add: base64url support

Using string replaceAll since base64 is external base64-js.
Dependency does not yet support base64url beatgammit/base64-js#53

index.js

@@ -396,6 +396,7 @@ Buffer.isEncoding = function isEncoding (encoding) {
     case 'ascii':
     case 'latin1':
     case 'binary':
+    case 'base64url':
     case 'base64':
     case 'ucs2':
     case 'ucs-2':
@@ -544,8 +545,9 @@ function slowToString (encoding, start, end) {
       case 'binary':
         return latin1Slice(this, start, end)
 
+      case 'base64url':
       case 'base64':
-        return base64Slice(this, start, end)
+        return base64Slice(this, start, end, encoding)
 
       case 'ucs2':
       case 'ucs-2':
@@ -871,8 +873,9 @@ function asciiWrite (buf, string, offset, length) {
   return blitBuffer(asciiToBytes(string), buf, offset, length)
 }
 
-function base64Write (buf, string, offset, length) {
-  return blitBuffer(base64ToBytes(string), buf, offset, length)
+function base64Write (buf, string, offset, length, encoding) {
+  const b64 = encoding === 'base64url' ? base64urlToBase64(string) : string
+  return blitBuffer(base64ToBytes(b64), buf, offset, length)
 }
 
 function ucs2Write (buf, string, offset, length) {
@@ -930,9 +933,11 @@ Buffer.prototype.write = function write (string, offset, length, encoding) {
       case 'binary':
         return asciiWrite(this, string, offset, length)
 
+      case 'base64url':
       case 'base64':
+        // console.log(encoding, '::', string)
         // Warning: maxLength not taken into account in base64Write
-        return base64Write(this, string, offset, length)
+        return base64Write(this, string, offset, length, encoding)
 
       case 'ucs2':
       case 'ucs-2':
@@ -955,12 +960,14 @@ Buffer.prototype.toJSON = function toJSON () {
   }
 }
 
-function base64Slice (buf, start, end) {
+function base64Slice (buf, start, end, encoding) {
+  let b64
   if (start === 0 && end === buf.length) {
-    return base64.fromByteArray(buf)
+    b64 = base64.fromByteArray(buf)
   } else {
-    return base64.fromByteArray(buf.slice(start, end))
+    b64 = base64.fromByteArray(buf.slice(start, end))
   }
+  return encoding === 'base64url' ? base64urlFromBase64(b64) : b64
 }
 
 function utf8Slice (buf, start, end) {
@@ -1945,6 +1952,23 @@ function boundsError (value, length, type) {
 
 const INVALID_BASE64_RE = /[^+/0-9A-Za-z-_]/g
 
+const BASE64_CHAR_62 = '+'
+const BASE64_CHAR_63 = '/'
+const BASE64URL_CHAR_62 = '-'
+const BASE64URL_CHAR_63 = '_'
+
+function base64urlToBase64 (str) {
+  return str
+    .replaceAll(BASE64URL_CHAR_62, BASE64_CHAR_62)
+    .replaceAll(BASE64URL_CHAR_63, BASE64_CHAR_63)
+}
+
+function base64urlFromBase64 (str) {
+  return str
+    .replaceAll(BASE64_CHAR_62, BASE64URL_CHAR_62)
+    .replaceAll(BASE64_CHAR_63, BASE64URL_CHAR_63)
+}
+
 function base64clean (str) {
   // Node takes equal signs as end of the Base64 encoding
   str = str.split('=')[0]

test/base64.js

@@ -53,3 +53,21 @@ test('base64: high byte', function (t) {
   )
   t.end()
 })
+
+test('base64url: convert to/from base64', function (t) {
+  const base64url = '8J-Ps--4j_Cfj7PvuI8='
+  const base64 = '8J+Ps++4j/Cfj7PvuI8='
+  const text = '🏳️🏳️'
+
+  const base64urlBuf = new B(base64url, 'base64url')
+  t.equal(base64urlBuf.toString('base64'), base64)
+  t.equal(base64urlBuf.toString(), text)
+
+  const base64Buf = new B(base64, 'base64')
+  t.equal(base64Buf.toString('base64url'), base64url)
+  t.equal(base64Buf.toString(), text)
+
+  const buf = new B(text)
+  t.equal(buf.toString('base64url'), base64url)
+  t.end()
+})