fs: allow writing files with ArrayBuffers

Extended most file writing functions to accept ArrayBuffers rather
than only strings, buffers, or data views. Does not include
functions that accept arrays of dataviews, such as writev.

Fixes: #42228

lib/fs.js

@@ -38,6 +38,7 @@ const {
   StringPrototypeCharCodeAt,
   StringPrototypeIndexOf,
   StringPrototypeSlice,
+  Uint8Array,
 } = primordials;
 
 const { fs: constants } = internalBinding('constants');
@@ -56,7 +57,7 @@ const {
 } = constants;
 
 const pathModule = require('path');
-const { isArrayBufferView } = require('internal/util/types');
+const { isArrayBufferView, isArrayBuffer } = require('internal/util/types');
 
 // We need to get the statValues from the binding at the callsite since
 // it's re-initialized after deserialization.
@@ -819,6 +820,9 @@ function write(fd, buffer, offsetOrOptions, length, position, callback) {
   fd = getValidatedFd(fd);
 
   let offset = offsetOrOptions;
+  if (isArrayBuffer(buffer)) {
+    buffer = new Uint8Array(buffer);
+  }
   if (isArrayBufferView(buffer)) {
     callback = maybeCallback(callback || position || length || offset);
 
@@ -888,6 +892,9 @@ function writeSync(fd, buffer, offsetOrOptions, length, position) {
   let result;
 
   let offset = offsetOrOptions;
+  if (isArrayBuffer(buffer)) {
+    buffer = new Uint8Array(buffer);
+  }
   if (isArrayBufferView(buffer)) {
     if (typeof offset === 'object') {
       ({
@@ -2178,6 +2185,10 @@ function writeFile(path, data, options, callback) {
   options = getOptions(options, { encoding: 'utf8', mode: 0o666, flag: 'w' });
   const flag = options.flag || 'w';
 
+  if (isArrayBuffer(data)) {
+    data = new Uint8Array(data);
+  }
+
   if (!isArrayBufferView(data)) {
     validateStringAfterArrayBufferView(data, 'data');
     data = Buffer.from(data, options.encoding || 'utf8');
@@ -2218,7 +2229,7 @@ function writeFile(path, data, options, callback) {
 function writeFileSync(path, data, options) {
   options = getOptions(options, { encoding: 'utf8', mode: 0o666, flag: 'w' });
 
-  if (!isArrayBufferView(data)) {
+  if (!isArrayBufferView(data) && !isArrayBuffer(data)) {
     validateStringAfterArrayBufferView(data, 'data');
     data = Buffer.from(data, options.encoding || 'utf8');
   }

lib/internal/fs/promises.js

@@ -38,7 +38,7 @@ const {
   AbortError,
   aggregateTwoErrors,
 } = require('internal/errors');
-const { isArrayBufferView } = require('internal/util/types');
+const { isArrayBuffer, isArrayBufferView } = require('internal/util/types');
 const { rimrafPromises } = require('internal/fs/rimraf');
 const {
   constants: {
@@ -409,7 +409,11 @@ async function writeFileHandle(filehandle, data, signal, encoding) {
     }
     return;
   }
-  data = new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
+  if (isArrayBuffer(data)) {
+    data = new Uint8Array(data);
+  } else {
+    data = new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
+  }
   let remaining = data.byteLength;
   if (remaining === 0) return;
   do {
@@ -610,6 +614,9 @@ async function readv(handle, buffers, position) {
 }
 
 async function write(handle, buffer, offsetOrOptions, length, position) {
+  if (isArrayBuffer(buffer)) {
+    buffer = new Uint8Array(buffer);
+  }
   if (buffer?.byteLength === 0)
     return { __proto__: null, bytesWritten: 0, buffer };
 
@@ -884,7 +891,7 @@ async function writeFile(path, data, options) {
   options = getOptions(options, { encoding: 'utf8', mode: 0o666, flag: 'w' });
   const flag = options.flag || 'w';
 
-  if (!isArrayBufferView(data) && !isCustomIterable(data)) {
+  if (!isArrayBufferView(data) && !isArrayBuffer(data) && !isCustomIterable(data)) {
     validateStringAfterArrayBufferView(data, 'data');
     data = Buffer.from(data, options.encoding || 'utf8');
   }