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AcceptEncoding.preference() prefers brotli > zstd > gzip

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This commit is contained in:
Amit Upadhyay 2023-11-15 13:39:09 +05:30
parent e50bceb914
commit e5ed406af6
1 changed files with 22 additions and 3 deletions
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25
actix-web/src/http/header/accept_encoding.rs
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@ -149,7 +149,7 @@ impl AcceptEncoding {
/// Extracts the most preferable encoding, accounting for [q-factor weighting].
///
/// If no q-factors are provided, the first encoding is chosen. Note that items without
/// If no q-factors are provided, we prefer brotli > zstd > gzip. Note that items without
/// q-factors are given the maximum preference value.
///
/// As per the spec, returns [`Preference::Any`] if acceptable list is empty. Though, if this is
@ -167,16 +167,19 @@ impl AcceptEncoding {
let mut max_item = None;
let mut max_pref = Quality::ZERO;
let mut max_rank = 0;
// uses manual max lookup loop since we want the first occurrence in the case of same
// preference but `Iterator::max_by_key` would give us the last occurrence
for pref in &self.0 {
// only change if strictly greater
// equal items, even while unsorted, still have higher preference if they appear first
if pref.quality > max_pref {
let rank = encoding_rank(&pref);
if pref.quality > max_pref || (pref.quality == max_pref && max_rank < rank) {
max_pref = pref.quality;
max_item = Some(pref.item.clone());
max_rank = rank;
}
}
@ -203,6 +206,8 @@ impl AcceptEncoding {
/// Returns a sorted list of encodings from highest to lowest precedence, accounting
/// for [q-factor weighting].
///
/// If no q-factors are provided, we prefer brotli > zstd > gzip.
///
/// [q-factor weighting]: https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.2
pub fn ranked(&self) -> Vec<Preference<Encoding>> {
self.ranked_items().map(|q| q.item).collect()
@ -225,6 +230,17 @@ impl AcceptEncoding {
}
}
fn encoding_rank(q: &QualityItem<Preference<Encoding>>) -> u8 {
if q.quality == Quality::ZERO {
return 0;
}
match q.item {
Preference::Specific(Encoding::Known(ContentEncoding::Brotli)) => 2,
Preference::Specific(Encoding::Known(ContentEncoding::Zstd)) => 1,
_ => 0,
}
}
/// Returns true if "identity" is an acceptable encoding.
///
/// Internal algorithm relies on item list being in descending order of quality.
@ -420,5 +436,8 @@ mod tests {
let test = accept_encoding!("br", "gzip", "*");
assert_eq!(test.preference().unwrap(), enc("br"));
let test = accept_encoding!("gzip", "br", "*");
assert_eq!(test.preference().unwrap(), enc("br"));
}
}