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Optimize replace_headers to avoid copies of keys

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Sometimes, I'm amazed at what non lexical lifetimes allows.
This commit is contained in:
Zachary Dremann
2021-08-28 11:58:43 -04:00
committed by Sean McArthur
parent 2881354c90
commit 2767071cac
1 changed files with 15 additions and 13 deletions
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28
src/util.rs
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@@ -1,4 +1,4 @@
use crate::header::HeaderMap; use crate::header::{Entry, HeaderMap, OccupiedEntry};
// xor-shift // xor-shift
#[cfg(not(target_arch = "wasm32"))] #[cfg(not(target_arch = "wasm32"))]
@@ -42,21 +42,23 @@ pub(crate) fn replace_headers(dst: &mut HeaderMap, src: HeaderMap) {
// The first time a name is yielded, it will be Some(name), and if // The first time a name is yielded, it will be Some(name), and if
// there are more values with the same name, the next yield will be // there are more values with the same name, the next yield will be
// None. // None.
//
// TODO: a complex exercise would be to optimize this to only
// require 1 hash/lookup of the key, but doing something fancy
// with header::Entry...
let mut prev_name = None; let mut prev_entry: Option<OccupiedEntry<_>> = None;
for (key, value) in src { for (key, value) in src {
match key { match key {
Some(key) => { Some(key) => match dst.entry(key) {
dst.insert(key.clone(), value); Entry::Occupied(mut e) => {
prev_name = Some(key); e.insert(value);
} prev_entry = Some(e);
None => match prev_name { }
Some(ref key) => { Entry::Vacant(e) => {
dst.append(key.clone(), value); let e = e.insert_entry(value);
prev_entry = Some(e);
}
},
None => match prev_entry {
Some(ref mut entry) => {
entry.append(value);
} }
None => unreachable!("HeaderMap::into_iter yielded None first"), None => unreachable!("HeaderMap::into_iter yielded None first"),
}, },