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<a name="source_node_cls"><!-- --></a>
<h1 class="topictitle1">source_node Class</h1>
<div>
<div class="section"><h2 class="sectiontitle">Summary</h2>
<p>A template class that is both a
<span class="keyword">graph_node</span> and a
<span class="keyword">sender<Output></span>. This node can have no
predecessors. It executes a user-provided
<span class="option">body</span> function object to generate messages that are
broadcast to all successors. It is a serial node and will never call its
<span class="keyword">body</span> concurrently. It is able to buffer a single item.
If no successor accepts an item that it has generated, the message is buffered
and will be provided to successors before a new item is generated.
</p>
</div>
<div class="section"><h2 class="sectiontitle">Syntax</h2>
<pre>template < typename Output > class source_node;</pre>
</div>
<div class="section"><h2 class="sectiontitle">Header</h2>
<pre>#include "tbb/flow_graph.h"</pre>
</div>
<div class="section"><h2 class="sectiontitle">Description</h2>
<p>This type of node generates messages of type
<span class="keyword">Output</span> by invoking the user-provided
<span class="keyword">body</span> and broadcasts the result to all of its
successors.
</p>
<p>A
<span class="keyword">source_node</span> is a serial node. Calls to
<span class="keyword">body</span> will never be made concurrently.
</p>
<p>A
<span class="keyword">source_node</span> will continue to invoke
<span class="keyword">body</span> and broadcast messages until the
<span class="keyword">body</span> returns
<span class="keyword">false</span> or it has no valid successors. A message may
be generated and then rejected by all successors. In that case, the message is
buffered and will be the next message sent once a successor is added to the
node or
<span class="keyword">try_get</span> is called. Calls to
<span class="keyword">try_get</span> will return a buffer message if available or
will invoke
<span class="keyword">body</span> to attempt to generate a new message. A call to
<span class="keyword">body</span> is made only when the internal buffer is empty.
</p>
<p>Rejection of messages by successors is handled using the protocol in
the Message Passing Protocol, see link below.
</p>
<div class="tablenoborder"><a name="tbl25"><!-- --></a><table cellpadding="4" summary="" id="tbl25" frame="border" border="1" cellspacing="0" rules="all"><caption><span class="tablecap">source_node<Output> Body Concept</span></caption>
<thead align="left">
<tr>
<th class="cellrowborder" align="center" valign="top" width="50%" id="d85476e126">
<p>Pseudo-Signature
</p>
</th>
<th class="cellrowborder" align="center" valign="top" width="50%" id="d85476e132">
<p>Semantics
</p>
</th>
</tr>
</thead>
<tbody>
<tr>
<td class="cellrowborder" valign="top" width="50%" headers="d85476e126 ">
<p>
<pre>B::B( const B& )</pre>
</p>
</td>
<td class="cellrowborder" valign="top" width="50%" headers="d85476e132 ">
<p>Copy constructor.
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="50%" headers="d85476e126 ">
<p>
<pre>B::~B()</pre>
</p>
</td>
<td class="cellrowborder" valign="top" width="50%" headers="d85476e132 ">
<p>Destructor.
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="50%" headers="d85476e126 ">
<p>
<pre>void operator=( const B& )</pre>
</p>
</td>
<td class="cellrowborder" valign="top" width="50%" headers="d85476e132 ">
<p>Assignment. The return type
<samp class="codeph">void</samp> in the pseudo-signature denotes that
<samp class="codeph">operator=</samp> is not required to return a value.
The actual
<samp class="codeph">operator=</samp> can return a value, which will be
ignored.
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="50%" headers="d85476e126 ">
<p>
<pre>bool B::operator() (Output &v)</pre>
</p>
</td>
<td class="cellrowborder" valign="top" width="50%" headers="d85476e132 ">
<p>Returns
<span class="keyword">true</span> when it has assigned a new value to
<span class="keyword">v</span>. Returns
<span class="keyword">false</span> when no new values may be generated.
</p>
</td>
</tr>
</tbody>
</table>
</div>
<div class="Note"><h3 class="NoteTipHead">
Caution</h3>
<p> The body object passed to a
<span class="keyword">source_node</span> is copied. Therefore updates to member
variables will not affect the original object used to construct the node. If
the state held within a body object must be inspected from outside of the node,
the
<span class="keyword">copy_body</span> function can be used to obtain an
updated copy.
</p>
</div>
<div class="Note"><h3 class="NoteTipHead">
Note</h3>
<p> The body object may throw or cancel its enclosing graph. See
task_group_context and Exceptions sections for a description.
</p>
<p><span class="keyword">Output</span> must be copy-constructible and assignable.
</p>
</div>
</div>
<div class="section"><h2 class="sectiontitle">Members</h2>
<pre>namespace tbb {
namespace flow {
template < typename Output >
class source_node : public graph_node, public sender< Output > {
public:
typedef Output output_type;
typedef receiver< output_type > successor_type;
template< typename Body >
source_node( graph &g, Body body, bool is_active = true );
source_node( const source_node &src );
~source_node();
void activate();
bool register_successor( successor_type &r );
bool remove_successor( successor_type &r );
bool try_get( output_type &v );
bool try_reserve( output_type &v );
bool try_release( );
bool try_consume( );
};
}
}</pre>
<div class="tablenoborder"><table cellpadding="4" summary="" frame="border" border="1" cellspacing="0" rules="all"><span class="tabledesc">The following table provides additional information on the
members of this class.
</span><thead align="left">
<tr>
<th class="cellrowborder" valign="top" width="33.89830508474576%" id="d85476e278">Member
</th>
<th class="cellrowborder" valign="top" width="66.10169491525423%" id="d85476e281">Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">template< typename Body
>source_node( graph &g, Body body, bool is_active=true )</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Constructs a
<span class="keyword">source_node</span> that will invoke
<span class="keyword">body</span>. By default the node is created in
the active state, that is, it will begin generating messages immediately. If
<span class="keyword">is_active</span> is
<span class="keyword">false</span>, messages will not be generated
until a call to
<span class="keyword">activate</span> is made.
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">source_node( const source_node
&src )</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Constructs a
<span class="keyword">source_node</span> that has the same initial
state that
<span class="keyword">src</span> had when it was constructed. The
<span class="keyword">source_node</span> that is constructed will have
a reference to the same
<span class="keyword">graph</span> object as
<span class="keyword">src</span>, will have a copy of the initial body
used by
<span class="keyword">src,</span> and have the same initial active
state as
<span class="keyword">src</span>. The predecessors and successors of
<span class="keyword">src</span> will not be copied.
</p>
<div class="Note"><h3 class="NoteTipHead">
Caution</h3>
<p> The new body object is copy constructed from a copy of
the original body provided to
<span class="keyword">src</span> at its construction. Therefore
changes made to member variables in
<span class="keyword">src</span>'s body after the construction of
<span class="keyword">src</span> will not affect the body of the new
<span class="keyword">source_node.</span>
</p>
</div>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">void activate()</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Sets the
<span class="keyword">source_node</span> to the active state, allowing
it to begin generating messages.
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">bool register_successor(
successor_type &r )</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Adds
<span class="keyword">r</span> to the set of successors.
</p>
<p><strong>Returns</strong>:
<span class="keyword">true</span>
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">bool remove_successor(
successor_type &r )</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Removes
<span class="keyword">r</span> from the set of successors.
</p>
<p><strong>Returns</strong>:
<span class="keyword">true</span>
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">bool try_get( output_type &v
)</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Will copy the buffered message into
<span class="keyword">v</span> if available or will invoke
<span class="keyword">body</span> to attempt to generate a new message
that will be copied into
<span class="keyword">v</span>.
</p>
<p><strong>Returns</strong>:<span class="keyword">true</span> if a message is
copied to v.
<span class="keyword">false</span> otherwise.
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">bool try_reserve( output_type
&v )</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Reserves the
<span class="keyword">source_node</span> if possible. If a message can
be buffered and the node is not already reserved, the node is reserved for the
caller, and the value is copied into
<span class="keyword">v</span>.
</p>
<p><strong>Returns</strong>:
<span class="keyword">true</span> if the node is reserved for the
caller.
<span class="keyword">false</span> otherwise.
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">bool try_release( )</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Releases any reservation held on the
<span class="keyword">source_node</span>. The message held in the
internal buffer is retained.
</p>
<p><strong>Returns</strong>:
<span class="keyword">true</span>
</p>
</td>
</tr>
<tr>
<td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d85476e278 "><span class="keyword">bool try_consume( )</span>
</td>
<td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d85476e281 ">
<p>Releases any reservation held on the
<span class="keyword">source_node</span> and clears the internal
buffer.
</p>
<p><strong>Returns</strong>:
<span class="keyword">true</span>
</p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
</div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="../../reference/flow_graph.htm">Flow Graph</a></div>
</div>
<div class="See Also">
<h2>See Also</h2>
<div class="linklist">
<div><a href="make_edge_func.htm">make_edge Template Function
</a></div>
<div><a href="remove_edge_func.htm">remove_edge Template Function
</a></div>
<div><a href="copy_body_func.htm">copy_body Template Function
</a></div>
<div><a href="message_passing_protocol.htm">Message Passing Protocol
</a></div>
<div><a href="../task_scheduler/task_group_context.htm">task_group_context
</a></div>
<div><a href="../exceptions.htm">Exceptions
</a></div></div>
</div>
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