@polkadot/util
Version:
A collection of useful utilities for @polkadot
32 lines (31 loc) • 1.06 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.u8aFixLength = u8aFixLength;
/**
* @name u8aFixLength
* @summary Shifts a Uint8Array to a specific bitLength
* @description
* 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.
* @example
* <BR>
*
* ```javascript
* import { u8aFixLength } from '@polkadot/util';
*
* u8aFixLength('0x12') // => 0x12
* u8aFixLength('0x12', 16) // => 0x0012
* u8aFixLength('0x1234', 8) // => 0x12
* ```
*/
function u8aFixLength(value, bitLength = -1, atStart = false) {
const byteLength = Math.ceil(bitLength / 8);
if (bitLength === -1 || value.length === byteLength) {
return value;
}
else if (value.length > byteLength) {
return value.subarray(0, byteLength);
}
const result = new Uint8Array(byteLength);
result.set(value, atStart ? 0 : (byteLength - value.length));
return result;
}