FreeRTOS内存管理

static size_t xNextFreeByte = ( size_t ) 0;
 
void *pvPortMalloc( size_t xWantedSize )
{
    static uint8_t *pucAlignedHeap = NULL;
    ...
}

void *pvPortMalloc( size_t xWantedSize )
{
void *pvReturn = NULL;
static uint8_t *pucAlignedHeap = NULL;
 
    /* Ensure that blocks are always aligned to the required number of bytes. */
    #if(portBYTE_ALIGNMENT != 1)
    {
        if(xWantedSize & portBYTE_ALIGNMENT_MASK)
        {
            /* Byte alignment required. */
            xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) );
        }
    }
    #endif
 
    vTaskSuspendAll();
    {
        if(pucAlignedHeap == NULL)
        {
            /* Ensure the heap starts on a correctly aligned boundary. */
            pucAlignedHeap = (uint8_t *)(((portPOINTER_SIZE_TYPE)&ucHeap[portBYTE_ALIGNMENT]) & (~((portPOINTER_SIZE_TYPE) portBYTE_ALIGNMENT_MASK)));
        }
 
        /* Check there is enough room left for the allocation. */
        if( ( ( xNextFreeByte + xWantedSize ) < configADJUSTED_HEAP_SIZE ) &&
            ( ( xNextFreeByte + xWantedSize ) > xNextFreeByte )    )/* Check for overflow. */
        {
            /* Return the next free byte then increment the index past this
            block. */
            pvReturn = pucAlignedHeap + xNextFreeByte;
            xNextFreeByte += xWantedSize;
        }
 
        traceMALLOC( pvReturn, xWantedSize );
    }
    ( void ) xTaskResumeAll();
 
    #if( configUSE_MALLOC_FAILED_HOOK == 1 )
    {
        if( pvReturn == NULL )
        {
            extern void vApplicationMallocFailedHook( void );
            vApplicationMallocFailedHook();
        }
    }
    #endif
 
    return pvReturn;
}

/* A few bytes might be lost to byte aligning the heap start address. */
#define configADJUSTED_HEAP_SIZE    ( configTOTAL_HEAP_SIZE - portBYTE_ALIGNMENT )