rt-thread中动态内存分配之小内存管理模块方法的一点理解

@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

 /**
  * @ingroup SystemInit
  *
  * This function will initialize system heap memory.
  *
  * @param begin_addr the beginning address of system heap memory.
  * @param end_addr the end address of system heap memory.
  */
 void rt_system_heap_init(void *begin_addr, void *end_addr)
 {
     struct heap_mem *mem;
     rt_ubase_t begin_align = RT_ALIGN((rt_ubase_t)begin_addr, RT_ALIGN_SIZE);
     rt_ubase_t end_align   = RT_ALIGN_DOWN((rt_ubase_t)end_addr, RT_ALIGN_SIZE);
 
     RT_DEBUG_NOT_IN_INTERRUPT;
 
     /* alignment addr */
     if ((end_align > ( * SIZEOF_STRUCT_MEM)) &&
         ((end_align -  * SIZEOF_STRUCT_MEM) >= begin_align))
     {
         /* calculate the aligned memory size */
         mem_size_aligned = end_align - begin_align -  * SIZEOF_STRUCT_MEM;
     }
     else
     {
         rt_kprintf("mem init, error begin address 0x%x, and end address 0x%x\n",
                    (rt_ubase_t)begin_addr, (rt_ubase_t)end_addr);
 
         return;
     }
 
     /* point to begin address of heap */
     heap_ptr = (rt_uint8_t *)begin_align;
 
     RT_DEBUG_LOG(RT_DEBUG_MEM, ("mem init, heap begin address 0x%x, size %d\n",
                                 (rt_ubase_t)heap_ptr, mem_size_aligned));
 
     /* initialize the start of the heap */
     mem        = (struct heap_mem *)heap_ptr;
     mem->magic = HEAP_MAGIC;
     mem->next  = mem_size_aligned + SIZEOF_STRUCT_MEM;
     mem->prev  = ;
     mem->used  = ;
 #ifdef RT_USING_MEMTRACE
     rt_mem_setname(mem, "INIT");
 #endif
 
     /* initialize the end of the heap */
     heap_end        = (struct heap_mem *)&heap_ptr[mem->next];
     heap_end->magic = HEAP_MAGIC;
     heap_end->used  = ;
     heap_end->next  = mem_size_aligned + SIZEOF_STRUCT_MEM;
     heap_end->prev  = mem_size_aligned + SIZEOF_STRUCT_MEM;
 #ifdef RT_USING_MEMTRACE
     rt_mem_setname(heap_end, "INIT");
 #endif
 
     rt_sem_init(&heap_sem, "heap", , RT_IPC_FLAG_FIFO);
 
     /* initialize the lowest-free pointer to the start of the heap */
     lfree = (struct heap_mem *)heap_ptr;
 }