blob: 5806e0c60767165bdeaaa0073e8005fc65700f43 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
|
//! `HasMemoryCost` and typed memory cost tracking
/// Types whose memory usage is known (and stable)
///
/// ### Important guarantees
///
/// Implementors of this trait must uphold the guarantees in the API of
/// [`memory_cost`](HasMemoryCost::memory_cost).
///
/// If these guarantees are violated, memory tracking may go wrong,
/// with seriously bad implications for the whole program,
/// including possible complete denial of service.
///
/// (Nevertheless, memory safety will not be compromised,
/// so trait this is not `unsafe`.)
pub trait HasMemoryCost {
/// Returns the memory cost of `self`, in bytes
///
/// ### Return value must be stable
///
/// It is vital that the return value does not change, for any particular `self`,
/// unless `self` is mutated through `&mut self` or similar.
/// Otherwise, memory accounting may go awry.
///
/// If `self` has interior mutability. the changing internal state
/// must not change the memory cost.
///
/// ### Panics - forbidden
///
/// This method must not panic.
/// Otherwise, memory accounting may go awry.
fn memory_cost(&self, _: crate::EnabledToken) -> usize;
}
|
