streams: refactor BufferList into ES6 class

PR-URL: https://github.com/nodejs/node/pull/12644
Reviewed-By: Brian White <mscdex@mscdex.net>

lib/internal/streams/BufferList.js

@@ -2,71 +2,71 @@
 
 const Buffer = require('buffer').Buffer;
 
-module.exports = BufferList;
+module.exports = class BufferList {
+  constructor() {
+    this.head = null;
+    this.tail = null;
+    this.length = 0;
+  }
 
-function BufferList() {
-  this.head = null;
-  this.tail = null;
-  this.length = 0;
-}
+  push(v) {
+    const entry = { data: v, next: null };
+    if (this.length > 0)
+      this.tail.next = entry;
+    else
+      this.head = entry;
+    this.tail = entry;
+    ++this.length;
+  }
 
-BufferList.prototype.push = function(v) {
-  const entry = { data: v, next: null };
-  if (this.length > 0)
-    this.tail.next = entry;
-  else
+  unshift(v) {
+    const entry = { data: v, next: this.head };
+    if (this.length === 0)
+      this.tail = entry;
     this.head = entry;
-  this.tail = entry;
-  ++this.length;
-};
+    ++this.length;
+  }
 
-BufferList.prototype.unshift = function(v) {
-  const entry = { data: v, next: this.head };
-  if (this.length === 0)
-    this.tail = entry;
-  this.head = entry;
-  ++this.length;
-};
+  shift() {
+    if (this.length === 0)
+      return;
+    const ret = this.head.data;
+    if (this.length === 1)
+      this.head = this.tail = null;
+    else
+      this.head = this.head.next;
+    --this.length;
+    return ret;
+  }
 
-BufferList.prototype.shift = function() {
-  if (this.length === 0)
-    return;
-  const ret = this.head.data;
-  if (this.length === 1)
+  clear() {
     this.head = this.tail = null;
-  else
-    this.head = this.head.next;
-  --this.length;
-  return ret;
-};
-
-BufferList.prototype.clear = function() {
-  this.head = this.tail = null;
-  this.length = 0;
-};
+    this.length = 0;
+  }
 
-BufferList.prototype.join = function(s) {
-  if (this.length === 0)
-    return '';
-  var p = this.head;
-  var ret = '' + p.data;
-  while (p = p.next)
-    ret += s + p.data;
-  return ret;
-};
+  join(s) {
+    if (this.length === 0)
+      return '';
+    var p = this.head;
+    var ret = '' + p.data;
+    while (p = p.next)
+      ret += s + p.data;
+    return ret;
+  }
 
-BufferList.prototype.concat = function(n) {
-  if (this.length === 0)
-    return Buffer.alloc(0);
-  if (this.length === 1)
-    return this.head.data;
-  const ret = Buffer.allocUnsafe(n >>> 0);
-  var p = this.head;
-  var i = 0;
-  while (p) {
-    p.data.copy(ret, i);
-    i += p.data.length;
-    p = p.next;
+  concat(n) {
+    if (this.length === 0)
+      return Buffer.alloc(0);
+    if (this.length === 1)
+      return this.head.data;
+    const ret = Buffer.allocUnsafe(n >>> 0);
+    var p = this.head;
+    var i = 0;
+    while (p) {
+      p.data.copy(ret, i);
+      i += p.data.length;
+      p = p.next;
+    }
+    return ret;
   }
-  return ret;
 };