heim-process 0.0.11

use std::io;
use std::mem;
use std::ptr;

#[allow(trivial_casts)]
pub fn args_max() -> io::Result<libc::c_int> {
    let mut name: [libc::c_int; 2] = [libc::CTL_KERN, libc::KERN_ARGMAX];
    let mut value: libc::c_int = 0;
    let mut length = mem::size_of::<libc::c_int>();

    let result = unsafe {
        libc::sysctl(
            name.as_mut_ptr(),
            2,
            &mut value as *mut libc::c_int as *mut libc::c_void,
            &mut length,
            ptr::null_mut(),
            0,
        )
    };

    if result == 0 {
        Ok(value)
    } else {
        Err(io::Error::last_os_error())
    }
}

// TODO: https://chromium.googlesource.com/crashpad/crashpad/+/360e441c53ab4191a6fd2472cc57c3343a2f6944/util/posix/process_util_mac.cc#32
#[allow(trivial_casts)]
pub fn proc_args(pid: libc::pid_t) -> io::Result<Vec<u8>> {
    // Command line for `kernel_task` process can't be fetched
    if pid == 0 {
        return Ok(Vec::new());
    }

    let mut args_max = args_max()? as usize;
    let mut name: [libc::c_int; 3] = [libc::CTL_KERN, libc::KERN_PROCARGS2, pid];
    let mut value = Vec::with_capacity(args_max);

    let result = unsafe {
        libc::sysctl(
            name.as_mut_ptr(),
            3,
            value.as_mut_ptr() as *mut libc::c_void,
            &mut args_max,
            ptr::null_mut(),
            0,
        )
    };

    if args_max < mem::size_of::<libc::c_int>() {
        return Err(io::Error::from(io::ErrorKind::InvalidData));
    }

    // `sysctl` changes the `args_max` value to what length were stored
    // and this is very convenient for us.
    unsafe {
        value.set_len(args_max);
    }

    // Since the default `argmax` is a rather big value (~256kb)
    // it would be unreasonable to keep all that unused data later
    // while the successful result is alive
    value.shrink_to_fit();

    if result == 0 {
        Ok(value)
    } else {
        Err(io::Error::last_os_error())
    }
}