FreeRTOS动态内存分配管理heap_5示例

2024-04-02 19:04:59 786人浏览八月长安

摘要

目录heap_5.cvPortDefineHeapRegions常见问题heap_5.c heap5与heap4分配释放算法完全相同，只是heap5支持管理多块不连续的内存，本质是将

heap_5.c

heap5与heap4分配释放算法完全相同，只是heap5支持管理多块不连续的内存，本质是将多块不连续内存用链表串成一整块内存，再用heap4算法来分配释放。若使用heap5则在涉及到分配释放的函数调用时要先调用vPortDefineHeapRegions把多块不连续内存串成一块初始化。

vPortDefineHeapRegions

此函数原型

void vPortDefineHeapRegions( const HeapRegion_t * const pxHeapRegions )，

参数在portable.h中定义，如下


typedef struct HeapRegion
{
	uint8_t *pucStartAddress;//指向内存块首地址
	size_t xSizeInBytes;//此内存块大小
} HeapRegion_t;

比如有2块内存要用heap5管理，地址0x80000000，大小0x10000,地址0x90000000，大小0xa0000,则如下定义该结构体数组

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

注意地址顺序要从小到大，最后要以{NULL，0}结尾(源码是以0做判断结束循环)
下面看初始化源码

void vPortDefineHeapRegions( const HeapRegion_t * const pxHeapRegions )
{
BlockLink_t *pxFirstFreeBlockInRegion = NULL, *pxPreviousFreeBlock;
size_t xAlignedHeap;
size_t xTotalRegionSize, xTotalHeapSize = 0;
BaseType_t xDefinedRegions = 0;
size_t xAddress;
const HeapRegion_t *pxHeapRegion;
	
	configASSERT( pxEnd == NULL );
	pxHeapRegion = &( pxHeapRegions[ xDefinedRegions ] );
	while( pxHeapRegion->xSizeInBytes > 0 )
	{
		xTotalRegionSize = pxHeapRegion->xSizeInBytes;
		
		xAddress = ( size_t ) pxHeapRegion->pucStartAddress;
		if( ( xAddress & portBYTE_ALIGNMENT_MASK ) != 0 )
		{
			xAddress += ( portBYTE_ALIGNMENT - 1 );
			xAddress &= ~portBYTE_ALIGNMENT_MASK;
			
			xTotalRegionSize -= xAddress - ( size_t ) pxHeapRegion->pucStartAddress;
		}
		xAlignedHeap = xAddress;
		
		if( xDefinedRegions == 0 )
		{
			
			xStart.pxNextFreeBlock = ( BlockLink_t * ) xAlignedHeap;
			xStart.xBlockSize = ( size_t ) 0;
		}
		else
		{
			
			configASSERT( pxEnd != NULL );
			
			configASSERT( xAddress > ( size_t ) pxEnd );
		}
		
		pxPreviousFreeBlock = pxEnd;
		
		xAddress = xAlignedHeap + xTotalRegionSize;
		xAddress -= xHeapStructSize;
		xAddress &= ~portBYTE_ALIGNMENT_MASK;
		pxEnd = ( BlockLink_t * ) xAddress;
		pxEnd->xBlockSize = 0;
		pxEnd->pxNextFreeBlock = NULL;
		
		pxFirstFreeBlockInRegion = ( BlockLink_t * ) xAlignedHeap;
		pxFirstFreeBlockInRegion->xBlockSize = xAddress - ( size_t ) pxFirstFreeBlockInRegion;
		pxFirstFreeBlockInRegion->pxNextFreeBlock = pxEnd;
		
		if( pxPreviousFreeBlock != NULL )
		{
			pxPreviousFreeBlock->pxNextFreeBlock = pxFirstFreeBlockInRegion;
		}
		xTotalHeapSize += pxFirstFreeBlockInRegion->xBlockSize;
		
		//下一块
		xDefinedRegions++;
		pxHeapRegion = &( pxHeapRegions[ xDefinedRegions ] );
	}
	xMinimumEverFreeBytesRemaining = xTotalHeapSize;
	xFreeBytesRemaining = xTotalHeapSize;
	
	configASSERT( xTotalHeapSize );
	
	xBlockAllocatedBit = ( ( size_t ) 1 ) << ( ( sizeof( size_t ) * heapBITS_PER_BYTE ) - 1 );
}

常见问题

比如有多块内存，一块是内部ram，其他是外部ram，外部的地址能写死确定，但是内部的会随着程序开发不停改变，怎么确定呢，下面是官网给的例子


#define RAM2_START_ADDRESS ( ( uint8_t * ) 0x00020000 )
#define RAM2_SIZE ( 32 * 1024 )
#define RAM3_START_ADDRESS ( ( uint8_t * ) 0x00030000 )
#define RAM3_SIZE ( 32 * 1024 )

#define RAM1_HEAP_SIZE ( 30 * 1024 )
static uint8_t ucHeap[ RAM1_HEAP_SIZE ];

const HeapRegion_t xHeapRegions[] =
{
    { ucHeap, RAM1_HEAP_SIZE },
    { RAM2_START_ADDRESS, RAM2_SIZE },
    { RAM3_START_ADDRESS, RAM3_SIZE },
    { NULL, 0 } 
};

这样就不用老是修改第一块的起始地址。

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