Reverted checking for Buffer API's existence.

src/io/bufferIOBase.ts

@@ -12,19 +12,6 @@ export type BufferIOOptions = {
   endianness?: Endianness | 'system';
 };
 
-interface BufferView {
-  byteOffset: number;
-  buffer: ArrayBufferLike;
-}
-
-function isBufferView(value: unknown): value is BufferView {
-  const BufferImpl =
-    typeof global !== 'undefined' && 'Buffer' in global
-      ? global.Buffer
-      : undefined;
-  return !!BufferImpl && value instanceof BufferImpl;
-}
-
 export class BufferIOBase {
   protected readonly uint8View: Uint8Array;
   protected readonly helperInt32View: Int32Array;
@@ -47,7 +34,7 @@ export class BufferIOBase {
     this.switchEndianness = this.endianness !== systemEndianness;
 
     let innerBuffer = buffer;
-    if (isBufferView(innerBuffer)) {
+    if (typeof Buffer !== 'undefined' && innerBuffer instanceof Buffer) {
       // Getting rid of the outer shell, which causes the Uint8Array line to create a copy, instead of a view.
       this.byteOffset += innerBuffer.byteOffset;
       innerBuffer = innerBuffer.buffer;