queue.h

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/*
	FreeRTOS V3.2.0 - Copyright (C) 2003 - 2005 Richard Barry.

	This file is part of the FreeRTOS distribution.

	FreeRTOS 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 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; 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, 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
 * <pre>
 * xQueueHandle xQueueCreate(
 *                            unsigned portBASE_TYPE uxQueueLength,
 *                            unsigned portBASE_TYPE uxItemSize
 *                          );
 * </pre>
 *
 * 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:
   <pre>
 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.
 }
 </pre>
 * \defgroup xQueueCreate xQueueCreate
 * \ingroup QueueManagement
 */
xQueueHandle xQueueCreate( unsigned portBASE_TYPE uxQueueLength, unsigned portBASE_TYPE uxItemSize );

/**
 * queue. h
 * <pre>
 * portBASE_TYPE xQueueSend(
 *								xQueueHandle xQueue,
 *								const void * pvItemToQueue,
 *								portTickType xTicksToWait
 *							);
 * </pre>
 *
 * 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:
   <pre>
 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.
 }
 </pre>
 * \defgroup xQueueSend xQueueSend
 * \ingroup QueueManagement
 */
signed portBASE_TYPE xQueueSend( xQueueHandle xQueue, const void * pvItemToQueue, portTickType xTicksToWait );

/**
 * queue. h
 * <pre>
 * portBASE_TYPE xQueueReceive(
 *                              xQueueHandle xQueue,
 *                              void *pcBuffer,
 *                              portTickType xTicksToWait
 *                            );</pre>
 *
 * 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 pcBuffer 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:
   <pre>
 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;