Re: [PATCH v2 2/3] rust: alloc: add Vec::resize method

[Benno Lossin]

On Tue Mar 18, 2025 at 9:12 PM CET, Tamir Duberstein wrote:
> On Sun, Mar 16, 2025 at 7:17 AM Andrew Ballance
> <andrewjballance@xxxxxxxxx> wrote:
>> +    pub fn resize(&mut self, new_len: usize, value: T, flags: Flags) -> Result<(), AllocError> {
>> +        if new_len > self.len() {
>> +            self.extend_with(new_len - self.len(), value, flags)
>> +        } else {
>> +            self.truncate(new_len);
>> +            Ok(())
>> +        }
>> +    }
>
> You can avoid underflow checking in debug builds by using `checked_sub`:

`checked_sub` doesn't only avoid underflow in debug builds, but rather
in all builds. But the code below is a good suggestion.

---
Cheers,
Benno

>         match new_len.checked_sub(self.len()) {
>             Some(n) => self.extend_with(n, value, flags),
>             None => {
>                 self.truncate(new_len);
>                 Ok(())
>             }
>         }
>
>>  }
>>
>>  impl<T, A> Drop for Vec<T, A>
>> --
>> 2.48.1
>>
>>
>
> Either way:
>
> Reviewed-by: Tamir Duberstein <tamird@xxxxxxxxx>