, if there is no such instance currently associated; otherwise, they throw <CODE>std::ios_base::failure</CODE>.  The <CODE>T</CODE> constructor must take all arguments other than the first by value or <CODE>const</CODE> reference. 
</P>
<P>
    It is not possible to specify a custom buffer size or putback buffer size using these members.
</P>

<A NAME="stream_buffer_is_open"></A>
<H4><CODE>stream_buffer::is_open</CODE></H4>
<PRE>    <SPAN CLASS="keyword">bool</SPAN> <B>is_open</B>() <SPAN CLASS="keyword">co