perf(headers): Improve Headers (#2397)

* perf(headers): Improve Headers

* perf: reduce variables in the for loop

* perf: use `===`

* perf: use `===`

* feat: Revert `avoid re-stringify`

* perf: use `substring`

* fix: fixing trimming issues

* perf: avoid two duplicate calls of `ByteString`.

* fix: comment position

lib/fetch/headers.js

@@ -16,6 +16,13 @@ const assert = require('assert')
 const kHeadersMap = Symbol('headers map')
 const kHeadersSortedMap = Symbol('headers map sorted')
 
+/**
+ * @param {number} code
+ */
+function isHTTPWhiteSpaceCharCode (code) {
+  return code === 0x00a || code === 0x00d || code === 0x009 || code === 0x020
+}
+
 /**
  * @see https://fetch.spec.whatwg.org/#concept-header-value-normalize
  * @param {string} potentialValue
@@ -24,12 +31,12 @@ 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 (j > i && 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.substring(i, j)
 }
 
 function fill (headers, object) {
@@ -38,7 +45,8 @@ 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({
@@ -48,15 +56,16 @@ function fill (headers, object) {
       }
 
       // 2. Append (header’s first item, header’s second item) to headers.
-      headers.append(header[0], header[1])
+      appendHeader(headers, header[0], header[1])
     }
   } else if (typeof object === 'object' && object !== null) {
     // Note: null should throw
 
     // 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) {
+      appendHeader(headers, keys[i], object[keys[i]])
     }
   } else {
     throw webidl.errors.conversionFailed({
@@ -67,6 +76,50 @@ function fill (headers, object) {
   }
 }
 
+/**
+ * @see https://fetch.spec.whatwg.org/#concept-headers-append
+ */
+function appendHeader (headers, name, value) {
+  // 1. Normalize value.
+  value = headerValueNormalize(value)
+
+  // 2. If name is not a header name or value is not a
+  //    header value, then throw a TypeError.
+  if (!isValidHeaderName(name)) {
+    throw webidl.errors.invalidArgument({
+      prefix: 'Headers.append',
+      value: name,
+      type: 'header name'
+    })
+  } else if (!isValidHeaderValue(value)) {
+    throw webidl.errors.invalidArgument({
+      prefix: 'Headers.append',
+      value,
+      type: 'header value'
+    })
+  }
+
+  // 3. If headers’s guard is "immutable", then throw a TypeError.
+  // 4. Otherwise, if headers’s guard is "request" and name is a
+  //    forbidden header name, return.
+  // Note: undici does not implement forbidden header names
+  if (headers[kGuard] === 'immutable') {
+    throw new TypeError('immutable')
+  } else if (headers[kGuard] === 'request-no-cors') {
+    // 5. Otherwise, if headers’s guard is "request-no-cors":
+    // TODO
+  }
+
+  // 6. Otherwise, if headers’s guard is "response" and name is a
+  //    forbidden response-header name, return.
+
+  // 7. Append (name, value) to headers’s header list.
+  return headers[kHeadersList].append(name, value)
+
+  // 8. If headers’s guard is "request-no-cors", then remove
+  //    privileged no-CORS request headers from headers
+}
+
 class HeadersList {
   /** @type {[string, string][]|null} */
   cookies = null
@@ -212,43 +265,7 @@ class Headers {
     name = webidl.converters.ByteString(name)
     value = webidl.converters.ByteString(value)
 
-    // 1. Normalize value.
-    value = headerValueNormalize(value)
-
-    // 2. If name is not a header name or value is not a
-    //    header value, then throw a TypeError.
-    if (!isValidHeaderName(name)) {
-      throw webidl.errors.invalidArgument({
-        prefix: 'Headers.append',
-        value: name,
-        type: 'header name'
-      })
-    } else if (!isValidHeaderValue(value)) {
-      throw webidl.errors.invalidArgument({
-        prefix: 'Headers.append',
-        value,
-        type: 'header value'
-      })
-    }
-
-    // 3. If headers’s guard is "immutable", then throw a TypeError.
-    // 4. Otherwise, if headers’s guard is "request" and name is a
-    //    forbidden header name, return.
-    // Note: undici does not implement forbidden header names
-    if (this[kGuard] === 'immutable') {
-      throw new TypeError('immutable')
-    } else if (this[kGuard] === 'request-no-cors') {
-      // 5. Otherwise, if headers’s guard is "request-no-cors":
-      // TODO
-    }
-
-    // 6. Otherwise, if headers’s guard is "response" and name is a
-    //    forbidden response-header name, return.
-
-    // 7. Append (name, value) to headers’s header list.
-    // 8. If headers’s guard is "request-no-cors", then remove
-    //    privileged no-CORS request headers from headers
-    return this[kHeadersList].append(name, value)
+    return appendHeader(this, name, value)
   }
 
   // https://fetch.spec.whatwg.org/#dom-headers-delete
@@ -422,16 +439,17 @@ 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

@@ -427,12 +427,10 @@ 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.`
       )
     }
   }