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buffer: add from(ArrayBufferView) support #43863

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356a0f6
buffer: add from(ArrayBufferView) support
LiviaMedeiros Jul 15, 2022
4ac40d6
squash: test when endianness is big
LiviaMedeiros Jul 17, 2022
ed85f0a
squash: add test
LiviaMedeiros Jul 18, 2022
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buffer: add from(ArrayBufferView) support
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@LiviaMedeiros
LiviaMedeiros committed Jul 16, 2022
commit 356a0f684bc98cbce3051e4a18d8acdd428661c9
12 changes: 8 additions & 4 deletions doc/api/buffer.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1207,10 +1207,14 @@ console.log(buf);

<!-- YAML
added: v5.10.0
changes:
- version: REPLACEME
pr-url: https://github.com/nodejs/node/pull/43863
description: The `buffer` parameter can now be an any `ArrayBufferView`.
-->

* `buffer` {Buffer|Uint8Array} An existing `Buffer` or [`Uint8Array`][] from
which to copy data.
* `buffer` {Buffer|ArrayBufferView} An existing `Buffer`, [`TypedArray`][],
or [`DataView`][] from which to copy data.

Copies the passed `buffer` data onto a new `Buffer` instance.

Expand Down Expand Up @@ -1242,8 +1246,8 @@ console.log(buf2.toString());
// Prints: buffer
```

A `TypeError` will be thrown if `buffer` is not a `Buffer` or another type
appropriate for `Buffer.from()` variants.
A `TypeError` will be thrown if `buffer` is not an `ArrayBufferView`
or another type appropriate for `Buffer.from()` variants.

### Static method: `Buffer.from(object[, offsetOrEncoding[, length]])`

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12 changes: 11 additions & 1 deletion lib/buffer.js
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Expand Up @@ -83,7 +83,8 @@ const {
const {
isAnyArrayBuffer,
isArrayBufferView,
isUint8Array
isTypedArray,
isUint8Array,
} = require('internal/util/types');
const {
inspect: utilInspect
Expand Down Expand Up @@ -306,6 +307,15 @@ Buffer.from = function from(value, encodingOrOffset, length) {
if (isAnyArrayBuffer(value))
return fromArrayBuffer(value, encodingOrOffset, length);

if (isArrayBufferView(value) && !isUint8Array(value)) {
if (!isTypedArray(value)) {
// DataView is not a TypedArray
return fromArrayBuffer(value.buffer.slice(value.byteOffset,
value.byteOffset + value.byteLength));
}
return fromArrayBuffer(value.slice().buffer);
}

const valueOf = value.valueOf && value.valueOf();
if (valueOf != null &&
valueOf !== value &&
Expand Down
66 changes: 58 additions & 8 deletions test/parallel/test-buffer-alloc.js
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Expand Up @@ -59,22 +59,72 @@ assert.strictEqual(d.length, 0);
}

// Test creating a Buffer from a Uint32Array
// Note: it is implicitly interpreted as Array of integers modulo 256
{
const ui32 = new Uint32Array(4).fill(42);
const e = Buffer.from(ui32);
for (const [index, value] of e.entries()) {
assert.strictEqual(value, ui32[index]);
}
assert.deepStrictEqual(e, Buffer.from([
42, 0, 0, 0,
42, 0, 0, 0,
42, 0, 0, 0,
42, 0, 0, 0,
]));
}
// Test creating a Buffer from a Uint32Array (old constructor)
// Note: it is implicitly interpreted as Array of integers modulo 256
{
const ui32 = new Uint32Array(4).fill(42);
const e = Buffer(ui32);
for (const [key, value] of e.entries()) {
assert.strictEqual(value, ui32[key]);
}
assert.deepStrictEqual(e, Buffer.from([
42, 0, 0, 0,
42, 0, 0, 0,
42, 0, 0, 0,
42, 0, 0, 0,
]));
}

// Test creating a Buffer from a BigUint64Array
{
const bui64 = new BigUint64Array(4).fill(42n);
const e = Buffer.from(bui64);
assert.deepStrictEqual(e, Buffer.from([
42, 0, 0, 0, 0, 0, 0, 0,
42, 0, 0, 0, 0, 0, 0, 0,
42, 0, 0, 0, 0, 0, 0, 0,
42, 0, 0, 0, 0, 0, 0, 0,
]));
}
// Test creating a Buffer from a BigUint64Array (old constructor)
{
const bui64 = new BigUint64Array(4).fill(42n);
const e = Buffer(bui64);
assert.deepStrictEqual(e, Buffer.from([
42, 0, 0, 0, 0, 0, 0, 0,
42, 0, 0, 0, 0, 0, 0, 0,
42, 0, 0, 0, 0, 0, 0, 0,
42, 0, 0, 0, 0, 0, 0, 0,
]));
}

// Test creating a Buffer from a Float64Array
{
const f64 = new Float64Array(4).fill(42);
const e = Buffer.from(f64);
assert.deepStrictEqual(e, Buffer.from([
0, 0, 0, 0, 0, 0, 69, 64,
0, 0, 0, 0, 0, 0, 69, 64,
0, 0, 0, 0, 0, 0, 69, 64,
0, 0, 0, 0, 0, 0, 69, 64,
]));
}
// Test creating a Buffer from a Float64Array (old constructor)
{
const f64 = new Float64Array(4).fill(42);
const e = Buffer(f64);
assert.deepStrictEqual(e, Buffer.from([
0, 0, 0, 0, 0, 0, 69, 64,
0, 0, 0, 0, 0, 0, 69, 64,
0, 0, 0, 0, 0, 0, 69, 64,
0, 0, 0, 0, 0, 0, 69, 64,
]));
}

// Test invalid encoding for Buffer.toString
Expand Down