http_types/
extensions.rs

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1// Implementation is based on
2// - https://github.com/hyperium/http/blob/master/src/extensions.rs
3// - https://github.com/kardeiz/type-map/blob/master/src/lib.rs
4
5use std::any::{Any, TypeId};
6use std::collections::HashMap;
7use std::fmt;
8use std::hash::{BuildHasherDefault, Hasher};
9
10/// A type to store extra data inside `Request` and `Response`.
11///
12/// Store and retrieve values by
13/// [`TypeId`](https://doc.rust-lang.org/std/any/struct.TypeId.html). This allows
14/// storing arbitrary data that implements `Sync + Send + 'static`. This is
15/// useful when for example implementing middleware that needs to send values.
16#[derive(Default)]
17pub struct Extensions {
18    map: Option<HashMap<TypeId, Box<dyn Any + Send + Sync>, BuildHasherDefault<IdHasher>>>,
19}
20
21impl Extensions {
22    /// Create an empty `Extensions`.
23    #[inline]
24    pub(crate) fn new() -> Self {
25        Self { map: None }
26    }
27
28    /// Insert a value into this `Extensions`.
29    ///
30    /// If a value of this type already exists, it will be returned.
31    pub fn insert<T: Send + Sync + 'static>(&mut self, val: T) -> Option<T> {
32        self.map
33            .get_or_insert_with(Default::default)
34            .insert(TypeId::of::<T>(), Box::new(val))
35            .and_then(|boxed| (boxed as Box<dyn Any>).downcast().ok().map(|boxed| *boxed))
36    }
37
38    /// Check if container contains value for type
39    pub fn contains<T: 'static>(&self) -> bool {
40        self.map
41            .as_ref()
42            .and_then(|m| m.get(&TypeId::of::<T>()))
43            .is_some()
44    }
45
46    /// Get a reference to a value previously inserted on this `Extensions`.
47    pub fn get<T: 'static>(&self) -> Option<&T> {
48        self.map
49            .as_ref()
50            .and_then(|m| m.get(&TypeId::of::<T>()))
51            .and_then(|boxed| (&**boxed as &(dyn Any)).downcast_ref())
52    }
53
54    /// Get a mutable reference to a value previously inserted on this `Extensions`.
55    pub fn get_mut<T: 'static>(&mut self) -> Option<&mut T> {
56        self.map
57            .as_mut()
58            .and_then(|m| m.get_mut(&TypeId::of::<T>()))
59            .and_then(|boxed| (&mut **boxed as &mut (dyn Any)).downcast_mut())
60    }
61
62    /// Remove a value from this `Extensions`.
63    ///
64    /// If a value of this type exists, it will be returned.
65    pub fn remove<T: 'static>(&mut self) -> Option<T> {
66        self.map
67            .as_mut()
68            .and_then(|m| m.remove(&TypeId::of::<T>()))
69            .and_then(|boxed| (boxed as Box<dyn Any>).downcast().ok().map(|boxed| *boxed))
70    }
71
72    /// Clear the `Extensions` of all inserted values.
73    #[inline]
74    pub fn clear(&mut self) {
75        self.map = None;
76    }
77}
78
79impl fmt::Debug for Extensions {
80    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
81        f.debug_struct("Extensions").finish()
82    }
83}
84
85// With TypeIds as keys, there's no need to hash them. So we simply use an identy hasher.
86#[derive(Default)]
87struct IdHasher(u64);
88
89impl Hasher for IdHasher {
90    fn write(&mut self, _: &[u8]) {
91        unreachable!("TypeId calls write_u64");
92    }
93
94    #[inline]
95    fn write_u64(&mut self, id: u64) {
96        self.0 = id;
97    }
98
99    #[inline]
100    fn finish(&self) -> u64 {
101        self.0
102    }
103}
104
105#[cfg(test)]
106mod tests {
107    use super::*;
108    #[test]
109    fn test_extensions() {
110        #[derive(Debug, PartialEq)]
111        struct MyType(i32);
112
113        let mut map = Extensions::new();
114
115        map.insert(5i32);
116        map.insert(MyType(10));
117
118        assert_eq!(map.get(), Some(&5i32));
119        assert_eq!(map.get_mut(), Some(&mut 5i32));
120
121        assert_eq!(map.remove::<i32>(), Some(5i32));
122        assert!(map.get::<i32>().is_none());
123
124        assert_eq!(map.get::<bool>(), None);
125        assert_eq!(map.get(), Some(&MyType(10)));
126    }
127}
http_types/extensions.rs

http_types/
extensions.rs
