<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <HTML> <HEAD> <TITLE>SymmetricFilter</TITLE> <LINK REL="stylesheet" HREF="../../../../boost.css"> <LINK REL="stylesheet" HREF="../theme/iostreams.css"> </HEAD> <BODY> <!-- Begin Banner --> <H1 CLASS="title">SymmetricFilter</H1> <HR CLASS="banner"> <!-- End Banner --> <H2>Description</H2> <P> A SymmetricFilter processes a character sequence fed to it incrementally in a user-supplied buffer and outputs a filtered sequence incrementally to a second user-supplied buffer. It is useful for defining filters based on C language APIs. </P> <P> SymmetricFilter does not refine <A HREF="filter.html">Filter</A>. Instead, the template <A HREF="../classes/symmetric_filter.html"><CODE>symmetric_filter</CODE></A> can used to generate a Filter from a SymmetricFilter. The Filters generated in this manner are <A HREF="dual_use_filter.html">DualUseFilters</A> and are <A HREF="../../../../doc/html/CopyConstructible.html" TARGET="_top">CopyConstructible</A> regardless of whether the SymmetricFilters on which they are based are <A HREF="../../../../doc/html/CopyConstructible.html">CopyConstructible</A>. </P> <P> The concept SymmetricFilter is notable in that its definition does not involve the concept of a <A HREF="source.html">Source</A> or <A HREF="sink.html">Sink</A>. </P> <H2>Associated Types</H2> <TABLE CELLPADDING="5" BORDER="1"> <TR><TD>Character type</TD><TD>The type of the characters in the filtered sequences</TD></TR> </TABLE> <H2>Notation</H2> <TABLE CELLPADDING="2"> <TR><TD><CODE>F</CODE></TD><TD>- A type which is a model of SymmetricFilter</TD></TR> <TR><TD><CODE>Ch</CODE></TD><TD>- The character type of <CODE>F</CODE></TD></TR> <TR><TD><CODE>f</CODE></TD><TD>- Object of type <CODE>F</CODE></TD></TR> <TR><TD><CODE>i1, i2</CODE></TD><TD>- Objects of type <CODE>const Ch*</CODE></TD></TR> <TR><TD><CODE>o1, o2</CODE></TD><TD>- Objects of type <CODE>Ch*</CODE></TD></TR> <TR><TD><CODE>flush</CODE></TD><TD>- Object of type <CODE>bool</CODE></TD></TR> </TABLE> <H2>Valid Expressions / Semantics — Typenames</H2> <TABLE CELLPADDING="5" BORDER="1"> <TR><TH>Expression</TH><TH>Expression Type</TH></TR> <TR> <TD> <PRE CLASS="plain_code"><CODE>typename <A HREF="../guide/traits.html#char_type_of_ref">char_type_of</A><F>::type</CODE></PRE> </TD> <TD><CODE>typename</CODE> of the character type</TD> </TR> </TABLE> <H2>Valid Expressions / Semantics — Member Functions</H2> <TABLE CELLPADDING="5" BORDER="1"> <TR><TH>Expression</TH><TH>Expression Type</TH><TH>Semantics</TH><TH>Postcondition</TH></TR> <TR> <TD><PRE CLASS="plain_code"><CODE>f.filter(i1, i2, o1, o2, flush)</CODE></PRE></TD> <TD><CODE>bool</CODE></TD> <TD> Attempts to filter the sequence <CODE>[i1, i2)</CODE>, storing the result in the sequence <CODE>[o1, o2)</CODE>. If <CODE>flush</CODE> is true, writes as much output to <CODE>[o1, o2)</CODE> as possible. If <CODE>flush</CODE> is <CODE>false</CODE>, returns <CODE>false</CODE> to indicate that a “natural” end of stream has been detected. Otherwise, returns <CODE>true</CODE> to indicate that additional characters, not yet stored in <CODE>[o1, o2)</CODE>, are available for output. </TD> <TD> <P><CODE>i1</CODE> points to the first unconsumed character in the orginal sequence <CODE>[i1, i2)</CODE>. <P><CODE>o1</CODE> points to the first unconsumed character in the orginal sequence <CODE>[o1, o2)</CODE>. <P>Either <CODE>i1 == i2</CODE> or <CODE>o1 == o2</CODE>. </TD> </TR> <TR> <TD><PRE CLASS="plain_code"><CODE>f.close()</CODE></PRE></TD> <TD><CODE>void</CODE></TD> <TD ALIGN="center">-</TD> <TD> <CODE></CODE><CODE>f</CODE> is ready to begin filtering a new sequence </TD> </TR> </TABLE> <H2>Exceptions</H2> <P> Errors which occur during the execution of <CODE>filter</CODE> or <CODE>close</CODE> are indicated by throwing exceptions. </P> <H2>Models</H2> <!-- Begin Footer --> <HR> <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> <P CLASS="copyright"> 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>) </P> <!-- End Footer --> </BODY>