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

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
   2 <HTML>
   3 <HEAD>
   4     <TITLE>Peekable</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">Peekable</H1>
  13     <HR CLASS="banner">
  14
  15 <!-- End Banner -->
  16
  17 <H2>Description</H2>
  18
  19 <P>
  20     A Peekable <A HREF="device.html">Device</A> allows a character read from the input sequence to be putback.
  21 </P>
  22
  23 <P>
  24     The name of the concept is based on the observation that a PeekableDevice allow the user to peek at the first character in the sequence it controls by calling <A HREF="../functions/get.html"><CODE>get</CODE></A> or <A HREF="../functions/read.html"><CODE>read</CODE></A> followed by <A HREF="../functions/putback.html"><CODE>putback</CODE></A>. The names Putbackable and InputRevertable were considered but rejected.
  25 </P>
  26
  27 <H2>Refinement of</H2>
  28
  29 <A HREF="source.html">Source</A>.
  30
  31 <A NAME="types"></A>
  32 <H2>Associated Types</H2>
  33
  34 Same as <A HREF="source.html">Source</A>.
  35
  36 <H2>Notation</H2>
  37
  38 <TABLE CELLPADDING="2">
  39     <TR><TD><CODE>P</CODE></TD><TD>-</TD><TD>A type which is a model of Peekable</TD></TR>
  40     <TR><TD><CODE>p</CODE></TD><TD>-</TD><TD>Object of type <CODE>P</CODE></TD></TR>
  41     <TR><TD><CODE>c</CODE></TD><TD>-</TD><TD>Object of type equal to the character type of <CODE>P</CODE></TD></TR>
  42     <TR><TD><CODE>io</CODE></TD><TD>-</TD><TD>Alias for namespace <CODE>boost::iostreams</CODE></TD></TR>
  43 </TABLE>
  44
  45 <H2>Valid Expressions / Semantics</H2>
  46
  47 <TABLE CELLPADDING="5" BORDER="1">
  48     <TR><TH>Expression</TH><TH>Expression Type</TH><TH>Precondition</TH><TH>Semantics</TH><TH>Postcondition</TH></TR>
  49     <TR>
  50         <TD>
  51             <PRE CLASS="plain_code"><CODE><A HREF="../functions/putback.html">io::putback</A>(p, c)</CODE></PRE>
  52         </TD>
  53         <TD><CODE>bool</CODE></TD>
  54         <TD>
  55            One or more characters has been read from <CODE>p</CODE> using <A HREF="../functions/get.html"><CODE>io::get</CODE></A> or <A HREF="../functions/read.html"><CODE>io::read</CODE></A>, with no intervening i/o operations having been performed
  56         </TD>
  57         <TD>
  58             Attempts to put back <CODE>c</CODE> to <CODE>p</CODE>, returning <CODE>true</CODE> for success
  59         </TD>
  60         <TD>
  61             If putback returns <CODE>true</CODE>, the next character read from <CODE>p</CODE> using <A HREF="../functions/get.html"><CODE>io::get</CODE></A> or <A HREF="../functions/read.html"><CODE>io::read</CODE></A> will be equal to <CODE>c</CODE></A>
  62         </TD>
  63     </TR>
  64 </TABLE>
  65
  66 <H2>Exceptions</H2>
  67
  68 <P>
  69     Errors which occur during the execution of <A CLASS="code" HREF="../functions/putback.html"><CODE>putback</CODE></A> are be indicated by throwing exceptions.
  70 </P>
  71
  72 <H2>Models</H2>
  73 <UL>
  74     <LI>Standard input streams and stream buffers.
  75 </UL>
  76
  77 <!-- Begin Footer -->
  78
  79 <HR>
  80
  81 <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>
  82 <P CLASS="copyright">
  83     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>)
  84 </P>
  85
  86 <!-- End Footer -->
  87
  88 </BODY>