3 files changed, 17 insertions, 11 deletions
diff --git a/std/node/_fs/_fs_common.ts b/std/node/_fs/_fs_common.ts
index 1f00bc481..bf7c0f675 100644
--- a/std/node/_fs/_fs_common.ts
+++ b/std/node/_fs/_fs_common.ts
@@ -35,6 +35,11 @@ export function getEncoding(
   const encoding =
     typeof optOrCallback === "string" ? optOrCallback : optOrCallback.encoding;
   if (!encoding) return null;
+  return encoding;
+}
+
+export function checkEncoding(encoding: string | null): string | null {
+  if (!encoding) return null;
   if (encoding === "utf8" || encoding === "utf-8") {
     return "utf8";
   }
diff --git a/std/node/_fs/_fs_readFile.ts b/std/node/_fs/_fs_readFile.ts
index ccea71cd6..448045fd2 100644
--- a/std/node/_fs/_fs_readFile.ts
+++ b/std/node/_fs/_fs_readFile.ts
@@ -3,23 +3,23 @@
 import { intoCallbackAPIWithIntercept, MaybeEmpty } from "../_utils.ts";
 
 import { getEncoding, FileOptions } from "./_fs_common.ts";
+import { Buffer } from "../buffer.ts";
 import { fromFileUrl } from "../path.ts";
 
 const { readFile: denoReadFile, readFileSync: denoReadFileSync } = Deno;
 
 type ReadFileCallback = (
   err: MaybeEmpty<Error>,
-  data: MaybeEmpty<string | Uint8Array>
+  data: MaybeEmpty<string | Buffer>
 ) => void;
 
 function maybeDecode(
   data: Uint8Array,
   encoding: string | null
-): string | Uint8Array {
-  if (encoding === "utf8") {
-    return new TextDecoder().decode(data);
-  }
-  return data;
+): string | Buffer {
+  const buffer = new Buffer(data.buffer, data.byteOffset, data.byteLength);
+  if (encoding) return buffer.toString(encoding);
+  return buffer;
 }
 
 export function readFile(
@@ -37,9 +37,9 @@ export function readFile(
 
   const encoding = getEncoding(optOrCallback);
 
-  intoCallbackAPIWithIntercept<Uint8Array, string | Uint8Array>(
+  intoCallbackAPIWithIntercept<Uint8Array, string | Buffer>(
     denoReadFile,
-    (data: Uint8Array): string | Uint8Array => maybeDecode(data, encoding),
+    (data: Uint8Array): string | Buffer => maybeDecode(data, encoding),
     cb,
     path
   );
@@ -48,7 +48,7 @@ export function readFile(
 export function readFileSync(
   path: string | URL,
   opt?: FileOptions | string
-): string | Uint8Array {
+): string | Buffer {
   path = path instanceof URL ? fromFileUrl(path) : path;
   return maybeDecode(denoReadFileSync(path), getEncoding(opt));
 }
diff --git a/std/node/_fs/_fs_writeFile.ts b/std/node/_fs/_fs_writeFile.ts
index 72e75c97a..4ede42638 100644
--- a/std/node/_fs/_fs_writeFile.ts
+++ b/std/node/_fs/_fs_writeFile.ts
@@ -7,6 +7,7 @@ import {
   CallbackWithError,
   isFileOptions,
   getEncoding,
+  checkEncoding,
   getOpenOptions,
 } from "./_fs_common.ts";
 
@@ -35,7 +36,7 @@ export function writeFile(
     ? options.mode
     : undefined;
 
-  const encoding = getEncoding(options) || "utf8";
+  const encoding = checkEncoding(getEncoding(options)) || "utf8";
   const openOptions = getOpenOptions(flag || "w");
 
   if (typeof data === "string" && encoding === "utf8")
@@ -82,7 +83,7 @@ export function writeFileSync(
     ? options.mode
     : undefined;
 
-  const encoding = getEncoding(options) || "utf8";
+  const encoding = checkEncoding(getEncoding(options)) || "utf8";
   const openOptions = getOpenOptions(flag || "w");
 
   if (typeof data === "string" && encoding === "utf8")