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<h1><A href="../../index.htm"><IMG height="86" alt="boost.png (6897 bytes)" src="../../boost.png" width="277" align="middle"
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border="0"></A>basic_intrusive_ref_counter class template</h1>
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<p>
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<A href="#Introduction">Introduction</A><br>
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<A href="#Synopsis">Synopsis</A><br>
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<A href="#Members">Members</A><br>
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</p>
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<h2><a name="Introduction">Introduction</a></h2>
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<p>The <STRONG>basic_intrusive_ref_counter</STRONG> class template implements a reference counter for a defived
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user's class that is intended to be used with <STRONG><a href="intrusive_ptr.html">intrusive_ptr</a></STRONG>.
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The base class has associated <STRONG>intrusive_ptr_add_ref</STRONG> and <STRONG>intrusive_ptr_release</STRONG> functions
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which modify the reference counter as needed and destroy the user's object when the counter drops to zero.</p>
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<p>The class template is parameterized on <STRONG>CounterPolicyT</STRONG>, which is a policy that defines the nature of the reference counter.
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Boost.SmartPtr provides two such policies: <STRONG>thread_unsafe_counter</STRONG> and <STRONG>thread_safe_counter</STRONG>. The former
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instructs the <STRONG>basic_intrusive_ref_counter</STRONG> base class to use a counter only suitable for a single-threaded use.
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Pointers to a single object that uses this kind of reference counter must not be used in different threads. The latter policy
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makes the reference counter thread-safe, unless the target platform doesn't support threading. Since in modern systems support for
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threading is common, a shorthand <STRONG>intrusive_ref_counter</STRONG> is provided, which is an alias for
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<STRONG>basic_intrusive_ref_counter<thread_safe_counter></STRONG>.</p>
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<h2><a name="Synopsis">Synopsis</a></h2>
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<pre>namespace boost {
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template<class CounterPolicyT> class basic_intrusive_ref_counter {
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public:
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<A href="#constructors" >basic_intrusive_ref_counter</A>();
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<A href="#constructors" >basic_intrusive_ref_counter</A>(basic_intrusive_ref_counter const & r);
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virtual <A href="#destructor" >~basic_intrusive_ref_counter</A>();
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basic_intrusive_ref_counter & <A href="#assignment" >operator=</A>(basic_intrusive_ref_counter const & r) noexcept;
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unsigned int <a href="#use_count" >use_count</a>() const noexcept;
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};
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struct thread_unsafe_counter;
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struct thread_safe_counter;
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typedef basic_intrusive_ref_counter<thread_safe_counter> intrusive_ref_counter;
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}</pre>
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<h2><a name="Members">Members</a></h2>
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<h3><a name="constructors">constructors</a></h3>
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<pre>basic_intrusive_ref_counter();</pre>
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<blockquote>
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<p><b>Postconditions:</b> <code>use_count() == 0</code>.</p>
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<p><b>Throws:</b> nothing.</p>
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<P><B>Notes:</B> The pointer to the constructed object is expected to be passed to <STRONG>intrusive_ptr</STRONG>
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constructor, assignment operator or <STRONG>reset()</STRONG> method, which would increment the reference counter.</P>
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</blockquote>
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<pre>basic_intrusive_ref_counter(basic_intrusive_ref_counter const &);</pre>
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<blockquote>
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<p><b>Postconditions:</b> <code>use_count() == 0</code>.</p>
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<p><b>Throws:</b> nothing.</p>
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<P><B>Notes:</B> The pointer to the constructed object is expected to be passed to <STRONG>intrusive_ptr</STRONG>
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constructor, assignment operator or <STRONG>reset()</STRONG> method, which would increment the reference counter.</P>
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</blockquote>
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<h3><a name="destructor">destructor</a></h3>
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<pre>virtual ~basic_intrusive_ref_counter();</pre>
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<BLOCKQUOTE>
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<P><B>Effects:</B> Destroys the counter object.</P>
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</BLOCKQUOTE>
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<H3><a name="assignment">assignment</a></H3>
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<pre>basic_intrusive_ref_counter & operator=(basic_intrusive_ref_counter const & r) noexcept;</pre>
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<BLOCKQUOTE>
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<P><B>Effects:</B> Does nothing, reference counter is not modified.</P>
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<P><B>Returns:</B> <code>*this</code>.</P>
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</BLOCKQUOTE>
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<H3><a name="use_count">use_count</a></H3>
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<pre>unsigned int use_count() const noexcept;</pre>
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<BLOCKQUOTE>
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<p><b>Returns:</b> The current value of the reference counter.</p>
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<p><b>Throws:</b> nothing.</p>
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<P><B>Notes:</B> The returned value may not be actual in multi-threaded applications.</P>
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</BLOCKQUOTE>
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<hr>
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<p>
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$Date: 2013-08-31 23:37:43 +0400 (Sat, 31 Aug 2013) $</p>
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<p>
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<small>Copyright © 2013 Andrey Semashev. Distributed under the Boost Software License, Version
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1.0. See accompanying file <A href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</A> or
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copy at <A href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>.</small></p>
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