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The use of dashes -- in general, but especially in our docs -- can be problematic. It is used inconsistently and there is always another form of punctuation that is as good or better for the situation. In an effort to reduce the number of variations we use to display the same types of information, remove the various uses of dashes from the documentation. PR-URL: https://github.com/nodejs/node/pull/30101 Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: Richard Lau <riclau@uk.ibm.com> Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>
2852 lines
88 KiB
Markdown
2852 lines
88 KiB
Markdown
# Buffer
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<!--introduced_in=v0.1.90-->
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> Stability: 2 - Stable
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Prior to the introduction of [`TypedArray`][], the JavaScript language had no
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mechanism for reading or manipulating streams of binary data. The `Buffer` class
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was introduced as part of the Node.js API to enable interaction with octet
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streams in TCP streams, file system operations, and other contexts.
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With [`TypedArray`][] now available, the `Buffer` class implements the
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[`Uint8Array`][] API in a manner that is more optimized and suitable for
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Node.js.
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Instances of the `Buffer` class are similar to arrays of integers from `0` to
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`255` (other integers are coerced to this range by `& 255` operation) but
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correspond to fixed-sized, raw memory allocations outside the V8 heap.
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The size of the `Buffer` is established when it is created and cannot be
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changed.
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The `Buffer` class is within the global scope, making it unlikely that one
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would need to ever use `require('buffer').Buffer`.
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```js
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// Creates a zero-filled Buffer of length 10.
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const buf1 = Buffer.alloc(10);
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// Creates a Buffer of length 10, filled with 0x1.
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const buf2 = Buffer.alloc(10, 1);
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// Creates an uninitialized buffer of length 10.
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// This is faster than calling Buffer.alloc() but the returned
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// Buffer instance might contain old data that needs to be
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// overwritten using either fill() or write().
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const buf3 = Buffer.allocUnsafe(10);
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// Creates a Buffer containing [0x1, 0x2, 0x3].
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const buf4 = Buffer.from([1, 2, 3]);
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// Creates a Buffer containing UTF-8 bytes [0x74, 0xc3, 0xa9, 0x73, 0x74].
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const buf5 = Buffer.from('tést');
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// Creates a Buffer containing Latin-1 bytes [0x74, 0xe9, 0x73, 0x74].
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const buf6 = Buffer.from('tést', 'latin1');
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```
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## `Buffer.from()`, `Buffer.alloc()`, and `Buffer.allocUnsafe()`
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In versions of Node.js prior to 6.0.0, `Buffer` instances were created using the
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`Buffer` constructor function, which allocates the returned `Buffer`
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differently based on what arguments are provided:
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* Passing a number as the first argument to `Buffer()` (e.g. `new Buffer(10)`)
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allocates a new `Buffer` object of the specified size. Prior to Node.js 8.0.0,
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the memory allocated for such `Buffer` instances is *not* initialized and
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*can contain sensitive data*. Such `Buffer` instances *must* be subsequently
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initialized by using either [`buf.fill(0)`][`buf.fill()`] or by writing to the
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entire `Buffer`. While this behavior is *intentional* to improve performance,
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development experience has demonstrated that a more explicit distinction is
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required between creating a fast-but-uninitialized `Buffer` versus creating a
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slower-but-safer `Buffer`. Since Node.js 8.0.0, `Buffer(num)` and `new
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Buffer(num)` return a `Buffer` with initialized memory.
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* Passing a string, array, or `Buffer` as the first argument copies the
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passed object's data into the `Buffer`.
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* Passing an [`ArrayBuffer`][] or a [`SharedArrayBuffer`][] returns a `Buffer`
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that shares allocated memory with the given array buffer.
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Because the behavior of `new Buffer()` is different depending on the type of the
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first argument, security and reliability issues can be inadvertently introduced
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into applications when argument validation or `Buffer` initialization is not
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performed.
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For example, if an attacker can cause an application to receive a number where
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a string is expected, the application may call `new Buffer(100)`
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instead of `new Buffer("100")`, it will allocate a 100 byte buffer instead
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of allocating a 3 byte buffer with content `"100"`. This is commonly possible
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using JSON API calls. Since JSON distinguishes between numeric and string types,
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it allows injection of numbers where a naive application might expect to always
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receive a string. Before Node.js 8.0.0, the 100 byte buffer might contain
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arbitrary pre-existing in-memory data, so may be used to expose in-memory
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secrets to a remote attacker. Since Node.js 8.0.0, exposure of memory cannot
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occur because the data is zero-filled. However, other attacks are still
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possible, such as causing very large buffers to be allocated by the server,
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leading to performance degradation or crashing on memory exhaustion.
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To make the creation of `Buffer` instances more reliable and less error-prone,
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the various forms of the `new Buffer()` constructor have been **deprecated**
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and replaced by separate `Buffer.from()`, [`Buffer.alloc()`][], and
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[`Buffer.allocUnsafe()`][] methods.
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*Developers should migrate all existing uses of the `new Buffer()` constructors
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to one of these new APIs.*
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* [`Buffer.from(array)`][] returns a new `Buffer` that *contains a copy* of the
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provided octets.
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* [`Buffer.from(arrayBuffer[, byteOffset[, length]])`][`Buffer.from(arrayBuf)`]
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returns a new `Buffer` that *shares the same allocated memory* as the given
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[`ArrayBuffer`][].
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* [`Buffer.from(buffer)`][] returns a new `Buffer` that *contains a copy* of the
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contents of the given `Buffer`.
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* [`Buffer.from(string[, encoding])`][`Buffer.from(string)`] returns a new
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`Buffer` that *contains a copy* of the provided string.
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* [`Buffer.alloc(size[, fill[, encoding]])`][`Buffer.alloc()`] returns a new
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initialized `Buffer` of the specified size. This method is slower than
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[`Buffer.allocUnsafe(size)`][`Buffer.allocUnsafe()`] but guarantees that newly
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created `Buffer` instances never contain old data that is potentially
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sensitive. A `TypeError` will be thrown if `size` is not a number.
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* [`Buffer.allocUnsafe(size)`][`Buffer.allocUnsafe()`] and
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[`Buffer.allocUnsafeSlow(size)`][`Buffer.allocUnsafeSlow()`] each return a
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new uninitialized `Buffer` of the specified `size`. Because the `Buffer` is
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uninitialized, the allocated segment of memory might contain old data that is
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potentially sensitive.
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`Buffer` instances returned by [`Buffer.allocUnsafe()`][] *may* be allocated off
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a shared internal memory pool if `size` is less than or equal to half
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[`Buffer.poolSize`][]. Instances returned by [`Buffer.allocUnsafeSlow()`][]
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*never* use the shared internal memory pool.
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### The `--zero-fill-buffers` command line option
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<!-- YAML
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added: v5.10.0
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-->
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Node.js can be started using the `--zero-fill-buffers` command line option to
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cause all newly allocated `Buffer` instances to be zero-filled upon creation by
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default. Before Node.js 8.0.0, this included buffers allocated by `new
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Buffer(size)`. Since Node.js 8.0.0, buffers allocated with `new` are always
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zero-filled, whether this option is used or not.
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[`Buffer.allocUnsafe()`][], [`Buffer.allocUnsafeSlow()`][], and `new
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SlowBuffer(size)`. Use of this flag can have a significant negative impact on
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performance. Use of the `--zero-fill-buffers` option is recommended only when
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necessary to enforce that newly allocated `Buffer` instances cannot contain old
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data that is potentially sensitive.
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```console
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$ node --zero-fill-buffers
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> Buffer.allocUnsafe(5);
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<Buffer 00 00 00 00 00>
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```
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### What makes `Buffer.allocUnsafe()` and `Buffer.allocUnsafeSlow()` "unsafe"?
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When calling [`Buffer.allocUnsafe()`][] and [`Buffer.allocUnsafeSlow()`][], the
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segment of allocated memory is *uninitialized* (it is not zeroed-out). While
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this design makes the allocation of memory quite fast, the allocated segment of
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memory might contain old data that is potentially sensitive. Using a `Buffer`
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created by [`Buffer.allocUnsafe()`][] without *completely* overwriting the
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memory can allow this old data to be leaked when the `Buffer` memory is read.
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While there are clear performance advantages to using
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[`Buffer.allocUnsafe()`][], extra care *must* be taken in order to avoid
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introducing security vulnerabilities into an application.
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## Buffers and Character Encodings
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<!-- YAML
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changes:
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- version: v6.4.0
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pr-url: https://github.com/nodejs/node/pull/7111
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description: Introduced `latin1` as an alias for `binary`.
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- version: v5.0.0
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pr-url: https://github.com/nodejs/node/pull/2859
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description: Removed the deprecated `raw` and `raws` encodings.
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-->
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When string data is stored in or extracted out of a `Buffer` instance, a
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character encoding may be specified.
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```js
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const buf = Buffer.from('hello world', 'ascii');
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console.log(buf.toString('hex'));
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// Prints: 68656c6c6f20776f726c64
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console.log(buf.toString('base64'));
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// Prints: aGVsbG8gd29ybGQ=
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console.log(Buffer.from('fhqwhgads', 'ascii'));
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// Prints: <Buffer 66 68 71 77 68 67 61 64 73>
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console.log(Buffer.from('fhqwhgads', 'utf16le'));
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// Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00>
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```
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The character encodings currently supported by Node.js include:
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* `'ascii'`: For 7-bit ASCII data only. This encoding is fast and will strip
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the high bit if set.
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* `'utf8'`: Multibyte encoded Unicode characters. Many web pages and other
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document formats use UTF-8.
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* `'utf16le'`: 2 or 4 bytes, little-endian encoded Unicode characters.
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Surrogate pairs (U+10000 to U+10FFFF) are supported.
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* `'ucs2'`: Alias of `'utf16le'`.
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* `'base64'`: Base64 encoding. When creating a `Buffer` from a string,
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this encoding will also correctly accept "URL and Filename Safe Alphabet" as
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specified in [RFC 4648, Section 5][].
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* `'latin1'`: A way of encoding the `Buffer` into a one-byte encoded string
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(as defined by the IANA in [RFC 1345][],
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page 63, to be the Latin-1 supplement block and C0/C1 control codes).
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* `'binary'`: Alias for `'latin1'`.
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* `'hex'`: Encode each byte as two hexadecimal characters.
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Modern Web browsers follow the [WHATWG Encoding Standard][] which aliases
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both `'latin1'` and `'ISO-8859-1'` to `'win-1252'`. This means that while doing
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something like `http.get()`, if the returned charset is one of those listed in
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the WHATWG specification it is possible that the server actually returned
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`'win-1252'`-encoded data, and using `'latin1'` encoding may incorrectly decode
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the characters.
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## Buffers and TypedArray
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<!-- YAML
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changes:
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- version: v3.0.0
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pr-url: https://github.com/nodejs/node/pull/2002
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description: The `Buffer`s class now inherits from `Uint8Array`.
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-->
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`Buffer` instances are also [`Uint8Array`][] instances. However, there are
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subtle incompatibilities with [`TypedArray`][]. For example, while
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[`ArrayBuffer#slice()`][] creates a copy of the slice, the implementation of
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[`Buffer#slice()`][`buf.slice()`] creates a view over the existing `Buffer`
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without copying, making [`Buffer#slice()`][`buf.slice()`] far more efficient.
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It is also possible to create new [`TypedArray`][] instances from a `Buffer`
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with the following caveats:
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1. The `Buffer` object's memory is copied to the [`TypedArray`][], not shared.
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2. The `Buffer` object's memory is interpreted as an array of distinct
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elements, and not as a byte array of the target type. That is,
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`new Uint32Array(Buffer.from([1, 2, 3, 4]))` creates a 4-element
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[`Uint32Array`][] with elements `[1, 2, 3, 4]`, not a [`Uint32Array`][] with a
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single element `[0x1020304]` or `[0x4030201]`.
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It is possible to create a new `Buffer` that shares the same allocated memory as
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a [`TypedArray`][] instance by using the `TypedArray` object's `.buffer`
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property.
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```js
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const arr = new Uint16Array(2);
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arr[0] = 5000;
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arr[1] = 4000;
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// Copies the contents of `arr`.
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const buf1 = Buffer.from(arr);
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// Shares memory with `arr`.
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const buf2 = Buffer.from(arr.buffer);
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console.log(buf1);
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// Prints: <Buffer 88 a0>
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console.log(buf2);
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// Prints: <Buffer 88 13 a0 0f>
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arr[1] = 6000;
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console.log(buf1);
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// Prints: <Buffer 88 a0>
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console.log(buf2);
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// Prints: <Buffer 88 13 70 17>
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```
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When creating a `Buffer` using a [`TypedArray`][]'s `.buffer`, it is
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possible to use only a portion of the underlying [`ArrayBuffer`][] by passing in
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`byteOffset` and `length` parameters.
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```js
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const arr = new Uint16Array(20);
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const buf = Buffer.from(arr.buffer, 0, 16);
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console.log(buf.length);
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// Prints: 16
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```
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The `Buffer.from()` and [`TypedArray.from()`][] have different signatures and
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implementations. Specifically, the [`TypedArray`][] variants accept a second
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argument that is a mapping function that is invoked on every element of the
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typed array:
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* `TypedArray.from(source[, mapFn[, thisArg]])`
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The `Buffer.from()` method, however, does not support the use of a mapping
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function:
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* [`Buffer.from(array)`][]
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* [`Buffer.from(buffer)`][]
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* [`Buffer.from(arrayBuffer[, byteOffset[, length]])`][`Buffer.from(arrayBuf)`]
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* [`Buffer.from(string[, encoding])`][`Buffer.from(string)`]
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## Buffers and iteration
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`Buffer` instances can be iterated over using `for..of` syntax:
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```js
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const buf = Buffer.from([1, 2, 3]);
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for (const b of buf) {
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console.log(b);
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}
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// Prints:
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// 1
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// 2
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// 3
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```
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Additionally, the [`buf.values()`][], [`buf.keys()`][], and
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[`buf.entries()`][] methods can be used to create iterators.
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## Class: Buffer
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The `Buffer` class is a global type for dealing with binary data directly.
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It can be constructed in a variety of ways.
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### new Buffer(array)
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<!-- YAML
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deprecated: v6.0.0
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changes:
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- version: v10.0.0
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pr-url: https://github.com/nodejs/node/pull/19524
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description: Calling this constructor emits a deprecation warning when
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run from code outside the `node_modules` directory.
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- version: v7.2.1
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pr-url: https://github.com/nodejs/node/pull/9529
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description: Calling this constructor no longer emits a deprecation warning.
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- version: v7.0.0
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pr-url: https://github.com/nodejs/node/pull/8169
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description: Calling this constructor emits a deprecation warning now.
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-->
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> Stability: 0 - Deprecated: Use [`Buffer.from(array)`][] instead.
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* `array` {integer[]} An array of bytes to copy from.
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Allocates a new `Buffer` using an `array` of octets.
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```js
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// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'.
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const buf = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);
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```
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### new Buffer(arrayBuffer\[, byteOffset\[, length\]\])
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<!-- YAML
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added: v3.0.0
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deprecated: v6.0.0
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changes:
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- version: v10.0.0
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pr-url: https://github.com/nodejs/node/pull/19524
|
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description: Calling this constructor emits a deprecation warning when
|
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run from code outside the `node_modules` directory.
|
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- version: v7.2.1
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pr-url: https://github.com/nodejs/node/pull/9529
|
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description: Calling this constructor no longer emits a deprecation warning.
|
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- version: v7.0.0
|
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pr-url: https://github.com/nodejs/node/pull/8169
|
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description: Calling this constructor emits a deprecation warning now.
|
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- version: v6.0.0
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pr-url: https://github.com/nodejs/node/pull/4682
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description: The `byteOffset` and `length` parameters are supported now.
|
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-->
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> Stability: 0 - Deprecated: Use
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> [`Buffer.from(arrayBuffer[, byteOffset[, length]])`][`Buffer.from(arrayBuf)`]
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> instead.
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* `arrayBuffer` {ArrayBuffer|SharedArrayBuffer} An [`ArrayBuffer`][],
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[`SharedArrayBuffer`][] or the `.buffer` property of a [`TypedArray`][].
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* `byteOffset` {integer} Index of first byte to expose. **Default:** `0`.
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* `length` {integer} Number of bytes to expose.
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**Default:** `arrayBuffer.length - byteOffset`.
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This creates a view of the [`ArrayBuffer`][] or [`SharedArrayBuffer`][] without
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copying the underlying memory. For example, when passed a reference to the
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`.buffer` property of a [`TypedArray`][] instance, the newly created `Buffer`
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will share the same allocated memory as the [`TypedArray`][].
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The optional `byteOffset` and `length` arguments specify a memory range within
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the `arrayBuffer` that will be shared by the `Buffer`.
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```js
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const arr = new Uint16Array(2);
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arr[0] = 5000;
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arr[1] = 4000;
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// Shares memory with `arr`.
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const buf = new Buffer(arr.buffer);
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console.log(buf);
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// Prints: <Buffer 88 13 a0 0f>
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// Changing the original Uint16Array changes the Buffer also.
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arr[1] = 6000;
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console.log(buf);
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// Prints: <Buffer 88 13 70 17>
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```
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|
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### new Buffer(buffer)
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<!-- YAML
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|
deprecated: v6.0.0
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/19524
|
|
description: Calling this constructor emits a deprecation warning when
|
|
run from code outside the `node_modules` directory.
|
|
- version: v7.2.1
|
|
pr-url: https://github.com/nodejs/node/pull/9529
|
|
description: Calling this constructor no longer emits a deprecation warning.
|
|
- version: v7.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/8169
|
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description: Calling this constructor emits a deprecation warning now.
|
|
-->
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> Stability: 0 - Deprecated: Use [`Buffer.from(buffer)`][] instead.
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* `buffer` {Buffer|Uint8Array} An existing `Buffer` or [`Uint8Array`][] from
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which to copy data.
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Copies the passed `buffer` data onto a new `Buffer` instance.
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```js
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const buf1 = new Buffer('buffer');
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const buf2 = new Buffer(buf1);
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buf1[0] = 0x61;
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console.log(buf1.toString());
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// Prints: auffer
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console.log(buf2.toString());
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// Prints: buffer
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```
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|
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### new Buffer(size)
|
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<!-- YAML
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|
deprecated: v6.0.0
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/19524
|
|
description: Calling this constructor emits a deprecation warning when
|
|
run from code outside the `node_modules` directory.
|
|
- version: v8.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/12141
|
|
description: The `new Buffer(size)` will return zero-filled memory by
|
|
default.
|
|
- version: v7.2.1
|
|
pr-url: https://github.com/nodejs/node/pull/9529
|
|
description: Calling this constructor no longer emits a deprecation warning.
|
|
- version: v7.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/8169
|
|
description: Calling this constructor emits a deprecation warning now.
|
|
-->
|
|
|
|
> Stability: 0 - Deprecated: Use [`Buffer.alloc()`][] instead (also see
|
|
> [`Buffer.allocUnsafe()`][]).
|
|
|
|
* `size` {integer} The desired length of the new `Buffer`.
|
|
|
|
Allocates a new `Buffer` of `size` bytes. If `size` is larger than
|
|
[`buffer.constants.MAX_LENGTH`][] or smaller than 0, [`ERR_INVALID_OPT_VALUE`][]
|
|
is thrown. A zero-length `Buffer` is created if `size` is 0.
|
|
|
|
Prior to Node.js 8.0.0, the underlying memory for `Buffer` instances
|
|
created in this way is *not initialized*. The contents of a newly created
|
|
`Buffer` are unknown and *may contain sensitive data*. Use
|
|
[`Buffer.alloc(size)`][`Buffer.alloc()`] instead to initialize a `Buffer`
|
|
with zeroes.
|
|
|
|
```js
|
|
const buf = new Buffer(10);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>
|
|
```
|
|
|
|
### new Buffer(string\[, encoding\])
|
|
<!-- YAML
|
|
deprecated: v6.0.0
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/19524
|
|
description: Calling this constructor emits a deprecation warning when
|
|
run from code outside the `node_modules` directory.
|
|
- version: v7.2.1
|
|
pr-url: https://github.com/nodejs/node/pull/9529
|
|
description: Calling this constructor no longer emits a deprecation warning.
|
|
- version: v7.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/8169
|
|
description: Calling this constructor emits a deprecation warning now.
|
|
-->
|
|
|
|
> Stability: 0 - Deprecated:
|
|
> Use [`Buffer.from(string[, encoding])`][`Buffer.from(string)`] instead.
|
|
|
|
* `string` {string} String to encode.
|
|
* `encoding` {string} The encoding of `string`. **Default:** `'utf8'`.
|
|
|
|
Creates a new `Buffer` containing `string`. The `encoding` parameter identifies
|
|
the character encoding of `string`.
|
|
|
|
```js
|
|
const buf1 = new Buffer('this is a tést');
|
|
const buf2 = new Buffer('7468697320697320612074c3a97374', 'hex');
|
|
|
|
console.log(buf1.toString());
|
|
// Prints: this is a tést
|
|
console.log(buf2.toString());
|
|
// Prints: this is a tést
|
|
console.log(buf1.toString('ascii'));
|
|
// Prints: this is a tC)st
|
|
```
|
|
|
|
### Class Method: Buffer.alloc(size\[, fill\[, encoding\]\])
|
|
<!-- YAML
|
|
added: v5.10.0
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18129
|
|
description: Attempting to fill a non-zero length buffer with a zero length
|
|
buffer triggers a thrown exception.
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/17427
|
|
description: Specifying an invalid string for `fill` triggers a thrown
|
|
exception.
|
|
- version: v8.9.3
|
|
pr-url: https://github.com/nodejs/node/pull/17428
|
|
description: Specifying an invalid string for `fill` now results in a
|
|
zero-filled buffer.
|
|
-->
|
|
|
|
* `size` {integer} The desired length of the new `Buffer`.
|
|
* `fill` {string|Buffer|Uint8Array|integer} A value to pre-fill the new `Buffer`
|
|
with. **Default:** `0`.
|
|
* `encoding` {string} If `fill` is a string, this is its encoding.
|
|
**Default:** `'utf8'`.
|
|
|
|
Allocates a new `Buffer` of `size` bytes. If `fill` is `undefined`, the
|
|
`Buffer` will be *zero-filled*.
|
|
|
|
```js
|
|
const buf = Buffer.alloc(5);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 00 00 00 00 00>
|
|
```
|
|
|
|
If `size` is larger than
|
|
[`buffer.constants.MAX_LENGTH`][] or smaller than 0, [`ERR_INVALID_OPT_VALUE`][]
|
|
is thrown. A zero-length `Buffer` is created if `size` is 0.
|
|
|
|
If `fill` is specified, the allocated `Buffer` will be initialized by calling
|
|
[`buf.fill(fill)`][`buf.fill()`].
|
|
|
|
```js
|
|
const buf = Buffer.alloc(5, 'a');
|
|
|
|
console.log(buf);
|
|
// Prints: <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)`][`buf.fill()`].
|
|
|
|
```js
|
|
const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>
|
|
```
|
|
|
|
Calling [`Buffer.alloc()`][] can be significantly slower than the alternative
|
|
[`Buffer.allocUnsafe()`][] but ensures that the newly created `Buffer` instance
|
|
contents will *never contain sensitive data*.
|
|
|
|
A `TypeError` will be thrown if `size` is not a number.
|
|
|
|
### Class Method: Buffer.allocUnsafe(size)
|
|
<!-- YAML
|
|
added: v5.10.0
|
|
changes:
|
|
- version: v7.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/7079
|
|
description: Passing a negative `size` will now throw an error.
|
|
-->
|
|
|
|
* `size` {integer} The desired length of the new `Buffer`.
|
|
|
|
Allocates a new `Buffer` of `size` bytes. If `size` is larger than
|
|
[`buffer.constants.MAX_LENGTH`][] or smaller than 0, [`ERR_INVALID_OPT_VALUE`][]
|
|
is thrown. A zero-length `Buffer` is created if `size` is 0.
|
|
|
|
The underlying memory for `Buffer` instances created in this way is *not
|
|
initialized*. The contents of the newly created `Buffer` are unknown and
|
|
*may contain sensitive data*. Use [`Buffer.alloc()`][] instead to initialize
|
|
`Buffer` instances with zeroes.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(10);
|
|
|
|
console.log(buf);
|
|
// Prints (contents may vary): <Buffer a0 8b 28 3f 01 00 00 00 50 32>
|
|
|
|
buf.fill(0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>
|
|
```
|
|
|
|
A `TypeError` will be thrown if `size` is not a number.
|
|
|
|
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()`][] and the deprecated
|
|
`new Buffer(size)` constructor only when `size` is less than or equal to
|
|
`Buffer.poolSize >> 1` (floor of [`Buffer.poolSize`][] divided by two).
|
|
|
|
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 important when an application requires the
|
|
additional performance that [`Buffer.allocUnsafe()`][] provides.
|
|
|
|
### Class Method: Buffer.allocUnsafeSlow(size)
|
|
<!-- YAML
|
|
added: v5.12.0
|
|
-->
|
|
|
|
* `size` {integer} The desired length of the new `Buffer`.
|
|
|
|
Allocates a new `Buffer` of `size` bytes. If `size` is larger than
|
|
[`buffer.constants.MAX_LENGTH`][] or smaller than 0, [`ERR_INVALID_OPT_VALUE`][]
|
|
is thrown. A zero-length `Buffer` is created if `size` is 0.
|
|
|
|
The underlying memory for `Buffer` instances created in this way is *not
|
|
initialized*. The contents of the newly created `Buffer` are unknown and
|
|
*may contain sensitive data*. Use [`buf.fill(0)`][`buf.fill()`] to initialize
|
|
such `Buffer` instances with zeroes.
|
|
|
|
When using [`Buffer.allocUnsafe()`][] to allocate new `Buffer` instances,
|
|
allocations under 4KB are sliced from a single pre-allocated `Buffer`. This
|
|
allows applications to avoid the garbage collection overhead of creating many
|
|
individually allocated `Buffer` instances. This approach improves both
|
|
performance and memory usage by eliminating the need to track and clean up as
|
|
many persistent objects.
|
|
|
|
However, in the case where a developer may need to retain a small chunk of
|
|
memory from a pool for an indeterminate amount of time, it may be appropriate
|
|
to create an un-pooled `Buffer` instance using `Buffer.allocUnsafeSlow()` and
|
|
then copying out the relevant bits.
|
|
|
|
```js
|
|
// Need to keep around a few small chunks of memory.
|
|
const store = [];
|
|
|
|
socket.on('readable', () => {
|
|
let data;
|
|
while (null !== (data = readable.read())) {
|
|
// Allocate for retained data.
|
|
const sb = Buffer.allocUnsafeSlow(10);
|
|
|
|
// Copy the data into the new allocation.
|
|
data.copy(sb, 0, 0, 10);
|
|
|
|
store.push(sb);
|
|
}
|
|
});
|
|
```
|
|
|
|
`Buffer.allocUnsafeSlow()` should be used only as a last resort after a
|
|
developer has observed undue memory retention in their applications.
|
|
|
|
A `TypeError` will be thrown if `size` is not a number.
|
|
|
|
### Class Method: Buffer.byteLength(string\[, encoding\])
|
|
<!-- YAML
|
|
added: v0.1.90
|
|
changes:
|
|
- version: v7.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/8946
|
|
description: Passing invalid input will now throw an error.
|
|
- version: v5.10.0
|
|
pr-url: https://github.com/nodejs/node/pull/5255
|
|
description: The `string` parameter can now be any `TypedArray`, `DataView`
|
|
or `ArrayBuffer`.
|
|
-->
|
|
|
|
* `string` {string|Buffer|TypedArray|DataView|ArrayBuffer|SharedArrayBuffer} A
|
|
value to calculate the length of.
|
|
* `encoding` {string} If `string` is a string, this is its encoding.
|
|
**Default:** `'utf8'`.
|
|
* Returns: {integer} The number of bytes contained within `string`.
|
|
|
|
Returns the actual byte length of a string. This is not the same as
|
|
[`String.prototype.length`][] since that returns the number of *characters* in
|
|
a string.
|
|
|
|
For `'base64'` and `'hex'`, this function assumes valid input. For strings that
|
|
contain non-Base64/Hex-encoded data (e.g. whitespace), the return value might be
|
|
greater than the length of a `Buffer` created from the string.
|
|
|
|
```js
|
|
const str = '\u00bd + \u00bc = \u00be';
|
|
|
|
console.log(`${str}: ${str.length} characters, ` +
|
|
`${Buffer.byteLength(str, 'utf8')} bytes`);
|
|
// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes
|
|
```
|
|
|
|
When `string` is a `Buffer`/[`DataView`][]/[`TypedArray`][]/[`ArrayBuffer`][]/
|
|
[`SharedArrayBuffer`][], the actual byte length is returned.
|
|
|
|
### Class Method: Buffer.compare(buf1, buf2)
|
|
<!-- YAML
|
|
added: v0.11.13
|
|
changes:
|
|
- version: v8.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/10236
|
|
description: The arguments can now be `Uint8Array`s.
|
|
-->
|
|
|
|
* `buf1` {Buffer|Uint8Array}
|
|
* `buf2` {Buffer|Uint8Array}
|
|
* Returns: {integer}
|
|
|
|
Compares `buf1` to `buf2` typically for the purpose of sorting arrays of
|
|
`Buffer` instances. This is equivalent to calling
|
|
[`buf1.compare(buf2)`][`buf.compare()`].
|
|
|
|
```js
|
|
const buf1 = Buffer.from('1234');
|
|
const buf2 = Buffer.from('0123');
|
|
const arr = [buf1, buf2];
|
|
|
|
console.log(arr.sort(Buffer.compare));
|
|
// Prints: [ <Buffer 30 31 32 33>, <Buffer 31 32 33 34> ]
|
|
// (This result is equal to: [buf2, buf1].)
|
|
```
|
|
|
|
### Class Method: Buffer.concat(list\[, totalLength\])
|
|
<!-- YAML
|
|
added: v0.7.11
|
|
changes:
|
|
- version: v8.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/10236
|
|
description: The elements of `list` can now be `Uint8Array`s.
|
|
-->
|
|
|
|
* `list` {Buffer[] | Uint8Array[]} List of `Buffer` or [`Uint8Array`][]
|
|
instances to concat.
|
|
* `totalLength` {integer} Total length of the `Buffer` instances in `list`
|
|
when concatenated.
|
|
* Returns: {Buffer}
|
|
|
|
Returns a new `Buffer` which is the result of concatenating all the `Buffer`
|
|
instances in the `list` together.
|
|
|
|
If the list has no items, or if the `totalLength` is 0, then a new zero-length
|
|
`Buffer` is returned.
|
|
|
|
If `totalLength` is not provided, it is calculated from the `Buffer` instances
|
|
in `list`. This however causes an additional loop to be executed in order to
|
|
calculate the `totalLength`, so it is faster to provide the length explicitly if
|
|
it is already known.
|
|
|
|
If `totalLength` is provided, it is coerced to an unsigned integer. If the
|
|
combined length of the `Buffer`s in `list` exceeds `totalLength`, the result is
|
|
truncated to `totalLength`.
|
|
|
|
```js
|
|
// Create a single `Buffer` from a list of three `Buffer` instances.
|
|
|
|
const buf1 = Buffer.alloc(10);
|
|
const buf2 = Buffer.alloc(14);
|
|
const buf3 = Buffer.alloc(18);
|
|
const totalLength = buf1.length + buf2.length + buf3.length;
|
|
|
|
console.log(totalLength);
|
|
// Prints: 42
|
|
|
|
const bufA = Buffer.concat([buf1, buf2, buf3], totalLength);
|
|
|
|
console.log(bufA);
|
|
// Prints: <Buffer 00 00 00 00 ...>
|
|
console.log(bufA.length);
|
|
// Prints: 42
|
|
```
|
|
|
|
### Class Method: Buffer.from(array)
|
|
<!-- YAML
|
|
added: v5.10.0
|
|
-->
|
|
|
|
* `array` {integer[]}
|
|
|
|
Allocates a new `Buffer` using an `array` of octets.
|
|
|
|
```js
|
|
// Creates a new Buffer containing UTF-8 bytes of the string 'buffer'.
|
|
const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);
|
|
```
|
|
|
|
A `TypeError` will be thrown if `array` is not an `Array` or other type
|
|
appropriate for `Buffer.from()` variants.
|
|
|
|
### Class Method: Buffer.from(arrayBuffer\[, byteOffset\[, length\]\])
|
|
<!-- YAML
|
|
added: v5.10.0
|
|
-->
|
|
|
|
* `arrayBuffer` {ArrayBuffer|SharedArrayBuffer} An [`ArrayBuffer`][],
|
|
[`SharedArrayBuffer`][], or the `.buffer` property of a [`TypedArray`][].
|
|
* `byteOffset` {integer} Index of first byte to expose. **Default:** `0`.
|
|
* `length` {integer} Number of bytes to expose.
|
|
**Default:** `arrayBuffer.length - byteOffset`.
|
|
|
|
This creates a view of the [`ArrayBuffer`][] without copying the underlying
|
|
memory. For example, 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
|
|
const arr = new Uint16Array(2);
|
|
|
|
arr[0] = 5000;
|
|
arr[1] = 4000;
|
|
|
|
// Shares memory with `arr`.
|
|
const buf = Buffer.from(arr.buffer);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 88 13 a0 0f>
|
|
|
|
// Changing the original Uint16Array changes the Buffer also.
|
|
arr[1] = 6000;
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 88 13 70 17>
|
|
```
|
|
|
|
The optional `byteOffset` and `length` arguments specify a memory range within
|
|
the `arrayBuffer` that will be shared by the `Buffer`.
|
|
|
|
```js
|
|
const ab = new ArrayBuffer(10);
|
|
const buf = Buffer.from(ab, 0, 2);
|
|
|
|
console.log(buf.length);
|
|
// Prints: 2
|
|
```
|
|
|
|
A `TypeError` will be thrown if `arrayBuffer` is not an [`ArrayBuffer`][] or a
|
|
[`SharedArrayBuffer`][] or other type appropriate for `Buffer.from()` variants.
|
|
|
|
### Class Method: Buffer.from(buffer)
|
|
<!-- YAML
|
|
added: v5.10.0
|
|
-->
|
|
|
|
* `buffer` {Buffer|Uint8Array} An existing `Buffer` or [`Uint8Array`][] from
|
|
which to copy data.
|
|
|
|
Copies the passed `buffer` data onto a new `Buffer` instance.
|
|
|
|
```js
|
|
const buf1 = Buffer.from('buffer');
|
|
const buf2 = Buffer.from(buf1);
|
|
|
|
buf1[0] = 0x61;
|
|
|
|
console.log(buf1.toString());
|
|
// Prints: auffer
|
|
console.log(buf2.toString());
|
|
// Prints: buffer
|
|
```
|
|
|
|
A `TypeError` will be thrown if `buffer` is not a `Buffer` or other type
|
|
appropriate for `Buffer.from()` variants.
|
|
|
|
### Class Method: Buffer.from(object\[, offsetOrEncoding\[, length\]\])
|
|
<!-- YAML
|
|
added: v8.2.0
|
|
-->
|
|
|
|
* `object` {Object} An object supporting `Symbol.toPrimitive` or `valueOf()`.
|
|
* `offsetOrEncoding` {integer|string} A byte-offset or encoding, depending on
|
|
the value returned either by `object.valueOf()` or
|
|
`object[Symbol.toPrimitive]()`.
|
|
* `length` {integer} A length, depending on the value returned either by
|
|
`object.valueOf()` or `object[Symbol.toPrimitive]()`.
|
|
|
|
For objects whose `valueOf()` function returns a value not strictly equal to
|
|
`object`, returns `Buffer.from(object.valueOf(), offsetOrEncoding, length)`.
|
|
|
|
```js
|
|
const buf = Buffer.from(new String('this is a test'));
|
|
// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>
|
|
```
|
|
|
|
For objects that support `Symbol.toPrimitive`, returns
|
|
`Buffer.from(object[Symbol.toPrimitive](), offsetOrEncoding, length)`.
|
|
|
|
```js
|
|
class Foo {
|
|
[Symbol.toPrimitive]() {
|
|
return 'this is a test';
|
|
}
|
|
}
|
|
|
|
const buf = Buffer.from(new Foo(), 'utf8');
|
|
// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>
|
|
```
|
|
|
|
A `TypeError` will be thrown if `object` has not mentioned methods or is not of
|
|
other type appropriate for `Buffer.from()` variants.
|
|
|
|
### Class Method: Buffer.from(string\[, encoding\])
|
|
<!-- YAML
|
|
added: v5.10.0
|
|
-->
|
|
|
|
* `string` {string} A string to encode.
|
|
* `encoding` {string} The encoding of `string`. **Default:** `'utf8'`.
|
|
|
|
Creates a new `Buffer` containing `string`. The `encoding` parameter identifies
|
|
the character encoding of `string`.
|
|
|
|
```js
|
|
const buf1 = Buffer.from('this is a tést');
|
|
const buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');
|
|
|
|
console.log(buf1.toString());
|
|
// Prints: this is a tést
|
|
console.log(buf2.toString());
|
|
// Prints: this is a tést
|
|
console.log(buf1.toString('ascii'));
|
|
// Prints: this is a tC)st
|
|
```
|
|
|
|
A `TypeError` will be thrown if `string` is not a string or other type
|
|
appropriate for `Buffer.from()` variants.
|
|
|
|
### Class Method: Buffer.isBuffer(obj)
|
|
<!-- YAML
|
|
added: v0.1.101
|
|
-->
|
|
|
|
* `obj` {Object}
|
|
* Returns: {boolean}
|
|
|
|
Returns `true` if `obj` is a `Buffer`, `false` otherwise.
|
|
|
|
### Class Method: Buffer.isEncoding(encoding)
|
|
<!-- YAML
|
|
added: v0.9.1
|
|
-->
|
|
|
|
* `encoding` {string} A character encoding name to check.
|
|
* Returns: {boolean}
|
|
|
|
Returns `true` if `encoding` contains a supported character encoding, or `false`
|
|
otherwise.
|
|
|
|
```js
|
|
console.log(Buffer.isEncoding('utf-8'));
|
|
// Prints: true
|
|
|
|
console.log(Buffer.isEncoding('hex'));
|
|
// Prints: true
|
|
|
|
console.log(Buffer.isEncoding('utf/8'));
|
|
// Prints: false
|
|
|
|
console.log(Buffer.isEncoding(''));
|
|
// Prints: false
|
|
```
|
|
|
|
### Class Property: Buffer.poolSize
|
|
<!-- YAML
|
|
added: v0.11.3
|
|
-->
|
|
|
|
* {integer} **Default:** `8192`
|
|
|
|
This is the size (in bytes) of pre-allocated internal `Buffer` instances used
|
|
for pooling. This value may be modified.
|
|
|
|
### buf\[index\]
|
|
<!-- YAML
|
|
type: property
|
|
name: [index]
|
|
-->
|
|
|
|
* `index` {integer}
|
|
|
|
The index operator `[index]` can be used to get and set the octet at position
|
|
`index` in `buf`. The values refer to individual bytes, so the legal value
|
|
range is between `0x00` and `0xFF` (hex) or `0` and `255` (decimal).
|
|
|
|
This operator is inherited from `Uint8Array`, so its behavior on out-of-bounds
|
|
access is the same as `UInt8Array`. In other words, getting returns `undefined`
|
|
and setting does nothing.
|
|
|
|
```js
|
|
// Copy an ASCII string into a `Buffer` one byte at a time.
|
|
|
|
const str = 'Node.js';
|
|
const buf = Buffer.allocUnsafe(str.length);
|
|
|
|
for (let i = 0; i < str.length; i++) {
|
|
buf[i] = str.charCodeAt(i);
|
|
}
|
|
|
|
console.log(buf.toString('ascii'));
|
|
// Prints: Node.js
|
|
```
|
|
|
|
### buf.buffer
|
|
|
|
* {ArrayBuffer} The underlying `ArrayBuffer` object based on
|
|
which this `Buffer` object is created.
|
|
|
|
```js
|
|
const arrayBuffer = new ArrayBuffer(16);
|
|
const buffer = Buffer.from(arrayBuffer);
|
|
|
|
console.log(buffer.buffer === arrayBuffer);
|
|
// Prints: true
|
|
```
|
|
|
|
### buf.byteOffset
|
|
|
|
* {integer} The `byteOffset` on the underlying `ArrayBuffer` object based on
|
|
which this `Buffer` object is created.
|
|
|
|
When setting `byteOffset` in `Buffer.from(ArrayBuffer, byteOffset, length)`
|
|
or sometimes when allocating a buffer smaller than `Buffer.poolSize` the
|
|
buffer doesn't start from a zero offset on the underlying `ArrayBuffer`.
|
|
|
|
This can cause problems when accessing the underlying `ArrayBuffer` directly
|
|
using `buf.buffer`, as the first bytes in this `ArrayBuffer` may be unrelated
|
|
to the `buf` object itself.
|
|
|
|
A common issue is when casting a `Buffer` object to a `TypedArray` object,
|
|
in this case one needs to specify the `byteOffset` correctly:
|
|
|
|
```js
|
|
// Create a buffer smaller than `Buffer.poolSize`.
|
|
const nodeBuffer = new Buffer.from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
|
|
|
|
// When casting the Node.js Buffer to an Int8 TypedArray remember to use the
|
|
// byteOffset.
|
|
new Int8Array(nodeBuffer.buffer, nodeBuffer.byteOffset, nodeBuffer.length);
|
|
```
|
|
|
|
### buf.compare(target\[, targetStart\[, targetEnd\[, sourceStart\[, sourceEnd\]\]\]\])
|
|
<!-- YAML
|
|
added: v0.11.13
|
|
changes:
|
|
- version: v8.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/10236
|
|
description: The `target` parameter can now be a `Uint8Array`.
|
|
- version: v5.11.0
|
|
pr-url: https://github.com/nodejs/node/pull/5880
|
|
description: Additional parameters for specifying offsets are supported now.
|
|
-->
|
|
|
|
* `target` {Buffer|Uint8Array} A `Buffer` or [`Uint8Array`][] with which to
|
|
compare `buf`.
|
|
* `targetStart` {integer} The offset within `target` at which to begin
|
|
comparison. **Default:** `0`.
|
|
* `targetEnd` {integer} The offset within `target` at which to end comparison
|
|
(not inclusive). **Default:** `target.length`.
|
|
* `sourceStart` {integer} The offset within `buf` at which to begin comparison.
|
|
**Default:** `0`.
|
|
* `sourceEnd` {integer} The offset within `buf` at which to end comparison
|
|
(not inclusive). **Default:** [`buf.length`][].
|
|
* Returns: {integer}
|
|
|
|
Compares `buf` with `target` and returns a number indicating whether `buf`
|
|
comes before, after, or is the same as `target` in sort order.
|
|
Comparison is based on the actual sequence of bytes in each `Buffer`.
|
|
|
|
* `0` is returned if `target` is the same as `buf`
|
|
* `1` is returned if `target` should come *before* `buf` when sorted.
|
|
* `-1` is returned if `target` should come *after* `buf` when sorted.
|
|
|
|
```js
|
|
const buf1 = Buffer.from('ABC');
|
|
const buf2 = Buffer.from('BCD');
|
|
const buf3 = Buffer.from('ABCD');
|
|
|
|
console.log(buf1.compare(buf1));
|
|
// Prints: 0
|
|
console.log(buf1.compare(buf2));
|
|
// Prints: -1
|
|
console.log(buf1.compare(buf3));
|
|
// Prints: -1
|
|
console.log(buf2.compare(buf1));
|
|
// Prints: 1
|
|
console.log(buf2.compare(buf3));
|
|
// Prints: 1
|
|
console.log([buf1, buf2, buf3].sort(Buffer.compare));
|
|
// Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ]
|
|
// (This result is equal to: [buf1, buf3, buf2].)
|
|
```
|
|
|
|
The optional `targetStart`, `targetEnd`, `sourceStart`, and `sourceEnd`
|
|
arguments can be used to limit the comparison to specific ranges within `target`
|
|
and `buf` respectively.
|
|
|
|
```js
|
|
const buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);
|
|
const buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);
|
|
|
|
console.log(buf1.compare(buf2, 5, 9, 0, 4));
|
|
// Prints: 0
|
|
console.log(buf1.compare(buf2, 0, 6, 4));
|
|
// Prints: -1
|
|
console.log(buf1.compare(buf2, 5, 6, 5));
|
|
// Prints: 1
|
|
```
|
|
|
|
[`ERR_OUT_OF_RANGE`][] is thrown if `targetStart < 0`, `sourceStart < 0`,
|
|
`targetEnd > target.byteLength`, or `sourceEnd > source.byteLength`.
|
|
|
|
### buf.copy(target\[, targetStart\[, sourceStart\[, sourceEnd\]\]\])
|
|
<!-- YAML
|
|
added: v0.1.90
|
|
-->
|
|
|
|
* `target` {Buffer|Uint8Array} A `Buffer` or [`Uint8Array`][] to copy into.
|
|
* `targetStart` {integer} The offset within `target` at which to begin
|
|
writing. **Default:** `0`.
|
|
* `sourceStart` {integer} The offset within `buf` from which to begin copying.
|
|
**Default:** `0`.
|
|
* `sourceEnd` {integer} The offset within `buf` at which to stop copying (not
|
|
inclusive). **Default:** [`buf.length`][].
|
|
* Returns: {integer} The number of bytes copied.
|
|
|
|
Copies data from a region of `buf` to a region in `target` even if the `target`
|
|
memory region overlaps with `buf`.
|
|
|
|
```js
|
|
// Create two `Buffer` instances.
|
|
const buf1 = Buffer.allocUnsafe(26);
|
|
const buf2 = Buffer.allocUnsafe(26).fill('!');
|
|
|
|
for (let i = 0; i < 26; i++) {
|
|
// 97 is the decimal ASCII value for 'a'.
|
|
buf1[i] = i + 97;
|
|
}
|
|
|
|
// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`.
|
|
buf1.copy(buf2, 8, 16, 20);
|
|
|
|
console.log(buf2.toString('ascii', 0, 25));
|
|
// Prints: !!!!!!!!qrst!!!!!!!!!!!!!
|
|
```
|
|
|
|
```js
|
|
// Create a `Buffer` and copy data from one region to an overlapping region
|
|
// within the same `Buffer`.
|
|
|
|
const buf = Buffer.allocUnsafe(26);
|
|
|
|
for (let i = 0; i < 26; i++) {
|
|
// 97 is the decimal ASCII value for 'a'.
|
|
buf[i] = i + 97;
|
|
}
|
|
|
|
buf.copy(buf, 0, 4, 10);
|
|
|
|
console.log(buf.toString());
|
|
// Prints: efghijghijklmnopqrstuvwxyz
|
|
```
|
|
|
|
### buf.entries()
|
|
<!-- YAML
|
|
added: v1.1.0
|
|
-->
|
|
|
|
* Returns: {Iterator}
|
|
|
|
Creates and returns an [iterator][] of `[index, byte]` pairs from the contents
|
|
of `buf`.
|
|
|
|
```js
|
|
// Log the entire contents of a `Buffer`.
|
|
|
|
const buf = Buffer.from('buffer');
|
|
|
|
for (const pair of buf.entries()) {
|
|
console.log(pair);
|
|
}
|
|
// Prints:
|
|
// [0, 98]
|
|
// [1, 117]
|
|
// [2, 102]
|
|
// [3, 102]
|
|
// [4, 101]
|
|
// [5, 114]
|
|
```
|
|
|
|
### buf.equals(otherBuffer)
|
|
<!-- YAML
|
|
added: v0.11.13
|
|
changes:
|
|
- version: v8.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/10236
|
|
description: The arguments can now be `Uint8Array`s.
|
|
-->
|
|
|
|
* `otherBuffer` {Buffer|Uint8Array} A `Buffer` or [`Uint8Array`][] with which to
|
|
compare `buf`.
|
|
* Returns: {boolean}
|
|
|
|
Returns `true` if both `buf` and `otherBuffer` have exactly the same bytes,
|
|
`false` otherwise.
|
|
|
|
```js
|
|
const buf1 = Buffer.from('ABC');
|
|
const buf2 = Buffer.from('414243', 'hex');
|
|
const buf3 = Buffer.from('ABCD');
|
|
|
|
console.log(buf1.equals(buf2));
|
|
// Prints: true
|
|
console.log(buf1.equals(buf3));
|
|
// Prints: false
|
|
```
|
|
|
|
### buf.fill(value\[, offset\[, end\]\]\[, encoding\])
|
|
<!-- YAML
|
|
added: v0.5.0
|
|
changes:
|
|
- version: v11.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/22969
|
|
description: Throws `ERR_OUT_OF_RANGE` instead of `ERR_INDEX_OUT_OF_RANGE`.
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18790
|
|
description: Negative `end` values throw an `ERR_INDEX_OUT_OF_RANGE` error.
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18129
|
|
description: Attempting to fill a non-zero length buffer with a zero length
|
|
buffer triggers a thrown exception.
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/17427
|
|
description: Specifying an invalid string for `value` triggers a thrown
|
|
exception.
|
|
- version: v5.7.0
|
|
pr-url: https://github.com/nodejs/node/pull/4935
|
|
description: The `encoding` parameter is supported now.
|
|
-->
|
|
|
|
* `value` {string|Buffer|Uint8Array|integer} The value with which to fill `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to fill `buf`.
|
|
**Default:** `0`.
|
|
* `end` {integer} Where to stop filling `buf` (not inclusive). **Default:**
|
|
[`buf.length`][].
|
|
* `encoding` {string} The encoding for `value` if `value` is a string.
|
|
**Default:** `'utf8'`.
|
|
* Returns: {Buffer} A reference to `buf`.
|
|
|
|
Fills `buf` with the specified `value`. If the `offset` and `end` are not given,
|
|
the entire `buf` will be filled:
|
|
|
|
```js
|
|
// Fill a `Buffer` with the ASCII character 'h'.
|
|
|
|
const b = Buffer.allocUnsafe(50).fill('h');
|
|
|
|
console.log(b.toString());
|
|
// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
|
|
```
|
|
|
|
`value` is coerced to a `uint32` value if it is not a string, `Buffer`, or
|
|
integer. If the resulting integer is greater than `255` (decimal), `buf` will be
|
|
filled with `value & 255`.
|
|
|
|
If the final write of a `fill()` operation falls on a multi-byte character,
|
|
then only the bytes of that character that fit into `buf` are written:
|
|
|
|
```js
|
|
// Fill a `Buffer` with a two-byte character.
|
|
|
|
console.log(Buffer.allocUnsafe(3).fill('\u0222'));
|
|
// Prints: <Buffer c8 a2 c8>
|
|
```
|
|
|
|
If `value` contains invalid characters, it is truncated; if no valid
|
|
fill data remains, an exception is thrown:
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(5);
|
|
|
|
console.log(buf.fill('a'));
|
|
// Prints: <Buffer 61 61 61 61 61>
|
|
console.log(buf.fill('aazz', 'hex'));
|
|
// Prints: <Buffer aa aa aa aa aa>
|
|
console.log(buf.fill('zz', 'hex'));
|
|
// Throws an exception.
|
|
```
|
|
|
|
### buf.includes(value\[, byteOffset\]\[, encoding\])
|
|
<!-- YAML
|
|
added: v5.3.0
|
|
-->
|
|
|
|
* `value` {string|Buffer|Uint8Array|integer} What to search for.
|
|
* `byteOffset` {integer} Where to begin searching in `buf`. If negative, then
|
|
offset is calculated from the end of `buf`. **Default:** `0`.
|
|
* `encoding` {string} If `value` is a string, this is its encoding.
|
|
**Default:** `'utf8'`.
|
|
* Returns: {boolean} `true` if `value` was found in `buf`, `false` otherwise.
|
|
|
|
Equivalent to [`buf.indexOf() !== -1`][`buf.indexOf()`].
|
|
|
|
```js
|
|
const buf = Buffer.from('this is a buffer');
|
|
|
|
console.log(buf.includes('this'));
|
|
// Prints: true
|
|
console.log(buf.includes('is'));
|
|
// Prints: true
|
|
console.log(buf.includes(Buffer.from('a buffer')));
|
|
// Prints: true
|
|
console.log(buf.includes(97));
|
|
// Prints: true (97 is the decimal ASCII value for 'a')
|
|
console.log(buf.includes(Buffer.from('a buffer example')));
|
|
// Prints: false
|
|
console.log(buf.includes(Buffer.from('a buffer example').slice(0, 8)));
|
|
// Prints: true
|
|
console.log(buf.includes('this', 4));
|
|
// Prints: false
|
|
```
|
|
|
|
### buf.indexOf(value\[, byteOffset\]\[, encoding\])
|
|
<!-- YAML
|
|
added: v1.5.0
|
|
changes:
|
|
- version: v8.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/10236
|
|
description: The `value` can now be a `Uint8Array`.
|
|
- version: v5.7.0, v4.4.0
|
|
pr-url: https://github.com/nodejs/node/pull/4803
|
|
description: When `encoding` is being passed, the `byteOffset` parameter
|
|
is no longer required.
|
|
-->
|
|
|
|
* `value` {string|Buffer|Uint8Array|integer} What to search for.
|
|
* `byteOffset` {integer} Where to begin searching in `buf`. If negative, then
|
|
offset is calculated from the end of `buf`. **Default:** `0`.
|
|
* `encoding` {string} If `value` is a string, this is the encoding used to
|
|
determine the binary representation of the string that will be searched for in
|
|
`buf`. **Default:** `'utf8'`.
|
|
* Returns: {integer} The index of the first occurrence of `value` in `buf`, or
|
|
`-1` if `buf` does not contain `value`.
|
|
|
|
If `value` is:
|
|
|
|
* a string, `value` is interpreted according to the character encoding in
|
|
`encoding`.
|
|
* a `Buffer` or [`Uint8Array`][], `value` will be used in its entirety.
|
|
To compare a partial `Buffer`, use [`buf.slice()`][].
|
|
* a number, `value` will be interpreted as an unsigned 8-bit integer
|
|
value between `0` and `255`.
|
|
|
|
```js
|
|
const buf = Buffer.from('this is a buffer');
|
|
|
|
console.log(buf.indexOf('this'));
|
|
// Prints: 0
|
|
console.log(buf.indexOf('is'));
|
|
// Prints: 2
|
|
console.log(buf.indexOf(Buffer.from('a buffer')));
|
|
// Prints: 8
|
|
console.log(buf.indexOf(97));
|
|
// Prints: 8 (97 is the decimal ASCII value for 'a')
|
|
console.log(buf.indexOf(Buffer.from('a buffer example')));
|
|
// Prints: -1
|
|
console.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8)));
|
|
// Prints: 8
|
|
|
|
const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');
|
|
|
|
console.log(utf16Buffer.indexOf('\u03a3', 0, 'utf16le'));
|
|
// Prints: 4
|
|
console.log(utf16Buffer.indexOf('\u03a3', -4, 'utf16le'));
|
|
// Prints: 6
|
|
```
|
|
|
|
If `value` is not a string, number, or `Buffer`, this method will throw a
|
|
`TypeError`. If `value` is a number, it will be coerced to a valid byte value,
|
|
an integer between 0 and 255.
|
|
|
|
If `byteOffset` is not a number, it will be coerced to a number. If the result
|
|
of coercion is `NaN` or `0`, then the entire buffer will be searched. This
|
|
behavior matches [`String#indexOf()`][].
|
|
|
|
```js
|
|
const b = Buffer.from('abcdef');
|
|
|
|
// Passing a value that's a number, but not a valid byte.
|
|
// Prints: 2, equivalent to searching for 99 or 'c'.
|
|
console.log(b.indexOf(99.9));
|
|
console.log(b.indexOf(256 + 99));
|
|
|
|
// Passing a byteOffset that coerces to NaN or 0.
|
|
// Prints: 1, searching the whole buffer.
|
|
console.log(b.indexOf('b', undefined));
|
|
console.log(b.indexOf('b', {}));
|
|
console.log(b.indexOf('b', null));
|
|
console.log(b.indexOf('b', []));
|
|
```
|
|
|
|
If `value` is an empty string or empty `Buffer` and `byteOffset` is less
|
|
than `buf.length`, `byteOffset` will be returned. If `value` is empty and
|
|
`byteOffset` is at least `buf.length`, `buf.length` will be returned.
|
|
|
|
### buf.keys()
|
|
<!-- YAML
|
|
added: v1.1.0
|
|
-->
|
|
|
|
* Returns: {Iterator}
|
|
|
|
Creates and returns an [iterator][] of `buf` keys (indices).
|
|
|
|
```js
|
|
const buf = Buffer.from('buffer');
|
|
|
|
for (const key of buf.keys()) {
|
|
console.log(key);
|
|
}
|
|
// Prints:
|
|
// 0
|
|
// 1
|
|
// 2
|
|
// 3
|
|
// 4
|
|
// 5
|
|
```
|
|
|
|
### buf.lastIndexOf(value\[, byteOffset\]\[, encoding\])
|
|
<!-- YAML
|
|
added: v6.0.0
|
|
changes:
|
|
- version: v8.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/10236
|
|
description: The `value` can now be a `Uint8Array`.
|
|
-->
|
|
|
|
* `value` {string|Buffer|Uint8Array|integer} What to search for.
|
|
* `byteOffset` {integer} Where to begin searching in `buf`. If negative, then
|
|
offset is calculated from the end of `buf`. **Default:**
|
|
`buf.length - 1`.
|
|
* `encoding` {string} If `value` is a string, this is the encoding used to
|
|
determine the binary representation of the string that will be searched for in
|
|
`buf`. **Default:** `'utf8'`.
|
|
* Returns: {integer} The index of the last occurrence of `value` in `buf`, or
|
|
`-1` if `buf` does not contain `value`.
|
|
|
|
Identical to [`buf.indexOf()`][], except the last occurrence of `value` is found
|
|
rather than the first occurrence.
|
|
|
|
```js
|
|
const buf = Buffer.from('this buffer is a buffer');
|
|
|
|
console.log(buf.lastIndexOf('this'));
|
|
// Prints: 0
|
|
console.log(buf.lastIndexOf('buffer'));
|
|
// Prints: 17
|
|
console.log(buf.lastIndexOf(Buffer.from('buffer')));
|
|
// Prints: 17
|
|
console.log(buf.lastIndexOf(97));
|
|
// Prints: 15 (97 is the decimal ASCII value for 'a')
|
|
console.log(buf.lastIndexOf(Buffer.from('yolo')));
|
|
// Prints: -1
|
|
console.log(buf.lastIndexOf('buffer', 5));
|
|
// Prints: 5
|
|
console.log(buf.lastIndexOf('buffer', 4));
|
|
// Prints: -1
|
|
|
|
const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');
|
|
|
|
console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
|
|
// Prints: 6
|
|
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
|
|
// Prints: 4
|
|
```
|
|
|
|
If `value` is not a string, number, or `Buffer`, this method will throw a
|
|
`TypeError`. If `value` is a number, it will be coerced to a valid byte value,
|
|
an integer between 0 and 255.
|
|
|
|
If `byteOffset` is not a number, it will be coerced to a number. Any arguments
|
|
that coerce to `NaN`, like `{}` or `undefined`, will search the whole buffer.
|
|
This behavior matches [`String#lastIndexOf()`][].
|
|
|
|
```js
|
|
const b = Buffer.from('abcdef');
|
|
|
|
// Passing a value that's a number, but not a valid byte.
|
|
// Prints: 2, equivalent to searching for 99 or 'c'.
|
|
console.log(b.lastIndexOf(99.9));
|
|
console.log(b.lastIndexOf(256 + 99));
|
|
|
|
// Passing a byteOffset that coerces to NaN.
|
|
// Prints: 1, searching the whole buffer.
|
|
console.log(b.lastIndexOf('b', undefined));
|
|
console.log(b.lastIndexOf('b', {}));
|
|
|
|
// Passing a byteOffset that coerces to 0.
|
|
// Prints: -1, equivalent to passing 0.
|
|
console.log(b.lastIndexOf('b', null));
|
|
console.log(b.lastIndexOf('b', []));
|
|
```
|
|
|
|
If `value` is an empty string or empty `Buffer`, `byteOffset` will be returned.
|
|
|
|
### buf.length
|
|
<!-- YAML
|
|
added: v0.1.90
|
|
-->
|
|
|
|
* {integer}
|
|
|
|
Returns the amount of memory allocated for `buf` in bytes. This
|
|
does not necessarily reflect the amount of "usable" data within `buf`.
|
|
|
|
```js
|
|
// Create a `Buffer` and write a shorter ASCII string to it.
|
|
|
|
const buf = Buffer.alloc(1234);
|
|
|
|
console.log(buf.length);
|
|
// Prints: 1234
|
|
|
|
buf.write('some string', 0, 'ascii');
|
|
|
|
console.log(buf.length);
|
|
// Prints: 1234
|
|
```
|
|
|
|
While the `length` property is not immutable, changing the value of `length`
|
|
can result in undefined and inconsistent behavior. Applications that wish to
|
|
modify the length of a `Buffer` should therefore treat `length` as read-only and
|
|
use [`buf.slice()`][] to create a new `Buffer`.
|
|
|
|
```js
|
|
let buf = Buffer.allocUnsafe(10);
|
|
|
|
buf.write('abcdefghj', 0, 'ascii');
|
|
|
|
console.log(buf.length);
|
|
// Prints: 10
|
|
|
|
buf = buf.slice(0, 5);
|
|
|
|
console.log(buf.length);
|
|
// Prints: 5
|
|
```
|
|
|
|
### buf.parent
|
|
<!-- YAML
|
|
deprecated: v8.0.0
|
|
-->
|
|
|
|
> Stability: 0 - Deprecated: Use [`buf.buffer`][] instead.
|
|
|
|
The `buf.parent` property is a deprecated alias for `buf.buffer`.
|
|
|
|
### buf.readBigInt64BE(\[offset\])
|
|
### buf.readBigInt64LE(\[offset\])
|
|
<!-- YAML
|
|
added: v12.0.0
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.
|
|
* Returns: {bigint}
|
|
|
|
Reads a signed 64-bit integer from `buf` at the specified `offset` with
|
|
the specified endian format (`readBigInt64BE()` returns big endian,
|
|
`readBigInt64LE()` returns little endian).
|
|
|
|
Integers read from a `Buffer` are interpreted as two's complement signed values.
|
|
|
|
### buf.readBigUInt64BE(\[offset\])
|
|
### buf.readBigUInt64LE(\[offset\])
|
|
<!-- YAML
|
|
added: v12.0.0
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.
|
|
* Returns: {bigint}
|
|
|
|
Reads an unsigned 64-bit integer from `buf` at the specified `offset` with
|
|
specified endian format (`readBigUInt64BE()` returns big endian,
|
|
`readBigUInt64LE()` returns little endian).
|
|
|
|
```js
|
|
const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);
|
|
|
|
console.log(buf.readBigUInt64BE(0));
|
|
// Prints: 4294967295n
|
|
|
|
console.log(buf.readBigUInt64LE(0));
|
|
// Prints: 18446744069414584320n
|
|
```
|
|
|
|
### buf.readDoubleBE(\[offset\])
|
|
### buf.readDoubleLE(\[offset\])
|
|
<!-- YAML
|
|
added: v0.11.15
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - 8`. **Default:** `0`.
|
|
* Returns: {number}
|
|
|
|
Reads a 64-bit double from `buf` at the specified `offset` with specified
|
|
endian format (`readDoubleBE()` returns big endian, `readDoubleLE()` returns
|
|
little endian).
|
|
|
|
```js
|
|
const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
|
|
|
|
console.log(buf.readDoubleBE(0));
|
|
// Prints: 8.20788039913184e-304
|
|
console.log(buf.readDoubleLE(0));
|
|
// Prints: 5.447603722011605e-270
|
|
console.log(buf.readDoubleLE(1));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readFloatBE(\[offset\])
|
|
### buf.readFloatLE(\[offset\])
|
|
<!-- YAML
|
|
added: v0.11.15
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.
|
|
* Returns: {number}
|
|
|
|
Reads a 32-bit float from `buf` at the specified `offset` with specified
|
|
endian format (`readFloatBE()` returns big endian, `readFloatLE()` returns
|
|
little endian).
|
|
|
|
```js
|
|
const buf = Buffer.from([1, 2, 3, 4]);
|
|
|
|
console.log(buf.readFloatBE(0));
|
|
// Prints: 2.387939260590663e-38
|
|
console.log(buf.readFloatLE(0));
|
|
// Prints: 1.539989614439558e-36
|
|
console.log(buf.readFloatLE(1));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readInt8(\[offset\])
|
|
<!-- YAML
|
|
added: v0.5.0
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - 1`. **Default:** `0`.
|
|
* Returns: {integer}
|
|
|
|
Reads a signed 8-bit integer from `buf` at the specified `offset`.
|
|
|
|
Integers read from a `Buffer` are interpreted as two's complement signed values.
|
|
|
|
```js
|
|
const buf = Buffer.from([-1, 5]);
|
|
|
|
console.log(buf.readInt8(0));
|
|
// Prints: -1
|
|
console.log(buf.readInt8(1));
|
|
// Prints: 5
|
|
console.log(buf.readInt8(2));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readInt16BE(\[offset\])
|
|
### buf.readInt16LE(\[offset\])
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.
|
|
* Returns: {integer}
|
|
|
|
Reads a signed 16-bit integer from `buf` at the specified `offset` with
|
|
the specified endian format (`readInt16BE()` returns big endian,
|
|
`readInt16LE()` returns little endian).
|
|
|
|
Integers read from a `Buffer` are interpreted as two's complement signed values.
|
|
|
|
```js
|
|
const buf = Buffer.from([0, 5]);
|
|
|
|
console.log(buf.readInt16BE(0));
|
|
// Prints: 5
|
|
console.log(buf.readInt16LE(0));
|
|
// Prints: 1280
|
|
console.log(buf.readInt16LE(1));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readInt32BE(\[offset\])
|
|
### buf.readInt32LE(\[offset\])
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.
|
|
* Returns: {integer}
|
|
|
|
Reads a signed 32-bit integer from `buf` at the specified `offset` with
|
|
the specified endian format (`readInt32BE()` returns big endian,
|
|
`readInt32LE()` returns little endian).
|
|
|
|
Integers read from a `Buffer` are interpreted as two's complement signed values.
|
|
|
|
```js
|
|
const buf = Buffer.from([0, 0, 0, 5]);
|
|
|
|
console.log(buf.readInt32BE(0));
|
|
// Prints: 5
|
|
console.log(buf.readInt32LE(0));
|
|
// Prints: 83886080
|
|
console.log(buf.readInt32LE(1));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readIntBE(offset, byteLength)
|
|
### buf.readIntLE(offset, byteLength)
|
|
<!-- YAML
|
|
added: v0.11.15
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
and `byteLength` to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - byteLength`.
|
|
* `byteLength` {integer} Number of bytes to read. Must satisfy
|
|
`0 < byteLength <= 6`.
|
|
* Returns: {integer}
|
|
|
|
Reads `byteLength` number of bytes from `buf` at the specified `offset`
|
|
and interprets the result as a two's complement signed value. Supports up to 48
|
|
bits of accuracy.
|
|
|
|
```js
|
|
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
|
|
|
|
console.log(buf.readIntLE(0, 6).toString(16));
|
|
// Prints: -546f87a9cbee
|
|
console.log(buf.readIntBE(0, 6).toString(16));
|
|
// Prints: 1234567890ab
|
|
console.log(buf.readIntBE(1, 6).toString(16));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
console.log(buf.readIntBE(1, 0).toString(16));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readUInt8(\[offset\])
|
|
<!-- YAML
|
|
added: v0.5.0
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - 1`. **Default:** `0`.
|
|
* Returns: {integer}
|
|
|
|
Reads an unsigned 8-bit integer from `buf` at the specified `offset`.
|
|
|
|
```js
|
|
const buf = Buffer.from([1, -2]);
|
|
|
|
console.log(buf.readUInt8(0));
|
|
// Prints: 1
|
|
console.log(buf.readUInt8(1));
|
|
// Prints: 254
|
|
console.log(buf.readUInt8(2));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readUInt16BE(\[offset\])
|
|
### buf.readUInt16LE(\[offset\])
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.
|
|
* Returns: {integer}
|
|
|
|
Reads an unsigned 16-bit integer from `buf` at the specified `offset` with
|
|
specified endian format (`readUInt16BE()` returns big endian, `readUInt16LE()`
|
|
returns little endian).
|
|
|
|
```js
|
|
const buf = Buffer.from([0x12, 0x34, 0x56]);
|
|
|
|
console.log(buf.readUInt16BE(0).toString(16));
|
|
// Prints: 1234
|
|
console.log(buf.readUInt16LE(0).toString(16));
|
|
// Prints: 3412
|
|
console.log(buf.readUInt16BE(1).toString(16));
|
|
// Prints: 3456
|
|
console.log(buf.readUInt16LE(1).toString(16));
|
|
// Prints: 5634
|
|
console.log(buf.readUInt16LE(2).toString(16));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readUInt32BE(\[offset\])
|
|
### buf.readUInt32LE(\[offset\])
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.
|
|
* Returns: {integer}
|
|
|
|
Reads an unsigned 32-bit integer from `buf` at the specified `offset` with
|
|
specified endian format (`readUInt32BE()` returns big endian,
|
|
`readUInt32LE()` returns little endian).
|
|
|
|
```js
|
|
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);
|
|
|
|
console.log(buf.readUInt32BE(0).toString(16));
|
|
// Prints: 12345678
|
|
console.log(buf.readUInt32LE(0).toString(16));
|
|
// Prints: 78563412
|
|
console.log(buf.readUInt32LE(1).toString(16));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.readUIntBE(offset, byteLength)
|
|
### buf.readUIntLE(offset, byteLength)
|
|
<!-- YAML
|
|
added: v0.11.15
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
and `byteLength` to `uint32` anymore.
|
|
-->
|
|
|
|
* `offset` {integer} Number of bytes to skip before starting to read. Must
|
|
satisfy `0 <= offset <= buf.length - byteLength`.
|
|
* `byteLength` {integer} Number of bytes to read. Must satisfy
|
|
`0 < byteLength <= 6`.
|
|
* Returns: {integer}
|
|
|
|
Reads `byteLength` number of bytes from `buf` at the specified `offset`
|
|
and interprets the result as an unsigned integer. Supports up to 48
|
|
bits of accuracy.
|
|
|
|
```js
|
|
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
|
|
|
|
console.log(buf.readUIntBE(0, 6).toString(16));
|
|
// Prints: 1234567890ab
|
|
console.log(buf.readUIntLE(0, 6).toString(16));
|
|
// Prints: ab9078563412
|
|
console.log(buf.readUIntBE(1, 6).toString(16));
|
|
// Throws ERR_OUT_OF_RANGE.
|
|
```
|
|
|
|
### buf.subarray(\[start\[, end\]\])
|
|
<!-- YAML
|
|
added: v3.0.0
|
|
-->
|
|
|
|
* `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.
|
|
|
|
Specifying `end` greater than [`buf.length`][] will return the same result as
|
|
that of `end` equal to [`buf.length`][].
|
|
|
|
Modifying the new `Buffer` slice will modify the memory in the original `Buffer`
|
|
because the allocated memory of the two objects overlap.
|
|
|
|
```js
|
|
// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte
|
|
// from the original `Buffer`.
|
|
|
|
const buf1 = Buffer.allocUnsafe(26);
|
|
|
|
for (let i = 0; i < 26; i++) {
|
|
// 97 is the decimal ASCII value for 'a'.
|
|
buf1[i] = i + 97;
|
|
}
|
|
|
|
const buf2 = buf1.subarray(0, 3);
|
|
|
|
console.log(buf2.toString('ascii', 0, buf2.length));
|
|
// Prints: abc
|
|
|
|
buf1[0] = 33;
|
|
|
|
console.log(buf2.toString('ascii', 0, buf2.length));
|
|
// Prints: !bc
|
|
```
|
|
|
|
Specifying negative indexes causes the slice to be generated relative to the
|
|
end of `buf` rather than the beginning.
|
|
|
|
```js
|
|
const buf = Buffer.from('buffer');
|
|
|
|
console.log(buf.subarray(-6, -1).toString());
|
|
// Prints: buffe
|
|
// (Equivalent to buf.subarray(0, 5).)
|
|
|
|
console.log(buf.subarray(-6, -2).toString());
|
|
// Prints: buff
|
|
// (Equivalent to buf.subarray(0, 4).)
|
|
|
|
console.log(buf.subarray(-5, -2).toString());
|
|
// Prints: uff
|
|
// (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()
|
|
<!-- YAML
|
|
added: v5.10.0
|
|
-->
|
|
|
|
* Returns: {Buffer} A reference to `buf`.
|
|
|
|
Interprets `buf` as an array of unsigned 16-bit integers and swaps the
|
|
byte order *in-place*. Throws [`ERR_INVALID_BUFFER_SIZE`][] if [`buf.length`][]
|
|
is not a multiple of 2.
|
|
|
|
```js
|
|
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
|
|
|
|
console.log(buf1);
|
|
// Prints: <Buffer 01 02 03 04 05 06 07 08>
|
|
|
|
buf1.swap16();
|
|
|
|
console.log(buf1);
|
|
// Prints: <Buffer 02 01 04 03 06 05 08 07>
|
|
|
|
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
|
|
|
|
buf2.swap16();
|
|
// Throws ERR_INVALID_BUFFER_SIZE.
|
|
```
|
|
|
|
One convenient use of `buf.swap16()` is to perform a fast in-place conversion
|
|
between UTF-16 little-endian and UTF-16 big-endian:
|
|
|
|
```js
|
|
const buf = Buffer.from('This is little-endian UTF-16', 'utf16le');
|
|
buf.swap16(); // Convert to big-endian UTF-16 text.
|
|
```
|
|
|
|
### buf.swap32()
|
|
<!-- YAML
|
|
added: v5.10.0
|
|
-->
|
|
|
|
* Returns: {Buffer} A reference to `buf`.
|
|
|
|
Interprets `buf` as an array of unsigned 32-bit integers and swaps the
|
|
byte order *in-place*. Throws [`ERR_INVALID_BUFFER_SIZE`][] if [`buf.length`][]
|
|
is not a multiple of 4.
|
|
|
|
```js
|
|
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
|
|
|
|
console.log(buf1);
|
|
// Prints: <Buffer 01 02 03 04 05 06 07 08>
|
|
|
|
buf1.swap32();
|
|
|
|
console.log(buf1);
|
|
// Prints: <Buffer 04 03 02 01 08 07 06 05>
|
|
|
|
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
|
|
|
|
buf2.swap32();
|
|
// Throws ERR_INVALID_BUFFER_SIZE.
|
|
```
|
|
|
|
### buf.swap64()
|
|
<!-- YAML
|
|
added: v6.3.0
|
|
-->
|
|
|
|
* Returns: {Buffer} A reference to `buf`.
|
|
|
|
Interprets `buf` as an array of 64-bit numbers and swaps byte order *in-place*.
|
|
Throws [`ERR_INVALID_BUFFER_SIZE`][] if [`buf.length`][] is not a multiple of 8.
|
|
|
|
```js
|
|
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
|
|
|
|
console.log(buf1);
|
|
// Prints: <Buffer 01 02 03 04 05 06 07 08>
|
|
|
|
buf1.swap64();
|
|
|
|
console.log(buf1);
|
|
// Prints: <Buffer 08 07 06 05 04 03 02 01>
|
|
|
|
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
|
|
|
|
buf2.swap64();
|
|
// Throws ERR_INVALID_BUFFER_SIZE.
|
|
```
|
|
|
|
JavaScript cannot encode 64-bit integers. This method is intended
|
|
for working with 64-bit floats.
|
|
|
|
### buf.toJSON()
|
|
<!-- YAML
|
|
added: v0.9.2
|
|
-->
|
|
|
|
* Returns: {Object}
|
|
|
|
Returns a JSON representation of `buf`. [`JSON.stringify()`][] implicitly calls
|
|
this function when stringifying a `Buffer` instance.
|
|
|
|
```js
|
|
const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);
|
|
const json = JSON.stringify(buf);
|
|
|
|
console.log(json);
|
|
// Prints: {"type":"Buffer","data":[1,2,3,4,5]}
|
|
|
|
const copy = JSON.parse(json, (key, value) => {
|
|
return value && value.type === 'Buffer' ?
|
|
Buffer.from(value.data) :
|
|
value;
|
|
});
|
|
|
|
console.log(copy);
|
|
// Prints: <Buffer 01 02 03 04 05>
|
|
```
|
|
|
|
### buf.toString(\[encoding\[, start\[, end\]\]\])
|
|
<!-- YAML
|
|
added: v0.1.90
|
|
-->
|
|
|
|
* `encoding` {string} The character encoding to use. **Default:** `'utf8'`.
|
|
* `start` {integer} The byte offset to start decoding at. **Default:** `0`.
|
|
* `end` {integer} The byte offset to stop decoding at (not inclusive).
|
|
**Default:** [`buf.length`][].
|
|
* Returns: {string}
|
|
|
|
Decodes `buf` to a string according to the specified character encoding in
|
|
`encoding`. `start` and `end` may be passed to decode only a subset of `buf`.
|
|
|
|
The maximum length of a string instance (in UTF-16 code units) is available
|
|
as [`buffer.constants.MAX_STRING_LENGTH`][].
|
|
|
|
```js
|
|
const buf1 = Buffer.allocUnsafe(26);
|
|
|
|
for (let i = 0; i < 26; i++) {
|
|
// 97 is the decimal ASCII value for 'a'.
|
|
buf1[i] = i + 97;
|
|
}
|
|
|
|
console.log(buf1.toString('ascii'));
|
|
// Prints: abcdefghijklmnopqrstuvwxyz
|
|
console.log(buf1.toString('ascii', 0, 5));
|
|
// Prints: abcde
|
|
|
|
const buf2 = Buffer.from('tést');
|
|
|
|
console.log(buf2.toString('hex'));
|
|
// Prints: 74c3a97374
|
|
console.log(buf2.toString('utf8', 0, 3));
|
|
// Prints: té
|
|
console.log(buf2.toString(undefined, 0, 3));
|
|
// Prints: té
|
|
```
|
|
|
|
### buf.values()
|
|
<!-- YAML
|
|
added: v1.1.0
|
|
-->
|
|
|
|
* Returns: {Iterator}
|
|
|
|
Creates and returns an [iterator][] for `buf` values (bytes). This function is
|
|
called automatically when a `Buffer` is used in a `for..of` statement.
|
|
|
|
```js
|
|
const buf = Buffer.from('buffer');
|
|
|
|
for (const value of buf.values()) {
|
|
console.log(value);
|
|
}
|
|
// Prints:
|
|
// 98
|
|
// 117
|
|
// 102
|
|
// 102
|
|
// 101
|
|
// 114
|
|
|
|
for (const value of buf) {
|
|
console.log(value);
|
|
}
|
|
// Prints:
|
|
// 98
|
|
// 117
|
|
// 102
|
|
// 102
|
|
// 101
|
|
// 114
|
|
```
|
|
|
|
### buf.write(string\[, offset\[, length\]\]\[, encoding\])
|
|
<!-- YAML
|
|
added: v0.1.90
|
|
-->
|
|
|
|
* `string` {string} String to write to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write `string`.
|
|
**Default:** `0`.
|
|
* `length` {integer} Number of bytes to write. **Default:**
|
|
`buf.length - offset`.
|
|
* `encoding` {string} The character encoding of `string`. **Default:** `'utf8'`.
|
|
* Returns: {integer} Number of bytes written.
|
|
|
|
Writes `string` to `buf` at `offset` according to the character encoding in
|
|
`encoding`. The `length` parameter is the number of bytes to write. If `buf` did
|
|
not contain enough space to fit the entire string, only part of `string` will be
|
|
written. However, partially encoded characters will not be written.
|
|
|
|
```js
|
|
const buf = Buffer.alloc(256);
|
|
|
|
const len = buf.write('\u00bd + \u00bc = \u00be', 0);
|
|
|
|
console.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);
|
|
// Prints: 12 bytes: ½ + ¼ = ¾
|
|
```
|
|
|
|
### buf.writeBigInt64BE(value\[, offset\])
|
|
### buf.writeBigInt64LE(value\[, offset\])
|
|
<!-- YAML
|
|
added: v12.0.0
|
|
-->
|
|
|
|
* `value` {bigint} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset` with specified endian
|
|
format (`writeBigInt64BE()` writes big endian, `writeBigInt64LE()` writes little
|
|
endian).
|
|
|
|
`value` is interpreted and written as a two's complement signed integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(8);
|
|
|
|
buf.writeBigInt64BE(0x0102030405060708n, 0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 01 02 03 04 05 06 07 08>
|
|
```
|
|
|
|
### buf.writeBigUInt64BE(value\[, offset\])
|
|
### buf.writeBigUInt64LE(value\[, offset\])
|
|
<!-- YAML
|
|
added: v12.0.0
|
|
-->
|
|
|
|
* `value` {bigint} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset` with specified endian
|
|
format (`writeBigUInt64BE()` writes big endian, `writeBigUInt64LE()` writes
|
|
little endian).
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(8);
|
|
|
|
buf.writeBigUInt64LE(0xdecafafecacefaden, 0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer de fa ce ca fe fa ca de>
|
|
```
|
|
|
|
### buf.writeDoubleBE(value\[, offset\])
|
|
### buf.writeDoubleLE(value\[, offset\])
|
|
<!-- YAML
|
|
added: v0.11.15
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {number} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - 8`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset` with specified endian
|
|
format (`writeDoubleBE()` writes big endian, `writeDoubleLE()` writes little
|
|
endian). `value` *should* be a valid 64-bit double. Behavior is undefined when
|
|
`value` is anything other than a 64-bit double.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(8);
|
|
|
|
buf.writeDoubleBE(123.456, 0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>
|
|
|
|
buf.writeDoubleLE(123.456, 0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>
|
|
```
|
|
|
|
### buf.writeFloatBE(value\[, offset\])
|
|
### buf.writeFloatLE(value\[, offset\])
|
|
<!-- YAML
|
|
added: v0.11.15
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {number} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset` with specified endian
|
|
format (`writeFloatBE()` writes big endian, `writeFloatLE()` writes little
|
|
endian). `value` *should* be a valid 32-bit float. Behavior is undefined when
|
|
`value` is anything other than a 32-bit float.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(4);
|
|
|
|
buf.writeFloatBE(0xcafebabe, 0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 4f 4a fe bb>
|
|
|
|
buf.writeFloatLE(0xcafebabe, 0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer bb fe 4a 4f>
|
|
```
|
|
|
|
### buf.writeInt8(value\[, offset\])
|
|
<!-- YAML
|
|
added: v0.5.0
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {integer} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - 1`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset`. `value` *should* be a valid
|
|
signed 8-bit integer. Behavior is undefined when `value` is anything other than
|
|
a signed 8-bit integer.
|
|
|
|
`value` is interpreted and written as a two's complement signed integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(2);
|
|
|
|
buf.writeInt8(2, 0);
|
|
buf.writeInt8(-2, 1);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 02 fe>
|
|
```
|
|
|
|
### buf.writeInt16BE(value\[, offset\])
|
|
### buf.writeInt16LE(value\[, offset\])
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {integer} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset` with specified endian
|
|
format (`writeInt16BE()` writes big endian, `writeInt16LE()` writes little
|
|
endian). `value` *should* be a valid signed 16-bit integer. Behavior is
|
|
undefined when `value` is anything other than a signed 16-bit integer.
|
|
|
|
`value` is interpreted and written as a two's complement signed integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(4);
|
|
|
|
buf.writeInt16BE(0x0102, 0);
|
|
buf.writeInt16LE(0x0304, 2);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 01 02 04 03>
|
|
```
|
|
|
|
### buf.writeInt32BE(value\[, offset\])
|
|
### buf.writeInt32LE(value\[, offset\])
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {integer} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset` with specified endian
|
|
format (`writeInt32BE()` writes big endian, `writeInt32LE()` writes little
|
|
endian). `value` *should* be a valid signed 32-bit integer. Behavior is
|
|
undefined when `value` is anything other than a signed 32-bit integer.
|
|
|
|
`value` is interpreted and written as a two's complement signed integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(8);
|
|
|
|
buf.writeInt32BE(0x01020304, 0);
|
|
buf.writeInt32LE(0x05060708, 4);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 01 02 03 04 08 07 06 05>
|
|
```
|
|
|
|
### buf.writeIntBE(value, offset, byteLength)
|
|
### buf.writeIntLE(value, offset, byteLength)
|
|
<!-- YAML
|
|
added: v0.11.15
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
and `byteLength` to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {integer} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - byteLength`.
|
|
* `byteLength` {integer} Number of bytes to write. Must satisfy
|
|
`0 < byteLength <= 6`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `byteLength` bytes of `value` to `buf` at the specified `offset`.
|
|
Supports up to 48 bits of accuracy. Behavior is undefined when `value` is
|
|
anything other than a signed integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(6);
|
|
|
|
buf.writeIntBE(0x1234567890ab, 0, 6);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 12 34 56 78 90 ab>
|
|
|
|
buf.writeIntLE(0x1234567890ab, 0, 6);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer ab 90 78 56 34 12>
|
|
```
|
|
|
|
### buf.writeUInt8(value\[, offset\])
|
|
<!-- YAML
|
|
added: v0.5.0
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {integer} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - 1`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset`. `value` *should* be a
|
|
valid unsigned 8-bit integer. Behavior is undefined when `value` is anything
|
|
other than an unsigned 8-bit integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(4);
|
|
|
|
buf.writeUInt8(0x3, 0);
|
|
buf.writeUInt8(0x4, 1);
|
|
buf.writeUInt8(0x23, 2);
|
|
buf.writeUInt8(0x42, 3);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 03 04 23 42>
|
|
```
|
|
|
|
### buf.writeUInt16BE(value\[, offset\])
|
|
### buf.writeUInt16LE(value\[, offset\])
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {integer} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset` with specified endian
|
|
format (`writeUInt16BE()` writes big endian, `writeUInt16LE()` writes little
|
|
endian). `value` should be a valid unsigned 16-bit integer. Behavior is
|
|
undefined when `value` is anything other than an unsigned 16-bit integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(4);
|
|
|
|
buf.writeUInt16BE(0xdead, 0);
|
|
buf.writeUInt16BE(0xbeef, 2);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer de ad be ef>
|
|
|
|
buf.writeUInt16LE(0xdead, 0);
|
|
buf.writeUInt16LE(0xbeef, 2);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer ad de ef be>
|
|
```
|
|
|
|
### buf.writeUInt32BE(value\[, offset\])
|
|
### buf.writeUInt32LE(value\[, offset\])
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {integer} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `value` to `buf` at the specified `offset` with specified endian
|
|
format (`writeUInt32BE()` writes big endian, `writeUInt32LE()` writes little
|
|
endian). `value` should be a valid unsigned 32-bit integer. Behavior is
|
|
undefined when `value` is anything other than an unsigned 32-bit integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(4);
|
|
|
|
buf.writeUInt32BE(0xfeedface, 0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer fe ed fa ce>
|
|
|
|
buf.writeUInt32LE(0xfeedface, 0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer ce fa ed fe>
|
|
```
|
|
|
|
### buf.writeUIntBE(value, offset, byteLength)
|
|
### buf.writeUIntLE(value, offset, byteLength)
|
|
<!-- YAML
|
|
added: v0.5.5
|
|
changes:
|
|
- version: v10.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/18395
|
|
description: Removed `noAssert` and no implicit coercion of the offset
|
|
and `byteLength` to `uint32` anymore.
|
|
-->
|
|
|
|
* `value` {integer} Number to be written to `buf`.
|
|
* `offset` {integer} Number of bytes to skip before starting to write. Must
|
|
satisfy `0 <= offset <= buf.length - byteLength`.
|
|
* `byteLength` {integer} Number of bytes to write. Must satisfy
|
|
`0 < byteLength <= 6`.
|
|
* Returns: {integer} `offset` plus the number of bytes written.
|
|
|
|
Writes `byteLength` bytes of `value` to `buf` at the specified `offset`.
|
|
Supports up to 48 bits of accuracy. Behavior is undefined when `value` is
|
|
anything other than an unsigned integer.
|
|
|
|
```js
|
|
const buf = Buffer.allocUnsafe(6);
|
|
|
|
buf.writeUIntBE(0x1234567890ab, 0, 6);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 12 34 56 78 90 ab>
|
|
|
|
buf.writeUIntLE(0x1234567890ab, 0, 6);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer ab 90 78 56 34 12>
|
|
```
|
|
|
|
## buffer.INSPECT_MAX_BYTES
|
|
<!-- YAML
|
|
added: v0.5.4
|
|
-->
|
|
|
|
* {integer} **Default:** `50`
|
|
|
|
Returns the maximum number of bytes that will be returned when
|
|
`buf.inspect()` is called. This can be overridden by user modules. See
|
|
[`util.inspect()`][] for more details on `buf.inspect()` behavior.
|
|
|
|
This is a property on the `buffer` module returned by
|
|
`require('buffer')`, not on the `Buffer` global or a `Buffer` instance.
|
|
|
|
## buffer.kMaxLength
|
|
<!-- YAML
|
|
added: v3.0.0
|
|
-->
|
|
|
|
* {integer} The largest size allowed for a single `Buffer` instance.
|
|
|
|
An alias for [`buffer.constants.MAX_LENGTH`][].
|
|
|
|
This is a property on the `buffer` module returned by
|
|
`require('buffer')`, not on the `Buffer` global or a `Buffer` instance.
|
|
|
|
## buffer.transcode(source, fromEnc, toEnc)
|
|
<!-- YAML
|
|
added: v7.1.0
|
|
changes:
|
|
- version: v8.0.0
|
|
pr-url: https://github.com/nodejs/node/pull/10236
|
|
description: The `source` parameter can now be a `Uint8Array`.
|
|
-->
|
|
|
|
* `source` {Buffer|Uint8Array} A `Buffer` or `Uint8Array` instance.
|
|
* `fromEnc` {string} The current encoding.
|
|
* `toEnc` {string} To target encoding.
|
|
* Returns: {Buffer}
|
|
|
|
Re-encodes the given `Buffer` or `Uint8Array` instance from one character
|
|
encoding to another. Returns a new `Buffer` instance.
|
|
|
|
Throws if the `fromEnc` or `toEnc` specify invalid character encodings or if
|
|
conversion from `fromEnc` to `toEnc` is not permitted.
|
|
|
|
Encodings supported by `buffer.transcode()` are: `'ascii'`, `'utf8'`,
|
|
`'utf16le'`, `'ucs2'`, `'latin1'`, and `'binary'`.
|
|
|
|
The transcoding process will use substitution characters if a given byte
|
|
sequence cannot be adequately represented in the target encoding. For instance:
|
|
|
|
```js
|
|
const buffer = require('buffer');
|
|
|
|
const newBuf = buffer.transcode(Buffer.from('€'), 'utf8', 'ascii');
|
|
console.log(newBuf.toString('ascii'));
|
|
// Prints: '?'
|
|
```
|
|
|
|
Because the Euro (`€`) sign is not representable in US-ASCII, it is replaced
|
|
with `?` in the transcoded `Buffer`.
|
|
|
|
This is a property on the `buffer` module returned by
|
|
`require('buffer')`, not on the `Buffer` global or a `Buffer` instance.
|
|
|
|
## Class: SlowBuffer
|
|
<!-- YAML
|
|
deprecated: v6.0.0
|
|
-->
|
|
|
|
> Stability: 0 - Deprecated: Use [`Buffer.allocUnsafeSlow()`][] instead.
|
|
|
|
Returns an un-pooled `Buffer`.
|
|
|
|
In order to avoid the garbage collection overhead of creating many individually
|
|
allocated `Buffer` instances, by default allocations under 4KB are sliced from a
|
|
single larger allocated object.
|
|
|
|
In the case where a developer may need to retain a small chunk of memory from a
|
|
pool for an indeterminate amount of time, it may be appropriate to create an
|
|
un-pooled `Buffer` instance using `SlowBuffer` then copy out the relevant bits.
|
|
|
|
```js
|
|
// Need to keep around a few small chunks of memory.
|
|
const store = [];
|
|
|
|
socket.on('readable', () => {
|
|
let data;
|
|
while (null !== (data = readable.read())) {
|
|
// Allocate for retained data.
|
|
const sb = SlowBuffer(10);
|
|
|
|
// Copy the data into the new allocation.
|
|
data.copy(sb, 0, 0, 10);
|
|
|
|
store.push(sb);
|
|
}
|
|
});
|
|
```
|
|
|
|
Use of `SlowBuffer` should be used only as a last resort *after* a developer
|
|
has observed undue memory retention in their applications.
|
|
|
|
### new SlowBuffer(size)
|
|
<!-- YAML
|
|
deprecated: v6.0.0
|
|
-->
|
|
|
|
> Stability: 0 - Deprecated: Use [`Buffer.allocUnsafeSlow()`][] instead.
|
|
|
|
* `size` {integer} The desired length of the new `SlowBuffer`.
|
|
|
|
Allocates a new `Buffer` of `size` bytes. If `size` is larger than
|
|
[`buffer.constants.MAX_LENGTH`][] or smaller than 0, [`ERR_INVALID_OPT_VALUE`][]
|
|
is thrown. A zero-length `Buffer` is created if `size` is 0.
|
|
|
|
The underlying memory for `SlowBuffer` instances is *not initialized*. The
|
|
contents of a newly created `SlowBuffer` are unknown and may contain sensitive
|
|
data. Use [`buf.fill(0)`][`buf.fill()`] to initialize a `SlowBuffer` with
|
|
zeroes.
|
|
|
|
```js
|
|
const { SlowBuffer } = require('buffer');
|
|
|
|
const buf = new SlowBuffer(5);
|
|
|
|
console.log(buf);
|
|
// Prints: (contents may vary): <Buffer 78 e0 82 02 01>
|
|
|
|
buf.fill(0);
|
|
|
|
console.log(buf);
|
|
// Prints: <Buffer 00 00 00 00 00>
|
|
```
|
|
|
|
## Buffer Constants
|
|
<!-- YAML
|
|
added: v8.2.0
|
|
-->
|
|
|
|
`buffer.constants` is a property on the `buffer` module returned by
|
|
`require('buffer')`, not on the `Buffer` global or a `Buffer` instance.
|
|
|
|
### buffer.constants.MAX_LENGTH
|
|
<!-- YAML
|
|
added: v8.2.0
|
|
-->
|
|
|
|
* {integer} The largest size allowed for a single `Buffer` instance.
|
|
|
|
On 32-bit architectures, this value is `(2^30)-1` (~1GB).
|
|
On 64-bit architectures, this value is `(2^31)-1` (~2GB).
|
|
|
|
This value is also available as [`buffer.kMaxLength`][].
|
|
|
|
### buffer.constants.MAX_STRING_LENGTH
|
|
<!-- YAML
|
|
added: v8.2.0
|
|
-->
|
|
|
|
* {integer} The largest length allowed for a single `string` instance.
|
|
|
|
Represents the largest `length` that a `string` primitive can have, counted
|
|
in UTF-16 code units.
|
|
|
|
This value may depend on the JS engine that is being used.
|
|
|
|
[RFC 1345]: https://tools.ietf.org/html/rfc1345
|
|
[RFC 4648, Section 5]: https://tools.ietf.org/html/rfc4648#section-5
|
|
[WHATWG Encoding Standard]: https://encoding.spec.whatwg.org/
|
|
[`ArrayBuffer#slice()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/slice
|
|
[`ArrayBuffer`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer
|
|
[`Buffer.alloc()`]: #buffer_class_method_buffer_alloc_size_fill_encoding
|
|
[`Buffer.allocUnsafe()`]: #buffer_class_method_buffer_allocunsafe_size
|
|
[`Buffer.allocUnsafeSlow()`]: #buffer_class_method_buffer_allocunsafeslow_size
|
|
[`Buffer.from(array)`]: #buffer_class_method_buffer_from_array
|
|
[`Buffer.from(arrayBuf)`]: #buffer_class_method_buffer_from_arraybuffer_byteoffset_length
|
|
[`Buffer.from(buffer)`]: #buffer_class_method_buffer_from_buffer
|
|
[`Buffer.from(string)`]: #buffer_class_method_buffer_from_string_encoding
|
|
[`Buffer.poolSize`]: #buffer_class_property_buffer_poolsize
|
|
[`DataView`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView
|
|
[`ERR_INVALID_BUFFER_SIZE`]: errors.html#ERR_INVALID_BUFFER_SIZE
|
|
[`ERR_INVALID_OPT_VALUE`]: errors.html#ERR_INVALID_OPT_VALUE
|
|
[`ERR_OUT_OF_RANGE`]: errors.html#ERR_OUT_OF_RANGE
|
|
[`JSON.stringify()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify
|
|
[`SharedArrayBuffer`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer
|
|
[`String#indexOf()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf
|
|
[`String#lastIndexOf()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/lastIndexOf
|
|
[`String.prototype.length`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/length
|
|
[`TypedArray.from()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/from
|
|
[`TypedArray`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
|
|
[`Uint32Array`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array
|
|
[`Uint8Array`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array
|
|
[`buf.buffer`]: #buffer_buf_buffer
|
|
[`buf.compare()`]: #buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend
|
|
[`buf.entries()`]: #buffer_buf_entries
|
|
[`buf.fill()`]: #buffer_buf_fill_value_offset_end_encoding
|
|
[`buf.indexOf()`]: #buffer_buf_indexof_value_byteoffset_encoding
|
|
[`buf.keys()`]: #buffer_buf_keys
|
|
[`buf.length`]: #buffer_buf_length
|
|
[`buf.slice()`]: #buffer_buf_slice_start_end
|
|
[`buf.values()`]: #buffer_buf_values
|
|
[`buffer.constants.MAX_LENGTH`]: #buffer_buffer_constants_max_length
|
|
[`buffer.constants.MAX_STRING_LENGTH`]: #buffer_buffer_constants_max_string_length
|
|
[`buffer.kMaxLength`]: #buffer_buffer_kmaxlength
|
|
[`util.inspect()`]: util.html#util_util_inspect_object_options
|
|
[iterator]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols
|