1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Chapter 8. Boost.Circular Buffer</title> 6<link rel="stylesheet" href="../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="libraries.html" title="Part I. The Boost C++ Libraries (BoostBook Subset)"> 10<link rel="prev" href="chrono/appendices.html" title="Appendices"> 11<link rel="next" href="circular_buffer/example.html" title="Circular_buffer example"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../boost.png"></td> 16<td align="center"><a href="../../index.html">Home</a></td> 17<td align="center"><a href="../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="chrono/appendices.html"><img src="../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="libraries.html"><img src="../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="circular_buffer/example.html"><img src="../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="chapter"> 27<div class="titlepage"><div> 28<div><h2 class="title"> 29<a name="circular_buffer"></a>Chapter 8. Boost.Circular Buffer</h2></div> 30<div><div class="authorgroup"><div class="author"><h3 class="author"> 31<span class="firstname">Jan</span> <span class="surname">Gaspar</span> 32</h3></div></div></div> 33<div><p class="copyright">Copyright © 2003-2013 Jan Gaspar</p></div> 34<div><div class="legalnotice"> 35<a name="circular_buffer.legal"></a><p> 36 Distributed under the Boost Software License, Version 1.0. (See accompanying 37 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 38 </p> 39</div></div> 40</div></div> 41<div class="toc"> 42<p><b>Table of Contents</b></p> 43<dl class="toc"> 44<dt><span class="section"><a href="circular_buffer.html#circular_buffer.intro">Introduction</a></span></dt> 45<dt><span class="section"><a href="circular_buffer/example.html">Circular_buffer example</a></span></dt> 46<dt><span class="section"><a href="circular_buffer/rationale.html">Rationale</a></span></dt> 47<dt><span class="section"><a href="circular_buffer/implementation.html">Implementation </a></span></dt> 48<dt><span class="section"><a href="circular_buffer/examples.html">More Examples</a></span></dt> 49<dt><span class="section"><a href="circular_buffer/headers.html">Header Files</a></span></dt> 50<dt><span class="section"><a href="circular_buffer/concepts.html">Modelled Concepts</a></span></dt> 51<dt><span class="section"><a href="circular_buffer/template_params.html">Template Parameters</a></span></dt> 52<dt><span class="section"><a href="circular_buffer/tickets.html">Trac Tickets</a></span></dt> 53<dt><span class="section"><a href="circular_buffer/release.html">Release Notes</a></span></dt> 54<dt><span class="section"><a href="circular_buffer/acknowledgements.html">Acknowledgements</a></span></dt> 55<dt><span class="section"><a href="circular_buffer/version_id.html">Documentation Version Info</a></span></dt> 56<dt><span class="section"><a href="boost_circular_buffer_c___reference.html">Boost.Circular_buffer C++ Reference</a></span></dt> 57<dd><dl> 58<dt><span class="section"><a href="boost_circular_buffer_c___reference.html#header.boost.circular_buffer_hpp">Header <boost/circular_buffer.hpp></a></span></dt> 59<dt><span class="section"><a href="boost_circular_buffer_c___reference.html#header.boost.circular_buffer.base_hpp">Header <boost/circular_buffer/base.hpp></a></span></dt> 60<dt><span class="section"><a href="boost_circular_buffer_c___reference.html#header.boost.circular_buffer.space_optimized_hpp">Header <boost/circular_buffer/space_optimized.hpp></a></span></dt> 61</dl></dd> 62<dt><span class="section"><a href="circular_buffer/s14.html">Index</a></span></dt> 63</dl> 64</div> 65<div class="note"><table border="0" summary="Note"> 66<tr> 67<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../doc/src/images/note.png"></td> 68<th align="left">Note</th> 69</tr> 70<tr><td align="left" valign="top"><p> 71 A printer-friendly PDF version of this manual is also available. 72 </p></td></tr> 73</table></div> 74<div class="section"> 75<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 76<a name="circular_buffer.intro"></a><a class="link" href="circular_buffer.html#circular_buffer.intro" title="Introduction">Introduction</a> 77</h2></div></div></div> 78<p> 79 A Circular Buffer. 80 </p> 81<h3> 82<a name="circular_buffer.intro.h0"></a> 83 <span class="phrase"><a name="circular_buffer.intro.description"></a></span><a class="link" href="circular_buffer.html#circular_buffer.intro.description">Description</a> 84 </h3> 85<p> 86 The term <a href="http://en.wikipedia.org/wiki/Circular_buffer" target="_top">circular 87 buffer</a> (also called a <span class="emphasis"><em>ring</em></span> or <span class="emphasis"><em>cyclic 88 buffer</em></span>) refers to an area in memory which is used to store incoming 89 data. When the buffer is filled, new data is written starting at the beginning 90 of the buffer and overwriting the old. 91 </p> 92<p> 93 <code class="computeroutput"><a class="link" href="boost/circular_buffer.html" title="Class template circular_buffer">boost::circular_buffer</a></code> 94 is a STL compliant container. 95 </p> 96<p> 97 It is a kind of sequence similar to <a href="https://www.boost.org/sgi/stl/List.html" target="_top">std::list</a> 98 or <a href="https://www.boost.org/sgi/stl/Deque.html" target="_top">std::deque</a>. 99 It supports random access iterators, constant time insert and erase operations 100 at the beginning or the end of the buffer and interoperability with std algorithms. 101 </p> 102<p> 103 The <code class="computeroutput"><a class="link" href="boost/circular_buffer.html" title="Class template circular_buffer">circular_buffer</a></code> is 104 especially designed to provide <span class="bold"><strong>fixed capacity</strong></span> 105 storage. When its capacity is exhausted, newly inserted elements will cause 106 elements to be overwritten, either at the beginning or end of the buffer (depending 107 on what insert operation is used). 108 </p> 109<p> 110 The <code class="computeroutput"><a class="link" href="boost/circular_buffer.html" title="Class template circular_buffer">circular_buffer</a></code> only 111 allocates memory when created, when the capacity is adjusted explicitly, or 112 as necessary to accommodate resizing or assign operations. 113 </p> 114<p> 115 <span class="inlinemediaobject"><img src="../../libs/circular_buffer/doc/images/circular_buffer.png"></span> 116 </p> 117<p> 118 There is also a <code class="computeroutput"><a class="link" href="boost/circular_idm45227212366288.html" title="Class template circular_buffer_space_optimized">circular_buffer_space_optimized</a></code> 119 version available. 120 </p> 121<p> 122 <span class="inlinemediaobject"><img src="../../libs/circular_buffer/doc/images/space_optimized.png"></span> 123 </p> 124<p> 125 <code class="computeroutput"><a class="link" href="boost/circular_idm45227212366288.html" title="Class template circular_buffer_space_optimized">circular_buffer_space_optimized</a></code> 126 is an adaptation of the <code class="computeroutput"><a class="link" href="boost/circular_buffer.html" title="Class template circular_buffer">circular_buffer</a></code> 127 which <span class="bold"><strong>does not allocate memory all at once when created</strong></span>, 128 instead it allocates memory as needed. 129 </p> 130<p> 131 The predictive memory allocation is similar to typical <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span></code> 132 implementation. Memory is automatically freed as the size of the container 133 decreases. 134 </p> 135<p> 136 The memory allocation process of the space-optimized circular buffer. The 137 <code class="computeroutput">min_capacity</code> 138 of the capacity controller represents the minimal guaranteed amount of allocated 139 memory. The allocated memory will never drop under this value. The default 140 value of the <code class="computeroutput"><span class="identifier">min_capacity</span></code> is 141 set to 0. The <code class="computeroutput"><span class="identifier">min_capacity</span></code> 142 can be set using the constructor parameter <code class="computeroutput">() 143 capacity_control </code> or the function <code class="computeroutput"><span class="identifier">set_capacity</span></code>. 144 </p> 145<p> 146 The space-optimized version is, of course, a little slower. 147 </p> 148</div> 149</div> 150<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 151<td align="left"><p><small>Last revised: August 11, 2020 at 15:03:47 GMT</small></p></td> 152<td align="right"><div class="copyright-footer"></div></td> 153</tr></table> 154<hr> 155<div class="spirit-nav"> 156<a accesskey="p" href="chrono/appendices.html"><img src="../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="libraries.html"><img src="../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="circular_buffer/example.html"><img src="../../doc/src/images/next.png" alt="Next"></a> 157</div> 158</body> 159</html> 160
