blob: 7f76603b1fc499418d3a61994c009dae16f21c91 [file] [log] [blame]
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<!-- This is broken by doc revisioning.
-->
<link rel="shortcut icon" href="../../../../img/favicon.ico">
<title>os_mbuf_off - Apache Mynewt</title>
<link href="../../../../css/bootstrap-3.0.3.min.css" rel="stylesheet">
<link rel="stylesheet" href="../../../../css/highlight.css">
<link href="../../../../css/base.css" rel="stylesheet">
<link href="../../../../css/custom.css" rel="stylesheet">
<link href="../../../../css/v2.css" rel="stylesheet">
<link href="https://fonts.googleapis.com/css?family=Lato" rel="stylesheet">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">
<!-- HTML5 shim and Respond.js IE8 support of HTML5 elements and media queries -->
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
<script src="https://oss.maxcdn.com/libs/respond.js/1.3.0/respond.min.js"></script>
<![endif]-->
<script>
(function(i, s, o, g, r, a, m) {
i["GoogleAnalyticsObject"] = r;
(i[r] =
i[r] ||
function() {
(i[r].q = i[r].q || []).push(arguments);
}),
(i[r].l = 1 * new Date());
(a = s.createElement(o)), (m = s.getElementsByTagName(o)[0]);
a.async = 1;
a.src = g;
m.parentNode.insertBefore(a, m);
})(window, document, "script", "//www.google-analytics.com/analytics.js", "ga");
ga("create", "UA-72162311-1", "auto");
ga("send", "pageview");
</script>
</head>
<body class="os_mbuf_off">
<div class="container">
<div class="row v2-main-banner">
<a class="logo-cell" href="/">
<img class="logo" src="/img/logo.png">
</a>
<div class="tagline-cell">
<h4 class="tagline">An OS to build, deploy and securely manage billions of devices</h4>
</div>
<div class="news-cell">
<div class="well">
<h4>Latest News:</h4> <a href="/download">Apache Mynewt 1.12.0, Apache NimBLE 1.7.0 </a> released (April 4, 2024)
</div>
</div>
</div>
</div>
<nav id="navbar" class="navbar navbar-inverse affix-top" data-spy="affix" data-offset-top="150" role="navigation">
<div class="container">
<!-- Collapsed navigation -->
<div class="navbar-header">
<!-- Expander button -->
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
</div>
<!-- Expanded navigation -->
<div class="navbar-collapse collapse">
<!-- Main navigation -->
<ul class="nav navbar-nav navbar-right">
<li
class=""
>
<a href="/"><i class="fa fa-home" style="font-size: larger;"></i></a>
</li>
<li
class="important"
>
<a href="/quick-start/">Quick Start</a>
</li>
<li
class=""
>
<a href="/about/">About</a>
</li>
<li
class=""
>
<a href="/talks/">Talks</a>
</li>
<li
class="active"
>
<a href="/documentation/">Documentation</a>
</li>
<li
class=""
>
<a href="/download/">Download</a>
</li>
<li
class=""
>
<a href="/community/">Community</a>
</li>
<li
class=""
>
<a href="/events/">Events</a>
</li>
</ul>
</div>
</div>
</nav>
<div class="container">
<div class="row">
<div class="col-md-3 v2-sidebar sidebar-container"><div id="docSidebar" class="hidden-print" role="complementary">
<div class="top">
<div role="search">
<form id="rtd-search-form" class="wy-form" action="../../../../search.html" method="get">
<div class="form-group">
<input type="text" name="q" class="form-control" placeholder="Search documentation" />
</div>
</form>
</div>
</div>
<ul class="toc-nav">
<li class="doc-version"><select class="form-control" onchange="if (this.value) window.location.href=this.value">
<option value="/latest">
Version: master
</option>
<option value="/v1_12_0/" >
Version: 1.12.0
</option>
<option value="/v1_11_0/" >
Version: 1.11.0
</option>
<option value="/v1_10_0/" >
Version: 1.10.0
</option>
<option value="/v1_9_0/" >
Version: 1.9.0
</option>
<option value="/v1_8_0/" >
Version: 1.8.0
</option>
<option value="/v1_7_0/" >
Version: 1.7.0
</option>
<option value="/v1_6_0/" >
Version: 1.6.0
</option>
<option value="/v1_5_0/" >
Version: 1.5.0
</option>
<option value="/v1_4_0/" >
Version: 1.4.0
</option>
<option value="/v1_3_0/os/introduction" >
Version: 1.3.0
</option>
<option value="/v1_2_0/os/introduction" >
Version: 1.2.0
</option>
<option value="/v1_1_0/os/introduction" >
Version: 1.1.0
</option>
<option value="/v1_0_0/os/introduction" selected="selected" >
Version: 1.0.0
</option>
<option value="/v0_9_0/os/introduction" >
Version: 0.9.0
</option>
</select></li>
<li ><a href="../../../introduction/">Mynewt Documentation</a>
<ul>
<li ><a href="../../../get_started/get_started/">Basic Setup</a>
</li>
<li >
<a href="../../../get_started/vocabulary/">Concepts</a>
</li>
<li ><a href="../../../tutorials/tutorials/">Tutorials</a>
</li>
<li ><a href="../../../os_user_guide/">OS User Guide</a>
<ul>
<li ><a href="../../mynewt_os/">OS Core</a>
<ul>
<li><a href="
../../os_started/
">Functions</a>
</li>
<li ><a href="../../context_switch/context_switch/">Scheduler</a>
</li>
<li ><a href="../../cputime/os_cputime/">CPU Time</a>
</li>
<li ><a href="../../time/os_time/">OS Time</a>
</li>
<li ><a href="../../task/task/">Tasks</a>
</li>
<li ><a href="../../event_queue/event_queue/">Event Queues</a>
</li>
<li ><a href="../../semaphore/semaphore/">Semaphores</a>
</li>
<li ><a href="../../mutex/mutex/">Mutexes</a>
</li>
<li ><a href="../../memory_pool/memory_pool/">Memory Pools</a>
</li>
<li ><a href="../../heap/heap/">Heap</a>
</li>
<li><a href="
../mbuf/
">Memory Buffers</a>
<ul>
<li ><a href="../mbuf/">Mbuf</a>
<ul>
<li><a href="
../OS_MBUF_PKTHDR/
">Functions/Macros</a>
<ul>
<li >
<a href="../OS_MBUF_PKTHDR/">OS_MBUF_PKTHDR</a>
</li>
<li >
<a href="../OS_MBUF_PKTHDR_TO_MBUF/">OS_MBUF_PKTHDR_TO_MBUF</a>
</li>
<li >
<a href="../OS_MBUF_PKTLEN/">OS_MBUF_PKTLEN</a>
</li>
<li >
<a href="../OS_MBUF_DATA/">OS_MBUF_DATA</a>
</li>
<li >
<a href="../OS_MBUF_USRHDR/">OS_MBUF_USRHDR</a>
</li>
<li >
<a href="../OS_MBUF_USRHDR_LEN/">OS_MBUF_USRHDR_LEN</a>
</li>
<li >
<a href="../OS_MBUF_LEADINGSPACE/">OS_MBUF_LEADINGSPACE</a>
</li>
<li >
<a href="../OS_MBUF_TRAILINGSPACE/">OS_MBUF_TRAILINGSPACE</a>
</li>
<li >
<a href="../os_mbuf_adj/">os_mbuf_adj</a>
</li>
<li >
<a href="../os_mbuf_append/">os_mbuf_append</a>
</li>
<li >
<a href="../os_mbuf_concat/">os_mbuf_concat</a>
</li>
<li >
<a href="../os_mbuf_copydata/">os_mbuf_copydata</a>
</li>
<li >
<a href="../os_mbuf_copyinto/">os_mbuf_copyinto</a>
</li>
<li >
<a href="../os_mbuf_dup/">os_mbuf_dup</a>
</li>
<li >
<a href="../os_mbuf_extend/">os_mbuf_extend</a>
</li>
<li >
<a href="../os_mbuf_free_chain/">os_mbuf_free_chain</a>
</li>
<li >
<a href="../os_mbuf_get/">os_mbuf_get</a>
</li>
<li >
<a href="../os_mbuf_get_pkthdr/">os_mbuf_get_pkthdr</a>
</li>
<li >
<a href="../os_mbuf_memcmp/">os_mbuf_memcmp</a>
</li>
<li class="active">
<a href="./">os_mbuf_off</a>
</li>
<li >
<a href="../os_mbuf_pool_init/">os_mbuf_pool_init</a>
</li>
<li >
<a href="../os_mbuf_prepend/">os_mbuf_prepend</a>
</li>
<li >
<a href="../os_mbuf_pullup/">os_mbuf_pullup</a>
</li>
</ul>
</li>
</ul>
</li>
<li ><a href="../../msys/msys/">Msys</a>
</li>
<li ><a href="../../mqueue/mqueue/">MQueue</a>
</li>
</ul>
</li>
<li ><a href="../../sanity/sanity/">Sanity</a>
</li>
<li ><a href="../../callout/callout/">Callouts</a>
</li>
</ul>
</li>
<li ><a href="../../porting/port_os/">Porting to your Platform</a>
</li>
<li ><a href="../../../modules/console/console/">Console</a>
</li>
<li ><a href="../../../modules/shell/shell/">Shell</a>
</li>
<li ><a href="../../../modules/split/split/">Split Images</a>
</li>
<li ><a href="../../../modules/bootloader/bootloader/">Bootloader</a>
</li>
<li><a href="
../../../modules/fs/fs/fs/
">File System</a>
</li>
<li ><a href="../../../modules/hal/hal/">Hardware Abstraction Layer</a>
</li>
<li ><a href="../../../modules/drivers/driver/">Drivers</a>
</li>
<li ><a href="../../../modules/testutil/testutil/">Test Utilities</a>
</li>
<li ><a href="../../../modules/devmgmt/newtmgr/">Device Management with Newt Manager</a>
</li>
<li ><a href="../../../modules/imgmgr/imgmgr/">Image Manager</a>
</li>
<li >
<a href="../../../modules/baselibc/">Baselibc library</a>
</li>
<li ><a href="../../../modules/json/json/">JSON</a>
</li>
<li ><a href="../../../modules/fcb/fcb/">Flash Circular Buffer</a>
</li>
<li ><a href="../../../modules/stats/stats/">Stats</a>
</li>
<li ><a href="../../../modules/logs/logs/">Logs</a>
</li>
<li ><a href="../../../modules/sysinitconfig/sysinitconfig/">System Configuration And Initialization</a>
</li>
</ul>
</li>
<li><a href="
../../../../network/ble/ble_intro/
">BLE User Guide</a>
</li>
<li ><a href="../../../../newt/newt_intro/">Newt Tool Guide</a>
</li>
<li ><a href="../../../../newtmgr/overview/">Newt Manager Guide</a>
</li>
<li >
<a href="../../../../known_issues/">Known Issues</a>
</li>
</ul>
</li>
<li><a href="
../../../../faq/go_env/
">Appendix</a>
</li>
</ul>
</div></div>
<div class="col-md-9" role="main">
<div class="doc-header">
<div role="navigation" aria-label="breadcrumbs navigation">
<ul class="wy-breadcrumbs">
<li><a href="/documentation/">Docs</a></li>
<li>&raquo; <a href="os/core_os/mbuf/OS_MBUF_PKTHDR/">Functions/Macros</a></li>
<li>&raquo; <a href="os/core_os/mbuf/mbuf/">Mbuf</a></li>
<li>&raquo; Memory Buffers</li>
<li>&raquo; <a href="os/core_os/mynewt_os/">OS Core</a></li>
<li>&raquo; <a href="os/os_user_guide/">OS User Guide</a></li>
<li>&raquo; <a href="os/introduction/">Mynewt Documentation</a></li>
<li>&raquo; os_mbuf_off</li>
</ul>
</div>
</div>
<div class="alert alert-warning">
<p>
Version 1.0.0 is not the most recent version of the Apache Mynewt
documentation. Click <a href="/latest">here</a> to read the latest
version.
</p>
</div>
<h2 id="os_mbuf_off"><font color="#F2853F" style="font-size:24pt">os_mbuf_off</font></h2>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code><span style="color: #A90D91">struct</span> <span style="color: #3F6E75">os_mbuf</span> <span style="color: #000000">*os_mbuf_off</span>(<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">os_mbuf</span> <span style="color: #000000">*om</span>, <span style="color: #A90D91">int</span> <span style="color: #000000">off</span>, <span style="color: #A90D91">int</span> <span style="color: #000000">*out_off</span>)
</code></pre></div>
<p>Given an offset in the packet (i.e. user data byte offset in the mbuf chain), return the mbuf and the offset in that mbuf where byte 'off' is located. Note that the offset is <em>returned</em> in <code>out_off</code>.</p>
<p><br></p>
<h4 id="arguments">Arguments</h4>
<table>
<thead>
<tr>
<th>Arguments</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>om</code></td>
<td>Pointer to mbuf</td>
</tr>
<tr>
<td><code>off</code></td>
<td>Location in mbuf chain of desired byte offset</td>
</tr>
<tr>
<td><code>out_off</code></td>
<td>Pointer to storage for the relative offset of the absolute location in the returned mbuf</td>
</tr>
</tbody>
</table>
<p><br></p>
<h4 id="returned-values">Returned values</h4>
<p><strong>NULL</strong> if the offset is not within the mbuf chain or <code>om</code> points to <strong>NULL</strong>.</p>
<p><br></p>
<h4 id="notes">Notes</h4>
<p>The user is allowed to call this function with the length of the mbuf chain but no greater. This allows the user to get the mbuf and offset (in that mbuf) where the next user data byte should be written.</p>
<p>While this api is provided to the user, other APIs are expected to be used by the applciation developer (i.e. <code>os_mbuf_append()</code> or <code>os_mbuf_copyinto()</code>).
<br></p>
<h4 id="example">Example</h4>
<div class="codehilite" style="background: #ffffff"><pre style="line-height: 125%;"><span></span><code> <span style="color: #A90D91">int</span> <span style="color: #000000">relative_offset</span>;
<span style="color: #A90D91">uint16_t</span> <span style="color: #000000">pktlen</span>;
<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">os_mbuf</span> <span style="color: #000000">*om</span>;
<span style="color: #A90D91">struct</span> <span style="color: #3F6E75">os_mbuf</span> <span style="color: #000000">*tmp</span>;
<span style="color: #177500">/* Append a new line character to end of mbuf data */</span>
<span style="color: #000000">pktlen</span> <span style="color: #000000">=</span> <span style="color: #000000">OS_MBUF_PKTLEN</span>(<span style="color: #000000">om</span>);
<span style="color: #000000">relative_offset</span> <span style="color: #000000">=</span> <span style="color: #1C01CE">0</span>;
<span style="color: #000000">tmp</span> <span style="color: #000000">=</span> <span style="color: #000000">os_mbuf_off</span>(<span style="color: #000000">om</span>, <span style="color: #000000">pktlen</span>, <span style="color: #000000">&amp;relative_offset</span>);
<span style="color: #A90D91">if</span> (<span style="color: #000000">tmp</span>) {
<span style="color: #177500">/* Offset found. */</span>
<span style="color: #000000">tmp-&gt;om_data</span>[<span style="color: #000000">relative_offset</span>] <span style="color: #000000">=</span> <span style="color: #2300CE">&#39;\n&#39;</span>;
} <span style="color: #A90D91">else</span> {
<span style="color: #177500">/*</span>
<span style="color: #177500"> * This mbuf does not contain enough bytes so this is an invalid offset.</span>
<span style="color: #177500"> * In other words, the mbuf is less than 62 bytes in length.</span>
<span style="color: #177500"> */</span>
}
</code></pre></div>
<div class="row">
<ul class="nav nav-pills" style="margin-bottom: 10px">
<li>
</li>
<li class="pull-right">
</li>
</ul>
</div>
<footer class="row">
<div class="col-xs-12">
<p class="copyright">Apache Mynewt (incubating) is available under Apache License, version 2.0.</p>
</div>
<div class="col-xs-12">
<div class="logos">
<a href="https://www.apache.org/">
<img src="/img/asf_logo_wide_small.png" alt="Apache" title="Apache">
</a>
<p>
Copyright © 2015-2021 The Apache Software Foundation.<br>
<small class="footnote">
Apache Mynewt, Mynewt, Apache, the Apache feather logo, and the Apache Mynewt
project logo are either registered trademarks or trademarks of the Apache
Software Foundation in the United States and other countries.
</small>
</p>
<a href="">
<img src="https://www.countit.com/images/add_to_slack.png" alt="Slack Icon" title="Join our Slack Community" />
</a>
</div>
</div>
<a href="https://www.apache.org/licenses/">
<button class="button-footer-asf">
License
</button>
</a>
<a href="https://www.apache.org/foundation/sponsorship.html">
<button class="button-footer-asf">
Sponsorship
</button>
</a>
<a href="https://www.apache.org/foundation/thanks.html">
<button class="button-footer-asf">
Thanks
</button>
</a>
<a href="https://www.apache.org/security/">
<button class="button-footer-asf">
Security
</button>
</a>
<a href="https://apache.org/events/current-event">
<button class="button-footer-asf">
ASF Events
</button>
</a>
</footer>
</div>
</div>
</div>
<script src="../../../../js/jquery-1.10.2.min.js"></script>
<script src="../../../../js/bootstrap-3.0.3.min.js"></script>
<script src="../../../../js/highlight.pack.js"></script>
<script src="../../../../js/base.js"></script>
<script src="../../../../js/custom.js"></script>
<script src="search/main.js"></script>
</body>
</html>