+/**
+ * Encodes @len bytes of data pointed to by @src by base64 encoding.
+ * Stores them in @dest and returns the number of bytes the output
+ * takes.
+ */
+uint base64_encode(byte *dest, const byte *src, uint len);
+/**
+ * Decodes @len bytes of data pointed to by @src from base64 encoding.
+ * All invalid characters are ignored. The result is stored into @dest
+ * and length of the result is returned.
+ */
+uint base64_decode(byte *dest, const byte *src, uint len);
+
+/**
+ * Use this macro to calculate @base64_encode() output buffer size.