fs: use byteLength to handle ArrayBuffer views

Unlike TypedArray, DataView doesn't have a length property.

PR-URL: #38187
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

doc/api/fs.md

@@ -265,18 +265,20 @@ added: v10.0.0
 added: v10.0.0
 -->
 
-* `buffer` {Buffer|Uint8Array} A buffer that will be filled with the file
-  data read.
+* `buffer` {Buffer|TypedArray|DataView} A buffer that will be filled with the
+  file data read.
 * `offset` {integer} The location in the buffer at which to start filling.
   **Default:** `0`
-* `length` {integer} The number of bytes to read. **Default:** `buffer.length`
+* `length` {integer} The number of bytes to read. **Default:**
+  `buffer.byteLength`
 * `position` {integer} The location where to begin reading data from the
   file. If `null`, data will be read from the current file position, and
   the position will be updated. If `position` is an integer, the current
   file position will remain unchanged.
 * Returns: {Promise} Fulfills upon success with an object with two properties:
   * `bytesRead` {integer} The number of bytes read
-  * `buffer` {Buffer|Uint8Array} A reference to the passed in `buffer` argument.
+  * `buffer` {Buffer|TypedArray|DataView} A reference to the passed in `buffer`
+    argument.
 
 Reads data from the file and stores that in the given buffer.
 
@@ -290,19 +292,20 @@ added:
  - v12.17.0
 -->
 * `options` {Object}
-  * `buffer` {Buffer|Uint8Array} A buffer that will be filled with the file
-    data read. **Default:** `Buffer.alloc(16384)`
+  * `buffer` {Buffer|TypedArray|DataView} A buffer that will be filled with the
+    file data read. **Default:** `Buffer.alloc(16384)`
   * `offset` {integer} The location in the buffer at which to start filling.
     **Default:** `0`
-  * `length` {integer} The number of bytes to read. **Default:** `buffer.length`
+  * `length` {integer} The number of bytes to read. **Default:**
+    `buffer.byteLength`
   * `position` {integer} The location where to begin reading data from the
     file. If `null`, data will be read from the current file position, and
     the position will be updated. If `position` is an integer, the current
     file position will remain unchanged. **Default:**: `null`
 * Returns: {Promise} Fulfills upon success with an object with two properties:
   * `bytesRead` {integer} The number of bytes read
-  * `buffer` {Buffer|Uint8Array} A reference to the passed in `buffer`
-  argument.
+  * `buffer` {Buffer|TypedArray|DataView} A reference to the passed in `buffer`
+    argument.
 
 Reads data from the file and stores that in the given buffer.
 
@@ -434,10 +437,11 @@ changes:
                  buffers anymore.
 -->
 
-* `buffer` {Buffer|Uint8Array|string|Object}
+* `buffer` {Buffer|TypedArray|DataView|string|Object}
 * `offset` {integer} The start position from within `buffer` where the data
-  to write begins.
-* `length` {integer} The number of bytes from `buffer` to write.
+  to write begins. **Default:** `0`
+* `length` {integer} The number of bytes from `buffer` to write. **Default:**
+  `buffer.byteLength`
 * `position` {integer} The offset from the beginning of the file where the
   data from `buffer` should be written. If `position` is not a `number`,
   the data will be written at the current position. See the POSIX pwrite(2)
@@ -449,8 +453,8 @@ Write `buffer` to the file.
 The promise is resolved with an object containing two properties:
 
 * `bytesWritten` {integer} the number of bytes written
-* `buffer` {Buffer|Uint8Array|string|Object} a reference to the `buffer`
-  written.
+* `buffer` {Buffer|TypedArray|DataView|string|Object} a reference to the
+  `buffer` written.
 
 It is unsafe to use `filehandle.write()` multiple times on the same file
 without waiting for the promise to be resolved (or rejected). For this
@@ -512,7 +516,7 @@ changes:
                  strings anymore.
 -->
 
-* `data` {string|Buffer|Uint8Array|Object}
+* `data` {string|Buffer|TypedArray|DataView|Object}
 * `options` {Object|string}
   * `encoding` {string|null} The expected character encoding when `data` is a
     string. **Default:** `'utf8'`
@@ -1270,7 +1274,7 @@ changes:
 -->
 
 * `file` {string|Buffer|URL|FileHandle} filename or `FileHandle`
-* `data` {string|Buffer|Uint8Array|Object|AsyncIterable|Iterable
+* `data` {string|Buffer|TypedArray|DataView|Object|AsyncIterable|Iterable
   |Stream}
 * `options` {Object|string}
   * `encoding` {string|null} **Default:** `'utf8'`
@@ -2722,9 +2726,11 @@ changes:
 
 * `fd` {integer}
 * `buffer` {Buffer|TypedArray|DataView} The buffer that the data will be
-  written to.
-* `offset` {integer} The position in `buffer` to write the data to.
-* `length` {integer}  The number of bytes to read.
+  written to. **Default:** `Buffer.alloc(16384)`
+* `offset` {integer} The position in `buffer` to write the data to. **Default:**
+  `0`
+* `length` {integer} The number of bytes to read. **Default:**
+  `buffer.byteLength`
 * `position` {integer|bigint} Specifies where to begin reading from in the
   file. If `position` is `null` or `-1 `, data will be read from the current
   file position, and the file position will be updated. If `position` is an
@@ -2761,7 +2767,7 @@ changes:
 * `options` {Object}
   * `buffer` {Buffer|TypedArray|DataView} **Default:** `Buffer.alloc(16384)`
   * `offset` {integer} **Default:** `0`
-  * `length` {integer} **Default:** `buffer.length`
+  * `length` {integer} **Default:** `buffer.byteLength`
   * `position` {integer|bigint} **Default:** `null`
 * `callback` {Function}
   * `err` {Error}
@@ -4689,7 +4695,7 @@ changes:
 * `buffer` {Buffer|TypedArray|DataView}
 * `options` {Object}
   * `offset` {integer} **Default:** `0`
-  * `length` {integer} **Default:** `buffer.length`
+  * `length` {integer} **Default:** `buffer.byteLength`
   * `position` {integer|bigint} **Default:** `null`
 * Returns: {number}
 

lib/fs.js

@@ -532,7 +532,7 @@ function read(fd, buffer, offset, length, position, callback) {
     ({
       buffer = Buffer.alloc(16384),
       offset = 0,
-      length = buffer.length,
+      length = buffer.byteLength,
       position
     } = options);
   }
@@ -587,15 +587,15 @@ ObjectDefineProperty(read, internalUtil.customPromisifyArgs,
 function readSync(fd, buffer, offset, length, position) {
   fd = getValidatedFd(fd);
 
+  validateBuffer(buffer);
+
   if (arguments.length <= 3) {
     // Assume fs.read(fd, buffer, options)
     const options = offset || {};
 
-    ({ offset = 0, length = buffer.length, position } = options);
+    ({ offset = 0, length = buffer.byteLength, position } = options);
   }
 
-  validateBuffer(buffer);
-
   if (offset == null) {
     offset = 0;
   } else {
@@ -682,7 +682,7 @@ function write(fd, buffer, offset, length, position, callback) {
       validateInteger(offset, 'offset');
     }
     if (typeof length !== 'number')
-      length = buffer.length - offset;
+      length = buffer.byteLength - offset;
     if (typeof position !== 'number')
       position = null;
     validateOffsetLengthWrite(offset, length, buffer.byteLength);

lib/internal/fs/promises.js

@@ -280,19 +280,19 @@ async function writeFileHandle(filehandle, data, signal, encoding) {
       checkAborted(signal);
       await write(
         filehandle, buf, undefined,
-        isArrayBufferView(buf) ? buf.length : encoding);
+        isArrayBufferView(buf) ? buf.byteLength : encoding);
       checkAborted(signal);
     }
     return;
   }
   data = new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
-  let remaining = data.length;
+  let remaining = data.byteLength;
   if (remaining === 0) return;
   do {
     checkAborted(signal);
     const { bytesWritten } =
       await write(filehandle, data, 0,
-                  MathMin(kWriteFileMaxChunkSize, data.length));
+                  MathMin(kWriteFileMaxChunkSize, data.byteLength));
     remaining -= bytesWritten;
     data = new Uint8Array(
       data.buffer,
@@ -404,7 +404,7 @@ async function read(handle, bufferOrOptions, offset, length, position) {
       buffer = Buffer.alloc(16384);
     }
     offset = bufferOrOptions.offset || 0;
-    length = buffer.length;
+    length = buffer.byteLength;
     position = bufferOrOptions.position || null;
   }
 
@@ -419,12 +419,12 @@ async function read(handle, bufferOrOptions, offset, length, position) {
   if (length === 0)
     return { bytesRead: length, buffer };
 
-  if (buffer.length === 0) {
+  if (buffer.byteLength === 0) {
     throw new ERR_INVALID_ARG_VALUE('buffer', buffer,
                                     'is empty and cannot be written');
   }
 
-  validateOffsetLengthRead(offset, length, buffer.length);
+  validateOffsetLengthRead(offset, length, buffer.byteLength);
 
   if (!NumberIsSafeInteger(position))
     position = -1;
@@ -447,7 +447,7 @@ async function readv(handle, buffers, position) {
 }
 
 async function write(handle, buffer, offset, length, position) {
-  if (buffer?.length === 0)
+  if (buffer?.byteLength === 0)
     return { bytesWritten: 0, buffer };
 
   if (isArrayBufferView(buffer)) {
@@ -457,7 +457,7 @@ async function write(handle, buffer, offset, length, position) {
       validateInteger(offset, 'offset');
     }
     if (typeof length !== 'number')
-      length = buffer.length - offset;
+      length = buffer.byteLength - offset;
     if (typeof position !== 'number')
       position = null;
     validateOffsetLengthWrite(offset, length, buffer.byteLength);

test/parallel/test-fs-write-buffer.js

@@ -146,3 +146,20 @@ tmpdir.refresh();
     fs.closeSync(fd);
   }));
 }
+
+// fs.write with a DataView, without the offset and length parameters:
+{
+  const filename = path.join(tmpdir.path, 'write8.txt');
+  fs.open(filename, 'w', 0o644, common.mustSucceed((fd) => {
+    const cb = common.mustSucceed((written) => {
+      assert.strictEqual(written, expected.length);
+      fs.closeSync(fd);
+
+      const found = fs.readFileSync(filename, 'utf8');
+      assert.strictEqual(found, expected.toString());
+    });
+
+    const uint8 = Uint8Array.from(expected);
+    fs.write(fd, new DataView(uint8.buffer), cb);
+  }));
+}