ordermap/map/

raw_entry_v1.rs

//! Opt-in access to the experimental raw entry API.
//!
//! This module is designed to mimic the raw entry API of [`HashMap`][std::collections::hash_map],
//! matching its unstable state as of Rust 1.75. See the tracking issue
//! [rust#56167](https://github.com/rust-lang/rust/issues/56167) for more details.
//!
//! The trait [`RawEntryApiV1`] and the `_v1` suffix on its methods are meant to insulate this for
//! the future, in case later breaking changes are needed. If the standard library stabilizes its
//! `hash_raw_entry` feature (or some replacement), matching *inherent* methods will be added to
//! `OrderMap` without such an opt-in trait.

use crate::{Equivalent, OrderMap};
use core::fmt;
use core::hash::{BuildHasher, Hash};
use indexmap::map::raw_entry_v1 as ix;
use indexmap::map::RawEntryApiV1 as _;

#[cfg(doc)]
use alloc::vec::Vec;

/// Opt-in access to the experimental raw entry API.
///
/// See the [`raw_entry_v1`][self] module documentation for more information.
pub trait RawEntryApiV1<K, V, S>: private::Sealed {
    /// Creates a raw immutable entry builder for the [`OrderMap`].
    ///
    /// Raw entries provide the lowest level of control for searching and
    /// manipulating a map. They must be manually initialized with a hash and
    /// then manually searched.
    ///
    /// This is useful for
    /// * Hash memoization
    /// * Using a search key that doesn't work with the [`Equivalent`] trait
    /// * Using custom comparison logic without newtype wrappers
    ///
    /// Unless you are in such a situation, higher-level and more foolproof APIs like
    /// [`get`][OrderMap::get] should be preferred.
    ///
    /// Immutable raw entries have very limited use; you might instead want
    /// [`raw_entry_mut_v1`][Self::raw_entry_mut_v1].
    ///
    /// # Examples
    ///
    /// ```
    /// use core::hash::{BuildHasher, Hash};
    /// use ordermap::map::{OrderMap, RawEntryApiV1};
    ///
    /// let mut map = OrderMap::new();
    /// map.extend([("a", 100), ("b", 200), ("c", 300)]);
    ///
    /// fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    ///     use core::hash::Hasher;
    ///     let mut state = hash_builder.build_hasher();
    ///     key.hash(&mut state);
    ///     state.finish()
    /// }
    ///
    /// for k in ["a", "b", "c", "d", "e", "f"] {
    ///     let hash = compute_hash(map.hasher(), k);
    ///     let i = map.get_index_of(k);
    ///     let v = map.get(k);
    ///     let kv = map.get_key_value(k);
    ///     let ikv = map.get_full(k);
    ///
    ///     println!("Key: {} and value: {:?}", k, v);
    ///
    ///     assert_eq!(map.raw_entry_v1().from_key(k), kv);
    ///     assert_eq!(map.raw_entry_v1().from_hash(hash, |q| *q == k), kv);
    ///     assert_eq!(map.raw_entry_v1().from_key_hashed_nocheck(hash, k), kv);
    ///     assert_eq!(map.raw_entry_v1().from_hash_full(hash, |q| *q == k), ikv);
    ///     assert_eq!(map.raw_entry_v1().index_from_hash(hash, |q| *q == k), i);
    /// }
    /// ```
    fn raw_entry_v1(&self) -> RawEntryBuilder<'_, K, V, S>;

    /// Creates a raw entry builder for the [`OrderMap`].
    ///
    /// Raw entries provide the lowest level of control for searching and
    /// manipulating a map. They must be manually initialized with a hash and
    /// then manually searched. After this, insertions into a vacant entry
    /// still require an owned key to be provided.
    ///
    /// Raw entries are useful for such exotic situations as:
    ///
    /// * Hash memoization
    /// * Deferring the creation of an owned key until it is known to be required
    /// * Using a search key that doesn't work with the [`Equivalent`] trait
    /// * Using custom comparison logic without newtype wrappers
    ///
    /// Because raw entries provide much more low-level control, it's much easier
    /// to put the `OrderMap` into an inconsistent state which, while memory-safe,
    /// will cause the map to produce seemingly random results. Higher-level and more
    /// foolproof APIs like [`entry`][OrderMap::entry] should be preferred when possible.
    ///
    /// Raw entries give mutable access to the keys. This must not be used
    /// to modify how the key would compare or hash, as the map will not re-evaluate
    /// where the key should go, meaning the keys may become "lost" if their
    /// location does not reflect their state. For instance, if you change a key
    /// so that the map now contains keys which compare equal, search may start
    /// acting erratically, with two keys randomly masking each other. Implementations
    /// are free to assume this doesn't happen (within the limits of memory-safety).
    ///
    /// # Examples
    ///
    /// ```
    /// use core::hash::{BuildHasher, Hash};
    /// use ordermap::map::{OrderMap, RawEntryApiV1};
    /// use ordermap::map::raw_entry_v1::RawEntryMut;
    ///
    /// let mut map = OrderMap::new();
    /// map.extend([("a", 100), ("b", 200), ("c", 300)]);
    ///
    /// fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    ///     use core::hash::Hasher;
    ///     let mut state = hash_builder.build_hasher();
    ///     key.hash(&mut state);
    ///     state.finish()
    /// }
    ///
    /// // Existing key (insert and update)
    /// match map.raw_entry_mut_v1().from_key("a") {
    ///     RawEntryMut::Vacant(_) => unreachable!(),
    ///     RawEntryMut::Occupied(mut view) => {
    ///         assert_eq!(view.index(), 0);
    ///         assert_eq!(view.get(), &100);
    ///         let v = view.get_mut();
    ///         let new_v = (*v) * 10;
    ///         *v = new_v;
    ///         assert_eq!(view.insert(1111), 1000);
    ///     }
    /// }
    ///
    /// assert_eq!(map["a"], 1111);
    /// assert_eq!(map.len(), 3);
    ///
    /// // Existing key (take)
    /// let hash = compute_hash(map.hasher(), "c");
    /// match map.raw_entry_mut_v1().from_key_hashed_nocheck(hash, "c") {
    ///     RawEntryMut::Vacant(_) => unreachable!(),
    ///     RawEntryMut::Occupied(view) => {
    ///         assert_eq!(view.index(), 2);
    ///         assert_eq!(view.remove_entry(), ("c", 300));
    ///     }
    /// }
    /// assert_eq!(map.raw_entry_v1().from_key("c"), None);
    /// assert_eq!(map.len(), 2);
    ///
    /// // Nonexistent key (insert and update)
    /// let key = "d";
    /// let hash = compute_hash(map.hasher(), key);
    /// match map.raw_entry_mut_v1().from_hash(hash, |q| *q == key) {
    ///     RawEntryMut::Occupied(_) => unreachable!(),
    ///     RawEntryMut::Vacant(view) => {
    ///         assert_eq!(view.index(), 2);
    ///         let (k, value) = view.insert("d", 4000);
    ///         assert_eq!((*k, *value), ("d", 4000));
    ///         *value = 40000;
    ///     }
    /// }
    /// assert_eq!(map["d"], 40000);
    /// assert_eq!(map.len(), 3);
    ///
    /// match map.raw_entry_mut_v1().from_hash(hash, |q| *q == key) {
    ///     RawEntryMut::Vacant(_) => unreachable!(),
    ///     RawEntryMut::Occupied(view) => {
    ///         assert_eq!(view.index(), 2);
    ///         assert_eq!(view.swap_remove_entry(), ("d", 40000));
    ///     }
    /// }
    /// assert_eq!(map.get("d"), None);
    /// assert_eq!(map.len(), 2);
    /// ```
    fn raw_entry_mut_v1(&mut self) -> RawEntryBuilderMut<'_, K, V, S>;
}

impl<K, V, S> RawEntryApiV1<K, V, S> for OrderMap<K, V, S> {
    fn raw_entry_v1(&self) -> RawEntryBuilder<'_, K, V, S> {
        RawEntryBuilder {
            inner: self.inner.raw_entry_v1(),
        }
    }

    fn raw_entry_mut_v1(&mut self) -> RawEntryBuilderMut<'_, K, V, S> {
        RawEntryBuilderMut {
            inner: self.inner.raw_entry_mut_v1(),
        }
    }
}

/// A builder for computing where in an [`OrderMap`] a key-value pair would be stored.
///
/// This `struct` is created by the [`OrderMap::raw_entry_v1`] method, provided by the
/// [`RawEntryApiV1`] trait. See its documentation for more.
pub struct RawEntryBuilder<'a, K, V, S> {
    inner: ix::RawEntryBuilder<'a, K, V, S>,
}

impl<K, V, S> fmt::Debug for RawEntryBuilder<'_, K, V, S> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("RawEntryBuilder").finish_non_exhaustive()
    }
}

impl<'a, K, V, S> RawEntryBuilder<'a, K, V, S> {
    /// Access an entry by key.
    pub fn from_key<Q>(self, key: &Q) -> Option<(&'a K, &'a V)>
    where
        S: BuildHasher,
        Q: ?Sized + Hash + Equivalent<K>,
    {
        self.inner.from_key(key)
    }

    /// Access an entry by a key and its hash.
    pub fn from_key_hashed_nocheck<Q>(self, hash: u64, key: &Q) -> Option<(&'a K, &'a V)>
    where
        Q: ?Sized + Equivalent<K>,
    {
        self.inner.from_key_hashed_nocheck(hash, key)
    }

    /// Access an entry by hash.
    pub fn from_hash<F>(self, hash: u64, is_match: F) -> Option<(&'a K, &'a V)>
    where
        F: FnMut(&K) -> bool,
    {
        self.inner.from_hash(hash, is_match)
    }

    /// Access an entry by hash, including its index.
    pub fn from_hash_full<F>(self, hash: u64, is_match: F) -> Option<(usize, &'a K, &'a V)>
    where
        F: FnMut(&K) -> bool,
    {
        self.inner.from_hash_full(hash, is_match)
    }

    /// Access the index of an entry by hash.
    pub fn index_from_hash<F>(self, hash: u64, is_match: F) -> Option<usize>
    where
        F: FnMut(&K) -> bool,
    {
        self.inner.index_from_hash(hash, is_match)
    }
}

/// A builder for computing where in an [`OrderMap`] a key-value pair would be stored.
///
/// This `struct` is created by the [`OrderMap::raw_entry_mut_v1`] method, provided by the
/// [`RawEntryApiV1`] trait. See its documentation for more.
pub struct RawEntryBuilderMut<'a, K, V, S> {
    inner: ix::RawEntryBuilderMut<'a, K, V, S>,
}

impl<K, V, S> fmt::Debug for RawEntryBuilderMut<'_, K, V, S> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("RawEntryBuilderMut").finish_non_exhaustive()
    }
}

impl<'a, K, V, S> RawEntryBuilderMut<'a, K, V, S> {
    /// Access an entry by key.
    pub fn from_key<Q>(self, key: &Q) -> RawEntryMut<'a, K, V, S>
    where
        S: BuildHasher,
        Q: ?Sized + Hash + Equivalent<K>,
    {
        RawEntryMut::new(self.inner.from_key(key))
    }

    /// Access an entry by a key and its hash.
    pub fn from_key_hashed_nocheck<Q>(self, hash: u64, key: &Q) -> RawEntryMut<'a, K, V, S>
    where
        Q: ?Sized + Equivalent<K>,
    {
        RawEntryMut::new(self.inner.from_key_hashed_nocheck(hash, key))
    }

    /// Access an entry by hash.
    pub fn from_hash<F>(self, hash: u64, is_match: F) -> RawEntryMut<'a, K, V, S>
    where
        F: FnMut(&K) -> bool,
    {
        RawEntryMut::new(self.inner.from_hash(hash, is_match))
    }
}

/// Raw entry for an existing key-value pair or a vacant location to
/// insert one.
pub enum RawEntryMut<'a, K, V, S> {
    /// Existing slot with equivalent key.
    Occupied(RawOccupiedEntryMut<'a, K, V, S>),
    /// Vacant slot (no equivalent key in the map).
    Vacant(RawVacantEntryMut<'a, K, V, S>),
}

impl<K: fmt::Debug, V: fmt::Debug, S> fmt::Debug for RawEntryMut<'_, K, V, S> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let mut tuple = f.debug_tuple("RawEntryMut");
        match self {
            Self::Vacant(v) => tuple.field(v),
            Self::Occupied(o) => tuple.field(o),
        };
        tuple.finish()
    }
}

impl<'a, K, V, S> RawEntryMut<'a, K, V, S> {
    fn new(entry: ix::RawEntryMut<'a, K, V, S>) -> Self {
        match entry {
            ix::RawEntryMut::Occupied(inner) => Self::Occupied(RawOccupiedEntryMut { inner }),
            ix::RawEntryMut::Vacant(inner) => Self::Vacant(RawVacantEntryMut { inner }),
        }
    }

    /// Return the index where the key-value pair exists or may be inserted.
    #[inline]
    pub fn index(&self) -> usize {
        match self {
            Self::Occupied(entry) => entry.index(),
            Self::Vacant(entry) => entry.index(),
        }
    }

    /// Inserts the given default key and value in the entry if it is vacant and returns mutable
    /// references to them. Otherwise mutable references to an already existent pair are returned.
    pub fn or_insert(self, default_key: K, default_value: V) -> (&'a mut K, &'a mut V)
    where
        K: Hash,
        S: BuildHasher,
    {
        match self {
            Self::Occupied(entry) => entry.into_key_value_mut(),
            Self::Vacant(entry) => entry.insert(default_key, default_value),
        }
    }

    /// Inserts the result of the `call` function in the entry if it is vacant and returns mutable
    /// references to them. Otherwise mutable references to an already existent pair are returned.
    pub fn or_insert_with<F>(self, call: F) -> (&'a mut K, &'a mut V)
    where
        F: FnOnce() -> (K, V),
        K: Hash,
        S: BuildHasher,
    {
        match self {
            Self::Occupied(entry) => entry.into_key_value_mut(),
            Self::Vacant(entry) => {
                let (key, value) = call();
                entry.insert(key, value)
            }
        }
    }

    /// Modifies the entry if it is occupied.
    pub fn and_modify<F>(mut self, f: F) -> Self
    where
        F: FnOnce(&mut K, &mut V),
    {
        if let Self::Occupied(entry) = &mut self {
            let (k, v) = entry.get_key_value_mut();
            f(k, v);
        }
        self
    }
}

/// A raw view into an occupied entry in an [`OrderMap`].
/// It is part of the [`RawEntryMut`] enum.
pub struct RawOccupiedEntryMut<'a, K, V, S> {
    inner: ix::RawOccupiedEntryMut<'a, K, V, S>,
}

impl<K: fmt::Debug, V: fmt::Debug, S> fmt::Debug for RawOccupiedEntryMut<'_, K, V, S> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("RawOccupiedEntryMut")
            .field("key", self.key())
            .field("value", self.get())
            .finish_non_exhaustive()
    }
}

impl<'a, K, V, S> RawOccupiedEntryMut<'a, K, V, S> {
    /// Return the index of the key-value pair
    #[inline]
    pub fn index(&self) -> usize {
        self.inner.index()
    }

    /// Gets a reference to the entry's key in the map.
    ///
    /// Note that this is not the key that was used to find the entry. There may be an observable
    /// difference if the key type has any distinguishing features outside of `Hash` and `Eq`, like
    /// extra fields or the memory address of an allocation.
    pub fn key(&self) -> &K {
        self.inner.key()
    }

    /// Gets a mutable reference to the entry's key in the map.
    ///
    /// Note that this is not the key that was used to find the entry. There may be an observable
    /// difference if the key type has any distinguishing features outside of `Hash` and `Eq`, like
    /// extra fields or the memory address of an allocation.
    pub fn key_mut(&mut self) -> &mut K {
        self.inner.key_mut()
    }

    /// Converts into a mutable reference to the entry's key in the map,
    /// with a lifetime bound to the map itself.
    ///
    /// Note that this is not the key that was used to find the entry. There may be an observable
    /// difference if the key type has any distinguishing features outside of `Hash` and `Eq`, like
    /// extra fields or the memory address of an allocation.
    pub fn into_key(self) -> &'a mut K {
        self.inner.into_key()
    }

    /// Gets a reference to the entry's value in the map.
    pub fn get(&self) -> &V {
        self.inner.get()
    }

    /// Gets a mutable reference to the entry's value in the map.
    ///
    /// If you need a reference which may outlive the destruction of the
    /// [`RawEntryMut`] value, see [`into_mut`][Self::into_mut].
    pub fn get_mut(&mut self) -> &mut V {
        self.inner.get_mut()
    }

    /// Converts into a mutable reference to the entry's value in the map,
    /// with a lifetime bound to the map itself.
    pub fn into_mut(self) -> &'a mut V {
        self.inner.into_mut()
    }

    /// Gets a reference to the entry's key and value in the map.
    pub fn get_key_value(&self) -> (&K, &V) {
        self.inner.get_key_value()
    }

    /// Gets a reference to the entry's key and value in the map.
    pub fn get_key_value_mut(&mut self) -> (&mut K, &mut V) {
        self.inner.get_key_value_mut()
    }

    /// Converts into a mutable reference to the entry's key and value in the map,
    /// with a lifetime bound to the map itself.
    pub fn into_key_value_mut(self) -> (&'a mut K, &'a mut V) {
        self.inner.into_key_value_mut()
    }

    /// Sets the value of the entry, and returns the entry's old value.
    pub fn insert(&mut self, value: V) -> V {
        self.inner.insert(value)
    }

    /// Sets the key of the entry, and returns the entry's old key.
    pub fn insert_key(&mut self, key: K) -> K {
        self.inner.insert_key(key)
    }

    /// Remove the key, value pair stored in the map for this entry, and return the value.
    ///
    /// **NOTE:** This is equivalent to indexmap's
    /// [`RawOccupiedEntryMut::shift_remove`][ix::RawOccupiedEntryMut::shift_remove], and
    /// like [`Vec::remove`], the pair is removed by shifting all of the
    /// elements that follow it, preserving their relative order.
    /// **This perturbs the index of all of those elements!**
    ///
    /// Computes in **O(n)** time (average).
    pub fn remove(self) -> V {
        self.inner.shift_remove()
    }

    /// Remove the key, value pair stored in the map for this entry, and return the value.
    ///
    /// Like [`Vec::swap_remove`], the pair is removed by swapping it with
    /// the last element of the map and popping it off.
    /// **This perturbs the position of what used to be the last element!**
    ///
    /// Computes in **O(1)** time (average).
    pub fn swap_remove(self) -> V {
        self.inner.swap_remove()
    }

    /// Remove and return the key, value pair stored in the map for this entry
    ///
    /// **NOTE:** This is equivalent to indexmap's
    /// [`RawOccupiedEntryMut::shift_remove_entry`][ix::RawOccupiedEntryMut::shift_remove_entry], and
    /// like [`Vec::remove`], the pair is removed by shifting all of the
    /// elements that follow it, preserving their relative order.
    /// **This perturbs the index of all of those elements!**
    ///
    /// Computes in **O(n)** time (average).
    pub fn remove_entry(self) -> (K, V) {
        self.inner.shift_remove_entry()
    }

    /// Remove and return the key, value pair stored in the map for this entry
    ///
    /// Like [`Vec::swap_remove`], the pair is removed by swapping it with
    /// the last element of the map and popping it off.
    /// **This perturbs the position of what used to be the last element!**
    ///
    /// Computes in **O(1)** time (average).
    pub fn swap_remove_entry(self) -> (K, V) {
        self.inner.swap_remove_entry()
    }

    /// Moves the position of the entry to a new index
    /// by shifting all other entries in-between.
    ///
    /// This is equivalent to [`OrderMap::move_index`]
    /// coming `from` the current [`.index()`][Self::index].
    ///
    /// * If `self.index() < to`, the other pairs will shift down while the targeted pair moves up.
    /// * If `self.index() > to`, the other pairs will shift up while the targeted pair moves down.
    ///
    /// ***Panics*** if `to` is out of bounds.
    ///
    /// Computes in **O(n)** time (average).
    #[track_caller]
    pub fn move_index(self, to: usize) {
        self.inner.move_index(to);
    }

    /// Swaps the position of entry with another.
    ///
    /// This is equivalent to [`OrderMap::swap_indices`]
    /// with the current [`.index()`][Self::index] as one of the two being swapped.
    ///
    /// ***Panics*** if the `other` index is out of bounds.
    ///
    /// Computes in **O(1)** time (average).
    #[track_caller]
    pub fn swap_indices(self, other: usize) {
        self.inner.swap_indices(other);
    }
}

/// A view into a vacant raw entry in an [`OrderMap`].
/// It is part of the [`RawEntryMut`] enum.
pub struct RawVacantEntryMut<'a, K, V, S> {
    inner: ix::RawVacantEntryMut<'a, K, V, S>,
}

impl<K, V, S> fmt::Debug for RawVacantEntryMut<'_, K, V, S> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("RawVacantEntryMut").finish_non_exhaustive()
    }
}

impl<'a, K, V, S> RawVacantEntryMut<'a, K, V, S> {
    /// Return the index where a key-value pair may be inserted.
    pub fn index(&self) -> usize {
        self.inner.index()
    }

    /// Inserts the given key and value into the map,
    /// and returns mutable references to them.
    pub fn insert(self, key: K, value: V) -> (&'a mut K, &'a mut V)
    where
        K: Hash,
        S: BuildHasher,
    {
        self.inner.insert(key, value)
    }

    /// Inserts the given key and value into the map with the provided hash,
    /// and returns mutable references to them.
    pub fn insert_hashed_nocheck(self, hash: u64, key: K, value: V) -> (&'a mut K, &'a mut V) {
        self.inner.insert_hashed_nocheck(hash, key, value)
    }

    /// Inserts the given key and value into the map at the given index,
    /// shifting others to the right, and returns mutable references to them.
    ///
    /// ***Panics*** if `index` is out of bounds.
    ///
    /// Computes in **O(n)** time (average).
    #[track_caller]
    pub fn shift_insert(self, index: usize, key: K, value: V) -> (&'a mut K, &'a mut V)
    where
        K: Hash,
        S: BuildHasher,
    {
        self.inner.shift_insert(index, key, value)
    }

    /// Inserts the given key and value into the map with the provided hash
    /// at the given index, and returns mutable references to them.
    ///
    /// ***Panics*** if `index` is out of bounds.
    ///
    /// Computes in **O(n)** time (average).
    #[track_caller]
    pub fn shift_insert_hashed_nocheck(
        self,
        index: usize,
        hash: u64,
        key: K,
        value: V,
    ) -> (&'a mut K, &'a mut V) {
        self.inner
            .shift_insert_hashed_nocheck(index, hash, key, value)
    }
}

mod private {
    pub trait Sealed {}

    impl<K, V, S> Sealed for super::OrderMap<K, V, S> {}
}