Struct alloc::collections::btree_map::CursorMut

pub struct CursorMut<'a, K: 'a, V: 'a, A = Global> {
    current: Option<Handle<NodeRef<Mut<'a>, K, V, LeafOrInternal>, KV>>,
    root: DormantMutRef<'a, Option<NodeRef<Owned, K, V, LeafOrInternal>>>,
    length: &'a mut usize,
    alloc: &'a mut A,
}

🔬This is a nightly-only experimental API. (btree_cursors #107540)

A cursor over a BTreeMap with editing operations.

A Cursor is like an iterator, except that it can freely seek back-and-forth, and can safely mutate the tree during iteration. This is because the lifetime of its yielded references is tied to its own lifetime, instead of just the underlying tree. This means cursors cannot yield multiple elements at once.

Cursors always point to an element in the tree, and index in a logically circular way. To accommodate this, there is a “ghost” non-element that yields None between the last and first elements of the tree.

A Cursor is created with the BTreeMap::lower_bound_mut and BTreeMap::upper_bound_mut methods.

Fields

current: Option<Handle<NodeRef<Mut<'a>, K, V, LeafOrInternal>, KV>>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

root: DormantMutRef<'a, Option<NodeRef<Owned, K, V, LeafOrInternal>>>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

length: &'a mut usize

🔬This is a nightly-only experimental API. (btree_cursors #107540)

alloc: &'a mut A

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Implementations

impl<'a, K, V, A> CursorMut<'a, K, V, A>

pub fn move_next(&mut self)

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Moves the cursor to the next element of the BTreeMap.

If the cursor is pointing to the “ghost” non-element then this will move it to the first element of the BTreeMap. If it is pointing to the last element of the BTreeMap then this will move it to the “ghost” non-element.

pub fn move_prev(&mut self)

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Moves the cursor to the previous element of the BTreeMap.

If the cursor is pointing to the “ghost” non-element then this will move it to the last element of the BTreeMap. If it is pointing to the first element of the BTreeMap then this will move it to the “ghost” non-element.

pub fn key(&self) -> Option<&K>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a reference to the key of the element that the cursor is currently pointing to.

This returns None if the cursor is currently pointing to the “ghost” non-element.

pub fn value(&self) -> Option<&V>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a reference to the value of the element that the cursor is currently pointing to.

This returns None if the cursor is currently pointing to the “ghost” non-element.

pub fn key_value(&self) -> Option<(&K, &V)>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a reference to the key and value of the element that the cursor is currently pointing to.

This returns None if the cursor is currently pointing to the “ghost” non-element.

pub fn value_mut(&mut self) -> Option<&mut V>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a mutable reference to the value of the element that the cursor is currently pointing to.

This returns None if the cursor is currently pointing to the “ghost” non-element.

pub fn key_value_mut(&mut self) -> Option<(&K, &mut V)>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a reference to the key and mutable reference to the value of the element that the cursor is currently pointing to.

This returns None if the cursor is currently pointing to the “ghost” non-element.

pub unsafe fn key_mut_unchecked(&mut self) -> Option<&mut K>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a mutable reference to the key of the element that the cursor is currently pointing to.

This returns None if the cursor is currently pointing to the “ghost” non-element.

Safety

This can be used to modify the key, but you must ensure that the BTreeMap invariants are maintained. Specifically:

• The key must remain unique within the tree.
• The key must remain in sorted order with regards to other elements in the tree.

pub fn peek_next(&mut self) -> Option<(&K, &mut V)>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a reference to the key and value of the next element.

If the cursor is pointing to the “ghost” non-element then this returns the first element of the BTreeMap. If it is pointing to the last element of the BTreeMap then this returns None.

pub fn peek_prev(&mut self) -> Option<(&K, &mut V)>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a reference to the key and value of the previous element.

If the cursor is pointing to the “ghost” non-element then this returns the last element of the BTreeMap. If it is pointing to the first element of the BTreeMap then this returns None.

pub fn as_cursor(&self) -> Cursor<'_, K, V>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Returns a read-only cursor pointing to the current element.

The lifetime of the returned Cursor is bound to that of the CursorMut, which means it cannot outlive the CursorMut and that the CursorMut is frozen for the lifetime of the Cursor.

impl<'a, K: Ord, V, A: Allocator + Clone> CursorMut<'a, K, V, A>

pub unsafe fn insert_after_unchecked(&mut self, key: K, value: V)

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Inserts a new element into the BTreeMap after the current one.

If the cursor is pointing at the “ghost” non-element then the new element is inserted at the front of the BTreeMap.

Safety

You must ensure that the BTreeMap invariants are maintained. Specifically:

• The key of the newly inserted element must be unique in the tree.
• All keys in the tree must remain in sorted order.

pub unsafe fn insert_before_unchecked(&mut self, key: K, value: V)

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Inserts a new element into the BTreeMap before the current one.

If the cursor is pointing at the “ghost” non-element then the new element is inserted at the end of the BTreeMap.

Safety

You must ensure that the BTreeMap invariants are maintained. Specifically:

• The key of the newly inserted element must be unique in the tree.
• All keys in the tree must remain in sorted order.

pub fn insert_after(&mut self, key: K, value: V)

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Inserts a new element into the BTreeMap after the current one.

If the cursor is pointing at the “ghost” non-element then the new element is inserted at the front of the BTreeMap.

Panics

This function panics if:

• the given key compares less than or equal to the current element (if any).
• the given key compares greater than or equal to the next element (if any).

pub fn insert_before(&mut self, key: K, value: V)

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Inserts a new element into the BTreeMap before the current one.

If the cursor is pointing at the “ghost” non-element then the new element is inserted at the end of the BTreeMap.

Panics

This function panics if:

• the given key compares greater than or equal to the current element (if any).
• the given key compares less than or equal to the previous element (if any).

pub fn remove_current(&mut self) -> Option<(K, V)>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Removes the current element from the BTreeMap.

The element that was removed is returned, and the cursor is moved to point to the next element in the BTreeMap.

If the cursor is currently pointing to the “ghost” non-element then no element is removed and None is returned. The cursor is not moved in this case.

pub fn remove_current_and_move_back(&mut self) -> Option<(K, V)>

🔬This is a nightly-only experimental API. (btree_cursors #107540)

Removes the current element from the BTreeMap.

The element that was removed is returned, and the cursor is moved to point to the previous element in the BTreeMap.

If the cursor is currently pointing to the “ghost” non-element then no element is removed and None is returned. The cursor is not moved in this case.

Trait Implementations

impl<K: Debug, V: Debug, A> Debug for CursorMut<'_, K, V, A>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.