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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_typetraits.examples.fill"></a><a class="link" href="fill.html" title="An Optimised Version of std::fill"> An Optimised Version
of std::fill</a>
</h3></div></div></div>
<p>
Demonstrates a version of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">fill</span></code>
that uses <code class="computeroutput"><a class="link" href="../reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a></code>
to determine whether to use <code class="computeroutput"><span class="identifier">memset</span></code>
to optimise the fill operation (see <a href="../../../../examples/fill_example.cpp" target="_top">fill_example.cpp</a>):
</p>
<pre class="programlisting"><span class="comment">//
</span><span class="comment">// fill
</span><span class="comment">// same as std::fill, but uses memset where appropriate
</span><span class="comment">//
</span><span class="keyword">namespace</span> <span class="identifier">detail</span><span class="special">{</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">I</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">b</span><span class="special">></span>
<span class="keyword">void</span> <span class="identifier">do_fill</span><span class="special">(</span><span class="identifier">I</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">I</span> <span class="identifier">last</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">val</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">integral_constant</a><span class="special"><</span><span class="keyword">bool</span><span class="special">,</span> <span class="identifier">b</span><span class="special">>&)</span>
<span class="special">{</span>
<span class="keyword">while</span><span class="special">(</span><span class="identifier">first</span> <span class="special">!=</span> <span class="identifier">last</span><span class="special">)</span>
<span class="special">{</span>
<span class="special">*</span><span class="identifier">first</span> <span class="special">=</span> <span class="identifier">val</span><span class="special">;</span>
<span class="special">++</span><span class="identifier">first</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span>
<span class="keyword">void</span> <span class="identifier">do_fill</span><span class="special">(</span><span class="identifier">T</span><span class="special">*</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">last</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">val</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">true_type</a><span class="special">&)</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">memset</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">val</span><span class="special">,</span> <span class="identifier">last</span><span class="special">-</span><span class="identifier">first</span><span class="special">);</span>
<span class="special">}</span>
<span class="special">}</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">I</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
<span class="keyword">inline</span> <span class="keyword">void</span> <span class="identifier">fill</span><span class="special">(</span><span class="identifier">I</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">I</span> <span class="identifier">last</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">val</span><span class="special">)</span>
<span class="special">{</span>
<span class="comment">//
</span> <span class="comment">// We can do an optimised fill if T has a trivial assignment
</span> <span class="comment">// operator and if it's size is one:
</span> <span class="comment">//
</span> <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">integral_constant</a><span class="special"><</span><span class="keyword">bool</span><span class="special">,</span>
<span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span> <span class="special">&&</span> <span class="special">(</span><span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">T</span><span class="special">)</span> <span class="special">==</span> <span class="number">1</span><span class="special">)></span> <span class="identifier">truth_type</span><span class="special">;</span>
<span class="identifier">detail</span><span class="special">::</span><span class="identifier">do_fill</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">val</span><span class="special">,</span> <span class="identifier">truth_type</span><span class="special">());</span>
<span class="special">}</span>
</pre>
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<td align="right"><div class="copyright-footer">Copyright © 2000, 2006 Adobe Systems Inc, David Abrahams,
Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant, Jesse Jones, Mat
Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten Ottosen, Robert
Ramey and Jeremy Siek<p>
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" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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