address bad usage of TST

benchmarks/core/parse-headers.mjs

@@ -79,6 +79,16 @@ const headersIrregular = Array.from(
     .map((c) => Buffer.from(c.toUpperCase()))
 )
 
+// wellknownHeaderName[wellknownHeaderNames.length-1] is the worst case
+// but Via is more pathological, we need around 20 times to reach Via,
+// if we insert wellknownHeaderNames to the TST in order while it is only
+// 3 characters long
+const worstCaseIfInsertInOrderToTST = Object.entries({
+  Via: '1.1 vegur'
+})
+  .flat()
+  .map((c) => Buffer.from(c))
+
 // avoid JIT bias
 bench('noop', () => {})
 bench('noop', () => {})
@@ -98,6 +108,11 @@ group('parseHeaders', () => {
       parseHeaders(headersIrregular[i])
     }
   })
+  bench('worstCaseIfInsertInOrderToTST', () => {
+    for (let i = 0; i < 1e4; i++) {
+      parseHeaders(worstCaseIfInsertInOrderToTST)
+    }
+  })
 })
 
 await new Promise((resolve) => setTimeout(resolve, 7000))

lib/core/tree.js

@@ -149,8 +149,18 @@ class TernarySearchTree {
 
 const tree = new TernarySearchTree()
 
-for (let i = 0; i < wellknownHeaderNames.length; ++i) {
-  const key = headerNameLowerCasedRecord[wellknownHeaderNames[i]]
+function shuffleArray (arr) {
+  for (let i = arr.length - 1; i > 0; i--) {
+    const j = Math.floor(Math.random() * (i + 1));
+    [arr[i], arr[j]] = [arr[j], arr[i]]
+  }
+  return arr
+}
+const randomIndexOfWellknownHeaderNames =
+  shuffleArray(wellknownHeaderNames.map((v, idx) => idx))
+
+for (const randomIndex of randomIndexOfWellknownHeaderNames) {
+  const key = headerNameLowerCasedRecord[wellknownHeaderNames[randomIndex]]
   tree.insert(key, key)
 }