# queue_node¶

[flow_graph.queue_node]

A node that forwards messages in a first-in first-out (FIFO) order by maintaining a buffer of messages.

// Defined in header <tbb/flow_graph.h>

namespace tbb {
namespace flow {

template <typename T >
class queue_node : public graph_node, public receiver<T>, public sender<T> {
public:
explicit queue_node( graph &g );
queue_node( const queue_node &src );
~queue_node();

bool try_put( const T &v );
bool try_get( T &v );
};

} // namespace flow
} // namespace tbb


Requirements:

• The type T must meet the CopyConstructible requirements from [copyconstructible] and CopyAssignable requirements from [copyassignable] ISO C++ Standard sections.

queue_node forwards messages in a FIFO order to a single successor in its successor set.

queue_node is a graph_node, receiver and sender.

queue_node has a buffering and single-push properties.

## Member functions¶

explicit queue_node(graph &g)

Constructs an empty queue_node that belongs to the graph g.

queue_node(const queue_node &src)

Constructs an empty queue_node that belongs to the same graph g as src. The list of predecessors, the list of successors, and the messages in the buffer are not copied.

bool try_put(const T &v)

Adds item to internal FIFO buffer. If v is the only item in the queue_node, a task is spawned to forward the item to a successor.

Returns: true.

bool try_get(T &v)

Returns: true if an item can be removed from the front of the queue_node and assigned to v. Returns false if there is no item currently in the queue_node or if the node is reserved.

## Example¶

Usage scenario is similar to buffer_node except that messages are passed in first-in first-out (FIFO) order.