perf(headers): Improve Headers

lib/fetch/headers.js

@@ -16,6 +16,21 @@ const assert = require('assert')
 const kHeadersMap = Symbol('headers map')
 const kHeadersSortedMap = Symbol('headers map sorted')
 
+/**
+ * @param {number} code
+ */
+function isHTTPWhiteSpaceCharCode (code) {
+  switch (code) {
+    case 0x00a:
+    case 0x00d:
+    case 0x009:
+    case 0x020:
+      return true
+    default:
+      return false
+  }
+}
+
 /**
  * @see https://fetch.spec.whatwg.org/#concept-header-value-normalize
  * @param {string} potentialValue
@@ -24,12 +39,12 @@ function headerValueNormalize (potentialValue) {
   //  To normalize a byte sequence potentialValue, remove
   //  any leading and trailing HTTP whitespace bytes from
   //  potentialValue.
+  let i = 0; let j = potentialValue.length
+
+  while (j > i && isHTTPWhiteSpaceCharCode(potentialValue.charCodeAt(j - 1))) --j
+  while (i > j && isHTTPWhiteSpaceCharCode(potentialValue.charCodeAt(i))) ++i
 
-  // Trimming the end with `.replace()` and a RegExp is typically subject to
-  // ReDoS. This is safer and faster.
-  let i = potentialValue.length
-  while (/[\r\n\t ]/.test(potentialValue.charAt(--i)));
-  return potentialValue.slice(0, i + 1).replace(/^[\r\n\t ]+/, '')
+  return i === 0 && j === potentialValue.length ? potentialValue : potentialValue.slice(i, j)
 }
 
 function fill (headers, object) {
@@ -38,7 +53,8 @@ function fill (headers, object) {
   // 1. If object is a sequence, then for each header in object:
   // Note: webidl conversion to array has already been done.
   if (Array.isArray(object)) {
-    for (const header of object) {
+    for (let i = 0; i < object.length; i++) {
+      const header = object[i]
       // 1. If header does not contain exactly two items, then throw a TypeError.
       if (header.length !== 2) {
         throw webidl.errors.exception({
@@ -55,8 +71,10 @@ function fill (headers, object) {
 
     // 2. Otherwise, object is a record, then for each key → value in object,
     //    append (key, value) to headers
-    for (const [key, value] of Object.entries(object)) {
-      headers.append(key, value)
+    const keys = Object.keys(object)
+    for (let i = 0; i < keys.length; i++) {
+      const key = keys[i]
+      headers.append(key, object[key])
     }
   } else {
     throw webidl.errors.conversionFailed({
@@ -422,16 +440,17 @@ class Headers {
     const cookies = this[kHeadersList].cookies
 
     // 3. For each name of names:
-    for (const [name, value] of names) {
+    for (let i = 0; i < names.length; i++) {
+      const [name, value] = names[i]
       // 1. If name is `set-cookie`, then:
       if (name === 'set-cookie') {
         // 1. Let values be a list of all values of headers in list whose name
         //    is a byte-case-insensitive match for name, in order.
 
         // 2. For each value of values:
         // 1. Append (name, value) to headers.
-        for (const value of cookies) {
-          headers.push([name, value])
+        for (let j = 0; j < cookies.length; j++) {
+          headers.push([name, cookies[j]])
         }
       } else {
         // 2. Otherwise:

lib/fetch/webidl.js

@@ -399,6 +399,11 @@ webidl.nullableConverter = function (converter) {
 
 // https://webidl.spec.whatwg.org/#es-DOMString
 webidl.converters.DOMString = function (V, opts = {}) {
+  // Note: avoid re-stringify
+  if (typeof V === 'string') {
+    return V
+  }
+
   // 1. If V is null and the conversion is to an IDL type
   //    associated with the [LegacyNullToEmptyString]
   //    extended attribute, then return the DOMString value
@@ -427,12 +432,10 @@ webidl.converters.ByteString = function (V) {
   // 2. If the value of any element of x is greater than
   //    255, then throw a TypeError.
   for (let index = 0; index < x.length; index++) {
-    const charCode = x.charCodeAt(index)
-
-    if (charCode > 255) {
+    if (x.charCodeAt(index) > 255) {
       throw new TypeError(
         'Cannot convert argument to a ByteString because the character at ' +
-        `index ${index} has a value of ${charCode} which is greater than 255.`
+        `index ${index} has a value of ${x.charCodeAt(index)} which is greater than 255.`
       )
     }
   }