/*
    FreeRTOS V7.0.2 - Copyright (C) 2011 Real Time Engineers Ltd.


    ***************************************************************************
     *                                                                       *
     *    FreeRTOS tutorial books are available in pdf and paperback.        *
     *    Complete, revised, and edited pdf reference manuals are also       *
     *    available.                                                         *
     *                                                                       *
     *    Purchasing FreeRTOS documentation will not only help you, by       *
     *    ensuring you get running as quickly as possible and with an        *
     *    in-depth knowledge of how to use FreeRTOS, it will also help       *
     *    the FreeRTOS project to continue with its mission of providing     *
     *    professional grade, cross platform, de facto standard solutions    *
     *    for microcontrollers - completely free of charge!                  *
     *                                                                       *
     *    >>> See http://www.FreeRTOS.org/Documentation for details. <<<     *
     *                                                                       *
     *    Thank you for using FreeRTOS, and thank you for your support!      *
     *                                                                       *
    ***************************************************************************


    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 (version 2) as published by the
    Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
    >>>NOTE<<< The modification to the GPL is included to allow you to
    distribute a combined work that includes FreeRTOS without being obliged to
    provide the source code for proprietary components outside of the FreeRTOS
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    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 and the FreeRTOS license exception along with FreeRTOS; if not it
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    by writing to Richard Barry, contact details for whom are available on the
    FreeRTOS WEB site.

    1 tab == 4 spaces!

    http://www.FreeRTOS.org - Documentation, latest information, license and
    contact details.

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*/


#ifndef QUEUE_H
#define QUEUE_H

#ifndef INC_FREERTOS_H
	#error "#include FreeRTOS.h" must appear in source files before "#include queue.h"
#endif

#ifdef __cplusplus
extern "C" {
#endif


#include "mpu_wrappers.h"

typedef struct QueueDefinition
{
	signed char *pcHead;				/*< Points to the beginning of the queue storage area. */
	signed char *pcTail;				/*< Points to the byte at the end of the queue storage area.  Once more byte is allocated than necessary to store the queue items, this is used as a marker. */

	signed char *pcWriteTo;				/*< Points to the free next place in the storage area. */
	signed char *pcReadFrom;			/*< Points to the last place that a queued item was read from. */

	xList xTasksWaitingToSend;				/*< List of tasks that are blocked waiting to post onto this queue.  Stored in priority order. */
	xList xTasksWaitingToReceive;			/*< List of tasks that are blocked waiting to read from this queue.  Stored in priority order. */

	volatile unsigned portBASE_TYPE uxMessagesWaiting;/*< The number of items currently in the queue. */
	unsigned portBASE_TYPE uxLength;		/*< The length of the queue defined as the number of items it will hold, not the number of bytes. */
	unsigned portBASE_TYPE uxItemSize;		/*< The size of each items that the queue will hold. */

	signed portBASE_TYPE xRxLock;			/*< Stores the number of items received from the queue (removed from the queue) while the queue was locked.  Set to queueUNLOCKED when the queue is not locked. */
	signed portBASE_TYPE xTxLock;			/*< Stores the number of items transmitted to the queue (added to the queue) while the queue was locked.  Set to queueUNLOCKED when the queue is not locked. */

} xQUEUE;


/**
 * Type by which queues are referenced.  For example, a call to xQueueCreate
 * returns (via a pointer parameter) an xQueueHandle variable that can then
 * be used as a parameter to xQueueSend(), xQueueReceive(), etc.
 */
typedef xQUEUE * xQueueHandle;


/* For internal use only. */
#define	queueSEND_TO_BACK	( 0 )
#define	queueSEND_TO_FRONT	( 1 )


/**
 * 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
 {
	char ucMessageID;
	char ucData[ 20 ];
 };

 void vATask( void *pvParameters )
 {
 xQueueHandle xQueue1, xQueue2;

	// Create a queue capable of containing 10 unsigned long values.
	xQueue1 = xQueueCreate( 10, sizeof( unsigned long ) );
	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 xQueueCreateExt( void *QueueStart, unsigned portBASE_TYPE uxQueueLength, unsigned portBASE_TYPE uxItemSize );
xQueueHandle xQueueCreate( unsigned portBASE_TYPE uxQueueLength, unsigned portBASE_TYPE uxItemSize );

/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueSendToToFront(
								   xQueueHandle	xQueue,
								   const void	*	pvItemToQueue,
								   portTickType	xTicksToWait
							   );
 * </pre>
 *
 * This is a macro that calls xQueueGenericSend().
 *
 * Post an item to the front of 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 and the
 * queue is full.  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
 {
	char ucMessageID;
	char ucData[ 20 ];
 } xMessage;

 unsigned long 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 long ) );

	// 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( xQueueSendToFront( 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;
		xQueueSendToFront( xQueue2, ( void * ) &pxMessage, ( portTickType ) 0 );
	}

	// ... Rest of task code.
 }
 </pre>
 * \defgroup xQueueSend xQueueSend
 * \ingroup QueueManagement
 */
#define xQueueSendToFront( xQueue, pvItemToQueue, xTicksToWait ) xQueueGenericSend( ( xQueue ), ( pvItemToQueue ), ( xTicksToWait ), queueSEND_TO_FRONT )

/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueSendToBack(
								   xQueueHandle	xQueue,
								   const	void	*	pvItemToQueue,
								   portTickType	xTicksToWait
							   );
 * </pre>
 *
 * This is a macro that calls xQueueGenericSend().
 *
 * Post an item to the back of 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 and the queue
 * is full.  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
 {
	char ucMessageID;
	char ucData[ 20 ];
 } xMessage;

 unsigned long 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 long ) );

	// 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( xQueueSendToBack( 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;
		xQueueSendToBack( xQueue2, ( void * ) &pxMessage, ( portTickType ) 0 );
	}

	// ... Rest of task code.
 }
 </pre>
 * \defgroup xQueueSend xQueueSend
 * \ingroup QueueManagement
 */
#define xQueueSendToBack( xQueue, pvItemToQueue, xTicksToWait ) xQueueGenericSend( ( xQueue ), ( pvItemToQueue ), ( xTicksToWait ), queueSEND_TO_BACK )

/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueSend(
							  xQueueHandle xQueue,
							  const void * pvItemToQueue,
							  portTickType xTicksToWait
						 );
 * </pre>
 *
 * This is a macro that calls xQueueGenericSend().  It is included for
 * backward compatibility with versions of FreeRTOS.org that did not
 * include the xQueueSendToFront() and xQueueSendToBack() macros.  It is
 * equivalent to xQueueSendToBack().
 *
 * 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 and the
 * queue is full.  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
 {
	char ucMessageID;
	char ucData[ 20 ];
 } xMessage;

 unsigned long 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 long ) );

	// 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
 */
#define xQueueSend( xQueue, pvItemToQueue, xTicksToWait ) xQueueGenericSend( ( xQueue ), ( pvItemToQueue ), ( xTicksToWait ), queueSEND_TO_BACK )


/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueGenericSend(
									xQueueHandle xQueue,
									const void * pvItemToQueue,
									portTickType xTicksToWait
									portBASE_TYPE xCopyPosition
								);
 * </pre>
 *
 * It is preferred that the macros xQueueSend(), xQueueSendToFront() and
 * xQueueSendToBack() are used in place of calling this function directly.
 *
 * 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 and the
 * queue is full.  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.
 *
 * @param xCopyPosition Can take the value queueSEND_TO_BACK to place the
 * item at the back of the queue, or queueSEND_TO_FRONT to place the item
 * at the front of the queue (for high priority messages).
 *
 * @return pdTRUE if the item was successfully posted, otherwise errQUEUE_FULL.
 *
 * Example usage:
   <pre>
 struct AMessage
 {
	char ucMessageID;
	char ucData[ 20 ];
 } xMessage;

 unsigned long 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 long ) );

	// 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( xQueueGenericSend( xQueue1, ( void * ) &ulVar, ( portTickType ) 10, queueSEND_TO_BACK ) != 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;
		xQueueGenericSend( xQueue2, ( void * ) &pxMessage, ( portTickType ) 0, queueSEND_TO_BACK );
	}

	// ... Rest of task code.
 }
 </pre>
 * \defgroup xQueueSend xQueueSend
 * \ingroup QueueManagement
 */
signed portBASE_TYPE xQueueGenericSend( xQueueHandle pxQueue, const void * const pvItemToQueue, portTickType xTicksToWait, portBASE_TYPE xCopyPosition );

/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueuePeek(
							 xQueueHandle xQueue,
							 void *pvBuffer,
							 portTickType xTicksToWait
						 );</pre>
 *
 * 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.
 *
 * @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.
 * xQueuePeek() will return immediately if xTicksToWait is 0 and the queue
 * is empty.
 *
 * @return pdTRUE if an item was successfully received from the queue,
 * otherwise pdFALSE.
 *
 * Example usage:
   <pre>
 struct AMessage
 {
	char ucMessageID;
	char 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 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 ), ( portTickType ) 10 ) )
		{
			// pcRxedMessage now points to the struct AMessage variable posted
			// by vATask, but the item still remains on the queue.
		}
	}

	// ... Rest of task code.
 }
 </pre>
 * \defgroup xQueueReceive xQueueReceive
 * \ingroup QueueManagement
 */
#define xQueuePeek( xQueue, pvBuffer, xTicksToWait ) xQueueGenericReceive( ( xQueue ), ( pvBuffer ), ( xTicksToWait ), pdTRUE )

/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueReceive(
								 xQueueHandle xQueue,
								 void *pvBuffer,
								 portTickType xTicksToWait
							);</pre>
 *
 * 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.
 *
 * @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.	 xQueueReceive() will return immediately if xTicksToWait
 * is zero and the queue is empty.  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
 {
	char ucMessageID;
	char 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.
 }
 </pre>
 * \defgroup xQueueReceive xQueueReceive
 * \ingroup QueueManagement
 */
#define xQueueReceive( xQueue, pvBuffer, xTicksToWait ) xQueueGenericReceive( ( xQueue ), ( pvBuffer ), ( xTicksToWait ), pdFALSE )


/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueGenericReceive(
									   xQueueHandle	xQueue,
									   void	*pvBuffer,
									   portTickType	xTicksToWait
									   portBASE_TYPE	xJustPeek
									);</pre>
 *
 * 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.
 *
 * @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.
 * xQueueGenericReceive() will return immediately if the queue is empty and
 * xTicksToWait is 0.
 *
 * @param xJustPeek When 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.
 *
 * @return pdTRUE if an item was successfully received from the queue,
 * otherwise pdFALSE.
 *
 * Example usage:
   <pre>
 struct AMessage
 {
	char ucMessageID;
	char 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( xQueueGenericReceive( xQueue, &( pxRxedMessage ), ( portTickType ) 10 ) )
		{
			// pcRxedMessage now points to the struct AMessage variable posted
			// by vATask.
		}
	}

	// ... Rest of task code.
 }
 </pre>
 * \defgroup xQueueReceive xQueueReceive
 * \ingroup QueueManagement
 */
signed portBASE_TYPE xQueueGenericReceive( xQueueHandle xQueue, void * const pvBuffer, portTickType xTicksToWait, portBASE_TYPE xJustPeek );

/**
 * queue. h
 * <pre>unsigned portBASE_TYPE uxQueueMessagesWaiting( const xQueueHandle xQueue );</pre>
 *
 * 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( const xQueueHandle xQueue );

/**
 * queue. h
 * <pre>void vQueueDelete( xQueueHandle xQueue );</pre>
 *
 * 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 pxQueue );
void vQueueDeleteExt( xQueueHandle pxQueue );
/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueSendToFrontFromISR(
										 xQueueHandle pxQueue,
										 const void *pvItemToQueue,
										 portBASE_TYPE *pxHigherPriorityTaskWoken
									  );
 </pre>
 *
 * This is a macro that calls xQueueGenericSendFromISR().
 *
 * Post an item to the front of a queue.  It is safe to use this macro 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 pxHigherPriorityTaskWoken xQueueSendToFrontFromISR() will set
 * *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task
 * to unblock, and the unblocked task has a priority higher than the currently
 * running task.  If xQueueSendToFromFromISR() sets this value to pdTRUE then
 * a context switch should be requested before the interrupt is exited.
 *
 * @return pdTRUE if the data was successfully sent to the queue, otherwise
 * errQUEUE_FULL.
 *
 * Example usage for buffered IO (where the ISR can obtain more than one value
 * per call):
   <pre>
 void vBufferISR( void )
 {
 char cIn;
 portBASE_TYPE xHigherPrioritTaskWoken;

	// We have not woken a task at the start of the ISR.
	xHigherPriorityTaskWoken = pdFALSE;

	// Loop until the buffer is empty.
	do
	{
		// Obtain a byte from the buffer.
		cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );

		// Post the byte.
		xQueueSendToFrontFromISR( xRxQueue, &cIn, &xHigherPriorityTaskWoken );

	} while( portINPUT_BYTE( BUFFER_COUNT ) );

	// Now the buffer is empty we can switch context if necessary.
	if( xHigherPriorityTaskWoken )
	{
		taskYIELD ();
	}
 }
 </pre>
 *
 * \defgroup xQueueSendFromISR xQueueSendFromISR
 * \ingroup QueueManagement
 */
#define xQueueSendToFrontFromISR( pxQueue, pvItemToQueue, pxHigherPriorityTaskWoken ) xQueueGenericSendFromISR( ( pxQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_FRONT )


/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueSendToBackFromISR(
										 xQueueHandle pxQueue,
										 const void *pvItemToQueue,
										 portBASE_TYPE *pxHigherPriorityTaskWoken
									  );
 </pre>
 *
 * This is a macro that calls xQueueGenericSendFromISR().
 *
 * Post an item to the back of a queue.  It is safe to use this macro 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 pxHigherPriorityTaskWoken xQueueSendToBackFromISR() will set
 * *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task
 * to unblock, and the unblocked task has a priority higher than the currently
 * running task.  If xQueueSendToBackFromISR() sets this value to pdTRUE then
 * a context switch should be requested before the interrupt is exited.
 *
 * @return pdTRUE if the data was successfully sent to the queue, otherwise
 * errQUEUE_FULL.
 *
 * Example usage for buffered IO (where the ISR can obtain more than one value
 * per call):
   <pre>
 void vBufferISR( void )
 {
 char cIn;
 portBASE_TYPE xHigherPriorityTaskWoken;

	// We have not woken a task at the start of the ISR.
	xHigherPriorityTaskWoken = pdFALSE;

	// Loop until the buffer is empty.
	do
	{
		// Obtain a byte from the buffer.
		cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );

		// Post the byte.
		xQueueSendToBackFromISR( xRxQueue, &cIn, &xHigherPriorityTaskWoken );

	} while( portINPUT_BYTE( BUFFER_COUNT ) );

	// Now the buffer is empty we can switch context if necessary.
	if( xHigherPriorityTaskWoken )
	{
		taskYIELD ();
	}
 }
 </pre>
 *
 * \defgroup xQueueSendFromISR xQueueSendFromISR
 * \ingroup QueueManagement
 */
#define xQueueSendToBackFromISR( pxQueue, pvItemToQueue, pxHigherPriorityTaskWoken ) xQueueGenericSendFromISR( ( pxQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_BACK )

/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueSendFromISR(
									 xQueueHandle pxQueue,
									 const void *pvItemToQueue,
									 portBASE_TYPE *pxHigherPriorityTaskWoken
								);
 </pre>
 *
 * This is a macro that calls xQueueGenericSendFromISR().  It is included
 * for backward compatibility with versions of FreeRTOS.org that did not
 * include the xQueueSendToBackFromISR() and xQueueSendToFrontFromISR()
 * macros.
 *
 * Post an item to the back of 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 pxHigherPriorityTaskWoken xQueueSendFromISR() will set
 * *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task
 * to unblock, and the unblocked task has a priority higher than the currently
 * running task.  If xQueueSendFromISR() sets this value to pdTRUE then
 * a context switch should be requested before the interrupt is exited.
 *
 * @return pdTRUE if the data was successfully sent to the queue, otherwise
 * errQUEUE_FULL.
 *
 * Example usage for buffered IO (where the ISR can obtain more than one value
 * per call):
   <pre>
 void vBufferISR( void )
 {
 char cIn;
 portBASE_TYPE xHigherPriorityTaskWoken;

	// We have not woken a task at the start of the ISR.
	xHigherPriorityTaskWoken = pdFALSE;

	// Loop until the buffer is empty.
	do
	{
		// Obtain a byte from the buffer.
		cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );

		// Post the byte.
		xQueueSendFromISR( xRxQueue, &cIn, &xHigherPriorityTaskWoken );

	} while( portINPUT_BYTE( BUFFER_COUNT ) );

	// Now the buffer is empty we can switch context if necessary.
	if( xHigherPriorityTaskWoken )
	{
		// Actual macro used here is port specific.
		taskYIELD_FROM_ISR ();
	}
 }
 </pre>
 *
 * \defgroup xQueueSendFromISR xQueueSendFromISR
 * \ingroup QueueManagement
 */
#define xQueueSendFromISR( pxQueue, pvItemToQueue, pxHigherPriorityTaskWoken ) xQueueGenericSendFromISR( ( pxQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_BACK )

/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueGenericSendFromISR(
										   xQueueHandle	pxQueue,
										   const	void	*pvItemToQueue,
										   portBASE_TYPE	*pxHigherPriorityTaskWoken,
										   portBASE_TYPE	xCopyPosition
									   );
 </pre>
 *
 * It is preferred that the macros xQueueSendFromISR(),
 * xQueueSendToFrontFromISR() and xQueueSendToBackFromISR() be used in place
 * of calling this function directly.
 *
 * 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 pxHigherPriorityTaskWoken xQueueGenericSendFromISR() will set
 * *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task
 * to unblock, and the unblocked task has a priority higher than the currently
 * running task.  If xQueueGenericSendFromISR() sets this value to pdTRUE then
 * a context switch should be requested before the interrupt is exited.
 *
 * @param xCopyPosition Can take the value queueSEND_TO_BACK to place the
 * item at the back of the queue, or queueSEND_TO_FRONT to place the item
 * at the front of the queue (for high priority messages).
 *
 * @return pdTRUE if the data was successfully sent to the queue, otherwise
 * errQUEUE_FULL.
 *
 * Example usage for buffered IO (where the ISR can obtain more than one value
 * per call):
   <pre>
 void vBufferISR( void )
 {
 char cIn;
 portBASE_TYPE xHigherPriorityTaskWokenByPost;

	// We have not woken a task at the start of the ISR.
	xHigherPriorityTaskWokenByPost = pdFALSE;

	// Loop until the buffer is empty.
	do
	{
		// Obtain a byte from the buffer.
		cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );

		// Post each byte.
		xQueueGenericSendFromISR( xRxQueue, &cIn, &xHigherPriorityTaskWokenByPost, queueSEND_TO_BACK );

	} while( portINPUT_BYTE( BUFFER_COUNT ) );

	// Now the buffer is empty we can switch context if necessary.  Note that the
	// name of the yield function required is port specific.
	if( xHigherPriorityTaskWokenByPost )
	{
		taskYIELD_YIELD_FROM_ISR();
	}
 }
 </pre>
 *
 * \defgroup xQueueSendFromISR xQueueSendFromISR
 * \ingroup QueueManagement
 */
signed portBASE_TYPE xQueueGenericSendFromISR( xQueueHandle pxQueue, const void * const pvItemToQueue, signed portBASE_TYPE *pxHigherPriorityTaskWoken, portBASE_TYPE xCopyPosition );

/**
 * queue. h
 * <pre>
 portBASE_TYPE xQueueReceiveFromISR(
									   xQueueHandle	pxQueue,
									   void	*pvBuffer,
									   portBASE_TYPE	*pxTaskWoken
								   );
 * </pre>
 *
 * 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:
   <pre>

 xQueueHandle xQueue;

 // Function to create a queue and post some values.
 void vAFunction( void *pvParameters )
 {
 char cValueToPost;
 const portTickType xBlockTime = ( portTickType )0xff;

	// Create a queue capable of containing 10 characters.
	xQueue = xQueueCreate( 10, sizeof( char ) );
	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;
 char 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 != ( char ) pdFALSE;
	{
		taskYIELD ();
	}
 }
 </pre>
 * \defgroup xQueueReceiveFromISR xQueueReceiveFromISR
 * \ingroup QueueManagement
 */
signed portBASE_TYPE xQueueReceiveFromISR( xQueueHandle pxQueue, void * const pvBuffer, signed portBASE_TYPE *pxTaskWoken );

/*
 * Utilities to query queue that are safe to use from an ISR.  These utilities
 * should be used only from witin an ISR, or within a critical section.
 */
signed portBASE_TYPE xQueueIsQueueEmptyFromISR( const xQueueHandle pxQueue );
signed portBASE_TYPE xQueueIsQueueFullFromISR( const xQueueHandle pxQueue );
unsigned portBASE_TYPE uxQueueMessagesWaitingFromISR( const xQueueHandle pxQueue );


/*
 * xQueueAltGenericSend() is an alternative version of xQueueGenericSend().
 * Likewise xQueueAltGenericReceive() is an alternative version of
 * xQueueGenericReceive().
 *
 * The source code that implements the alternative (Alt) API is much
 * simpler	because it executes everything from within a critical section.
 * This is	the approach taken by many other RTOSes, but FreeRTOS.org has the
 * preferred fully featured API too.  The fully featured API has more
 * complex	code that takes longer to execute, but makes much less use of
 * critical sections.  Therefore the alternative API sacrifices interrupt
 * responsiveness to gain execution speed, whereas the fully featured API
 * sacrifices execution speed to ensure better interrupt responsiveness.
 */
signed portBASE_TYPE xQueueAltGenericSend( xQueueHandle pxQueue, const void * const pvItemToQueue, portTickType xTicksToWait, portBASE_TYPE xCopyPosition );
signed portBASE_TYPE xQueueAltGenericReceive( xQueueHandle pxQueue, void * const pvBuffer, portTickType xTicksToWait, portBASE_TYPE xJustPeeking );
#define xQueueAltSendToFront( xQueue, pvItemToQueue, xTicksToWait ) xQueueAltGenericSend( ( xQueue ), ( pvItemToQueue ), ( xTicksToWait ), queueSEND_TO_FRONT )
#define xQueueAltSendToBack( xQueue, pvItemToQueue, xTicksToWait ) xQueueAltGenericSend( ( xQueue ), ( pvItemToQueue ), ( xTicksToWait ), queueSEND_TO_BACK )
#define xQueueAltReceive( xQueue, pvBuffer, xTicksToWait ) xQueueAltGenericReceive( ( xQueue ), ( pvBuffer ), ( xTicksToWait ), pdFALSE )
#define xQueueAltPeek( xQueue, pvBuffer, xTicksToWait ) xQueueAltGenericReceive( ( xQueue ), ( pvBuffer ), ( xTicksToWait ), pdTRUE )

/*
 * 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-routines.
 *
 * 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 );

/*
 * For internal use only.  Use xSemaphoreCreateMutex() or
 * xSemaphoreCreateCounting() instead of calling these functions directly.
 */
xQueueHandle xQueueCreateMutex( void );
xQueueHandle xQueueCreateCountingSemaphore( unsigned portBASE_TYPE uxCountValue, unsigned portBASE_TYPE uxInitialCount );

/*
 * For internal use only.  Use xSemaphoreTakeMutexRecursive() or
 * xSemaphoreGiveMutexRecursive() instead of calling these functions directly.
 */
portBASE_TYPE xQueueTakeMutexRecursive( xQueueHandle pxMutex, portTickType xBlockTime );
portBASE_TYPE xQueueGiveMutexRecursive( xQueueHandle pxMutex );

/*
 * The registry is provided as a means for kernel aware debuggers to
 * locate queues, semaphores and mutexes.  Call vQueueAddToRegistry() add
 * a queue, semaphore or mutex handle to the registry if you want the handle
 * to be available to a kernel aware debugger.  If you are not using a kernel
 * aware debugger then this function can be ignored.
 *
 * configQUEUE_REGISTRY_SIZE defines the maximum number of handles the
 * registry can hold.  configQUEUE_REGISTRY_SIZE must be greater than 0
 * within FreeRTOSConfig.h for the registry to be available.  Its value
 * does not effect the number of queues, semaphores and mutexes that can be
 * created - just the number that the registry can hold.
 *
 * @param xQueue The handle of the queue being added to the registry.  This
 * is the handle returned by a call to xQueueCreate().  Semaphore and mutex
 * handles can also be passed in here.
 *
 * @param pcName The name to be associated with the handle.  This is the
 * name that the kernel aware debugger will display.
 */
#if configQUEUE_REGISTRY_SIZE > 0U
	void vQueueAddToRegistry( xQueueHandle xQueue, signed char *pcName );
#endif

/* Not a public API function, hence the 'Restricted' in the name. */
void vQueueWaitForMessageRestricted( xQueueHandle pxQueue, portTickType xTicksToWait );


#ifdef __cplusplus
}
#endif

#endif /* QUEUE_H */

