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25 | <div class="section"> | |
26 | <div class="titlepage"><div><div><h3 class="title"> | |
27 | <a name="boost_typetraits.examples.fill"></a><a class="link" href="fill.html" title="An Optimised Version of std::fill">An Optimised Version | |
28 | of std::fill</a> | |
29 | </h3></div></div></div> | |
30 | <p> | |
31 | Demonstrates a version of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">fill</span></code> | |
32 | that uses <code class="computeroutput"><a class="link" href="../reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a></code> | |
33 | to determine whether to use <code class="computeroutput"><span class="identifier">memset</span></code> | |
34 | to optimise the fill operation (see <a href="../../../../examples/fill_example.cpp" target="_top">fill_example.cpp</a>): | |
35 | </p> | |
36 | <pre class="programlisting"><span class="comment">//</span> | |
37 | <span class="comment">// fill</span> | |
38 | <span class="comment">// same as std::fill, but uses memset where appropriate</span> | |
39 | <span class="comment">//</span> | |
40 | <span class="keyword">namespace</span> <span class="identifier">detail</span><span class="special">{</span> | |
41 | ||
42 | <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> | |
43 | <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> | |
44 | <span class="special">{</span> | |
45 | <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> | |
46 | <span class="special">{</span> | |
47 | <span class="special">*</span><span class="identifier">first</span> <span class="special">=</span> <span class="identifier">val</span><span class="special">;</span> | |
48 | <span class="special">++</span><span class="identifier">first</span><span class="special">;</span> | |
49 | <span class="special">}</span> | |
50 | <span class="special">}</span> | |
51 | ||
52 | <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> | |
53 | <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> | |
54 | <span class="special">{</span> | |
55 | <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> | |
56 | <span class="special">}</span> | |
57 | ||
58 | <span class="special">}</span> | |
59 | ||
60 | <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> | |
61 | <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> | |
62 | <span class="special">{</span> | |
63 | <span class="comment">//</span> | |
64 | <span class="comment">// We can do an optimised fill if T has a trivial assignment </span> | |
65 | <span class="comment">// operator and if it's size is one:</span> | |
66 | <span class="comment">//</span> | |
67 | <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> | |
68 | <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> | |
69 | <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> | |
70 | <span class="special">}</span> | |
71 | </pre> | |
72 | </div> | |
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77 | Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten | |
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79 | Watanabe<p> | |
80 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
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