Optimize Name parsing by using a pair of TinyVec

The previous implementation used Rc to represent Label, then composed
those in an array to represent Name. That produced a large number of
small allocations in the parsing code path. This new implementation
avoids allocations entirely for small names, and unless the name has a
very large number of labels, it is stored entirely in one allocation.

This also removes the Index impl for Name. Since we no longer contain
any Labels, we cannot implement that (a common problem with Index leaking
implementation details).

crates/client/src/rr/lower_name.rs

@@ -11,14 +11,13 @@ use std::borrow::Borrow;
 use std::cmp::{Ordering, PartialEq};
 use std::fmt;
 use std::hash::{Hash, Hasher};
-use std::ops::Index;
 use std::str::FromStr;
 
 use crate::proto::error::*;
 #[cfg(feature = "serde-config")]
 use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
 
-use crate::rr::{Label, Name};
+use crate::rr::Name;
 use crate::serialize::binary::*;
 
 ///  them should be through references. As a workaround the Strings are all Rc as well as the array
@@ -191,14 +190,6 @@ impl fmt::Display for LowerName {
     }
 }
 
-impl Index<usize> for LowerName {
-    type Output = Label;
-
-    fn index(&self, _index: usize) -> &Label {
-        &(self.0[_index])
-    }
-}
-
 impl PartialOrd<LowerName> for LowerName {
     fn partial_cmp(&self, other: &LowerName) -> Option<Ordering> {
         Some(self.cmp(other))

crates/proto/Cargo.toml

@@ -78,6 +78,7 @@ serde = { version = "1.0", features = ["derive"], optional = true }
 smallvec = "1.6"
 socket2 = { version = "0.3.16", optional = true }
 thiserror = "1.0.20"
+tinyvec = { version = "1.1.1", features = ["alloc"] }
 tokio = { version = "1.0", optional = true }
 url = "2.1.0"
 wasm-bindgen-crate = { version = "0.2.58", optional = true, package = "wasm-bindgen" }

crates/proto/src/rr/domain/label.rs

@@ -17,7 +17,7 @@ use std::borrow::Borrow;
 use std::cmp::{Ordering, PartialEq};
 use std::fmt::{self, Debug, Display, Formatter, Write};
 use std::hash::{Hash, Hasher};
-use std::sync::Arc as Rc;
+use tinyvec::TinyVec;
 
 use idna;
 use log::debug;
@@ -29,7 +29,7 @@ const IDNA_PREFIX: &[u8] = b"xn--";
 
 /// Labels are always stored as ASCII, unicode characters must be encoded with punycode
 #[derive(Clone, Eq)]
-pub struct Label(Rc<[u8]>);
+pub struct Label(TinyVec<[u8; 24]>);
 
 impl Label {
     /// These must only be ASCII, with unicode encoded to PunyCode, or other such transformation.
@@ -40,7 +40,7 @@ impl Label {
         if bytes.len() > 63 {
             return Err(format!("Label exceeds maximum length 63: {}", bytes.len()).into());
         };
-        Ok(Label(Rc::from(bytes)))
+        Ok(Label(TinyVec::from(bytes)))
     }
 
     /// Translates this string into IDNA safe name, encoding to punycode as necessary.
@@ -86,7 +86,7 @@ impl Label {
 
     /// Returns a new Label of the Wildcard, i.e. "*"
     pub fn wildcard() -> Self {
-        Label(Rc::from(WILDCARD.to_vec()))
+        Label(TinyVec::from(WILDCARD))
     }
 
     /// Converts this label to lowercase
@@ -100,7 +100,7 @@ impl Label {
         {
             let mut lower_label: Vec<u8> = self.0.to_vec();
             lower_label[idx..].make_ascii_lowercase();
-            Label(Rc::from(lower_label))
+            Label(TinyVec::from(lower_label.as_slice()))
         } else {
             self.clone()
         }
@@ -201,7 +201,7 @@ impl Label {
 
 impl AsRef<[u8]> for Label {
     fn as_ref(&self) -> &[u8] {
-        &self.0
+        self.as_bytes()
     }
 }