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PO_Expand versus new versus GNU
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copied!<p>Recently, I made a new friend. His name is <a href="http://msdn.microsoft.com/en-us/library/wfzt8b7y.aspx" rel="nofollow">_expand</a>, and we've had some nice conversations, and I've even hung out with him a few times. But when I started asking around, no one had ever heard of my _expand. I became suspicious. I called a few thoroughly non-metaphorical friends at microsoft, and a few friends elsewhere in the business. Nothing. No one had ever used it. I noodled around various search engines and source trees. Nothing except a cursory mention here and there. Certainly not enough information on performance and compatibility for me to introduce _expand into production code or more pertinently, generic libraries. </p> <p>Worse, there's no equivalent function that I can find in any of the gnu libraries, so anything I hack up with my new friend isn't going to be portable in the least. Which is a shame, because it's really a fascinating and exciting capacity to have. Certainly, I could dig down into realloc, and pull apart how it functions, but the problem there is that much of the implementation is highly variable on *nixes. So I'd have to code version after version to try and get a portable _expand. Still, it seems ridiculous that nothing similar exists in the glib or the expanded gnu libs. </p> <ol> <li>Is there a similar function that I should know about for linux hacking? <strong>Mostly Answered</strong></li> <li>Is there a standard hook that I could build a similar function on? <strong>Answered</strong></li> <li>Does anyone know what kind of performance _expand offers? </li> <li>How does it interact with objects allocated on the LFH?</li> </ol> <p>To clarify my interests, I'm trying to build a singly-linked accumulator that expands in an attempt to minimize fragmentation while allocating multiple-element blocks along the lines of the traditional deque implementation. By constraining the use-cases for element addition and deletion, I'm hoping to optimize time-to-delete for the whole structure, as well as element insertion and indexing. As a result, the "loud failure" of _expand lets me make the structure think intelligently about when and if it can resize inplace, and what that means about where it can put data.</p>

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