port Extensions from http crate #315

src/extensions.rs

@@ -0,0 +1,90 @@
+use std::any::{Any, TypeId};
+use std::collections::HashMap;
+use std::fmt;
+use std::hash::BuildHasherDefault;
+
+use fnv::FnvHasher;
+
+type AnyMap = HashMap<TypeId, Box<Any>, BuildHasherDefault<FnvHasher>>;
+
+/// A type map of request extensions.
+pub struct Extensions {
+    map: AnyMap,
+}
+
+impl Extensions {
+    /// Create an empty `Extensions`.
+    #[inline]
+    pub(crate) fn new() -> Extensions {
+        Extensions {
+            map: HashMap::default(),
+        }
+    }
+
+    /// Insert a type into this `Extensions`.
+    ///
+    /// If a extension of this type already existed, it will
+    /// be returned.
+    pub fn insert<T: 'static>(&mut self, val: T) {
+        self.map.insert(TypeId::of::<T>(), Box::new(val));
+    }
+
+    /// Get a reference to a type previously inserted on this `Extensions`.
+    pub fn get<T: 'static>(&self) -> Option<&T> {
+        self.map
+            .get(&TypeId::of::<T>())
+            .and_then(|boxed| (&**boxed as &(Any + 'static)).downcast_ref())
+    }
+
+    /// Get a mutable reference to a type previously inserted on this `Extensions`.
+    pub fn get_mut<T: 'static>(&mut self) -> Option<&mut T> {
+        self.map
+            .get_mut(&TypeId::of::<T>())
+            .and_then(|boxed| (&mut **boxed as &mut (Any + 'static)).downcast_mut())
+    }
+
+    /// Remove a type from this `Extensions`.
+    ///
+    /// If a extension of this type existed, it will be returned.
+    pub fn remove<T: 'static>(&mut self) -> Option<T> {
+        self.map.remove(&TypeId::of::<T>()).and_then(|boxed| {
+            //TODO: we can use unsafe and remove double checking the type id
+            (boxed as Box<Any + 'static>)
+                .downcast()
+                .ok()
+                .map(|boxed| *boxed)
+        })
+    }
+
+    /// Clear the `Extensions` of all inserted extensions.
+    #[inline]
+    pub fn clear(&mut self) {
+        self.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)));
+}