1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
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();
        }
    }
}

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)));
}