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<div class="identifier-type">class</div><div class="header"><chrono></div><h1 itemprop="name"><span class="namespace" title="namespace std::chrono">std::chrono::</span><span class="token">local_info</span><span class="cpp cpp20" title="C++20で追加">(C++20)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="o">::</span><span class="nn">chrono</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">struct</span><span class="w"> </span><span class="nc">local_info</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">static</span><span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">unique</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="w"> </span><span class="k">static</span><span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">nonexistent</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="w"> </span><span class="k">static</span><span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">ambiguous</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="sys_info.html">sys_info</a></span><span class="w"> </span><span class="n">first</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="sys_info.html">sys_info</a></span><span class="w"> </span><span class="n">second</span><span class="p">;</span>
<span class="w"> </span><span class="p">};</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p><code>local_info</code>は、ローカル時間に関するタイムゾーン情報の低レベルインタフェースを提供するクラスである。</p>
<p>このクラスの情報は、<code><a href="local_time.html">local_time</a></code>から<code><a href="sys_time.html">sys_time</a></code>に変換する際に使用される。</p>
<ul>
<li><code><a href="local_time.html">local_time</a></code>から<code><a href="sys_time.html">sys_time</a></code>への変換が一意に決まる場合、<code>result == unique</code>となり、<code>first</code>が正しい<code><a href="sys_info.html">sys_info</a></code>で埋められ、<code>second</code>はゼロ初期化される</li>
<li>存在しないローカル時間が生じる場合、<code>result == nonexistent</code>となり、<code>first</code>はそのローカル時間の直前に終了する<code><a href="sys_info.html">sys_info</a></code>で、<code>second</code>はそのローカル時間の直後に開始する<code><a href="sys_info.html">sys_info</a></code>で埋められる</li>
<li>あいまいなローカル時間が生じる場合、<code>result == ambiguous</code>となり、<code>first</code>はそのローカル時間の直後に終了する<code><a href="sys_info.html">sys_info</a></code>で、<code>second</code>はそのローカル時間の直前に開始する<code><a href="sys_info.html">sys_info</a></code>で埋められる</li>
</ul>
<h2>備考</h2>
<ul>
<li><code>nonexistent</code>および<code>ambiguous</code>は、サマータイムを採用しているタイムゾーンで生じる可能性がある<ul>
<li>存在しないローカル時間の例として、タイムゾーン<code>"America/New_York"</code>のローカル時刻 2016-03-13 02:30:00 は以下の隙間に位置するため存在しえない：<ul>
<li>2016-03-13 02:00:00 EST</li>
<li>2016-03-13 03:00:00 EDT</li>
<li>2016-03-13 07:00:00 UTC</li>
</ul>
</li>
<li>あいまいなローカル時間の例として、タイムゾーン<code>"America/New_York"</code>のローカル時刻 2016-11-06 01:30:00 は、以下のいずれかとなり、一意に決まらない：<ul>
<li>2016-11-06 05:30:00 UTC</li>
<li>2016-11-06 06:30:00 UTC</li>
</ul>
</li>
</ul>
</li>
</ul>
<h2>メンバ変数</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>変数</th>
<th>説明</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>unique</code></td>
<td><code>result</code>がこの値である場合、<code><a href="local_time.html">local_time</a></code>から<code><a href="sys_time.html">sys_time</a></code>への変換が一意に決まる</td>
</tr>
<tr>
<td><code>nonexistent</code></td>
<td><code>result</code>がこの値である場合、存在しないローカル時間である</td>
</tr>
<tr>
<td><code>ambiguous</code></td>
<td><code>result</code>がこの値である場合、重複するローカル時間があるため<code><a href="local_time.html">local_time</a></code>から<code><a href="sys_time.html">sys_time</a></code>への変換が一意に決まらない</td>
</tr>
<tr>
<td><code>first</code></td>
<td>変換に使用される第1候補のタイムゾーン情報</td>
</tr>
<tr>
<td><code>second</code></td>
<td>変換に使用される第2候補のタイムゾーン情報</td>
</tr>
</tbody>
</table>
<h2>非メンバ関数</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="local_info/op_ostream.html">operator<<</a></code></td>
<td>出力ストリームへの出力</td>
<td>C++20</td>
</tr>
</tbody>
</table>
<h2>文字列フォーマット</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="local_info/formatter.html">formatter</a></code></td>
<td><code><a href="../format/formatter.html">std::formatter</a></code>クラスの特殊化</td>
<td>C++20</td>
</tr>
</tbody>
</table>
<h2>例</h2>
<p><div class="yata" id="ebb79486bd99ed8368202e6ea9b7e474c243d0db"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../chrono.html"><chrono></a></span>
<span class="k">namespace</span><span class="w"> </span><span class="nn">chrono</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nn">std</span><span class="o">::</span><span class="nn">chrono</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">now</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="system_clock.html">chrono::system_clock</a></span><span class="o">::</span><span class="n"><a href="system_clock/now.html">now()</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="local_time.html">chrono::local_time</a></span><span class="w"> </span><span class="n">local_now</span><span class="p">{</span><span class="n">now</span><span class="p">.</span><span class="n"><a href="time_point/time_since_epoch.html">time_since_epoch()</a></span><span class="p">};</span>
<span class="w"> </span><span class="c1">// 日本のタイムゾーン</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="time_zone.html">chrono::time_zone</a></span><span class="o">*</span><span class="w"> </span><span class="n">tz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="locate_zone.html">chrono::locate_zone</a></span><span class="p">(</span><span class="s">"Asia/Tokyo"</span><span class="p">);</span>
<span class="w"> </span><span class="n"><span style="color:#ff0000">chrono::local_info</span></span><span class="w"> </span><span class="n">li</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="time_zone/get_info.html">tz->get_info</a></span><span class="p">(</span><span class="n">local_now</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">li</span><span class="p">.</span><span class="n">result</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="sys_info.html">chrono::sys_info</a></span><span class="w"> </span><span class="n">si</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">li</span><span class="p">.</span><span class="n">first</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="time_point/floor.html">chrono::floor</a></span><span class="o"><</span><span class="n"><a href="duration_aliases.html">chrono::hours</a></span><span class="o">></span><span class="p">(</span><span class="n">si</span><span class="p">.</span><span class="n">offset</span><span class="p">).</span><span class="n"><a href="duration/count.html">count()</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">" <a href="duration_aliases.html">hours</a>"</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span><span class="w"> </span><span class="c1">// UTCタイムゾーンからの差分時間</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">si</span><span class="p">.</span><span class="n">abbrev</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span><span class="w"> </span><span class="c1">// タイムゾーンの略称</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力</h3>
<p><pre><code>0
9 <a href="duration_aliases.html">hours</a>
JST
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++20</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../implementation.html#clang">Clang</a>: 9.0 <span aria-label="未実装" role="img" title="未実装">❌</span></li>
<li><a href="../../implementation.html#gcc">GCC</a>: 9.2 <span aria-label="未実装" role="img" title="未実装">❌</span></li>
<li><a href="../../implementation.html#visual_cpp">Visual C++</a>: 2019 Update 3 <span aria-label="未実装" role="img" title="未実装">❌</span></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://yohhoy.hatenadiary.jp/entry/20180326/p1" target="_blank">C++標準ライブラリのタイムゾーン(Time Zone) - yohhoyの日記</a></li>
</ul></div>
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