Class template spsc_queue

boost::lockfree::spsc_queue

Synopsis

// In header: <boost/lockfree/spsc_queue.hpp>

template<typename T, typename A0, typename A1> 
class spsc_queue {
public:
  // types
  typedef T                                 value_type;
  typedef implementation_defined::allocator allocator; 
  typedef implementation_defined::size_type size_type; 

  // member classes/structs/unions
  template<typename T, typename ... Options> 
  struct implementation_defined {
    // types
    typedef allocator_arg allocator;
    typedef std::size_t   size_type;
  };

  // construct/copy/destruct
  spsc_queue(void);
  template<typename U> 
    explicit spsc_queue(typename boost::allocator_rebind< allocator, U >::type const &);
  explicit spsc_queue(allocator const &);
  explicit spsc_queue(size_type);
  template<typename U> 
    spsc_queue(size_type, 
               typename boost::allocator_rebind< allocator, U >::type const &);
  spsc_queue(size_type, allocator_arg const &);

  // public member functions
  bool push(T const &);
  bool pop();
  template<typename U> 
    boost::enable_if< typename is_convertible< T, U >::type, bool >::type 
    pop(U &);
  size_type push(T const *, size_type);
  template<size_type size> size_type push(T const (&));
  template<typename ConstIterator> 
    ConstIterator push(ConstIterator, ConstIterator);
  size_type pop(T *, size_type);
  template<size_type size> size_type pop(T(&));
  template<typename OutputIterator> 
    boost::disable_if< typename is_convertible< T, OutputIterator >::type, size_type >::type 
    pop(OutputIterator);
  template<typename Functor> bool consume_one(Functor &);
  template<typename Functor> bool consume_one(Functor const &);
  template<typename Functor> size_type consume_all(Functor &);
  template<typename Functor> size_type consume_all(Functor const &);
  size_type read_available() const;
  size_type write_available() const;
  const T & front() const;
  T & front();
  void reset(void);
};

Description

The spsc_queue class provides a single-writer/single-reader fifo queue, pushing and popping is wait-free.

Policies:

boost::lockfree::capacity<>, optional
If this template argument is passed to the options, the size of the ringbuffer is set at compile-time.
boost::lockfree::allocator<>, defaults to boost::lockfree::allocator<std::allocator<T>>
Specifies the allocator that is used to allocate the ringbuffer. This option is only valid, if the ringbuffer is configured to be sized at run-time

Requirements:

T must have a default constructor
T must be copyable

`spsc_queue` public construct/copy/destruct

```
spsc_queue(void);
```
Constructs a spsc_queue

Requires:

spsc_queue must be configured to be sized at compile-time
```
template<typename U> 
  explicit spsc_queue(typename boost::allocator_rebind< allocator, U >::type const &);
```
Constructs a spsc_queue with a custom allocator

Note

This is just for API compatibility: an allocator isn't actually needed

Requires:

spsc_queue must be configured to be sized at compile-time
```
explicit spsc_queue(allocator const &);
```
Constructs a spsc_queue with a custom allocator

Note

This is just for API compatibility: an allocator isn't actually needed

Requires:

spsc_queue must be configured to be sized at compile-time
```
explicit spsc_queue(size_type element_count);
```
Constructs a spsc_queue for element_count elements

Requires:

spsc_queue must be configured to be sized at run-time

template<typename U> 
  spsc_queue(size_type element_count, 
             typename boost::allocator_rebind< allocator, U >::type const & alloc);

Constructs a spsc_queue for element_count elements with a custom allocator

Requires:

spsc_queue must be configured to be sized at run-time

```
spsc_queue(size_type element_count, allocator_arg const & alloc);
```
Constructs a spsc_queue for element_count elements with a custom allocator

Requires:

spsc_queue must be configured to be sized at run-time

`spsc_queue` public member functions

bool push(T const & t);

Pushes object t to the ringbuffer.

	Note
	Thread-safe and wait-free

Requires:	only one thread is allowed to push data to the spsc_queue
Postconditions:	object will be pushed to the spsc_queue, unless it is full.
Returns:	true, if the push operation is successful.

bool pop();

Pops one object from ringbuffer.

	Note
	Thread-safe and wait-free

Requires:	only one thread is allowed to pop data to the spsc_queue
Postconditions:	if ringbuffer is not empty, object will be discarded.
Returns:	true, if the pop operation is successful, false if ringbuffer was empty.

template<typename U> 
  boost::enable_if< typename is_convertible< T, U >::type, bool >::type 
  pop(U & ret);

Pops one object from ringbuffer.

	Note
	Thread-safe and wait-free

Requires:	only one thread is allowed to pop data to the spsc_queue
Postconditions:	if ringbuffer is not empty, object will be copied to ret.
Returns:	true, if the pop operation is successful, false if ringbuffer was empty.

```
size_type push(T const * t, size_type size);
```
Pushes as many objects from the array t as there is space.

Note

Thread-safe and wait-free

Requires:

only one thread is allowed to push data to the spsc_queue

Returns:

number of pushed items
```
template<size_type size> size_type push(T const (&) t);
```
Pushes as many objects from the array t as there is space available.

Note

Thread-safe and wait-free

Requires:

only one thread is allowed to push data to the spsc_queue

Returns:

number of pushed items
```
template<typename ConstIterator> 
  ConstIterator push(ConstIterator begin, ConstIterator end);
```
Pushes as many objects from the range [begin, end) as there is space .

Note

Thread-safe and wait-free

Requires:

only one thread is allowed to push data to the spsc_queue

Returns:

iterator to the first element, which has not been pushed
```
size_type pop(T * ret, size_type size);
```
Pops a maximum of size objects from ringbuffer.

Note

Thread-safe and wait-free

Requires:

only one thread is allowed to pop data to the spsc_queue

Returns:

number of popped items
```
template<size_type size> size_type pop(T(&) ret);
```
Pops a maximum of size objects from spsc_queue.

Note

Thread-safe and wait-free

Requires:

only one thread is allowed to pop data to the spsc_queue

Returns:

number of popped items

template<typename OutputIterator> 
  boost::disable_if< typename is_convertible< T, OutputIterator >::type, size_type >::type 
  pop(OutputIterator it);

Pops objects to the output iterator it

	Note
	Thread-safe and wait-free

Requires:	only one thread is allowed to pop data to the spsc_queue
Returns:	number of popped items

```
template<typename Functor> bool consume_one(Functor & f);
```
consumes one element via a functor

pops one element from the queue and applies the functor on this object

Note

Thread-safe and non-blocking, if functor is thread-safe and non-blocking

Returns:

true, if one element was consumed
```
template<typename Functor> bool consume_one(Functor const & f);
```
consumes one element via a functor

pops one element from the queue and applies the functor on this object

Note

Thread-safe and non-blocking, if functor is thread-safe and non-blocking

Returns:

true, if one element was consumed
```
template<typename Functor> size_type consume_all(Functor & f);
```
consumes all elements via a functor

sequentially pops all elements from the queue and applies the functor on each object

Note

Thread-safe and non-blocking, if functor is thread-safe and non-blocking

Returns:

number of elements that are consumed
```
template<typename Functor> size_type consume_all(Functor const & f);
```
consumes all elements via a functor

sequentially pops all elements from the queue and applies the functor on each object

Note

Thread-safe and non-blocking, if functor is thread-safe and non-blocking

Returns:

number of elements that are consumed
```
size_type read_available() const;
```
get number of elements that are available for read

Note

Thread-safe and wait-free, should only be called from the consumer thread

Returns:

number of available elements that can be popped from the spsc_queue
```
size_type write_available() const;
```
get write space to write elements

Note

Thread-safe and wait-free, should only be called from the producer thread

Returns:

number of elements that can be pushed to the spsc_queue

const T & front() const;

get reference to element in the front of the queue

Availability of front element can be checked using read_available().

	Note
	Thread-safe and wait-free

Requires:	only a consuming thread is allowed to check front element
Requires:	read_available() > 0. If ringbuffer is empty, it's undefined behaviour to invoke this method.
Returns:	reference to the first element in the queue

T & front();

get reference to element in the front of the queue

Availability of front element can be checked using read_available().

	Note
	Thread-safe and wait-free

Requires:	only a consuming thread is allowed to check front element
Requires:	read_available() > 0. If ringbuffer is empty, it's undefined behaviour to invoke this method.
Returns:	reference to the first element in the queue

```
void reset(void);
```
reset the ringbuffer

Note

Not thread-safe

	Note
	This is just for API compatibility: an allocator isn't actually needed

	Note
	Thread-safe and non-blocking, if functor is thread-safe and non-blocking

	Note
	Thread-safe and wait-free, should only be called from the consumer thread

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