Trait MapStorage 

pub trait MapStorage: Default {
    // Required methods
    fn get(&self, key: &usize) -> Option<&Entry>;
    fn get_mut(&mut self, key: &usize) -> Option<&mut Entry>;
    fn insert(&mut self, key: usize, entry: Entry) -> Option<Entry>;
    fn remove(&mut self, key: &usize) -> Option<Entry>;
    fn contains_key(&self, key: &usize) -> bool;
    fn for_each_entry<F: FnMut(&Entry)>(&self, f: F);
    fn clear(&mut self);

    // Provided methods
    fn reserve(&mut self, _additional: usize) { ... }
    fn decrement_and_maybe_remove(
        &mut self,
        key: &usize,
    ) -> Option<(bool, usize)> { ... }
}

Trait abstracting over map implementations for arena storage.

This allows Arena to be generic over the underlying map type, supporting both BTreeMap and HashMap.

Required Methods

fn get(&self, key: &usize) -> Option<&Entry>

Get an entry by key.

fn get_mut(&mut self, key: &usize) -> Option<&mut Entry>

Get a mutable entry by key.

fn insert(&mut self, key: usize, entry: Entry) -> Option<Entry>

Insert an entry, returning the old value if present.

fn remove(&mut self, key: &usize) -> Option<Entry>

Remove an entry by key.

fn contains_key(&self, key: &usize) -> bool

Check if a key exists.

fn for_each_entry<F: FnMut(&Entry)>(&self, f: F)

Iterate over all entries.

fn clear(&mut self)

Clear all entries.

Provided Methods

fn reserve(&mut self, _additional: usize)

Reserve capacity for additional entries.

This is a no-op for ordered maps (BTreeMap) but can improve performance for hash maps by avoiding rehashing during bulk inserts.

fn decrement_and_maybe_remove(&mut self, key: &usize) -> Option<(bool, usize)>

Decrement the count for a key and remove if zero.

Returns Some(true) if entry was found and removed, Some(false) if entry was found but count > 0 after decrement, None if entry was not found.

This uses entry API when available for single-lookup performance.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl MapStorage for BTreeMap<usize, Entry>

fn get(&self, key: &usize) -> Option<&Entry>

fn get_mut(&mut self, key: &usize) -> Option<&mut Entry>

fn insert(&mut self, key: usize, entry: Entry) -> Option<Entry>

fn remove(&mut self, key: &usize) -> Option<Entry>

fn contains_key(&self, key: &usize) -> bool

fn for_each_entry<F: FnMut(&Entry)>(&self, f: F)

fn clear(&mut self)

impl MapStorage for HashMap<usize, Entry>

fn decrement_and_maybe_remove(&mut self, key: &usize) -> Option<(bool, usize)>

Entry-based decrement for single-lookup performance.

fn get(&self, key: &usize) -> Option<&Entry>

fn get_mut(&mut self, key: &usize) -> Option<&mut Entry>

fn insert(&mut self, key: usize, entry: Entry) -> Option<Entry>

fn remove(&mut self, key: &usize) -> Option<Entry>

fn contains_key(&self, key: &usize) -> bool

fn for_each_entry<F: FnMut(&Entry)>(&self, f: F)

fn clear(&mut self)

fn reserve(&mut self, additional: usize)

Implementors

impl MapStorage for FastHashMap