buffer: proof of concept that everything is possible

lib/buffer.js

@@ -8,20 +8,42 @@ const internalUtil = require('internal/util');
 
 class FastBuffer extends Uint8Array {}
 
-FastBuffer.prototype.constructor = Buffer;
-Buffer.prototype = FastBuffer.prototype;
+const kFromErrorMsg = 'First argument must be a string, Buffer, ' +
+                      'ArrayBuffer, Array, or array-like object.';
 
-exports.Buffer = Buffer;
-exports.SlowBuffer = SlowBuffer;
 exports.INSPECT_MAX_BYTES = 50;
 exports.kMaxLength = binding.kMaxLength;
 
-const kFromErrorMsg = 'First argument must be a string, Buffer, ' +
-                      'ArrayBuffer, Array, or array-like object.';
-
 Buffer.poolSize = 8 * 1024;
 var poolSize, poolOffset, allocPool;
 
+const BufferClass = ((BufferFn) => class Buffer extends FastBuffer {
+  constructor(arg, encodingOrOffset, length) {
+    let realbuf;
+
+    // Common case.
+    if (typeof arg === 'number') {
+      if (typeof encodingOrOffset === 'string') {
+        throw new Error(
+          'If encoding is specified then the first argument must be a string'
+        );
+      }
+      realbuf = BufferFn.allocUnsafe(arg);
+    } else {
+      realbuf = BufferFn.from(arg, encodingOrOffset, length);
+    }
+
+    super(realbuf.buffer, realbuf.byteOffset, realbuf.byteLength);
+  }
+})(Buffer);
+
+FastBuffer.prototype.constructor = Buffer;
+BufferClass.prototype.constructor = Buffer;
+Buffer.prototype = FastBuffer.prototype;
+
+exports.Buffer = Buffer;
+exports.SlowBuffer = SlowBuffer;
+exports.BufferClass = BufferClass;
 
 binding.setupBufferJS(Buffer.prototype, bindingObj);
 
@@ -65,16 +87,7 @@ function alignPool() {
  * would ever actually be removed.
  **/
 function Buffer(arg, encodingOrOffset, length) {
-  // Common case.
-  if (typeof arg === 'number') {
-    if (typeof encodingOrOffset === 'string') {
-      throw new Error(
-        'If encoding is specified then the first argument must be a string'
-      );
-    }
-    return Buffer.allocUnsafe(arg);
-  }
-  return Buffer.from(arg, encodingOrOffset, length);
+  return new BufferClass(arg, encodingOrOffset, length);
 }
 
 /**