bremenpl wrote on Tuesday, September 25, 2018:
Hello there,
I was wondering either there is a msize function available that would determine the amount of dynamically allocated memory with freertos malloc port function? I would appreciate all help.
rtel wrote on Tuesday, September 25, 2018:
FreeRTOS keeps memory allocation in the port layer - so the answer is ‘it depends on which memory allocator you are using’. If you are using heap_1, heap_2, heap_4 or heap_5 that come with the kernel download then the answer is no - there is no msize function - but (in heap_4 and heap_5 at least) each block starts with the following structure:
typedef struct A_BLOCK_LINK
{
struct A_BLOCK_LINK *pxNextFreeBlock; /*<< The next free block in the list. */
size_t xBlockSize; /*<< The size of the free block. */
} BlockLink_t;
so you could create one quite easily. This structure is BEFORE the memory returned by malloc(). If you look at the implementation of vPortFree() in heap_4.c you will see how to access it. here is a snippet of the code, you will see that you have to mask off the most significant bit to get the size:
if( pv != NULL )
{
/* The memory being freed will have an BlockLink_t structure immediately
before it. */
puc -= xHeapStructSize;
/* This casting is to keep the compiler from issuing warnings. */
pxLink = ( void * ) puc;
/* Check the block is actually allocated. */
configASSERT( ( pxLink->xBlockSize & xBlockAllocatedBit ) != 0 );
configASSERT( pxLink->pxNextFreeBlock == NULL );