// Implementation is based on
// - https://github.com/hyperium/http/blob/master/src/extensions.rs
// - https://github.com/kardeiz/type-map/blob/master/src/lib.rs
use std::any::{Any, TypeId};
use std::collections::HashMap;
use std::fmt;
use std::hash::{BuildHasherDefault, Hasher};
/// A type to store extra data inside `Request` and `Response`.
///
/// Store and retrieve values by
/// [`TypeId`](https://doc.rust-lang.org/std/any/struct.TypeId.html). This allows
/// storing arbitrary data that implements `Sync + Send + 'static`. This is
/// useful when for example implementing middleware that needs to send values.
#[derive(Default)]
pub struct Extensions {
map: Option<HashMap<TypeId, Box<dyn Any + Send + Sync>, BuildHasherDefault<IdHasher>>>,
}
impl Extensions {
/// Create an empty `Extensions`.
#[inline]
pub(crate) fn new() -> Self {
Self { map: None }
}
/// Insert a value into this `Extensions`.
///
/// If a value of this type already exists, it will be returned.
pub fn insert<T: Send + Sync + 'static>(&mut self, val: T) -> Option<T> {
self.map
.get_or_insert_with(Default::default)
.insert(TypeId::of::<T>(), Box::new(val))
.and_then(|boxed| (boxed as Box<dyn Any>).downcast().ok().map(|boxed| *boxed))
}
/// Check if container contains value for type
pub fn contains<T: 'static>(&self) -> bool {
self.map
.as_ref()
.and_then(|m| m.get(&TypeId::of::<T>()))
.is_some()
}
/// Get a reference to a value previously inserted on this `Extensions`.
pub fn get<T: 'static>(&self) -> Option<&T> {
self.map
.as_ref()
.and_then(|m| m.get(&TypeId::of::<T>()))
.and_then(|boxed| (&**boxed as &(dyn Any)).downcast_ref())
}
/// Get a mutable reference to a value previously inserted on this `Extensions`.
pub fn get_mut<T: 'static>(&mut self) -> Option<&mut T> {
self.map
.as_mut()
.and_then(|m| m.get_mut(&TypeId::of::<T>()))
.and_then(|boxed| (&mut **boxed as &mut (dyn Any)).downcast_mut())
}
/// Remove a value from this `Extensions`.
///
/// If a value of this type exists, it will be returned.
pub fn remove<T: 'static>(&mut self) -> Option<T> {
self.map
.as_mut()
.and_then(|m| m.remove(&TypeId::of::<T>()))
.and_then(|boxed| (boxed as Box<dyn Any>).downcast().ok().map(|boxed| *boxed))
}
/// Clear the `Extensions` of all inserted values.
#[inline]
pub fn clear(&mut self) {
self.map = None;
}
}
impl fmt::Debug for Extensions {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Extensions").finish()
}
}
// With TypeIds as keys, there's no need to hash them. So we simply use an identy hasher.
#[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 = Extensions::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.remove::<i32>(), Some(5i32));
assert!(map.get::<i32>().is_none());
assert_eq!(map.get::<bool>(), None);
assert_eq!(map.get(), Some(&MyType(10)));
}
}