@2019-01-18
【小记】
rt-thread中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 ", 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 ", 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 }