Diff: FreeRTOS/Source/include/queue.h

Revision:

0:d4960fcea8ff

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FreeRTOS/Source/include/queue.h	Sat Jan 01 11:17:45 2011 +0000
@@ -0,0 +1,1259 @@
+/*
+    FreeRTOS V6.0.3 - Copyright (C) 2010 Real Time Engineers Ltd.
+
+    ***************************************************************************
+    *                                                                         *
+    * If you are:                                                             *
+    *                                                                         *
+    *    + New to FreeRTOS,                                                   *
+    *    + Wanting to learn FreeRTOS or multitasking in general quickly       *
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+    *    + Wanting to improve your FreeRTOS skills and productivity           *
+    *                                                                         *
+    * then take a look at the FreeRTOS eBook                                  *
+    *                                                                         *
+    *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *
+    *                  http://www.FreeRTOS.org/Documentation                  *
+    *                                                                         *
+    * A pdf reference manual is also available.  Both are usually delivered   *
+    * to your inbox within 20 minutes to two hours when purchased between 8am *
+    * and 8pm GMT (although please allow up to 24 hours in case of            *
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+    *                                                                         *
+    ***************************************************************************
+
+    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 exception 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 kernel.
+    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 and the FreeRTOS license exception along with FreeRTOS; if not it 
+    can be viewed here: http://www.freertos.org/a00114.html and also obtained 
+    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.
+
+    http://www.SafeRTOS.com - A version that is certified for use in safety
+    critical systems.
+
+    http://www.OpenRTOS.com - Commercial support, development, porting,
+    licensing and training services.
+*/
+
+#ifndef INC_FREERTOS_H
+    #error "#include FreeRTOS.h" must appear in source files before "#include queue.h"
+#endif
+
+
+
+
+#ifndef QUEUE_H
+#define QUEUE_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "mpu_wrappers.h"
+
+typedef void * 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 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 xQueue, 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 xQueue );
+
+/**
+ * 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 xMutex, portTickType xBlockTime );
+portBASE_TYPE xQueueGiveMutexRecursive( xQueueHandle xMutex );
+
+/*
+ * 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 > 0
+    void vQueueAddToRegistry( xQueueHandle xQueue, signed char *pcName );
+//#endif
+
+
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* QUEUE_H */
+