use shmem_bind::{ShmemBox, self as shmem};

let shared_mem = shmem::Builder::new("<FLINK_FILE_HANDLE>")
    .with_size(mem::size_of::<MyType>() as i64)
    .open()?;

let boxed_val = unsafe { shared_mem.boxed::<MyType>() };

type NotZeroI32 = i32;

let boxed_val = unsafe { 
  // the allocated shared_memory is zeroed and thus, not a valid `NotZeroI32`
  let mut boxed_val = shared_mem.boxed::<NotZeroI32>();
  *boxed_val = 5;
  boxed_val
  };

struct MyType;

impl Drop for MyType{
    fn drop(&mut self) {
        println!("my type is dropped");
    }
}

{
  let shared_mem = shmem::Builder::new("<FLINK_FILE_HANDLE>")
      .with_size(mem::size_of::<Message>() as i64)
      .open()?;
  let mut boxed_val = unsafe {shared_mem.boxed::<MyType>()};

  // boxed_val goes out of scope and the underlying MyType is dropped
  // output:
  // my type is dropped
}
{
  let shared_mem = shmem::Builder::new("<FLINK_FILE_HANDLE>")
      .with_size(mem::size_of::<Message>() as i64)
      .open()?;
  let mut boxed_val = unsafe {shared_mem.boxed::<MyType>()};
  ShmemBox::leak(boxed_val);

  // boxed_val leaks and the underlying MyType is not dropped. the shared memory stays linked to the os
  // output is empty
}

struct MyType;

impl Drop for MyType{
    fn drop(&mut self) {
        println!("my type is dropped");
    }
}

{
  let shared_mem = shmem::Builder::new("<FLINK_FILE_HANDLE>")
      .with_size(mem::size_of::<Message>() as i64)
      .open()?;
  let mut boxed_val = unsafe {shared_mem.boxed::<MyType>()};
  
  // boxed_val was owner, but it got leaked
  ShmemBox::leak(boxed_val);
}
{
  let shared_mem = shmem::Builder::new("<FLINK_FILE_HANDLE>")
      .with_size(mem::size_of::<Message>() as i64)
      .open()?;
  let mut boxed_val = unsafe {shared_mem.boxed::<MyType>()};
  
  // shared memory is already created, so the boxed_val is not the owner.
  let boxed_val = ShmemBox::own(boxed_val);

  // boxed_val goes out of scope, MyType is dropped. the shared memory is unliked.
  // output:
  // my type is dropped
}