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: array_buffer.rs
    path of file: ./repos/rusty_v8/src
    
    the code of the file until where you have to start completion: // Copyright 2019-2021 the Deno authors. All rights reserved. MIT license.

use std::cell::Cell;
use std::ffi::c_void;
use std::ops::Deref;
use std::ptr::null;
use std::ptr::NonNull;
use std::slice;

use crate::support::long;
use crate::support::MaybeBool;
use crate::support::Opaque;
use crate::support::Shared;
use crate::support::SharedPtrBase;
use crate::support::SharedRef;
use crate::support::UniquePtr;
use crate::su
    
fn test_rust_allocator() {
  use std::sync::atomic::{AtomicUsize, Ordering};
  use std::sync::Arc;

  unsafe extern "C" fn allocate(_: &AtomicUsize, _: usize) -> *mut c_void {
    unimplemented!()
  }
  unsafe extern "C" fn allocate_uninitialized(
    _: &AtomicUsize,
    _: usize,
  ) -> *mut c_void {
    unimplemented!()
  }
  unsafe extern "C" fn free(_: &AtomicUsize, _: *mut c_void, _: usize) {
    unimplemented!()
  }
  unsafe extern "C" fn reallocate(
    _: &AtomicUsize,
    _: *mut c_void,
    _: usize,
    _: usize,
  ) -> *mut c_void {
    unimplemented!()
  }
  unsafe extern "C" fn drop(x: *const AtomicUsize) {
    let arc = Arc::from_raw(x);
    arc.store(42, Ordering::SeqCst);
  }

  let retval = Arc::new(AtomicUsize::new(0));

  let vtable: &'static RustAllocatorVtable<AtomicUsize> =
    &RustAllocatorVtable {
      allocate,
      allocate_uninitialized,
      free,
      reallocate,
      drop,
    };
  unsafe { new_rust_allocator(Arc::into_raw(retval.clone()), vtable) };
  assert_eq!(retval.load(Ordering::SeqCst), 42);
  assert_eq!(Arc::strong_count(&retval), 1);
}