Unicode/ASCII characters in QTextStream

[yren]

From the docs:

void QTextStream::setAutoDetectUnicode ( bool enabled )

If enabled is true, QTextStream will attempt to detect Unicode encoding by peeking into the stream data to see if it can find the UTF-16 or UTF-32 BOM (Byte Order Mark). If this mark is found, QTextStream will replace the current codec with the UTF codec.

Thanks! How does the auto-detect know if it is Unicode file? Does Unicode file have some kind of header?