1 files changed, 88 insertions, 0 deletions
diff --git a/third_party/rust/headers/src/map_ext.rs b/third_party/rust/headers/src/map_ext.rs
new file mode 100644
index 0000000000..e80ccda9e3
--- /dev/null
+++ b/third_party/rust/headers/src/map_ext.rs
@@ -0,0 +1,88 @@
+use super::{Error, Header, HeaderValue};
+use http;
+
+/// An extension trait adding "typed" methods to `http::HeaderMap`.
+pub trait HeaderMapExt: self::sealed::Sealed {
+    /// Inserts the typed `Header` into this `HeaderMap`.
+    fn typed_insert<H>(&mut self, header: H)
+    where
+        H: Header;
+
+    /// Tries to find the header by name, and then decode it into `H`.
+    fn typed_get<H>(&self) -> Option<H>
+    where
+        H: Header;
+
+    /// Tries to find the header by name, and then decode it into `H`.
+    fn typed_try_get<H>(&self) -> Result<Option<H>, Error>
+    where
+        H: Header;
+}
+
+impl HeaderMapExt for http::HeaderMap {
+    fn typed_insert<H>(&mut self, header: H)
+    where
+        H: Header,
+    {
+        let entry = self.entry(H::name());
+        let mut values = ToValues {
+            state: State::First(entry),
+        };
+        header.encode(&mut values);
+    }
+
+    fn typed_get<H>(&self) -> Option<H>
+    where
+        H: Header,
+    {
+        HeaderMapExt::typed_try_get(self).unwrap_or(None)
+    }
+
+    fn typed_try_get<H>(&self) -> Result<Option<H>, Error>
+    where
+        H: Header,
+    {
+        let mut values = self.get_all(H::name()).iter();
+        if values.size_hint() == (0, Some(0)) {
+            Ok(None)
+        } else {
+            H::decode(&mut values).map(Some)
+        }
+    }
+}
+
+struct ToValues<'a> {
+    state: State<'a>,
+}
+
+#[derive(Debug)]
+enum State<'a> {
+    First(http::header::Entry<'a, HeaderValue>),
+    Latter(http::header::OccupiedEntry<'a, HeaderValue>),
+    Tmp,
+}
+
+impl<'a> Extend<HeaderValue> for ToValues<'a> {
+    fn extend<T: IntoIterator<Item = HeaderValue>>(&mut self, iter: T) {
+        for value in iter {
+            let entry = match ::std::mem::replace(&mut self.state, State::Tmp) {
+                State::First(http::header::Entry::Occupied(mut e)) => {
+                    e.insert(value);
+                    e
+                }
+                State::First(http::header::Entry::Vacant(e)) => e.insert_entry(value),
+                State::Latter(mut e) => {
+                    e.append(value);
+                    e
+                }
+                State::Tmp => unreachable!("ToValues State::Tmp"),
+            };
+            self.state = State::Latter(entry);
+        }
+    }
+}
+
+mod sealed {
+    pub trait Sealed {}
+    impl Sealed for ::http::HeaderMap {}
+}