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buffer: add DataView support to isUtf8, isAscii, and stringLength #67179

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3a85311
buffer: add DataView support to isUtf8, isAscii, and stringLength
ShakilUrRehman21 Nov 1, 2026
a04161d
typings: add stringLengthUtf8 to buffer internalBinding
ShakilUrRehman21 Nov 3, 2026
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16 changes: 13 additions & 3 deletions doc/api/buffer.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1019,9 +1019,13 @@ the byte length as reported by `.byteLength` is returned.

<!-- YAML
added: v26.11.0
changes:
- version: REPLACEME
pr-url: https://github.com/nodejs/node/pull/REPLACEME
description: DataView is now supported.
-->

* `input` {Buffer | ArrayBuffer | TypedArray} The bytes that would be decoded.
* `input` {Buffer | ArrayBuffer | TypedArray | DataView} The bytes that would be decoded.
* `encoding` {string} The character encoding `input` would be decoded with.
**Default:** `'utf8'`.
* Returns: {integer}
Expand Down Expand Up @@ -5398,6 +5402,9 @@ added:
- v19.6.0
- v18.15.0
changes:
- version: REPLACEME
pr-url: https://github.com/nodejs/node/pull/REPLACEME
description: DataView is now supported.
- version:
- v26.8.0
- v24.21.0
Expand All @@ -5406,7 +5413,7 @@ changes:
as empty.
-->

* `input` {Buffer | ArrayBuffer | TypedArray} The input to validate.
* `input` {Buffer | ArrayBuffer | TypedArray | DataView} The input to validate.
* Returns: {boolean}

This function returns `true` if `input` contains only valid ASCII-encoded data,
Expand Down Expand Up @@ -5468,6 +5475,9 @@ added:
- v19.4.0
- v18.14.0
changes:
- version: REPLACEME
pr-url: https://github.com/nodejs/node/pull/REPLACEME
description: DataView is now supported.
- version:
- v26.8.0
- v24.21.0
Expand All @@ -5476,7 +5486,7 @@ changes:
as empty.
-->

* `input` {Buffer | ArrayBuffer | TypedArray} The input to validate.
* `input` {Buffer | ArrayBuffer | TypedArray | DataView} The input to validate.
* Returns: {boolean}

This function returns `true` if `input` contains only valid UTF-8-encoded data,
Expand Down
12 changes: 6 additions & 6 deletions lib/buffer.js
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Expand Up @@ -1484,19 +1484,19 @@ function atob(input) {
}

function isUtf8(input) {
if (isTypedArray(input) || isAnyArrayBuffer(input)) {
if (isArrayBufferView(input) || isAnyArrayBuffer(input)) {
return bindingIsUtf8(input);
}

throw new ERR_INVALID_ARG_TYPE('input', ['ArrayBuffer', 'Buffer', 'TypedArray'], input);
throw new ERR_INVALID_ARG_TYPE('input', ['ArrayBuffer', 'Buffer', 'TypedArray', 'DataView'], input);
}

function isAscii(input) {
if (isTypedArray(input) || isAnyArrayBuffer(input)) {
if (isArrayBufferView(input) || isAnyArrayBuffer(input)) {
return bindingIsAscii(input);
}

throw new ERR_INVALID_ARG_TYPE('input', ['ArrayBuffer', 'Buffer', 'TypedArray'], input);
throw new ERR_INVALID_ARG_TYPE('input', ['ArrayBuffer', 'Buffer', 'TypedArray', 'DataView'], input);
}

/**
Expand All @@ -1511,8 +1511,8 @@ function isLatin1(input) {
}

function stringLength(input, encoding = 'utf8') {
if (!isTypedArray(input) && !isAnyArrayBuffer(input)) {
throw new ERR_INVALID_ARG_TYPE('input', ['ArrayBuffer', 'Buffer', 'TypedArray'], input);
if (!isArrayBufferView(input) && !isAnyArrayBuffer(input)) {
throw new ERR_INVALID_ARG_TYPE('input', ['ArrayBuffer', 'Buffer', 'TypedArray', 'DataView'], input);
}
validateString(encoding, 'encoding');
const ops = getEncodingOps(encoding);
Expand Down
6 changes: 3 additions & 3 deletions src/node_buffer.cc
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Expand Up @@ -1372,7 +1372,7 @@ static bool ValidateUtf8(Local<Value> value) {

static void IsUtf8(const FunctionCallbackInfo<Value>& args) {
CHECK_EQ(args.Length(), 1);
CHECK(args[0]->IsTypedArray() || args[0]->IsArrayBuffer() ||
CHECK(args[0]->IsArrayBufferView() || args[0]->IsArrayBuffer() ||

@anonrig anonrig Nov 2, 2026

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these changes require updates to typings folder as well...

@ShakilUrRehman21 ShakilUrRehman21 Nov 3, 2026

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Updated typings/internalBinding/buffer.d.ts to include stringLengthUtf8. Thanks for pointing that out!

Keeping this PR in draft for now per first-time contributor guidelines until my first PR (#67178) lands.

args[0]->IsSharedArrayBuffer());

args.GetReturnValue().Set(ValidateUtf8(args[0]));
Expand All @@ -1397,7 +1397,7 @@ static bool ValidateAscii(Local<Value> value) {

static void IsAscii(const FunctionCallbackInfo<Value>& args) {
CHECK_EQ(args.Length(), 1);
CHECK(args[0]->IsTypedArray() || args[0]->IsArrayBuffer() ||
CHECK(args[0]->IsArrayBufferView() || args[0]->IsArrayBuffer() ||
args[0]->IsSharedArrayBuffer());

args.GetReturnValue().Set(ValidateAscii(args[0]));
Expand Down Expand Up @@ -1627,7 +1627,7 @@ static double StringLengthUtf8Impl(Local<Value> value) {

static void StringLengthUtf8(const FunctionCallbackInfo<Value>& args) {
CHECK_EQ(args.Length(), 1);
CHECK(args[0]->IsTypedArray() || args[0]->IsArrayBuffer() ||
CHECK(args[0]->IsArrayBufferView() || args[0]->IsArrayBuffer() ||
args[0]->IsSharedArrayBuffer());

args.GetReturnValue().Set(StringLengthUtf8Impl(args[0]));
Expand Down
11 changes: 11 additions & 0 deletions test/parallel/test-buffer-isascii.js
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Expand Up @@ -10,6 +10,9 @@ const encoder = new TextEncoder();
assert.strictEqual(isAscii(encoder.encode('hello')), true);
assert.strictEqual(isAscii(encoder.encode('ğ')), false);
assert.strictEqual(isAscii(Buffer.from([])), true);
assert.strictEqual(isAscii(new DataView(new ArrayBuffer(0))), true);
assert.strictEqual(isAscii(new DataView(encoder.encode('hello').buffer)), true);
assert.strictEqual(isAscii(new DataView(encoder.encode('ğ').buffer)), false);

[
undefined,
Expand All @@ -34,10 +37,12 @@ assert.strictEqual(isAscii(Buffer.from([])), true);
const arrayBuffer = new ArrayBuffer(1);
const typedArray = new Uint8Array(arrayBuffer);
typedArray[0] = 0xff;
const dataView = new DataView(arrayBuffer);
const inputs = [
arrayBuffer,
typedArray,
Buffer.from(arrayBuffer),
dataView,
];
for (const input of inputs) {
assert.strictEqual(isAscii(input), false);
Expand All @@ -47,3 +52,9 @@ assert.strictEqual(isAscii(Buffer.from([])), true);
assert.strictEqual(isAscii(input), true);
}
}

{
const buffer = Buffer.from('hello world');
const view = new DataView(buffer.buffer, buffer.byteOffset, 5);
assert.strictEqual(isAscii(view), true);
}
10 changes: 10 additions & 0 deletions test/parallel/test-buffer-isutf8.js
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Expand Up @@ -10,6 +10,8 @@ const encoder = new TextEncoder();
assert.strictEqual(isUtf8(encoder.encode('hello')), true);
assert.strictEqual(isUtf8(encoder.encode('ğ')), true);
assert.strictEqual(isUtf8(Buffer.from([])), true);
assert.strictEqual(isUtf8(new DataView(new ArrayBuffer(0))), true);
assert.strictEqual(isUtf8(new DataView(encoder.encode('hello').buffer)), true);

// Taken from test/fixtures/wpt/encoding/textdecoder-fatal.any.js
[
Expand Down Expand Up @@ -78,10 +80,12 @@ assert.strictEqual(isUtf8(Buffer.from([])), true);
const arrayBuffer = new ArrayBuffer(1);
const typedArray = new Uint8Array(arrayBuffer);
typedArray[0] = 0xff;
const dataView = new DataView(arrayBuffer);
const inputs = [
arrayBuffer,
typedArray,
Buffer.from(arrayBuffer),
dataView,
];
for (const input of inputs) {
assert.strictEqual(isUtf8(input), false);
Expand All @@ -91,3 +95,9 @@ assert.strictEqual(isUtf8(Buffer.from([])), true);
assert.strictEqual(isUtf8(input), true);
}
}

{
const buffer = Buffer.from('hello world');
const view = new DataView(buffer.buffer, buffer.byteOffset, 5);
assert.strictEqual(isUtf8(view), true);
}
6 changes: 4 additions & 2 deletions test/parallel/test-buffer-stringlength.js
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Expand Up @@ -35,6 +35,7 @@ assert.strictEqual(Buffer.stringLength(Buffer.alloc(0)), 0);
assert.strictEqual(Buffer.stringLength(ab), expected);
assert.strictEqual(Buffer.stringLength(sab), expected);
assert.strictEqual(Buffer.stringLength(new Uint8Array(ab)), expected);
assert.strictEqual(Buffer.stringLength(new DataView(ab)), expected);
assert.strictEqual(Buffer.stringLength(new Uint16Array(ab.slice(0, 16))),
Buffer.from(ab.slice(0, 16)).toString().length);
}
Expand All @@ -43,9 +44,11 @@ assert.strictEqual(Buffer.stringLength(Buffer.alloc(0)), 0);
{
const ab = new ArrayBuffer(8);
const view = new Uint8Array(ab);
const dataView = new DataView(ab);
structuredClone(ab, { transfer: [ab] });
assert.strictEqual(Buffer.stringLength(ab), 0);
assert.strictEqual(Buffer.stringLength(view), 0);
assert.strictEqual(Buffer.stringLength(dataView), 0);
}

// Invalid UTF-8 is counted the way toString() decodes it (one U+FFFD per
Expand Down Expand Up @@ -119,8 +122,7 @@ assert.strictEqual(Buffer.stringLength(Buffer.alloc(0)), 0);
}

// Argument validation.
for (const input of [undefined, null, 'abc', 42, {}, [], new Blob([]),
new DataView(new ArrayBuffer(4))]) {
for (const input of [undefined, null, 'abc', 42, {}, [], new Blob([])]) {
assert.throws(() => Buffer.stringLength(input),
{ code: 'ERR_INVALID_ARG_TYPE' });
}
Expand Down
1 change: 1 addition & 0 deletions typings/internalBinding/buffer.d.ts
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Expand Up @@ -22,6 +22,7 @@ export interface BufferBinding {
isUtf8(input: ArrayBufferView | ArrayBuffer | SharedArrayBuffer): boolean;
isAscii(input: ArrayBufferView | ArrayBuffer | SharedArrayBuffer): boolean;
isLatin1(input: string): boolean;
stringLengthUtf8(input: ArrayBufferView | ArrayBuffer | SharedArrayBuffer): number;

mask(source: ArrayBufferView, destination: ArrayBufferView, offset: number, length: number, mask: number): boolean;

Expand Down