denoland-deno/js/get_random_values.ts

// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
import * as dispatch from "./dispatch";
import { sendSync } from "./dispatch_json";
import { assert } from "./util";

/** Synchronously collects cryptographically secure random values. The
 * underlying CSPRNG in use is Rust's `rand::rngs::ThreadRng`.
 *
 *       const arr = new Uint8Array(32);
 *       crypto.getRandomValues(arr);
 */
export function getRandomValues<
  T extends
    | Int8Array
    | Uint8Array
    | Uint8ClampedArray
    | Int16Array
    | Uint16Array
    | Int32Array
    | Uint32Array
>(typedArray: T): T {
  assert(typedArray !== null, "Input must not be null");
  assert(typedArray.length <= 65536, "Input must not be longer than 65536");
  const ui8 = new Uint8Array(
    typedArray.buffer,
    typedArray.byteOffset,
    typedArray.byteLength
  );
  sendSync(dispatch.OP_GET_RANDOM_VALUES, {}, ui8);
  return typedArray;
}