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New casts for smart pointers.

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[SVN r12743]
This commit is contained in:
Darin Adler
2002-02-06 19:42:04 +00:00
parent f9782387d9
commit 0dd3285d56
4 changed files with 86 additions and 5 deletions
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shared_ptr.htm
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@@ -97,6 +97,10 @@ function must be passed in, or the pointed-to object must have a trivial destruc
shared_ptr&lt;T&gt <a href="#shared_static_cast">shared_static_cast</a>(shared_ptr&lt;U&gt; const &amp; r); // never throws
template&lt;typename T, typename U&gt;
shared_ptr&lt;T&gt <a href="#shared_dynamic_cast">shared_dynamic_cast</a>(shared_ptr&lt;U&gt; const &amp; r);
template&lt;typename T, typename U&gt;
shared_ptr&lt;T&gt <a href="#shared_polymorphic_cast">shared_polymorphic_cast</a>(shared_ptr&lt;U&gt; const &amp; r);
template&lt;typename T, typename U&gt;
shared_ptr&lt;T&gt <a href="#shared_polymorphic_downcast">shared_polymorphic_downcast</a>(shared_ptr&lt;U&gt; const &amp; r); // never throws
}</pre>
@@ -244,7 +248,7 @@ Provided as an aid to generic programming.</p>
<h3><a name="shared_static_cast">shared_static_cast</a></h3>
<pre>template&lt;typename T, typename U&gt;
shared_ptr&lt;T&gt <a href="#shared_static_cast">shared_static_cast</a>(shared_ptr&lt;U&gt; const &amp; r); // never throws</pre>
shared_ptr&lt;T&gt shared_static_cast(shared_ptr&lt;U&gt; const &amp; r); // never throws</pre>
<p>Perform a <b>static_cast</b> on the stored pointer, returning another <b>shared_ptr</b>.
The resulting smart pointer will share its use count with the original pointer.</p>
<p>Note that the seemingly equivalent expression</p>
@@ -253,7 +257,7 @@ The resulting smart pointer will share its use count with the original pointer.<
<h3><a name="shared_dynamic_cast">shared_dynamic_cast</a></h3>
<pre>template&lt;typename T, typename U&gt;
shared_ptr&lt;T&gt <a href="#shared_dynamic_cast">shared_dynamic_cast</a>(shared_ptr&lt;U&gt; const &amp; r);</pre>
shared_ptr&lt;T&gt shared_dynamic_cast(shared_ptr&lt;U&gt; const &amp; r);</pre>
<p>Perform a <b>dynamic_cast</b> on the stored pointer, returning another <b>shared_ptr</b>.
The resulting smart pointer will share its use count with the original pointer unless the result of the
cast is 0. The only exception which may be thrown is <b>std::bad_alloc</b>, which may be thrown during the
@@ -263,6 +267,22 @@ cast has no effect.</p>
<blockquote><code>shared_ptr&lt;T&gt;(dynamic_cast&lt;T*&gt;(r.get()))</code></blockquote>
<p>will eventually result in undefined behavior, attempting to delete the same object twice.</p>
<h3><a name="shared_polymorphic_cast">shared_polymorphic_cast</a></h3>
<pre>template&lt;typename T, typename U&gt;
shared_ptr&lt;T&gt shared_polymorphic_cast(shared_ptr&lt;U&gt; const &amp; r);</pre>
<p>Perform a <a href="../conversion/cast.htm#Polymorphic_cast"><b>polymorphic_cast</b><a> on the stored pointer,
returning another <b>shared_ptr</b>.
The resulting smart pointer will share its use count with the original pointer.
The only exception which may be thrown is <b>std::bad_cast</b>, if the pointer type can not be converted.
If an exception is thrown, the cast has no effect.</p>
<h3><a name="shared_polymorphic_downcast">shared_polymorphic_downcast</a></h3>
<pre>template&lt;typename T, typename U&gt;
shared_ptr&lt;T&gt shared_polymorphic_downcast(shared_ptr&lt;U&gt; const &amp; r); // never throws</pre>
<p>Perform a <a href="../conversion/cast.htm#Polymorphic_cast"><b>polymorphic_downcast</b><a> on the stored pointer,
returning another <b>shared_ptr</b>.
The resulting smart pointer will share its use count with the original pointer.</p>
<h2><a name="example">Example</a></h2>
<p>See <a href="shared_ptr_example.cpp">shared_ptr_example.cpp</a> for a complete example program.