AcceptEncoding: sort by weight

Author: yoshuawuyts

src/content/accept_encoding.rs

@@ -2,6 +2,7 @@
 
 use crate::content::EncodingProposal;
 use crate::headers::{HeaderName, HeaderValue, Headers, ToHeaderValues, ACCEPT_ENCODING};
+use crate::utils::sort_by_weight;
 
 use std::fmt::{self, Debug, Write};
 use std::option;
@@ -70,6 +71,11 @@ impl AcceptEncoding {
         self.wildcard = wildcard
     }
 
+    /// Sort the entries in-place.
+    pub fn sort(&mut self) {
+        sort_by_weight(&mut self.entries);
+    }
+
     /// Insert a `HeaderName` + `HeaderValue` pair into a `Headers` instance.
     pub fn apply(&self, mut headers: impl AsMut<Headers>) {
         headers.as_mut().insert(ACCEPT_ENCODING, self.value());
@@ -291,21 +297,18 @@ mod test {
     fn reorder_iter_based_on_weight() -> crate::Result<()> {
         let mut accept = AcceptEncoding::new();
         accept.push(EncodingProposal::new(Encoding::Gzip, Some(0.4))?);
+        accept.push(EncodingProposal::new(Encoding::Identity, None)?);
         accept.push(EncodingProposal::new(Encoding::Brotli, Some(0.8))?);
 
         let mut headers = Response::new(200);
         accept.apply(&mut headers);
 
-        let accept = AcceptEncoding::from_headers(headers)?.unwrap();
+        let mut accept = AcceptEncoding::from_headers(headers)?.unwrap();
+        accept.sort();
         let mut accept = accept.iter();
         assert_eq!(accept.next().unwrap(), Encoding::Brotli);
         assert_eq!(accept.next().unwrap(), Encoding::Gzip);
+        assert_eq!(accept.next().unwrap(), Encoding::Identity);
         Ok(())
     }
 }
-
-/// Order header proposals. In the case of two proposals of equal weight we pick
-/// the one that was declared last.
-fn sort_proposals<T: PartialOrd>(props: &mut Vec<T>) {
-    props.sort_unstable_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Less))
-}

src/content/encoding_proposal.rs

@@ -6,7 +6,7 @@ use crate::utils::parse_weight;
 use std::cmp::{Ordering, PartialEq};
 
 /// A proposed `Encoding` in `AcceptEncoding`.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 pub struct EncodingProposal {
     /// The proposed encoding.
     encoding: Encoding,

src/utils/mod.rs

@@ -4,6 +4,8 @@ pub(crate) use date::fmt_http_date;
 pub(crate) use date::parse_http_date;
 
 use crate::{Error, Status, StatusCode};
+
+use std::cmp::Ordering;
 use std::str::FromStr;
 
 /// Declares unstable items.
@@ -38,3 +40,14 @@ pub(crate) fn parse_weight(s: &str) -> crate::Result<f32> {
         }
     }
 }
+
+/// Order proposals by weight. Try ordering by q value first. If equal or undefined,
+/// order by index, favoring the latest provided value.
+pub(crate) fn sort_by_weight<T: PartialOrd + Copy>(props: &mut Vec<T>) {
+    let mut arr: Vec<(usize, T)> = props.iter().map(|t| *t).enumerate().collect();
+    arr.sort_unstable_by(|a, b| match b.1.partial_cmp(&a.1) {
+        None | Some(Ordering::Equal) => b.0.cmp(&a.0),
+        Some(ord @ _) => ord,
+    });
+    *props = arr.into_iter().map(|(_, t)| t).collect::<Vec<T>>();
+}