Intel Threading Building Blocks

Name

Template Class — Template class for queue with concurrent operations.concurrent_queue

Synopsis

#include "tbb/concurrent_queue.h"

template<typename T> class concurrent_queue;

Description

A concurrent_queue is a bounded data structure that permits multiple threads to concurrently push and pop items. Its behavior is first-in first-out in reference to any items pushed by a single thread and popped by a single thread. The default bounds are large enough to make the queue practically unbounded, subject to memory limitations on the target machine.

The interface is different from that of an STL std::queue because concurrent_queue is designed for concurrent operations. See Table 5-1 for the differences.

Table 5-1. std::queue versus tbb::concurrent_queue

Feature	STL std::queue	tbb::concurrent_queue
Access to front and back	front and back methods	Not present. They would be unsafe while concurrent operations are in progress.
size_type	Unsigned integral type	Signed integral type.
size( )	Returns the number of items in the queue	Returns the number of pushes minus the number of pops. Waiting push or pop operations are included in the difference. The size is negative if there are pops waiting for corresponding pushes.
Copy and pop item from queue q	x=q.front( ) q.pop( )	q.pop(x) waits for the object indefinitely. For an immediate return, use pop_if_present.
Copy and pop item unless queue q is empty	bool b=!q.empty( ); if(b) { x=q.front( ); q.pop( ); }	q.pop_if_present(x) ...