Basic Box

basicbox.rs

#![no_implicit_prelude]
pub(crate) extern crate alloc; // with heap
pub(crate) extern crate core; // fundamental
pub(crate) extern crate std; // OS

fn main() {
    let _x = MyBox::new(alloc::vec![4]);
}

pub struct MyBox<T> {
    ptr: *mut T,
    phantom : core::marker::PhantomData<T>
}

impl<T> MyBox<T> {
    pub fn new(val: T) -> Self {
        unsafe {
            let ptr = alloc::alloc::alloc(alloc::alloc::Layout::new::<T>()) as *mut T;
            core::ptr::write(ptr, val);
            MyBox {
                ptr,
                phantom : core::marker::PhantomData
            }
        }
    }
    pub fn unbox(self) -> T {
        unsafe {
            let out = self.ptr.read();
            alloc::alloc::dealloc(self.ptr as *mut u8, alloc::alloc::Layout::new::<T>());
            core::mem::forget(self);
            out
        }
    }
}

// {}
impl<T> core::ops::Drop for MyBox<T> {
    fn drop(&mut self) {
        unsafe {
            core::ptr::drop_in_place(self.ptr);
            alloc::alloc::dealloc(self.ptr as *mut u8, alloc::alloc::Layout::new::<T>());
        }
    }
}

impl<T> core::ops::Deref for MyBox<T> {
    type Target = T;
    fn deref(&self) -> &Self::Target {
        unsafe{&*self.ptr}
    }
}
impl<T> core::ops::DerefMut for MyBox<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        unsafe{&mut *self.ptr}
    }
}