common/packages/util/docs/u8a.md

u8a

Utility methods to convert to and from Uint8Array objects

• u8aConcat Creates a concatenated Uint8Array from the inputs.
• u8aFixLength Shifts a Uint8Array to a specific bitLength
• u8aFromBn Creates a Uint8Array value from a BN object.
• u8aFromBuffer Creates a Uint8Array value from a Buffer object.
• u8aFromHex Creates a Uint8Array value from a hex string.
• u8aFromString Creates a Uint8Array object from a string.
• u8aFromUtf8 Creates a Uint8Array object from a utf-8 string.
• u8aToBn Creates a BN from a Uint8Array object.
• u8aToBuffer Creates a Buffer object from a hex string.
• u8aToHex Creates a hex string from a Uint8Array object.
• u8aToString Creates a string from a Uint8Array object.
• u8aToU8a Creates a Uint8Array value from a Uint8Array bignumber or hex input.
• u8aToUtf8 Creates a utf-8 string from a Uint8Array object.

u8aConcat

Creates a concatenated Uint8Array from the inputs.

u8aConcat (...values: Array<Uint8Array | string>): Uint8Array

Concatenates the input arrays into a single UInt8Array.

import { u8aConcat } from '@polkadot/util';

u8aConcat(
new Uint8Array([1, 2, 3]),
new Uint8Array([4, 5, 6])
); // [1, 2, 3, 4, 5, 6]

u8aFixLength

Shifts a Uint8Array to a specific bitLength

u8aFixLength (value: string, bitLength: number = -1, withPadding: boolean = false): string

Returns a uint8Array with the specified number of bits contained in the return value. (If bitLength is -1, length checking is not done). Values with more bits are trimmed to the specified length.

import { u8aFixLength } from '@polkadot/util';

u8aFixLength('0x12') // => 0x12
u8aFixLength('0x12', 16) // => 0x0012
u8aFixLength('0x1234', 8) // => 0x12

u8aFromBn

Creates a Uint8Array value from a BN object. (alias of bnToU8a)

u8aFromBn (value?: BN): Uint8Array

u8aFromBuffer

Creates a Uint8Array value from a Buffer object. (alias of bufferToU8a)

u8aFromBuffer (value?: Buffer): Uint8Array

u8aFromHex

Creates a Uint8Array value from a hex string. (alias of hexToU8a)

u8aFromHex (value?: string): Uint8Array

u8aFromString

Creates a Uint8Array object from a string.

u8aFromString (value: string): UInt8Array

String input values return the actual encoded UInt8Array.

import { u8aFromString } from '@polkadot/util';

u8aFromString('hello'); // [0x68, 0x65, 0x6c, 0x6c, 0x6f]

u8aFromUtf8

Creates a Uint8Array object from a utf-8 string.

u8aFromUtf8 (value?: string): UInt8Array

String input values return the actual encoded UInt8Array. null or undefined values returns an empty encoded array.

import { u8aFromUtf8 } from '@polkadot/util';

u8aFromUtf8('hello'); // [0x68, 0x65, 0x6c, 0x6c, 0x6f]

u8aToBn

Creates a BN from a Uint8Array object.

u8aToHex (value?: Uint8Array, isLe: boolean = false): BN

UInt8Array input values return the actual BN. null or undefined values returns an 0x0 value.

import { u8aToBn } from '@polkadot/util';

u8aToHex(new Uint8Array([0x68, 0x65, 0x6c, 0x6c, 0xf])); // 0x68656c0f

u8aToBuffer

Creates a Buffer object from a hex string.

u8aToBuffer (value?: UInt8Array): Buffer

null inputs returns an empty Buffer result. UInt8Array input values return the actual bytes value converted to a Buffer. Anything that is not a UInt8Array throws an error.

import { u8aToBuffer } from '@polkadot/util';

console.log('Buffer', u8aToBuffer('0x123480001f'));

u8aToHex

Creates a hex string from a Uint8Array object.

u8aToHex (value?: UInt8Array): string

UInt8Array input values return the actual hex string. null or undefined values returns an 0x string.

import { u8aToHex } from '@polkadot/util';

u8aToHex(new Uint8Array([0x68, 0x65, 0x6c, 0x6c, 0xf])); // 0x68656c0f

u8aToString

Creates a string from a Uint8Array object.

u8aToString (value?: UInt8Array): string

UInt8Array input values return the actual decoded string. null or undefined values returns an empty string.

import { u8aToString } from '@polkadot/util';

u8aToString(new Uint8Array([21,23,45,67])); // 21,23,45,67

u8aToU8a

Creates a Uint8Array value from a Uint8Array bignumber or hex input.

u8aToU8a (value?: Uint8Array | string): Uint8Array

null inputs returns a [] result, Uint8Array values returns the value, hex strings returns a Uint8Array representation.

import { u8aToU8a } from '@polkadot/util';

u8aToU8a(new Uint8Array([0x12, 0x34]); // => Uint8Array([0x12, 0x34])
u8aToU8a(0x1234); // => Uint8Array([0x12, 0x34])

u8aToUtf8

Creates a utf-8 string from a Uint8Array object.

u8aToUtf8 (value?: UInt8Array): string

UInt8Array input values return the actual decoded utf-8 string. null or undefined values returns an empty string.

import { u8aToUtf8 } from '@polkadot/util';

u8aToUtf8(new Uint8Array([0x68, 0x65, 0x6c, 0x6c, 0x6f])); // hello