Re: [PATCH 3/9] rust: list: add struct with prev/next pointers

[Benno Lossin <benno.lossin@proton.me>]

On 04.04.24 16:03, Alice Ryhl wrote:
> On Wed, Apr 3, 2024 at 5:57 PM Benno Lossin <benno.lossin@proton.me> wrote:
>>
>> On 02.04.24 14:17, Alice Ryhl wrote:
>>> +/// Implemented by types where a [`ListArc<Self>`] can be inserted into a `List`.
>>> +///
>>> +/// # Safety
>>> +///
>>> +/// Implementers must ensure that they provide the guarantees documented on the three methods
>>> +/// below.
>>> +///
>>> +/// [`ListArc<Self>`]: ListArc
>>> +pub unsafe trait ListItem<const ID: u64 = 0>: ListArcSafe<ID> {
>>> +    /// Views the [`ListLinks`] for this value.
>>> +    ///
>>> +    /// # Guarantees
>>> +    ///
>>> +    /// * If there is a currently active call to `prepare_to_insert`, then this returns the same
>>> +    ///   pointer as the one returned by the currently active call to `prepare_to_insert`.
>>
>> I was a bit confused by the term "active call to `prepare_to_insert`",
>> since I thought that the function would need to be executed at this
>> moment. I inferred from below that you mean by this that there has been
>> a `prepare_to_insert` call, but not yet a corresponding `post_remove`
>> call.
>> I did not yet find a better way to phrase this.
>>
>> I like putting the guarantees on the functions very much.
> 
> How about this?
> 
> If there is a previous call to `prepare_to_insert` and there is no
> call to `post_remove` since the most recent such call, then this
> returns the same pointer as the one returned by the most recent call
> to `prepare_to_insert`.
> 
> Otherwise, the returned pointer points at a read-only [`ListLinks`]
> with two null pointers.
Sounds good.

-- 
Cheers,
Benno