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: findfs.rs
    path of file: ./repos/rustybox/util_linux
    
    the code of the file until where you have to start completion: use libc;
use libc::puts;
extern "C" {

  /* Returns:
   * 0: no UUID= or LABEL= prefix found
   * 1: UUID= or LABEL= prefix found. In this case,
   *    *fsname is replaced if device with such UUID or LABEL is found
   */

}

/*
 * Support functions for mounting devices by label/uuid
 *
 * Copyright (C) 2006 by Jason Schoon <floydpink@gmail.com>
 * Some portions cribbed from e2fsprogs, util-linux, dosfstools
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source 
    
pub unsafe fn findfs_main(mut _argc: libc::c_int, mut argv: *mut *mut libc::c_char) -> libc::c_int {
  argv = argv.offset(1);
  let mut dev: *mut libc::c_char = *argv;
  if dev.is_null() {
    crate::libbb::appletlib::bb_show_usage();
  }
  if !crate::libbb::compare_string_array::is_prefixed_with(
    dev,
    b"/dev/\x00" as *const u8 as *const libc::c_char,
  )
  .is_null()
  {
    /* Just pass any /dev/xxx name right through.
     * This might aid in some scripts being able
     * to call this unconditionally */
    dev = std::ptr::null_mut::<libc::c_char>()
  } else if crate::util_linux::volume_id::get_devname::resolve_mount_spec(argv) == 0 {
    crate::libbb::appletlib::bb_show_usage();
  }
  if *argv != dev {
    puts(*argv);
    return 0;
  }
  return 1i32;
}