FreeRTOS Tetris
Macros | Functions
Queue Receiving

Group that contains macros & functions for receiving queue data. More...

Collaboration diagram for Queue Receiving:

Macros

#define xQueuePeek(xQueue, pvBuffer, xTicksToWait)   xQueueGenericReceive( ( xQueue ), ( pvBuffer ), ( xTicksToWait ), pdTRUE )
 
#define xQueueReceive(xQueue, pvBuffer, xTicksToWait)   xQueueGenericReceive( ( xQueue ), ( pvBuffer ), ( xTicksToWait ), pdFALSE )
 

Functions

BaseType_t xQueueGenericReceive (QueueHandle_t xQueue, void *const pvBuffer, TickType_t xTicksToWait, const BaseType_t xJustPeek) PRIVILEGED_FUNCTION
 

Detailed Description

Group that contains macros & functions for receiving queue data.

Macro Definition Documentation

◆ xQueuePeek

#define xQueuePeek (   xQueue,
  pvBuffer,
  xTicksToWait 
)    xQueueGenericReceive( ( xQueue ), ( pvBuffer ), ( xTicksToWait ), pdTRUE )

#include <queue.h>

QueueHandle_t xQueue,
void *pvBuffer,
TickType_t xTicksToWait
);

This is a macro that calls the xQueueGenericReceive() function.

Receive an item from a queue without removing the item from the queue. The item is received by copy so a buffer of adequate size must be provided. The number of bytes copied into the buffer was defined when the queue was created.

Successfully received items remain on the queue so will be returned again by the next call, or a call to xQueueReceive().

This macro must not be used in an interrupt service routine. See xQueuePeekFromISR() for an alternative that can be called from an interrupt service routine.

Parameters
xQueueThe handle to the queue from which the item is to be received.
pvBufferPointer to the buffer into which the received item will be copied.
xTicksToWaitThe maximum amount of time the task should block waiting for an item to receive should the queue be empty at the time of the call. The time is defined in tick periods so the constant portTICK_PERIOD_MS should be used to convert to real time if this is required. xQueuePeek() will return immediately if xTicksToWait is 0 and the queue is empty.
Returns
pdTRUE if an item was successfully received from the queue, otherwise pdFALSE.

Example usage:

struct AMessage
{
char ucMessageID;
char ucData[ 20 ];
} xMessage;
// Task to create a queue and post a value.
void vATask( void *pvParameters )
{
struct AMessage *pxMessage;
// Create a queue capable of containing 10 pointers to AMessage structures.
// These should be passed by pointer as they contain a lot of data.
xQueue = xQueueCreate( 10, sizeof( struct AMessage * ) );
if( xQueue == 0 )
{
// Failed to create the queue.
}
// ...
// Send a pointer to a struct AMessage object. Don't block if the
// queue is already full.
pxMessage = & xMessage;
xQueueSend( xQueue, ( void * ) &pxMessage, ( TickType_t ) 0 );
// ... Rest of task code.
}
// Task to peek the data from the queue.
void vADifferentTask( void *pvParameters )
{
struct AMessage *pxRxedMessage;
if( xQueue != 0 )
{
// Peek a message on the created queue. Block for 10 ticks if a
// message is not immediately available.
if( xQueuePeek( xQueue, &( pxRxedMessage ), ( TickType_t ) 10 ) )
{
// pcRxedMessage now points to the struct AMessage variable posted
// by vATask, but the item still remains on the queue.
}
}
// ... Rest of task code.
}

◆ xQueueReceive

#define xQueueReceive (   xQueue,
  pvBuffer,
  xTicksToWait 
)    xQueueGenericReceive( ( xQueue ), ( pvBuffer ), ( xTicksToWait ), pdFALSE )

#include <queue.h>

QueueHandle_t xQueue,
void *pvBuffer,
TickType_t xTicksToWait
);

This is a macro that calls the xQueueGenericReceive() function.

Receive an item from a queue. The item is received by copy so a buffer of adequate size must be provided. The number of bytes copied into the buffer was defined when the queue was created.

Successfully received items are removed from the queue.

This function must not be used in an interrupt service routine. See xQueueReceiveFromISR for an alternative that can.

Parameters
xQueueThe handle to the queue from which the item is to be received.
pvBufferPointer to the buffer into which the received item will be copied.
xTicksToWaitThe maximum amount of time the task should block waiting for an item to receive should the queue be empty at the time of the call. xQueueReceive() will return immediately if xTicksToWait is zero and the queue is empty. The time is defined in tick periods so the constant portTICK_PERIOD_MS should be used to convert to real time if this is required.
Returns
pdTRUE if an item was successfully received from the queue, otherwise pdFALSE.

Example usage:

struct AMessage
{
char ucMessageID;
char ucData[ 20 ];
} xMessage;
// Task to create a queue and post a value.
void vATask( void *pvParameters )
{
struct AMessage *pxMessage;
// Create a queue capable of containing 10 pointers to AMessage structures.
// These should be passed by pointer as they contain a lot of data.
xQueue = xQueueCreate( 10, sizeof( struct AMessage * ) );
if( xQueue == 0 )
{
// Failed to create the queue.
}
// ...
// Send a pointer to a struct AMessage object. Don't block if the
// queue is already full.
pxMessage = & xMessage;
xQueueSend( xQueue, ( void * ) &pxMessage, ( TickType_t ) 0 );
// ... Rest of task code.
}
// Task to receive from the queue.
void vADifferentTask( void *pvParameters )
{
struct AMessage *pxRxedMessage;
if( xQueue != 0 )
{
// Receive a message on the created queue. Block for 10 ticks if a
// message is not immediately available.
if( xQueueReceive( xQueue, &( pxRxedMessage ), ( TickType_t ) 10 ) )
{
// pcRxedMessage now points to the struct AMessage variable posted
// by vATask.
}
}
// ... Rest of task code.
}

Function Documentation

◆ xQueueGenericReceive()

BaseType_t xQueueGenericReceive ( QueueHandle_t  xQueue,
void *const  pvBuffer,
TickType_t  xTicksToWait,
const BaseType_t  xJustPeek 
)

#include <queue.h>

QueueHandle_t xQueue,
void *pvBuffer,
TickType_t xTicksToWait
BaseType_t xJustPeek
);

It is preferred that the macro xQueueReceive() be used rather than calling this function directly.

Receive an item from a queue. The item is received by copy so a buffer of adequate size must be provided. The number of bytes copied into the buffer was defined when the queue was created.

This function must not be used in an interrupt service routine. See xQueueReceiveFromISR for an alternative that can.

Parameters
xQueueThe handle to the queue from which the item is to be received.
pvBufferPointer to the buffer into which the received item will be copied.
xTicksToWaitThe maximum amount of time the task should block waiting for an item to receive should the queue be empty at the time of the call. The time is defined in tick periods so the constant portTICK_PERIOD_MS should be used to convert to real time if this is required. xQueueGenericReceive() will return immediately if the queue is empty and xTicksToWait is 0.
xJustPeekWhen set to true, the item received from the queue is not actually removed from the queue - meaning a subsequent call to xQueueReceive() will return the same item. When set to false, the item being received from the queue is also removed from the queue.
Returns
pdTRUE if an item was successfully received from the queue, otherwise pdFALSE.

Example usage:

struct AMessage
{
char ucMessageID;
char ucData[ 20 ];
} xMessage;
// Task to create a queue and post a value.
void vATask( void *pvParameters )
{
struct AMessage *pxMessage;
// Create a queue capable of containing 10 pointers to AMessage structures.
// These should be passed by pointer as they contain a lot of data.
xQueue = xQueueCreate( 10, sizeof( struct AMessage * ) );
if( xQueue == 0 )
{
// Failed to create the queue.
}
// ...
// Send a pointer to a struct AMessage object. Don't block if the
// queue is already full.
pxMessage = & xMessage;
xQueueSend( xQueue, ( void * ) &pxMessage, ( TickType_t ) 0 );
// ... Rest of task code.
}
// Task to receive from the queue.
void vADifferentTask( void *pvParameters )
{
struct AMessage *pxRxedMessage;
if( xQueue != 0 )
{
// Receive a message on the created queue. Block for 10 ticks if a
// message is not immediately available.
if( xQueueGenericReceive( xQueue, &( pxRxedMessage ), ( TickType_t ) 10 ) )
{
// pcRxedMessage now points to the struct AMessage variable posted
// by vATask.
}
}
// ... Rest of task code.
}
xQueueGenericReceive
BaseType_t xQueueGenericReceive(QueueHandle_t xQueue, void *const pvBuffer, TickType_t xTicksToWait, const BaseType_t xJustPeek) PRIVILEGED_FUNCTION
Definition: queue.c:1275
TickType_t
uint32_t TickType_t
FreeRTOS definition for a single tick.
Definition: portmacro.h:98
QueueHandle_t
void * QueueHandle_t
Definition: queue.h:135
BaseType_t
long BaseType_t
FreeRTOS definition for long ints.
Definition: portmacro.h:91
xQueueReceive
#define xQueueReceive(xQueue, pvBuffer, xTicksToWait)
Definition: queue.h:1314
xQueueCreate
#define xQueueCreate(uxQueueLength, uxItemSize)
Definition: queue.h:237
xQueueSend
#define xQueueSend(xQueue, pvItemToQueue, xTicksToWait)
Definition: queue.h:440
xQueuePeek
#define xQueuePeek(xQueue, pvBuffer, xTicksToWait)
Definition: queue.h:1223