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buffer: make byteLength work with ArrayBuffer & DataView #5255

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buffer: make byteLength work with ArrayBuffer & DataView 
Convert anything to string, but Buffer, TypedArray and ArrayBuffer

```
var uint8 = new Uint8Array([0xf0, 0x9f, 0x90]);
Buffer.byteLength(uint8); // should be 3, but returns 11
Buffer.byteLength(uint8.buffer); // should be 3, but return 20
```
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@JacksonTian
JacksonTian committed Mar 23, 2016
commit 0c74f6049b505863e5d13f400cfb7a6fec76e9a4
9 changes: 8 additions & 1 deletion doc/api/buffer.markdown
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Expand Up @@ -468,7 +468,7 @@ additional performance that `Buffer.allocUnsafe(size)` provides.

### Class Method: Buffer.byteLength(string[, encoding])

* `string` {String}
* `string` {String | Buffer | TypedArray | DataView | ArrayBuffer}
* `encoding` {String} Default: `'utf8'`
* Return: {Number}

Expand All @@ -487,6 +487,11 @@ console.log(`${str}: ${str.length} characters, ` +
// ½ + ¼ = ¾: 9 characters, 12 bytes
```

When `string` is a `Buffer`/[`DataView`][]/[`TypedArray`][]/`ArrayBuffer`,
returns the actual byte length.

Otherwise, converts to `String` and returns the byte length of string.

### Class Method: Buffer.compare(buf1, buf2)

* `buf1` {Buffer}
Expand Down Expand Up @@ -1727,3 +1732,5 @@ console.log(buf);
[buffer_allocunsafe]: #buffer_class_method_buffer_allocraw_size
[buffer_alloc]: #buffer_class_method_buffer_alloc_size_fill_encoding
[`TypedArray.from()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/from
[`DataView`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView
[`TypedArray`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
7 changes: 4 additions & 3 deletions lib/buffer.js
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Expand Up @@ -317,11 +317,12 @@ function base64ByteLength(str, bytes) {


function byteLength(string, encoding) {
if (string instanceof Buffer)
return string.length;
if (typeof string !== 'string') {
if (ArrayBuffer.isView(string) || string instanceof ArrayBuffer)
return string.byteLength;

if (typeof string !== 'string')
string = '' + string;
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@jasnell jasnell Mar 22, 2016

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nit: string += '' works too

}

var len = string.length;
if (len === 0)
Expand Down
34 changes: 34 additions & 0 deletions test/parallel/test-buffer-bytelength.js
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Expand Up @@ -3,19 +3,53 @@
require('../common');
var assert = require('assert');
var Buffer = require('buffer').Buffer;
var SlowBuffer = require('buffer').SlowBuffer;

// coerce values to string
assert.equal(Buffer.byteLength(32, 'binary'), 2);
assert.equal(Buffer.byteLength(NaN, 'utf8'), 3);
assert.equal(Buffer.byteLength({}, 'binary'), 15);
assert.equal(Buffer.byteLength(), 9);

var buff = new Buffer(10);
assert(ArrayBuffer.isView(buff));
var slowbuff = new SlowBuffer(10);
assert(ArrayBuffer.isView(slowbuff));

// buffer
var incomplete = Buffer.from([0xe4, 0xb8, 0xad, 0xe6, 0x96]);
assert.equal(Buffer.byteLength(incomplete), 5);
var ascii = Buffer.from('abc');
assert.equal(Buffer.byteLength(ascii), 3);

// ArrayBuffer
var buffer = new ArrayBuffer(8);
assert.equal(Buffer.byteLength(buffer), 8);

// TypedArray
var int8 = new Int8Array(8);
assert.equal(Buffer.byteLength(int8), 8);
var uint8 = new Uint8Array(8);
assert.equal(Buffer.byteLength(uint8), 8);
var uintc8 = new Uint8ClampedArray(2);
assert.equal(Buffer.byteLength(uintc8), 2);
var int16 = new Int16Array(8);
assert.equal(Buffer.byteLength(int16), 16);
var uint16 = new Uint16Array(8);
assert.equal(Buffer.byteLength(uint16), 16);
var int32 = new Int32Array(8);
assert.equal(Buffer.byteLength(int32), 32);
var uint32 = new Uint32Array(8);
assert.equal(Buffer.byteLength(uint32), 32);
var float32 = new Float32Array(8);
assert.equal(Buffer.byteLength(float32), 32);
var float64 = new Float64Array(8);
assert.equal(Buffer.byteLength(float64), 64);

// DataView
var dv = new DataView(new ArrayBuffer(2));
assert.equal(Buffer.byteLength(dv), 2);

// special case: zero length string
assert.equal(Buffer.byteLength('', 'ascii'), 0);
assert.equal(Buffer.byteLength('', 'HeX'), 0);
Expand Down