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Today, I would like to share with you about FreeRTOS dynamic memory allocation how to manage heap5 related knowledge points, detailed content, clear logic, I believe that most people still know too much about this knowledge, so share this article for your reference, I hope you can get something after reading this article, let's take a look at it.

Heap_5.c

Heap5 and heap4 allocation and release algorithm is exactly the same, but heap5 supports the management of multi-block discontiguous memory, the essence is to use a linked list to string multi-block discontinuous memory into a whole block of memory, and then use the heap4 algorithm to allocate release. If you use heap5, you should first call vPortDefineHeapRegions to initialize multiple blocks of discontiguous memory when it comes to allocating freed function calls.

VPortDefineHeapRegions

This function prototype

Void vPortDefineHeapRegions (const HeapRegion_t * const pxHeapRegions)

Parameters are defined in portable.h, as follows

/ * Used by heap_5.c. * / typedef struct HeapRegion {uint8_t * pucStartAddress;// points to the first address of the memory block size_t xSizeInBytes;// this memory block size} HeapRegion_t

For example, if you have 2 blocks of memory to be managed with heap5, address 0x80000000, size 0x10000, address 0x90000000, and size 0xa0000, the structure body array is defined as follows

HeapRegion_t xHeapRegions [] = {{(uint8_t *) 0x80000000UL, 0x10000}, {(uint8_t *) 0x90000000UL, 0xa0000}, {NULL, 0}}

Note that the address order should start from small to large, and end with {NULL,0} (the source code is 0 to judge the end of the loop)

Let's look at the initialization source code.

Void vPortDefineHeapRegions (const HeapRegion_t * const pxHeapRegions) {BlockLink_t * pxFirstFreeBlockInRegion = NULL, * pxPreviousFreeBlock;size_t xAlignedHeap;size_t xTotalRegionSize, xTotalHeapSize = 0persBaseTypetypt xDefinedRegions = 0polisizetypt xAddress;const HeapRegion_t * pxHeapRegion; / * Can only call once! * / configASSERT (pxEnd = = NULL); pxHeapRegion = & (pxHeapRegions [xDefinedRegions]); while (pxHeapRegion- > xSizeInBytes > 0) {xTotalRegionSize = pxHeapRegion- > xSizeInBytes / * Ensure the heap region starts on a correctly aligned boundary. * / xAddress = (size_t) pxHeapRegion- > pucStartAddress; if ((xAddress & portBYTE_ALIGNMENT_MASK)! = 0) {xAddress + = (portBYTE_ALIGNMENT-1); xAddress & = ~ portBYTE_ALIGNMENT_MASK; / * Adjust the size for the bytes lost to alignment. * / xTotalRegionSize-= xAddress-(size_t) pxHeapRegion- > pucStartAddress;} xAlignedHeap = xAddress; / * Set xStart if it has not already been set. * / if (xDefinedRegions = = 0) {/ * xStart is used to hold a pointer to the first item in the list of free blocks. The void cast is used to prevent compiler warnings. * / xStart.pxNextFreeBlock = (BlockLink_t *) xAlignedHeap; xStart.xBlockSize = (size_t) 0;} else {/ * Should only get here if one region has already been added to the heap. * / configASSERT (pxEnd! = NULL); / * Check blocks are passed in with increasing start addresses. * / configASSERT (xAddress > (size_t) pxEnd);} / * Remember the location of the end marker in the previous region, if any. * / pxPreviousFreeBlock = pxEnd; / * pxEnd is used to mark the end of the list of free blocks and is inserted at the end of the region space. * / xAddress = xAlignedHeap + xTotalRegionSize; xAddress-= xHeapStructSize; xAddress & = ~ portBYTE_ALIGNMENT_MASK; pxEnd = (BlockLink_t *) xAddress; pxEnd- > xBlockSize = 0; pxEnd- > pxNextFreeBlock = NULL / * To start with there is a single free block in this region that is sized to take up the entire heap region minus the space taken by the free block structure. * / pxFirstFreeBlockInRegion = (BlockLink_t *) xAlignedHeap; pxFirstFreeBlockInRegion- > xBlockSize = xAddress-(size_t) pxFirstFreeBlockInRegion; pxFirstFreeBlockInRegion- > pxNextFreeBlock = pxEnd; / * If this is not the first region that makes up the entire heap space then link the previous region to this region. * / if (pxPreviousFreeBlock! = NULL) {pxPreviousFreeBlock- > pxNextFreeBlock = pxFirstFreeBlockInRegion;} xTotalHeapSize + = pxFirstFreeBlockInRegion- > xBlockSize; / * Move onto the next HeapRegion_t structure. * / / the next xDefinedRegions++; pxHeapRegion = & (pxHeapRegions [xDefinedRegions]);} xMinimumEverFreeBytesRemaining = xTotalHeapSize; xFreeBytesRemaining = xTotalHeapSize; / * Check something was actually defined before it is accessed. * / configASSERT (xTotalHeapSize); / * Work out the position of the top bit in a size_t variable. * / xBlockAllocatedBit = ((size_t) 1)

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