裸機malloc實現

曾在arm裸機程序或者RTOS移植時，用到malloc，參考某位網友修改。

在6410跑過，所以設置6410的一塊固定地址爲堆，提供給malloc。

#define UNUSED 0
#define USED 1
#define HEAP_NOTFIND 0
#define HEAP_FOUND  1

static unsigned long HEAP_START = 0x54000000;
static unsigned long HEAP_END = 0x58000000;

typedef struct heap
{
	int size;
	int start;
	int end;
	int used;
	struct heap *next;
	struct heap *prv;
}heap;

static heap *heap_head;
static heap *heap_crrunt;
static heap *heap_mark;
static int heapnum=0;


//初始化堆
void init_heap()
{

	heap_head = (heap *)HEAP_START;
	heap_head->size = (HEAP_END-HEAP_START)-sizeof(heap);
	heap_head->start = HEAP_START+sizeof(heap);
	heap_head->end = HEAP_END;
	heap_head->used = UNUSED;
	heap_head->next = NULL;
	heap_head->prv = NULL;
	heap_crrunt = heap_head;
	heapnum=0;
	
	printf("HEAP_START=%08x\n",HEAP_START);
	printf("HEAP_END=%08x\n",HEAP_END);	
	
	
	printf("heap_head=0x%08x\n",heap_crrunt);
	printf("heap_head->start=%08x\n",heap_head->start);
	printf("heap_head->size=0x%08x\n",heap_head->size);
	
	

}

//分配內存函數

void * xmalloc(unsigned int size)
{

	heap *newblock;
	heap *prtblock;
	int stat=HEAP_NOTFIND;
	int num = 0;
	size = (size+7)&~7;
//	printf("xmalloc:%d\n",heapnum);

	heap_mark=heap_crrunt;
//	printf("heap_crrunt:0x%08x\n",heap_crrunt);
	while(heap_crrunt->next != heap_mark)
 	{
 		if(heap_crrunt == NULL) 
 			heap_crrunt = heap_head;
  	
  		if(heap_crrunt->used == UNUSED)
    	{
    		if(heap_crrunt->size > size)
       		{	
       			newblock = (heap*)((unsigned char *)heap_crrunt+(size+sizeof(heap)));
        		newblock->size = heap_crrunt->size-(size+sizeof(heap));
        		newblock->start = heap_crrunt->start+(size+sizeof(heap));
        		newblock->end = heap_crrunt->end;
        		newblock->used = UNUSED;
        		newblock->next = heap_crrunt->next;
        		newblock->prv = heap_crrunt;
        		heap_crrunt->used = USED;
        		heap_crrunt->size = size;
        		heap_crrunt->end = heap_crrunt->start+size;
        		heap_crrunt->next = newblock;
        		stat = HEAP_FOUND;
				heapnum++;
				
        		printf("heapnum:%d,heap:0x%08x,heapsize:%d\n",heapnum,heap_crrunt->start,size);
        		
				break;      
        	}
        
      	}
  		num++;
  		delay(1);
		if(num > 1000)
		{
			printf("alloc error\n");
			return NULL;
		}
  		heap_crrunt = heap_crrunt->next;
  
  	}
  	
  	if(stat == HEAP_NOTFIND)
  	{
  		printf("malloc fail\n");
  		return NULL;
  	}
  	
 	prtblock = heap_crrunt;
  	
 	heap_crrunt = newblock;
//	printf("newblock=0x%08x\n",newblock);
//	printf("newblock start=0x%08x\n",newblock->start);
	
 	return ((heap *)((u32)prtblock + sizeof(heap)));
 } 
  
//釋放
void xfree(void *block)

{	
	heap * ptrblock;
	heap * prvblock;
	heap * nextblock;
  
  	if(block==NULL) 
  	return ;
  	
  	ptrblock = (heap *)((unsigned char *)block-sizeof(heap));
  	ptrblock->used = UNUSED;
  	prvblock = ptrblock->prv;
  	nextblock = ptrblock->next;
  	printf("xfree\n");
  	if(prvblock != NULL)
   	{
   		if(prvblock->used==UNUSED)
      	{
      		prvblock->size = prvblock->size+ptrblock->size+sizeof(heap);
       		prvblock->end = ptrblock->end;
       		prvblock->next = ptrblock->next;
       		ptrblock = prvblock;
			heapnum--;
       	}
   }  
  	if(nextblock != NULL)
  	{
  		if(nextblock->used == UNUSED)
     	{
     		ptrblock->size = ptrblock->size+nextblock->size+sizeof(heap);
     		ptrblock->end = nextblock->end;
     		ptrblock->next = ptrblock->next;
			heapnum--;
     	}
  	}
   
   heap_crrunt = ptrblock;
}