Struct engine_traits::IndexHandles

pub struct IndexHandles(BTreeMap<Vec<u8>, IndexHandle>);

Implementations

impl IndexHandles

pub fn new() -> IndexHandles

pub fn into_map(self) -> BTreeMap<Vec<u8>, IndexHandle>

pub fn add(&mut self, key: Vec<u8>, index_handle: IndexHandle)

pub fn encode(&self) -> Vec<u8>

pub fn decode(buf: &[u8]) -> Result<IndexHandles>

Methods from Deref<Target = BTreeMap<Vec<u8>, IndexHandle>>

pub fn clear(&mut self)

Clears the map, removing all elements.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut a = BTreeMap::new();
a.insert(1, "a");
a.clear();
assert!(a.is_empty());

pub fn get<Q>(&self, key: &Q) -> Option<&V> where
    K: Borrow<Q> + Ord,
    Q: Ord + ?Sized, 

Returns a reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);

pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)> where
    K: Borrow<Q> + Ord,
    Q: Ord + ?Sized, 

Returns the key-value pair corresponding to the supplied key.

The supplied key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

Examples

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
assert_eq!(map.get_key_value(&2), None);

pub fn first_key_value(&self) -> Option<(&K, &V)> where
    K: Ord, 

🔬 This is a nightly-only experimental API. (map_first_last)

Returns the first key-value pair in the map. The key in this pair is the minimum key in the map.

Examples

Basic usage:

#![feature(map_first_last)]
use std::collections::BTreeMap;

let mut map = BTreeMap::new();
assert_eq!(map.first_key_value(), None);
map.insert(1, "b");
map.insert(2, "a");
assert_eq!(map.first_key_value(), Some((&1, &"b")));

pub fn first_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> where
    K: Ord, 

🔬 This is a nightly-only experimental API. (map_first_last)

Returns the first entry in the map for in-place manipulation. The key of this entry is the minimum key in the map.

Examples

#![feature(map_first_last)]
use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
map.insert(2, "b");
if let Some(mut entry) = map.first_entry() {
    if *entry.key() > 0 {
        entry.insert("first");
    }
}
assert_eq!(*map.get(&1).unwrap(), "first");
assert_eq!(*map.get(&2).unwrap(), "b");

pub fn pop_first(&mut self) -> Option<(K, V)> where
    K: Ord, 

🔬 This is a nightly-only experimental API. (map_first_last)

Removes and returns the first element in the map. The key of this element is the minimum key that was in the map.

Examples

Draining elements in ascending order, while keeping a usable map each iteration.

#![feature(map_first_last)]
use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
map.insert(2, "b");
while let Some((key, _val)) = map.pop_first() {
    assert!(map.iter().all(|(k, _v)| *k > key));
}
assert!(map.is_empty());

pub fn last_key_value(&self) -> Option<(&K, &V)> where
    K: Ord, 

🔬 This is a nightly-only experimental API. (map_first_last)

Returns the last key-value pair in the map. The key in this pair is the maximum key in the map.

Examples

Basic usage:

#![feature(map_first_last)]
use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "b");
map.insert(2, "a");
assert_eq!(map.last_key_value(), Some((&2, &"a")));

pub fn last_entry(&mut self) -> Option<OccupiedEntry<'_, K, V>> where
    K: Ord, 

🔬 This is a nightly-only experimental API. (map_first_last)

Returns the last entry in the map for in-place manipulation. The key of this entry is the maximum key in the map.

Examples

#![feature(map_first_last)]
use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
map.insert(2, "b");
if let Some(mut entry) = map.last_entry() {
    if *entry.key() > 0 {
        entry.insert("last");
    }
}
assert_eq!(*map.get(&1).unwrap(), "a");
assert_eq!(*map.get(&2).unwrap(), "last");

pub fn pop_last(&mut self) -> Option<(K, V)> where
    K: Ord, 

🔬 This is a nightly-only experimental API. (map_first_last)

Removes and returns the last element in the map. The key of this element is the maximum key that was in the map.

Examples

Draining elements in descending order, while keeping a usable map each iteration.

#![feature(map_first_last)]
use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
map.insert(2, "b");
while let Some((key, _val)) = map.pop_last() {
    assert!(map.iter().all(|(k, _v)| *k < key));
}
assert!(map.is_empty());

pub fn contains_key<Q>(&self, key: &Q) -> bool where
    K: Borrow<Q> + Ord,
    Q: Ord + ?Sized, 

Returns true if the map contains a value for the specified key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);

pub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut V> where
    K: Borrow<Q> + Ord,
    Q: Ord + ?Sized, 

Returns a mutable reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
if let Some(x) = map.get_mut(&1) {
    *x = "b";
}
assert_eq!(map[&1], "b");

pub fn insert(&mut self, key: K, value: V) -> Option<V> where
    K: Ord, 

Inserts a key-value pair into the map.

If the map did not have this key present, None is returned.

If the map did have this key present, the value is updated, and the old value is returned. The key is not updated, though; this matters for types that can be == without being identical. See the module-level documentation for more.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
assert_eq!(map.insert(37, "a"), None);
assert_eq!(map.is_empty(), false);

map.insert(37, "b");
assert_eq!(map.insert(37, "c"), Some("b"));
assert_eq!(map[&37], "c");

pub fn try_insert(
    &mut self,
    key: K,
    value: V
) -> Result<&mut V, OccupiedError<'_, K, V>> where
    K: Ord, 

🔬 This is a nightly-only experimental API. (map_try_insert)

Tries to insert a key-value pair into the map, and returns a mutable reference to the value in the entry.

If the map already had this key present, nothing is updated, and an error containing the occupied entry and the value is returned.

Examples

Basic usage:

#![feature(map_try_insert)]

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
assert_eq!(map.try_insert(37, "a").unwrap(), &"a");

let err = map.try_insert(37, "b").unwrap_err();
assert_eq!(err.entry.key(), &37);
assert_eq!(err.entry.get(), &"a");
assert_eq!(err.value, "b");

pub fn remove<Q>(&mut self, key: &Q) -> Option<V> where
    K: Borrow<Q> + Ord,
    Q: Ord + ?Sized, 

Removes a key from the map, returning the value at the key if the key was previously in the map.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);

pub fn remove_entry<Q>(&mut self, key: &Q) -> Option<(K, V)> where
    K: Borrow<Q> + Ord,
    Q: Ord + ?Sized, 

Removes a key from the map, returning the stored key and value if the key was previously in the map.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(1, "a");
assert_eq!(map.remove_entry(&1), Some((1, "a")));
assert_eq!(map.remove_entry(&1), None);

pub fn retain<F>(&mut self, f: F) where
    F: FnMut(&K, &mut V) -> bool,
    K: Ord, 

Retains only the elements specified by the predicate.

In other words, remove all pairs (k, v) such that f(&k, &mut v) returns false.

Examples

use std::collections::BTreeMap;

let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x*10)).collect();
// Keep only the elements with even-numbered keys.
map.retain(|&k, _| k % 2 == 0);
assert!(map.into_iter().eq(vec![(0, 0), (2, 20), (4, 40), (6, 60)]));

pub fn append(&mut self, other: &mut BTreeMap<K, V>) where
    K: Ord, 

Moves all elements from other into Self, leaving other empty.

Examples

use std::collections::BTreeMap;

let mut a = BTreeMap::new();
a.insert(1, "a");
a.insert(2, "b");
a.insert(3, "c");

let mut b = BTreeMap::new();
b.insert(3, "d");
b.insert(4, "e");
b.insert(5, "f");

a.append(&mut b);

assert_eq!(a.len(), 5);
assert_eq!(b.len(), 0);

assert_eq!(a[&1], "a");
assert_eq!(a[&2], "b");
assert_eq!(a[&3], "d");
assert_eq!(a[&4], "e");
assert_eq!(a[&5], "f");

pub fn range<T, R>(&self, range: R) -> Range<'_, K, V> where
    T: Ord + ?Sized,
    K: Borrow<T> + Ord,
    R: RangeBounds<T>, 

Constructs a double-ended iterator over a sub-range of elements in the map. The simplest way is to use the range syntax min..max, thus range(min..max) will yield elements from min (inclusive) to max (exclusive). The range may also be entered as (Bound<T>, Bound<T>), so for example range((Excluded(4), Included(10))) will yield a left-exclusive, right-inclusive range from 4 to 10.

Panics

Panics if range start > end. Panics if range start == end and both bounds are Excluded.

Examples

Basic usage:

use std::collections::BTreeMap;
use std::ops::Bound::Included;

let mut map = BTreeMap::new();
map.insert(3, "a");
map.insert(5, "b");
map.insert(8, "c");
for (&key, &value) in map.range((Included(&4), Included(&8))) {
    println!("{}: {}", key, value);
}
assert_eq!(Some((&5, &"b")), map.range(4..).next());

pub fn range_mut<T, R>(&mut self, range: R) -> RangeMut<'_, K, V> where
    T: Ord + ?Sized,
    K: Borrow<T> + Ord,
    R: RangeBounds<T>, 

Constructs a mutable double-ended iterator over a sub-range of elements in the map. The simplest way is to use the range syntax min..max, thus range(min..max) will yield elements from min (inclusive) to max (exclusive). The range may also be entered as (Bound<T>, Bound<T>), so for example range((Excluded(4), Included(10))) will yield a left-exclusive, right-inclusive range from 4 to 10.

Panics

Panics if range start > end. Panics if range start == end and both bounds are Excluded.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"]
    .iter()
    .map(|&s| (s, 0))
    .collect();
for (_, balance) in map.range_mut("B".."Cheryl") {
    *balance += 100;
}
for (name, balance) in &map {
    println!("{} => {}", name, balance);
}

pub fn entry(&mut self, key: K) -> Entry<'_, K, V> where
    K: Ord, 

Gets the given key’s corresponding entry in the map for in-place manipulation.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut count: BTreeMap<&str, usize> = BTreeMap::new();

// count the number of occurrences of letters in the vec
for x in vec!["a", "b", "a", "c", "a", "b"] {
    *count.entry(x).or_insert(0) += 1;
}

assert_eq!(count["a"], 3);

pub fn split_off<Q>(&mut self, key: &Q) -> BTreeMap<K, V> where
    K: Borrow<Q> + Ord,
    Q: Ord + ?Sized, 

Splits the collection into two at the given key. Returns everything after the given key, including the key.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut a = BTreeMap::new();
a.insert(1, "a");
a.insert(2, "b");
a.insert(3, "c");
a.insert(17, "d");
a.insert(41, "e");

let b = a.split_off(&3);

assert_eq!(a.len(), 2);
assert_eq!(b.len(), 3);

assert_eq!(a[&1], "a");
assert_eq!(a[&2], "b");

assert_eq!(b[&3], "c");
assert_eq!(b[&17], "d");
assert_eq!(b[&41], "e");

pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F> where
    F: FnMut(&K, &mut V) -> bool,
    K: Ord, 

🔬 This is a nightly-only experimental API. (btree_drain_filter)

Creates an iterator that visits all elements (key-value pairs) in ascending key order and uses a closure to determine if an element should be removed. If the closure returns true, the element is removed from the map and yielded. If the closure returns false, or panics, the element remains in the map and will not be yielded.

The iterator also lets you mutate the value of each element in the closure, regardless of whether you choose to keep or remove it.

If the iterator is only partially consumed or not consumed at all, each of the remaining elements is still subjected to the closure, which may change its value and, by returning true, have the element removed and dropped.

It is unspecified how many more elements will be subjected to the closure if a panic occurs in the closure, or a panic occurs while dropping an element, or if the DrainFilter value is leaked.

Examples

Splitting a map into even and odd keys, reusing the original map:

#![feature(btree_drain_filter)]
use std::collections::BTreeMap;

let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
let evens: BTreeMap<_, _> = map.drain_filter(|k, _v| k % 2 == 0).collect();
let odds = map;
assert_eq!(evens.keys().copied().collect::<Vec<_>>(), vec![0, 2, 4, 6]);
assert_eq!(odds.keys().copied().collect::<Vec<_>>(), vec![1, 3, 5, 7]);

pub fn iter(&self) -> Iter<'_, K, V>

Gets an iterator over the entries of the map, sorted by key.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert(3, "c");
map.insert(2, "b");
map.insert(1, "a");

for (key, value) in map.iter() {
    println!("{}: {}", key, value);
}

let (first_key, first_value) = map.iter().next().unwrap();
assert_eq!((*first_key, *first_value), (1, "a"));

pub fn iter_mut(&mut self) -> IterMut<'_, K, V>

Gets a mutable iterator over the entries of the map, sorted by key.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut map = BTreeMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

// add 10 to the value if the key isn't "a"
for (key, value) in map.iter_mut() {
    if key != &"a" {
        *value += 10;
    }
}

pub fn keys(&self) -> Keys<'_, K, V>

Gets an iterator over the keys of the map, in sorted order.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut a = BTreeMap::new();
a.insert(2, "b");
a.insert(1, "a");

let keys: Vec<_> = a.keys().cloned().collect();
assert_eq!(keys, [1, 2]);

pub fn values(&self) -> Values<'_, K, V>

Gets an iterator over the values of the map, in order by key.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut a = BTreeMap::new();
a.insert(1, "hello");
a.insert(2, "goodbye");

let values: Vec<&str> = a.values().cloned().collect();
assert_eq!(values, ["hello", "goodbye"]);

pub fn values_mut(&mut self) -> ValuesMut<'_, K, V>

Gets a mutable iterator over the values of the map, in order by key.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut a = BTreeMap::new();
a.insert(1, String::from("hello"));
a.insert(2, String::from("goodbye"));

for value in a.values_mut() {
    value.push_str("!");
}

let values: Vec<String> = a.values().cloned().collect();
assert_eq!(values, [String::from("hello!"),
                    String::from("goodbye!")]);

pub const fn len(&self) -> usize

Returns the number of elements in the map.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut a = BTreeMap::new();
assert_eq!(a.len(), 0);
a.insert(1, "a");
assert_eq!(a.len(), 1);

pub const fn is_empty(&self) -> bool

Returns true if the map contains no elements.

Examples

Basic usage:

use std::collections::BTreeMap;

let mut a = BTreeMap::new();
assert!(a.is_empty());
a.insert(1, "a");
assert!(!a.is_empty());

Trait Implementations

impl Debug for IndexHandles

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

Formats the value using the given formatter.

impl Default for IndexHandles

fn default() -> IndexHandles

Returns the “default value” for a type.

impl Deref for IndexHandles

type Target = BTreeMap<Vec<u8>, IndexHandle>

The resulting type after dereferencing.

fn deref(&self) -> &BTreeMap<Vec<u8>, IndexHandle>

Dereferences the value.

impl DerefMut for IndexHandles

fn deref_mut(&mut self) -> &mut BTreeMap<Vec<u8>, IndexHandle>

Mutably dereferences the value.