109 lines
2.8 KiB
Rust
109 lines
2.8 KiB
Rust
//! This module defines a `DynMap` -- a container for heterogeneous maps.
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//!
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//! This means that `DynMap` stores a bunch of hash maps inside, and those maps
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//! can be of different types.
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//!
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//! It is used like this:
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//!
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//! ```
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//! // keys define submaps of a `DynMap`
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//! const STRING_TO_U32: Key<String, u32> = Key::new();
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//! const U32_TO_VEC: Key<u32, Vec<bool>> = Key::new();
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//!
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//! // Note: concrete type, no type params!
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//! let mut map = DynMap::new();
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//!
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//! // To access a specific map, index the `DynMap` by `Key`:
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//! map[STRING_TO_U32].insert("hello".to_string(), 92);
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//! let value = map[U32_TO_VEC].get(92);
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//! assert!(value.is_none());
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//! ```
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//!
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//! This is a work of fiction. Any similarities to Kotlin's `BindingContext` are
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//! a coincidence.
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use std::{
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hash::Hash,
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marker::PhantomData,
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ops::{Index, IndexMut},
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};
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use anymap::Map;
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use rustc_hash::FxHashMap;
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pub struct Key<K, V, P = (K, V)> {
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_phantom: PhantomData<(K, V, P)>,
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}
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impl<K, V, P> Key<K, V, P> {
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pub(crate) const fn new() -> Key<K, V, P> {
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Key { _phantom: PhantomData }
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}
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}
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impl<K, V, P> Copy for Key<K, V, P> {}
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impl<K, V, P> Clone for Key<K, V, P> {
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fn clone(&self) -> Key<K, V, P> {
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*self
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}
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}
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pub trait Policy {
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type K;
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type V;
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fn insert(map: &mut DynMap, key: Self::K, value: Self::V);
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fn get<'a>(map: &'a DynMap, key: &Self::K) -> Option<&'a Self::V>;
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}
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impl<K: Hash + Eq + 'static, V: 'static> Policy for (K, V) {
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type K = K;
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type V = V;
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fn insert(map: &mut DynMap, key: K, value: V) {
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map.map.entry::<FxHashMap<K, V>>().or_insert_with(Default::default).insert(key, value);
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}
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fn get<'a>(map: &'a DynMap, key: &K) -> Option<&'a V> {
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map.map.get::<FxHashMap<K, V>>()?.get(key)
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}
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}
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pub struct DynMap {
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pub(crate) map: Map,
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}
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impl Default for DynMap {
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fn default() -> Self {
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DynMap { map: Map::new() }
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}
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}
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#[repr(transparent)]
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pub struct KeyMap<KEY> {
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map: DynMap,
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_phantom: PhantomData<KEY>,
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}
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impl<P: Policy> KeyMap<Key<P::K, P::V, P>> {
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pub fn insert(&mut self, key: P::K, value: P::V) {
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P::insert(&mut self.map, key, value)
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}
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pub fn get(&self, key: &P::K) -> Option<&P::V> {
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P::get(&self.map, key)
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}
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}
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impl<P: Policy> Index<Key<P::K, P::V, P>> for DynMap {
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type Output = KeyMap<Key<P::K, P::V, P>>;
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fn index(&self, _key: Key<P::K, P::V, P>) -> &Self::Output {
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// Safe due to `#[repr(transparent)]`.
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unsafe { std::mem::transmute::<&DynMap, &KeyMap<Key<P::K, P::V, P>>>(self) }
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}
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}
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impl<P: Policy> IndexMut<Key<P::K, P::V, P>> for DynMap {
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fn index_mut(&mut self, _key: Key<P::K, P::V, P>) -> &mut Self::Output {
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// Safe due to `#[repr(transparent)]`.
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unsafe { std::mem::transmute::<&mut DynMap, &mut KeyMap<Key<P::K, P::V, P>>>(self) }
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}
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}
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