#include <AtomicQueue.hpp>
Classes | |
| union | SIndexes |
Public Types | |
| typedef unsigned int | size_type |
Public Member Functions | |
| AtomicQueue (unsigned int size) | |
| size_type | capacity () const |
| void | clear () |
| bool | dequeue (T &result) |
| bool | enqueue (const T &value) |
| const T | front () const |
| bool | isEmpty () const |
| bool | isFull () const |
| size_type | size () const |
| ~AtomicQueue () | |
Private Types | |
| typedef T | C |
| typedef C *volatile | CacheObjType |
| typedef volatile C * | CachePtrType |
| typedef C * | PtrType |
| typedef C | ValueType |
Private Member Functions | |
| AtomicQueue (const AtomicQueue< T > &) | |
| CachePtrType | propose_r () |
| CachePtrType | propose_w () |
| CachePtrType | recover_r () const |
Private Attributes | |
| CachePtrType | _buf |
| volatile SIndexes | _indxes |
| const int | _size |
Detailed Description
template<class T>
class RTT::internal::AtomicQueue< T >
Create an atomic, non-blocking single ended queue (FIFO) for storing a pointer to T. It is a Many Readers, Many Writers implementation based on the atomic Compare And Swap instruction. Any number of threads may access the queue concurrently.
This queue tries to obey strict ordering, but under high contention of reads interfering writes, one or more elements may be dequeued out of order. For this reason, size() is expensive to accurately calculate the size.
Due to the same limitations, it is possible that the full capacity of the queue is not used (simulations show seldomly an off by one element if capacity==10) and that isFull() returns true, while size() < capacity().
- Warning:
- You can not store null pointers.
- Parameters:
-
T The pointer type to be stored in the Queue. Example : AtomicQueue< A* > is a queue of pointers to A.
Definition at line 70 of file AtomicQueue.hpp.
Member Typedef Documentation
typedef T RTT::internal::AtomicQueue< T >::C [private] |
Definition at line 73 of file AtomicQueue.hpp.
typedef C* volatile RTT::internal::AtomicQueue< T >::CacheObjType [private] |
Definition at line 75 of file AtomicQueue.hpp.
typedef volatile C* RTT::internal::AtomicQueue< T >::CachePtrType [private] |
Definition at line 74 of file AtomicQueue.hpp.
typedef C* RTT::internal::AtomicQueue< T >::PtrType [private] |
Definition at line 77 of file AtomicQueue.hpp.
| typedef unsigned int RTT::internal::AtomicQueue< T >::size_type |
Definition at line 184 of file AtomicQueue.hpp.
typedef C RTT::internal::AtomicQueue< T >::ValueType [private] |
Definition at line 76 of file AtomicQueue.hpp.
Constructor & Destructor Documentation
| RTT::internal::AtomicQueue< T >::AtomicQueue | ( | const AtomicQueue< T > & | ) | [private] |
| RTT::internal::AtomicQueue< T >::AtomicQueue | ( | unsigned int | size | ) | [inline] |
Create an AtomicQueue with queue size size.
- Parameters:
-
size The size of the queue, should be 1 or greater.
Definition at line 190 of file AtomicQueue.hpp.
| RTT::internal::AtomicQueue< T >::~AtomicQueue | ( | ) | [inline] |
Definition at line 197 of file AtomicQueue.hpp.
Member Function Documentation
| size_type RTT::internal::AtomicQueue< T >::capacity | ( | ) | const [inline] |
Return the maximum number of items this queue can contain.
Definition at line 231 of file AtomicQueue.hpp.
| void RTT::internal::AtomicQueue< T >::clear | ( | ) | [inline] |
Clear all contents of the Queue and thus make it empty.
Definition at line 304 of file AtomicQueue.hpp.
| bool RTT::internal::AtomicQueue< T >::dequeue | ( | T & | result | ) | [inline] |
Dequeue an item.
- Parameters:
-
value The value dequeued.
- Returns:
- false if queue is empty, true if dequeued.
Definition at line 278 of file AtomicQueue.hpp.
| bool RTT::internal::AtomicQueue< T >::enqueue | ( | const T & | value | ) | [inline] |
Enqueue an item.
- Parameters:
-
value The value to enqueue, not zero.
- Returns:
- false if queue is full or value is zero, true if queued.
Definition at line 258 of file AtomicQueue.hpp.
| const T RTT::internal::AtomicQueue< T >::front | ( | ) | const [inline] |
Return the next to be read value.
Definition at line 296 of file AtomicQueue.hpp.
| bool RTT::internal::AtomicQueue< T >::isEmpty | ( | ) | const [inline] |
Inspect if the Queue is empty.
- Returns:
- true if empty, false otherwise.
Definition at line 220 of file AtomicQueue.hpp.
| bool RTT::internal::AtomicQueue< T >::isFull | ( | ) | const [inline] |
Inspect if the Queue is full.
- Returns:
- true if full, false otherwise.
Definition at line 206 of file AtomicQueue.hpp.
| CachePtrType RTT::internal::AtomicQueue< T >::propose_r | ( | ) | [inline, private] |
Atomic advance and wrap of the Read pointer. Return the data position or zero if queue is empty.
Definition at line 157 of file AtomicQueue.hpp.
| CachePtrType RTT::internal::AtomicQueue< T >::propose_w | ( | ) | [inline, private] |
Atomic advance and wrap of the Write pointer. Return the old position or zero if queue is full.
Definition at line 131 of file AtomicQueue.hpp.
| CachePtrType RTT::internal::AtomicQueue< T >::recover_r | ( | ) | const [inline, private] |
The loose ordering may cause missed items in our queue which are not pointed at by the read pointer. This function recovers such items from _buf.
- Returns:
- zero if nothing to recover, the location of a lost item otherwise.
Definition at line 104 of file AtomicQueue.hpp.
| size_type RTT::internal::AtomicQueue< T >::size | ( | ) | const [inline] |
Return the exact number of elements in the queue. This is slow because it scans the whole queue.
Definition at line 241 of file AtomicQueue.hpp.
Member Data Documentation
CachePtrType RTT::internal::AtomicQueue< T >::_buf [private] |
The pointer to the buffer can be cached, the contents are volatile.
Definition at line 89 of file AtomicQueue.hpp.
volatile SIndexes RTT::internal::AtomicQueue< T >::_indxes [private] |
The indexes are packed into one double word. Therefore the read and write index can be read and written atomically.
Definition at line 95 of file AtomicQueue.hpp.
const int RTT::internal::AtomicQueue< T >::_size [private] |
Definition at line 72 of file AtomicQueue.hpp.
The documentation for this class was generated from the following file: