Move internal modules to “internal” folder.

.internal/cloneBuffer.js

@@ -0,0 +1,34 @@
+import root from './.internal/root.js';
+
+/** Detect free variable `exports`. */
+const freeExports = typeof exports == 'object' && exports && !exports.nodeType && exports;
+
+/** Detect free variable `module`. */
+const freeModule = freeExports && typeof module == 'object' && module && !module.nodeType && module;
+
+/** Detect the popular CommonJS extension `module.exports`. */
+const moduleExports = freeModule && freeModule.exports === freeExports;
+
+/** Built-in value references. */
+const Buffer = moduleExports ? root.Buffer : undefined, allocUnsafe = Buffer ? Buffer.allocUnsafe : undefined;
+
+/**
+ * Creates a clone of  `buffer`.
+ *
+ * @private
+ * @param {Buffer} buffer The buffer to clone.
+ * @param {boolean} [isDeep] Specify a deep clone.
+ * @returns {Buffer} Returns the cloned buffer.
+ */
+function cloneBuffer(buffer, isDeep) {
+  if (isDeep) {
+    return buffer.slice();
+  }
+  const length = buffer.length;
+  const result = allocUnsafe ? allocUnsafe(length) : new buffer.constructor(length);
+
+  buffer.copy(result);
+  return result;
+}
+
+export default cloneBuffer;