@caido/quickjs-types / llrt/buffer

llrt/buffer

Interfaces

Buffer

Extends

• Uint8Array

Indexable

[index: number]: number

Methods

subarray()

subarray(start?: number, end?: number): 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.

This method is inherited from TypedArray.prototype.subarray().

Modifying the new Buffer slice will modify the memory in the original Bufferbecause the allocated memory of the two objects overlap.

import { Buffer } from 'buffer';

// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte
// from the original `Buffer`.

const buf1 = Buffer.alloc(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.

import { Buffer } from 'buffer';

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).)

Parameters

Parameter	Type	Description
start?	number	Where the new Buffer will start.
end?	number	Where the new Buffer will end (not inclusive).

Returns

Buffer

Overrides

Uint8Array.subarray

toString()

toString(encoding?: BufferEncoding): string

Decodes buf to a string according to the specified character encoding inencoding.

If encoding is 'utf8' and a byte sequence in the input is not valid UTF-8, then each invalid byte is replaced with the replacement character U+FFFD.

import { Buffer } from 'buffer';

const buf1 = Buffer.alloc(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

console.log(buf1.toString('utf8'));
// Prints: abcdefghijklmnopqrstuvwxyz

const buf2 = Buffer.from('tést');

console.log(buf2.toString('hex'));
// Prints: 74c3a97374

Parameters

Parameter	Type	Description
encoding?	BufferEncoding	The character encoding to use.

Returns

string

Overrides

Uint8Array.toString

---

BufferConstructor

Methods

alloc()

alloc(size: number, fill?: string | number | Uint8Array, encoding?: BufferEncoding): Buffer

Allocates a new Buffer of size bytes. If fill is undefined, the Buffer will be zero-filled.

import { Buffer } from 'buffer';

const buf = Buffer.alloc(5);

console.log(buf);
// Prints: <Buffer 00 00 00 00 00>

If fill is specified, the allocated Buffer will be initialized by calling Buffer.alloc(size, fill).

import { Buffer } from 'buffer';

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 Buffer.aloc(size, fill, encoding).

import { Buffer } from 'buffer';

const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');

console.log(buf);
// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>

Parameters

Parameter	Type	Description
size	number	The desired length of the new Buffer.
fill?	string | number | Uint8Array	A value to pre-fill the new Buffer with.
encoding?	BufferEncoding	If fill is a string, this is its encoding.

Returns

Buffer

byteLength()

byteLength(string: string | ArrayBuffer | SharedArrayBuffer | ArrayBufferView | Buffer, encoding?: BufferEncoding): number

Returns the byte length of a string when encoded using encoding. This is not the same as String.prototype.length, which does not account for the encoding that is used to convert the string into bytes.

import { Buffer } from 'buffer';

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](https://developer.mozilla.org/en-US/docs/Web/JavaScript/- Reference/Global_Objects/TypedArray)/ArrayBuffer/[SharedArrayBuffer](https://develop- er.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer), the byte length as reported by .byteLengthis returned.

Parameters

Parameter	Type	Description
string	string | ArrayBuffer | SharedArrayBuffer | ArrayBufferView | Buffer	A value to calculate the length of.
encoding?	BufferEncoding	If string is a string, this is its encoding.

Returns

number

The number of bytes contained within string.

concat()

concat(list: readonly Uint8Array[], totalLength?: number): 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 by adding their lengths.

If totalLength is provided, it is coerced to an unsigned integer. If the combined length of the Buffers in list exceeds totalLength, the result is truncated to totalLength.

import { Buffer } from 'buffer';

// 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

Parameters

Parameter	Type	Description
list	readonly Uint8Array[]	List of Buffer or Uint8Array instances to concatenate.
totalLength?	number	Total length of the Buffer instances in list when concatenated.

Returns

Buffer

from()

Call Signature

from(arrayBuffer: WithImplicitCoercion<ArrayBuffer | SharedArrayBuffer>, byteOffset?: number, length?: number): Buffer

Allocates a new Buffer using an array of bytes in the range 0 – 255.

Parameters

Parameter	Type
arrayBuffer	WithImplicitCoercion<ArrayBuffer | SharedArrayBuffer>
byteOffset?	number
length?	number

Returns

Buffer

Call Signature

from(data: Uint8Array | readonly number[]): Buffer

Creates a new Buffer using the passed

Parameters

Parameter	Type	Description
data	Uint8Array | readonly number[]	data to create a new Buffer

Returns

Buffer

Call Signature

from(data: WithImplicitCoercion<string | Uint8Array | readonly number[]>): Buffer

Parameters

Parameter	Type
data	WithImplicitCoercion<string | Uint8Array | readonly number[]>

Returns

Buffer

Call Signature

from(str: WithImplicitCoercion<string> | { [toPrimitive]: string; }, encoding?: BufferEncoding): Buffer

Creates a new Buffer containing the given JavaScript string {str}. If provided, the {encoding} parameter identifies the character encoding. If not provided, {encoding} defaults to 'utf8'.

Parameters

Parameter	Type
str	WithImplicitCoercion<string> | { [toPrimitive]: string; }
encoding?	BufferEncoding

Returns

Buffer

Type Aliases

BufferEncoding

BufferEncoding: "hex" | "base64" | "utf-8" | "utf8" | "unicode-1-1-utf8" | "utf-16le" | "utf16le" | "utf-16" | "utf16" | "utf-16be" | "utf16be" | "windows-1252" | "ansi_x3.4-1968" | "ascii" | "cp1252" | "cp819" | "csisolatin1" | "ibm819" | "iso-8859-1" | "iso-ir-100" | "iso8859-1" | "iso88591" | "iso_8859-1" | "iso_8859-1:1987" | "l1" | "latin1" | "us-ascii" | "x-cp1252"

---

WithImplicitCoercion<T>

WithImplicitCoercion<T>: T | { valueOf: T; }

Type Parameters

Type Parameter
T

Variables

Buffer

Buffer: BufferConstructor

---

constants

const constants: object

Type declaration

MAX_LENGTH

MAX_LENGTH: number

MAX_STRING_LENGTH

MAX_STRING_LENGTH: number

Functions

atob()

atob(data: string): string

Decodes a string of Base64-encoded data into bytes, and encodes those bytes into a string using UTF-8.

The data may be any JavaScript-value that can be coerced into a string.

Parameters

Parameter	Type	Description
data	string	The Base64-encoded input string.

Returns

string

Legacy

Use Buffer.from(data, 'base64') instead.

---

btoa()

btoa(data: string): string

Decodes a string into bytes using UTF-8, and encodes those bytes into a string using Base64.

The data may be any JavaScript-value that can be coerced into a string.

Parameters

Parameter	Type	Description
data	string	An ASCII (Latin1) string.

Returns

string

Legacy

Use buf.toString('base64') instead.