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<div class="title">llfio_v2_xxx::algorithm Namespace Reference</div> </div>
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<p>Collection of file system based algorithms.
<a href="namespacellfio__v2__xxx_1_1algorithm.html#details">More...</a></p>
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Namespaces</h2></td></tr>
<tr class="memitem:namespacellfio__v2__xxx_1_1algorithm_1_1impl"><td class="memItemLeft" align="right" valign="top">  </td><td class="memItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm_1_1impl.html">impl</a></td></tr>
<tr class="memdesc:namespacellfio__v2__xxx_1_1algorithm_1_1impl"><td class="mdescLeft"> </td><td class="mdescRight">Does not exist in the actual source code, purely here to workaround doxygen limitations. <br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:namespacellfio__v2__xxx_1_1algorithm_1_1shared__fs__mutex"><td class="memItemLeft" align="right" valign="top">  </td><td class="memItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm_1_1shared__fs__mutex.html">shared_fs_mutex</a></td></tr>
<tr class="memdesc:namespacellfio__v2__xxx_1_1algorithm_1_1shared__fs__mutex"><td class="mdescLeft"> </td><td class="mdescRight">Algorithms for protecting a shared filing system resource from racy modification. <br /></td></tr>
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Classes</h2></td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1cached__parent__handle__adapter.html">cached_parent_handle_adapter</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Adapts any <code>construct()</code>-able implementation to cache its parent directory handle in a process wide cache. <a href="classllfio__v2__xxx_1_1algorithm_1_1cached__parent__handle__adapter.html#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1combining__handle__adapter.html">combining_handle_adapter</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A handle combining the data from one or two other handles. <a href="classllfio__v2__xxx_1_1algorithm_1_1combining__handle__adapter.html#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1compare__visitor.html">compare_visitor</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A visitor for the filesystem traversal and comparison algorithm. <a href="structllfio__v2__xxx_1_1algorithm_1_1compare__visitor.html#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1contents__visitor.html">contents_visitor</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A visitor for the filesystem contents algorithm. <a href="structllfio__v2__xxx_1_1algorithm_1_1contents__visitor.html#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1difference__item.html">difference_item</a></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1reduce__visitor.html">reduce_visitor</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A visitor for the filesystem traversal and reduction algorithm. <a href="structllfio__v2__xxx_1_1algorithm_1_1reduce__visitor.html#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1summarize__visitor.html">summarize_visitor</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A visitor for the filesystem traversal and summary algorithm. <a href="structllfio__v2__xxx_1_1algorithm_1_1summarize__visitor.html#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1traversal__summary.html">traversal_summary</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A summary of a directory tree. <a href="structllfio__v2__xxx_1_1algorithm_1_1traversal__summary.html#details">More...</a><br /></td></tr>
<tr class="separator:"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">struct  </td><td class="memItemRight" valign="bottom"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1traverse__visitor.html">traverse_visitor</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">A visitor for the filesystem traversal algorithm. <a href="structllfio__v2__xxx_1_1algorithm_1_1traverse__visitor.html#details">More...</a><br /></td></tr>
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<tr class="memitem:"><td class="memItemLeft" align="right" valign="top">class  </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a></td></tr>
<tr class="memdesc:"><td class="mdescLeft"> </td><td class="mdescRight">Provides a constant time capacity expanding move-only STL vector. Requires <code>T</code> to be trivially copyable. <a href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html#details">More...</a><br /></td></tr>
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Typedefs</h2></td></tr>
<tr class="memitem:a27450e894b5dab6c18a01350670fa0dc"><td class="memTemplParams" colspan="2">template<class Target , class Source > </td></tr>
<tr class="memitem:a27450e894b5dab6c18a01350670fa0dc"><td class="memTemplItemLeft" align="right" valign="top">using </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a27450e894b5dab6c18a01350670fa0dc">xor_handle_adapter</a> = <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1combining__handle__adapter.html">combining_handle_adapter</a>< detail::xor_handle_adapter_op, Target, Source ></td></tr>
<tr class="memdesc:a27450e894b5dab6c18a01350670fa0dc"><td class="mdescLeft"> </td><td class="mdescRight">A handle combining the data from two other handles using XOR. <a href="namespacellfio__v2__xxx_1_1algorithm.html#a27450e894b5dab6c18a01350670fa0dc">More...</a><br /></td></tr>
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Functions</h2></td></tr>
<tr class="memitem:a3c661d6cba0da25fe9e1211ede1fd004"><td class="memItemLeft" align="right" valign="top">result< file_handle::extent_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a3c661d6cba0da25fe9e1211ede1fd004">clone_or_copy</a> (<a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a> &src, const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> &destdir, <a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view</a> destleaf={}, bool preserve_timestamps=true, bool force_copy_now=false, <a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42">file_handle::creation</a> creation=<a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42af7cf95e0f43dc8f79e39ae628c85a11d">file_handle::creation::always_new</a>, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d={}) noexcept</td></tr>
<tr class="memdesc:a3c661d6cba0da25fe9e1211ede1fd004"><td class="mdescLeft"> </td><td class="mdescRight">Clone or copy the extents of the filesystem entity identified by <code>src</code> to <code>destdir</code> optionally renamed to <code>destleaf</code>. <a href="namespacellfio__v2__xxx_1_1algorithm.html#a3c661d6cba0da25fe9e1211ede1fd004">More...</a><br /></td></tr>
<tr class="separator:a3c661d6cba0da25fe9e1211ede1fd004"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:afae251fc3bfb7280b47b6135e2f6c7e2"><td class="memItemLeft" align="right" valign="top">result< <a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1contents__visitor_1_1contents__type.html">contents_visitor::contents_type</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#afae251fc3bfb7280b47b6135e2f6c7e2">contents</a> (const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> &dirh, <a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1contents__visitor.html">contents_visitor</a> *visitor=nullptr, size_t threads=0, bool force_slow_path=false) noexcept</td></tr>
<tr class="memdesc:afae251fc3bfb7280b47b6135e2f6c7e2"><td class="mdescLeft"> </td><td class="mdescRight">Calculate the contents of everything within and under <code>dirh</code>. What is returned is unordered. <a href="namespacellfio__v2__xxx_1_1algorithm.html#afae251fc3bfb7280b47b6135e2f6c7e2">More...</a><br /></td></tr>
<tr class="separator:afae251fc3bfb7280b47b6135e2f6c7e2"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a6165d32704ff21b4aed3046f11b31cb0"><td class="memItemLeft" align="right" valign="top">result< <a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1traversal__summary.html">traversal_summary</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a6165d32704ff21b4aed3046f11b31cb0">summarize</a> (const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> &dirh, stat_t::want want=<a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1traversal__summary.html#a8904eee9435edf3562642294046c634e">traversal_summary::default_metadata</a>(), <a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1summarize__visitor.html">summarize_visitor</a> *visitor=nullptr, size_t threads=0, bool force_slow_path=false) noexcept</td></tr>
<tr class="memdesc:a6165d32704ff21b4aed3046f11b31cb0"><td class="mdescLeft"> </td><td class="mdescRight">Summarise the directory identified <code>dirh</code>, and everything therein. <a href="namespacellfio__v2__xxx_1_1algorithm.html#a6165d32704ff21b4aed3046f11b31cb0">More...</a><br /></td></tr>
<tr class="separator:a6165d32704ff21b4aed3046f11b31cb0"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a05594f7c8ae275fa65b2acd57cc9b8ac"><td class="memItemLeft" align="right" valign="top">result< size_t > </td><td class="memItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a05594f7c8ae275fa65b2acd57cc9b8ac">reduce</a> (<a class="el" href="classllfio__v2__xxx_1_1directory__handle.html">directory_handle</a> &&dirh, <a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1reduce__visitor.html">reduce_visitor</a> *visitor=nullptr, size_t threads=0, bool force_slow_path=false) noexcept</td></tr>
<tr class="memdesc:a05594f7c8ae275fa65b2acd57cc9b8ac"><td class="mdescLeft"> </td><td class="mdescRight">Reduce the directory identified <code>dirh</code>, and everything therein, to the null set. <a href="namespacellfio__v2__xxx_1_1algorithm.html#a05594f7c8ae275fa65b2acd57cc9b8ac">More...</a><br /></td></tr>
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<tr class="memitem:ae068bc16598189811d0ce2b3530f1de7"><td class="memItemLeft" align="right" valign="top">result< size_t > </td><td class="memItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#ae068bc16598189811d0ce2b3530f1de7">traverse</a> (const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> &dirh, <a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1traverse__visitor.html">traverse_visitor</a> *visitor, size_t threads=0, void *data=nullptr, bool force_slow_path=false) noexcept</td></tr>
<tr class="memdesc:ae068bc16598189811d0ce2b3530f1de7"><td class="mdescLeft"> </td><td class="mdescRight">Traverse everything within and under <code>dirh</code>. <a href="namespacellfio__v2__xxx_1_1algorithm.html#ae068bc16598189811d0ce2b3530f1de7">More...</a><br /></td></tr>
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template<class T > </td></tr>
<tr class="memitem:a6e8566ac7a5eeb0c14cf2387dfb8c1a1"><td class="memTemplItemLeft" align="right" valign="top">bool </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a6e8566ac7a5eeb0c14cf2387dfb8c1a1">operator==</a> (const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &a, const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &b)</td></tr>
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template<class T > </td></tr>
<tr class="memitem:a7ef00d65394827ceb91597dda1f496f9"><td class="memTemplItemLeft" align="right" valign="top">bool </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a7ef00d65394827ceb91597dda1f496f9">operator!=</a> (const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &a, const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &b)</td></tr>
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template<class T > </td></tr>
<tr class="memitem:a48db273f73f86955938b99faeef6e113"><td class="memTemplItemLeft" align="right" valign="top">bool </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a48db273f73f86955938b99faeef6e113">operator<</a> (const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &a, const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &b)</td></tr>
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template<class T > </td></tr>
<tr class="memitem:a993ddc5c77998a907582247107f6e6c5"><td class="memTemplItemLeft" align="right" valign="top">bool </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a993ddc5c77998a907582247107f6e6c5">operator<=</a> (const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &a, const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &b)</td></tr>
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template<class T > </td></tr>
<tr class="memitem:a4ba09ef10dc88c605edf40669322d8d4"><td class="memTemplItemLeft" align="right" valign="top">bool </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a4ba09ef10dc88c605edf40669322d8d4">operator></a> (const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &a, const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &b)</td></tr>
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template<class T > </td></tr>
<tr class="memitem:ade7571062c3e19cb6622bd2e411130ab"><td class="memTemplItemLeft" align="right" valign="top">bool </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#ade7571062c3e19cb6622bd2e411130ab">operator>=</a> (const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &a, const <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &b)</td></tr>
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template<class T > </td></tr>
<tr class="memitem:ae0973243c4b58d53d6f11ce5a2535a8c"><td class="memTemplItemLeft" align="right" valign="top">void </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#ae0973243c4b58d53d6f11ce5a2535a8c">swap</a> (<a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &a, <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1trivial__vector.html">trivial_vector</a>< T > &b) noexcept</td></tr>
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<tr class="memitem:a0e474a5af3258fc971c71d057c8fb0bb"><td class="memTemplParams" colspan="2">template<class T , class... Args> </td></tr>
<tr class="memitem:a0e474a5af3258fc971c71d057c8fb0bb"><td class="memTemplItemLeft" align="right" valign="top">result< <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1cached__parent__handle__adapter.html">cached_parent_handle_adapter</a>< T > > </td><td class="memTemplItemRight" valign="bottom"><a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a0e474a5af3258fc971c71d057c8fb0bb">cache_parent</a> (Args &&... args) noexcept</td></tr>
<tr class="memdesc:a0e474a5af3258fc971c71d057c8fb0bb"><td class="mdescLeft"> </td><td class="mdescRight">Constructs a <code>T</code> adapted into a parent handle caching implementation. <a href="namespacellfio__v2__xxx_1_1algorithm.html#a0e474a5af3258fc971c71d057c8fb0bb">More...</a><br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Collection of file system based algorithms. </p>
</div><h2 class="groupheader">Typedef Documentation</h2>
<a id="a27450e894b5dab6c18a01350670fa0dc"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a27450e894b5dab6c18a01350670fa0dc">◆ </a></span>xor_handle_adapter</h2>
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template<class Target , class Source > </div>
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<td class="memname">using <a class="el" href="namespacellfio__v2__xxx_1_1algorithm.html#a27450e894b5dab6c18a01350670fa0dc">llfio_v2_xxx::algorithm::xor_handle_adapter</a> = typedef <a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1combining__handle__adapter.html">combining_handle_adapter</a><detail::xor_handle_adapter_op, Target, Source></td>
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<p>A handle combining the data from two other handles using XOR. </p>
<dl class="tparams"><dt>Template Parameters</dt><dd>
<table class="tparams">
<tr><td class="paramname">Target</td><td>The type of the target handle. This is the one written to during any writes i.e. the input and second handle are XORed together and written to the first handle. </td></tr>
<tr><td class="paramname">Source</td><td>The type of the second handle with which to XOR the target handle.</td></tr>
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</dd>
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<dl class="section warning"><dt>Warning</dt><dd>This class is still in development, do not use. </dd></dl>
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<h2 class="groupheader">Function Documentation</h2>
<a id="a0e474a5af3258fc971c71d057c8fb0bb"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a0e474a5af3258fc971c71d057c8fb0bb">◆ </a></span>cache_parent()</h2>
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<td class="memname">result<<a class="el" href="classllfio__v2__xxx_1_1algorithm_1_1cached__parent__handle__adapter.html">cached_parent_handle_adapter</a><T> > llfio_v2_xxx::algorithm::cache_parent </td>
<td>(</td>
<td class="paramtype">Args &&... </td>
<td class="paramname"><em>args</em></td><td>)</td>
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<p>Constructs a <code>T</code> adapted into a parent handle caching implementation. </p>
<p>This function works via the <code>construct<T>()</code> free function framework for which your <code>handle</code> implementation must have registered its construction details. </p>
<div class="fragment"><div class="line"><a name="l00182"></a><span class="lineno"> 182</span>  {</div>
<div class="line"><a name="l00183"></a><span class="lineno"> 183</span>  construct<T> constructor{std::forward<Args>(args)...};</div>
<div class="line"><a name="l00184"></a><span class="lineno"> 184</span>  OUTCOME_TRY(<span class="keyword">auto</span> &&h, constructor());</div>
<div class="line"><a name="l00185"></a><span class="lineno"> 185</span>  <span class="keywordflow">try</span></div>
<div class="line"><a name="l00186"></a><span class="lineno"> 186</span>  {</div>
<div class="line"><a name="l00187"></a><span class="lineno"> 187</span>  <span class="keywordflow">return</span> cached_parent_handle_adapter<T>(std::move(h), constructor.base, constructor._path);</div>
<div class="line"><a name="l00188"></a><span class="lineno"> 188</span>  }</div>
<div class="line"><a name="l00189"></a><span class="lineno"> 189</span>  <span class="keywordflow">catch</span>(...)</div>
<div class="line"><a name="l00190"></a><span class="lineno"> 190</span>  {</div>
<div class="line"><a name="l00191"></a><span class="lineno"> 191</span>  <span class="keywordflow">return</span> error_from_exception();</div>
<div class="line"><a name="l00192"></a><span class="lineno"> 192</span>  }</div>
<div class="line"><a name="l00193"></a><span class="lineno"> 193</span>  }</div>
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<h2 class="memtitle"><span class="permalink"><a href="#a3c661d6cba0da25fe9e1211ede1fd004">◆ </a></span>clone_or_copy()</h2>
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<td class="memname">result<file_handle::extent_type> llfio_v2_xxx::algorithm::clone_or_copy </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a> & </td>
<td class="paramname"><em>src</em>, </td>
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<td class="paramtype">const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> & </td>
<td class="paramname"><em>destdir</em>, </td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view</a> </td>
<td class="paramname"><em>destleaf</em> = <code>{}</code>, </td>
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<td class="paramtype">bool </td>
<td class="paramname"><em>preserve_timestamps</em> = <code>true</code>, </td>
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<td class="paramtype">bool </td>
<td class="paramname"><em>force_copy_now</em> = <code>false</code>, </td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42">file_handle::creation</a> </td>
<td class="paramname"><em>creation</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42af7cf95e0f43dc8f79e39ae628c85a11d">file_handle::creation::always_new</a></code>, </td>
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<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> </td>
<td class="paramname"><em>d</em> = <code>{}</code> </td>
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<p>Clone or copy the extents of the filesystem entity identified by <code>src</code> to <code>destdir</code> optionally renamed to <code>destleaf</code>. </p>
<dl class="section return"><dt>Returns</dt><dd>The number of bytes cloned or copied. </dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">src</td><td>The file to clone or copy. </td></tr>
<tr><td class="paramname">destdir</td><td>The base to lookup <code>destleaf</code> within. </td></tr>
<tr><td class="paramname">destleaf</td><td>The leafname to use. If empty, use the same leafname as <code>src</code> currently has. </td></tr>
<tr><td class="paramname">preserve_timestamps</td><td>Use <code>stat_t::stamp()</code> to preserve as much metadata from the original to the clone/copy as possible. </td></tr>
<tr><td class="paramname">force_copy_now</td><td>Parameter to pass to <code>file_handle::clone_extents()</code> to force extents to be copied now, not copy-on-write lazily later. </td></tr>
<tr><td class="paramname">creation</td><td>How to create the destination file handle. NOTE that if this is NOT <code>always_new</code>, if the destination has identical maximum extent and last modified timestamp (and permissions on POSIX) to the source, it is NOT copied, and zero is returned. </td></tr>
<tr><td class="paramname">d</td><td>Deadline by which to complete the operation.</td></tr>
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<p>Firstly, a <code>file_handle</code> is constructed at the destination using <code>creation</code>, which defaults to always creating a new inode. The caching used for the destination handle is replicated from the source handle – be aware that not caching metadata is expensive.</p>
<p>Next <code>file_handle::clone_extents()</code> with <code>emulate_if_unsupported = false</code> is called on the whole file content. If extent cloning is supported, this will be very fast and not consume new disk space (note: except on networked filesystems). If the source file is sparsely allocated, the destination will have identical sparse allocation.</p>
<p>If the previous operation did not succeed, the disk free space is checked using <code>statfs_t</code>, and if the copy would exceed current disk free space, the destination file is unlinked and an error code comparing equal to <code>errc::no_space_on_device</code> is returned.</p>
<p>Next, <code>file_handle::clone_extents()</code> with <code>emulate_if_unsupported = true</code> is called on the whole file content. This copies only the allocated extents in blocks sized whatever is the large page size on this platform (2Mb on x64).</p>
<p>Finally, if <code>preserve_timestamps</code> is true, the destination file handle is restamped with the metadata from the source file handle just before the destination file handle is closed. </p>
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<h2 class="memtitle"><span class="permalink"><a href="#afae251fc3bfb7280b47b6135e2f6c7e2">◆ </a></span>contents()</h2>
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<td class="memname">result<<a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1contents__visitor_1_1contents__type.html">contents_visitor::contents_type</a>> llfio_v2_xxx::algorithm::contents </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> & </td>
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<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1contents__visitor.html">contents_visitor</a> * </td>
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<td class="paramname"><em>threads</em> = <code>0</code>, </td>
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<p>Calculate the contents of everything within and under <code>dirh</code>. What is returned is unordered. </p>
<p>This is a very thin veneer over <code>traverse()</code> which came out of the fact that I kept writing "get me the contents" traversal visitors again and again, so eventually I just wrote a library edition. Its only "clever" bit is that it stores the contents in thread local storage, and merges the contents afterwards.</p>
<p>It is race free to concurrent relocations of <code>dirh</code>. It is entirely implemented in header-only code, as it is very simple. </p>
<div class="fragment"><div class="line"><a name="l00225"></a><span class="lineno"> 225</span>  {</div>
<div class="line"><a name="l00226"></a><span class="lineno"> 226</span>  contents_visitor default_visitor;</div>
<div class="line"><a name="l00227"></a><span class="lineno"> 227</span>  <span class="keywordflow">if</span>(visitor == <span class="keyword">nullptr</span>)</div>
<div class="line"><a name="l00228"></a><span class="lineno"> 228</span>  {</div>
<div class="line"><a name="l00229"></a><span class="lineno"> 229</span>  visitor = &default_visitor;</div>
<div class="line"><a name="l00230"></a><span class="lineno"> 230</span>  }</div>
<div class="line"><a name="l00231"></a><span class="lineno"> 231</span>  contents_visitor::_state_type state(dirh);</div>
<div class="line"><a name="l00232"></a><span class="lineno"> 232</span>  OUTCOME_TRY(<span class="keyword">auto</span> &&dirhpath, dirh.current_path());</div>
<div class="line"><a name="l00233"></a><span class="lineno"> 233</span>  state.rootdirpathlen.store(dirhpath.native().size() + 1, std::memory_order_relaxed);</div>
<div class="line"><a name="l00234"></a><span class="lineno"> 234</span>  OUTCOME_TRY(<a class="code" href="namespacellfio__v2__xxx_1_1algorithm.html#ae068bc16598189811d0ce2b3530f1de7">traverse</a>(dirh, visitor, threads, &state, force_slow_path));</div>
<div class="line"><a name="l00235"></a><span class="lineno"> 235</span>  <span class="keywordflow">return</span> {std::move(state.contents)};</div>
<div class="line"><a name="l00236"></a><span class="lineno"> 236</span>  }</div>
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<h2 class="memtitle"><span class="permalink"><a href="#a05594f7c8ae275fa65b2acd57cc9b8ac">◆ </a></span>reduce()</h2>
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<td class="memname">result<size_t> llfio_v2_xxx::algorithm::reduce </td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1directory__handle.html">directory_handle</a> && </td>
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<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1reduce__visitor.html">reduce_visitor</a> * </td>
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<p>Reduce the directory identified <code>dirh</code>, and everything therein, to the null set. </p>
<p>You might be surprised to learn that most directory tree removal implementations are of poor quality, not leveraging the filesystem facilities that are available, not handling concurrent modification of the filesystem correctly, having poor performance, or failing to handle not uncommon corner cases. This implementation is considerably better quality, indeed it is to my knowledge the highest quality possible on at least Linux and Microsoft Windows.</p>
<p>The algorithm is as follows:</p>
<ol type="1">
<li>Attempt to rename <code>dirh</code> to a uniquely named directory. If successful, this causes concurrent users to no longer see the directory tree. It also usefully detects if permissions problems would prevent whole directory tree removal. Note that on Windows, if any process has a handle open to anything inside the directory tree, it is usually the case that all renames will be prevented.</li>
<li><code>algorithm::traverse()</code> is begun, using the visitor supplied. This will unlink all items using a breadth-first algorithm, from root to tips. With the default visitor, directories which cannot be opened for traversal are ignored; entries which cannot be unlinked are attempted to be renamed into the base directory; entries which cannot be renamed are ignored.</li>
<li>Except for unrenameable files, now the entire directory tree will have been reduced to a minimum possible set of uniquely named items in the base directory, all of which by definition must be undeletable. We now loop attempting to reduce the remaining entries. The default visitor implementation takes a timeout, which if exceeded, an error code comparing equal to <code>errc::timed_out</code> is returned.</li>
</ol>
<p>Even on slow filesystems such as those on Windows, or networked filesystems, this algorithm performs very well. We do not currently inspect the filing system to see if bisect unlinking directories with millions of entries will perform well (some filing systems can store very large directories with multiple independent inode locks, thus using multiple kernel threads on the same directory sees a large performance increase for very large directories). We also remove items based on enumerated order, under the assumption that filesystems will have optimised for this specific use case.</p>
<p>If the function succeeds, <code>dirh</code> is moved into the function, and the total number of filesystem entries removed is returned.</p>
<p>If the function fails, <code>dirh</code> is NOT moved into the function, and continues to refer to the (likely renamed) directory you passed in. You might do something like try to rename it into <code>storage_backed_temporary_files_directory()</code>, or some other hail mary action.</p>
<p>You should review the documentation for <code>algorithm::traverse()</code>, as this algorithm is entirely implemented using that algorithm. </p>
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<h2 class="memtitle"><span class="permalink"><a href="#a6165d32704ff21b4aed3046f11b31cb0">◆ </a></span>summarize()</h2>
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<td class="memname">result< <a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1traversal__summary.html">traversal_summary</a> > llfio_v2_xxx::algorithm::summarize </td>
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<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1algorithm_1_1summarize__visitor.html">summarize_visitor</a> * </td>
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<p>Summarise the directory identified <code>dirh</code>, and everything therein. </p>
<p>It can be useful to summarise a directory hierarchy, especially to determine how much storage it occupies, but also how many mounted filesystems it straddles etc. You should specify what metadata you wish to summarise, if this is a subset of what metadata <code>directory_handle::read()</code> returns, performance will be considerably better. The default summarises all possible metadata.</p>
<p>This is a trivial implementation on top of <code>algorithm::traverse()</code>, indeed it is implemented entirely as header code. You should review the documentation for <code>algorithm::traverse()</code>, as this algorithm is entirely implemented using that algorithm. </p>
<div class="fragment"><div class="line"><a name="l00117"></a><span class="lineno"> 117</span>  {</div>
<div class="line"><a name="l00118"></a><span class="lineno"> 118</span>  LLFIO_LOG_FUNCTION_CALL(&dirh);</div>
<div class="line"><a name="l00119"></a><span class="lineno"> 119</span>  summarize_visitor default_visitor;</div>
<div class="line"><a name="l00120"></a><span class="lineno"> 120</span>  <span class="keywordflow">if</span>(visitor == <span class="keyword">nullptr</span>)</div>
<div class="line"><a name="l00121"></a><span class="lineno"> 121</span>  {</div>
<div class="line"><a name="l00122"></a><span class="lineno"> 122</span>  visitor = &default_visitor;</div>
<div class="line"><a name="l00123"></a><span class="lineno"> 123</span>  }</div>
<div class="line"><a name="l00124"></a><span class="lineno"> 124</span>  result<traversal_summary> state(in_place_type<traversal_summary>);</div>
<div class="line"><a name="l00125"></a><span class="lineno"> 125</span>  state.assume_value().want = want;</div>
<div class="line"><a name="l00126"></a><span class="lineno"> 126</span>  directory_entry entry{{}, stat_t(<span class="keyword">nullptr</span>)};</div>
<div class="line"><a name="l00127"></a><span class="lineno"> 127</span>  OUTCOME_TRY(entry.stat.fill(dirh, want));</div>
<div class="line"><a name="l00128"></a><span class="lineno"> 128</span>  OUTCOME_TRY(summarize_visitor::accumulate(state.assume_value(), &state.assume_value(), <span class="keyword">nullptr</span>, entry, want));</div>
<div class="line"><a name="l00129"></a><span class="lineno"> 129</span>  OUTCOME_TRY(<a class="code" href="namespacellfio__v2__xxx_1_1algorithm.html#ae068bc16598189811d0ce2b3530f1de7">traverse</a>(dirh, visitor, threads, &state.assume_value(), force_slow_path));</div>
<div class="line"><a name="l00130"></a><span class="lineno"> 130</span>  <span class="keywordflow">return</span> state;</div>
<div class="line"><a name="l00131"></a><span class="lineno"> 131</span>  }</div>
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<h2 class="memtitle"><span class="permalink"><a href="#ae068bc16598189811d0ce2b3530f1de7">◆ </a></span>traverse()</h2>
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<p>Traverse everything within and under <code>dirh</code>. </p>
<p>The algorithm is as follows:</p>
<ol type="1">
<li>Call <code>pre_enumeration()</code> of the visitor on the <code>directory_handle</code> about to be enumerated.</li>
<li>Enumerate the contents of the directory.</li>
<li>Call <code>post_enumeration()</code> of the visitor on the contents just enumerated.</li>
<li>For each directory in the contents, append the directory handle and each directory leafname to its hierarchy depth level in a stack of lists.</li>
<li>Loop, using the least deep available item in the stack, until the stack is empty.</li>
</ol>
<p>If <code>known_dirs_remaining</code> exceeds four, a threadpool of not more than <code>threads</code> threads is spun up in order to traverse the hierarchy more quickly.</p>
<p>This algorithm is therefore primarily a breadth-first algorithm, in that we proceed from root, level by level, to the tips. The number returned is the total number of directories traversed.</p>
<h2><a class="anchor" id="autotoc_md17"></a>
Notes</h2>
<p>The implementation tries hard to not open too many file descriptors at a time in order to not exceed the system limit, which may be as low as 1024 on POSIX. On POSIX, it checks <code>getrlimit(RLIMIT_NOFILE)</code> for the soft limit on open file descriptors, and if the remaining unused open file descriptors is less than 65536, it will prefer a slow path implementation which exchanges file descriptor usage for lots more dynamic memory allocation and memory copying. You can force this slow path on any platform using <code>force_slow_path</code>, and in correct code you should always check for failures in <code>directory_open_failed()</code> comparing equal to <code>errc::too_many_files_open</code>, and if encountered restart the traversal using the slow path forced.</p>
<p>Almost every modern POSIX system allows a <code>RLIMIT_NOFILE</code> of over a million nowadays, so you should <code>setrlimit(RLIMIT_NOFILE)</code> appropriately in your program if you are absolutely sure that doing so will not break code in your program (e.g. <code>select()</code> fails spectacularly if file descriptors exceed 1024 on most POSIX).</p>
<p>To give an idea of the difference slow path makes, for Linux ext4:</p>
<ul>
<li>Slow path, 1 thread, traversed 131,915 directories and 8,254,162 entries in 3.10 seconds.</li>
<li>Slow path, 16 threads, traversed 131,915 directories and 8,254,162 entries in 0.966 seconds.</li>
<li>Fast path, 1 thread, traversed 131,915 directories and 8,254,162 entries in 2.73 seconds (+12%).</li>
<li>Fast path, 16 threads, traversed 131,915 directories and 8,254,162 entries in 0.525 seconds (+46%). </li>
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