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Removed remote_download and remote_install.

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* The implementation is now responsible for supplying
  run-time time zone database updates.
This commit is contained in:
Howard Hinnant
2017-10-15 14:26:27 -04:00
parent 3370dab0ed
commit 7957b976bc
1 changed files with 19 additions and 63 deletions
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d0355r4.html
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@@ -59,6 +59,9 @@ Document number: D0355R4<br>
<h3>Changes since <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0355r3.html">R3</a></h3>
<ul>
<li>Presume that the time zone database is supplied only by the std::lib implementation,
but can be updated at run time. Removed <code>remote_download</code> and
<code>remote_install</code>. This functionality is now subsumed by the implementation.</li>
<li><code>to_stream</code> sets <code>failbit</code> if it is required to create a name
for an invalid month or weekday.</li>
<li>Add note to promise compatibility with <a href="https://wg21.link/p0645"><code>fmt</code> (P0645)</a></li>
@@ -9254,9 +9257,14 @@ tzdb::const_iterator tzdb::cend() const noexcept;
</p>
<a name="time.timezone.database.remote"></a><h3>23.17.12.1.1 Remote time zone database support [time.timezone.database.remote]</h3>
<p class = note>
This subsection is optional/separable and needs further discussion in the LEWG. No
other sections depend upon this subsection.
<p>
The <i>local</i> time zone database is that supplied by the implementation when the
application first accesses the database, for example via <code>current_zone()</code>.
While the application is running, the implementation may choose to update the time
zone database. This update shall not impact the application in any way unless the
application calls the functions in this section. This potentially updated time zone
database is referred to as the <i>remote</i> time zone database.
</p>
<pre>
@@ -9264,12 +9272,9 @@ const tzdb&amp; reload_tzdb();
</pre>
<blockquote>
<p>
<i>Effects:</i> This function first checks the latest version at the
<a href="http://www.iana.org/time-zones">IANA website</a>. If the
<a href="http://www.iana.org/time-zones">IANA website</a> is unavailable, or if the
latest version is already installed, there are no effects. Otherwise, a new version
is available. It is downloaded and installed, and then the program initializes
a new <code>tzdb</code> from the new disk files and pushes it to the front of
<i>Effects:</i> This function first checks the version of the remote time zone database.
If the version of the local and remote databases are the same, there are no effects.
Otherwise the remote database is pushed to the front of
the <code>tzdb_list</code> accessed by <code>get_tzdb_list()</code>.
</p>
<p>
@@ -9279,8 +9284,8 @@ the <code>tzdb_list</code> accessed by <code>get_tzdb_list()</code>.
<i>Remarks:</i> No pointers, references or iterators are invalidated.
</p>
<p>
<i>Thread Safety:</i> This function is thread safe with respect to <code>front()</code>
and <code>erase_after()</code>.
<i>Thread Safety:</i> This function is thread safe with respect to
<code>get_tzdb_list().front()</code> and <code>get_tzdb_list().erase_after()</code>.
</p>
<p>
<i>Throws:</i> <code>runtime_error</code> if for any reason a reference can not
@@ -9293,61 +9298,12 @@ string remote_version();
</pre>
<blockquote>
<p>
<i>Returns:</i> The latest database version number from the
<a href="http://www.iana.org/time-zones">IANA website</a>. If the
<a href="http://www.iana.org/time-zones">IANA website</a> can not be reached, or
if it can be reached but the latest version number is unexpectedly not
available, the empty string is returned.
<i>Returns:</i> The latest remote database version. If the remote
version s not available, the empty string is returned.
</p>
<p>
<i>Note:</i> If non-empty, this can be compared with <code>get_tzdb().version</code> to
discover if you have the latest database installed.
</p>
</blockquote>
<pre>
bool remote_download(string_view version);
</pre>
<blockquote>
<p>
<i>Effects:</i> If <code>version == remote_version()</code> this function will download
the compressed tar file holding the latest time zone database from the
<a href="http://www.iana.org/time-zones">IANA website</a>. The tar file will be placed
at an unspecified location.
</p>
<p>
<i>Returns:</i> <code>true</code> if the database was successfully downloaded, else
<code>false</code>.
</p>
<p>
<i>Thread safety:</i> If called by multiple threads, there will be a race on the
creation of the tar file.
</p>
</blockquote>
<pre>
bool remote_install(string_view version);
</pre>
<blockquote>
<p>
<i>Effects:</i> If <code>version</code> refers to the file successfully
downloaded by <code>remote_download()</code> this function will remove the
existing time zone database, then extract a new database
from the tar file, and will then delete the tar file.
</p>
<p>
This function <i>does not</i> cause your program to re-initialize itself from
this new database. In order to do that, you must call
<code>reload_tzdb()</code> (or <code>get_tzdb()</code> if the database has yet
to be initialized).
</p>
<p>
<i>Returns:</i> <code>true</code> if the database was successfully replaced by
the tar file , else <code>false</code>.
</p>
<p>
<i>Thread safety:</i> If called by multiple threads, there will be a race on the
creation of the new database.
discover if the local and remote databases are equivalent.
</p>
</blockquote>