/*
FreeRTOS.org V4.1.0 - Copyright (C) 2003-2006 Richard Barry.
This file is part of the FreeRTOS.org distribution.
FreeRTOS.org is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FreeRTOS.org is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FreeRTOS.org; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
A special exception to the GPL can be applied should you wish to distribute
a combined work that includes FreeRTOS.org, without being obliged to provide
the source code for any proprietary components. See the licensing section
of http://www.FreeRTOS.org for full details of how and when the exception
can be applied.
***************************************************************************
See http://www.FreeRTOS.org for documentation, latest information, license
and contact details. Please ensure to read the configuration and relevant
port sections of the online documentation.
***************************************************************************
*/
#ifndef QUEUE_H
#define QUEUE_H
typedef void * xQueueHandle;
/**
* queue. h
*
xQueueHandle xQueueCreate(
unsigned portBASE_TYPE uxQueueLength,
unsigned portBASE_TYPE uxItemSize
);
*
*
* Creates a new queue instance. This allocates the storage required by the
* new queue and returns a handle for the queue.
*
* @param uxQueueLength The maximum number of items that the queue can contain.
*
* @param uxItemSize The number of bytes each item in the queue will require.
* Items are queued by copy, not by reference, so this is the number of bytes
* that will be copied for each posted item. Each item on the queue must be
* the same size.
*
* @return If the queue is successfully create then a handle to the newly
* created queue is returned. If the queue cannot be created then 0 is
* returned.
*
* Example usage:
struct AMessage
{
portCHAR ucMessageID;
portCHAR ucData[ 20 ];
};
void vATask( void *pvParameters )
{
xQueueHandle xQueue1, xQueue2;
// Create a queue capable of containing 10 unsigned long values.
xQueue1 = xQueueCreate( 10, sizeof( unsigned portLONG ) );
if( xQueue1 == 0 )
{
// Queue was not created and must not be used.
}
// Create a queue capable of containing 10 pointers to AMessage structures.
// These should be passed by pointer as they contain a lot of data.
xQueue2 = xQueueCreate( 10, sizeof( struct AMessage * ) );
if( xQueue2 == 0 )
{
// Queue was not created and must not be used.
}
// ... Rest of task code.
}
* \defgroup xQueueCreate xQueueCreate
* \ingroup QueueManagement
*/
xQueueHandle xQueueCreate( unsigned portBASE_TYPE uxQueueLength, unsigned portBASE_TYPE uxItemSize );
/**
* queue. h
*
portBASE_TYPE xQueueSend(
xQueueHandle xQueue,
const void * pvItemToQueue,
portTickType xTicksToWait
);
*
*
* Post an item on a queue. The item is queued by copy, not by reference.
* This function must not be called from an interrupt service routine.
* See xQueueSendFromISR () for an alternative which may be used in an ISR.
*
* @param xQueue The handle to the queue on which the item is to be posted.
*
* @param pvItemToQueue A pointer to the item that is to be placed on the
* queue. The size of the items the queue will hold was defined when the
* queue was created, so this many bytes will be copied from pvItemToQueue
* into the queue storage area.
*
* @param xTicksToWait The maximum amount of time the task should block
* waiting for space to become available on the queue, should it already
* be full. The call will return immediately if this is set to 0. The
* time is defined in tick periods so the constant portTICK_RATE_MS
* should be used to convert to real time if this is required.
*
* @return pdTRUE if the item was successfully posted, otherwise errQUEUE_FULL.
*
* Example usage:
struct AMessage
{
portCHAR ucMessageID;
portCHAR ucData[ 20 ];
} xMessage;
unsigned portLONG ulVar = 10UL;
void vATask( void *pvParameters )
{
xQueueHandle xQueue1, xQueue2;
struct AMessage *pxMessage;
// Create a queue capable of containing 10 unsigned long values.
xQueue1 = xQueueCreate( 10, sizeof( unsigned portLONG ) );
// Create a queue capable of containing 10 pointers to AMessage structures.
// These should be passed by pointer as they contain a lot of data.
xQueue2 = xQueueCreate( 10, sizeof( struct AMessage * ) );
// ...
if( xQueue1 != 0 )
{
// Send an unsigned long. Wait for 10 ticks for space to become
// available if necessary.
if( xQueueSend( xQueue1, ( void * ) &ulVar, ( portTickType ) 10 ) != pdPASS )
{
// Failed to post the message, even after 10 ticks.
}
}
if( xQueue2 != 0 )
{
// Send a pointer to a struct AMessage object. Don't block if the
// queue is already full.
pxMessage = & xMessage;
xQueueSend( xQueue2, ( void * ) &pxMessage, ( portTickType ) 0 );
}
// ... Rest of task code.
}
* \defgroup xQueueSend xQueueSend
* \ingroup QueueManagement
*/
signed portBASE_TYPE xQueueSend( xQueueHandle xQueue, const void * pvItemToQueue, portTickType xTicksToWait );
/**
* queue. h
*
portBASE_TYPE xQueueReceive(
xQueueHandle xQueue,
void *pvBuffer,
portTickType xTicksToWait
);
*
* 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.
*
* @param pxQueue The handle to the queue from which the item is to be
* received.
*
* @param pvBuffer Pointer to the buffer into which the received item will
* be copied.
*
* @param xTicksToWait The 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_RATE_MS should be used to convert to real time if this is required.
*
* @return pdTRUE if an item was successfully received from the queue,
* otherwise pdFALSE.
*
* Example usage:
struct AMessage
{
portCHAR ucMessageID;
portCHAR ucData[ 20 ];
} xMessage;
xQueueHandle xQueue;
// 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, ( portTickType ) 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 ), ( portTickType ) 10 ) )
{
// pcRxedMessage now points to the struct AMessage variable posted
// by vATask.
}
}
// ... Rest of task code.
}
* \defgroup xQueueReceive xQueueReceive
* \ingroup QueueManagement
*/
signed portBASE_TYPE xQueueReceive( xQueueHandle xQueue, void *pvBuffer, portTickType xTicksToWait );
/**
* queue. h
* unsigned portBASE_TYPE uxQueueMessagesWaiting( xQueueHandle xQueue );
*
* Return the number of messages stored in a queue.
*
* @param xQueue A handle to the queue being queried.
*
* @return The number of messages available in the queue.
*
* \page uxQueueMessagesWaiting uxQueueMessagesWaiting
* \ingroup QueueManagement
*/
unsigned portBASE_TYPE uxQueueMessagesWaiting( xQueueHandle xQueue );
/**
* queue. h
* void vQueueDelete( xQueueHandle xQueue );
*
* Delete a queue - freeing all the memory allocated for storing of items
* placed on the queue.
*
* @param xQueue A handle to the queue to be deleted.
*
* \page vQueueDelete vQueueDelete
* \ingroup QueueManagement
*/
void vQueueDelete( xQueueHandle xQueue );
/**
* queue. h
*
portBASE_TYPE xQueueSendFromISR(
xQueueHandle pxQueue,
const void *pvItemToQueue,
portBASE_TYPE xTaskPreviouslyWoken
);
*
* Post an item on a queue. It is safe to use this function from within an
* interrupt service routine.
*
* Items are queued by copy not reference so it is preferable to only
* queue small items, especially when called from an ISR. In most cases
* it would be preferable to store a pointer to the item being queued.
*
* @param xQueue The handle to the queue on which the item is to be posted.
*
* @param pvItemToQueue A pointer to the item that is to be placed on the
* queue. The size of the items the queue will hold was defined when the
* queue was created, so this many bytes will be copied from pvItemToQueue
* into the queue storage area.
*
* @param cTaskPreviouslyWoken This is included so an ISR can post onto
* the same queue multiple times from a single interrupt. The first call
* should always pass in pdFALSE. Subsequent calls should pass in
* the value returned from the previous call. See the file serial .c in the
* PC port for a good example of this mechanism.
*
* @return pdTRUE if a task was woken by posting onto the queue. This is
* used by the ISR to determine if a context switch may be required following
* the ISR.
*
* Example usage for buffered IO (where the ISR can obtain more than one value
* per call):
void vBufferISR( void )
{
portCHAR cIn;
portBASE_TYPE xTaskWokenByPost;
// We have not woken a task at the start of the ISR.
cTaskWokenByPost = pdFALSE;
// Loop until the buffer is empty.
do
{
// Obtain a byte from the buffer.
cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );
// Post the byte. The first time round the loop cTaskWokenByPost
// will be pdFALSE. If the queue send causes a task to wake we do
// not want the task to run until we have finished the ISR, so
// xQueueSendFromISR does not cause a context switch. Also we
// don't want subsequent posts to wake any other tasks, so we store
// the return value back into cTaskWokenByPost so xQueueSendFromISR
// knows not to wake any task the next iteration of the loop.
xTaskWokenByPost = xQueueSendFromISR( xRxQueue, &cIn, cTaskWokenByPost );
} while( portINPUT_BYTE( BUFFER_COUNT ) );
// Now the buffer is empty we can switch context if necessary.
if( cTaskWokenByPost )
{
taskYIELD ();
}
}
*
* \defgroup xQueueSendFromISR xQueueSendFromISR
* \ingroup QueueManagement
*/
signed portBASE_TYPE xQueueSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xTaskPreviouslyWoken );
/**
* queue. h
*
portBASE_TYPE xQueueReceiveFromISR(
xQueueHandle pxQueue,
void *pvBuffer,
portBASE_TYPE *pxTaskWoken
);
*
*
* Receive an item from a queue. It is safe to use this function from within an
* interrupt service routine.
*
* @param pxQueue The handle to the queue from which the item is to be
* received.
*
* @param pvBuffer Pointer to the buffer into which the received item will
* be copied.
*
* @param pxTaskWoken A task may be blocked waiting for space to become
* available on the queue. If xQueueReceiveFromISR causes such a task to
* unblock *pxTaskWoken will get set to pdTRUE, otherwise *pxTaskWoken will
* remain unchanged.
*
* @return pdTRUE if an item was successfully received from the queue,
* otherwise pdFALSE.
*
* Example usage:
xQueueHandle xQueue;
// Function to create a queue and post some values.
void vAFunction( void *pvParameters )
{
portCHAR cValueToPost;
const portTickType xBlockTime = ( portTickType )0xff;
// Create a queue capable of containing 10 characters.
xQueue = xQueueCreate( 10, sizeof( portCHAR ) );
if( xQueue == 0 )
{
// Failed to create the queue.
}
// ...
// Post some characters that will be used within an ISR. If the queue
// is full then this task will block for xBlockTime ticks.
cValueToPost = 'a';
xQueueSend( xQueue, ( void * ) &cValueToPost, xBlockTime );
cValueToPost = 'b';
xQueueSend( xQueue, ( void * ) &cValueToPost, xBlockTime );
// ... keep posting characters ... this task may block when the queue
// becomes full.
cValueToPost = 'c';
xQueueSend( xQueue, ( void * ) &cValueToPost, xBlockTime );
}
// ISR that outputs all the characters received on the queue.
void vISR_Routine( void )
{
portBASE_TYPE xTaskWokenByReceive = pdFALSE;
portCHAR cRxedChar;
while( xQueueReceiveFromISR( xQueue, ( void * ) &cRxedChar, &xTaskWokenByReceive) )
{
// A character was received. Output the character now.
vOutputCharacter( cRxedChar );
// If removing the character from the queue woke the task that was
// posting onto the queue cTaskWokenByReceive will have been set to
// pdTRUE. No matter how many times this loop iterates only one
// task will be woken.
}
if( cTaskWokenByPost != ( portCHAR ) pdFALSE;
{
taskYIELD ();
}
}
* \defgroup xQueueReceiveFromISR xQueueReceiveFromISR
* \ingroup QueueManagement
*/
signed portBASE_TYPE xQueueReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxTaskWoken );
/*
* The functions defined above are for passing data to and from tasks. The
* functions below are the equivalents for passing data to and from
* co-rtoutines.
*
* These functions are called from the co-routine macro implementation and
* should not be called directly from application code. Instead use the macro
* wrappers defined within croutine.h.
*/
signed portBASE_TYPE xQueueCRSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xCoRoutinePreviouslyWoken );
signed portBASE_TYPE xQueueCRReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxTaskWoken );
signed portBASE_TYPE xQueueCRSend( xQueueHandle pxQueue, const void *pvItemToQueue, portTickType xTicksToWait );
signed portBASE_TYPE xQueueCRReceive( xQueueHandle pxQueue, void *pvBuffer, portTickType xTicksToWait );
#endif