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>>;
// With TypeIds as keys, there's no need to hash them. They are already hashes
// themselves, coming from the compiler. The IdHasher just holds the u64 of
// the TypeId, and then returns it, instead of doing any bit fiddling.
#[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
}
}
/// A type map of protocol extensions.
///
/// `Extensions` can be used by `Request` and `Response` to store
/// extra data derived from the underlying protocol.
#[derive(Default)]
pub struct Extensions {
// If extensions are never used, no need to carry around an empty HashMap.
// That's 3 words. Instead, this is only 1 word.
map: Option<Box<AnyMap>>,
}
impl Extensions {
/// Create an empty `Extensions`.
#[inline]
pub fn new() -> Extensions {
Extensions { map: None }
}
/// Insert a type into this `Extensions`.
///
/// If a extension of this type already existed, it will
/// be returned.
///
/// # Example
///
/// ```
/// # use http::Extensions;
/// let mut ext = Extensions::new();
/// assert!(ext.insert(5i32).is_none());
/// assert!(ext.insert(4u8).is_none());
/// assert_eq!(ext.insert(9i32), Some(5i32));
/// ```
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)
})
}
/// Get a reference to a type previously inserted on this `Extensions`.
///
/// # Example
///
/// ```
/// # use http::Extensions;
/// let mut ext = Extensions::new();
/// assert!(ext.get::<i32>().is_none());
/// ext.insert(5i32);
///
/// assert_eq!(ext.get::<i32>(), Some(&5i32));
/// ```
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())
}
/// Get a mutable reference to a type previously inserted on this `Extensions`.
///
/// # Example
///
/// ```
/// # use http::Extensions;
/// let mut ext = Extensions::new();
/// ext.insert(String::from("Hello"));
/// ext.get_mut::<String>().unwrap().push_str(" World");
///
/// assert_eq!(ext.get::<String>().unwrap(), "Hello World");
/// ```
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())
}
/// Remove a type from this `Extensions`.
///
/// If a extension of this type existed, it will be returned.
///
/// # Example
///
/// ```
/// # use http::Extensions;
/// let mut ext = Extensions::new();
/// ext.insert(5i32);
/// assert_eq!(ext.remove::<i32>(), Some(5i32));
/// assert!(ext.get::<i32>().is_none());
/// ```
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)
})
}
/// Clear the `Extensions` of all inserted extensions.
///
/// # Example
///
/// ```
/// # use http::Extensions;
/// let mut ext = Extensions::new();
/// ext.insert(5i32);
/// ext.clear();
///
/// assert!(ext.get::<i32>().is_none());
/// ```
#[inline]
pub fn clear(&mut self) {
if let Some(ref mut map) = self.map {
map.clear();
}
}
/// Check whether the extension set is empty or not.
///
/// # Example
///
/// ```
/// # use http::Extensions;
/// let mut ext = Extensions::new();
/// assert!(ext.is_empty());
/// ext.insert(5i32);
/// assert!(!ext.is_empty());
/// ```
#[inline]
pub fn is_empty(&self) -> bool {
self.map
.as_ref()
.map_or(true, |map| map.is_empty())
}
/// Get the numer of extensions available.
///
/// # Example
///
/// ```
/// # use http::Extensions;
/// let mut ext = Extensions::new();
/// assert_eq!(ext.len(), 0);
/// ext.insert(5i32);
/// assert_eq!(ext.len(), 1);
/// ```
#[inline]
pub fn len(&self) -> usize {
self.map
.as_ref()
.map_or(0, |map| map.len())
}
/// Extends `self` with another `Extensions`.
///
/// If an instance of a specific type exists in both, the one in `self` is overwritten with the
/// one from `other`.
///
/// # Example
///
/// ```
/// # use http::Extensions;
/// let mut ext_a = Extensions::new();
/// ext_a.insert(8u8);
/// ext_a.insert(16u16);
///
/// let mut ext_b = Extensions::new();
/// ext_b.insert(4u8);
/// ext_b.insert("hello");
///
/// ext_a.extend(ext_b);
/// assert_eq!(ext_a.len(), 3);
/// assert_eq!(ext_a.get::<u8>(), Some(&4u8));
/// assert_eq!(ext_a.get::<u16>(), Some(&16u16));
/// assert_eq!(ext_a.get::<&'static str>().copied(), Some("hello"));
/// ```
pub fn extend(&mut self, other: Self) {
if let Some(other) = other.map {
if let Some(map) = &mut self.map {
map.extend(*other);
} else {
self.map = Some(other);
}
}
}
}
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)));
}
