1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>bitmap_pos_to_ord</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="The Linux Kernel API"><link rel="up" href="kernel-lib.html#idp1123213284" title="Bitmap Operations"><link rel="prev" href="API---bitmap-parselist.html" title="__bitmap_parselist"><link rel="next" href="API-bitmap-ord-to-pos.html" title="bitmap_ord_to_pos"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span class="phrase">bitmap_pos_to_ord</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API---bitmap-parselist.html">Prev</a>&#160;</td><th width="60%" align="center">Bitmap Operations</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-bitmap-ord-to-pos.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-bitmap-pos-to-ord"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>bitmap_pos_to_ord &#8212; 
2     find ordinal of set bit at given position in bitmap
3 </p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">bitmap_pos_to_ord </b>(</code></td><td>const unsigned long * <var class="pdparam">buf</var>, </td></tr><tr><td>&#160;</td><td>unsigned int <var class="pdparam">pos</var>, </td></tr><tr><td>&#160;</td><td>unsigned int <var class="pdparam">nbits</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1123457780"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>buf</code></em></span></dt><dd><p>
4     pointer to a bitmap
5    </p></dd><dt><span class="term"><em class="parameter"><code>pos</code></em></span></dt><dd><p>
6     a bit position in <em class="parameter"><code>buf</code></em> (0 &lt;= <em class="parameter"><code>pos</code></em> &lt; <em class="parameter"><code>nbits</code></em>)
7    </p></dd><dt><span class="term"><em class="parameter"><code>nbits</code></em></span></dt><dd><p>
8     number of valid bit positions in <em class="parameter"><code>buf</code></em>
9    </p></dd></dl></div></div><div class="refsect1"><a name="idp1123462788"></a><h2>Description</h2><p>
10   Map the bit at position <em class="parameter"><code>pos</code></em> in <em class="parameter"><code>buf</code></em> (of length <em class="parameter"><code>nbits</code></em>) to the
11   ordinal of which set bit it is.  If it is not set or if <em class="parameter"><code>pos</code></em>
12   is not a valid bit position, map to -1.
13   </p><p>
14
15   If for example, just bits 4 through 7 are set in <em class="parameter"><code>buf</code></em>, then <em class="parameter"><code>pos</code></em>
16   values 4 through 7 will get mapped to 0 through 3, respectively,
17   and other <em class="parameter"><code>pos</code></em> values will get mapped to -1.  When <em class="parameter"><code>pos</code></em> value 7
18   gets mapped to (returns) <em class="parameter"><code>ord</code></em> value 3 in this example, that means
19   that bit 7 is the 3rd (starting with 0th) set bit in <em class="parameter"><code>buf</code></em>.
20   </p><p>
21
22   The bit positions 0 through <em class="parameter"><code>bits</code></em> are valid positions in <em class="parameter"><code>buf</code></em>.
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