Switch to custom base64 implementation

Previously we used Node's API for converting to/from base64
but it limits portability of this library to defirent enviroments
include Deno

Fixes #152

.eslintrc.yml

@@ -3,7 +3,6 @@ parserOptions:
   ecmaVersion: 2020
 env:
   es6: true
-  node: true
 reportUnusedDisableDirectives: true
 plugins:
   - node
@@ -659,6 +658,8 @@ overrides:
       node/no-unpublished-import: off
       import/no-extraneous-dependencies: [error, { devDependencies: true }]
   - files: 'resources/**'
+    env:
+      node: true
     rules:
       node/no-unpublished-require: off
       node/no-sync: off

src/utils/__tests__/base64-test.js

@@ -3,8 +3,8 @@ import { expect } from 'chai';
 
 import { base64, unbase64 } from '../base64';
 
-const exampleUtf8 = 'Some examples: ❤😀';
-const exampleBase64 = 'U29tZSBleGFtcGxlczog4p2k8J+YgA==';
+const exampleUtf8 = 'Some examples:  ͢❤😀';
+const exampleBase64 = 'U29tZSBleGFtcGxlczogIM2i4p2k8J+YgA==';
 
 describe('base64 conversion', () => {
   it('converts from utf-8 to base64', () => {

src/utils/base64.js

@@ -1,9 +1,153 @@
 export type Base64String = string;
 
-export function base64(i: string): Base64String {
-  return Buffer.from(i, 'utf8').toString('base64');
+export function base64(input: string): Base64String {
+  const utf8Array = stringToUTF8Array(input);
+  let result = '';
+
+  const length = utf8Array.length;
+  const rest = length % 3;
+  for (let i = 0; i < length - rest; i += 3) {
+    const a = utf8Array[i];
+    const b = utf8Array[i + 1];
+    const c = utf8Array[i + 2];
+
+    result += first6Bits(a);
+    result += last2BitsAndFirst4Bits(a, b);
+    result += last4BitsAndFirst2Bits(b, c);
+    result += last6Bits(c);
+  }
+
+  if (rest === 1) {
+    const a = utf8Array[length - 1];
+    result += first6Bits(a) + last2BitsAndFirst4Bits(a, 0) + '==';
+  } else if (rest === 2) {
+    const a = utf8Array[length - 2];
+    const b = utf8Array[length - 1];
+    result +=
+      first6Bits(a) +
+      last2BitsAndFirst4Bits(a, b) +
+      last4BitsAndFirst2Bits(b, 0) +
+      '=';
+  }
+
+  return result;
+}
+
+function first6Bits(a: number): string {
+  return toBase64Char((a >> 2) & 63);
+}
+
+function last2BitsAndFirst4Bits(a: number, b: number): string {
+  return toBase64Char(((a << 4) | (b >> 4)) & 63);
+}
+
+function last4BitsAndFirst2Bits(b: number, c: number): string {
+  return toBase64Char(((b << 2) | (c >> 6)) & 63);
+}
+
+function last6Bits(c: number): string {
+  return toBase64Char(c & 63);
+}
+
+export function unbase64(input: Base64String): string {
+  const utf8Array = [];
+
+  for (let i = 0; i < input.length; i += 4) {
+    const a = fromBase64Char(input[i]);
+    const b = fromBase64Char(input[i + 1]);
+    const c = fromBase64Char(input[i + 2]);
+    const d = fromBase64Char(input[i + 3]);
+
+    if (a === -1 || b === -1 || c === -1 || d === -1) {
+      /*
+       * Previously we used Node's API for parsing Base64 and following code
+       * Buffer.from(i, 'utf8').toString('base64')
+       * That silently ignored incorrect input and returned empty string instead
+       * Let's keep this behaviour for a time being and hopefully fix it in the future.
+       */
+      return '';
+    }
+
+    const bitmap24 = (a << 18) | (b << 12) | (c << 6) | d;
+    utf8Array.push((bitmap24 >> 16) & 255);
+    utf8Array.push((bitmap24 >> 8) & 255);
+    utf8Array.push(bitmap24 & 255);
+  }
+
+  let paddingIndex = input.length - 1;
+  while (input[paddingIndex] === '=') {
+    --paddingIndex;
+    utf8Array.pop();
+  }
+
+  return utf8ArrayToString(utf8Array);
 }
 
-export function unbase64(i: Base64String): string {
-  return Buffer.from(i, 'base64').toString('utf8');
+const b64CharacterSet =
+  'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
+
+function toBase64Char(bitMap6: number): string {
+  return b64CharacterSet.charAt(bitMap6);
+}
+
+function fromBase64Char(base64Char: string | void): number {
+  if (base64Char === undefined) {
+    return -1;
+  }
+  return base64Char === '=' ? 0 : b64CharacterSet.indexOf(base64Char);
+}
+
+function stringToUTF8Array(input: string): Array<number> {
+  const result = [];
+  for (const utfChar of input) {
+    const code = utfChar.codePointAt(0);
+    if (code < 0x80) {
+      result.push(code);
+    } else if (code < 0x800) {
+      result.push(0xc0 | (code >> 6));
+      result.push(0x80 | (code & 0x3f));
+    } else if (code < 0x10000) {
+      result.push(0xe0 | (code >> 12));
+      result.push(0x80 | ((code >> 6) & 0x3f));
+      result.push(0x80 | (code & 0x3f));
+    } else {
+      result.push(0xf0 | (code >> 18));
+      result.push(0x80 | ((code >> 12) & 0x3f));
+      result.push(0x80 | ((code >> 6) & 0x3f));
+      result.push(0x80 | (code & 0x3f));
+    }
+  }
+  return result;
+}
+
+function utf8ArrayToString(input: Array<number>) {
+  let result = '';
+  for (let i = 0; i < input.length; ) {
+    const a = input[i++];
+    if ((a & 0x80) === 0) {
+      result += String.fromCodePoint(a);
+      continue;
+    }
+
+    const b = input[i++];
+    if ((a & 0xe0) === 0xc0) {
+      result += String.fromCodePoint(((a & 0x1f) << 6) | (b & 0x3f));
+      continue;
+    }
+
+    const c = input[i++];
+    if ((a & 0xf0) === 0xe0) {
+      result += String.fromCodePoint(
+        ((a & 0x0f) << 12) | ((b & 0x3f) << 6) | (c & 0x3f),
+      );
+      continue;
+    }
+
+    const d = input[i++];
+    result += String.fromCodePoint(
+      ((a & 0x07) << 18) | ((b & 0x3f) << 12) | ((c & 0x3f) << 6) | (d & 0x3f),
+    );
+  }
+
+  return result;
 }