1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2<HTML> 3<HEAD> 4 <TITLE>Flushable</TITLE> 5 <LINK REL="stylesheet" HREF="../../../../boost.css"> 6 <LINK REL="stylesheet" HREF="../theme/iostreams.css"> 7</HEAD> 8<BODY> 9 10<!-- Begin Banner --> 11 12 <H1 CLASS="title">Flushable</H1> 13 <HR CLASS="banner"> 14 15<!-- End Banner --> 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> 36 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. 86</P> 87 88<!-- Begin Footer --> 89 90<HR> 91 92<P CLASS="copyright">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>© Copyright 2004-2007 <a href="https://www.boost.org/users/people/jonathan_turkanis.html" target="_top">Jonathan Turkanis</a></P> 93<P CLASS="copyright"> 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>) 95</P> 96 97<!-- End Footer --> 98 99</BODY>