fs: fix fs.promises.writeFile with typed arrays

Before this change, only the first part of typed arrays which have more
than 1 byte per element (e.g. Uint16Array) would be written.
This also removes the use of the `slice` method to avoid unnecessary
copying the data.

Fixes: https://github.com/nodejs/node/issues/35343

PR-URL: https://github.com/nodejs/node/pull/35376
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

1 files changed, 10 insertions, 3 deletions

diff --git a/lib/internal/fs/promises.js b/lib/internal/fs/promises.js
index a938b382eb1..60a28735a98 100644
--- a/lib/internal/fs/promises.js
+++ b/lib/internal/fs/promises.js
@@ -10,12 +10,13 @@ const kReadFileMaxChunkSize = 2 ** 14;
 const kWriteFileMaxChunkSize = 2 ** 14;
 
 const {
+  Error,
   MathMax,
   MathMin,
   NumberIsSafeInteger,
-  Symbol,
-  Error,
   Promise,
+  Symbol,
+  Uint8Array,
 } = primordials;
 
 const {
@@ -237,6 +238,8 @@ async function fsCall(fn, handle, ...args) {
 }
 
 async function writeFileHandle(filehandle, data) {
+  // `data` could be any kind of typed array.
+  data = new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
   let remaining = data.length;
   if (remaining === 0) return;
   do {
@@ -244,7 +247,11 @@ async function writeFileHandle(filehandle, data) {
       await write(filehandle, data, 0,
                   MathMin(kWriteFileMaxChunkSize, data.length));
     remaining -= bytesWritten;
-    data = data.slice(bytesWritten);
+    data = new Uint8Array(
+      data.buffer,
+      data.byteOffset + bytesWritten,
+      data.byteLength - bytesWritten
+    );
   } while (remaining > 0);
 }