alloc/collections/btree/map/
entry.rs

1use core::fmt::{self, Debug};
2use core::marker::PhantomData;
3use core::mem;
4
5use Entry::*;
6
7use super::super::borrow::DormantMutRef;
8use super::super::node::{Handle, NodeRef, marker};
9use super::BTreeMap;
10use crate::alloc::{Allocator, Global};
11
12/// A view into a single entry in a map, which may either be vacant or occupied.
13///
14/// This `enum` is constructed from the [`entry`] method on [`BTreeMap`].
15///
16/// [`entry`]: BTreeMap::entry
17#[stable(feature = "rust1", since = "1.0.0")]
18#[cfg_attr(not(test), rustc_diagnostic_item = "BTreeEntry")]
19pub enum Entry<
20    'a,
21    K: 'a,
22    V: 'a,
23    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + Clone = Global,
24> {
25    /// A vacant entry.
26    #[stable(feature = "rust1", since = "1.0.0")]
27    Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V, A>),
28
29    /// An occupied entry.
30    #[stable(feature = "rust1", since = "1.0.0")]
31    Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V, A>),
32}
33
34#[stable(feature = "debug_btree_map", since = "1.12.0")]
35impl<K: Debug + Ord, V: Debug, A: Allocator + Clone> Debug for Entry<'_, K, V, A> {
36    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
37        match *self {
38            Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
39            Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
40        }
41    }
42}
43
44/// A view into a vacant entry in a `BTreeMap`.
45/// It is part of the [`Entry`] enum.
46#[stable(feature = "rust1", since = "1.0.0")]
47pub struct VacantEntry<
48    'a,
49    K,
50    V,
51    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + Clone = Global,
52> {
53    pub(super) key: K,
54    /// `None` for a (empty) map without root
55    pub(super) handle: Option<Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>>,
56    pub(super) dormant_map: DormantMutRef<'a, BTreeMap<K, V, A>>,
57
58    /// The BTreeMap will outlive this IntoIter so we don't care about drop order for `alloc`.
59    pub(super) alloc: A,
60
61    // Be invariant in `K` and `V`
62    pub(super) _marker: PhantomData<&'a mut (K, V)>,
63}
64
65#[stable(feature = "debug_btree_map", since = "1.12.0")]
66impl<K: Debug + Ord, V, A: Allocator + Clone> Debug for VacantEntry<'_, K, V, A> {
67    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
68        f.debug_tuple("VacantEntry").field(self.key()).finish()
69    }
70}
71
72/// A view into an occupied entry in a `BTreeMap`.
73/// It is part of the [`Entry`] enum.
74#[stable(feature = "rust1", since = "1.0.0")]
75pub struct OccupiedEntry<
76    'a,
77    K,
78    V,
79    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + Clone = Global,
80> {
81    pub(super) handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>,
82    pub(super) dormant_map: DormantMutRef<'a, BTreeMap<K, V, A>>,
83
84    /// The BTreeMap will outlive this IntoIter so we don't care about drop order for `alloc`.
85    pub(super) alloc: A,
86
87    // Be invariant in `K` and `V`
88    pub(super) _marker: PhantomData<&'a mut (K, V)>,
89}
90
91#[stable(feature = "debug_btree_map", since = "1.12.0")]
92impl<K: Debug + Ord, V: Debug, A: Allocator + Clone> Debug for OccupiedEntry<'_, K, V, A> {
93    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
94        f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
95    }
96}
97
98/// The error returned by [`try_insert`](BTreeMap::try_insert) when the key already exists.
99///
100/// Contains the occupied entry, and the value that was not inserted.
101#[unstable(feature = "map_try_insert", issue = "82766")]
102pub struct OccupiedError<
103    'a,
104    K: 'a,
105    V: 'a,
106    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + Clone = Global,
107> {
108    /// The entry in the map that was already occupied.
109    pub entry: OccupiedEntry<'a, K, V, A>,
110    /// The value which was not inserted, because the entry was already occupied.
111    pub value: V,
112}
113
114#[unstable(feature = "map_try_insert", issue = "82766")]
115impl<K: Debug + Ord, V: Debug, A: Allocator + Clone> Debug for OccupiedError<'_, K, V, A> {
116    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
117        f.debug_struct("OccupiedError")
118            .field("key", self.entry.key())
119            .field("old_value", self.entry.get())
120            .field("new_value", &self.value)
121            .finish()
122    }
123}
124
125#[unstable(feature = "map_try_insert", issue = "82766")]
126impl<'a, K: Debug + Ord, V: Debug, A: Allocator + Clone> fmt::Display
127    for OccupiedError<'a, K, V, A>
128{
129    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
130        write!(
131            f,
132            "failed to insert {:?}, key {:?} already exists with value {:?}",
133            self.value,
134            self.entry.key(),
135            self.entry.get(),
136        )
137    }
138}
139
140#[unstable(feature = "map_try_insert", issue = "82766")]
141impl<'a, K: core::fmt::Debug + Ord, V: core::fmt::Debug> core::error::Error
142    for crate::collections::btree_map::OccupiedError<'a, K, V>
143{
144}
145
146impl<'a, K: Ord, V, A: Allocator + Clone> Entry<'a, K, V, A> {
147    /// Ensures a value is in the entry by inserting the default if empty, and returns
148    /// a mutable reference to the value in the entry.
149    ///
150    /// # Examples
151    ///
152    /// ```
153    /// use std::collections::BTreeMap;
154    ///
155    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
156    /// map.entry("poneyland").or_insert(12);
157    ///
158    /// assert_eq!(map["poneyland"], 12);
159    /// ```
160    #[stable(feature = "rust1", since = "1.0.0")]
161    pub fn or_insert(self, default: V) -> &'a mut V {
162        match self {
163            Occupied(entry) => entry.into_mut(),
164            Vacant(entry) => entry.insert(default),
165        }
166    }
167
168    /// Ensures a value is in the entry by inserting the result of the default function if empty,
169    /// and returns a mutable reference to the value in the entry.
170    ///
171    /// # Examples
172    ///
173    /// ```
174    /// use std::collections::BTreeMap;
175    ///
176    /// let mut map: BTreeMap<&str, String> = BTreeMap::new();
177    /// let s = "hoho".to_string();
178    ///
179    /// map.entry("poneyland").or_insert_with(|| s);
180    ///
181    /// assert_eq!(map["poneyland"], "hoho".to_string());
182    /// ```
183    #[stable(feature = "rust1", since = "1.0.0")]
184    pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
185        match self {
186            Occupied(entry) => entry.into_mut(),
187            Vacant(entry) => entry.insert(default()),
188        }
189    }
190
191    /// Ensures a value is in the entry by inserting, if empty, the result of the default function.
192    ///
193    /// This method allows for generating key-derived values for insertion by providing the default
194    /// function a reference to the key that was moved during the `.entry(key)` method call.
195    ///
196    /// The reference to the moved key is provided so that cloning or copying the key is
197    /// unnecessary, unlike with `.or_insert_with(|| ... )`.
198    ///
199    /// # Examples
200    ///
201    /// ```
202    /// use std::collections::BTreeMap;
203    ///
204    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
205    ///
206    /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
207    ///
208    /// assert_eq!(map["poneyland"], 9);
209    /// ```
210    #[inline]
211    #[stable(feature = "or_insert_with_key", since = "1.50.0")]
212    pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
213        match self {
214            Occupied(entry) => entry.into_mut(),
215            Vacant(entry) => {
216                let value = default(entry.key());
217                entry.insert(value)
218            }
219        }
220    }
221
222    /// Returns a reference to this entry's key.
223    ///
224    /// # Examples
225    ///
226    /// ```
227    /// use std::collections::BTreeMap;
228    ///
229    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
230    /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
231    /// ```
232    #[stable(feature = "map_entry_keys", since = "1.10.0")]
233    pub fn key(&self) -> &K {
234        match *self {
235            Occupied(ref entry) => entry.key(),
236            Vacant(ref entry) => entry.key(),
237        }
238    }
239
240    /// Provides in-place mutable access to an occupied entry before any
241    /// potential inserts into the map.
242    ///
243    /// # Examples
244    ///
245    /// ```
246    /// use std::collections::BTreeMap;
247    ///
248    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
249    ///
250    /// map.entry("poneyland")
251    ///    .and_modify(|e| { *e += 1 })
252    ///    .or_insert(42);
253    /// assert_eq!(map["poneyland"], 42);
254    ///
255    /// map.entry("poneyland")
256    ///    .and_modify(|e| { *e += 1 })
257    ///    .or_insert(42);
258    /// assert_eq!(map["poneyland"], 43);
259    /// ```
260    #[stable(feature = "entry_and_modify", since = "1.26.0")]
261    pub fn and_modify<F>(self, f: F) -> Self
262    where
263        F: FnOnce(&mut V),
264    {
265        match self {
266            Occupied(mut entry) => {
267                f(entry.get_mut());
268                Occupied(entry)
269            }
270            Vacant(entry) => Vacant(entry),
271        }
272    }
273
274    /// Sets the value of the entry, and returns an `OccupiedEntry`.
275    ///
276    /// # Examples
277    ///
278    /// ```
279    /// use std::collections::BTreeMap;
280    ///
281    /// let mut map: BTreeMap<&str, String> = BTreeMap::new();
282    /// let entry = map.entry("poneyland").insert_entry("hoho".to_string());
283    ///
284    /// assert_eq!(entry.key(), &"poneyland");
285    /// ```
286    #[inline]
287    #[stable(feature = "btree_entry_insert", since = "CURRENT_RUSTC_VERSION")]
288    pub fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V, A> {
289        match self {
290            Occupied(mut entry) => {
291                entry.insert(value);
292                entry
293            }
294            Vacant(entry) => entry.insert_entry(value),
295        }
296    }
297}
298
299impl<'a, K: Ord, V: Default, A: Allocator + Clone> Entry<'a, K, V, A> {
300    #[stable(feature = "entry_or_default", since = "1.28.0")]
301    /// Ensures a value is in the entry by inserting the default value if empty,
302    /// and returns a mutable reference to the value in the entry.
303    ///
304    /// # Examples
305    ///
306    /// ```
307    /// use std::collections::BTreeMap;
308    ///
309    /// let mut map: BTreeMap<&str, Option<usize>> = BTreeMap::new();
310    /// map.entry("poneyland").or_default();
311    ///
312    /// assert_eq!(map["poneyland"], None);
313    /// ```
314    pub fn or_default(self) -> &'a mut V {
315        match self {
316            Occupied(entry) => entry.into_mut(),
317            Vacant(entry) => entry.insert(Default::default()),
318        }
319    }
320}
321
322impl<'a, K: Ord, V, A: Allocator + Clone> VacantEntry<'a, K, V, A> {
323    /// Gets a reference to the key that would be used when inserting a value
324    /// through the VacantEntry.
325    ///
326    /// # Examples
327    ///
328    /// ```
329    /// use std::collections::BTreeMap;
330    ///
331    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
332    /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
333    /// ```
334    #[stable(feature = "map_entry_keys", since = "1.10.0")]
335    pub fn key(&self) -> &K {
336        &self.key
337    }
338
339    /// Take ownership of the key.
340    ///
341    /// # Examples
342    ///
343    /// ```
344    /// use std::collections::BTreeMap;
345    /// use std::collections::btree_map::Entry;
346    ///
347    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
348    ///
349    /// if let Entry::Vacant(v) = map.entry("poneyland") {
350    ///     v.into_key();
351    /// }
352    /// ```
353    #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
354    pub fn into_key(self) -> K {
355        self.key
356    }
357
358    /// Sets the value of the entry with the `VacantEntry`'s key,
359    /// and returns a mutable reference to it.
360    ///
361    /// # Examples
362    ///
363    /// ```
364    /// use std::collections::BTreeMap;
365    /// use std::collections::btree_map::Entry;
366    ///
367    /// let mut map: BTreeMap<&str, u32> = BTreeMap::new();
368    ///
369    /// if let Entry::Vacant(o) = map.entry("poneyland") {
370    ///     o.insert(37);
371    /// }
372    /// assert_eq!(map["poneyland"], 37);
373    /// ```
374    #[stable(feature = "rust1", since = "1.0.0")]
375    #[rustc_confusables("push", "put")]
376    pub fn insert(self, value: V) -> &'a mut V {
377        self.insert_entry(value).into_mut()
378    }
379
380    /// Sets the value of the entry with the `VacantEntry`'s key,
381    /// and returns an `OccupiedEntry`.
382    ///
383    /// # Examples
384    ///
385    /// ```
386    /// use std::collections::BTreeMap;
387    /// use std::collections::btree_map::Entry;
388    ///
389    /// let mut map: BTreeMap<&str, u32> = BTreeMap::new();
390    ///
391    /// if let Entry::Vacant(o) = map.entry("poneyland") {
392    ///     let entry = o.insert_entry(37);
393    ///     assert_eq!(entry.get(), &37);
394    /// }
395    /// assert_eq!(map["poneyland"], 37);
396    /// ```
397    #[stable(feature = "btree_entry_insert", since = "CURRENT_RUSTC_VERSION")]
398    pub fn insert_entry(mut self, value: V) -> OccupiedEntry<'a, K, V, A> {
399        let handle = match self.handle {
400            None => {
401                // SAFETY: There is no tree yet so no reference to it exists.
402                let map = unsafe { self.dormant_map.reborrow() };
403                let root = map.root.insert(NodeRef::new_leaf(self.alloc.clone()).forget_type());
404                // SAFETY: We *just* created the root as a leaf, and we're
405                // stacking the new handle on the original borrow lifetime.
406                unsafe {
407                    let mut leaf = root.borrow_mut().cast_to_leaf_unchecked();
408                    leaf.push_with_handle(self.key, value)
409                }
410            }
411            Some(handle) => handle.insert_recursing(self.key, value, self.alloc.clone(), |ins| {
412                drop(ins.left);
413                // SAFETY: Pushing a new root node doesn't invalidate
414                // handles to existing nodes.
415                let map = unsafe { self.dormant_map.reborrow() };
416                let root = map.root.as_mut().unwrap(); // same as ins.left
417                root.push_internal_level(self.alloc.clone()).push(ins.kv.0, ins.kv.1, ins.right)
418            }),
419        };
420
421        // SAFETY: modifying the length doesn't invalidate handles to existing nodes.
422        unsafe { self.dormant_map.reborrow().length += 1 };
423
424        OccupiedEntry {
425            handle: handle.forget_node_type(),
426            dormant_map: self.dormant_map,
427            alloc: self.alloc,
428            _marker: PhantomData,
429        }
430    }
431}
432
433impl<'a, K: Ord, V, A: Allocator + Clone> OccupiedEntry<'a, K, V, A> {
434    /// Gets a reference to the key in the entry.
435    ///
436    /// # Examples
437    ///
438    /// ```
439    /// use std::collections::BTreeMap;
440    ///
441    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
442    /// map.entry("poneyland").or_insert(12);
443    /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
444    /// ```
445    #[must_use]
446    #[stable(feature = "map_entry_keys", since = "1.10.0")]
447    pub fn key(&self) -> &K {
448        self.handle.reborrow().into_kv().0
449    }
450
451    /// Converts the entry into a reference to its key.
452    pub(crate) fn into_key(self) -> &'a K {
453        self.handle.into_kv_mut().0
454    }
455
456    /// Take ownership of the key and value from the map.
457    ///
458    /// # Examples
459    ///
460    /// ```
461    /// use std::collections::BTreeMap;
462    /// use std::collections::btree_map::Entry;
463    ///
464    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
465    /// map.entry("poneyland").or_insert(12);
466    ///
467    /// if let Entry::Occupied(o) = map.entry("poneyland") {
468    ///     // We delete the entry from the map.
469    ///     o.remove_entry();
470    /// }
471    ///
472    /// // If now try to get the value, it will panic:
473    /// // println!("{}", map["poneyland"]);
474    /// ```
475    #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
476    pub fn remove_entry(self) -> (K, V) {
477        self.remove_kv()
478    }
479
480    /// Gets a reference to the value in the entry.
481    ///
482    /// # Examples
483    ///
484    /// ```
485    /// use std::collections::BTreeMap;
486    /// use std::collections::btree_map::Entry;
487    ///
488    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
489    /// map.entry("poneyland").or_insert(12);
490    ///
491    /// if let Entry::Occupied(o) = map.entry("poneyland") {
492    ///     assert_eq!(o.get(), &12);
493    /// }
494    /// ```
495    #[must_use]
496    #[stable(feature = "rust1", since = "1.0.0")]
497    pub fn get(&self) -> &V {
498        self.handle.reborrow().into_kv().1
499    }
500
501    /// Gets a mutable reference to the value in the entry.
502    ///
503    /// If you need a reference to the `OccupiedEntry` that may outlive the
504    /// destruction of the `Entry` value, see [`into_mut`].
505    ///
506    /// [`into_mut`]: OccupiedEntry::into_mut
507    ///
508    /// # Examples
509    ///
510    /// ```
511    /// use std::collections::BTreeMap;
512    /// use std::collections::btree_map::Entry;
513    ///
514    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
515    /// map.entry("poneyland").or_insert(12);
516    ///
517    /// assert_eq!(map["poneyland"], 12);
518    /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
519    ///     *o.get_mut() += 10;
520    ///     assert_eq!(*o.get(), 22);
521    ///
522    ///     // We can use the same Entry multiple times.
523    ///     *o.get_mut() += 2;
524    /// }
525    /// assert_eq!(map["poneyland"], 24);
526    /// ```
527    #[stable(feature = "rust1", since = "1.0.0")]
528    pub fn get_mut(&mut self) -> &mut V {
529        self.handle.kv_mut().1
530    }
531
532    /// Converts the entry into a mutable reference to its value.
533    ///
534    /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
535    ///
536    /// [`get_mut`]: OccupiedEntry::get_mut
537    ///
538    /// # Examples
539    ///
540    /// ```
541    /// use std::collections::BTreeMap;
542    /// use std::collections::btree_map::Entry;
543    ///
544    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
545    /// map.entry("poneyland").or_insert(12);
546    ///
547    /// assert_eq!(map["poneyland"], 12);
548    /// if let Entry::Occupied(o) = map.entry("poneyland") {
549    ///     *o.into_mut() += 10;
550    /// }
551    /// assert_eq!(map["poneyland"], 22);
552    /// ```
553    #[must_use = "`self` will be dropped if the result is not used"]
554    #[stable(feature = "rust1", since = "1.0.0")]
555    pub fn into_mut(self) -> &'a mut V {
556        self.handle.into_val_mut()
557    }
558
559    /// Sets the value of the entry with the `OccupiedEntry`'s key,
560    /// and returns the entry's old value.
561    ///
562    /// # Examples
563    ///
564    /// ```
565    /// use std::collections::BTreeMap;
566    /// use std::collections::btree_map::Entry;
567    ///
568    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
569    /// map.entry("poneyland").or_insert(12);
570    ///
571    /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
572    ///     assert_eq!(o.insert(15), 12);
573    /// }
574    /// assert_eq!(map["poneyland"], 15);
575    /// ```
576    #[stable(feature = "rust1", since = "1.0.0")]
577    #[rustc_confusables("push", "put")]
578    pub fn insert(&mut self, value: V) -> V {
579        mem::replace(self.get_mut(), value)
580    }
581
582    /// Takes the value of the entry out of the map, and returns it.
583    ///
584    /// # Examples
585    ///
586    /// ```
587    /// use std::collections::BTreeMap;
588    /// use std::collections::btree_map::Entry;
589    ///
590    /// let mut map: BTreeMap<&str, usize> = BTreeMap::new();
591    /// map.entry("poneyland").or_insert(12);
592    ///
593    /// if let Entry::Occupied(o) = map.entry("poneyland") {
594    ///     assert_eq!(o.remove(), 12);
595    /// }
596    /// // If we try to get "poneyland"'s value, it'll panic:
597    /// // println!("{}", map["poneyland"]);
598    /// ```
599    #[stable(feature = "rust1", since = "1.0.0")]
600    #[rustc_confusables("delete", "take")]
601    pub fn remove(self) -> V {
602        self.remove_kv().1
603    }
604
605    // Body of `remove_entry`, probably separate because the name reflects the returned pair.
606    pub(super) fn remove_kv(self) -> (K, V) {
607        let mut emptied_internal_root = false;
608        let (old_kv, _) =
609            self.handle.remove_kv_tracking(|| emptied_internal_root = true, self.alloc.clone());
610        // SAFETY: we consumed the intermediate root borrow, `self.handle`.
611        let map = unsafe { self.dormant_map.awaken() };
612        map.length -= 1;
613        if emptied_internal_root {
614            let root = map.root.as_mut().unwrap();
615            root.pop_internal_level(self.alloc);
616        }
617        old_kv
618    }
619}