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| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_typetraits.examples.copy"></a><a class="link" href="copy.html" title="An Optimized Version of std::copy"> An Optimized Version |
| of std::copy</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">copy</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">memcpy</span></code> |
| to optimise the copy operation (see <a href="../../../../examples/copy_example.cpp" target="_top">copy_example.cpp</a>): |
| </p> |
| <pre class="programlisting"><span class="comment">// |
| </span><span class="comment">// opt::copy |
| </span><span class="comment">// same semantics as std::copy |
| </span><span class="comment">// calls memcpy 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">I1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">I2</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">b</span><span class="special">></span> |
| <span class="identifier">I2</span> <span class="identifier">copy_imp</span><span class="special">(</span><span class="identifier">I1</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">I1</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">I2</span> <span class="identifier">out</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">out</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">first</span><span class="special">;</span> |
| <span class="special">++</span><span class="identifier">out</span><span class="special">;</span> |
| <span class="special">++</span><span class="identifier">first</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">return</span> <span class="identifier">out</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="identifier">T</span><span class="special">*</span> <span class="identifier">copy_imp</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">first</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">out</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">memmove</span><span class="special">(</span><span class="identifier">out</span><span class="special">,</span> <span class="identifier">first</span><span class="special">,</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="keyword">sizeof</span><span class="special">(</span><span class="identifier">T</span><span class="special">));</span> |
| <span class="keyword">return</span> <span class="identifier">out</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">typename</span> <span class="identifier">I1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">I2</span><span class="special">></span> |
| <span class="keyword">inline</span> <span class="identifier">I2</span> <span class="identifier">copy</span><span class="special">(</span><span class="identifier">I1</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">I1</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">I2</span> <span class="identifier">out</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">// |
| </span> <span class="comment">// We can copy with memcpy if T has a trivial assignment operator, |
| </span> <span class="comment">// and if the iterator arguments are actually pointers (this last |
| </span> <span class="comment">// requirement we detect with overload resolution): |
| </span> <span class="comment">// |
| </span> <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">iterator_traits</span><span class="special"><</span><span class="identifier">I1</span><span class="special">>::</span><span class="identifier">value_type</span> <span class="identifier">value_type</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="identifier">detail</span><span class="special">::</span><span class="identifier">copy_imp</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">out</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">value_type</span><span class="special">>());</span> |
| <span class="special">}</span> |
| </pre> |
| </div> |
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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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