Introduce xMessageBufferNextLengthBytes() and tests for the same.

Add call to traceTASK_SWITCHED_IN() in vTaskStartScheduler() so trace tools can see the first task to run.

FreeRTOS/Source/include/message_buffer.h

@@ -693,6 +693,25 @@ size_t xMessageBufferSpaceAvailable( MessageBufferHandle_t xMessageBuffer ) );
  */
 #define xMessageBufferSpaceAvailable( xMessageBuffer ) xStreamBufferSpacesAvailable( ( StreamBufferHandle_t ) xMessageBuffer )
 
+/**
+ * message_buffer.h
+ <pre>
+ size_t xMessageBufferNextLengthBytes( MessageBufferHandle_t xMessageBuffer ) );
+ </pre>
+ * Returns the length (in bytes) of the next message in a message buffer.
+ * Useful if xMessageBufferReceive() returned 0 because the size of the buffer
+ * passed into xMessageBufferReceive() was too small to hold the next message.
+ *
+ * @param xMessageBuffer The handle of the message buffer being queried.
+ *
+ * @return The length (in bytes) of the next message in the message buffer, or 0
+ * if the message buffer is empty.
+ *
+ * \defgroup xMessageBufferNextLengthBytes xMessageBufferNextLengthBytes
+ * \ingroup MessageBufferManagement
+ */
+#define xMessageBufferNextLengthBytes( xMessageBuffer ) xStreamBufferNextMessageLengthBytes( ( StreamBufferHandle_t ) xMessageBuffer ) PRIVILEGED_FUNCTION;
+
 /**
  * message_buffer.h
  *

FreeRTOS/Source/include/mpu_prototypes.h

@@ -138,6 +138,7 @@ UBaseType_t MPU_uxEventGroupGetNumber( void* xEventGroup );
 size_t MPU_xStreamBufferSend( StreamBufferHandle_t xStreamBuffer, const void *pvTxData, size_t xDataLengthBytes, TickType_t xTicksToWait );
 size_t MPU_xStreamBufferSendFromISR( StreamBufferHandle_t xStreamBuffer, const void *pvTxData, size_t xDataLengthBytes, BaseType_t * const pxHigherPriorityTaskWoken );
 size_t MPU_xStreamBufferReceive( StreamBufferHandle_t xStreamBuffer, void *pvRxData, size_t xBufferLengthBytes, TickType_t xTicksToWait );
+size_t MPU_xStreamBufferNextMessageLengthBytes( StreamBufferHandle_t xStreamBuffer );
 size_t MPU_xStreamBufferReceiveFromISR( StreamBufferHandle_t xStreamBuffer, void *pvRxData, size_t xBufferLengthBytes, BaseType_t * const pxHigherPriorityTaskWoken );
 void MPU_vStreamBufferDelete( StreamBufferHandle_t xStreamBuffer );
 BaseType_t MPU_xStreamBufferIsFull( StreamBufferHandle_t xStreamBuffer );

FreeRTOS/Source/include/mpu_wrappers.h

@@ -142,6 +142,7 @@ only for ports that are using the MPU. */
 		#define xStreamBufferSend						MPU_xStreamBufferSend
 		#define xStreamBufferSendFromISR				MPU_xStreamBufferSendFromISR
 		#define xStreamBufferReceive					MPU_xStreamBufferReceive
+		#define xStreamBufferNextMessageLengthBytes		MPU_xStreamBufferNextMessageLengthBytes
 		#define xStreamBufferReceiveFromISR				MPU_xStreamBufferReceiveFromISR
 		#define vStreamBufferDelete						MPU_vStreamBufferDelete
 		#define xStreamBufferIsFull						MPU_xStreamBufferIsFull

FreeRTOS/Source/include/stream_buffer.h

@@ -839,6 +839,8 @@ StreamBufferHandle_t xStreamBufferGenericCreateStatic( size_t xBufferSizeBytes,
 													   uint8_t * const pucStreamBufferStorageArea,
 													   StaticStreamBuffer_t * const pxStaticStreamBuffer ) PRIVILEGED_FUNCTION;
 
+size_t xStreamBufferNextMessageLengthBytes( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;
+
 #if( configUSE_TRACE_FACILITY == 1 )
 	void vStreamBufferSetStreamBufferNumber( StreamBufferHandle_t xStreamBuffer, UBaseType_t uxStreamBufferNumber ) PRIVILEGED_FUNCTION;
 	UBaseType_t uxStreamBufferGetStreamBufferNumber( StreamBufferHandle_t xStreamBuffer ) PRIVILEGED_FUNCTION;

FreeRTOS/Source/portable/Common/mpu_wrappers.c

@@ -1136,6 +1136,18 @@ BaseType_t xRunningPrivileged = xPortRaisePrivilege();
 }
 /*-----------------------------------------------------------*/
 
+size_t MPU_xStreamBufferNextMessageLengthBytes( StreamBufferHandle_t xStreamBuffer )
+{
+size_t xReturn;
+BaseType_t xRunningPrivileged = xPortRaisePrivilege();
+
+	xReturn = xStreamBufferNextMessageLengthBytes( xStreamBuffer );
+	vPortResetPrivilege( xRunningPrivileged );
+
+	return xReturn;
+}
+/*-----------------------------------------------------------*/
+
 size_t MPU_xStreamBufferReceive( StreamBufferHandle_t xStreamBuffer, void *pvRxData, size_t xBufferLengthBytes, TickType_t xTicksToWait )
 {
 size_t xReturn;

FreeRTOS/Source/stream_buffer.c

@@ -792,6 +792,48 @@ size_t xReceivedLength = 0, xBytesAvailable, xBytesToStoreMessageLength;
 }
 /*-----------------------------------------------------------*/
 
+size_t xStreamBufferNextMessageLengthBytes( StreamBufferHandle_t xStreamBuffer )
+{
+StreamBuffer_t * const pxStreamBuffer = ( StreamBuffer_t * ) xStreamBuffer; /*lint !e9087 !e9079 Safe cast as StreamBufferHandle_t is opaque Streambuffer_t. */
+size_t xReturn, xBytesAvailable, xOriginalTail;
+
+	configASSERT( pxStreamBuffer );
+
+	/* Ensure the stream buffer is being used as a message buffer. */
+	if( ( pxStreamBuffer->ucFlags & sbFLAGS_IS_MESSAGE_BUFFER ) != ( uint8_t ) 0 )
+	{
+		xBytesAvailable = prvBytesInBuffer( pxStreamBuffer );
+		if( xBytesAvailable > sbBYTES_TO_STORE_MESSAGE_LENGTH )
+		{
+			/* The number of bytes available is greater than the number of bytes
+			required to hold the length of the next message, so another message
+			is available.  Return its length without removing the length bytes
+			from the buffer.  A copy of the tail is stored so the buffer can be
+			returned to its prior state as the message is not actually being
+			removed from the buffer. */
+			xOriginalTail = pxStreamBuffer->xTail;
+			( void ) prvReadBytesFromBuffer( pxStreamBuffer, ( uint8_t * ) &xReturn, sbBYTES_TO_STORE_MESSAGE_LENGTH, xBytesAvailable );
+			pxStreamBuffer->xTail = xOriginalTail;
+		}
+		else
+		{
+			/* The minimum amount of bytes in a message buffer is
+			( sbBYTES_TO_STORE_MESSAGE_LENGTH + 1 ), so if xBytesAvailable is
+			less than sbBYTES_TO_STORE_MESSAGE_LENGTH the only other valid
+			value is 0. */
+			configASSERT( xBytesAvailable == 0 );
+			xReturn = 0;
+		}
+	}
+	else
+	{
+		xReturn = 0;
+	}
+
+	return xReturn;
+}
+/*-----------------------------------------------------------*/
+
 size_t xStreamBufferReceiveFromISR( StreamBufferHandle_t xStreamBuffer,
 									void *pvRxData,
 									size_t xBufferLengthBytes,

FreeRTOS/Source/tasks.c

@@ -1994,6 +1994,8 @@ BaseType_t xReturn;
 		FreeRTOSConfig.h file. */
 		portCONFIGURE_TIMER_FOR_RUN_TIME_STATS();
 
+		traceTASK_SWITCHED_IN();
+
 		/* Setting up the timer tick is hardware specific and thus in the
 		portable interface. */
 		if( xPortStartScheduler() != pdFALSE )