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| <h1><img height="86" alt="boost.png (6897 bytes)" src="../../boost.png" |
| width="277" align="middle" border="0">basic_intrusive_ref_counter class template</h1> |
| <p> |
| <A href="#Introduction">Introduction</A><br> |
| <A href="#Synopsis">Synopsis</A><br> |
| <A href="#Members">Members</A><br> |
| </p> |
| <h2><a name="Introduction">Introduction</a></h2> |
| <p>The <STRONG>intrusive_ref_counter</STRONG> class template implements a reference counter for a derived |
| user's class that is intended to be used with <STRONG><a href="intrusive_ptr.html">intrusive_ptr</a></STRONG>. |
| The base class has associated <STRONG>intrusive_ptr_add_ref</STRONG> and <STRONG>intrusive_ptr_release</STRONG> functions |
| which modify the reference counter as needed and destroy the user's object when the counter drops to zero.</p> |
| <p>The class template is parameterized on <STRONG>DerivedT</STRONG> and <STRONG>CounterPolicyT</STRONG> parameters. |
| The first parameter is the user's class that derives from <STRONG>intrusive_ref_counter</STRONG>. This type |
| is needed in order to destroy the object correctly when there are no references to it left.</p> |
| <p>The second parameter is a policy that defines the nature of the reference counter. |
| Boost.SmartPtr provides two such policies: <STRONG>thread_unsafe_counter</STRONG> and <STRONG>thread_safe_counter</STRONG>. The former |
| instructs the <STRONG>intrusive_ref_counter</STRONG> base class to use a counter only suitable for a single-threaded use. |
| Pointers to a single object that uses this kind of reference counter must not be used in different threads. The latter policy |
| makes the reference counter thread-safe, unless the target platform doesn't support threading. Since in modern systems support for |
| threading is common, the default counter policy is <STRONG>thread_safe_counter</STRONG>.</p> |
| <h2><a name="Synopsis">Synopsis</a></h2> |
| <pre>namespace boost { |
| |
| struct thread_unsafe_counter; |
| struct thread_safe_counter; |
| |
| template<class DerivedT, class CounterPolicyT = thread_safe_counter> |
| class intrusive_ref_counter |
| { |
| public: |
| <A href="#constructors" >intrusive_ref_counter</A>() = noexcept; |
| <A href="#constructors" >intrusive_ref_counter</A>(intrusive_ref_counter const & r) = noexcept; |
| |
| intrusive_ref_counter & <A href="#assignment" >operator=</A>(intrusive_ref_counter const & r) noexcept; |
| |
| unsigned int <a href="#use_count" >use_count</a>() const noexcept; |
| |
| protected: |
| <A href="#destructor" >~intrusive_ref_counter</A>() = default; |
| }; |
| |
| }</pre> |
| <h2><a name="Members">Members</a></h2> |
| <h3><a name="constructors">constructors</a></h3> |
| <pre>intrusive_ref_counter();</pre> |
| <blockquote> |
| <p><b>Postconditions:</b> <code>use_count() == 0</code>.</p> |
| <p><b>Throws:</b> nothing.</p> |
| <P><B>Notes:</B> The pointer to the constructed object is expected to be passed to <STRONG>intrusive_ptr</STRONG> |
| constructor, assignment operator or <STRONG>reset()</STRONG> method, which would increment the reference counter.</P> |
| </blockquote> |
| <pre>intrusive_ref_counter(intrusive_ref_counter const &);</pre> |
| <blockquote> |
| <p><b>Postconditions:</b> <code>use_count() == 0</code>.</p> |
| <p><b>Throws:</b> nothing.</p> |
| <P><B>Notes:</B> The pointer to the constructed object is expected to be passed to <STRONG>intrusive_ptr</STRONG> |
| constructor, assignment operator or <STRONG>reset()</STRONG> method, which would increment the reference counter.</P> |
| </blockquote> |
| <h3><a name="destructor">destructor</a></h3> |
| <pre>~intrusive_ref_counter();</pre> |
| <BLOCKQUOTE> |
| <p><b>Throws:</b> nothing.</p> |
| <P><B>Effects:</B> Destroys the counter object.</P> |
| <P><B>Notes:</B> The destructor is protected so that the object can only be destroyed through the <STRONG>DerivedT</STRONG> class.</P> |
| </BLOCKQUOTE> |
| <H3><a name="assignment">assignment</a></H3> |
| <pre>intrusive_ref_counter & operator=(intrusive_ref_counter const & r) noexcept;</pre> |
| <BLOCKQUOTE> |
| <P><B>Effects:</B> Does nothing, reference counter is not modified.</P> |
| <P><B>Returns:</B> <code>*this</code>.</P> |
| </BLOCKQUOTE> |
| <H3><a name="use_count">use_count</a></H3> |
| <pre>unsigned int use_count() const noexcept;</pre> |
| <BLOCKQUOTE> |
| <p><b>Returns:</b> The current value of the reference counter.</p> |
| <p><b>Throws:</b> nothing.</p> |
| <P><B>Notes:</B> The returned value may not be actual in multi-threaded applications.</P> |
| </BLOCKQUOTE> |
| <hr> |
| <p>$Date$</p> |
| <p> |
| <small>Copyright © 2013 Andrey Semashev. Distributed under the Boost Software License, Version |
| 1.0. See accompanying file <A href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</A> or |
| 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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