Add base64 decoder and change existing base64 encoder.

sdk/lib/crypto/crypto_base.dart

Index: sdk/lib/crypto/crypto_base.dart
diff --git a/sdk/lib/crypto/crypto_base.dart b/sdk/lib/crypto/crypto_base.dart
index d1666b51ed9a7bafb0a5537301fb92a67b2577d5..4737e1db6407432804686893f0c665d8b25b907f 100644
--- a/sdk/lib/crypto/crypto_base.dart
+++ b/sdk/lib/crypto/crypto_base.dart
@@ -123,13 +123,49 @@ abstract class CryptoUtils {
   }
 
   /**
-   * Converts a list of bytes (for example a message digest) into a
-   * base64 encoded string optionally broken up in to lines of
-   * [lineLength] chars separated by '\r\n'.
+   * Converts a list of bytes into a Base 64 encoded string.
+   *
+   * The list can be any list of integers in the range 0..255,
+   * for example a message digest.
+   *
+   * If [addLineSeparator] is true, the resulting string will  be
+   * broken into lines of 76 characters, separated by "\r\n".
+   *
+   * If [urlSafe] is true, the result is URL and filename safe.
+   *
+   * If [usePadding] is false, Extra padding characters ('=') are not

[floitsch, 2013/03/22 17:22:05]

If [usePadding] is false, no extra padding characters ('=') are appended to the
output.

[mdakin1, 2013/03/25 17:05:02]

Done.

+   * appended to output.
+   *
+   * Based on RFC 4648 http://tools.ietf.org/html/rfc4648
+   *
+   */
+  static String bytesToBase64(List<int> bytes,
+                              {bool urlSafe : false,
+                               bool addLineSeparator : false,
+                               bool usePadding : true}) {
+    return _CryptoUtils.bytesToBase64(bytes,
+                                      urlSafe,
+                                      addLineSeparator,
+                                      usePadding);
+  }
+
+
+  /**
+   * Converts a Base 64 encoded String into list of bytes.
+   *
+   * Decoder ignores "\r\n" sequences from input. By default it also ignores
+   * all illegal characters unless [ignoreErrors] is false.
+   *
+   * Accepts both URL safe and unsafe Base 64 encoded strings.
+   *
+   * Returns an empty list if [input] is null.

[floitsch, 2013/03/22 17:22:05]

Why not throw a null-pointer exception? (in which case we shouldn't say anything
about `null` in the comment.

[mdakin1, 2013/03/25 17:05:02]

Done, no mention of null anymore.

+   *
+   * Based on RFC 4648 http://tools.ietf.org/html/rfc4648
    */
-  static String bytesToBase64(List<int> bytes, [int lineLength]) {
-    return _CryptoUtils.bytesToBase64(bytes, lineLength);
+  static List<int> base64StringToBytes(String input, {bool ignoreErrors : true}) {
+    return _CryptoUtils.base64StringToBytes(input, ignoreErrors);
   }
+
 }
 
 /**