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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | 4x 4x 201021x 201021x 201021x 201021x 201021x 201021x | /** * @license * Copyright 2019 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import { bufferToBase64UrlSafe } from './buffer-to-base64-url-safe'; /** Generates a new FID using random values from Web Crypto API. */ export function generateFid(): string { // A valid FID has exactly 22 base64 characters, which is 132 bits, or 16.5 // bytes. our implementation generates a 17 byte array instead. const fidByteArray = new Uint8Array(17); crypto.getRandomValues(fidByteArray); // Replace the first 4 random bits with the constant FID header of 0b0111. fidByteArray[0] = 0b01110000 + (fidByteArray[0] % 0b00010000); return encode(fidByteArray); } /** Converts a FID Uint8Array to a base64 string representation. */ function encode(fidByteArray: Uint8Array): string { const b64String = bufferToBase64UrlSafe(fidByteArray); // Remove the 23rd character that was added because of the extra 4 bits at the // end of our 17 byte array, and the '=' padding. return b64String.substr(0, 22); } |