use hashbrown::HashMap;
use std::{
any::{Any, TypeId},
fmt,
hash::{BuildHasherDefault, Hasher},
};
#[derive(Default)]
pub struct StateSet(HashMap<TypeId, Box<dyn Any + Send + Sync>, BuildHasherDefault<IdHasher>>);
impl StateSet {
pub fn new() -> Self {
Self::default()
}
pub fn insert<T: Send + Sync + 'static>(&mut self, val: T) -> Option<T> {
self.0
.insert(TypeId::of::<T>(), Box::new(val))
.and_then(|boxed| (boxed as Box<dyn Any>).downcast().ok().map(|boxed| *boxed))
}
pub fn contains<T: 'static>(&self) -> bool {
self.0.get(&TypeId::of::<T>()).is_some()
}
pub fn get<T: 'static>(&self) -> Option<&T> {
self.0
.get(&TypeId::of::<T>())
.and_then(|boxed| (&**boxed as &(dyn Any)).downcast_ref())
}
pub fn get_mut<T: 'static>(&mut self) -> Option<&mut T> {
self.0
.get_mut(&TypeId::of::<T>())
.and_then(|boxed| (&mut **boxed as &mut (dyn Any)).downcast_mut())
}
pub fn take<T: 'static>(&mut self) -> Option<T> {
self.0
.remove(&TypeId::of::<T>())
.and_then(|boxed| (boxed as Box<dyn Any>).downcast().ok().map(|boxed| *boxed))
}
#[allow(clippy::missing_panics_doc)]
pub fn get_or_insert<T: Send + Sync + 'static>(&mut self, default: T) -> &mut T {
self.0
.entry(TypeId::of::<T>())
.or_insert_with(|| Box::new(default))
.downcast_mut()
.expect("StateSet maintains the invariant the value associated with a given TypeId is always the type associated with that TypeId.")
}
#[allow(clippy::missing_panics_doc)]
pub fn get_or_insert_with<F, T>(&mut self, default: F) -> &mut T
where
F: FnOnce() -> T,
T: Send + Sync + 'static,
{
self.0
.entry(TypeId::of::<T>())
.or_insert_with(|| Box::new(default()))
.downcast_mut()
.expect("StateSet maintains the invariant the value associated with a given TypeId is always the type associated with that TypeId.")
}
}
impl fmt::Debug for StateSet {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("StateSet").finish()
}
}
#[derive(Default)]
struct IdHasher(u64);
impl Hasher for IdHasher {
fn write(&mut self, _: &[u8]) {
unreachable!("TypeId calls write_u64");
}
#[inline]
fn write_u64(&mut self, id: u64) {
self.0 = id;
}
#[inline]
fn finish(&self) -> u64 {
self.0
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_extensions() {
#[derive(Debug, PartialEq)]
struct MyType(i32);
let mut map = StateSet::new();
map.insert(5i32);
map.insert(MyType(10));
assert_eq!(map.get(), Some(&5i32));
assert_eq!(map.get_mut(), Some(&mut 5i32));
assert_eq!(map.take::<i32>(), Some(5i32));
assert!(map.get::<i32>().is_none());
assert_eq!(map.get::<bool>(), None);
assert_eq!(map.get(), Some(&MyType(10)));
}
}