OS_FIFO Struct Reference

A linked-list FIFO for passing pointers to user-defined structures between tasks. More...

#include <nbrtos.h>

Inherits OS_TASK_DLY_OBJ.

Public Member Functions
	OS_FIFO ()
	Construct and initialize the FIFO (empty linked list).
uint8_t	Init ()
	Reset the FIFO to its initial (empty) state.
uint8_t	Post (OS_FIFO_EL *pToPost)
	Post an element to the tail of the FIFO.
uint8_t	PostFirst (OS_FIFO_EL *pToPost)
	Post an element to the head of the FIFO (priority insertion).
OS_FIFO_EL *	Pend (uint32_t timeoutTicks, uint8_t &result)
	Wait for an element to be posted to the FIFO.
OS_FIFO_EL *	Pend (TickTimeout &t, uint8_t &result)
	Wait for an element to be posted to the FIFO, using a TickTimeout.
OS_FIFO_EL *	Pend (uint32_t timeoutTicks=WAIT_FOREVER)
	Wait for an element to be posted to the FIFO (no result code).
OS_FIFO_EL *	PendUntil (uint32_t timeoutTime, uint8_t &result)
	Wait until an absolute TimeTick value for an element to be posted.
OS_FIFO_EL *	PendNoWait (uint8_t &result)
	Retrieve an element from the FIFO without waiting.
OS_FIFO_EL *	PendNoWait ()
	Retrieve an element from the FIFO without waiting (no result code).

Detailed Description

A linked-list FIFO for passing pointers to user-defined structures between tasks.

Unlike OS_Q (which stores void pointers in a fixed-size array), OS_FIFO uses a linked list so there is no predefined capacity limit. Each element posted must begin with an OS_FIFO_EL-compatible header (a pointer used internally to link elements together). Your application is responsible for allocating the elements, either statically or from the heap.

Elements are extracted in FIFO order (first posted = first retrieved), unless PostFirst() is used to insert at the head.

Note

If you only need to pass simple pointer-sized values, OS_Q may be simpler.

See also

OS_Q, OS_FIFO_EL, TEMPL_FIFO

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Expand for Example Usage

Examples

Pass a Structure Between Tasks

struct MyMessage
{
    OS_FIFO_EL link;   // Must be the first member
    int        data;
};
 
OS_FIFO gFifo;
MyMessage gMsg;
 
void ProducerTask(void *pd)
{
    gMsg.data = 42;
    gFifo.Post((OS_FIFO_EL *)&gMsg);
}
 
void ConsumerTask(void *pd)
{
    OS_FIFO_EL *pEl = gFifo.Pend(5 * TICKS_PER_SECOND);
    if (pEl != NULL)
    {
        MyMessage *pMsg = (MyMessage *)pEl;
        iprintf("Received data: %d\r\n", pMsg->data);
    }
}

---

Constructor & Destructor Documentation

OS_FIFO()

OS_FIFO::OS_FIFO ( )

inline

Construct and initialize the FIFO (empty linked list).

See also

Init()

Member Function Documentation

Init()

uint8_t OS_FIFO::Init

(

)

Reset the FIFO to its initial (empty) state.

Return values

OS_NO_ERR

If successful.

See also

NBRTOS Error Codes

Pend() [1/3]

OS_FIFO_EL * OS_FIFO::Pend	(	TickTimeout &	t,
		uint8_t &	result )

Wait for an element to be posted to the FIFO, using a TickTimeout.

Parameters

t	TickTimeout controlling the maximum wait duration.
result	Receives OS_NO_ERR on success or OS_TIMEOUT on timeout.

Returns

Pointer to the retrieved OS_FIFO_EL, or NULL on timeout.

See also

PendNoWait(), PendUntil(), NBRTOS Error Codes

Pend() [2/3]

OS_FIFO_EL * OS_FIFO::Pend ( uint32_t timeoutTicks, uint8_t & result )

inline

Wait for an element to be posted to the FIFO.

Parameters

timeoutTicks	Maximum system ticks to wait. A value of 0 waits forever.
result	Receives OS_NO_ERR on success or OS_TIMEOUT on timeout.

Returns

Pointer to the retrieved OS_FIFO_EL, or NULL on timeout.

See also

PendNoWait(), PendUntil(), NBRTOS Error Codes

Pend() [3/3]

OS_FIFO_EL * OS_FIFO::Pend ( uint32_t timeoutTicks = WAIT_FOREVER )

inline

Wait for an element to be posted to the FIFO (no result code).

Parameters

timeoutTicks

Maximum system ticks to wait. A value of 0 (default) waits forever.

Returns

Pointer to the retrieved OS_FIFO_EL, or NULL on timeout.

See also

PendNoWait(), PendUntil(), NBRTOS Error Codes

PendNoWait() [1/2]

OS_FIFO_EL * OS_FIFO::PendNoWait ( )

inline

Retrieve an element from the FIFO without waiting (no result code).

Returns

Pointer to the retrieved OS_FIFO_EL, or NULL if the FIFO was empty.

See also

Pend(), PendUntil(), NBRTOS Error Codes

PendNoWait() [2/2]

OS_FIFO_EL * OS_FIFO::PendNoWait

(

uint8_t &

result

)

Retrieve an element from the FIFO without waiting.

Parameters

result

Receives OS_NO_ERR if an element was available, or OS_TIMEOUT if empty.

Returns

Pointer to the retrieved OS_FIFO_EL, or NULL if the FIFO was empty.

See also

Pend(), PendUntil(), NBRTOS Error Codes

PendUntil()

OS_FIFO_EL * OS_FIFO::PendUntil ( uint32_t timeoutTime, uint8_t & result )

inline

Wait until an absolute TimeTick value for an element to be posted.

Parameters

timeoutTime	Absolute system TimeTick value at which to stop waiting.
result	Receives OS_NO_ERR on success or OS_TIMEOUT on timeout.

Returns

Pointer to the retrieved OS_FIFO_EL, or NULL on timeout.

See also

Pend(), PendNoWait(), NBRTOS Error Codes

Post()

uint8_t OS_FIFO::Post

(

OS_FIFO_EL *

pToPost

)

Post an element to the tail of the FIFO.

If a higher-priority task is pending on this FIFO, it will be released.

Parameters

pToPost

Pointer to the element (cast as OS_FIFO_EL) to post.

Return values

OS_NO_ERR

If successful.

See also

PostFirst(), Pend()

PostFirst()

uint8_t OS_FIFO::PostFirst

(

OS_FIFO_EL *

pToPost

)

Post an element to the head of the FIFO (priority insertion).

Parameters

pToPost

Pointer to the element (cast as OS_FIFO_EL) to post at the head.

Return values

OS_NO_ERR

If successful.

See also

Post(), Pend()

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The documentation for this struct was generated from the following file:

• nbrtos.h