafe extern "C" fn lcong48(param: *mut c_ushort) {
    // Input should be a size-7 array.

    /* Go through this ptr -> u64 -> ptr conversion to ensure we only
     * get the lower 16 bits of each element. */
    let new_xi = lcg48::uint48_from_ushort_arr3(param.offset(0));
    lcg48::set_ushort_arr3_from_uint48(lcg48::DEFAULT_XI.as_mut_ptr(), new_xi);
    lcg48::A = lcg48::uint48_from_ushort_arr3(param.offset(3));
    lcg48::C = *param.offset(6) as u16; // c_ushort may be more than 16 bits
}

#[repr(C)]
pub struct ldiv_t {
    quot: c_long,
    rem: c_long,
}

#[no_mangle]
pub extern "C" fn ldiv(numer: c_long, denom: c_long) -> ldiv_t {
    ldiv_t {
        quot: numer / denom,
        rem: numer % denom,
    }
}

#[no_mangle]
pub extern "C" fn llabs(i: c_longlong) -> c_longlong {
    i.abs()
}

#[repr(C)]
pub struct lldiv_t {
    quot: c_longlong,
    rem: c_longlong,
}

#[no_mangle]
pub extern "C" fn lldiv(numer: c_longlong, denom: c_longlong) -> lldiv_t {
    lldiv_t {
        quot: numer / denom,
        rem: numer % denom,
    }
}

#[no_mangle]
pub unsafe extern "C" fn lrand48() -> c_long {
    let new_xi = lcg48::generator_step(lcg48::DEFAULT_XI.as_mut_ptr());
    lcg48::uint31_from_x(new_xi)
}

#[no_mangle]
pub unsafe extern "C" fn malloc(size: size_t) -> *mut c_void {
    let ptr = platform::alloc(size);
    if ptr.is_null() {
        platform::errno = errno::ENOMEM;
    }
    ptr
}

#[no_mangle]
pub unsafe extern "C" fn memalign(alignment: size_t, size: size_t) -> *mut c_void {
    /* Check if alignment is a (positive) power of two. The second
     * expression will never underflow, due to Rust's lazy boolean
     * operators. */
    if alignment > 0 && (alignment & (alignment - 1)) == 0 {
        let ptr = platform::alloc_align(size, alignment);
        if ptr.is_null() {
            platform::errno = errno::ENOMEM;
        }
        ptr
    } else {
        platform::errno = errno::EINVAL;
        ptr::null_mut()
    }
}

#[no_mangle]
pub unsafe extern "C" fn mblen(s: *const c_char, n: size_t) -> c_int {
    let mut wc: wchar_t = 0;
    let mut state: mbstate_t = mbstate_t {};
    let result: usize = mbrtowc(&mut wc, s, n, &mut state);

    if result == -1isize as usize {
        return -1;
    }
    if result == -2isize as usize {
        return -1;
    }

    result as i32
}

#[no_mangle]
pub unsafe extern "C" fn mbstowcs(pwcs: *mut wchar_t, mut s: *const c_char, n: size_t) -> size_t {
    let mut state: mbstate_t = mbstate_t {};
    mbsrtowcs(pwcs, &mut s, n, &mut state)
}

#[no_mangle]
pub unsafe extern "C" fn mbtowc(pwc: *mut wchar_t, s: *const c_char, n: size_t) -> c_int {
    let mut state: mbstate_t = mbstate_t {};
    mbrtowc(pwc, s, n, &mut state) as c_int
}

fn inner_mktemp<T, F>(name: *mut c_char, suffix_len: c_int, mut attempt: F) -> Option<T>
where
    F: FnMut() -> Option<T>,
{
    let len = unsafe { strlen(name) as c_int };

    if len < 6 || suffix_len > len - 6 {
        unsafe { platform::errno = errno::EINVAL };
        return None;
    }

    for i in (len - suffix_len - 6)..(len - suffix_len) {
        if unsafe { *name.offset(i as isize) } != b'X' as c_char {
            unsafe { platform::errno = errno::EINVAL };
            return None;
        }
    }

    let mut rng = JitterRng::new_with_timer(get_nstime);
    let _ = rng.test_timer();

    for _ in 0..100 {
        let char_iter = iter::repeat(())
            .map(|()| rng.sample(Alphanumeric))
            .take(6)
            .enumerate();
        unsafe {
            for (i, c) in char_iter {
                *name.offset((len as isize) - (suffix_len as isize) - (i as isize) - 1) =
                    c as c_char
            }
        }

        if let result @ Some(_) = attempt() {
            return result;
        }
    }

    unsafe { platform::errno = errno::EEXIST }

    None
}

#[no_mangle]
pub unsafe extern "C" fn mktemp(name: *mut c_char) -> *mut c_char {
    if inner_mktemp(name, 0, || {
        let name = CStr::from_ptr(name);
        if Sys::access(name, 0) != 0 && platform::errno == ENOENT {
            Some(())
        } else {
            None
        }
    })
    .is_none()
    {
        *name = 0;
    }
    name
}

fn get_nstime() -> u64 {
    let mut ts: timespec = unsafe { mem::uninitialized() };
    Sys::clock_gettime(CLOCK_MONOTONIC, &mut ts);
    ts.tv_nsec as u64
}

#[no_mangle]
pub extern "C" fn mkostemps(name: *mut c_char, suffix_len: c_int, mut flags: c_int) -> c_int {
    flags &= !O_ACCMODE;
    flags |= O_RDWR | O_CREAT | O_EXCL;

    inner_mktemp(name, suffix_len, || {
        let name = unsafe { CStr::from_ptr(name) };
        let fd = Sys::open(name, flags, 0o600);

        if fd >= 0 {
            Some(fd)
        } else {
            None
        }
    })
    .unwrap_or(-1)
}

#[no_mangle]
pub extern "C" fn mkstemp(name: *mut c_char) -> c_int {
    mkostemps(name, 0, 0)
}
#[no_mangle]
pub extern "C" fn mkostemp(name: *mut c_char, flags: c_int) -> c_int {
    mkostemps(name, 0, flags)
}
#[no_mangle]
pub extern "C" fn mkstemps(name: *mut c_char, suffix_len: c_int) -> c_int {
    mkostemps(name, suffix_len, 0)
}

#[no_mangle]
pub unsafe extern "C" fn mrand48() -> c_long {
    let new_xi = lcg48::generator_step(lcg48::DEFAULT_XI.as_mut_ptr());
    lcg48::int32_from_x(new_xi)
}

#[no_mangle]
pub unsafe extern "C" fn nrand48(xsubi: *mut c_ushort) -> c_long {
    let new_xi = lcg48::generator_step(xsubi);
    lcg48::uint31_from_x(new_xi)
}

// #[no_mangle]
pub extern "C" fn ptsname(fildes: c_int) -> *mut c_char {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn putenv(insert: *mut c_char) -> c_int {
    assert_ne!(insert, ptr::null_mut(), "putenv(NULL)");
    if let Some((i, _)) = find_env(insert) {
        //TODO: find out why this crashes: platform::free(platform::inner_environ[i] as *mut c_void);
        platform::inner_environ[i] = insert;
    } else {
        let i = platform::inner_environ.len() - 1;
        assert_eq!(
            platform::inner_environ[i],
            ptr::null_mut(),
            "environ did not end with null"
        );
        platform::inner_environ[i] = insert;
        platform::inner_environ.push(ptr::null_mut());
        platform::environ = platform::inner_environ.as_mut_ptr();
    }
    0
}

#[no_mangle]
pub extern "C" fn qsort(
    base: *mut c_void,
    nel: size_t,
    width: size_t,
    compar: Option<extern "C" fn(*const c_void, *const c_void) -> c_int>,
) {
    if let Some(comp) = compar {
        // XXX: check width too?  not specified
        if nel > 0 {
            // XXX: maybe try to do mergesort/timsort first and fallback to introsort if memory
            //      allocation fails?  not sure what is ideal
            sort::introsort(base as *mut c_char, nel, width, comp);
        }
    }
}

#[no_mangle]
pub unsafe extern "C" fn rand() -> c_int {
    match RNG {
        Some(ref mut rng) => RNG_SAMPLER.sample(rng),
        None => {
            let mut rng = XorShiftRng::from_seed([1; 16]);
            let ret = RNG_SAMPLER.sample(&mut rng);
            RNG = Some(rng);
            ret
        }
    }
}

#[no_mangle]
pub unsafe extern "C" fn rand_r(seed: *mut c_uint) -> c_int {
    if seed.is_null() {
        errno::EINVAL
    } else {
        // set the type explicitly so this will fail if the array size for XorShiftRng changes
        let seed_arr: [u8; 16] = mem::transmute([*seed; 16 / mem::size_of::<c_uint>()]);

        let mut rng = XorShiftRng::from_seed(seed_arr);
        let ret = RNG_SAMPLER.sample(&mut rng);

        *seed = ret as _;

        ret
    }
}

// #[no_mangle]
pub extern "C" fn random() -> c_long {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn realloc(ptr: *mut c_void, size: size_t) -> *mut c_void {
    let ptr = platform::realloc(ptr, size);
    if ptr.is_null() {
        platform::errno = errno::ENOMEM;
    }
    ptr
}

#[no_mangle]
pub unsafe extern "C" fn realpath(pathname: *const c_char, resolved: *mut c_char) -> *mut c_char {
    let ptr = if resolved.is_null() {
        malloc(limits::PATH_MAX) as *mut c_char
    } else {
        resolved
    };

    let out = slice::from_raw_parts_mut(ptr as *mut u8, limits::PATH_MAX);
    {
        let file = match File::open(&CStr::from_ptr(pathname), O_PATH | O_CLOEXEC) {
            Ok(file) => file,
            Err(_) => return ptr::null_mut(),
        };

        let len = out.len();
        let read = Sys::fpath(*file, &mut out[..len - 1]);
        if read < 0 {
            return ptr::null_mut();
        }
        out[read as usize] = 0;
    }

    ptr
}

#[no_mangle]
pub unsafe extern "C" fn seed48(seed16v: *mut c_ushort) -> *mut c_ushort {
    lcg48::reset_a_and_c();

    lcg48::STASHED_XI = lcg48::DEFAULT_XI;

    let new_xi = lcg48::uint48_from_ushort_arr3(seed16v);
    lcg48::set_ushort_arr3_from_uint48(lcg48::DEFAULT_XI.as_mut_ptr(), new_xi);

    lcg48::STASHED_XI.as_mut_ptr()
}

#[no_mangle]
pub unsafe extern "C" fn setenv(
    mut key: *const c_char,
    mut value: *const c_char,
    overwrite: c_int,
) -> c_int {
    let mut key_len = 0;
    while *key.offset(key_len) != 0 {
        key_len += 1;
    }
    let mut value_len = 0;
    while *value.offset(value_len) != 0 {
        value_len += 1;
    }

    let index = if let Some((i, existing)) = find_env(key) {
        if overwrite == 0 {
            return 0;
        }

        let mut existing_len = 0;
        while *existing.offset(existing_len) != 0 {
            existing_len += 1;
        }

        if existing_len >= value_len {
            // Reuse existing element's allocation
            for i in 0..=value_len {
                *existing.offset(i) = *value.offset(i);
            }
            return 0;
        } else {
            i
        }
    } else {
        let i = platform::inner_environ.len() - 1;
        assert_eq!(
            platform::inner_environ[i],
            ptr::null_mut(),
            "environ did not end with null"
        );
        platform::inner_environ.push(ptr::null_mut());
        platform::environ = platform::inner_environ.as_mut_ptr();
        i
    };

    //platform::free(platform::inner_environ[index] as *mut c_void);
    let mut ptr = platform::alloc(key_len as usize + 1 + value_len as usize) as *mut c_char;
    platform::inner_environ[index] = ptr;

    while *key != 0 {
        *ptr = *key;
        ptr = ptr.offset(1);
        key = key.offset(1);
    }
    *ptr = b'=' as c_char;
    ptr = ptr.offset(1);
    while *value != 0 {
        *ptr = *value;
        ptr = ptr.offset(1);
        value = value.offset(1);
    }
    *ptr = 0;

    0
}

// #[no_mangle]
pub extern "C" fn setkey(key: *const c_char) {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn setstate(state: *const c_char) -> *mut c_char {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn srand(seed: c_uint) {
    RNG = Some(XorShiftRng::from_seed([seed as u8; 16]));
}

#[no_mangle]
pub unsafe extern "C" fn srand48(seedval: c_long) {
    lcg48::reset_a_and_c();

    /* Set the high 32 bits of the 48-bit X_i value to the lower 32 bits
     * of the input argument, and the lower 16 bits to 0x330e, as
     * specified in POSIX. */
    let new_xi = (((seedval as u32) as u64) << 16) | 0x330e_u64;
    lcg48::set_ushort_arr3_from_uint48(lcg48::DEFAULT_XI.as_mut_ptr(), new_xi);
}

// #[no_mangle]
pub extern "C" fn srandom(seed: c_uint) {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn strtod(s: *const c_char, endptr: *mut *mut c_char) -> c_double {
    strto_float_impl!(c_double, s, endptr)
}
#[no_mangle]
pub unsafe extern "C" fn strtof(s: *const c_char, endptr: *mut *mut c_char) -> c_float {
    strto_float_impl!(c_float, s, endptr)
}

pub fn is_positive(ch: c_char) -> Option<(bool, isize)> {
    match ch {
        0 => None,
        ch if ch == b'+' as c_char => Some((true, 1)),
        ch if ch == b'-' as c_char => Some((false, 1)),
        _ => Some((true, 0)),
    }
}

pub unsafe fn detect_base(s: *const c_char) -> Option<(c_int, isize)> {
    let first = *s as u8;
    match first {
        0 => None,
        b'0' => {
            let second = *s.offset(1) as u8;
            if second == b'X' || second == b'x' {
                Some((16, 2))
            } else if second >= b'0' && second <= b'7' {
                Some((8, 1))
            } else {
                // in this case, the prefix (0) is going to be the number
                Some((8, 0))
            }
        }
        _ => Some((10, 0)),
    }
}

pub unsafe fn convert_octal(s: *const c_char) -> Option<(c_ulong, isize, bool)> {
    if *s != 0 && *s == b'0' as c_char {
        if let Some((val, idx, overflow)) = convert_integer(s.offset(1), 8) {
            Some((val, idx + 1, overflow))
        } else {
            // in case the prefix is not actually a prefix
            Some((0, 1, false))
        }
    } else {
        None
    }
}

pub unsafe fn convert_hex(s: *const c_char) -> Option<(c_ulong, isize, bool)> {
    if (*s != 0 && *s == b'0' as c_char)
        && (*s.offset(1) != 0 && (*s.offset(1) == b'x' as c_char || *s.offset(1) == b'X' as c_char))
    {
        convert_integer(s.offset(2), 16).map(|(val, idx, overflow)| (val, idx + 2, overflow))
    } else {
        convert_integer(s, 16).map(|(val, idx, overflow)| (val, idx, overflow))
    }
}

pub unsafe fn convert_integer(s: *const c_char, base: c_int) -> Option<(c_ulong, isize, bool)> {
    // -1 means the character is invalid
    #[rustfmt::skip]
    const LOOKUP_TABLE: [c_long; 256] = [
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
        -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
        25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, -1, -1,
        -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
        25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    ];

    let mut num: c_ulong = 0;
    let mut idx = 0;
    let mut overflowed = false;

    loop {
        // `-1 as usize` is usize::MAX
        // `-1 as u8 as usize` is u8::MAX
        // It extends by the sign bit unless we cast it to unsigned first.
        let val = LOOKUP_TABLE[*s.offset(idx) as u8 as usize];
        if val == -1 || val as c_int >= base {
            break;
        } else {
            if let Some(res) = num
                .checked_mul(base as c_ulong)
                .and_then(|num| num.checked_add(val as c_ulong))
            {
                num = res;
            } else {
                platform::errno = ERANGE;
                num = c_ulong::max_value();
                overflowed = true;
            }

            idx += 1;
        }
    }

    if idx > 0 {
        Some((num, idx, overflowed))
    } else {
        None
    }
}

#[no_mangle]
pub unsafe extern "C" fn strtoul(
    s: *const c_char,
    endptr: *mut *mut c_char,
    base: c_int,
) -> c_ulong {
    strto_impl!(
        c_ulong,
        false,
        c_ulong::max_value(),
        c_ulong::min_value(),
        s,
        endptr,
        base
    )
}

#[no_mangle]
pub unsafe extern "C" fn strtol(s: *const c_char, endptr: *mut *mut c_char, base: c_int) -> c_long {
    strto_impl!(
        c_long,
        true,
        c_long::max_value(),
        c_long::min_value(),
        s,
        endptr,
        base
    )
}

#[no_mangle]
pub unsafe extern "C" fn strtoull(
    s: *const c_char,
    endptr: *mut *mut c_char,
    base: c_int,
) -> c_ulonglong {
    strtoul(s, endptr, base)
}

#[no_mangle]
pub unsafe extern "C" fn strtoll(
    s: *const c_char,
    endptr: *mut *mut c_char,
    base: c_int,
) -> c_longlong {
    strtol(s, endptr, base)
}

#[no_mangle]
pub unsafe extern "C" fn system(command: *const c_char) -> c_int {
    //TODO: share code with popen

    let child_pid = unistd::fork();
    if child_pid == 0 {
        let command_nonnull = if command.is_null() {
            "exit 0\0".as_ptr()
        } else {
            command as *const u8
        };

        let shell = "/bin/sh\0".as_ptr();

        let args = [
            "sh\0".as_ptr(),
            "-c\0".as_ptr(),
            command_nonnull,
            ptr::null(),
        ];

        unistd::execv(shell as *const c_char, args.as_ptr() as *const *mut c_char);

        exit(127);

        unreachable!();
    } else if child_pid > 0 {
        let mut wstatus = 0;
        if Sys::waitpid(child_pid, &mut wstatus, 0) == !0 {
            return -1;
        }

        wstatus
    } else {
        -1
    }
}

// #[no_mangle]
pub extern "C" fn ttyslot() -> c_int {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn unlockpt(fildes: c_int) -> c_int {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn unsetenv(key: *const c_char) -> c_int {
    if let Some((i, _)) = find_env(key) {
        // No need to worry about updating the pointer, this does not
        // reallocate in any way. And the final null is already shifted back.
        platform::inner_environ.remove(i);
    }
    0
}

#[no_mangle]
pub unsafe extern "C" fn valloc(size: size_t) -> *mut c_void {
    /* sysconf(_SC_PAGESIZE) is a c_long and may in principle not
     * convert correctly to a size_t. */
    match size_t::try_from(sysconf(_SC_PAGESIZE)) {
        Ok(page_size) => {
            /* valloc() is not supposed to be able to set errno to
             * EINVAL, hence no call to memalign(). */
            let ptr = platform::alloc_align(size, page_size);
            if ptr.is_null() {
                platform::errno = errno::ENOMEM;
            }
            ptr
        }
        Err(_) => {
            // A corner case. No errno setting.
            ptr::null_mut()
        }
    }
}

#[no_mangle]
pub extern "C" fn wcstombs(s: *mut c_char, pwcs: *mut *const wchar_t, n: size_t) -> size_t {
    let mut state: mbstate_t = mbstate_t {};
    wcsrtombs(s, pwcs, n, &mut state)
}

#[no_mangle]
pub unsafe extern "C" fn wctomb(s: *mut c_char, wc: wchar_t) -> c_int {
    let mut state: mbstate_t = mbstate_t {};
    let result: usize = wcrtomb(s, wc, &mut state);

    if result == -1isize as usize {
        return -1;
    }
    if result == -2isize as usize {
        return -1;
    }

    result as c_int
}