Queues of buffer headers

Typedefs
typedef struct MMAL_QUEUE_T	MMAL_QUEUE_T

Functions
MMAL_QUEUE_T *	mmal_queue_create (void)
void	mmal_queue_put (MMAL_QUEUE_T *queue, MMAL_BUFFER_HEADER_T *buffer)
void	mmal_queue_put_back (MMAL_QUEUE_T *queue, MMAL_BUFFER_HEADER_T *buffer)
MMAL_BUFFER_HEADER_T *	mmal_queue_get (MMAL_QUEUE_T *queue)
MMAL_BUFFER_HEADER_T *	mmal_queue_wait (MMAL_QUEUE_T *queue)
MMAL_BUFFER_HEADER_T *	mmal_queue_timedwait (MMAL_QUEUE_T *queue, VCOS_UNSIGNED timeout)
unsigned int	mmal_queue_length (MMAL_QUEUE_T *queue)
void	mmal_queue_destroy (MMAL_QUEUE_T *queue)

Detailed Description

This provides a thread-safe implementation of a queue of buffer headers (MMAL_BUFFER_HEADER_T). The queue works in a first-in, first-out basis so the buffer headers will be dequeued in the order they have been queued.

Typedef Documentation

MMAL_QUEUE_T

typedef struct MMAL_QUEUE_T MMAL_QUEUE_T

Definition at line 43 of file mmal_queue.h.

Function Documentation

mmal_queue_create()

MMAL_QUEUE_T* mmal_queue_create

(

void

)

Create a queue of MMAL_BUFFER_HEADER_T

Returns

Pointer to the newly created queue or NULL on failure.

mmal_queue_destroy()

void mmal_queue_destroy

(

MMAL_QUEUE_T *

queue

)

Destroy a queue of MMAL_BUFFER_HEADER_T.

Parameters

queue

Pointer to a queue

mmal_queue_get()

MMAL_BUFFER_HEADER_T* mmal_queue_get

(

MMAL_QUEUE_T *

queue

)

Get a MMAL_BUFFER_HEADER_T from a queue

Parameters

queue

Pointer to a queue

Returns

pointer to the next MMAL_BUFFER_HEADER_T or NULL if the queue is empty.

mmal_queue_length()

unsigned int mmal_queue_length

(

MMAL_QUEUE_T *

queue

)

Get the number of MMAL_BUFFER_HEADER_T currently in a queue.

Parameters

queue

Pointer to a queue

Returns

length (in elements) of the queue.

mmal_queue_put()

void mmal_queue_put	(	MMAL_QUEUE_T *	queue,
		MMAL_BUFFER_HEADER_T *	buffer
	)

Put a MMAL_BUFFER_HEADER_T into a queue

Parameters

queue	Pointer to a queue
buffer	Pointer to the MMAL_BUFFER_HEADER_T to add to the queue

mmal_queue_put_back()

void mmal_queue_put_back	(	MMAL_QUEUE_T *	queue,
		MMAL_BUFFER_HEADER_T *	buffer
	)

Put a MMAL_BUFFER_HEADER_T back at the start of a queue. This is used when a buffer header was removed from the queue but not fully processed and needs to be put back where it was originally taken.

Parameters

queue	Pointer to a queue
buffer	Pointer to the MMAL_BUFFER_HEADER_T to add to the queue

mmal_queue_timedwait()

MMAL_BUFFER_HEADER_T* mmal_queue_timedwait	(	MMAL_QUEUE_T *	queue,
		VCOS_UNSIGNED	timeout
	)

Wait for a MMAL_BUFFER_HEADER_T from a queue, up to a given timeout. This is the same as a wait, except that it will abort in case of timeout.

Parameters

queue	Pointer to a queue
timeout	Number of milliseconds to wait before returning if the semaphore can't be acquired.

Returns

pointer to the next MMAL_BUFFER_HEADER_T.

mmal_queue_wait()

MMAL_BUFFER_HEADER_T* mmal_queue_wait

(

MMAL_QUEUE_T *

queue

)

Wait for a MMAL_BUFFER_HEADER_T from a queue. This is the same as a get except that this will block until a buffer header is available.

Parameters

queue

Pointer to a queue

Returns

pointer to the next MMAL_BUFFER_HEADER_T.