Source/portable/MemMang/heap_1.c

/*
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*/

/* 

Changes between V2.5.1 and V2.5.1

	+ The memory pool has been defined within a struct to ensure correct memory
	  alignment on 32bit systems.

Changes between V2.6.1 and V3.0.0

	+ An overflow check has been added to ensure the next free byte variable 
	  does not wrap around.
*/


/*
 * The simplest possible implementation of pvPortMalloc().  Note that this
 * implementation does NOT allow allocated memory to be freed again.
 *
 * See heap_2.c and heap_3.c for alternative implementations, and the memory
 * management pages of http://www.FreeRTOS.org for more information.
 */
#include <stdlib.h>
#include "FreeRTOS.h"
#include "task.h"

/* Setup the correct byte alignment mask for the defined byte alignment. */

#if portBYTE_ALIGNMENT == 8
	#define heapBYTE_ALIGNMENT_MASK ( ( size_t ) 0x0007 )
#endif

#if portBYTE_ALIGNMENT == 4
	#define heapBYTE_ALIGNMENT_MASK	( ( size_t ) 0x0003 )
#endif

#if portBYTE_ALIGNMENT == 2
	#define heapBYTE_ALIGNMENT_MASK	( ( size_t ) 0x0001 )
#endif

#if portBYTE_ALIGNMENT == 1 
	#define heapBYTE_ALIGNMENT_MASK	( ( size_t ) 0x0000 )
#endif

#ifndef heapBYTE_ALIGNMENT_MASK
	#error "Invalid portBYTE_ALIGNMENT definition"
#endif

/* Allocate the memory for the heap.  The struct is used to force byte
alignment without using any non-portable code. */
static union xRTOS_HEAP
{
	volatile unsigned portLONG ulDummy;
	unsigned portCHAR ucHeap[ configTOTAL_HEAP_SIZE ];
} xHeap;

static size_t xNextFreeByte = ( size_t ) 0;
/*-----------------------------------------------------------*/

void *pvPortMalloc( size_t xWantedSize )
{
void *pvReturn = NULL; 

	/* Ensure that blocks are always aligned to the required number of bytes. */
	#if portBYTE_ALIGNMENT != 1
		if( xWantedSize & heapBYTE_ALIGNMENT_MASK )
		{
			/* Byte alignment required. */
			xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & heapBYTE_ALIGNMENT_MASK ) );
		}
	#endif

	vTaskSuspendAll();
	{
		/* Check there is enough room left for the allocation. */
		if( ( ( xNextFreeByte + xWantedSize ) < configTOTAL_HEAP_SIZE ) &&
			( ( xNextFreeByte + xWantedSize ) > xNextFreeByte )	)/* Check for overflow. */
		{
			/* Return the next free byte then increment the index past this
			block. */
			pvReturn = &( xHeap.ucHeap[ xNextFreeByte ] );
			xNextFreeByte += xWantedSize;			
		}	
	}
	xTaskResumeAll();

	return pvReturn;
}
/*-----------------------------------------------------------*/

void vPortFree( void *pv )
{
	/* Memory cannot be freed using this scheme.  See heap_2.c and heap_3.c 
	for alternative implementations, and the memory management pages of 
	http://www.FreeRTOS.org for more information. */
	( void ) pv;
}
/*-----------------------------------------------------------*/

void vPortInitialiseBlocks( void )
{
	/* Only required when static memory is not cleared. */
	xNextFreeByte = ( size_t ) 0;
}