base64.ts

/**
 * @license
 * Copyright 2020 Google LLC
 *
 * 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 { base64, DecodeBase64StringError } from '@firebase/util';

import { Base64DecodeError } from '../../util/base64_decode_error';

// WebSafe uses a different URL-encoding safe alphabet that doesn't match
// the encoding used on the backend.
const WEB_SAFE = false;

/** Converts a Base64 encoded string to a binary string. */
export function decodeBase64(encoded: string): string {
  try {
    return String.fromCharCode.apply(
      null,
      // We use `decodeStringToByteArray()` instead of `decodeString()` since
      // `decodeString()` returns Unicode strings, which doesn't match the values
      // returned by `atob()`'s Latin1 representation.
      base64.decodeStringToByteArray(encoded, WEB_SAFE)
    );
  } catch (e) {
    if (e instanceof DecodeBase64StringError) {
      throw new Base64DecodeError('Invalid base64 string: ' + e);
    } else {
      throw e;
    }
  }
}

/** Converts a binary string to a Base64 encoded string. */
export function encodeBase64(raw: string): string {
  const bytes: number[] = [];
  for (let i = 0; i < raw.length; i++) {
    bytes[i] = raw.charCodeAt(i);
  }
  return base64.encodeByteArray(bytes, WEB_SAFE);
}

/** True if and only if the Base64 conversion functions are available. */
export function isBase64Available(): boolean {
  return true;
}