Name came from the half-serious idea of using a smiley as the "magic cookie", part of short header that can be used to detect Smile format encoded documents.

The main idea is to allow use of specific marker, 0xFF for framing purpose -- that is, as a document separator, to allow "blind" splitting of a stream of Smile-encoded documents into chunks of documents. "Blind" here means that splitter can start at ANY byte position, looking for split marker, without having to consider document structure or token boundaries: it just "blindly" focuses on finding next (or, previous) 0xFF and knows that MUST be a document boundary.

Currently (version 1.0) byte value of 0xFE is also avoided if (but only if!) using Safe Binary Encoding setting.

Note: if not writing Binary data at all, this setting has no relevance (and byte values of 0xFF and 0xFE are not used at all either).