【rt-thread】动态内存分配之小内存管理模块方法的一点理解

 内存初始化后的布局示意

lfree指向内存空闲区首地址

 1 /**
 2  * @ingroup SystemInit
 3  *
 4  * This function will initialize system heap memory.
 5  *
 6  * @param begin_addr the beginning address of system heap memory.
 7  * @param end_addr the end address of system heap memory.
 8  */
 9 void rt_system_heap_init(void *begin_addr, void *end_addr)
10 {
11     struct heap_mem *mem;
12     rt_ubase_t begin_align = RT_ALIGN((rt_ubase_t)begin_addr, RT_ALIGN_SIZE);
13     rt_ubase_t end_align   = RT_ALIGN_DOWN((rt_ubase_t)end_addr, RT_ALIGN_SIZE);
14 
15     RT_DEBUG_NOT_IN_INTERRUPT;
16 
17     /* alignment addr */
18     if ((end_align > (2 * SIZEOF_STRUCT_MEM)) &&
19         ((end_align - 2 * SIZEOF_STRUCT_MEM) >= begin_align))
20     {
21         /* calculate the aligned memory size */
22         mem_size_aligned = end_align - begin_align - 2 * SIZEOF_STRUCT_MEM;        
23     }                                                                            
24     else
25     {
26         rt_kprintf("mem init, error begin address 0x%x, and end address 0x%x\n",
27                    (rt_ubase_t)begin_addr, (rt_ubase_t)end_addr);
28 
29         return;
30     }
31 
32     /* point to begin address of heap */
33     heap_ptr = (rt_uint8_t *)begin_align;
34 
35     RT_DEBUG_LOG(RT_DEBUG_MEM, ("mem init, heap begin address 0x%x, size %d\n",
36                                 (rt_ubase_t)heap_ptr, mem_size_aligned));
37 
38     /* initialize the start of the heap */
39     mem        = (struct heap_mem *)heap_ptr;
40     mem->magic = HEAP_MAGIC;
41     mem->next  = mem_size_aligned + SIZEOF_STRUCT_MEM;
42     mem->prev  = 0;
43     mem->used  = 0;
44 #ifdef RT_USING_MEMTRACE
45     rt_mem_setname(mem, "INIT");
46 #endif
47 
48     /* initialize the end of the heap */
49     heap_end        = (struct heap_mem *)&heap_ptr[mem->next];
50     heap_end->magic = HEAP_MAGIC;
51     heap_end->used  = 1;
52     heap_end->next  = mem_size_aligned + SIZEOF_STRUCT_MEM;
53     heap_end->prev  = mem_size_aligned + SIZEOF_STRUCT_MEM;
54 #ifdef RT_USING_MEMTRACE
55     rt_mem_setname(heap_end, "INIT");
56 #endif
57 
58     rt_sem_init(&heap_sem, "heap", 1, RT_IPC_FLAG_FIFO);
59 
60     /* initialize the lowest-free pointer to the start of the heap */
61     lfree = (struct heap_mem *)heap_ptr;
62 }

 

posted @ 2019-01-18 13:21  壹点灵异  阅读(1453)  评论(0)  编辑  收藏  举报