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doc: add Buffer#subarray() and add note about Uint8Array#slice()

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PR-URL: https://github.com/nodejs/node/pull/28101
Refs: https://github.com/nodejs/node/issues/28087
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
This commit is contained in:
FUJI Goro (gfx) 2019-06-06 22:43:22 +09:00 committed by Rich Trott
parent 0a3885e8a7
commit ee167877ad
1 changed files with 49 additions and 18 deletions
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67
doc/api/buffer.md
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@ -1896,18 +1896,9 @@ console.log(buf.readUIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE. // Throws ERR_OUT_OF_RANGE.
``` ```
### buf.slice([start[, end]]) ### buf.subarray([start[, end]])
<!-- YAML <!-- YAML
added: v0.3.0 added: v3.0.0
changes:
- version: v7.1.0, v6.9.2
pr-url: https://github.com/nodejs/node/pull/9341
description: Coercing the offsets to integers now handles values outside
the 32-bit integer range properly.
- version: v7.0.0
pr-url: https://github.com/nodejs/node/pull/9101
description: All offsets are now coerced to integers before doing any
calculations with them.
--> -->
* `start` {integer} Where the new `Buffer` will start. **Default:** `0`. * `start` {integer} Where the new `Buffer` will start. **Default:** `0`.
@ -1935,7 +1926,7 @@ for (let i = 0; i < 26; i++) {
buf1[i] = i + 97; buf1[i] = i + 97;
} }
const buf2 = buf1.slice(0, 3); const buf2 = buf1.subarray(0, 3);
console.log(buf2.toString('ascii', 0, buf2.length)); console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: abc // Prints: abc
@ -1952,17 +1943,57 @@ end of `buf` rather than the beginning.
```js ```js
const buf = Buffer.from('buffer'); const buf = Buffer.from('buffer');
console.log(buf.slice(-6, -1).toString()); console.log(buf.subarray(-6, -1).toString());
// Prints: buffe // Prints: buffe
// (Equivalent to buf.slice(0, 5).) // (Equivalent to buf.subarray(0, 5).)
console.log(buf.slice(-6, -2).toString()); console.log(buf.subarray(-6, -2).toString());
// Prints: buff // Prints: buff
// (Equivalent to buf.slice(0, 4).) // (Equivalent to buf.subarray(0, 4).)
console.log(buf.slice(-5, -2).toString()); console.log(buf.subarray(-5, -2).toString());
// Prints: uff // Prints: uff
// (Equivalent to buf.slice(1, 4).) // (Equivalent to buf.subarray(1, 4).)
```
### buf.slice([start[, end]])
<!-- YAML
added: v0.3.0
changes:
- version: v7.1.0, v6.9.2
pr-url: https://github.com/nodejs/node/pull/9341
description: Coercing the offsets to integers now handles values outside
the 32-bit integer range properly.
- version: v7.0.0
pr-url: https://github.com/nodejs/node/pull/9101
description: All offsets are now coerced to integers before doing any
calculations with them.
-->
* `start` {integer} Where the new `Buffer` will start. **Default:** `0`.
* `end` {integer} Where the new `Buffer` will end (not inclusive).
**Default:** [`buf.length`][].
* Returns: {Buffer}
Returns a new `Buffer` that references the same memory as the original, but
offset and cropped by the `start` and `end` indices.
This is the same behavior as `buf.subarray()`.
This method is not compatible with the `Uint8Array.prototype.slice()`,
which is a superclass of `Buffer`. To copy the slice, use
`Uint8Array.prototype.slice()`.
```js
const buf = Buffer.from('buffer');
const copiedBuf = Uint8Array.prototype.slice.call(buf);
copiedBuf[0]++;
console.log(copiedBuf.toString());
// Prints: cuffer
console.log(buf.toString());
// Prints: buffer
``` ```
### buf.swap16() ### buf.swap16()