Comments (3)
+1 to this.
@jeromefroe Can you please consider reverting #150 which uses NonZeroUsize
for capacity.
There are certain cases which capacity zero is pretty useful and ergonomic in the code as in for example to disable the cache mentioned above. It is a similar thing to pass an empty vector or buffer around.
Or you may be dynamically allocating capacity to each of many caches and some might get zero.
NonZeroUsize
is also making the api more divergent from standard hash-map type (or other common types). Having to use NonZeroUsize
also forces to either use the unsafe
new_unchecked
function or use unwrap
after new
, and both are ugly.
from lru-rs.
If you wish to support a cache with zero capacity, you will need to return an Option
whenever you call get_or_insert
or get_mut_or_insert
. This means handling the case where the capacity is zero each time instead of just during initialization. Is this justified? I think that in most use cases the desired change will add much more branching (handling Option
s).
Comparing it to a hash-map type may not be suitable because hash-maps typically have dynamic capacity and don't fail on insertions due to capacity limitations, as it increases on demand.
Still, it should be possible to create a wrapper around the cache to handle the zero-capacity case and expose the desired APIs.
WDYT?
from lru-rs.
If you wish to support a cache with zero capacity, you will need to return an
Option
whenever you callget_or_insert
orget_mut_or_insert
Not necessarily.
You can implement:
enum ValueWrapper<'a, V> {
Borrowed(&'a V),
Owned(V),
}
So that get_or_insert
will return ValueWrapper
instead, and the ValueWrapper
can implement Borrow
:
impl<'a, V> Borrow<V> for ValueWrapper<'a, V> {
fn borrow(&self) -> &V {
match self {
Self::Borrowed(v) => v,
Self::Owned(v) => v,
}
}
}
so that effectively it is equivalent to &V
.
I have implemented this idea in #177
from lru-rs.
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from lru-rs.