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use std::any::{Any, TypeId};
use std::collections::HashMap;
use std::fmt;
use std::hash::{BuildHasherDefault, Hasher};
type AnyMap = HashMap<TypeId, Box<dyn Any + Send + Sync>, BuildHasherDefault<IdHasher>>;
#[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
}
}
#[derive(Default)]
pub struct Extensions {
map: Option<Box<AnyMap>>,
}
impl Extensions {
#[inline]
pub fn new() -> Extensions {
Extensions { map: None }
}
pub fn insert<T: Send + Sync + 'static>(&mut self, val: T) -> Option<T> {
self.map
.get_or_insert_with(|| Box::new(HashMap::default()))
.insert(TypeId::of::<T>(), Box::new(val))
.and_then(|boxed| {
(boxed as Box<dyn Any + 'static>)
.downcast()
.ok()
.map(|boxed| *boxed)
})
}
pub fn get<T: Send + Sync + 'static>(&self) -> Option<&T> {
self.map
.as_ref()
.and_then(|map| map.get(&TypeId::of::<T>()))
.and_then(|boxed| (&**boxed as &(dyn Any + 'static)).downcast_ref())
}
pub fn get_mut<T: Send + Sync + 'static>(&mut self) -> Option<&mut T> {
self.map
.as_mut()
.and_then(|map| map.get_mut(&TypeId::of::<T>()))
.and_then(|boxed| (&mut **boxed as &mut (dyn Any + 'static)).downcast_mut())
}
pub fn remove<T: Send + Sync + 'static>(&mut self) -> Option<T> {
self.map
.as_mut()
.and_then(|map| map.remove(&TypeId::of::<T>()))
.and_then(|boxed| {
(boxed as Box<dyn Any + 'static>)
.downcast()
.ok()
.map(|boxed| *boxed)
})
}
#[inline]
pub fn clear(&mut self) {
if let Some(ref mut map) = self.map {
map.clear();
}
}
}
impl fmt::Debug for Extensions {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Extensions").finish()
}
}
#[test]
fn test_extensions() {
#[derive(Debug, PartialEq)]
struct MyType(i32);
let mut extensions = Extensions::new();
extensions.insert(5i32);
extensions.insert(MyType(10));
assert_eq!(extensions.get(), Some(&5i32));
assert_eq!(extensions.get_mut(), Some(&mut 5i32));
assert_eq!(extensions.remove::<i32>(), Some(5i32));
assert!(extensions.get::<i32>().is_none());
assert_eq!(extensions.get::<bool>(), None);
assert_eq!(extensions.get(), Some(&MyType(10)));
}