# safe-buffer [![travis][travis-image]][travis-url] [![npm][npm-image]][npm-url] [![downloads][downloads-image]][downloads-url] [![javas
cript style guide][standard-image]][standard-url]
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#### Safer Node.js Buffer API
**Use the new Node.js Buffer APIs (`Buffer.from`, `Buffer.alloc`,
`Buffer.allocUnsafe`, `Buffer.allocUnsafeSlow`) in all versions of Node.js.**
**Uses the built-in implementation when available.**
## install
```
npm install safe-buffer
```
## usage
The goal of this package is to provide a safe replac
ement for the node.js `Buffer`.
It's a drop-in replacement for `Buffer`. You can use it by adding one `require` line to
the top of your node.js modules:
```js
var Buffer = require('safe-buffer').Buffer
// Existing buffer code will co
ntinue to work without issues:
new Buffer('hey', 'utf8')
new Buffer([1, 2, 3], 'utf8')
new Buffer(obj)
new Buffer(16) // create an uninitialized buffer (potentially unsafe)
// But you can use these new explicit APIs to make clear what you want:
Buffer.from('hey', 'utf8') // co
nvert from many types to a Buffer
Buffer.alloc(16) // create a zero-filled buffer (safe)
Buffer.allocUnsafe(16) // create an uninitialized buffer (potentially unsafe)
```
## api
### Class Method: Buffer.from(array)
<!-- YAML
added: v3.0.0
-->
* `array` {Array}
Allocates a new `Buffer` using an `array` of octets.
```js
co
nst buf = Buffer.from([0
x62,0
x75,0
x66,0
x66,0
x65,0
x72]);
// creates a new Buffer co
ntaining ASCII bytes
// ['b','u','f','f','e','r']
```
A `TypeError` will be thrown if `array` is not an `Array`.
### Class Method: Buffer.from(arrayBuffer[, byteOffset[, length]])
<!-- YAML
added: v5.10.0
-->
* `arrayBuffer` {ArrayBuffer} The `.buffer` property of a `TypedArray` or
a `new ArrayBuffer()`
* `byteOffset` {Number} Default: `0`
* `length` {Number} Default: `arrayBuffer.length - byteOffset`
When passed a reference to the `.buffer` property of a `TypedArray` instance,
the newly created `Buffer` will share the same allocated memory as the
TypedArray.
```js
co
nst arr = new Uint16Array(2);
arr[0] = 5000;
arr[1] = 4000;
co
nst buf = Buffer.from(arr.buffer); // shares the memory with arr;
console.log(buf);
// Prints: <Buffer 88 13 a0 0f>
// changing the TypedArray changes the Buffer also
arr[1] = 6000;
console.log(buf);
// Prints: <Buffer 88 13 70 17>
```
The optio
nal `byteOffset` and `length` arguments specify a memory range within
the `arrayBuffer` that will be shared by the `Buffer`.
```js
co
nst ab = new ArrayBuffer(10);
co
nst buf = Buffer.from(ab, 0, 2);
console.log(buf.length);
// Prints: 2
```
A `TypeError` will be thrown if `arrayBuffer` is not an `ArrayBuffer`.
### Class Method: Buffer.from(buffer)
<!-- YAML
added: v3.0.0
-->
* `buffer` {Buffer}
Copies the passed `buffer` data o
nto a new `Buffer` instance.
```js
co
nst buf1 = Buffer.from('buffer');
co
nst buf2 = Buffer.from(buf1);
buf1[0] = 0
x61;
console.log(buf1.toString());
// 'auffer'
console.log(buf2.toString());
// 'buffer' (copy is not changed)
```
A `TypeError` will be thrown if `buffer` is not a `Buffer`.
### Class Method: Buffer.from(str[, encoding])
<!-- YAML
added: v5.10.0
-->
* `str` {String} String to encode.
* `encoding` {String} Encoding to use, Default: `'utf8'`
Creates a new `Buffer` co
ntaining the given JavaS
cript string `str`. If
provided, the `encoding` parameter identifies the character encoding.
If not provided, `encoding` defaults to `'utf8'`.
```js
co
nst buf1 = Buffer.from('this is a tést');
console.log(buf1.toString());
// prints: this is a tést
console.log(buf1.toString('ascii'));
// prints: this is a tC)st
co
nst buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');
console.log(buf2.toString());
// prints: this is a tést
```
A `TypeError` will be thrown if `str` is not a string.
### Class Method: Buffer.alloc(size[, fill[, encoding]])
<!-- YAML
added: v5.10.0
-->
* `size` {Number}
* `fill` {Value} Default: `undefined`
* `encoding` {String} Default: `utf8`
Allocates a new `Buffer` of `size` bytes. If `fill` is `undefined`, the
`Buffer` will be *zero-filled*.
```js
co
nst buf = Buffer.alloc(5);
console.log(buf);
// <Buffer 00 00 00 00 00>
```
The `size` must be less than or equal to the value of
`require('buffer').kMaxLength` (on 64-bit architectures, `kMaxLength` is
`(2^31)-1`). Otherwise, a [`RangeError`][] is thrown. A zero-length Buffer will
be created if a `size` less than or equal to 0 is specified.
If `fill` is specified, the allocated `Buffer` will be initialized by calling
`buf.fill(fill)`. See [`buf.fill()`][] for more information.
```js
co
nst buf = Buffer.alloc(5, 'a');
console.log(buf);
// <Buffer 61 61 61 61 61>
```
If both `fill` and `encoding` are specified, the allocated `Buffer` will be
initialized by calling `buf.fill(fill, encoding)`. For example:
```js
co
nst buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'b
ase64');
console.log(buf);
// <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>
```
Calling `Buffer.alloc(size)` can be significantly slower than the alternative
`Buffer.allocUnsafe(size)` but ensures that the newly created `Buffer` instance
co
ntents will *never co
ntain sensitive data*.
A `TypeError` will be thrown if `size` is not a number.
### Class Method: Buffer.allocUnsafe(size)
<!-- YAML
added: v5.10.0
-->
* `size` {Number}
Allocates a new *non-zero-filled* `Buffer` of `size` bytes. The `size` must
be less than or equal to the value of `require('buffer').kMaxLength` (on 64-bit
architectures, `kMaxLength` is `(2^31)-1`). Otherwise, a [`RangeError`][] is
thrown. A zero-length Buffer will be created if a `size` less than or equal to
0 is specified.
The underlying memory for `Buffer` instances created in this way is *not
initialized*. The co
ntents of the newly created `Buffer` are unknown and
*may co
ntain sensitive data*. Use [`buf.fill(0)`][] to initialize such
`Buffer` instances to zeroes.
```js
co
nst buf = Buffer.allocUnsafe(5);
console.log(buf);
// <Buffer 78 e0 82 02 01>
// (octets will be different, every time)
buf.fill(0);
console.log(buf);
// <Buffer 00 00 00 00 00>
```
A `TypeError` will be thrown if `size` is not a number.
Note that the `Buffer` module pre-allocates an internal `Buffer` instance of
size `Buffer.poolSize` that is used as a pool for the fast allocation of new
`Buffer` instances created using `Buffer.allocUnsafe(size)` (and the deprecated
`new Buffer(size)` constructor) o
nly when `size` is less than or equal to
`Buffer.poolSize >> 1` (floor of `Buffer.poolSize` divided by two). The default
value of `Buffer.poolSize` is `8192` but can be modified.
Use of this pre-allocated internal memory pool is a key difference between
calling `Buffer.alloc(size, fill)` vs. `Buffer.allocUnsafe(size).fill(fill)`.
Specifically, `Buffer.alloc(size, fill)` will *never* use the internal Buffer
pool, while `Buffer.allocUnsafe(size).fill(fill)` *will* use the internal
Buffer pool if `size` is less than or equal to half `Buffer.poolSize`. The
difference is subtle but can be i
mportant when an application requires the
additio
nal performance that `Buffer.allocUnsafe(size)` provides.
### Class Method: Buffer.allocUnsafeSlow(size)
<!-- YAML
added: v5.10.0
-->
* `size` {Number}
Allocates a new *non-zero-filled* and non-pooled `Buffer` of `size` bytes. The
`size` must be less than or equal to the value of
`require('buffer').kMaxLength` (on 64-bit architectures, `kMaxLength` is
`(2^31)-1`). Otherwise, a [`RangeError`][] is thrown. A zero-length Buffer will
