Sindbad~EG File Manager
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<p>Library Version 18.1.40</p>
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<div class="sect1" lang="en" xml:lang="en">
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<h2 class="title" style="clear: both"><a id="stl_container_specific"></a>Dbstl container specific
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<dt>
<span class="sect2">
<a href="stl_container_specific.html#idm140654539330192">db_vector specific notes</a>
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<dt>
<span class="sect2">
<a href="stl_container_specific.html#idm140654539204112">Associative container specific notes</a>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="idm140654539330192"></a>db_vector specific notes</h3>
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<p>
Set the <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> flag in the database
handle if you want
<code class="classname">db_vector<></code> to
work like <code class="classname">std::vector</code> or
<code class="classname">std::deque</code>. Do not set
<a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> if you want
<code class="classname">db_vector<></code> to
work like <code class="classname">std::list</code>. Note
that without <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> set,
<code class="classname">db_vector<></code> can
work faster.
</p>
<p>
For example, to construct a fast
std::queue/std::stack object, you only need a
<code class="classname">db_vector<></code>
object whose database handle does not have
<a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> set. Of course, if the database
handle has <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> set, it still works for
this kind of scenario, just not as fast.
</p>
<p>
<code class="classname">db_vector</code> does not check
whether <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> is set. If you do not set
it, <code class="classname">db_vector<></code> will
not work like
std::vector<>/std::deque<> with regard
to operator[], because the indices are not
maintained in that case.
</p>
<p>
You can find example code showing how to use
this feature in the
<code class="methodname">StlAdvancedFeaturesExample::queue_stack()</code>
method.
</p>
</li>
<li>
<p>
Just as is the case with
<code class="classname">std::vector</code>,
inserting/deleting in the middle of a
<code class="classname">db_vector</code> is slower
than doing the same action at the end of the
sequence. This is because the underlying DB_RECNO
DB (with the <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> flag set) is relatively
slow when inserting/deleting in the middle or the
head — it has to update the index numbers of
all the records following the one that was
inserted/deleted. If you do not need to keep the
index ordered on insert/delete, you can use
<code class="classname">db_map</code> instead.
</p>
<p>
<code class="classname">db_vector</code> also contains
methods inherited from
<code class="classname">std::list</code> and
<code class="classname">std::deque</code>, including
<code class="classname">std::list<>'s</code>
unique methods <code class="methodname">remove()</code>,
<code class="methodname">remove_if()</code>,
<code class="methodname">unique()</code>,
<code class="methodname">merge()</code>,
<code class="methodname">sort()</code>,
<code class="methodname">reverse()</code>, and
<code class="methodname">splice()</code>. These use
the identical semantics/behaviors of the
<code class="classname">std::list<></code>
methods, although pushing/deleting at the head is
slower than the
<code class="methodname">std::deque</code> and
<code class="methodname">std::list</code> equivalent
when there are quite a lot of elements in the
database.
</p>
</li>
<li>
<p>
You can use <code class="classname">std::queue</code>,
<code class="classname">std::priority_queue</code> and
<code class="classname">std::stack</code> container
adapters with <code class="classname">db_vector</code>;
they work with db_vector even without
<a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> set.
</p>
</li>
</ul>
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<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idm140654539204112"></a>Associative container specific notes</h3>
</div>
</div>
</div>
<p>
<code class="classname">db_map</code> contains the union of method
set from <code class="classname">std::map</code> and
<code class="classname">hash_map</code>, but there are some
methods that can only be called on containers backed by
<code class="literal">DB_BTREE</code> or
<code class="literal">DB_HASH</code> databases. You can call
<code class="function">db_map<>::is_hash()</code> to
figure out the type of the backing database. If you call
unsupported methods then an InvalidFunctionCall exception
is thrown.
</p>
<p>
These are the <code class="literal">DB_BTREE</code> specific
methods: <code class="methodname">upper_bound()</code>,
<code class="methodname">lower_bound()</code>,
<code class="methodname">key_comp()</code>, and
<code class="methodname">value_comp()</code>. The
<code class="literal">DB_HASH</code> specific methods are
<code class="methodname">key_eq()</code>,
<code class="methodname">hash_funct()</code>.
</p>
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