Rossette library for Unicode

Hi All,

Can anyone, who has worked with Rossette library for handling Unicode characters, clarify my following doubts ?

1. Rosette library defines a class bt_string for holding 8 bit strings. It is possible to create a non uncode string from Unicode string using ExternalEncoding class. The sample code is as follows -

bt_string sjisHello("\u0065\u23ff", ExternalEncoding::ShiftJISMS);

In the above code the unicode string (the first arument in the contructor) will be converted to Shift_JIS. 
Now my question is Shift_JIS supports multibytes characters. But bt_string can support only single byte (8-bit) characters . So in that case how it works ?

2. Now the bt_string class is different than normal character array of C ? In both the cases single byte charcaters are supported.


Thanks in advance,
Sourav