ceph/src/boost/libs/iostreams/doc/concepts/flushable.html

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  12     <H1 CLASS="title">Flushable</H1>
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  16
  17 <H2>Description</H2>
  18
  19 <P>
  20     A Flushable Sink or OutputFilter provides a means for the user to request that all buffered characters be sent downstream.
  21 </P>
  22
  23 <H2>Refinement of</H2>
  24
  25 <A NAME="types"></A>
  26 <H2>Associated Types</H2>
  27
  28 <P>Same as <A HREF="filter.html#types">Filter</A> or <A HREF="device.html#types">Device</A>, with the following additional requirement:</P>
  29
  30 <TABLE CELLPADDING="5" BORDER="1">
  31     <TR><TD>Category</TD><TD>A type convertible to <A HREF="../guide/traits.html#category_tags"><CODE>flushable_tag</CODE></A></TD></TR>
  32 </TABLE>
  33
  34
  35 <H2>Notation</H2>
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  37 <TABLE CELLPADDING="2">
  38     <TR><TD><CODE>F</CODE></TD><TD>-</TD><TD>A type which is a model of Flushable</TD></TR>
  39     <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>
  40     <TR><TD><CODE>f</CODE></TD><TD>-</TD><TD>Object of type <CODE>F</CODE></TD></TR>
  41     <TR><TD><CODE>d</CODE></TD><TD>-</TD><TD>Object of type <CODE>D</CODE></TD></TR>
  42 </TABLE>
  43
  44 <H2>Valid Expressions / Semantics</H2>
  45
  46 <TABLE CELLPADDING="5" BORDER="1">
  47     <TR><TH>Expression</TH><TH>Expression Type</TH><TH>Precondition</TH><TH>Semantics</TH></TR>
  48     <TR>
  49         <TD>
  50             <PRE CLASS="plain_code"><CODE><A HREF="../functions/flush.html#flush_device">boost::iostreams::flush</A>(f)</CODE></PRE>
  51         </TD>
  52         <TD><CODE>bool</CODE></TD>
  53         <TD>Category convertible to <A HREF="../guide/traits.html#category_tags"><CODE>device_tag</CODE></A></TD>
  54         <TD>
  55             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>
  56         </TD>
  57     </TR>
  58     <TR>
  59         <TD>
  60             <PRE CLASS="plain_code"><CODE><A HREF="../functions/flush.html#flush_filter">boost::iostreams::flush</A>(f, d)</CODE></PRE>
  61         </TD>
  62         <TD><CODE>bool</CODE></TD>
  63         <TD>Category convertible to <A HREF="../guide/traits.html#category_tags"><CODE>filter_tag</CODE></A></TD>
  64         <TD>
  65             <P>
  66                 Attempts to write all buffered characters to d, returning <CODE>true</CODE> if all buffered characters were written.
  67             </P>
  68         </TD>
  69     </TR>
  70 </TABLE>
  71
  72 <H2>Exceptions</H2>
  73
  74 <P>
  75     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.
  76 </P>
  77
  78 <H2>Models</H2>
  79
  80 <P>Several of the Filters and Devices provided by the Iostreams library are Flushable, but this is an implementation detail.</P>
  81
  82 <HR>
  83
  84 <P>
  85     <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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  92 <P CLASS="copyright">&copy; Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>&copy; Copyright 2004-2007 <a href="http://www.coderage.com/turkanis/" target="_top">Jonathan Turkanis</a></P>
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  94     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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