Add base 64 encoding to the crypto library utils.

lib/crypto/crypto_utils.dart

Index: lib/crypto/crypto_utils.dart
diff --git a/lib/crypto/crypto_utils.dart b/lib/crypto/crypto_utils.dart
index aa364b68bdcc6e4cfec6d2a01c2eef27d1cde8ea..1b9ebff362e9579cb2df4daf9120da7c7fc42e26 100644
--- a/lib/crypto/crypto_utils.dart
+++ b/lib/crypto/crypto_utils.dart
@@ -10,4 +10,46 @@ class _CryptoUtils {
     }
     return result.toString();
   }
+
+  static String bytesToBase64(List<int> bytes) {
+    final table =
+        const [ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
+                'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
+                'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
+                'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
+                'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
+                '8', '9', '+', '/' ];
+
+    var result = new StringBuffer();
+
+    // Encode all full 24-bit blocks.
+    var i = 0;
+    for (; (i + 2) < bytes.length; i += 3) {
+      var b0 = bytes[i] & 0xff;
+      var b1 = bytes[i + 1] & 0xff;
+      var b2 = bytes[i + 2] & 0xff;
+      result.add(table[b0 >> 2]);
+      result.add(table[((b0 << 4) | (b1 >> 4)) & 0x3f]);
+      result.add(table[((b1 << 2) | (b2 >> 6)) & 0x3f]);
+      result.add(table[b2 & 0x3f]);

[Søren Gjesse, 2012/05/30 13:40:08]

You need to insert \r\n for at least every 76 characters (57 bytes or 19
blocks). RFC 2045 page 24 says "The encoded output stream must be represented in
lines of no more than 76 characters each".

[Mads Ager (google), 2012/05/30 15:16:10]

http://tools.ietf.org/html/rfc4648

explicitly says in section 3.1 that implementations MUST NOT add line feeds
unless explicitly stated so. I'll add an optional parameter 'lineLength' which
can be used to specify the 76 char line length if used for MIME.

+    }
+
+    // Deal with the last non-full block if any and add padding '='.
+    if (i == bytes.length - 1) {
+      var b0 = bytes[i] & 0xff;
+      result.add(table[b0 >> 2]);
+      result.add(table[(b0 << 4) & 0x3f]);
+      result.add('=');
+      result.add('=');
+    } else if (i == bytes.length - 2) {
+      var b0 = bytes[i] & 0xff;
+      var b1 = bytes[i + 1] & 0xff;
+      result.add(table[b0 >> 2]);
+      result.add(table[((b0 << 4) | (b1 >> 4)) & 0x3f]);
+      result.add(table[(b1 << 2) & 0x3f]);
+      result.add('=');
+    }
+
+    return result.toString();
+  }
 }