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    <p>Do you have a <em>really</em> good reason to use a list here at all? At first glance, it looks like a <code>std::vector</code> will be a better choice. You probably also don't want a container of pointers, just a container of objects.</p> <p>You can also do the job quite a bit more neatly a standard algorithm:</p> <pre><code>typedef std::vector&lt;pfx_t&gt; pfx_list_t; int eval_one_pkt(pfx_list_t const &amp;cfg, unsigned int ip_addr) { auto pos = std::find_if(cfg.begin(), cfg.end(), [ip_addr](pfx_t const &amp;p) { return ip_addr &gt;= p.begin &amp;&amp; ip_addr &lt;= p.end; }); if (pos != cfg.end()) { ++(pos-&gt;count); return 1; } return 0; } </code></pre> <p>If I were doing it, however, I'd probably turn that into generic algorithm instead:</p> <pre><code>template &lt;class InIter&gt; int eval_one_pkt(InIter b, InIter e, unsigned int ip_addr) { auto pos = std::find_if(b, e, [ip_addr](pfx_t const &amp;p) { return ip_addr &gt;= p.begin &amp;&amp; ip_addr &lt;= p.end; }); if (pos != cfg.end()) { ++(pos-&gt;count); return 1; } return 0; } </code></pre> <p>Though unrelated to C vs. C++, for a possible slight further optimization on the range check you might want to try something like this:</p> <pre><code>return ((unsigned)(ip_addr-p.begin) &lt;= (p.end-p.begin)); </code></pre> <p>With a modern compiler with optimization enabled, I'd expect the template to be expanded inline entirely at the point of use, so there probably wouldn't be any function calls involved at all.</p>
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    1. POWhy does this C++ function takes 4 time as much as a c function
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    1. COThanks for the answer. list is a better choice because pfx_ts can come and go. I used object pointer because object can be in multiple lists
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    2. CO@helloworld: [list still probably isn't a better choice](http://stackoverflow.com/a/9765090/179910). Fair enough about using a pointer.
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    3. COthanks for the pointer on list vs vectors.yes i agree with your reasoning
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