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  <!ENTITY % threads.entities SYSTEM "entities.xml">
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<header name="boost/thread/thread.hpp"
  last-revision="$Date: 2004/07/17 04:33:59 $">
  <namespace name="boost">
    <class name="thread">
		<purpose>
			<para>The <classname>thread</classname> class represents threads of
			execution, and provides the functionality to create and manage 
			threads within the &Boost.Threads; library. See 
			<xref linkend="threads.glossary"/> for a precise description of 
			<link linkend="threads.glossary.thread">thread of execution</link>,
			and for definitions of threading-related terms and of thread states such as 
			<link linkend="threads.glossary.thread-state">blocked</link>.</para>
		</purpose>

		<description>
			<para>A <link linkend="threads.glossary.thread">thread of execution</link>
			has an initial function. For the program's initial thread, the initial 
			function is <code>main()</code>. For other threads, the initial 
			function is <code>operator()</code> of the function object passed to
			the <classname>thread</classname> object's constructor.</para>

			<para>A thread of execution  is said to be &quot;finished&quot; 
			or to have &quot;finished execution&quot; when its initial function returns or 
			is terminated. This includes completion of all thread cleanup 
			handlers, and completion of the normal C++ function return behaviors,
			such as destruction of automatic storage (stack) objects and releasing 
			any associated implementation resources.</para>

			<para>A thread object has an associated state which is either
			&quot;joinable&quot; or &quot;non-joinable&quot;.</para>

			<para>Except as described below, the policy used by an implementation
			of &Boost.Threads; to schedule transitions between thread states is 
			unspecified.</para>

			<para><note>Just as the lifetime of a file may be different from the
			lifetime of an <code>iostream</code> object which represents the file, the lifetime
			of a thread of execution may be different from the 
			<classname>thread</classname> object which represents the thread of 
			execution. In particular, after a call to <code>join()</code>,
			the thread of execution will no longer exist even though the 
			<classname>thread</classname> object continues to exist until the 
			end of its normal lifetime. The converse is also possible; if 
			a <classname>thread</classname> object is destroyed without 
			<code>join()</code> first having been called, the thread of execution 
			continues until its initial function completes.</note></para>
		</description>

		<inherit access="private">
			<type><classname>boost::noncopyable</classname></type>
			<purpose>Exposition only</purpose>
		</inherit>

		<constructor>
			<effects>Constructs a <classname>thread</classname> object 
			representing the current thread of execution.</effects>
			
			<postconditions><code>*this</code> is non-joinable.</postconditions>
			
			<notes><emphasis role="bold">Danger:</emphasis>
			<code>*this</code> is valid only within the current thread.</notes>
		</constructor>

		<constructor specifiers="explicit">
			<parameter name="threadfunc">
				<paramtype>const boost::function0&lt;void&gt;&amp;</paramtype>
			</parameter>
			
			<effects>
				Starts a new thread of execution and constructs a 
				<classname>thread</classname> object representing it. 
				Copies <code>threadfunc</code> (which in turn copies
				the function object wrapped by <code>threadfunc</code>) 
				to an internal location which persists for the lifetime 
				of the new thread of execution. Calls <code>operator()</code>
				on the copy of the <code>threadfunc</code> function object 
				in the new thread of execution.
			</effects>
			
			<postconditions><code>*this</code> is joinable.</postconditions>

			<throws><code>boost::thread_resource_error</code> if a new thread
			of execution cannot be started.</throws>
		</constructor>
		
		<destructor>
			<effects>Destroys <code>*this</code>. The actual thread of 
			execution may continue to execute after the 
			<classname>thread</classname> object has been destroyed.
			</effects>
			
			<notes>If <code>*this</code> is joinable the actual thread 
			of execution becomes &quot;detached&quot;. Any resources used 
			by the thread will be reclaimed when the thread of execution 
			completes. To ensure such a thread of execution runs to completion
			before the <classname>thread</classname> object is destroyed, call
			<code>join()</code>.</notes>
		</destructor>
		
		<method-group name="comparison">
			<method name="operator==" cv="const">
				<type>bool</type>
				
				<parameter name="rhs">
					<type>const thread&amp;</type>
				</parameter>
				
				<requires>The thread is non-terminated or <code>*this</code>
				is joinable.</requires>
				  
				<returns><code>true</code> if <code>*this</code> and 
				<code>rhs</code> represent the same thread of 
				execution.</returns>
			</method>
			
			<method name="operator!=" cv="const">
				<type>bool</type>
				
				<parameter name="rhs">
					<type>const thread&amp;</type>
				</parameter>
				
				<requires>The thread is non-terminated or <code>*this</code>
				is joinable.</requires>
				  
				<returns><code>!(*this==rhs)</code>.</returns>
			</method>
		</method-group>

		<method-group name="modifier">
			<method name="join">
				<type>void</type>
				
				<requires><code>*this</code> is joinable.</requires>
				  
				<effects>The current thread of execution blocks until the 
				initial function of the thread of execution represented by 
				<code>*this</code> finishes and all resources are 
				reclaimed.</effects>
				
				<postcondition><code>*this</code> is non-joinable.</postcondition>
				
				<notes>If <code>*this == thread()</code> the result is 
				implementation-defined. If the implementation doesn't
				detect this the result will be 
				<link linkend="threads.glossary.deadlock">deadlock</link>.
				</notes>
			</method>
		</method-group>

		<method-group name="static">
			<method name="sleep" specifiers="static">
				<type>void</type>
				
				<parameter name="xt">
					<paramtype>const <classname>xtime</classname>&amp;</paramtype>
				</parameter>
				
				<effects>The current thread of execution blocks until 
				<code>xt</code> is reached.</effects>
			</method>
			
			<method name="yield" specifiers="static">
				<type>void</type>

				<effects>The current thread of execution is placed in the
				<link linkend="threads.glossary.thread-state">ready</link> 
				state.</effects>
				
				<notes>
					<simpara>Allow the current thread to give up the rest of its 
					time slice (or other scheduling quota) to another thread. 
					Particularly useful in non-preemptive implementations.</simpara>
				</notes>
			</method>
		</method-group>
	</class>

	<class name="thread_group">
		<purpose>
			The <classname>thread_group</classname> class provides a container
			for easy grouping of threads to simplify several common thread 
			creation and management idioms.
		</purpose>

		<inherit access="private">
			<type><classname>boost::noncopyable</classname></type>
			<purpose>Exposition only</purpose>
		</inherit>


		<constructor>
			<effects>Constructs an empty <classname>thread_group</classname>
			container.</effects>
		</constructor>
		
		<destructor>
			<effects>Destroys each contained thread object. Destroys <code>*this</code>.</effects>
			
			<notes>Behavior is undefined if another thread references 
			<code>*this </code> during the execution of the destructor.
			</notes>
		</destructor>

		<method-group name="modifier">
			<method name="create_thread">
				<type><classname>thread</classname>*</type>
				
				<parameter name="threadfunc">
					<paramtype>const boost::function0&lt;void&gt;&amp;</paramtype>
				</parameter>
				
				<effects>Creates a new <classname>thread</classname> object 
				that executes <code>threadfunc</code> and adds it to the 
				<code>thread_group</code> container object's list of managed
				<classname>thread</classname> objects.</effects>
				
				<returns>Pointer to the newly created 
				<classname>thread</classname> object.</returns>
			</method>

			<method name="add_thread">
				<type>void</type>
				
				<parameter name="thrd">
					<paramtype><classname>thread</classname>* thrd</paramtype>
				</parameter>
				
				<effects>Adds <code>thrd</code> to the 
				<classname>thread_group</classname> object's list of managed 
				<classname>thread</classname> objects. The <code>thrd</code> 
				object must have been allocated via <code>operator new</code> and will 
				be deleted when the group is destroyed.</effects>
			</method>

			<method name="remove_thread">
				<type>void</type>
				
				<parameter name="thrd">
					<paramtype><classname>thread</classname>* thrd</paramtype>
				</parameter>
				
				<effects>Removes <code>thread</code> from <code>*this</code>'s
				list of managed <classname>thread</classname> objects.</effects>
				
				<throws><emphasis role="bold">???</emphasis> if 
				<code>thrd</code> is not in <code>*this</code>'s list
				of managed <classname>thread</classname> objects.</throws>
			</method>

			<method name="join_all">
				<type>void</type>
				
				<effects>Calls <code>join()</code> on each of the managed 
				<classname>thread</classname> objects.</effects>
			</method>
		</method-group>
	</class>
  </namespace>
</header>
