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<H1 CLASS="title">Flushable</H1>
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<H2>Description</H2>
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A Flushable Sink or OutputFilter provides a means for the user to request that all buffered characters be sent downstream.
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<H2>Refinement of</H2>
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<H2>Associated Types</H2>
<P>Same as <A HREF="filter.html#types">Filter</A> or <A HREF="device.html#types">Device</A>, with the following additional requirement:</P>
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<TR><TD>Category</TD><TD>A type convertible to <A HREF="../guide/traits.html#category_tags"><CODE>flushable_tag</CODE></A></TD></TR>
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<H2>Notation</H2>
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<TR><TD><CODE>F</CODE></TD><TD>-</TD><TD>A type which is a model of Flushable</TD></TR>
<TR><TD><CODE>D</CODE></TD><TD>-</TD><TD>A type which is a model of <A HREF="device.html">Sink</A>, with the same character type as <CODE>F</CODE></TD></TR>
<TR><TD><CODE>f</CODE></TD><TD>-</TD><TD>Object of type <CODE>F</CODE></TD></TR>
<TR><TD><CODE>d</CODE></TD><TD>-</TD><TD>Object of type <CODE>D</CODE></TD></TR>
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<H2>Valid Expressions / Semantics</H2>
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<TR><TH>Expression</TH><TH>Expression Type</TH><TH>Precondition</TH><TH>Semantics</TH></TR>
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<PRE CLASS="plain_code"><CODE><A HREF="../functions/flush.html#flush_device">boost::iostreams::flush</A>(f)</CODE></PRE>
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<TD><CODE>bool</CODE></TD>
<TD>Category convertible to <A HREF="../guide/traits.html#category_tags"><CODE>device_tag</CODE></A></TD>
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Attempts to send all buffered characters downstream, returning <CODE>true</CODE> unless an error occurs.<A CLASS='footnote_ref' NAME='note_1_ref' HREF='#note_1'><SUP>[1]</SUP></A>
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<PRE CLASS="plain_code"><CODE><A HREF="../functions/flush.html#flush_filter">boost::iostreams::flush</A>(f, d)</CODE></PRE>
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<TD><CODE>bool</CODE></TD>
<TD>Category convertible to <A HREF="../guide/traits.html#category_tags"><CODE>filter_tag</CODE></A></TD>
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Attempts to write all buffered characters to d, returning <CODE>true</CODE> if all buffered characters were written.
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<H2>Exceptions</H2>
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Errors which occur during the execution of <A CLASS="code" HREF="../functions/flush.html"><CODE>flush</CODE></A> are be indicated by throwing exceptions. Such exceptions are caught and ignored if they occur during the execution of stream or stream buffer destructor.
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<H2>Models</H2>
<P>Several of the Filters and Devices provided by the Iostreams library are Flushable, but this is an implementation detail.</P>
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<A CLASS='footnote_ref' NAME='note_1' HREF='#note_1_ref'><SUP>[1]</SUP></A>It was noticed late in developement that to be consistent with the policy of reporting errors using exceptions (<I>see</I> <A HREF='../guide/exceptions.html'>Exceptions</A>), <CODE>flush</CODE> should have been specified to return <CODE>void</CODE> when invoked on a Device. Until the specification is changed, Devices should always return <CODE>true</CODE> when flushed.
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<P CLASS="copyright">Revised 02 Feb 2008</P>
<P CLASS="copyright">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>© Copyright 2004-2007 <a href="http://www.coderage.com/turkanis/" target="_top">Jonathan Turkanis</a></P>
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Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)
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