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 <span id="projectnumber">v2.00 late alpha</span>
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<div class="title">llfio_v2_xxx::fast_random_file_handle Class Reference<span class="mlabels"><span class="mlabel">abstract</span></span></div> </div>
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<p>A handle to synthesised, non-cryptographic, pseudo-random data.
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<p><code>#include "fast_random_file_handle.hpp"</code></p>
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<tr class="memitem:a55f9c712b4ece6066a4269a73d229bfb"><td class="memItemLeft" align="right" valign="top"><a id="a55f9c712b4ece6066a4269a73d229bfb"></a>
using </td><td class="memItemRight" valign="bottom"><b>dev_t</b> = file_handle::dev_t</td></tr>
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using </td><td class="memItemRight" valign="bottom"><b>ino_t</b> = file_handle::ino_t</td></tr>
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<tr class="memitem:ac8b7de182379e57f0b40fda48d58822d"><td class="memItemLeft" align="right" valign="top"><a id="ac8b7de182379e57f0b40fda48d58822d"></a>
using </td><td class="memItemRight" valign="bottom"><b>path_view_type</b> = <a class="el" href="classllfio__v2__xxx_1_1path__view.html">file_handle::path_view_type</a></td></tr>
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<tr class="memitem:a22771acd68f6b630d3861c60aaa25a41"><td class="memItemLeft" align="right" valign="top"><a id="a22771acd68f6b630d3861c60aaa25a41"></a>
using </td><td class="memItemRight" valign="bottom"><b>path_type</b> = io_handle::path_type</td></tr>
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using </td><td class="memItemRight" valign="bottom"><b>extent_type</b> = io_handle::extent_type</td></tr>
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using </td><td class="memItemRight" valign="bottom"><b>size_type</b> = io_handle::size_type</td></tr>
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<tr class="memitem:a5baa53702ad860fa9c3fb5af28f14fd8"><td class="memItemLeft" align="right" valign="top"><a id="a5baa53702ad860fa9c3fb5af28f14fd8"></a>
using </td><td class="memItemRight" valign="bottom"><b>mode</b> = <a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">io_handle::mode</a></td></tr>
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using </td><td class="memItemRight" valign="bottom"><b>creation</b> = <a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42">io_handle::creation</a></td></tr>
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using </td><td class="memItemRight" valign="bottom"><b>caching</b> = <a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">io_handle::caching</a></td></tr>
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<tr class="memitem:a6c0545db3c2e8fe9ffdafbfbe4b7f6e2"><td class="memItemLeft" align="right" valign="top"><a id="a6c0545db3c2e8fe9ffdafbfbe4b7f6e2"></a>
using </td><td class="memItemRight" valign="bottom"><b>flag</b> = io_handle::flag</td></tr>
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<tr class="memitem:a1020835dc0f70fbc8a7b852fa8d5c0b6"><td class="memItemLeft" align="right" valign="top"><a id="a1020835dc0f70fbc8a7b852fa8d5c0b6"></a>
using </td><td class="memItemRight" valign="bottom"><b>buffer_type</b> = <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1buffer__type.html">io_handle::buffer_type</a></td></tr>
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<tr class="memitem:a39516dc5f2780e42afe5dbb836829f56"><td class="memItemLeft" align="right" valign="top"><a id="a39516dc5f2780e42afe5dbb836829f56"></a>
using </td><td class="memItemRight" valign="bottom"><b>const_buffer_type</b> = <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1const__buffer__type.html">io_handle::const_buffer_type</a></td></tr>
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using </td><td class="memItemRight" valign="bottom"><b>buffers_type</b> = <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a8f525d9665b524442b46cd55678817ed">io_handle::buffers_type</a></td></tr>
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<tr class="memitem:a4b0a7e494477cecde8e160f8f20ef572"><td class="memItemLeft" align="right" valign="top"><a id="a4b0a7e494477cecde8e160f8f20ef572"></a>
using </td><td class="memItemRight" valign="bottom"><b>const_buffers_type</b> = <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a693a8c64bb7de1a6835d6a151e37aa0e">io_handle::const_buffers_type</a></td></tr>
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<tr class="memitem:a55b1ab8db8c3016c5bc75f1548e2f8e8"><td class="memTemplParams" colspan="2"><a id="a55b1ab8db8c3016c5bc75f1548e2f8e8"></a>
template<class T > </td></tr>
<tr class="memitem:a55b1ab8db8c3016c5bc75f1548e2f8e8"><td class="memTemplItemLeft" align="right" valign="top">using </td><td class="memTemplItemRight" valign="bottom"><b>io_request</b> = <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_handle::io_request</a>< T ></td></tr>
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template<class T > </td></tr>
<tr class="memitem:a386543b3dd65d4d416d755a153eef593"><td class="memTemplItemLeft" align="right" valign="top">using </td><td class="memTemplItemRight" valign="bottom"><b>io_result</b> = <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_handle::io_result</a>< T ></td></tr>
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<tr class="memitem:aa25e3ab298152166fc387d8fcfb19a63"><td class="memItemLeft" align="right" valign="top">enum  </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63">lock_kind</a> { <b>unknown</b>,
<a class="el" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63a9e81e7b963c71363e2fb3eefcfecfc0e">lock_kind::shared</a>,
<a class="el" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63aa4293995cfbfa9ce60ce71ade2ff75f7">lock_kind::exclusive</a>
}<tr class="memdesc:aa25e3ab298152166fc387d8fcfb19a63"><td class="mdescLeft"> </td><td class="mdescRight">The kinds of concurrent user exclusion which can be performed. <a href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63">More...</a><br /></td></tr>
</td></tr>
<tr class="separator:aa25e3ab298152166fc387d8fcfb19a63"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a7816bb7ae5156fa2997b68e6300ae565"><td class="memItemLeft" align="right" valign="top">enum  </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565">barrier_kind</a> { <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565a2f6648dac37731813bb84ae9b24bdfdb">barrier_kind::nowait_data_only</a>,
<a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565af1d3baf03681db9a9986e0a76d6107ce">barrier_kind::wait_data_only</a>,
<a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565ab7a52d26120f585b21e8960812db5bf1">barrier_kind::nowait_all</a>,
<a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565a4e1789381cf8c976ec7a7118b3529345">barrier_kind::wait_all</a>
}<tr class="memdesc:a7816bb7ae5156fa2997b68e6300ae565"><td class="mdescLeft"> </td><td class="mdescRight">The kinds of write reordering barrier which can be performed. <a href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565">More...</a><br /></td></tr>
</td></tr>
<tr class="separator:a7816bb7ae5156fa2997b68e6300ae565"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a1a65884346740af7fb4648c79d44a750"><td class="memItemLeft" align="right" valign="top"><a id="a1a65884346740af7fb4648c79d44a750"></a>
using </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#a1a65884346740af7fb4648c79d44a750">unique_id_type</a> = QUICKCPPLIB_NAMESPACE::integers128::uint128</td></tr>
<tr class="memdesc:a1a65884346740af7fb4648c79d44a750"><td class="mdescLeft"> </td><td class="mdescRight">The unique identifier type used by this handle. <br /></td></tr>
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</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-methods"></a>
Public Member Functions</h2></td></tr>
<tr class="memitem:a4661a9c1551d33d054ccd80599806ba7"><td class="memItemLeft" align="right" valign="top"><a id="a4661a9c1551d33d054ccd80599806ba7"></a>
 </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a4661a9c1551d33d054ccd80599806ba7">fast_random_file_handle</a> ()=default</td></tr>
<tr class="memdesc:a4661a9c1551d33d054ccd80599806ba7"><td class="mdescLeft"> </td><td class="mdescRight">Default constructor. <br /></td></tr>
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<tr class="memitem:a2b7cbbd9f7cb5563cb08e7ca26225a63"><td class="memItemLeft" align="right" valign="top"><a id="a2b7cbbd9f7cb5563cb08e7ca26225a63"></a>
 </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a2b7cbbd9f7cb5563cb08e7ca26225a63">fast_random_file_handle</a> (extent_type <a class="el" href="namespacellfio__v2__xxx.html#aa3676f0dd69f4b54cf7e14e3f86d32b9">length</a>, span< const byte > seed)</td></tr>
<tr class="memdesc:a2b7cbbd9f7cb5563cb08e7ca26225a63"><td class="mdescLeft"> </td><td class="mdescRight">Constructor. Seed is not much use past sixteen bytes. <br /></td></tr>
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<tr class="memitem:af63fe21c3bf2095a1b232687f10ab1ca"><td class="memItemLeft" align="right" valign="top"><a id="af63fe21c3bf2095a1b232687f10ab1ca"></a>
 </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#af63fe21c3bf2095a1b232687f10ab1ca">fast_random_file_handle</a> (<a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a> &&o) noexcept</td></tr>
<tr class="memdesc:af63fe21c3bf2095a1b232687f10ab1ca"><td class="mdescLeft"> </td><td class="mdescRight">Implicit move construction of fast_random_file_handle permitted. <br /></td></tr>
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<tr class="memitem:af201782a92c5c9ceac071f8358dd6247"><td class="memItemLeft" align="right" valign="top"><a id="af201782a92c5c9ceac071f8358dd6247"></a>
 </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#af201782a92c5c9ceac071f8358dd6247">fast_random_file_handle</a> (const <a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a> &)=delete</td></tr>
<tr class="memdesc:af201782a92c5c9ceac071f8358dd6247"><td class="mdescLeft"> </td><td class="mdescRight">No copy construction (use <code>clone()</code>) <br /></td></tr>
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<tr class="memitem:a16ccaa28c68e06e7c3d5f7ff94d2cea5"><td class="memItemLeft" align="right" valign="top"><a id="a16ccaa28c68e06e7c3d5f7ff94d2cea5"></a>
<a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a> & </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a16ccaa28c68e06e7c3d5f7ff94d2cea5">operator=</a> (<a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a> &&o) noexcept</td></tr>
<tr class="memdesc:a16ccaa28c68e06e7c3d5f7ff94d2cea5"><td class="mdescLeft"> </td><td class="mdescRight">Move assignment of fast_random_file_handle permitted. <br /></td></tr>
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<tr class="memitem:a5477b7a397fce509e1fd04092a559e8c"><td class="memItemLeft" align="right" valign="top"><a id="a5477b7a397fce509e1fd04092a559e8c"></a>
<a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a> & </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a5477b7a397fce509e1fd04092a559e8c">operator=</a> (const <a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a> &)=delete</td></tr>
<tr class="memdesc:a5477b7a397fce509e1fd04092a559e8c"><td class="mdescLeft"> </td><td class="mdescRight">No copy assignment. <br /></td></tr>
<tr class="separator:a5477b7a397fce509e1fd04092a559e8c"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:abc5627ee63a95d17499f079d890e6af9"><td class="memItemLeft" align="right" valign="top"><a id="abc5627ee63a95d17499f079d890e6af9"></a>
void </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#abc5627ee63a95d17499f079d890e6af9">swap</a> (<a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a> &o) noexcept</td></tr>
<tr class="memdesc:abc5627ee63a95d17499f079d890e6af9"><td class="mdescLeft"> </td><td class="mdescRight">Swap with another instance. <br /></td></tr>
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<tr class="memitem:ad67d4e8da0a8fa8719f301d577418165"><td class="memItemLeft" align="right" valign="top"><a id="ad67d4e8da0a8fa8719f301d577418165"></a>
virtual result< void > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#ad67d4e8da0a8fa8719f301d577418165">close</a> () noexcept override</td></tr>
<tr class="memdesc:ad67d4e8da0a8fa8719f301d577418165"><td class="mdescLeft"> </td><td class="mdescRight">Immediately close the native handle type managed by this handle. <br /></td></tr>
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<tr class="memitem:a800e1a97e8dc3f9cc74dc2115d476398"><td class="memItemLeft" align="right" valign="top"><a id="a800e1a97e8dc3f9cc74dc2115d476398"></a>
virtual result< extent_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a800e1a97e8dc3f9cc74dc2115d476398">maximum_extent</a> () const noexcept override</td></tr>
<tr class="memdesc:a800e1a97e8dc3f9cc74dc2115d476398"><td class="mdescLeft"> </td><td class="mdescRight">Return the current maximum permitted extent of the file. <br /></td></tr>
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<tr class="memitem:a3e147cacf24cb8d96b6c57f30692fda2"><td class="memItemLeft" align="right" valign="top"><a id="a3e147cacf24cb8d96b6c57f30692fda2"></a>
virtual result< extent_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a3e147cacf24cb8d96b6c57f30692fda2">truncate</a> (extent_type newsize) noexcept override</td></tr>
<tr class="memdesc:a3e147cacf24cb8d96b6c57f30692fda2"><td class="mdescLeft"> </td><td class="mdescRight">Resize the current maximum permitted extent of the random file to the given extent. <br /></td></tr>
<tr class="separator:a3e147cacf24cb8d96b6c57f30692fda2"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ab88d8d93300d1525d52ad1eb4e00e504"><td class="memItemLeft" align="right" valign="top"><a id="ab88d8d93300d1525d52ad1eb4e00e504"></a>
virtual result< extent_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#ab88d8d93300d1525d52ad1eb4e00e504">zero</a> (extent_type, extent_type bytes, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept override</td></tr>
<tr class="memdesc:ab88d8d93300d1525d52ad1eb4e00e504"><td class="mdescLeft"> </td><td class="mdescRight">Zero a portion of the random file (does nothing). <br /></td></tr>
<tr class="separator:ab88d8d93300d1525d52ad1eb4e00e504"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a9bc75ea73ffb575d36e9800b8e1e5af0"><td class="memItemLeft" align="right" valign="top"><a id="a9bc75ea73ffb575d36e9800b8e1e5af0"></a>
virtual result< std::vector< std::pair< extent_type, extent_type > > > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a9bc75ea73ffb575d36e9800b8e1e5af0">extents</a> () const noexcept override</td></tr>
<tr class="memdesc:a9bc75ea73ffb575d36e9800b8e1e5af0"><td class="mdescLeft"> </td><td class="mdescRight">Return a single extent of the maximum extent. <br /></td></tr>
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<tr class="memitem:ae84ac3c127d067d44d978e4621d4d2f1"><td class="memItemLeft" align="right" valign="top">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a>< buffers_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#ae84ac3c127d067d44d978e4621d4d2f1">read</a> (<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< buffers_type > reqs, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept override</td></tr>
<tr class="memdesc:ae84ac3c127d067d44d978e4621d4d2f1"><td class="mdescLeft"> </td><td class="mdescRight">Read data from the random file. <a href="#ae84ac3c127d067d44d978e4621d4d2f1">More...</a><br /></td></tr>
<tr class="separator:ae84ac3c127d067d44d978e4621d4d2f1"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:abdbe878fecb166d1eda5ddc4718e101d"><td class="memItemLeft" align="right" valign="top">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a>< const_buffers_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#abdbe878fecb166d1eda5ddc4718e101d">write</a> (<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type > reqs, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept override</td></tr>
<tr class="memdesc:abdbe878fecb166d1eda5ddc4718e101d"><td class="mdescLeft"> </td><td class="mdescRight">Fails to write to the random file. <a href="#abdbe878fecb166d1eda5ddc4718e101d">More...</a><br /></td></tr>
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<tr class="memitem:a28f78f709ba3d7b26ba38cefa21fd7b8"><td class="memItemLeft" align="right" valign="top"><a id="a28f78f709ba3d7b26ba38cefa21fd7b8"></a>
virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a>< const_buffers_type > </td><td class="memItemRight" valign="bottom"><b>barrier</b> (<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type > reqs=<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type >(), <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565">barrier_kind</a>=<a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565a2f6648dac37731813bb84ae9b24bdfdb">barrier_kind::nowait_data_only</a>, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept override</td></tr>
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<tr class="memitem:a3b27d0f83fb72ebaa1e6a2eead9bec3e"><td class="memItemLeft" align="right" valign="top">virtual result< <a class="el" href="classllfio__v2__xxx_1_1file__handle_1_1extent__guard.html">extent_guard</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a3b27d0f83fb72ebaa1e6a2eead9bec3e">lock_range</a> (extent_type offset, extent_type bytes, <a class="el" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63">lock_kind</a> kind, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept override</td></tr>
<tr class="memdesc:a3b27d0f83fb72ebaa1e6a2eead9bec3e"><td class="mdescLeft"> </td><td class="mdescRight">EXTENSION: Tries to lock the range of bytes specified for shared or exclusive access. Be aware this passes through the same semantics as the underlying OS call, including any POSIX insanity present on your platform: <a href="#a3b27d0f83fb72ebaa1e6a2eead9bec3e">More...</a><br /></td></tr>
<tr class="separator:a3b27d0f83fb72ebaa1e6a2eead9bec3e"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a0b20ae88c350702b39f41d8223f0b164"><td class="memItemLeft" align="right" valign="top">virtual void </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a0b20ae88c350702b39f41d8223f0b164">unlock_range</a> (extent_type, extent_type) noexcept override</td></tr>
<tr class="memdesc:a0b20ae88c350702b39f41d8223f0b164"><td class="mdescLeft"> </td><td class="mdescRight">EXTENSION: Unlocks a byte range previously locked. <a href="#a0b20ae88c350702b39f41d8223f0b164">More...</a><br /></td></tr>
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<tr class="memitem:ad0cfbde678b809518ca005251ec64808"><td class="memItemLeft" align="right" valign="top"><a id="ad0cfbde678b809518ca005251ec64808"></a>
void </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#ad0cfbde678b809518ca005251ec64808">swap</a> (<a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a> &o) noexcept</td></tr>
<tr class="memdesc:ad0cfbde678b809518ca005251ec64808"><td class="mdescLeft"> </td><td class="mdescRight">Swap with another instance. <br /></td></tr>
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<tr class="memitem:a4716696b8700953889006251e0678aa4"><td class="memItemLeft" align="right" valign="top"><a id="a4716696b8700953889006251e0678aa4"></a>
void </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a4716696b8700953889006251e0678aa4">swap</a> (<a class="el" href="classllfio__v2__xxx_1_1handle.html">handle</a> &o) noexcept</td></tr>
<tr class="memdesc:a4716696b8700953889006251e0678aa4"><td class="mdescLeft"> </td><td class="mdescRight">Swap with another instance. <br /></td></tr>
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<tr class="memitem:a823391cea8818da742c0d4c573f7300f"><td class="memItemLeft" align="right" valign="top">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a>< const_buffers_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a823391cea8818da742c0d4c573f7300f">barrier</a> (<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type > reqs=<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type >(), <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565">barrier_kind</a> kind=<a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565a2f6648dac37731813bb84ae9b24bdfdb">barrier_kind::nowait_data_only</a>, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept=0</td></tr>
<tr class="memdesc:a823391cea8818da742c0d4c573f7300f"><td class="mdescLeft"> </td><td class="mdescRight">Issue a write reordering barrier such that writes preceding the barrier will reach storage before writes after this barrier. <a href="#a823391cea8818da742c0d4c573f7300f">More...</a><br /></td></tr>
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<tr class="memitem:a6b97756d8d46e80da7d0fa04158a71a8"><td class="memItemLeft" align="right" valign="top">result< <a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a6b97756d8d46e80da7d0fa04158a71a8">clone</a> (<a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> mode_=mode::unchanged, <a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> caching_=caching::unchanged, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=std::chrono::seconds(30)) const noexcept</td></tr>
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<tr class="memitem:aeea4389189021b94dde6d8f2c3ccc5b3"><td class="memItemLeft" align="right" valign="top">result< <a class="el" href="classllfio__v2__xxx_1_1handle.html">handle</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aeea4389189021b94dde6d8f2c3ccc5b3">clone</a> () const noexcept</td></tr>
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<tr class="memitem:ae7735588338065ede0ab9b7f979bc65a"><td class="memItemLeft" align="right" valign="top"><a id="ae7735588338065ede0ab9b7f979bc65a"></a>
<a class="el" href="classllfio__v2__xxx_1_1io__service.html">io_service</a> * </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#ae7735588338065ede0ab9b7f979bc65a">service</a> () const noexcept</td></tr>
<tr class="memdesc:ae7735588338065ede0ab9b7f979bc65a"><td class="mdescLeft"> </td><td class="mdescRight">The i/o service this handle is attached to, if any. <br /></td></tr>
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<tr class="memitem:a6e46c6ea379152eb559ab15990f7c467"><td class="memItemLeft" align="right" valign="top"><a id="a6e46c6ea379152eb559ab15990f7c467"></a>
<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a>< size_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a6e46c6ea379152eb559ab15990f7c467">read</a> (extent_type offset, std::initializer_list< <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1buffer__type.html">buffer_type</a> > lst, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept</td></tr>
<tr class="memdesc:a6e46c6ea379152eb559ab15990f7c467"><td class="mdescLeft"> </td><td class="mdescRight">Convenience initialiser list based overload for <code>read()</code> <br /></td></tr>
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<tr class="memitem:a5f7485307a0704aa1680e5785be2035d"><td class="memItemLeft" align="right" valign="top">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a>< buffers_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a5f7485307a0704aa1680e5785be2035d">read</a> (<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< buffers_type > reqs, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept</td></tr>
<tr class="memdesc:a5f7485307a0704aa1680e5785be2035d"><td class="mdescLeft"> </td><td class="mdescRight">Read data from the open handle. <a href="#a5f7485307a0704aa1680e5785be2035d">More...</a><br /></td></tr>
<tr class="separator:a5f7485307a0704aa1680e5785be2035d"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a3c5c229b11f488d0e9bff74c65737db2"><td class="memItemLeft" align="right" valign="top">result< <a class="el" href="classllfio__v2__xxx_1_1file__handle_1_1extent__guard.html">extent_guard</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a3c5c229b11f488d0e9bff74c65737db2">lock_range</a> (<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< buffers_type > reqs, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept</td></tr>
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<tr class="memitem:a4055bb02680af02dcc189f0461bad503"><td class="memItemLeft" align="right" valign="top">result< <a class="el" href="classllfio__v2__xxx_1_1file__handle_1_1extent__guard.html">extent_guard</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a4055bb02680af02dcc189f0461bad503">lock_range</a> (<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type > reqs, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept</td></tr>
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<tr class="memitem:a2919da8c2520240c4e65f18f68872fd0"><td class="memItemLeft" align="right" valign="top">result< <a class="el" href="classllfio__v2__xxx_1_1file__handle_1_1extent__guard.html">extent_guard</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a2919da8c2520240c4e65f18f68872fd0">try_lock_range</a> (extent_type offset, extent_type bytes, <a class="el" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63">lock_kind</a> kind) noexcept</td></tr>
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<tr class="memitem:ade38a6d55a4eda3c6d5e196683b129a7"><td class="memItemLeft" align="right" valign="top">virtual size_t </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1io__handle.html#ade38a6d55a4eda3c6d5e196683b129a7">max_buffers</a> () const noexcept</td></tr>
<tr class="memdesc:ade38a6d55a4eda3c6d5e196683b129a7"><td class="mdescLeft"> </td><td class="mdescRight">The <em>maximum</em> number of buffers which a single read or write syscall can process at a time for this specific open handle. On POSIX, this is known as <code>IOV_MAX</code>. <a href="#ade38a6d55a4eda3c6d5e196683b129a7">More...</a><br /></td></tr>
<tr class="separator:ade38a6d55a4eda3c6d5e196683b129a7"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a83884eca7b4cd09125a5cf8a155e6052"><td class="memItemLeft" align="right" valign="top">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a>< const_buffers_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a83884eca7b4cd09125a5cf8a155e6052">write</a> (<a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type > reqs, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept</td></tr>
<tr class="memdesc:a83884eca7b4cd09125a5cf8a155e6052"><td class="mdescLeft"> </td><td class="mdescRight">Write data to the open handle. <a href="#a83884eca7b4cd09125a5cf8a155e6052">More...</a><br /></td></tr>
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<tr class="memitem:ab500784aa806dc7c2d90028d2f72de57"><td class="memItemLeft" align="right" valign="top"><a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a>< size_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1io__handle.html#ab500784aa806dc7c2d90028d2f72de57">write</a> (extent_type offset, std::initializer_list< <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1const__buffer__type.html">const_buffer_type</a> > lst, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()) noexcept</td></tr>
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<tr class="memitem:ac5222904f116c9beb0515a4a5aa850bf"><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#ac5222904f116c9beb0515a4a5aa850bf">QUICKCPPLIB_BITFIELD_BEGIN</a> (flag)</td></tr>
<tr class="memdesc:ac5222904f116c9beb0515a4a5aa850bf"><td class="mdescLeft"> </td><td class="mdescRight">Bitwise flags which can be specified. <a href="#ac5222904f116c9beb0515a4a5aa850bf">More...</a><br /></td></tr>
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<tr class="memitem:aa7e9bedf8c7a4c4a79a644a6e1857ee4"><td class="memItemLeft" align="right" valign="top"><a id="aa7e9bedf8c7a4c4a79a644a6e1857ee4"></a>
 </td><td class="memItemRight" valign="bottom"><b>QUICKCPPLIB_BITFIELD_END</b> (flag)</td></tr>
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<tr class="memitem:a00a85eec5a41f7edb2c574d40cf04535"><td class="memItemLeft" align="right" valign="top">virtual result< path_type > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a00a85eec5a41f7edb2c574d40cf04535">current_path</a> () const noexcept</td></tr>
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<tr class="memitem:a1d273e38c061eb11f5012f624e9a202e"><td class="memItemLeft" align="right" valign="top"><a id="a1d273e38c061eb11f5012f624e9a202e"></a>
virtual <a class="el" href="structllfio__v2__xxx_1_1native__handle__type.html">native_handle_type</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a1d273e38c061eb11f5012f624e9a202e">release</a> () noexcept</td></tr>
<tr class="memdesc:a1d273e38c061eb11f5012f624e9a202e"><td class="mdescLeft"> </td><td class="mdescRight">Release the native handle type managed by this handle. <br /></td></tr>
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<tr class="memitem:a5c7f6a0a8ffdea22763c75a9319ba0c2"><td class="memItemLeft" align="right" valign="top"><a id="a5c7f6a0a8ffdea22763c75a9319ba0c2"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a5c7f6a0a8ffdea22763c75a9319ba0c2">is_valid</a> () const noexcept</td></tr>
<tr class="memdesc:a5c7f6a0a8ffdea22763c75a9319ba0c2"><td class="mdescLeft"> </td><td class="mdescRight">True if the handle is valid (and usually open) <br /></td></tr>
<tr class="separator:a5c7f6a0a8ffdea22763c75a9319ba0c2"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a97e0884c27147b4929be98961b8e9254"><td class="memItemLeft" align="right" valign="top"><a id="a97e0884c27147b4929be98961b8e9254"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a97e0884c27147b4929be98961b8e9254">is_readable</a> () const noexcept</td></tr>
<tr class="memdesc:a97e0884c27147b4929be98961b8e9254"><td class="mdescLeft"> </td><td class="mdescRight">True if the handle is readable. <br /></td></tr>
<tr class="separator:a97e0884c27147b4929be98961b8e9254"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a211fee447a47bdeb5424a2a5ae1de852"><td class="memItemLeft" align="right" valign="top"><a id="a211fee447a47bdeb5424a2a5ae1de852"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a211fee447a47bdeb5424a2a5ae1de852">is_writable</a> () const noexcept</td></tr>
<tr class="memdesc:a211fee447a47bdeb5424a2a5ae1de852"><td class="mdescLeft"> </td><td class="mdescRight">True if the handle is writable. <br /></td></tr>
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<tr class="memitem:ac3aa3dc009822c0e437f317864534feb"><td class="memItemLeft" align="right" valign="top"><a id="ac3aa3dc009822c0e437f317864534feb"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#ac3aa3dc009822c0e437f317864534feb">is_append_only</a> () const noexcept</td></tr>
<tr class="memdesc:ac3aa3dc009822c0e437f317864534feb"><td class="mdescLeft"> </td><td class="mdescRight">True if the handle is append only. <br /></td></tr>
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<tr class="memitem:a101620e9fff0c0e8c346af0e9de58b6a"><td class="memItemLeft" align="right" valign="top">virtual result< void > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a101620e9fff0c0e8c346af0e9de58b6a">set_append_only</a> (bool enable) noexcept</td></tr>
<tr class="memdesc:a101620e9fff0c0e8c346af0e9de58b6a"><td class="mdescLeft"> </td><td class="mdescRight">EXTENSION: Changes whether this handle is append only or not. <a href="#a101620e9fff0c0e8c346af0e9de58b6a">More...</a><br /></td></tr>
<tr class="separator:a101620e9fff0c0e8c346af0e9de58b6a"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a8085cb3b40982c6dbd874547c183fd5e"><td class="memItemLeft" align="right" valign="top"><a id="a8085cb3b40982c6dbd874547c183fd5e"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a8085cb3b40982c6dbd874547c183fd5e">is_overlapped</a> () const noexcept</td></tr>
<tr class="memdesc:a8085cb3b40982c6dbd874547c183fd5e"><td class="mdescLeft"> </td><td class="mdescRight">True if overlapped. <br /></td></tr>
<tr class="separator:a8085cb3b40982c6dbd874547c183fd5e"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a695ce0ed1606d540cfa452790ea71632"><td class="memItemLeft" align="right" valign="top"><a id="a695ce0ed1606d540cfa452790ea71632"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a695ce0ed1606d540cfa452790ea71632">is_seekable</a> () const noexcept</td></tr>
<tr class="memdesc:a695ce0ed1606d540cfa452790ea71632"><td class="mdescLeft"> </td><td class="mdescRight">True if seekable. <br /></td></tr>
<tr class="separator:a695ce0ed1606d540cfa452790ea71632"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a751e912d8dab755ea969a418c1d544eb"><td class="memItemLeft" align="right" valign="top"><a id="a751e912d8dab755ea969a418c1d544eb"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a751e912d8dab755ea969a418c1d544eb">requires_aligned_io</a> () const noexcept</td></tr>
<tr class="memdesc:a751e912d8dab755ea969a418c1d544eb"><td class="mdescLeft"> </td><td class="mdescRight">True if requires aligned i/o. <br /></td></tr>
<tr class="separator:a751e912d8dab755ea969a418c1d544eb"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a7751fbb4b1aff527f469412ea33116ed"><td class="memItemLeft" align="right" valign="top"><a id="a7751fbb4b1aff527f469412ea33116ed"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a7751fbb4b1aff527f469412ea33116ed">is_regular</a> () const noexcept</td></tr>
<tr class="memdesc:a7751fbb4b1aff527f469412ea33116ed"><td class="mdescLeft"> </td><td class="mdescRight">True if a regular file or device. <br /></td></tr>
<tr class="separator:a7751fbb4b1aff527f469412ea33116ed"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a4ca48bdcd6d6bf8b41d0cebb304fe9ce"><td class="memItemLeft" align="right" valign="top"><a id="a4ca48bdcd6d6bf8b41d0cebb304fe9ce"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a4ca48bdcd6d6bf8b41d0cebb304fe9ce">is_directory</a> () const noexcept</td></tr>
<tr class="memdesc:a4ca48bdcd6d6bf8b41d0cebb304fe9ce"><td class="mdescLeft"> </td><td class="mdescRight">True if a directory. <br /></td></tr>
<tr class="separator:a4ca48bdcd6d6bf8b41d0cebb304fe9ce"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ae0d5de068f71628e9491c5669f89dca0"><td class="memItemLeft" align="right" valign="top"><a id="ae0d5de068f71628e9491c5669f89dca0"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#ae0d5de068f71628e9491c5669f89dca0">is_symlink</a> () const noexcept</td></tr>
<tr class="memdesc:ae0d5de068f71628e9491c5669f89dca0"><td class="mdescLeft"> </td><td class="mdescRight">True if a symlink. <br /></td></tr>
<tr class="separator:ae0d5de068f71628e9491c5669f89dca0"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a018de0f7c177e3cff239016d14582e9a"><td class="memItemLeft" align="right" valign="top"><a id="a018de0f7c177e3cff239016d14582e9a"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a018de0f7c177e3cff239016d14582e9a">is_multiplexer</a> () const noexcept</td></tr>
<tr class="memdesc:a018de0f7c177e3cff239016d14582e9a"><td class="mdescLeft"> </td><td class="mdescRight">True if a multiplexer like BSD kqueues, Linux epoll or Windows IOCP. <br /></td></tr>
<tr class="separator:a018de0f7c177e3cff239016d14582e9a"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ade0d0e05b844e77f425669da87bf48bb"><td class="memItemLeft" align="right" valign="top"><a id="ade0d0e05b844e77f425669da87bf48bb"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#ade0d0e05b844e77f425669da87bf48bb">is_process</a> () const noexcept</td></tr>
<tr class="memdesc:ade0d0e05b844e77f425669da87bf48bb"><td class="mdescLeft"> </td><td class="mdescRight">True if a process. <br /></td></tr>
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<tr class="memitem:a354c9168af7759f7151a071c1e1b7b19"><td class="memItemLeft" align="right" valign="top"><a id="a354c9168af7759f7151a071c1e1b7b19"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a354c9168af7759f7151a071c1e1b7b19">is_section</a> () const noexcept</td></tr>
<tr class="memdesc:a354c9168af7759f7151a071c1e1b7b19"><td class="mdescLeft"> </td><td class="mdescRight">True if a memory section. <br /></td></tr>
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<tr class="memitem:a90bf8668df002dac5a7d9397486b2946"><td class="memItemLeft" align="right" valign="top"><a id="a90bf8668df002dac5a7d9397486b2946"></a>
<a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a90bf8668df002dac5a7d9397486b2946">kernel_caching</a> () const noexcept</td></tr>
<tr class="memdesc:a90bf8668df002dac5a7d9397486b2946"><td class="mdescLeft"> </td><td class="mdescRight">Kernel cache strategy used by this handle. <br /></td></tr>
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<tr class="memitem:a7126a726b2a06e4c1eca1a94c41163ff"><td class="memItemLeft" align="right" valign="top"><a id="a7126a726b2a06e4c1eca1a94c41163ff"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a7126a726b2a06e4c1eca1a94c41163ff">are_reads_from_cache</a> () const noexcept</td></tr>
<tr class="memdesc:a7126a726b2a06e4c1eca1a94c41163ff"><td class="mdescLeft"> </td><td class="mdescRight">True if the handle uses the kernel page cache for reads. <br /></td></tr>
<tr class="separator:a7126a726b2a06e4c1eca1a94c41163ff"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a8036792f332459064172d7b0cfaee3cf"><td class="memItemLeft" align="right" valign="top"><a id="a8036792f332459064172d7b0cfaee3cf"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a8036792f332459064172d7b0cfaee3cf">are_writes_durable</a> () const noexcept</td></tr>
<tr class="memdesc:a8036792f332459064172d7b0cfaee3cf"><td class="mdescLeft"> </td><td class="mdescRight">True if writes are safely on storage on completion. <br /></td></tr>
<tr class="separator:a8036792f332459064172d7b0cfaee3cf"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a0a2a5896f5e373fa032cdae1c1fff2c1"><td class="memItemLeft" align="right" valign="top"><a id="a0a2a5896f5e373fa032cdae1c1fff2c1"></a>
bool </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a0a2a5896f5e373fa032cdae1c1fff2c1">are_safety_barriers_issued</a> () const noexcept</td></tr>
<tr class="memdesc:a0a2a5896f5e373fa032cdae1c1fff2c1"><td class="mdescLeft"> </td><td class="mdescRight">True if issuing safety fsyncs is on. <br /></td></tr>
<tr class="separator:a0a2a5896f5e373fa032cdae1c1fff2c1"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a013936bc1254b1a47567fe29698d1b1c"><td class="memItemLeft" align="right" valign="top"><a id="a013936bc1254b1a47567fe29698d1b1c"></a>
flag </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">flags</a> () const noexcept</td></tr>
<tr class="memdesc:a013936bc1254b1a47567fe29698d1b1c"><td class="mdescLeft"> </td><td class="mdescRight">The flags this handle was opened with. <br /></td></tr>
<tr class="separator:a013936bc1254b1a47567fe29698d1b1c"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a942b0d276c9f20fe41baab679b88fe72"><td class="memItemLeft" align="right" valign="top"><a id="a942b0d276c9f20fe41baab679b88fe72"></a>
<a class="el" href="structllfio__v2__xxx_1_1native__handle__type.html">native_handle_type</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a942b0d276c9f20fe41baab679b88fe72">native_handle</a> () const noexcept</td></tr>
<tr class="memdesc:a942b0d276c9f20fe41baab679b88fe72"><td class="mdescLeft"> </td><td class="mdescRight">The native handle used by this handle. <br /></td></tr>
<tr class="separator:a942b0d276c9f20fe41baab679b88fe72"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ac24ed4cdb96690d7da95cd17b0f3d090"><td class="memItemLeft" align="right" valign="top"><a id="ac24ed4cdb96690d7da95cd17b0f3d090"></a>
dev_t </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#ac24ed4cdb96690d7da95cd17b0f3d090">st_dev</a> () const noexcept</td></tr>
<tr class="memdesc:ac24ed4cdb96690d7da95cd17b0f3d090"><td class="mdescLeft"> </td><td class="mdescRight">Unless <code>flag::disable_safety_unlinks</code> is set, the device id of the file when opened. <br /></td></tr>
<tr class="separator:ac24ed4cdb96690d7da95cd17b0f3d090"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:aad6465d30ee438b860ccc59c0e0fc4dc"><td class="memItemLeft" align="right" valign="top"><a id="aad6465d30ee438b860ccc59c0e0fc4dc"></a>
ino_t </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#aad6465d30ee438b860ccc59c0e0fc4dc">st_ino</a> () const noexcept</td></tr>
<tr class="memdesc:aad6465d30ee438b860ccc59c0e0fc4dc"><td class="mdescLeft"> </td><td class="mdescRight">Unless <code>flag::disable_safety_unlinks</code> is set, the inode of the file when opened. When combined with st_dev(), forms a unique identifer on this system. <br /></td></tr>
<tr class="separator:aad6465d30ee438b860ccc59c0e0fc4dc"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a9793fe40564fda2437783488bd51b9f1"><td class="memItemLeft" align="right" valign="top"><a id="a9793fe40564fda2437783488bd51b9f1"></a>
<a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#a1a65884346740af7fb4648c79d44a750">unique_id_type</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#a9793fe40564fda2437783488bd51b9f1">unique_id</a> () const noexcept</td></tr>
<tr class="memdesc:a9793fe40564fda2437783488bd51b9f1"><td class="mdescLeft"> </td><td class="mdescRight">A unique identifier for this handle across the entire system. Can be used in hash tables etc. <br /></td></tr>
<tr class="separator:a9793fe40564fda2437783488bd51b9f1"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a865caad2f7f4bdf12fb74aabfe3c5ff5"><td class="memItemLeft" align="right" valign="top">virtual result< <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#a865caad2f7f4bdf12fb74aabfe3c5ff5">parent_path_handle</a> (<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=std::chrono::seconds(30)) const noexcept</td></tr>
<tr class="separator:a865caad2f7f4bdf12fb74aabfe3c5ff5"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a8700edc9ecd4dd35d5aad7c65dd0eca2"><td class="memItemLeft" align="right" valign="top">virtual result< void > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#a8700edc9ecd4dd35d5aad7c65dd0eca2">relink</a> (const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> &base, <a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view_type</a> <a class="el" href="namespacellfio__v2__xxx.html#a49f7bb77eb38fbe1280019225b66b78b">path</a>, bool atomic_replace=true, <a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=std::chrono::seconds(30)) noexcept</td></tr>
<tr class="separator:a8700edc9ecd4dd35d5aad7c65dd0eca2"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a1dd7923bb65456af4da41ebe7cb84982"><td class="memItemLeft" align="right" valign="top">virtual result< void > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#a1dd7923bb65456af4da41ebe7cb84982">unlink</a> (<a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> d=std::chrono::seconds(30)) noexcept</td></tr>
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</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-static-methods"></a>
Static Public Member Functions</h2></td></tr>
<tr class="memitem:ad7a9a1810c10a5b34c1134d942cfa1c1"><td class="memItemLeft" align="right" valign="top">static result< <a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#ad7a9a1810c10a5b34c1134d942cfa1c1">fast_random_file</a> (extent_type bytes=(extent_type) -1, <a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> _mode=<a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaecae13117d6f0584c25a9da6c8f8415e">mode::read</a>, span< const byte > seed={}) noexcept</td></tr>
<tr class="separator:ad7a9a1810c10a5b34c1134d942cfa1c1"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a09e6b3e9806b328a687a55e955b885a3"><td class="memItemLeft" align="right" valign="top">static result< <a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a09e6b3e9806b328a687a55e955b885a3">file</a> (const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> &base, <a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view_type</a> <a class="el" href="namespacellfio__v2__xxx.html#a49f7bb77eb38fbe1280019225b66b78b">path</a>, <a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> _mode=<a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaecae13117d6f0584c25a9da6c8f8415e">mode::read</a>, <a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42">creation</a> _creation=<a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42aa200dcd6176417e93be2405188ae7cc9">creation::open_existing</a>, <a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> _caching=<a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852aa181a603769c1f98ad927e7367c7aa51">caching::all</a>, flag <a class="el" href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">flags</a>=flag::none) noexcept</td></tr>
<tr class="separator:a09e6b3e9806b328a687a55e955b885a3"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a3141a85996e46a3cc6b238d321198e47"><td class="memItemLeft" align="right" valign="top">static result< <a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a3141a85996e46a3cc6b238d321198e47">random_file</a> (const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> &dirpath, <a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> _mode=<a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee">mode::write</a>, <a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> _caching=<a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852ad5197d93c063a2b1e22d1630a39b7aef">caching::temporary</a>, flag <a class="el" href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">flags</a>=flag::none) noexcept</td></tr>
<tr class="separator:a3141a85996e46a3cc6b238d321198e47"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a428114e3c8628c0621b1aa156051651c"><td class="memItemLeft" align="right" valign="top">static result< <a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a428114e3c8628c0621b1aa156051651c">temp_file</a> (<a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view_type</a> name=<a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view_type</a>(), <a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> _mode=<a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee">mode::write</a>, <a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42">creation</a> _creation=<a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42a8f0339e854eb5321306a443ce9199e1d">creation::if_needed</a>, <a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> _caching=<a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852ad5197d93c063a2b1e22d1630a39b7aef">caching::temporary</a>, flag <a class="el" href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">flags</a>=flag::unlink_on_first_close) noexcept</td></tr>
<tr class="separator:a428114e3c8628c0621b1aa156051651c"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a1eff21e1833be0c21f72477c593fadc5"><td class="memItemLeft" align="right" valign="top">static result< <a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a> > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a1eff21e1833be0c21f72477c593fadc5">temp_inode</a> (const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> &dirh=<a class="el" href="namespacellfio__v2__xxx_1_1path__discovery.html#a2dd74ea752f3f511d58ccccdcac7f4fd">path_discovery::storage_backed_temporary_files_directory</a>(), <a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> _mode=<a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee">mode::write</a>, flag <a class="el" href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">flags</a>=flag::none) noexcept</td></tr>
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</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pro-methods"></a>
Protected Member Functions</h2></td></tr>
<tr class="memitem:a6d7f0bf0df9384635111f23bd63d1792"><td class="memItemLeft" align="right" valign="top"><a id="a6d7f0bf0df9384635111f23bd63d1792"></a>
result< void > </td><td class="memItemRight" valign="bottom"><b>_perms_check</b> () const noexcept</td></tr>
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<tr class="memitem:adc2b24484565bcb0cf654adf2f732f7e"><td class="memItemLeft" align="right" valign="top"><a id="adc2b24484565bcb0cf654adf2f732f7e"></a>
result< void > </td><td class="memItemRight" valign="bottom"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#adc2b24484565bcb0cf654adf2f732f7e">_fetch_inode</a> () const noexcept</td></tr>
<tr class="memdesc:adc2b24484565bcb0cf654adf2f732f7e"><td class="mdescLeft"> </td><td class="mdescRight">Fill in _devid and _inode from the handle via fstat() <br /></td></tr>
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</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pro-attribs"></a>
Protected Attributes</h2></td></tr>
<tr class="memitem:a81a7ae5e213b40fdece1f76430eea161"><td class="memItemLeft" align="right" valign="top"><a id="a81a7ae5e213b40fdece1f76430eea161"></a>
<a class="el" href="structllfio__v2__xxx_1_1fast__random__file__handle_1_1prng.html">llfio_v2_xxx::fast_random_file_handle::prng</a> </td><td class="memItemRight" valign="bottom"><b>_prng</b></td></tr>
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extent_type </td><td class="memItemRight" valign="bottom"><b>_length</b> {0}</td></tr>
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<tr class="memitem:aa2c2b2847fd039b9c255633e6031817a"><td class="memItemLeft" align="right" valign="top"><a id="aa2c2b2847fd039b9c255633e6031817a"></a>
<a class="el" href="classllfio__v2__xxx_1_1io__service.html">io_service</a> * </td><td class="memItemRight" valign="bottom"><b>_service</b> {nullptr}</td></tr>
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<tr class="memitem:affb091ded80ffde7c0c3854e2abc52fd"><td class="memItemLeft" align="right" valign="top"><a id="affb091ded80ffde7c0c3854e2abc52fd"></a>
<a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> </td><td class="memItemRight" valign="bottom"><b>_caching</b> {<a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852a334c4a4c42fdb79d7ebc3e73b517e6f8">caching::none</a>}</td></tr>
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<tr class="memitem:ad758cf1eb2e0b4c63583eab05e7f6820"><td class="memItemLeft" align="right" valign="top"><a id="ad758cf1eb2e0b4c63583eab05e7f6820"></a>
flag </td><td class="memItemRight" valign="bottom"><b>_flags</b> {flag::none}</td></tr>
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<a class="el" href="structllfio__v2__xxx_1_1native__handle__type.html">native_handle_type</a> </td><td class="memItemRight" valign="bottom"><b>_v</b></td></tr>
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<tr class="memitem:a4d20a64cf182162a49962ed25d2126b3"><td class="memItemLeft" align="right" valign="top"><a id="a4d20a64cf182162a49962ed25d2126b3"></a>
dev_t </td><td class="memItemRight" valign="bottom"><b>_devid</b> {0}</td></tr>
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<tr class="memitem:a8454764db3cd47e65ec7853b9cb0b3fa"><td class="memItemLeft" align="right" valign="top"><a id="a8454764db3cd47e65ec7853b9cb0b3fa"></a>
ino_t </td><td class="memItemRight" valign="bottom"><b>_inode</b> {0}</td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>A handle to synthesised, non-cryptographic, pseudo-random data. </p>
<p>This implementation of file handle provides read-only file data of random bits based on Bob Jenkins' 32-bit JSF PRNG (<a href="http://burtleburtle.net/bob/rand/smallprng.html">http://burtleburtle.net/bob/rand/smallprng.html</a>). It works by initialising the prng state from the seed you provide at construction, and then for each 4 byte block it copies the 16 bytes of prng state, overwrites the first eight bytes with the offset divided by 4, and performs a PRNG round to generate a fairly unique number. As there are eight bytes of randomness being mixed with eight bytes of counter, this will not be a particularly random stream, but it's probably not awful either.</p>
<p>Note that writes to this handle are permitted if it was opened with write permission, but writes have no effect.</p>
<p>The use for a file handle full of random data may not be obvious. The first is to obfuscate another file's data using <code>algorithm::xor_handle_adapter</code>. The second is for mock ups in testing, where this file handle stands in for some other (large) file, and you are testing throughput or latency in processing code.</p>
<p>The third is for unit testing randomly corrupted file data. <code>algorithm::mix_handle_adapter</code> can randomly mix scatter gather buffers from this file handle into another file handle in order to test how well handling code copes with random data corruption.</p>
<h2>Benchmarks:</h2>
<p>On a 3.1Ghz Intel Skylake CPU where <code>memcpy()</code> can do ~12Gb/sec:</p>
<ul>
<li>GCC7: 4659 Mb/sec</li>
<li>VS2017: 3653 Mb/sec</li>
</ul>
<p>The current implementation spots when it can do 16x simultaneous PRNG rounds, and thus can fill a cache line at a time. The Skylake CPU used to benchmark the code dispatches around four times the throughput with this, however there is likely still performance left on the table.</p>
<p>If someone were bothered to rewrite the JSF PRNG into SIMD, it is possible one could approach <code>memcpy()</code> in performance. One would probably need to use AVX-512 however, as the JSF PRNG makes heavy use of bit rotation, which is slow before AVX-512 as it must be emulated with copious bit shifting and masking. </p>
</div><h2 class="groupheader">Member Enumeration Documentation</h2>
<a id="a7816bb7ae5156fa2997b68e6300ae565"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a7816bb7ae5156fa2997b68e6300ae565">◆ </a></span>barrier_kind</h2>
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<td class="memname">enum <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565">llfio_v2_xxx::io_handle::barrier_kind</a></td>
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<span class="mlabels"><span class="mlabel">strong</span><span class="mlabel">inherited</span></span> </td>
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<p>The kinds of write reordering barrier which can be performed. </p>
<table class="fieldtable">
<tr><th colspan="2">Enumerator</th></tr><tr><td class="fieldname"><a id="a7816bb7ae5156fa2997b68e6300ae565a2f6648dac37731813bb84ae9b24bdfdb"></a>nowait_data_only </td><td class="fielddoc"><p>Barrier data only, non-blocking. This is highly optimised on NV-DIMM storage, but consider using <code>nvram_barrier()</code> for even better performance. </p>
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<tr><td class="fieldname"><a id="a7816bb7ae5156fa2997b68e6300ae565af1d3baf03681db9a9986e0a76d6107ce"></a>wait_data_only </td><td class="fielddoc"><p>Barrier data only, block until it is done. This is highly optimised on NV-DIMM storage, but consider using <code>nvram_barrier()</code> for even better performance. </p>
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<tr><td class="fieldname"><a id="a7816bb7ae5156fa2997b68e6300ae565ab7a52d26120f585b21e8960812db5bf1"></a>nowait_all </td><td class="fielddoc"><p>Barrier data and the metadata to retrieve it, non-blocking. </p>
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<tr><td class="fieldname"><a id="a7816bb7ae5156fa2997b68e6300ae565a4e1789381cf8c976ec7a7118b3529345"></a>wait_all </td><td class="fielddoc"><p>Barrier data and the metadata to retrieve it, block until it is done. </p>
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<div class="fragment"><div class="line"><a name="l00055"></a><span class="lineno"> 55</span>  {</div><div class="line"><a name="l00056"></a><span class="lineno"> 56</span>  nowait_data_only, <span class="comment">//!< Barrier data only, non-blocking. This is highly optimised on NV-DIMM storage, but consider using `nvram_barrier()` for even better performance.</span></div><div class="line"><a name="l00057"></a><span class="lineno"> 57</span> <span class="comment"></span> wait_data_only, <span class="comment">//!< Barrier data only, block until it is done. This is highly optimised on NV-DIMM storage, but consider using `nvram_barrier()` for even better performance.</span></div><div class="line"><a name="l00058"></a><span class="lineno"> 58</span> <span class="comment"></span> nowait_all, <span class="comment">//!< Barrier data and the metadata to retrieve it, non-blocking.</span></div><div class="line"><a name="l00059"></a><span class="lineno"> 59</span> <span class="comment"></span> wait_all <span class="comment">//!< Barrier data and the metadata to retrieve it, block until it is done.</span></div><div class="line"><a name="l00060"></a><span class="lineno"> 60</span> <span class="comment"></span> };</div></div><!-- fragment -->
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<h2 class="memtitle"><span class="permalink"><a href="#aa25e3ab298152166fc387d8fcfb19a63">◆ </a></span>lock_kind</h2>
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<td class="memname">enum <a class="el" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63">llfio_v2_xxx::file_handle::lock_kind</a></td>
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<span class="mlabels"><span class="mlabel">strong</span><span class="mlabel">inherited</span></span> </td>
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<p>The kinds of concurrent user exclusion which can be performed. </p>
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<tr><th colspan="2">Enumerator</th></tr><tr><td class="fieldname"><a id="aa25e3ab298152166fc387d8fcfb19a63a9e81e7b963c71363e2fb3eefcfecfc0e"></a>shared </td><td class="fielddoc"><p>Exclude only those requesting an exclusive lock on the same inode. </p>
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<tr><td class="fieldname"><a id="aa25e3ab298152166fc387d8fcfb19a63aa4293995cfbfa9ce60ce71ade2ff75f7"></a>exclusive </td><td class="fielddoc"><p>Exclude those requesting any kind of lock on the same inode. </p>
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<div class="fragment"><div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  {</div><div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  unknown,</div><div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  shared, <span class="comment">//!< Exclude only those requesting an exclusive lock on the same inode.</span></div><div class="line"><a name="l00082"></a><span class="lineno"> 82</span> <span class="comment"></span> exclusive <span class="comment">//!< Exclude those requesting any kind of lock on the same inode.</span></div><div class="line"><a name="l00083"></a><span class="lineno"> 83</span> <span class="comment"></span> };</div></div><!-- fragment -->
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<h2 class="groupheader">Member Function Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a823391cea8818da742c0d4c573f7300f">◆ </a></span>barrier()</h2>
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<td class="memname">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a><const_buffers_type> llfio_v2_xxx::io_handle::barrier </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a693a8c64bb7de1a6835d6a151e37aa0e">const_buffers_type</a> > </td>
<td class="paramname"><em>reqs</em> = <code><a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a693a8c64bb7de1a6835d6a151e37aa0e">const_buffers_type</a> >()</code>, </td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565">barrier_kind</a> </td>
<td class="paramname"><em>kind</em> = <code><a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a7816bb7ae5156fa2997b68e6300ae565a2f6648dac37731813bb84ae9b24bdfdb">barrier_kind::nowait_data_only</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><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()</code> </td>
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<td>)</td>
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<span class="mlabels"><span class="mlabel">pure virtual</span><span class="mlabel">noexcept</span><span class="mlabel">inherited</span></span> </td>
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<p>Issue a write reordering barrier such that writes preceding the barrier will reach storage before writes after this barrier. </p>
<dl class="section warning"><dt>Warning</dt><dd><b>Assume that this call is a no-op</b>. It is not reliably implemented in many common use cases, for example if your code is running inside a LXC container, or if the user has mounted the filing system with non-default options. Instead open the handle with <code>caching::reads</code> which means that all writes form a strict sequential order not completing until acknowledged by the storage device. Filing system can and do use different algorithms to give much better performance with <code>caching::reads</code>, some (e.g. ZFS) spectacularly better.</dd>
<dd>
Let me repeat again: consider this call to be a <b>hint</b> to poke the kernel with a stick to go start to do some work sooner rather than later. <b>It may be ignored entirely</b>.</dd>
<dd>
For portability, you can only assume that barriers write order for a single handle instance. You cannot assume that barriers write order across multiple handles to the same inode, or across processes.</dd></dl>
<dl class="section return"><dt>Returns</dt><dd>The buffers barriered, which may not be the buffers input. The size of each scatter-gather buffer is updated with the number of bytes of that buffer barriered. </dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">reqs</td><td>A scatter-gather and offset request for what range to barrier. May be ignored on some platforms which always write barrier the entire file. Supplying a default initialised reqs write barriers the entire file. </td></tr>
<tr><td class="paramname">kind</td><td>Which kind of write reordering barrier to perform. </td></tr>
<tr><td class="paramname">d</td><td>An optional deadline by which the i/o must complete, else it is cancelled. Note function may return significantly after this deadline if the i/o takes long to cancel. </td></tr>
</table>
</dd>
</dl>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX fdatasync() or Windows NtFlushBuffersFileEx() can return. </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>None. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#a6b97756d8d46e80da7d0fa04158a71a8">◆ </a></span>clone() <span class="overload">[1/2]</span></h2>
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<td class="memname">result<<a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a>> llfio_v2_xxx::file_handle::clone </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> </td>
<td class="paramname"><em>mode_</em> = <code>mode::unchanged</code>, </td>
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<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> </td>
<td class="paramname"><em>caching_</em> = <code>caching::unchanged</code>, </td>
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<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> </td>
<td class="paramname"><em>d</em> = <code>std::chrono::seconds(30)</code> </td>
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<td></td>
<td>)</td>
<td></td><td> const</td>
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<span class="mlabels"><span class="mlabel">noexcept</span><span class="mlabel">inherited</span></span> </td>
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<p>Clone this handle (copy constructor is disabled to avoid accidental copying), optionally race free reopening the handle with different access or caching.</p>
<p>Microsoft Windows provides a syscall for cloning an existing handle but with new access. On POSIX, if not changing the mode, we change caching via <code>fcntl()</code>, if changing the mode we must loop calling <code>current_path()</code>, trying to open the path returned and making sure it is the same inode.</p>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX dup() or DuplicateHandle() can return. </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>On POSIX if changing the mode, we must loop calling <code>current_path()</code> and trying to open the path returned. Thus many allocations may occur. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#aeea4389189021b94dde6d8f2c3ccc5b3">◆ </a></span>clone() <span class="overload">[2/2]</span></h2>
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<td class="memname">result<<a class="el" href="classllfio__v2__xxx_1_1handle.html">handle</a>> llfio_v2_xxx::handle::clone </td>
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<p>Clone this handle (copy constructor is disabled to avoid accidental copying)</p>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX dup() or DuplicateHandle() can return. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#a00a85eec5a41f7edb2c574d40cf04535">◆ </a></span>current_path()</h2>
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<td class="memname">virtual result<path_type> llfio_v2_xxx::handle::current_path </td>
<td>(</td>
<td class="paramname"></td><td>)</td>
<td> const</td>
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<p>Returns the current path of the open handle as said by the operating system. Note that you are NOT guaranteed that any path refreshed bears any resemblance to the original, some operating systems will return some different path which still reaches the same inode via some other route e.g. hardlinks, dereferenced symbolic links, etc. Windows and Linux correctly track changes to the specific path the handle was opened with, not getting confused by other hard links. MacOS nearly gets it right, but under some circumstances e.g. renaming may switch to a different hard link's path which is almost certainly a bug.</p>
<p>If LLFIO was not able to determine the current path for this open handle e.g. the inode has been unlinked, it returns an empty path. Be aware that FreeBSD can return an empty (deleted) path for file inodes no longer cached by the kernel path cache, LLFIO cannot detect the difference. FreeBSD will also return any path leading to the inode if it is hard linked. FreeBSD does implement path retrieval for directory inodes correctly however, and see <code>algorithm::cached_parent_handle_adapter<T></code> for a handle adapter which makes use of that.</p>
<p>On Linux if <code>/proc</code> is not mounted, this call fails with an error. All APIs in LLFIO which require the use of <code>current_path()</code> can be told to not use it e.g. <code>flag::disable_safety_unlinks</code>. It is up to you to detect if <code>current_path()</code> is not working, and to change how you call LLFIO appropriately.</p>
<dl class="section warning"><dt>Warning</dt><dd>This call is expensive, it always asks the kernel for the current path, and no checking is done to ensure what the kernel returns is accurate or even sensible. Be aware that despite these precautions, paths are unstable and <b>can change randomly at any moment</b>. Most code written to use absolute file systems paths is <b>racy</b>, so don't do it, use <code>path_handle</code> to fix a base location on the file system and work from that anchor instead!</dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>At least one malloc for the <code>path_type</code>, likely several more. </dd></dl>
<dl class="section see"><dt>See also</dt><dd><code>algorithm::cached_parent_handle_adapter<T></code> which overrides this with an implementation based on retrieving the current path of a cached handle to the parent directory. On platforms with instability or failure to retrieve the correct current path for regular files, the cached parent handle adapter works around the problem by taking advantage of directory inodes not having the same instability problems on any platform. </dd></dl>
<p>Reimplemented in <a class="el" href="classllfio__v2__xxx_1_1symlink__handle.html#aea44ed050acfd8e4f9dec59ff194c746">llfio_v2_xxx::symlink_handle</a>.</p>
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<h2 class="memtitle"><span class="permalink"><a href="#ad7a9a1810c10a5b34c1134d942cfa1c1">◆ </a></span>fast_random_file()</h2>
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<td class="memname">static result<<a class="el" href="classllfio__v2__xxx_1_1fast__random__file__handle.html">fast_random_file_handle</a>> llfio_v2_xxx::fast_random_file_handle::fast_random_file </td>
<td>(</td>
<td class="paramtype">extent_type </td>
<td class="paramname"><em>bytes</em> = <code>(extent_type) -1</code>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> </td>
<td class="paramname"><em>_mode</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaecae13117d6f0584c25a9da6c8f8415e">mode::read</a></code>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">span< const byte > </td>
<td class="paramname"><em>seed</em> = <code>{}</code> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
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<p>Create a random file handle. </p><dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">bytes</td><td>How long the random file ought to report itself being. </td></tr>
<tr><td class="paramname">_mode</td><td>How to open the file. </td></tr>
<tr><td class="paramname">seed</td><td>Up to 88 bytes with which to seed the randomness. The default means use <code>utils::random_fill()</code>. </td></tr>
</table>
</dd>
</dl>
<div class="fragment"><div class="line"><a name="l00173"></a><span class="lineno"> 173</span>  {}) noexcept</div><div class="line"><a name="l00174"></a><span class="lineno"> 174</span>  {</div><div class="line"><a name="l00175"></a><span class="lineno"> 175</span>  <span class="keywordflow">if</span>(_mode == <a class="code" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaa9516dfb15f51c7ee19a4d46b8c0dbe1d">mode::append</a>)</div><div class="line"><a name="l00176"></a><span class="lineno"> 176</span>  {</div><div class="line"><a name="l00177"></a><span class="lineno"> 177</span>  <span class="keywordflow">return</span> errc::invalid_argument;</div><div class="line"><a name="l00178"></a><span class="lineno"> 178</span>  }</div><div class="line"><a name="l00179"></a><span class="lineno"> 179</span>  byte _seed[16];</div><div class="line"><a name="l00180"></a><span class="lineno"> 180</span>  <span class="keywordflow">if</span>(seed.empty())</div><div class="line"><a name="l00181"></a><span class="lineno"> 181</span>  {</div><div class="line"><a name="l00182"></a><span class="lineno"> 182</span>  <a class="code" href="namespacellfio__v2__xxx_1_1utils.html#ae61e2de30b06776a1c24643a1d1dc64e">utils::random_fill</a>((<span class="keywordtype">char</span> *) _seed, <span class="keyword">sizeof</span>(_seed));</div><div class="line"><a name="l00183"></a><span class="lineno"> 183</span>  seed = _seed;</div><div class="line"><a name="l00184"></a><span class="lineno"> 184</span>  }</div><div class="line"><a name="l00185"></a><span class="lineno"> 185</span>  result<fast_random_file_handle> ret(<a class="code" href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a4661a9c1551d33d054ccd80599806ba7">fast_random_file_handle</a>(bytes, seed));</div><div class="line"><a name="l00186"></a><span class="lineno"> 186</span>  native_handle_type &nativeh = ret.value()._v;</div><div class="line"><a name="l00187"></a><span class="lineno"> 187</span>  LLFIO_LOG_FUNCTION_CALL(&ret);</div><div class="line"><a name="l00188"></a><span class="lineno"> 188</span>  nativeh.behaviour |= <a class="code" href="namespacellfio__v2__xxx.html#af31a062639499a79ef5cc8aed16ba65d">native_handle_type::disposition::file</a>;</div><div class="line"><a name="l00189"></a><span class="lineno"> 189</span>  nativeh.behaviour |= native_handle_type::disposition::seekable | native_handle_type::disposition::readable;</div><div class="line"><a name="l00190"></a><span class="lineno"> 190</span>  <span class="keywordflow">if</span>(_mode == <a class="code" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee">mode::write</a>)</div><div class="line"><a name="l00191"></a><span class="lineno"> 191</span>  {</div><div class="line"><a name="l00192"></a><span class="lineno"> 192</span>  nativeh.behaviour |= native_handle_type::disposition::writable;</div><div class="line"><a name="l00193"></a><span class="lineno"> 193</span>  }</div><div class="line"><a name="l00194"></a><span class="lineno"> 194</span>  <span class="keywordflow">return</span> ret;</div><div class="line"><a name="l00195"></a><span class="lineno"> 195</span>  }</div><div class="ttc" id="classllfio__v2__xxx_1_1fast__random__file__handle_html_a4661a9c1551d33d054ccd80599806ba7"><div class="ttname"><a href="classllfio__v2__xxx_1_1fast__random__file__handle.html#a4661a9c1551d33d054ccd80599806ba7">llfio_v2_xxx::fast_random_file_handle::fast_random_file_handle</a></div><div class="ttdeci">fast_random_file_handle()=default</div><div class="ttdoc">Default constructor. </div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1handle_html_aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee"><div class="ttname"><a href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee">llfio_v2_xxx::handle::mode::write</a></div><div class="ttdoc">Ability to read and write (READ_CONTROL|FILE_READ_DATA|FILE_READ_ATTRIBUTES|FILE_READ_EA|FILE_WRITE_D...</div></div>
<div class="ttc" id="namespacellfio__v2__xxx_html_af31a062639499a79ef5cc8aed16ba65d"><div class="ttname"><a href="namespacellfio__v2__xxx.html#af31a062639499a79ef5cc8aed16ba65d">llfio_v2_xxx::file</a></div><div class="ttdeci">result< file_handle > file(const path_handle &base, file_handle::path_view_type path, file_handle::mode _mode=file_handle::mode::read, file_handle::creation _creation=file_handle::creation::open_existing, file_handle::caching _caching=file_handle::caching::all, file_handle::flag flags=file_handle::flag::none) noexcept</div><div class="ttdef"><b>Definition:</b> file_handle.hpp:501</div></div>
<div class="ttc" id="namespacellfio__v2__xxx_1_1utils_html_ae61e2de30b06776a1c24643a1d1dc64e"><div class="ttname"><a href="namespacellfio__v2__xxx_1_1utils.html#ae61e2de30b06776a1c24643a1d1dc64e">llfio_v2_xxx::utils::random_fill</a></div><div class="ttdeci">void random_fill(char *buffer, size_t bytes) noexcept</div><div class="ttdoc">Fills the buffer supplied with cryptographically strong randomness. Uses the OS kernel API...</div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1handle_html_aa3930273a2d4cabbac309e0b75701dcaa9516dfb15f51c7ee19a4d46b8c0dbe1d"><div class="ttname"><a href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaa9516dfb15f51c7ee19a4d46b8c0dbe1d">llfio_v2_xxx::handle::mode::append</a></div><div class="ttdoc">All mainstream OSs and CIFS guarantee this is atomic with respect to all other appenders (FILE_APPEND...</div></div>
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<h2 class="memtitle"><span class="permalink"><a href="#a09e6b3e9806b328a687a55e955b885a3">◆ </a></span>file()</h2>
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<td class="memname">static result<<a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a>> llfio_v2_xxx::file_handle::file </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> & </td>
<td class="paramname"><em>base</em>, </td>
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<td></td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view_type</a> </td>
<td class="paramname"><em>path</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> </td>
<td class="paramname"><em>_mode</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaecae13117d6f0584c25a9da6c8f8415e">mode::read</a></code>, </td>
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<td></td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42">creation</a> </td>
<td class="paramname"><em>_creation</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42aa200dcd6176417e93be2405188ae7cc9">creation::open_existing</a></code>, </td>
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<td class="paramname"><em>_caching</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852aa181a603769c1f98ad927e7367c7aa51">caching::all</a></code>, </td>
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<td class="paramname"><em>flags</em> = <code>flag::none</code> </td>
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<td></td>
<td>)</td>
<td></td><td></td>
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<p>Create a file handle opening access to a file on path </p><dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">base</td><td>Handle to a base location on the filing system. Pass <code>{}</code> to indicate that path will be absolute. </td></tr>
<tr><td class="paramname">path</td><td>The path relative to base to open. </td></tr>
<tr><td class="paramname">_mode</td><td>How to open the file. </td></tr>
<tr><td class="paramname">_creation</td><td>How to create the file. </td></tr>
<tr><td class="paramname">_caching</td><td>How to ask the kernel to cache the file. </td></tr>
<tr><td class="paramname">flags</td><td>Any additional custom behaviours.</td></tr>
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<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX open() or CreateFile() can return. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#a3b27d0f83fb72ebaa1e6a2eead9bec3e">◆ </a></span>lock_range() <span class="overload">[1/3]</span></h2>
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<td class="memname">virtual result<<a class="el" href="classllfio__v2__xxx_1_1file__handle_1_1extent__guard.html">extent_guard</a>> llfio_v2_xxx::fast_random_file_handle::lock_range </td>
<td>(</td>
<td class="paramtype">extent_type </td>
<td class="paramname"><em>offset</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype">extent_type </td>
<td class="paramname"><em>bytes</em>, </td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63">lock_kind</a> </td>
<td class="paramname"><em>kind</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> </td>
<td class="paramname"><em>d</em> = <code><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()</code> </td>
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<p>EXTENSION: Tries to lock the range of bytes specified for shared or exclusive access. Be aware this passes through the same semantics as the underlying OS call, including any POSIX insanity present on your platform: </p>
<ul>
<li>Any fd closed on an inode must release all byte range locks on that inode for all other fds. If your OS isn't new enough to support the non-insane lock API, <code>flag::byte_lock_insanity</code> will be set in flags() after the first call to this function.</li>
<li>Threads replace each other's locks, indeed locks replace each other's locks.</li>
</ul>
<p>You almost cetainly should use your choice of an <code>algorithm::shared_fs_mutex::*</code> instead of this as those are more portable and performant, or use the <code>SharedMutex</code> modelling member functions which lock the whole inode for exclusive or shared access.</p>
<dl class="section warning"><dt>Warning</dt><dd>This is a low-level API which you should not use directly in portable code. Another issue is that atomic lock upgrade/downgrade, if your platform implements that (you should assume it does not in portable code), means that on POSIX you need to <em>release</em> the old <code>extent_guard</code> after creating a new one over the same byte range, otherwise the old <code>extent_guard</code>'s destructor will simply unlock the range entirely. On Windows however upgrade/downgrade locks overlay, so on that platform you must <em>not</em> release the old <code>extent_guard</code>. Look into <code>algorithm::shared_fs_mutex::safe_byte_ranges</code> for a portable solution.</dd></dl>
<dl class="section return"><dt>Returns</dt><dd>An extent guard, the destruction of which will call unlock(). </dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">offset</td><td>The offset to lock. Note that on POSIX the top bit is always cleared before use as POSIX uses signed transport for offsets. If you want an advisory rather than mandatory lock on Windows, one technique is to force top bit set so the region you lock is not the one you will i/o - obviously this reduces maximum file size to (2^63)-1. </td></tr>
<tr><td class="paramname">bytes</td><td>The number of bytes to lock. </td></tr>
<tr><td class="paramname">kind</td><td>Whether the lock is to be shared or exclusive. </td></tr>
<tr><td class="paramname">d</td><td>An optional deadline by which the lock must complete, else it is cancelled. </td></tr>
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</dd>
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<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX fcntl() can return, <code>errc::timed_out</code>, <code>errc::not_supported</code> may be returned if deadline i/o is not possible with this particular handle configuration (e.g. non-overlapped HANDLE on Windows). </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>The default synchronous implementation in file_handle performs no memory allocation. The asynchronous implementation in async_file_handle performs one calloc and one free. </dd></dl>
<p>Reimplemented from <a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a5a9910116cc5751398e6b55f06a9a793">llfio_v2_xxx::file_handle</a>.</p>
<div class="fragment"><div class="line"><a name="l00294"></a><span class="lineno"> 294</span>  {</div><div class="line"><a name="l00295"></a><span class="lineno"> 295</span>  <span class="comment">// Lock nothing</span></div><div class="line"><a name="l00296"></a><span class="lineno"> 296</span>  <span class="keywordflow">return</span> _extent_guard(<span class="keyword">this</span>, offset, bytes, kind);</div><div class="line"><a name="l00297"></a><span class="lineno"> 297</span>  }</div></div><!-- fragment -->
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<h2 class="memtitle"><span class="permalink"><a href="#a3c5c229b11f488d0e9bff74c65737db2">◆ </a></span>lock_range() <span class="overload">[2/3]</span></h2>
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<td class="memname">result<<a class="el" href="classllfio__v2__xxx_1_1file__handle_1_1extent__guard.html">extent_guard</a>> llfio_v2_xxx::file_handle::lock_range </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< buffers_type > </td>
<td class="paramname"><em>reqs</em>, </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><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()</code> </td>
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<p>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </p>
<div class="fragment"><div class="line"><a name="l00387"></a><span class="lineno"> 387</span>  {</div><div class="line"><a name="l00388"></a><span class="lineno"> 388</span>  <span class="keywordtype">size_t</span> bytes = 0;</div><div class="line"><a name="l00389"></a><span class="lineno"> 389</span>  <span class="keywordflow">for</span>(<span class="keyword">auto</span> &i : reqs.buffers)</div><div class="line"><a name="l00390"></a><span class="lineno"> 390</span>  {</div><div class="line"><a name="l00391"></a><span class="lineno"> 391</span>  <span class="keywordflow">if</span>(bytes + i.size() < bytes)</div><div class="line"><a name="l00392"></a><span class="lineno"> 392</span>  {</div><div class="line"><a name="l00393"></a><span class="lineno"> 393</span>  <span class="keywordflow">return</span> errc::value_too_large;</div><div class="line"><a name="l00394"></a><span class="lineno"> 394</span>  }</div><div class="line"><a name="l00395"></a><span class="lineno"> 395</span>  bytes += i.size();</div><div class="line"><a name="l00396"></a><span class="lineno"> 396</span>  }</div><div class="line"><a name="l00397"></a><span class="lineno"> 397</span>  <span class="keywordflow">return</span> <a class="code" href="classllfio__v2__xxx_1_1file__handle.html#a5a9910116cc5751398e6b55f06a9a793">lock_range</a>(reqs.offset, bytes, <a class="code" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63a9e81e7b963c71363e2fb3eefcfecfc0e">lock_kind::shared</a>, d);</div><div class="line"><a name="l00398"></a><span class="lineno"> 398</span>  }</div><div class="ttc" id="classllfio__v2__xxx_1_1file__handle_html_aa25e3ab298152166fc387d8fcfb19a63a9e81e7b963c71363e2fb3eefcfecfc0e"><div class="ttname"><a href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63a9e81e7b963c71363e2fb3eefcfecfc0e">llfio_v2_xxx::file_handle::lock_kind::shared</a></div><div class="ttdoc">Exclude only those requesting an exclusive lock on the same inode. </div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1file__handle_html_a5a9910116cc5751398e6b55f06a9a793"><div class="ttname"><a href="classllfio__v2__xxx_1_1file__handle.html#a5a9910116cc5751398e6b55f06a9a793">llfio_v2_xxx::file_handle::lock_range</a></div><div class="ttdeci">virtual result< extent_guard > lock_range(extent_type offset, extent_type bytes, lock_kind kind, deadline d=deadline()) noexcept</div><div class="ttdoc">EXTENSION: Tries to lock the range of bytes specified for shared or exclusive access. Be aware this passes through the same semantics as the underlying OS call, including any POSIX insanity present on your platform: </div></div>
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<td class="memname">result<<a class="el" href="classllfio__v2__xxx_1_1file__handle_1_1extent__guard.html">extent_guard</a>> llfio_v2_xxx::file_handle::lock_range </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type > </td>
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<p>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </p>
<div class="fragment"><div class="line"><a name="l00401"></a><span class="lineno"> 401</span>  {</div><div class="line"><a name="l00402"></a><span class="lineno"> 402</span>  <span class="keywordtype">size_t</span> bytes = 0;</div><div class="line"><a name="l00403"></a><span class="lineno"> 403</span>  <span class="keywordflow">for</span>(<span class="keyword">auto</span> &i : reqs.buffers)</div><div class="line"><a name="l00404"></a><span class="lineno"> 404</span>  {</div><div class="line"><a name="l00405"></a><span class="lineno"> 405</span>  <span class="keywordflow">if</span>(bytes + i.size() < bytes)</div><div class="line"><a name="l00406"></a><span class="lineno"> 406</span>  {</div><div class="line"><a name="l00407"></a><span class="lineno"> 407</span>  <span class="keywordflow">return</span> errc::value_too_large;</div><div class="line"><a name="l00408"></a><span class="lineno"> 408</span>  }</div><div class="line"><a name="l00409"></a><span class="lineno"> 409</span>  bytes += i.size();</div><div class="line"><a name="l00410"></a><span class="lineno"> 410</span>  }</div><div class="line"><a name="l00411"></a><span class="lineno"> 411</span>  <span class="keywordflow">return</span> <a class="code" href="classllfio__v2__xxx_1_1file__handle.html#a5a9910116cc5751398e6b55f06a9a793">lock_range</a>(reqs.offset, bytes, <a class="code" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63aa4293995cfbfa9ce60ce71ade2ff75f7">lock_kind::exclusive</a>, d);</div><div class="line"><a name="l00412"></a><span class="lineno"> 412</span>  }</div><div class="ttc" id="classllfio__v2__xxx_1_1file__handle_html_aa25e3ab298152166fc387d8fcfb19a63aa4293995cfbfa9ce60ce71ade2ff75f7"><div class="ttname"><a href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63aa4293995cfbfa9ce60ce71ade2ff75f7">llfio_v2_xxx::file_handle::lock_kind::exclusive</a></div><div class="ttdoc">Exclude those requesting any kind of lock on the same inode. </div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1file__handle_html_a5a9910116cc5751398e6b55f06a9a793"><div class="ttname"><a href="classllfio__v2__xxx_1_1file__handle.html#a5a9910116cc5751398e6b55f06a9a793">llfio_v2_xxx::file_handle::lock_range</a></div><div class="ttdeci">virtual result< extent_guard > lock_range(extent_type offset, extent_type bytes, lock_kind kind, deadline d=deadline()) noexcept</div><div class="ttdoc">EXTENSION: Tries to lock the range of bytes specified for shared or exclusive access. Be aware this passes through the same semantics as the underlying OS call, including any POSIX insanity present on your platform: </div></div>
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<h2 class="memtitle"><span class="permalink"><a href="#ade38a6d55a4eda3c6d5e196683b129a7">◆ </a></span>max_buffers()</h2>
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<td class="memname">virtual size_t llfio_v2_xxx::io_handle::max_buffers </td>
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<p>The <em>maximum</em> number of buffers which a single read or write syscall can process at a time for this specific open handle. On POSIX, this is known as <code>IOV_MAX</code>. </p>
<p>Note that the actual number of buffers accepted for a read or a write may be significantly lower than this system-defined limit, depending on available resources. The <code>read()</code> or <code>write()</code> call will return the buffers accepted.</p>
<p>Note also that some OSs will error out if you supply more than this limit to <code>read()</code> or <code>write()</code>, but other OSs do not. Some OSs guarantee that each i/o syscall has effects atomically visible or not to other i/o, other OSs do not.</p>
<p>OS X does not implement scatter-gather file i/o syscalls. Thus this function will always return <code>1</code> in that situation.</p>
<p>Microsoft Windows <em>may</em> implement scatter-gather file i/o under very limited circumstances. Most of the time this function will return <code>1</code>. </p>
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<h2 class="memtitle"><span class="permalink"><a href="#a865caad2f7f4bdf12fb74aabfe3c5ff5">◆ </a></span>parent_path_handle()</h2>
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<td class="memname">virtual result<<a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a>> llfio_v2_xxx::fs_handle::parent_path_handle </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> </td>
<td class="paramname"><em>d</em> = <code>std::chrono::seconds(30)</code></td><td>)</td>
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<p>Obtain a handle to the path <b>currently</b> containing this handle's file entry.</p>
<dl class="section warning"><dt>Warning</dt><dd>This call is <b>racy</b> and can result in the wrong path handle being returned. Note that unless <code>flag::disable_safety_unlinks</code> is set, this implementation opens a <code>path_handle</code> to the source containing directory, then checks if the file entry within has the same inode as the open file handle. It will retry this matching until success until the deadline given.</dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>Calls <code>current_path()</code> and thus is both expensive and calls malloc many times.</dd></dl>
<dl class="section see"><dt>See also</dt><dd><code>algorithm::cached_parent_handle_adapter<T></code> which overrides this with a zero cost implementation, thus making unlinking and relinking very considerably quicker. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#ac5222904f116c9beb0515a4a5aa850bf">◆ </a></span>QUICKCPPLIB_BITFIELD_BEGIN()</h2>
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<td class="memname">llfio_v2_xxx::handle::QUICKCPPLIB_BITFIELD_BEGIN </td>
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<p>Bitwise flags which can be specified. </p>
<p>< No flags </p><pre class="fragment">Unlinks the file on handle close. On POSIX, this simply unlinks whatever is pointed
</pre><p> to by <code>path()</code> upon the call of <code>close()</code> if and only if the inode matches. On Windows, if you are on Windows 10 1709 or later, exactly the same thing occurs. If on previous editions of Windows, the file entry does not disappears but becomes unavailable for anyone else to open with an <code>errc::resource_unavailable_try_again</code> error return. Because this is confusing, unless the <code>win_disable_unlink_emulation</code> flag is also specified, this POSIX behaviour is somewhat emulated by LLFIO on older Windows by renaming the file to a random name on <code>close()</code> causing it to appear to have been unlinked immediately.</p>
<p>Some kernel caching modes have unhelpfully inconsistent behaviours in getting your data onto storage, so by default unless this flag is specified LLFIO adds extra fsyncs to the following operations for the caching modes specified below: truncation of file length either explicitly or during file open. closing of the handle either explicitly or in the destructor.</p>
<p>Additionally on Linux only to prevent loss of file metadata: On the parent directory whenever a file might have been created. On the parent directory on file close.</p>
<p>This only occurs for these kernel caching modes: caching::none caching::reads caching::reads_and_metadata caching::safety_barriers</p>
<p><code>file_handle::unlink()</code> could accidentally delete the wrong file if someone has renamed the open file handle since the time it was opened. To prevent this occuring, where the OS doesn't provide race free unlink-by-open-handle we compare the inode of the path we are about to unlink with that of the open handle before unlinking. </p><dl class="section warning"><dt>Warning</dt><dd>This does not prevent races where in between the time of checking the inode and executing the unlink a third party changes the item about to be unlinked. Only operating systems with a true race-free unlink syscall are race free.</dd></dl>
<p>Ask the OS to disable prefetching of data. This can improve random i/o performance.</p>
<p>Ask the OS to maximise prefetching of data, possibly prefetching the entire file into kernel cache. This can improve sequential i/o performance.</p>
<p>< See the documentation for <code>unlink_on_first_close</code> </p><pre class="fragment">Microsoft Windows NTFS, having been created in the late 1980s, did not originally
</pre><p> implement extents-based storage and thus could only represent sparse files via efficient compression of intermediate zeros. With NTFS v3.0 (Microsoft Windows 2000), a proper extents-based on-storage representation was added, thus allowing only 64Kb extent chunks written to be stored irrespective of whatever the maximum file extent was set to.</p>
<p>For various historical reasons, extents-based storage is disabled by default in newly created files on NTFS, unlike in almost every other major filing system. You have to explicitly "opt in" to extents-based storage.</p>
<p>As extents-based storage is nearly cost free on NTFS, LLFIO by default opts in to extents-based storage for any empty file it creates. If you don't want this, you can specify this flag to prevent that happening.</p>
<p>Filesystems tend to be embarrassingly parallel for operations performed to different inodes. Where LLFIO performs i/o to multiple inodes at a time, it will use OpenMP or the Parallelism or Concurrency standard library extensions to usually complete the operation in constant rather than linear time. If you don't want this default, you can disable default using this flag.</p>
<p>Microsoft Windows NTFS has the option, when creating a directory, to set whether leafname lookup will be case sensitive. This is the only way of getting exact POSIX semantics on Windows without resorting to editing the system registry, however it also affects all code doing lookups within that directory, so we must default it to off.</p>
<p>< On Windows, create any new handles with OVERLAPPED semantics</p>
<p>< Using insane POSIX byte range locks</p>
<p>< This is an inode created with no representation on the filing system </p>
<div class="fragment"><div class="line"><a name="l00098"></a><span class="lineno"> 98</span>  {</div><div class="line"><a name="l00099"></a><span class="lineno"> 99</span>  none = 0, <span class="comment">//!< No flags</span></div><div class="line"><a name="l00100"></a><span class="lineno"> 100</span> <span class="comment"></span><span class="comment"> /*! Unlinks the file on handle close. On POSIX, this simply unlinks whatever is pointed</span></div><div class="line"><a name="l00101"></a><span class="lineno"> 101</span> <span class="comment"> to by `path()` upon the call of `close()` if and only if the inode matches. On Windows,</span></div><div class="line"><a name="l00102"></a><span class="lineno"> 102</span> <span class="comment"> if you are on Windows 10 1709 or later, exactly the same thing occurs. If on previous</span></div><div class="line"><a name="l00103"></a><span class="lineno"> 103</span> <span class="comment"> editions of Windows, the file entry does not disappears but becomes unavailable for</span></div><div class="line"><a name="l00104"></a><span class="lineno"> 104</span> <span class="comment"> anyone else to open with an `errc::resource_unavailable_try_again` error return. Because this is confusing, unless the</span></div><div class="line"><a name="l00105"></a><span class="lineno"> 105</span> <span class="comment"> `win_disable_unlink_emulation` flag is also specified, this POSIX behaviour is</span></div><div class="line"><a name="l00106"></a><span class="lineno"> 106</span> <span class="comment"> somewhat emulated by LLFIO on older Windows by renaming the file to a random name on `close()`</span></div><div class="line"><a name="l00107"></a><span class="lineno"> 107</span> <span class="comment"> causing it to appear to have been unlinked immediately.</span></div><div class="line"><a name="l00108"></a><span class="lineno"> 108</span> <span class="comment"> */</span></div><div class="line"><a name="l00109"></a><span class="lineno"> 109</span>  unlink_on_first_close = 1U << 0U,</div><div class="line"><a name="l00110"></a><span class="lineno"> 110</span> <span class="comment"></span></div><div class="line"><a name="l00111"></a><span class="lineno"> 111</span> <span class="comment"> /*! Some kernel caching modes have unhelpfully inconsistent behaviours</span></div><div class="line"><a name="l00112"></a><span class="lineno"> 112</span> <span class="comment"> in getting your data onto storage, so by default unless this flag is</span></div><div class="line"><a name="l00113"></a><span class="lineno"> 113</span> <span class="comment"> specified LLFIO adds extra fsyncs to the following operations for the</span></div><div class="line"><a name="l00114"></a><span class="lineno"> 114</span> <span class="comment"> caching modes specified below:</span></div><div class="line"><a name="l00115"></a><span class="lineno"> 115</span> <span class="comment"> * truncation of file length either explicitly or during file open.</span></div><div class="line"><a name="l00116"></a><span class="lineno"> 116</span> <span class="comment"> * closing of the handle either explicitly or in the destructor.</span></div><div class="line"><a name="l00117"></a><span class="lineno"> 117</span> <span class="comment"></span></div><div class="line"><a name="l00118"></a><span class="lineno"> 118</span> <span class="comment"> Additionally on Linux only to prevent loss of file metadata:</span></div><div class="line"><a name="l00119"></a><span class="lineno"> 119</span> <span class="comment"> * On the parent directory whenever a file might have been created.</span></div><div class="line"><a name="l00120"></a><span class="lineno"> 120</span> <span class="comment"> * On the parent directory on file close.</span></div><div class="line"><a name="l00121"></a><span class="lineno"> 121</span> <span class="comment"></span></div><div class="line"><a name="l00122"></a><span class="lineno"> 122</span> <span class="comment"> This only occurs for these kernel caching modes:</span></div><div class="line"><a name="l00123"></a><span class="lineno"> 123</span> <span class="comment"> * caching::none</span></div><div class="line"><a name="l00124"></a><span class="lineno"> 124</span> <span class="comment"> * caching::reads</span></div><div class="line"><a name="l00125"></a><span class="lineno"> 125</span> <span class="comment"> * caching::reads_and_metadata</span></div><div class="line"><a name="l00126"></a><span class="lineno"> 126</span> <span class="comment"> * caching::safety_barriers</span></div><div class="line"><a name="l00127"></a><span class="lineno"> 127</span> <span class="comment"> */</span></div><div class="line"><a name="l00128"></a><span class="lineno"> 128</span>  disable_safety_barriers = 1U << 2U,<span class="comment"></span></div><div class="line"><a name="l00129"></a><span class="lineno"> 129</span> <span class="comment"> /*! `file_handle::unlink()` could accidentally delete the wrong file if someone has</span></div><div class="line"><a name="l00130"></a><span class="lineno"> 130</span> <span class="comment"> renamed the open file handle since the time it was opened. To prevent this occuring,</span></div><div class="line"><a name="l00131"></a><span class="lineno"> 131</span> <span class="comment"> where the OS doesn't provide race free unlink-by-open-handle we compare the inode of</span></div><div class="line"><a name="l00132"></a><span class="lineno"> 132</span> <span class="comment"> the path we are about to unlink with that of the open handle before unlinking.</span></div><div class="line"><a name="l00133"></a><span class="lineno"> 133</span> <span class="comment"> \warning This does not prevent races where in between the time of checking the inode</span></div><div class="line"><a name="l00134"></a><span class="lineno"> 134</span> <span class="comment"> and executing the unlink a third party changes the item about to be unlinked. Only</span></div><div class="line"><a name="l00135"></a><span class="lineno"> 135</span> <span class="comment"> operating systems with a true race-free unlink syscall are race free.</span></div><div class="line"><a name="l00136"></a><span class="lineno"> 136</span> <span class="comment"> */</span></div><div class="line"><a name="l00137"></a><span class="lineno"> 137</span>  disable_safety_unlinks = 1U << 3U,<span class="comment"></span></div><div class="line"><a name="l00138"></a><span class="lineno"> 138</span> <span class="comment"> /*! Ask the OS to disable prefetching of data. This can improve random</span></div><div class="line"><a name="l00139"></a><span class="lineno"> 139</span> <span class="comment"> i/o performance.</span></div><div class="line"><a name="l00140"></a><span class="lineno"> 140</span> <span class="comment"> */</span></div><div class="line"><a name="l00141"></a><span class="lineno"> 141</span>  disable_prefetching = 1U << 4U,<span class="comment"></span></div><div class="line"><a name="l00142"></a><span class="lineno"> 142</span> <span class="comment"> /*! Ask the OS to maximise prefetching of data, possibly prefetching the entire file</span></div><div class="line"><a name="l00143"></a><span class="lineno"> 143</span> <span class="comment"> into kernel cache. This can improve sequential i/o performance.</span></div><div class="line"><a name="l00144"></a><span class="lineno"> 144</span> <span class="comment"> */</span></div><div class="line"><a name="l00145"></a><span class="lineno"> 145</span>  maximum_prefetching = 1U << 5U,</div><div class="line"><a name="l00146"></a><span class="lineno"> 146</span> </div><div class="line"><a name="l00147"></a><span class="lineno"> 147</span>  win_disable_unlink_emulation = 1U << 24U, <span class="comment">//!< See the documentation for `unlink_on_first_close`</span></div><div class="line"><a name="l00148"></a><span class="lineno"> 148</span> <span class="comment"></span><span class="comment"> /*! Microsoft Windows NTFS, having been created in the late 1980s, did not originally</span></div><div class="line"><a name="l00149"></a><span class="lineno"> 149</span> <span class="comment"> implement extents-based storage and thus could only represent sparse files via</span></div><div class="line"><a name="l00150"></a><span class="lineno"> 150</span> <span class="comment"> efficient compression of intermediate zeros. With NTFS v3.0 (Microsoft Windows 2000),</span></div><div class="line"><a name="l00151"></a><span class="lineno"> 151</span> <span class="comment"> a proper extents-based on-storage representation was added, thus allowing only 64Kb</span></div><div class="line"><a name="l00152"></a><span class="lineno"> 152</span> <span class="comment"> extent chunks written to be stored irrespective of whatever the maximum file extent</span></div><div class="line"><a name="l00153"></a><span class="lineno"> 153</span> <span class="comment"> was set to.</span></div><div class="line"><a name="l00154"></a><span class="lineno"> 154</span> <span class="comment"></span></div><div class="line"><a name="l00155"></a><span class="lineno"> 155</span> <span class="comment"> For various historical reasons, extents-based storage is disabled by default in newly</span></div><div class="line"><a name="l00156"></a><span class="lineno"> 156</span> <span class="comment"> created files on NTFS, unlike in almost every other major filing system. You have to</span></div><div class="line"><a name="l00157"></a><span class="lineno"> 157</span> <span class="comment"> explicitly "opt in" to extents-based storage.</span></div><div class="line"><a name="l00158"></a><span class="lineno"> 158</span> <span class="comment"></span></div><div class="line"><a name="l00159"></a><span class="lineno"> 159</span> <span class="comment"> As extents-based storage is nearly cost free on NTFS, LLFIO by default opts in to</span></div><div class="line"><a name="l00160"></a><span class="lineno"> 160</span> <span class="comment"> extents-based storage for any empty file it creates. If you don't want this, you</span></div><div class="line"><a name="l00161"></a><span class="lineno"> 161</span> <span class="comment"> can specify this flag to prevent that happening.</span></div><div class="line"><a name="l00162"></a><span class="lineno"> 162</span> <span class="comment"> */</span></div><div class="line"><a name="l00163"></a><span class="lineno"> 163</span>  win_disable_sparse_file_creation = 1U << 25U,<span class="comment"></span></div><div class="line"><a name="l00164"></a><span class="lineno"> 164</span> <span class="comment"> /*! Filesystems tend to be embarrassingly parallel for operations performed to different</span></div><div class="line"><a name="l00165"></a><span class="lineno"> 165</span> <span class="comment"> inodes. Where LLFIO performs i/o to multiple inodes at a time, it will use OpenMP or</span></div><div class="line"><a name="l00166"></a><span class="lineno"> 166</span> <span class="comment"> the Parallelism or Concurrency standard library extensions to usually complete the</span></div><div class="line"><a name="l00167"></a><span class="lineno"> 167</span> <span class="comment"> operation in constant rather than linear time. If you don't want this default, you can</span></div><div class="line"><a name="l00168"></a><span class="lineno"> 168</span> <span class="comment"> disable default using this flag.</span></div><div class="line"><a name="l00169"></a><span class="lineno"> 169</span> <span class="comment"> */</span></div><div class="line"><a name="l00170"></a><span class="lineno"> 170</span>  disable_parallelism = 1U << 26U,<span class="comment"></span></div><div class="line"><a name="l00171"></a><span class="lineno"> 171</span> <span class="comment"> /*! Microsoft Windows NTFS has the option, when creating a directory, to set whether</span></div><div class="line"><a name="l00172"></a><span class="lineno"> 172</span> <span class="comment"> leafname lookup will be case sensitive. This is the only way of getting exact POSIX</span></div><div class="line"><a name="l00173"></a><span class="lineno"> 173</span> <span class="comment"> semantics on Windows without resorting to editing the system registry, however it also</span></div><div class="line"><a name="l00174"></a><span class="lineno"> 174</span> <span class="comment"> affects all code doing lookups within that directory, so we must default it to off.</span></div><div class="line"><a name="l00175"></a><span class="lineno"> 175</span> <span class="comment"> */</span></div><div class="line"><a name="l00176"></a><span class="lineno"> 176</span>  win_create_case_sensitive_directory = 1U << 27U,</div><div class="line"><a name="l00177"></a><span class="lineno"> 177</span> </div><div class="line"><a name="l00178"></a><span class="lineno"> 178</span>  <span class="comment">// NOTE: IF UPDATING THIS UPDATE THE std::ostream PRINTER BELOW!!!</span></div><div class="line"><a name="l00179"></a><span class="lineno"> 179</span> </div><div class="line"><a name="l00180"></a><span class="lineno"> 180</span>  overlapped = 1U << 28U, <span class="comment">//!< On Windows, create any new handles with OVERLAPPED semantics</span></div><div class="line"><a name="l00181"></a><span class="lineno"> 181</span> <span class="comment"></span> byte_lock_insanity = 1U << 29U, <span class="comment">//!< Using insane POSIX byte range locks</span></div><div class="line"><a name="l00182"></a><span class="lineno"> 182</span> <span class="comment"></span> anonymous_inode = 1U << 30U <span class="comment">//!< This is an inode created with no representation on the filing system</span></div><div class="line"><a name="l00183"></a><span class="lineno"> 183</span> <span class="comment"></span> } QUICKCPPLIB_BITFIELD_END(flag);</div></div><!-- fragment -->
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<h2 class="memtitle"><span class="permalink"><a href="#a3141a85996e46a3cc6b238d321198e47">◆ </a></span>random_file()</h2>
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<td class="memname">static result<<a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a>> llfio_v2_xxx::file_handle::random_file </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> & </td>
<td class="paramname"><em>dirpath</em>, </td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> </td>
<td class="paramname"><em>_mode</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee">mode::write</a></code>, </td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> </td>
<td class="paramname"><em>_caching</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852ad5197d93c063a2b1e22d1630a39b7aef">caching::temporary</a></code>, </td>
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<p>Create a file handle creating a randomly named file on a path. The file is opened exclusively with <code>creation::only_if_not_exist</code> so it will never collide with nor overwrite any existing file. Note also that caching defaults to temporary which hints to the OS to only flush changes to physical storage as lately as possible.</p>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX open() or CreateFile() can return. </dd></dl>
<div class="fragment"><div class="line"><a name="l00144"></a><span class="lineno"> 144</span>  {</div><div class="line"><a name="l00145"></a><span class="lineno"> 145</span>  <span class="keywordflow">try</span></div><div class="line"><a name="l00146"></a><span class="lineno"> 146</span>  {</div><div class="line"><a name="l00147"></a><span class="lineno"> 147</span>  <span class="keywordflow">for</span>(;;)</div><div class="line"><a name="l00148"></a><span class="lineno"> 148</span>  {</div><div class="line"><a name="l00149"></a><span class="lineno"> 149</span>  <span class="keyword">auto</span> randomname = <a class="code" href="namespacellfio__v2__xxx_1_1utils.html#a6a29cf29a4b097411f6c1e5274bfb417">utils::random_string</a>(32);</div><div class="line"><a name="l00150"></a><span class="lineno"> 150</span>  randomname.append(<span class="stringliteral">".random"</span>);</div><div class="line"><a name="l00151"></a><span class="lineno"> 151</span>  result<file_handle> ret = <a class="code" href="classllfio__v2__xxx_1_1file__handle.html#a09e6b3e9806b328a687a55e955b885a3">file</a>(dirpath, randomname, _mode, <a class="code" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42abba3bc579480e6c94ecd81b7b5923255">creation::only_if_not_exist</a>, _caching, <a class="code" href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">flags</a>);</div><div class="line"><a name="l00152"></a><span class="lineno"> 152</span>  <span class="keywordflow">if</span>(ret || (!ret && ret.error() != errc::file_exists))</div><div class="line"><a name="l00153"></a><span class="lineno"> 153</span>  {</div><div class="line"><a name="l00154"></a><span class="lineno"> 154</span>  <span class="keywordflow">return</span> ret;</div><div class="line"><a name="l00155"></a><span class="lineno"> 155</span>  }</div><div class="line"><a name="l00156"></a><span class="lineno"> 156</span>  }</div><div class="line"><a name="l00157"></a><span class="lineno"> 157</span>  }</div><div class="line"><a name="l00158"></a><span class="lineno"> 158</span>  <span class="keywordflow">catch</span>(...)</div><div class="line"><a name="l00159"></a><span class="lineno"> 159</span>  {</div><div class="line"><a name="l00160"></a><span class="lineno"> 160</span>  <span class="keywordflow">return</span> error_from_exception();</div><div class="line"><a name="l00161"></a><span class="lineno"> 161</span>  }</div><div class="line"><a name="l00162"></a><span class="lineno"> 162</span>  }</div><div class="ttc" id="classllfio__v2__xxx_1_1file__handle_html_a09e6b3e9806b328a687a55e955b885a3"><div class="ttname"><a href="classllfio__v2__xxx_1_1file__handle.html#a09e6b3e9806b328a687a55e955b885a3">llfio_v2_xxx::file_handle::file</a></div><div class="ttdeci">static result< file_handle > file(const path_handle &base, path_view_type path, mode _mode=mode::read, creation _creation=creation::open_existing, caching _caching=caching::all, flag flags=flag::none) noexcept</div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1handle_html_a013936bc1254b1a47567fe29698d1b1c"><div class="ttname"><a href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">llfio_v2_xxx::handle::flags</a></div><div class="ttdeci">flag flags() const noexcept</div><div class="ttdoc">The flags this handle was opened with. </div><div class="ttdef"><b>Definition:</b> handle.hpp:335</div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1handle_html_af0b352d0f273ba6fa70c178b2c2fee42abba3bc579480e6c94ecd81b7b5923255"><div class="ttname"><a href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42abba3bc579480e6c94ecd81b7b5923255">llfio_v2_xxx::handle::creation::only_if_not_exist</a></div><div class="ttdoc">Filesystem entry must NOT exist, and is atomically created by the success of this operation...</div></div>
<div class="ttc" id="namespacellfio__v2__xxx_1_1utils_html_a6a29cf29a4b097411f6c1e5274bfb417"><div class="ttname"><a href="namespacellfio__v2__xxx_1_1utils.html#a6a29cf29a4b097411f6c1e5274bfb417">llfio_v2_xxx::utils::random_string</a></div><div class="ttdeci">std::string random_string(size_t randomlen)</div><div class="ttdoc">Returns a cryptographically random string capable of being used as a filename. Essentially random_fil...</div><div class="ttdef"><b>Definition:</b> utils.hpp:134</div></div>
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<h2 class="memtitle"><span class="permalink"><a href="#ae84ac3c127d067d44d978e4621d4d2f1">◆ </a></span>read() <span class="overload">[1/2]</span></h2>
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<td class="memname">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a><buffers_type> llfio_v2_xxx::fast_random_file_handle::read </td>
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<p>Read data from the random file. </p>
<p>Note that ensuring that the scatter buffers are address and size aligned to 16 byte (128 bit) multiples will give maximum performance.</p>
<dl class="section return"><dt>Returns</dt><dd>The buffers input, with the size of each scatter-gather buffer updated with the number of bytes of that buffer transferred. </dd></dl>
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<tr><td class="paramname">reqs</td><td>A scatter-gather and offset request. </td></tr>
<tr><td class="paramname">d</td><td>Ignored. </td></tr>
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<dl class="section user"><dt>Errors returnable</dt><dd>None possible. </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>None possible. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#a5f7485307a0704aa1680e5785be2035d">◆ </a></span>read() <span class="overload">[2/2]</span></h2>
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<td class="memname">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a><buffers_type> llfio_v2_xxx::io_handle::read </td>
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<p>Read data from the open handle. </p>
<dl class="section warning"><dt>Warning</dt><dd>Depending on the implementation backend, <b>very</b> different buffers may be returned than you supplied. You should <b>always</b> use the buffers returned and assume that they point to different memory and that each buffer's size will have changed.</dd></dl>
<dl class="section return"><dt>Returns</dt><dd>The buffers read, which may not be the buffers input. The size of each scatter-gather buffer returned is updated with the number of bytes of that buffer transferred, and the pointer to the data may be <em>completely</em> different to what was submitted (e.g. it may point into a memory map). </dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">reqs</td><td>A scatter-gather and offset request. </td></tr>
<tr><td class="paramname">d</td><td>An optional deadline by which the i/o must complete, else it is cancelled. Note function may return significantly after this deadline if the i/o takes long to cancel. </td></tr>
</table>
</dd>
</dl>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX read() can return, <code>errc::timed_out</code>, <code>errc::operation_canceled</code>. <code>errc::not_supported</code> may be returned if deadline i/o is not possible with this particular handle configuration (e.g. reading from regular files on POSIX or reading from a non-overlapped HANDLE on Windows). </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>The default synchronous implementation in file_handle performs no memory allocation. The asynchronous implementation in async_file_handle performs one calloc and one free. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#a8700edc9ecd4dd35d5aad7c65dd0eca2">◆ </a></span>relink()</h2>
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<td class="memname">virtual result<void> llfio_v2_xxx::fs_handle::relink </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> & </td>
<td class="paramname"><em>base</em>, </td>
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<td></td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1fs__handle.html#abcd8c8171f4e561620864295e8d5879b">path_view_type</a> </td>
<td class="paramname"><em>path</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype">bool </td>
<td class="paramname"><em>atomic_replace</em> = <code>true</code>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> </td>
<td class="paramname"><em>d</em> = <code>std::chrono::seconds(30)</code> </td>
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<p>Relinks the current path of this open handle to the new path specified. If <code>atomic_replace</code> is true, the relink <b>atomically</b> and silently replaces any item at the new path specified. This operation is both atomic and silent matching POSIX behaviour even on Microsoft Windows where no Win32 API can match POSIX semantics.</p>
<dl class="section warning"><dt>Warning</dt><dd>Some operating systems provide a race free syscall for renaming an open handle (Windows). On all other operating systems this call is <b>racy</b> and can result in the wrong file entry being relinked. Note that unless <code>flag::disable_safety_unlinks</code> is set, this implementation opens a <code>path_handle</code> to the source containing directory first, then checks before relinking that the item about to be relinked has the same inode as the open file handle. It will retry this matching until success until the deadline given. This should prevent most unmalicious accidental loss of data.</dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">base</td><td>Base for any relative path. </td></tr>
<tr><td class="paramname">path</td><td>The relative or absolute new path to relink to. </td></tr>
<tr><td class="paramname">atomic_replace</td><td>Atomically replace the destination if a file entry already is present there. Choosing false for this will fail if a file entry is already present at the destination, and may not be an atomic operation on some platforms (i.e. both the old and new names may be linked to the same inode for a very short period of time). Windows and recent Linuxes are always atomic. </td></tr>
<tr><td class="paramname">d</td><td>The deadline by which the matching of the containing directory to the open handle's inode must succeed, else <code>errc::timed_out</code> will be returned. </td></tr>
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</dd>
</dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>Except on platforms with race free syscalls for renaming open handles (Windows), calls <code>current_path()</code> via <code>parent_path_handle()</code> and thus is both expensive and calls malloc many times. </dd></dl>
<p>Reimplemented in <a class="el" href="classllfio__v2__xxx_1_1symlink__handle.html#afea9ef2b36cac3f6dfcae7555ca3303c">llfio_v2_xxx::symlink_handle</a>.</p>
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<h2 class="memtitle"><span class="permalink"><a href="#a101620e9fff0c0e8c346af0e9de58b6a">◆ </a></span>set_append_only()</h2>
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<td class="memname">virtual result<void> llfio_v2_xxx::handle::set_append_only </td>
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<td class="paramtype">bool </td>
<td class="paramname"><em>enable</em></td><td>)</td>
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<p>EXTENSION: Changes whether this handle is append only or not. </p>
<dl class="section warning"><dt>Warning</dt><dd>On Windows this is implemented as a bit of a hack to make it fast like on POSIX, so make sure you open the handle for read/write originally. Note unlike on POSIX the append_only disposition will be the only one toggled, seekable and readable will remain turned on.</dd></dl>
<dl class="section user"><dt>Errors returnable</dt><dd>Whatever POSIX fcntl() returns. On Windows nothing is changed on the handle. </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>No memory allocation. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#a428114e3c8628c0621b1aa156051651c">◆ </a></span>temp_file()</h2>
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<td class="memname">static result<<a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a>> llfio_v2_xxx::file_handle::temp_file </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view_type</a> </td>
<td class="paramname"><em>name</em> = <code><a class="el" href="classllfio__v2__xxx_1_1path__view.html">path_view_type</a>()</code>, </td>
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<td></td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dca">mode</a> </td>
<td class="paramname"><em>_mode</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee">mode::write</a></code>, </td>
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<td class="paramkey"></td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42">creation</a> </td>
<td class="paramname"><em>_creation</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#af0b352d0f273ba6fa70c178b2c2fee42a8f0339e854eb5321306a443ce9199e1d">creation::if_needed</a></code>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852">caching</a> </td>
<td class="paramname"><em>_caching</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#aecd3a7db6cee3aec07d32fe6f99e6852ad5197d93c063a2b1e22d1630a39b7aef">caching::temporary</a></code>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype">flag </td>
<td class="paramname"><em>flags</em> = <code>flag::unlink_on_first_close</code> </td>
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<td></td>
<td>)</td>
<td></td><td></td>
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<p>Create a file handle creating the named file on some path which the OS declares to be suitable for temporary files. Most OSs are very lazy about flushing changes made to these temporary files. Note the default flags are to have the newly created file deleted on first handle close. Note also that an empty name is equivalent to calling <code>random_file(path_discovery::storage_backed_temporary_files_directory())</code> and the creation parameter is ignored.</p>
<dl class="section note"><dt>Note</dt><dd>If the temporary file you are creating is not going to have its path sent to another process for usage, this is the WRONG function to use. Use <code>temp_inode()</code> instead, it is far more secure.</dd></dl>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX open() or CreateFile() can return. </dd></dl>
<div class="fragment"><div class="line"><a name="l00180"></a><span class="lineno"> 180</span>  {</div><div class="line"><a name="l00181"></a><span class="lineno"> 181</span>  <span class="keyword">auto</span> &tempdirh = <a class="code" href="namespacellfio__v2__xxx_1_1path__discovery.html#a2dd74ea752f3f511d58ccccdcac7f4fd">path_discovery::storage_backed_temporary_files_directory</a>();</div><div class="line"><a name="l00182"></a><span class="lineno"> 182</span>  <span class="keywordflow">return</span> name.empty() ? <a class="code" href="classllfio__v2__xxx_1_1file__handle.html#a3141a85996e46a3cc6b238d321198e47">random_file</a>(tempdirh, _mode, _caching, <a class="code" href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">flags</a>) : <a class="code" href="classllfio__v2__xxx_1_1file__handle.html#a09e6b3e9806b328a687a55e955b885a3">file</a>(tempdirh, name, _mode, _creation, _caching, <a class="code" href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">flags</a>);</div><div class="line"><a name="l00183"></a><span class="lineno"> 183</span>  }</div><div class="ttc" id="classllfio__v2__xxx_1_1file__handle_html_a09e6b3e9806b328a687a55e955b885a3"><div class="ttname"><a href="classllfio__v2__xxx_1_1file__handle.html#a09e6b3e9806b328a687a55e955b885a3">llfio_v2_xxx::file_handle::file</a></div><div class="ttdeci">static result< file_handle > file(const path_handle &base, path_view_type path, mode _mode=mode::read, creation _creation=creation::open_existing, caching _caching=caching::all, flag flags=flag::none) noexcept</div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1handle_html_a013936bc1254b1a47567fe29698d1b1c"><div class="ttname"><a href="classllfio__v2__xxx_1_1handle.html#a013936bc1254b1a47567fe29698d1b1c">llfio_v2_xxx::handle::flags</a></div><div class="ttdeci">flag flags() const noexcept</div><div class="ttdoc">The flags this handle was opened with. </div><div class="ttdef"><b>Definition:</b> handle.hpp:335</div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1file__handle_html_a3141a85996e46a3cc6b238d321198e47"><div class="ttname"><a href="classllfio__v2__xxx_1_1file__handle.html#a3141a85996e46a3cc6b238d321198e47">llfio_v2_xxx::file_handle::random_file</a></div><div class="ttdeci">static result< file_handle > random_file(const path_handle &dirpath, mode _mode=mode::write, caching _caching=caching::temporary, flag flags=flag::none) noexcept</div><div class="ttdef"><b>Definition:</b> file_handle.hpp:143</div></div>
<div class="ttc" id="namespacellfio__v2__xxx_1_1path__discovery_html_a2dd74ea752f3f511d58ccccdcac7f4fd"><div class="ttname"><a href="namespacellfio__v2__xxx_1_1path__discovery.html#a2dd74ea752f3f511d58ccccdcac7f4fd">llfio_v2_xxx::path_discovery::storage_backed_temporary_files_directory</a></div><div class="ttdeci">const path_handle & storage_backed_temporary_files_directory() noexcept</div><div class="ttdoc">Returns a reference to an open handle to a verified temporary directory where files created are store...</div></div>
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<h2 class="memtitle"><span class="permalink"><a href="#a1eff21e1833be0c21f72477c593fadc5">◆ </a></span>temp_inode()</h2>
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<td class="memname">static result<<a class="el" href="classllfio__v2__xxx_1_1file__handle.html">file_handle</a>> llfio_v2_xxx::file_handle::temp_inode </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="classllfio__v2__xxx_1_1path__handle.html">path_handle</a> & </td>
<td class="paramname"><em>dirh</em> = <code><a class="el" href="namespacellfio__v2__xxx_1_1path__discovery.html#a2dd74ea752f3f511d58ccccdcac7f4fd">path_discovery::storage_backed_temporary_files_directory</a>()</code>, </td>
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<td class="paramname"><em>_mode</em> = <code><a class="el" href="classllfio__v2__xxx_1_1handle.html#aa3930273a2d4cabbac309e0b75701dcaaefb2a684e4afb7d55e6147fbe5a332ee">mode::write</a></code>, </td>
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<td class="paramtype">flag </td>
<td class="paramname"><em>flags</em> = <code>flag::none</code> </td>
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<p><em>Securely</em> create a file handle creating a temporary anonymous inode in the filesystem referred to by <em>dirpath</em>. The inode created has no name nor accessible path on the filing system and ceases to exist as soon as the last handle is closed, making it ideal for use as a temporary file where other processes do not need to have access to its contents via some path on the filing system (a classic use case is for backing shared memory maps).</p>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX open() or CreateFile() can return. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#a2919da8c2520240c4e65f18f68872fd0">◆ </a></span>try_lock_range()</h2>
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<td class="memname">result<<a class="el" href="classllfio__v2__xxx_1_1file__handle_1_1extent__guard.html">extent_guard</a>> llfio_v2_xxx::file_handle::try_lock_range </td>
<td>(</td>
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<td class="paramtype">extent_type </td>
<td class="paramname"><em>bytes</em>, </td>
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<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1file__handle.html#aa25e3ab298152166fc387d8fcfb19a63">lock_kind</a> </td>
<td class="paramname"><em>kind</em> </td>
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<p>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </p>
<div class="fragment"><div class="line"><a name="l00384"></a><span class="lineno"> 384</span> { <span class="keywordflow">return</span> <a class="code" href="classllfio__v2__xxx_1_1file__handle.html#a5a9910116cc5751398e6b55f06a9a793">lock_range</a>(offset, bytes, kind, deadline(std::chrono::seconds(0))); }</div><div class="ttc" id="classllfio__v2__xxx_1_1file__handle_html_a5a9910116cc5751398e6b55f06a9a793"><div class="ttname"><a href="classllfio__v2__xxx_1_1file__handle.html#a5a9910116cc5751398e6b55f06a9a793">llfio_v2_xxx::file_handle::lock_range</a></div><div class="ttdeci">virtual result< extent_guard > lock_range(extent_type offset, extent_type bytes, lock_kind kind, deadline d=deadline()) noexcept</div><div class="ttdoc">EXTENSION: Tries to lock the range of bytes specified for shared or exclusive access. Be aware this passes through the same semantics as the underlying OS call, including any POSIX insanity present on your platform: </div></div>
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<h2 class="memtitle"><span class="permalink"><a href="#a1dd7923bb65456af4da41ebe7cb84982">◆ </a></span>unlink()</h2>
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<td class="memname">virtual result<void> llfio_v2_xxx::fs_handle::unlink </td>
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<td class="paramname"><em>d</em> = <code>std::chrono::seconds(30)</code></td><td>)</td>
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<p>Unlinks the current path of this open handle, causing its entry to immediately disappear from the filing system. On Windows before Windows 10 1709 unless <code>flag::win_disable_unlink_emulation</code> is set, this behaviour is simulated by renaming the file to something random and setting its delete-on-last-close flag. Note that Windows may prevent the renaming of a file in use by another process, if so it will NOT be renamed. After the next handle to that file closes, it will become permanently unopenable by anyone else until the last handle is closed, whereupon the entry will be eventually removed by the operating system.</p>
<dl class="section warning"><dt>Warning</dt><dd>Some operating systems provide a race free syscall for unlinking an open handle (Windows). On all other operating systems this call is <b>racy</b> and can result in the wrong file entry being unlinked. Note that unless <code>flag::disable_safety_unlinks</code> is set, this implementation opens a <code>path_handle</code> to the containing directory first, then checks that the item about to be unlinked has the same inode as the open file handle. It will retry this matching until success until the deadline given. This should prevent most unmalicious accidental loss of data.</dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
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<tr><td class="paramname">d</td><td>The deadline by which the matching of the containing directory to the open handle's inode must succeed, else <code>errc::timed_out</code> will be returned. </td></tr>
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</dd>
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<dl class="section user"><dt>Memory Allocations</dt><dd>Except on platforms with race free syscalls for unlinking open handles (Windows), calls <code>current_path()</code> and thus is both expensive and calls malloc many times. On Windows, also calls <code>current_path()</code> if <code>flag::disable_safety_unlinks</code> is not set. </dd></dl>
<p>Reimplemented in <a class="el" href="classllfio__v2__xxx_1_1symlink__handle.html#a002c9dab669604d58e08aa8f4dbc99c8">llfio_v2_xxx::symlink_handle</a>.</p>
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<h2 class="memtitle"><span class="permalink"><a href="#a0b20ae88c350702b39f41d8223f0b164">◆ </a></span>unlock_range()</h2>
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<td class="memname">virtual void llfio_v2_xxx::fast_random_file_handle::unlock_range </td>
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<td class="paramname"><em>bytes</em> </td>
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<p>EXTENSION: Unlocks a byte range previously locked. </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">offset</td><td>The offset to unlock. This should be an offset previously locked. </td></tr>
<tr><td class="paramname">bytes</td><td>The number of bytes to unlock. This should be a byte extent previously locked. </td></tr>
</table>
</dd>
</dl>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX fcntl() can return. </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>None. </dd></dl>
<p>Reimplemented from <a class="el" href="classllfio__v2__xxx_1_1file__handle.html#a0cd024de36cc7cb63d9189f45a9944e9">llfio_v2_xxx::file_handle</a>.</p>
<div class="fragment"><div class="line"><a name="l00300"></a><span class="lineno"> 300</span>  {</div><div class="line"><a name="l00301"></a><span class="lineno"> 301</span>  <span class="comment">// Unlock nothing</span></div><div class="line"><a name="l00302"></a><span class="lineno"> 302</span>  }</div></div><!-- fragment -->
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<h2 class="memtitle"><span class="permalink"><a href="#abdbe878fecb166d1eda5ddc4718e101d">◆ </a></span>write() <span class="overload">[1/3]</span></h2>
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<td class="memname">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a><const_buffers_type> llfio_v2_xxx::fast_random_file_handle::write </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< const_buffers_type > </td>
<td class="paramname"><em>reqs</em>, </td>
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<td></td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> </td>
<td class="paramname"><em>d</em> = <code><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()</code> </td>
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<td>)</td>
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<span class="mlabels"><span class="mlabel">inline</span><span class="mlabel">override</span><span class="mlabel">virtual</span><span class="mlabel">noexcept</span></span> </td>
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<p>Fails to write to the random file. </p>
<p>If the handle was not opened with write permissions, this will fail with a code comparing equal to <code>errc::permission_denied</code>. Otherwise the writes have no effect, and the buffers returned have all zero lengths.</p>
<dl class="section return"><dt>Returns</dt><dd>The buffers written with all buffer lengths zeroed. </dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">reqs</td><td>A scatter-gather and offset request. </td></tr>
<tr><td class="paramname">d</td><td>Ignored. </td></tr>
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</dd>
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<dl class="section user"><dt>Errors returnable</dt><dd>None possible if handle was opened with write permissions. </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>None possible. </dd></dl>
<div class="fragment"><div class="line"><a name="l00262"></a><span class="lineno"> 262</span>  {</div><div class="line"><a name="l00263"></a><span class="lineno"> 263</span>  (void) d;</div><div class="line"><a name="l00264"></a><span class="lineno"> 264</span>  OUTCOME_TRY(_perms_check());</div><div class="line"><a name="l00265"></a><span class="lineno"> 265</span>  <span class="comment">// Return null written</span></div><div class="line"><a name="l00266"></a><span class="lineno"> 266</span>  <span class="keywordflow">for</span>(<span class="keyword">auto</span> &buffer : reqs.buffers)</div><div class="line"><a name="l00267"></a><span class="lineno"> 267</span>  {</div><div class="line"><a name="l00268"></a><span class="lineno"> 268</span>  buffer = {buffer.data(), 0};</div><div class="line"><a name="l00269"></a><span class="lineno"> 269</span>  }</div><div class="line"><a name="l00270"></a><span class="lineno"> 270</span>  <span class="keywordflow">return</span> std::move(reqs.buffers);</div><div class="line"><a name="l00271"></a><span class="lineno"> 271</span>  }</div></div><!-- fragment -->
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<a id="a83884eca7b4cd09125a5cf8a155e6052"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a83884eca7b4cd09125a5cf8a155e6052">◆ </a></span>write() <span class="overload">[2/3]</span></h2>
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<td class="memname">virtual <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a><const_buffers_type> llfio_v2_xxx::io_handle::write </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__request.html">io_request</a>< <a class="el" href="classllfio__v2__xxx_1_1io__handle.html#a693a8c64bb7de1a6835d6a151e37aa0e">const_buffers_type</a> > </td>
<td class="paramname"><em>reqs</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a> </td>
<td class="paramname"><em>d</em> = <code><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()</code> </td>
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<td></td>
<td>)</td>
<td></td><td></td>
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<span class="mlabels"><span class="mlabel">inline</span><span class="mlabel">virtual</span><span class="mlabel">noexcept</span><span class="mlabel">inherited</span></span> </td>
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<p>Write data to the open handle. </p>
<dl class="section warning"><dt>Warning</dt><dd>Depending on the implementation backend, not all of the buffers input may be written. For example, with a zeroed deadline, some backends may only consume as many buffers as the system has available write slots for, thus for those backends this call is "non-blocking" in the sense that it will return immediately even if it could not schedule a single buffer write. Another example is that some implementations will not auto-extend the length of a file when a write exceeds the maximum extent, you will need to issue a <code>truncate(newsize)</code> first.</dd></dl>
<dl class="section return"><dt>Returns</dt><dd>The buffers written, which may not be the buffers input. The size of each scatter-gather buffer returned is updated with the number of bytes of that buffer transferred. </dd></dl>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">reqs</td><td>A scatter-gather and offset request. </td></tr>
<tr><td class="paramname">d</td><td>An optional deadline by which the i/o must complete, else it is cancelled. Note function may return significantly after this deadline if the i/o takes long to cancel. </td></tr>
</table>
</dd>
</dl>
<dl class="section user"><dt>Errors returnable</dt><dd>Any of the values POSIX write() can return, <code>errc::timed_out</code>, <code>errc::operation_canceled</code>. <code>errc::not_supported</code> may be returned if deadline i/o is not possible with this particular handle configuration (e.g. writing to regular files on POSIX or writing to a non-overlapped HANDLE on Windows). </dd></dl>
<dl class="section user"><dt>Memory Allocations</dt><dd>The default synchronous implementation in file_handle performs no memory allocation. The asynchronous implementation in async_file_handle performs one calloc and one free. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#ab500784aa806dc7c2d90028d2f72de57">◆ </a></span>write() <span class="overload">[3/3]</span></h2>
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<td class="memname"><a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1io__result.html">io_result</a><size_type> llfio_v2_xxx::io_handle::write </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classllfio__v2__xxx_1_1handle.html#a4ee58f1b6a24af5e64d850d1e3eed07f">extent_type</a> </td>
<td class="paramname"><em>offset</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">std::initializer_list< <a class="el" href="structllfio__v2__xxx_1_1io__handle_1_1const__buffer__type.html">const_buffer_type</a> > </td>
<td class="paramname"><em>lst</em>, </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><a class="el" href="structllfio__v2__xxx_1_1deadline.html">deadline</a>()</code> </td>
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<p>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </p>
<div class="fragment"><div class="line"><a name="l00370"></a><span class="lineno"> 370</span>  {</div><div class="line"><a name="l00371"></a><span class="lineno"> 371</span>  const_buffer_type *_reqs = <span class="keyword">reinterpret_cast<</span>const_buffer_type *<span class="keyword">></span>(alloca(<span class="keyword">sizeof</span>(const_buffer_type) * lst.size()));</div><div class="line"><a name="l00372"></a><span class="lineno"> 372</span>  memcpy(_reqs, lst.begin(), <span class="keyword">sizeof</span>(const_buffer_type) * lst.size());</div><div class="line"><a name="l00373"></a><span class="lineno"> 373</span>  io_request<const_buffers_type> reqs(<a class="code" href="classllfio__v2__xxx_1_1io__handle.html#a693a8c64bb7de1a6835d6a151e37aa0e">const_buffers_type</a>(_reqs, lst.size()), offset);</div><div class="line"><a name="l00374"></a><span class="lineno"> 374</span>  <span class="keyword">auto</span> ret = <a class="code" href="classllfio__v2__xxx_1_1io__handle.html#a83884eca7b4cd09125a5cf8a155e6052">write</a>(reqs, d);</div><div class="line"><a name="l00375"></a><span class="lineno"> 375</span>  <span class="keywordflow">if</span>(ret)</div><div class="line"><a name="l00376"></a><span class="lineno"> 376</span>  {</div><div class="line"><a name="l00377"></a><span class="lineno"> 377</span>  <span class="keywordflow">return</span> ret.bytes_transferred();</div><div class="line"><a name="l00378"></a><span class="lineno"> 378</span>  }</div><div class="line"><a name="l00379"></a><span class="lineno"> 379</span>  <span class="keywordflow">return</span> std::move(ret).error();</div><div class="line"><a name="l00380"></a><span class="lineno"> 380</span>  }</div><div class="ttc" id="classllfio__v2__xxx_1_1io__handle_html_a693a8c64bb7de1a6835d6a151e37aa0e"><div class="ttname"><a href="classllfio__v2__xxx_1_1io__handle.html#a693a8c64bb7de1a6835d6a151e37aa0e">llfio_v2_xxx::io_handle::const_buffers_type</a></div><div class="ttdeci">span< const_buffer_type > const_buffers_type</div><div class="ttdoc">The gather buffers type used by this handle. Guaranteed to be TrivialType apart from construction...</div><div class="ttdef"><b>Definition:</b> io_handle.hpp:188</div></div>
<div class="ttc" id="classllfio__v2__xxx_1_1io__handle_html_a83884eca7b4cd09125a5cf8a155e6052"><div class="ttname"><a href="classllfio__v2__xxx_1_1io__handle.html#a83884eca7b4cd09125a5cf8a155e6052">llfio_v2_xxx::io_handle::write</a></div><div class="ttdeci">virtual io_result< const_buffers_type > write(io_request< const_buffers_type > reqs, deadline d=deadline()) noexcept</div><div class="ttdoc">Write data to the open handle. </div></div>
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<hr/>The documentation for this class was generated from the following file:<ul>
<li>include/llfio/v2.0/<a class="el" href="fast__random__file__handle_8hpp.html">fast_random_file_handle.hpp</a></li>
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