73 lines
4.2 KiB
HTML
73 lines
4.2 KiB
HTML
<!--
|
|
Licensed to the Apache Software Foundation (ASF) under one or more
|
|
contributor license agreements. See the NOTICE file distributed
|
|
with this work for additional information regarding copyright
|
|
ownership. The ASF licenses this file to you under the Apache
|
|
License, Version 2.0 (the License); you may not use this file
|
|
except in compliance with the License. You may obtain a copy of
|
|
the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
|
|
implied. See the License for the specific language governing
|
|
permissions and limitations under the License.
|
|
|
|
Copyright 1999-2007 Rogue Wave Software, Inc.
|
|
-->
|
|
|
|
<HTML>
|
|
<HEAD>
|
|
<TITLE>An Example</TITLE>
|
|
<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
|
|
<BODY BGCOLOR=#FFFFFF>
|
|
<A HREF="37-1.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="38.html"><IMG SRC="images/bnext.gif" WIDTH=25 HEIGHT=21 ALT="Next file" BORDER=O></A><DIV CLASS="DOCUMENTNAME"><B>Apache C++ Standard Library User's Guide</B></DIV>
|
|
<H2>37.2 An Example</H2>
|
|
<A NAME="idx897"><!></A>
|
|
<A NAME="idx898"><!></A>
|
|
<P>A program can register a callback function on a particular stream as follows:</P>
|
|
|
|
<UL><PRE>
|
|
// Callback function
|
|
void show_event(std::ios_base::event e,
|
|
std::iosbase& io, int index)
|
|
{
|
|
if (e == std::ios_base::imbue_event)
|
|
std::cout << "imbue called" << std::endl;
|
|
else if (e == std::ios_base::erase_event)
|
|
std::cout << "stream destroyed" << std::endl;
|
|
else
|
|
std::cout << "cpyfmt called" << std::endl;
|
|
}
|
|
|
|
|
|
std::ostringstream s;
|
|
s.register_callback(show_event,0); //1
|
|
s.imbue(std::locale::global()); //2
|
|
</PRE></UL>
|
|
<TABLE CELLPADDING="3">
|
|
|
|
<TR VALIGN="top"><TD><SAMP>//1</SAMP></TD><TD>The function <SAMP>show_event</SAMP> is now called with either <SAMP>std::ios_base::erase_event</SAMP>, <SAMP>std::ios_base::imbue_event</SAMP>, or <SAMP>std::ios_base::copyfmt_event</SAMP> as the first argument, depending on whether the destruction of the stream, the imbuing of a new locale, or a call to <SAMP>std::basic_ios<>::copyfmt()</SAMP> initiated the callback.
|
|
<TR VALIGN="top"><TD><SAMP>//2</SAMP></TD><TD>This causes <SAMP>show_event</SAMP> to be called. The first argument is <SAMP>std::ios_base::imbue_event</SAMP>; the second argument is a reference to the stream where the event occurred, which is <SAMP>s</SAMP> in this case; and the third argument is always the index provided in the call to <SAMP>std::ios_base<>::register_callback()</SAMP>, which is <SAMP>0</SAMP> in this case.
|
|
<BR><BR>If more than one function is registered, functions are called in the opposite order of registration.
|
|
</TABLE>
|
|
<P>Please refer to <A HREF="26-9.html#2692">Section 26.9.2</A> for an example using callback functions with a user-defined stream inserter.</P>
|
|
|
|
<BR>
|
|
<HR>
|
|
<A HREF="37-1.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="38.html"><IMG SRC="images/bnext.gif" WIDTH=20 HEIGHT=21 ALT="Next file" BORDER=O></A>
|
|
|
|
<!-- Google Analytics tracking code -->
|
|
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
|
|
</script>
|
|
<script type="text/javascript">
|
|
_uacct = "UA-1775151-1";
|
|
urchinTracker();
|
|
</script>
|
|
<!-- end of Google Analytics tracking code -->
|
|
|
|
</BODY>
|
|
</HTML>
|