You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: xgetcwd.rs
    path of file: ./repos/rustybox/libbb
    
    the code of the file until where you have to start completion: use crate::libbb::ptr_to_globals::bb_errno;
use crate::librb::size_t;
use libc;
use libc::free;
extern "C" {

  #[no_mangle]
  fn getcwd(__buf: *mut libc::c_char, __size: size_t) -> *mut libc::c_char;
  #[no_mangle]
  fn strlen(__s: *const libc::c_char) -> size_t;

}

/*
 * Busybox main internal header file
 *
 * Based in part on code from sash, Copyrigh
    
pub unsafe fn xrealloc_getcwd_or_warn(mut cwd: *mut libc::c_char) -> *mut libc::c_char {
  let mut ret: *mut libc::c_char = std::ptr::null_mut::<libc::c_char>(); /* 128 + 64 should be enough for 99% of cases */
  let mut path_max: libc::c_uint = 0;
  path_max = 128i32 as libc::c_uint;
  loop {
    path_max = path_max.wrapping_add(64i32 as libc::c_uint);
    cwd = crate::libbb::xfuncs_printf::xrealloc(cwd as *mut libc::c_void, path_max as size_t)
      as *mut libc::c_char;
    ret = getcwd(cwd, path_max as size_t);
    if ret.is_null() {
      if *bb_errno == 34i32 {
        continue;
      }
      free(cwd as *mut libc::c_void);
      crate::libbb::perror_msg::bb_simple_perror_msg(
        b"getcwd\x00" as *const u8 as *const libc::c_char,
      );
      return std::ptr::null_mut::<libc::c_char>();
    } else {
      cwd = crate::libbb::xfuncs_printf::xrealloc(
        cwd as *mut libc::c_void,
        strlen(cwd).wrapping_add(1i32 as libc::c_ulong),
      ) as *mut libc::c_char;
      return cwd;
    }
  }
}