@caido/quickjs-types / llrt/buffer

llrt/buffer

Interfaces

Buffer

Extends

Uint8Array

Indexable

[index: number]: number

Methods

copy()

copy(target: Uint8Array, targetStart?: number, sourceStart?: number, sourceEnd?: number): number

Copies data from a region of buf to a region in target, even if the targetmemory region overlaps with buf.

TypedArray.prototype.set() performs the same operation, and is available for all TypedArrays, including Buffers, although it takes different function arguments.

import { Buffer } from 'buffer';

// 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);
// This is equivalent to:
// buf2.set(buf1.subarray(16, 20), 8);

console.log(buf2.toString('ascii', 0, 25));
// Prints: !!!!!!!!qrst!!!!!!!!!!!!!

import { Buffer } from 'buffer';

// 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

Parameters

Parameter	Type	Description
`target`	`Uint8Array`	A `Buffer` or Uint8Array to copy into.
`targetStart`?	`number`	The offset within `target` at which to begin writing.
`sourceStart`?	`number`	The offset within `buf` from which to begin copying.
`sourceEnd`?	`number`	The offset within `buf` at which to stop copying (not inclusive).

Returns

number

The number of bytes copied.

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

writeDoubleBE()

writeDoubleBE(value: number, offset?: number): number

Writes value to buf at the specified offset as big-endian. The value must be a JavaScript number. Behavior is undefined when value is anything other than a JavaScript number.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeDoubleBE(123.456, 0);

console.log(buf);
// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>

Parameters

Parameter	Type	Description
`value`	`number`	Number to be written to `buf`.
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 8`.

Returns

number

offset plus the number of bytes written.

writeDoubleLE()

writeDoubleLE(value: number, offset?: number): number

Writes value to buf at the specified offset as little-endian. The value must be a JavaScript number. Behavior is undefined when value is anything other than a JavaScript number.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeDoubleLE(123.456, 0);

console.log(buf);
// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>

Parameters

Parameter	Type	Description
`value`	`number`	Number to be written to `buf`.
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 8`.

Returns

number

offset plus the number of bytes written.

writeFloatBE()

writeFloatBE(value: number, offset?: number): number

Writes value to buf at the specified offset as big-endian. Behavior is undefined when value is anything other than a JavaScript number.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeFloatBE(0xcafebabe, 0);

console.log(buf);
// Prints: <Buffer 4f 4a fe bb>

Parameters

Parameter	Type	Description
`value`	`number`	Number to be written to `buf`.
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`.

Returns

number

offset plus the number of bytes written.

writeFloatLE()

writeFloatLE(value: number, offset?: number): number

Writes value to buf at the specified offset as little-endian. Behavior is undefined when value is anything other than a JavaScript number.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeFloatLE(0xcafebabe, 0);

console.log(buf);
// Prints: <Buffer bb fe 4a 4f>

Parameters

Parameter	Type	Description
`value`	`number`	Number to be written to `buf`.
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`.

Returns

number

offset plus the number of bytes written.

writeInt16BE()

writeInt16BE(value: number, offset?: number): number

Writes value to buf at the specified offset as big-endian. The value must be a valid signed 16-bit integer. Behavior is undefined when value is anything other than a signed 16-bit integer.

The value is interpreted and written as a two's complement signed integer.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt16BE(0x0102, 0);

console.log(buf);
// Prints: <Buffer 01 02>

Parameters

Parameter	Type	Description
`value`	`number`	Number to be written to `buf`.
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`.

Returns

number

offset plus the number of bytes written.

writeInt16LE()

writeInt16LE(value: number, offset?: number): number

Writes value to buf at the specified offset as little-endian. The value must be a valid signed 16-bit integer. Behavior is undefined when value is anything other than a signed 16-bit integer.

The value is interpreted and written as a two's complement signed integer.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt16LE(0x0304, 0);

console.log(buf);
// Prints: <Buffer 04 03>

Parameters

Parameter	Type	Description
`value`	`number`	Number to be written to `buf`.
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`.

Returns

number

offset plus the number of bytes written.

writeInt32BE()

writeInt32BE(value: number, offset?: number): number

Writes value to buf at the specified offset as big-endian. The value must be a valid signed 32-bit integer. Behavior is undefined when value is anything other than a signed 32-bit integer.

The value is interpreted and written as a two's complement signed integer.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeInt32BE(0x01020304, 0);

console.log(buf);
// Prints: <Buffer 01 02 03 04>

Parameters

Parameter	Type	Description
`value`	`number`	-
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`.

Returns

number

offset plus the number of bytes written.

writeInt32LE()

writeInt32LE(value: number, offset?: number): number

Writes value to buf at the specified offset as little-endian. The value must be a valid signed 32-bit integer. Behavior is undefined when value is anything other than a signed 32-bit integer.

The value is interpreted and written as a two's complement signed integer.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeInt32LE(0x05060708, 0);

console.log(buf);
// Prints: <Buffer 08 07 06 05>

Parameters

Parameter	Type	Description
`value`	`number`	Number to be written to `buf`.
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`.

Returns

number

offset plus the number of bytes written.

writeInt8()

writeInt8(value: number, offset?: number): number

Writes value to buf at the specified offset. value must 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.

import { Buffer } from 'buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt8(2, 0);
buf.writeInt8(-2, 1);

console.log(buf);
// Prints: <Buffer 02 fe>

Parameters

Parameter	Type	Description
`value`	`number`	Number to be written to `buf`.
`offset`?	`number`	Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 1`.

Returns

number

offset plus the number of bytes written.

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.

llrt/buffer ​

Interfaces ​

Buffer ​

Extends ​

Indexable ​

Methods ​

copy() ​

Parameters ​

Returns ​

subarray() ​

Parameters ​

Returns ​

Overrides ​

toString() ​

Parameters ​

Returns ​

Overrides ​

writeDoubleBE() ​

Parameters ​

Returns ​

writeDoubleLE() ​

Parameters ​

Returns ​

writeFloatBE() ​

Parameters ​

Returns ​

writeFloatLE() ​

Parameters ​

Returns ​

writeInt16BE() ​

Parameters ​

Returns ​

writeInt16LE() ​

Parameters ​

Returns ​

writeInt32BE() ​

Parameters ​

Returns ​

writeInt32LE() ​

Parameters ​

Returns ​

writeInt8() ​

Parameters ​

Returns ​

BufferConstructor ​

Methods ​

alloc() ​

Parameters ​

Returns ​

byteLength() ​

Parameters ​

Returns ​

concat() ​

Parameters ​

Returns ​

from() ​

Call Signature ​

Parameters ​

Returns ​

Call Signature ​

Parameters ​

Returns ​

Call Signature ​

Parameters ​

Returns ​

Call Signature ​

Parameters ​

Returns ​

Type Aliases ​

BufferEncoding ​

WithImplicitCoercion<T> ​

Type Parameters ​

Variables ​

Buffer ​

constants ​

Type declaration ​

MAX_LENGTH ​

MAX_STRING_LENGTH ​

Functions ​

atob() ​

llrt/buffer

Interfaces

Buffer

Extends

Indexable

Methods

copy()

Parameters

Returns

subarray()

Parameters

Returns

Overrides

toString()

Parameters

Returns

Overrides

writeDoubleBE()

Parameters

Returns

writeDoubleLE()

Parameters

Returns

writeFloatBE()

Parameters

Returns

writeFloatLE()

Parameters

Returns

writeInt16BE()

Parameters

Returns

writeInt16LE()

Parameters

Returns

writeInt32BE()

Parameters

Returns

writeInt32LE()

Parameters

Returns

writeInt8()

Parameters

Returns

BufferConstructor

Methods

alloc()

Parameters

Returns

byteLength()

Parameters

Returns

concat()

Parameters

Returns

from()

Call Signature

Parameters

Returns

Call Signature

Parameters

Returns

Call Signature

Parameters

Returns

Call Signature

Parameters

Returns

Type Aliases

BufferEncoding

WithImplicitCoercion<T>

Type Parameters

Variables

Buffer

constants

Type declaration

MAX_LENGTH

MAX_STRING_LENGTH

Functions

atob()